Caloric Restriction

    From Longevity Wiki
    Food level, fecundity and longevity. Median life span and fecundity are negatively affected by a very low nutrient concentration in higher eukaryotes. However, life span but not fecundity is optimized by dietary restriction (DR).[1]

    Caloric restriction (CR), also known as calorie restriction or dietary restriction (DR), refers to a diet that reduces the intake of chemically bound energy from foods by 10 to 50 percent compared to ad libitum ("at will") nutrition. The goal is to achieve a higher life expectancy or at least delayed aging or health-promoting effects[2][3], without leading to malnutrition.

    In a number of model organisms, a health-promoting and life-extending effect has been demonstrated through this method. However, no extension of life expectancy has been observed in some species or breeds. The extension of life expectancy in some rodent strains by up to 50%[4] is dependent on the genome and sex among other factors[5].

    Effects in Model Organisms

    Positive Effects

    Kaplan–Meier Survival Curve on the effects of calorie restriction of laboratory mice (KR=Calorie Restriction, Überlebensrate=Cumulative survival, Alter=age, Monate=months).[6]

    Calorie restriction has been studied in model organisms such as Yeast (Saccharomyces Cerevisiae)[7][8], Nematodes (Caenorhabditis Elegans)[9], Fruit Flies (Drosophila Melanogaster)[10], Mice (Mus Musculus)[6], Rats (Rattus Norvegicus)[11], Domestic Dogs (Canis Familiaris)[12] and Non-Human Primates.[13][14][15]

    In many species, not only is the average lifespan of the test animals increased, but also their maximum lifespan. The frequency of age-related diseases correspondingly decreases.[16] The effect of an increase in maximum life expectancy occurs in rodents both when starting the diet in the early life phase (1st to 3rd month), and in the middle life phase (12th month).[13][14] However, if calorie restriction is started in a later life phase of the test animals, such as in the 17th or 24th month of mice, the effect reverses and the lifespan of the test animals is shortened.[17]

    Both in a study with rhesus monkeys[18] by the American National Institute on Aging, and in a study on Drosophila[10], it has been suggested that life extension depends not only on calorie restriction but also on the composition of the diet.

    General Criticism

    Various findings raise doubts about the notion that caloric restriction slows down the aging process, delays the age-related decline in physiological fitness, or extends the lifespan of organisms from different phylogenetic groups.[19] Positive effects of caloric restriction are not universal:

    In fruit flies, positive effects of caloric restriction are not reproduced with careful control of nutrient fractions.[20]

    The increase in lifespan caused by caloric restriction is not even reproducible among different strains of the same species.[19]

    Calorie restriction does not extend lifespan in all mice. In the top graph, a significant effect is observed in C57BL/6 mice ("laboratory mice"), while it is absent in DBA/2 mice ("wild type") below (AL=ad libitum, CR=Calorie Restriction).[17]

    Thus, calorie restriction does not lead to lifespan extension in all mouse strains.[17] In 19 to 27% of the mouse strains studied, a 40% caloric restriction even resulted in a shortened lifespan.[21][22]

    The frequently used C57BL/6 mice tend to become overweight with unrestricted food access (ad libitum). In these animals, the effect of caloric restriction is significant. DBA/2 mice, on the other hand, remain lean even with ad-libitum feeding. In mice from this strain, caloric restriction does not lead to lifespan extension. DBA/2 mice consume more oxygen with the same energy intake than C57BL/6 mice, meaning their metabolic rate is increased – they are poorer "feed converters."[23] It was already observed in earlier experiments that caloric restriction is most successful in mice that gain significant weight in early adulthood.[24] The results of these studies are interpreted to mean that lifespan is more influenced by the balance of energy intake and energy expenditure. Only in test animals prone to overweight or obesity can caloric restriction cause lifespan extension.[25]

    The NIA study on rhesus monkeys found no lifespan extension.[18] In a long-term study conducted at the Wisconsin National Primate Research Center over a period of 20 years on rhesus monkeys, a significantly better health status and a significantly increased lifespan were observed in the group of animals that received a reduced food supply during this period. In this group, 80% of the animals were still alive, compared to only 50% in the normally fed control group. Furthermore, in the animals with calorie restriction, a significantly delayed onset of age-associated diseases such as diabetes, cancer, and brain atrophy, as well as cardiovascular incidents, was observed. The authors of the study conclude that calorie restriction delays the aging process in this primate species.[26]

    Genetic Variations

    In animal models, some physiological and metabolic traits, especially lifespan, are strongly affected by genetic backgrounds and variations as well as non-genetic factors such as symbiotic microbiome and water balance[27]. The role of particular genes in the response of lifespan to caloric restriction has been investigated by determining if a genetic alteration alters this response. Lifespan rises to a maximum as the food intake is lowered, but can decline rapidly if the food supply is further reduced. Therefore, the effects of mutations should be examined over a broad range of food intakes, so that the degree of caloric restriction that maximizes life span can be determined and used in tests for genetic effects[28].

    When a collection of recombinant inbred mouse strains were tested for lifespan under ad libitum diet and caloric restriction (40% reduction compared to ad libitum diet) diet, a wide range of lifespan responses were observed in both ad libitum and caloric restriction diets[21][29]. For example, the mean lifespan of female mice on ad libitum diet varied from 407 to 1208 days. Strikingly, their lifespans on CR diet varied to a greater degree from 113 to 1225 days. Importantly, not only did CR fail in lifespan extension in some lines, but it even shortened lifespan in some lines too[21].

    Similarly, a strong variation in lifespan response to diets was observed when a collection of nearly 200 genetically distinct lines of Drosophila (DGRP: Drosophila Genetic Reference Panel) tested for lifespan in ad libitum (5% Yeast) and caloric restriction (0.5% Yeast)[30]. In both cases, lifespan response also significantly varied between males and females[21][30], generating a further layer of complication in understanding the mechanisms of caloric restriction. A simple interpretation of these animal studies would suggest that a certain type of caloric restriction may not be beneficial, but they can be even deleterious depending on genetic variations and sex[31]. Therefore, for human applications of caloric restriction, it is suggested that individualized genomics and medicine should be established first to take full advantage of caloric restriction.[32]

    Effects in Humans

    The hormonal and metabolic effects of calorie restriction observed in experimental animals, such as lower body temperature, reduced metabolic rate, and decreased oxidative stress, have also been demonstrated in humans.[16][33] Additionally, lower serum levels of basal insulin ("fasting insulin"), profibrotic proteins, various growth factors - such as PDGF and TGF-α - as well as cytokines like Tumor Necrosis Factor-α have been detected.[34][35][36][37][38] It is also established that long-term calorie restriction is an effective prevention against Type II Diabetes, high blood pressure, and Atherosclerosis, which together are the main causes of Morbidity, disabilities, and Mortality in humans.[39]

    Longevity

    Currently, there is no scientific evidence that permanent calorie restriction – with adequate nutrition – leads to an extension of life expectancy compared to a lean adult.[40] It is undisputed that severe overweight, i.e., obesity, leads to a reduction in average and maximum life expectancy. However, reviews have confirmed that calorie restriction (or Intermittent fasting) in healthy adults is likely to lead to similar life extension – extensions of health and lifespan – as observed in animal experiments. They describe the health effects and molecular mechanisms of such phases, including Autophagy. A problem with scientific studies on this is that the relatively long lifespan of humans makes it difficult to directly test such interventions.[41] Periods in which calorie intake is limited to a constant deficit can be combined with intermittent fasting (periods with intervals of consuming no food, only water, and tea/coffee, for example) and variants of the Mediterranean diet, which typically have long-term cardiovascular benefits and could also increase longevity.[42] Which protocols (such as duration and magnitude of the calorie deficit) and combinations (see, for example, Caloric restriction mimetic, effects of coffee, and AMPK) with calorie restriction are effective or most effective in humans in general and depending on the individual[43] is still unknown.

    Risks of Calorie Restriction in Humans

    Specifically in the USA, the results of animal experiments have led to many practitioners adopting calorie restriction, particularly in California. A group of these practitioners formed the Calorie Restriction Society. Excessive calorie reduction always carries the risk of malnutrition, which can negatively affect physical and mental health. There are repeated warnings about potential eating disorders with calorie restriction. On the other hand, a study showed that calorie restriction does not lead to an increase in anorexia or bulimia. The psychological effects of calorie restriction were evaluated as positive in this study.[44]

    Long-term undernutrition can, besides positive effects, also lead to various deficiency diseases. Developmental disorders can occur in minors. Cold sensitivity may increase.[45] Ovulation can be suspended in women with very low BMI, resulting in temporary infertility.[45] In the Minnesota Starvation Experiment, anemia, edema in the lower extremities, muscle wasting, weakness, neurological impairments, dizziness, irritability, lethargy, and depression were observed in adult males undergoing a six-month calorie restriction with a 90% carbohydrate diet.[46] Short-term calorie restriction can lead to muscle wasting and reduced bone density.[47] In individuals with low body fat, calorie restriction can be harmful.[48]

    Mechanism

    The reasons for the lifespan extension in model organisms through caloric restriction are not yet fully understood. The underlying mechanism of this effect remains unknown. It's possible that the extension of lifespan results from improved health status due to the absence of obesity and the delayed onset of age-related diseases of the metabolic syndrome such as cardiovascular diseases and Type II Diabetes mellitus.

    Studies conducted with mice suggest that the lifespan extension associated with caloric restriction is not simply a result of leanness caused by calorie restriction. The maximum lifespan of male rats that maintained a low body fat mass through physical activity did not increase, but it did for mice that maintained a low body weight through caloric restriction alone, despite a sedentary lifestyle.[48]

    Caloric restriction in rats produces soluble factors in the blood serum that cause lifespan extension in human cell cultures.[49] Various mechanisms are being discussed:

    Reduction of Oxidative Stress

    There are indications that oxidative stress is reduced by decreased food intake, thereby delaying primary aging. Primary aging is the process in cells and organs that defines the maximum lifespan in the absence of diseases (inevitable aging). Secondary aging is determined by external factors such as diseases, environmental factors, lifestyle, and physical activity (avoidable aging).[50] Oxidative stress primarily occurs in the mitochondria, the powerhouses of the cells.[51][52] In some mouse strains, the effect of calorie restriction can be partially induced by Resveratrol.[53] In yeasts, the protein Rim15, a glucose-inhibited protein kinase, acts as a sensor of nutrient concentrations as well as the initiator of Meiosis and is necessary for lifespan extension in yeasts.[54] However, a meta-analysis also reported that caloric restriction – contrary to previous results – does not lead to lifespan extension in yeasts, but the results in yeasts are partly based on methodological artifacts.[55]

    Hormesis

    According to a contrary hypothesis, oxidative stress from reactive oxygen species (ROS) is thought to positively stimulate cell metabolism (Hormesis), which may explain the health benefits of caloric restriction as well as Fasting, oxidative plant compounds in cabbage vegetables, and physical training.[56]

    In contrast to the free radical theory, it is assumed that an increased formation of reactive oxygen species in the mitochondria, associated with caloric restriction, causes an adaptive response that enhances stress resistance.[57]

    Activation of Sirtuin-1 and Reduced Expression of the mTOR Receptor

    Signal-regulating enzymes such as Sirtuin-1 (Sirt1) in mammals, or Sirtuin Sir2 in yeasts, may play a role.[58] The cells of calorically restricted test animals produce Sirt1 in larger quantities.[59] An increased production of Sirt1, in turn, reduces the expression of the mTOR receptor (mammalian Target of Rapamycin),[60] which is also associated with the aging process. The lifespan of mice can be significantly extended by administering Rapamycin, which docks to the mTOR receptor.[61][62] Melatonin is also being studied due to its activation of Sirtuin.[53]

    "Reprogramming" of Metabolism and Gene Expression

    According to another theory, long-term reduced food intake "reprograms" the metabolism.[63] In mice under caloric restriction, a changed gene expression has been observed. On one hand, genes involved in energy metabolism are overexpressed,[64] while on the other hand, over 50 pro-inflammatory genes are downregulated.[65][66] It's possible that the regeneration of some stem cells is enhanced.[67] In some strains of mice, a similar effect can be induced by Metformin.[5]

    Increased Formation of Ketone Bodies

    Both caloric restriction and the ketogenic diet have therapeutic potential in various animal models of neurological diseases.[68] Under caloric restriction, there is a transition from glucose metabolism to the use of ketone bodies. Ketone bodies can be used as an alternative energy source for brain cells when glucose availability is poor.[69]

    Ketone bodies protect neurons against various types of neuronal injuries. This is one explanation for the beneficial effect of caloric restriction in the animal model of neurological diseases.[69]

    Increased Autophagy

    Autophagy, also known as “cellular self-digestion”, is a cellular pathway involved in the breakdown of proteins and organelles, and plays a role in various diseases. Dysfunctions in autophagy are associated with neurodegenerative diseases, microbial infections, and aging.

    Several indications suggest that autophagy is important for the effects of calorie restriction: The efficiency of autophagy decreases with age; the decline in autophagy is associated with changes in aging biomarkers; the age-dependent change in autophagy is prevented experimentally by calorie restriction; preventing a decrease in autophagy efficiency mimics the effects of calorie restriction; prolonged inhibition of autophagy accelerates the aging process; conversely, prolonged stimulation of autophagy delays the aging process in rats; stimulating autophagy can protect older cells from accumulation of altered mitochondrial DNA; stimulating autophagy alleviates age-related hypercholesterolemia in rodents.[70]

    A comparable effect was observed in plants whose lighting was reduced.[71]

    Reduced Thyroid Hormones

    Plasma levels of thyroid hormones Triiodothyronine (T3), Thyroxine (T4), and Thyroid-stimulating Hormone (TSH) were measured in Rhesus monkeys (Macaca mulatta) subjected to a 30% CR (caloric restriction) diet. The plasma T3 level decreased compared to the control group. Given the impact of the thyroid axis on metabolism, this could be a mechanism through which a CR diet mediates its health benefits.[72]

    Calorie Restriction Mimetics

    Even if human studies prove a positive effect of calorie restriction on human life expectancy, the necessary reduction in food energy intake over the corresponding duration and degree is not practical or desired for the majority of people. Therefore, so-called Calorie Restriction Mimetics (CR mimetics) are also being researched. The goal of this strategy is to discover compounds that mimic the effects of calorie restriction in the human body, for example by acting on the same metabolic pathways, without the need for actual restriction of food energy intake.[73]

    However, further studies are required to determine whether calorie restriction mimetics actually have an impact on human life expectancy.[48]

    Potential Calorie Restriction Mimetics

    According to Ingram, various substances are considered as mimetics of calorie restriction in the human body:[74]

    • 2-Deoxy-D-glucose can initiate ketogenesis[75], makes rats gain slightly less body weight than control animals and leads to a significant reduction in body temperature and fasting serum insulin levels, thereby simulating certain effects of calorie restriction.[76]
    • Metformin, an orally administered antidiabetic, reduces cancer incidence in rats and slows the progression of the disease. It also reduces the occurrence of cardiovascular diseases and extends lifespan.[77]
    • Glipizide, like Metformin, is an orally administered antidiabetic that helps control blood sugar levels. It works by partially blocking the potassium channels of the beta cells of the Islets of Langerhans.[78]
    • Rosiglitazone prevents fatty acid-induced insulin resistance by reducing the glucose infusion rate and improves insulin-mediated suppression of hepatic glucose production. It also improves the systemic elimination of non-esterified fatty acids.[79]
    • Pioglitazone, like Rosiglitazone, belongs to the class of substances known as Thiazolidinediones/Glitazones.
    • Soy Isoflavones appear to have cardioprotective effects similar to those of calorie restriction, such as reducing LDL cholesterol, inhibiting pro-inflammatory cytokines, stimulating nitric oxide production, potentially reducing LDL particles, inhibiting platelet aggregation, and improving vascular reactivity.[80]
    • Resveratrol increases the survival rate of obese mice compared to a control group of lean, untreated animals. Adding Resveratrol to the diet of lean mice, however, does not further increase lifespan.[81]
    • Rimonabant belongs to the endocannabinoids, cannabis-like substances that can regulate appetite and energy balance. Rimonabant is a cannabinoid-1 receptor blocker. By overstimulating the endocannabinoid receptor in the hypothalamus, it stimulates fatty acid synthesis (lipogenesis), presumably by increasing adiponectin levels. This lipogenesis reduces intra-abdominal fat. Rimonabant also improves the lipid profile and glucose tolerance.[Citation needed]
    • Adiponectin, a hormone secreted by fat cells, reduces insulin resistance in obese mice by reducing triglyceride content in muscles and liver.[82]
    • Sirolimus/Rapamycin, when administered to mice with food, inhibits the mTOR pathway and resulted in a significantly increased lifespan compared to control mice.[83]
    • Acipimox inhibits the release of fatty acids from adipose tissue and reduces the blood concentration of LDL particles, along with a reduction in triglyceride and cholesterol levels.[Citation needed]

    See Also

    Further Reading

    • 2010, Extending healthy life span--from yeast to humans [1]
    • 2020, Mechanisms of Lifespan Regulation by Calorie Restriction and Intermittent Fasting in Model Organisms [32]

    Todo

    References

    1. ↑ 1.0 1.1 Fontana L et al.: Extending healthy life span--from yeast to humans. Science 2010. (PMID 20395504) [PubMed] [DOI] [Full text] When the food intake of organisms such as yeast and rodents is reduced (dietary restriction), they live longer than organisms fed a normal diet. A similar effect is seen when the activity of nutrient-sensing pathways is reduced by mutations or chemical inhibitors. In rodents, both dietary restriction and decreased nutrient-sensing pathway activity can lower the incidence of age-related loss of function and disease, including tumors and neurodegeneration. Dietary restriction also increases life span and protects against diabetes, cancer, and cardiovascular disease in rhesus monkeys, and in humans it causes changes that protect against these age-related pathologies. Tumors and diabetes are also uncommon in humans with mutations in the growth hormone receptor, and natural genetic variants in nutrient-sensing pathways are associated with increased human life span. Dietary restriction and reduced activity of nutrient-sensing pathways may thus slow aging by similar mechanisms, which have been conserved during evolution. We discuss these findings and their potential application to prevention of age-related disease and promotion of healthy aging in humans, and the challenge of possible negative side effects.
    2. ↑ Pijl H: Longevity. The allostatic load of dietary restriction. Physiol Behav 2012. (PMID 21663754) [PubMed] [DOI] Restriction of food intake by 10-50% of ad libitum on a per unit of weight or energy content basis can extend the lifespan of a wide variety of species and prevent or delay age-related disease. This review first briefly summarizes the data delineating mortality trajectories of various species' populations maintained on restricted diets to provide insight into the effects of nutrient deprivation on distinct components of the aging process. Next, I discuss a number of important studies that have addressed the question whether it is the lack of calories and/or specific nutrients that determines the longevity response to dietary restriction. Finally, I review the evidence for hormesis as a proximate mechanism underpinning the impact of dietary restriction on lifespan. In aggregate, the currently available demographic data suggest that dietary restriction can both slow the age-related progressive accumulation of cellular damage and also enhance the ability of organisms to cope with irreversible injury. Restriction of essential nutrients as well as calories may affect life expectancy, perhaps in a species specific fashion. Hormesis, i.e. an evolutionary conserved stress response routine providing protection against a wide variety of (other) hazards in response to low levels of stress, is very likely to contribute to the beneficial health effects of dietary restriction.
    3. ↑ Dorshkind K et al.: The ageing immune system: is it ever too old to become young again?. Nat Rev Immunol 2009. (PMID 19104499) [PubMed] [DOI] Ageing is accompanied by a decline in the function of the immune system, which increases susceptibility to infections and can decrease the quality of life. The ability to rejuvenate the ageing immune system would therefore be beneficial for elderly individuals and would decrease health-care costs for society. But is the immune system ever too old to become young again? We review here the promise of various approaches to rejuvenate the function of the immune system in the rapidly growing ageing population.
    4. ↑ Speakman JR & Mitchell SE: Caloric restriction. Mol Aspects Med 2011. (PMID 21840335) [PubMed] [DOI] Restricting the intake of calories has been practiced as a method for increasing both the length and quality of life for over 500 years. Experimental work confirming the success of this approach in animals has accumulated over the last 100 years. Lifelong caloric restriction (CR) may extend life by up to 50% in rodents, with progressively less impact the later in life it is started. This effect is matched by profound impacts on age related diseases including reduced risk of cancer, neurodegenerative disorders, autoimmune disease, cardiovascular disease and type II diabetes mellitus. The disposable soma theory of ageing suggests that CR evolved as a somatic protection response to enable animals to survive periods of food shortage. The shutdown of reproductive function during CR is consistent with this suggestion, but other features of the phenomenon are less consistent with this theory, and some have suggested that in rodents it may be mostly an artifact of domestication. CR induces profound effects on animals at all levels from the transcriptome to whole animal physiology and behavior. Animals under CR lose weight which is disproportionately contributed to by white adipose tissue. Generally animals on CR change their activity patterns so that they are more active prior to food delivery each day but total activity may be unchanged or reduced. Considerable debate has occurred over the effects of CR on resting metabolic rate (RMR). Total RMR declines, but as body mass and body composition also change it is unclear whether metabolism at the tissue level also declines, is unchanged or even increases. Body temperature universally decreases. Hunger is increased and does not seem to abate even with very long term restriction. Circulating adipokines are reduced reflecting the reduction in white adipose tissue (WAT) mass under restriction and there is a large reduction in circulating insulin and glucose levels. There are profound tissue level changes in metabolism with a generalized shift from carbohydrate to fat metabolism. Four pathways have been implicated in mediating the CR effect. These are the insulin like growth factor (IGF-1)/insulin signaling pathway, the sirtuin pathway, the adenosine monophosphate (AMP) activated protein kinase (AMPK) pathway and the target of rapamycin (TOR) pathway. These different pathways may interact and may all play important roles mediating different aspects of the response. Exactly how they generate the health benefits remains open for debate, however CR results in reduced oxidative stress and enhanced autophagy, both of which could be essential components of the beneficial effects. Most data about the effects of CR in mammals comes from work on rodents. There is limited work on non-human primates that shows promising effects and one randomized controlled trial in humans where physiological markers of the CR response are consistent with the responses in mice and rats. There are also populations of humans voluntarily restricting themselves. Humans on long term restriction report similar negative side effects to those observed in animals - perpetual hunger, reduced body temperature leading to a feeling of being cold, and diminished libido. Considerable effort has been directed in recent years to find drugs that mimic the CR response. Promising candidates are those that intersect with the critical signaling pathways identified above and include biguanides such as metformin that target the insulin signaling pathway, stilbenes (e.g. resveratrol) that affect sirtuin activity and drugs such as rapamycin that interact with mTOR signaling. Whether it will ever be possible to find drugs that capture the health benefits of CR without the negative side-effects remains unclear. Moreover, even if such drugs are developed how the current licensing system for drug use in western societies would cope with them may be a further obstacle to their use.
    5. ↑ 5.0 5.1 Mulvey L et al.: Lifespan modulation in mice and the confounding effects of genetic background. J Genet Genomics 2014. (PMID 25269675) [PubMed] [DOI] [Full text] We are currently in the midst of a revolution in ageing research, with several dietary, genetic and pharmacological interventions now known to modulate ageing in model organisms. Excitingly, these interventions also appear to have beneficial effects on late-life health. For example, dietary restriction (DR) has been shown to slow the incidence of age-associated cardiovascular disease, metabolic disease, cancer and brain ageing in non-human primates and has been shown to improve a range of health indices in humans. While the idea that DR's ability to extend lifespan is often thought of as being universal, studies in a range of organisms, including yeast, mice and monkeys, suggest that this may not actually be the case. The precise reasons underlying these differential effects of DR on lifespan are currently unclear, but genetic background may be an important factor in how an individual responds to DR. Similarly, recent findings also suggest that the responsiveness of mice to specific genetic or pharmacological interventions that modulate ageing may again be influenced by genetic background. Consequently, while there is a clear driver to develop interventions to improve late-life health and vitality, understanding precisely how these act in response to particular genotypes is critical if we are to translate these findings to humans. We will consider of the role of genetic background in the efficacy of various lifespan interventions and discuss potential routes of utilising genetic heterogeneity to further understand how particular interventions modulate lifespan and healthspan.
    6. ↑ 6.0 6.1 Weindruch R et al.: The retardation of aging in mice by dietary restriction: longevity, cancer, immunity and lifetime energy intake. J Nutr 1986. (PMID 3958810) [PubMed] [DOI] We sought to clarify the impact of dietary restriction (undernutrition without malnutrition) on aging. Female mice from a long-lived strain were fed after weaning in one of six ways: group 1) a nonpurified diet ad libitum; 2) 85 kcal/wk of a purified diet (approximately 25% restriction); 3) 50 kcal/wk of a restricted purified diet enriched in protein, vitamin and mineral content to provide nearly equal intakes of these essentials as in group 2 (approximately 55% restriction); 4) as per group 3, but also restricted before weaning; 5) 50 kcal/wk of a vitamin- and mineral-enriched diet but with protein intake gradually reduced over the life span; 6) 40 kcal/wk of the diet fed to groups 3 and 4 (approximately 65% restriction). Mice from groups 3-6 exhibited mean and maximal life spans 35-65% greater than for group 1 and 20-40% greater than for group 2. Mice from group 6 lived longest of all. The longest lived 10% of mice from group 6 averaged 53.0 mo which, to our knowledge, exceeds reported values for any mice of any strain. Beneficial influences on tumor patterns and on declines with age in T-lymphocyte proliferation were most striking in group 6. Significant positive correlations between adult body weight and longevity occurred in groups 3-5 suggesting that increased metabolic efficiency may be related to longevity in restricted mice. Mice from groups 3-6 ate approximately 30% more calories per gram of mouse over the life span than did mice from group 2. These findings show the profound anti-aging effects of dietary restriction and provide new information for optimizing restriction regimes.
    7. ↑ Lin SJ et al.: Requirement of NAD and SIR2 for life-span extension by calorie restriction in Saccharomyces cerevisiae. Science 2000. (PMID 11000115) [PubMed] [DOI] Calorie restriction extends life-span in a wide variety of organisms. Although it has been suggested that calorie restriction may work by reducing the levels of reactive oxygen species produced during respiration, the mechanism by which this regimen slows aging is uncertain. Here, we mimicked calorie restriction in yeast by physiological or genetic means and showed a substantial extension in life-span. This extension was not observed in strains mutant for SIR2 (which encodes the silencing protein Sir2p) or NPT1 (a gene in a pathway in the synthesis of NAD, the oxidized form of nicotinamide adenine dinucleotide). These findings suggest that the increased longevity induced by calorie restriction requires the activation of Sir2p by NAD.
    8. ↑ Lin SJ et al.: Calorie restriction extends Saccharomyces cerevisiae lifespan by increasing respiration. Nature 2002. (PMID 12124627) [PubMed] [DOI] Calorie restriction (CR) extends lifespan in a wide spectrum of organisms and is the only regimen known to lengthen the lifespan of mammals. We established a model of CR in budding yeast Saccharomyces cerevisiae. In this system, lifespan can be extended by limiting glucose or by reducing the activity of the glucose-sensing cyclic-AMP-dependent kinase (PKA). Lifespan extension in a mutant with reduced PKA activity requires Sir2 and NAD (nicotinamide adenine dinucleotide). In this study we explore how CR activates Sir2 to extend lifespan. Here we show that the shunting of carbon metabolism toward the mitochondrial tricarboxylic acid cycle and the concomitant increase in respiration play a central part in this process. We discuss how this metabolic strategy may apply to CR in animals.
    9. ↑ Lakowski B & Hekimi S: The genetics of caloric restriction in Caenorhabditis elegans. Proc Natl Acad Sci U S A 1998. (PMID 9789046) [PubMed] [DOI] [Full text] Low caloric intake (caloric restriction) can lengthen the life span of a wide range of animals and possibly even of humans. To understand better how caloric restriction lengthens life span, we used genetic methods and criteria to investigate its mechanism of action in the nematode Caenorhabditis elegans. Mutations in many genes (eat genes) result in partial starvation of the worm by disrupting the function of the pharynx, the feeding organ. We found that most eat mutations significantly lengthen life span (by up to 50%). In C. elegans, mutations in a number of other genes that can extend life span have been found. Two genetically distinct mechanisms of life span extension are known: a mechanism involving genes that regulate dauer formation (age-1, daf-2, daf-16, and daf-28) and a mechanism involving genes that affect the rate of development and behavior (clk-1, clk-2, clk-3, and gro-1). We find that the long life of eat-2 mutants does not require the activity of DAF-16 and that eat-2; daf-2 double mutants live even longer than extremely long-lived daf-2 mutants. These findings demonstrate that food restriction lengthens life span by a mechanism distinct from that of dauer-formation mutants. In contrast, we find that food restriction does not further increase the life span of long-lived clk-1 mutants, suggesting that clk-1 and caloric restriction affect similar processes.
    10. ↑ 10.0 10.1 Mair W et al.: Calories do not explain extension of life span by dietary restriction in Drosophila. PLoS Biol 2005. (PMID 16000018) [PubMed] [DOI] [Full text] Dietary restriction (DR) extends life span in diverse organisms, including mammals, and common mechanisms may be at work. DR is often known as calorie restriction, because it has been suggested that reduction of calories, rather than of particular nutrients in the diet, mediates extension of life span in rodents. We here demonstrate that extension of life span by DR in Drosophila is not attributable to the reduction in calorie intake. Reduction of either dietary yeast or sugar can reduce mortality and extend life span, but by an amount that is unrelated to the calorie content of the food, and with yeast having a much greater effect per calorie than does sugar. Calorie intake is therefore not the key factor in the reduction of mortality rate by DR in this species.
    11. ↑ C. M. McCay und M. F. Crowell: Prolonging the Life Span. In: The Scientific Monthly 39, 1934, S. 405–414; JSTOR 15813.
    12. ↑ Lawler DF et al.: Diet restriction and ageing in the dog: major observations over two decades. Br J Nutr 2008. (PMID 18062831) [PubMed] [DOI] This report reviews decade two of the lifetime diet restriction study of the dog. Labrador retrievers (n 48) were paired at age 6 weeks by sex and weight within each of seven litters, and assigned randomly within the pair to control-feeding (CF) or 25 % diet restriction (DR). Feeding began at age 8 weeks. The same diet was fed to all dogs; only the quantity differed. Major lifetime observations included 1.8 years longer median lifespan among diet-restricted dogs, with delayed onset of late life diseases, especially osteoarthritis. Long-term DR did not negatively affect skeletal maturation, structure or metabolism. Among all dogs, high static fat mass and declining lean body mass predicted death, most strongly at 1 year prior. Fat mass above 25 % was associated with increasing insulin resistance, which independently predicted lifespan and chronic diseases. Metabolizable energy requirement/lean body mass most accurately explained energy metabolism due to diet restriction; diet-restricted dogs required 17 % less energy to maintain each lean kilogram. Metabonomics-based urine metabolite trajectories reflected DR-related differences, suggesting that signals from gut microbiota may be involved in the DR longevity and health responses. Independent of feeding group, increased hazard of earlier death was associated with lower lymphoproliferative responses to phytohaemagglutinin, concanavalin A, and pokeweed mitogen; lower total lymphocytes, T-cells, CD4 and CD8 cells; lower CD8 percentages and higher B-cell percentages. When diet group was taken into account, PWM responses and cell counts and percentages remained predictive of earlier death.
    13. ↑ 13.0 13.1 Lane MA et al.: Caloric restriction and aging in primates: Relevance to humans and possible CR mimetics. Microsc Res Tech 2002. (PMID 12424798) [PubMed] [DOI] For nearly 70 years it has been recognized that reduction in caloric intake by 30-40% from ad libitum levels leads to a significant extension of mean and maximal lifespan in a variety of short-lived species. This effect of caloric restriction (CR) on lifespan has been reported in nearly all species tested and has been reproduced hundreds of times under a variety of different laboratory conditions. In addition to prolonging lifespan, CR also prevents or delays the onset of age-related disease and maintains many physiological functions at more youthful levels. Studies in longer-lived species, specifically rhesus and squirrel monkeys, have been underway since the late 1980s. The studies in nonhuman primates are beginning to yield valuable information suggesting that the effect of CR on aging is universal across species and that this nutritional paradigm will have similar effects in humans. Even if CR can be shown to impact upon human aging, it is unlikely that most people will be able to maintain the strict dietary control required for this regimen. Thus, elucidation of the biological mechanisms of CR and development of alternative strategies to yield similar benefits is of primary importance. CR mimetics, or interventions that "mimic" certain protective effects of CR, may represent one such alternative strategy.
    14. ↑ 14.0 14.1 Wanagat J et al.: Caloric intake and aging: mechanisms in rodents and a study in nonhuman primates. Toxicol Sci 1999. (PMID 10630588) [PubMed] [DOI] Caloric restriction (CR) increases maximum life span in rodents while attenuating the development of age-associated pathological and biological changes. Although nearly all of the rodent studies have initiated CR early in life (1-3 months of age), CR, when started at 12 months of age, also extends maximum life span in mice. Two main questions face investigators of CR. One concerns the mechanisms by which CR retards aging and diseases in rodents. There is evidence that CR may act, at least in part, by reducing oxidative stress. A CR-induced decrease in oxidative stress appears to be most profound in post-mitotic tissues and may derive from lower mitochondrial production of free radicals. The second issue is whether CR will exert similar effects in primates. Studies on CR in rhesus monkeys (maximum life span approximately 40 years) support the notion of human translatability. We describe the University of Wisconsin Study of rhesus monkeys subjected to a 30% reduction of caloric intake starting at either 1989 or 1994 when they were approximately 10 years old. The data from our study and from other trials suggest that CR can be safely carried out in monkeys and that certain physiological effects of CR that occur in rodents (e.g., decreased blood glucose and insulin levels, improved insulin sensitivity, and lowering of body temperature) also occur in monkeys. Whether oxidative stress in monkeys is reduced by CR will be known by the year 2000, while effects on longevity and diseases should be clearly seen by, appropriately, 2020.
    15. ↑ Weindruch R: The retardation of aging by caloric restriction: studies in rodents and primates. Toxicol Pathol 1996. (PMID 8994305) [PubMed] [DOI] Caloric restriction (CR), which has been investigated by gerontologists for more than 60 yr, provides the only intervention tested to date in mammals (typically mice and rats) that repeatedly and strongly increases maximum life span while retarding the appearance of age-associated pathologic and biologic changes. Although the large majority of rodent studies have initiated CR early in life (1-3 mo of age), CR started in midadulthood (at 12 mo) also extends maximum life span in mice. Two main questions now face gerontologists investigating CR. By what mechanisms does CR retard aging and disease processes in rodents? There is evidence to suggest that age-associated increases in oxidative damage may represent a primary aging process that is attenuated by CR. Will CR exert similar actions in primates? Studies in rhesus monkeys subjected to CR and limited human epidemiological data support the notion of human translatability. However, no matter what the answers are to these questions, the prolongation of the health span and life span of rodents by CR has major implications for many disciplines, including toxicologic pathology, and raises important questions about the desirability of ad libitum feeding.
    16. ↑ 16.0 16.1 Hofer T et al.: Long-term effects of caloric restriction or exercise on DNA and RNA oxidation levels in white blood cells and urine in humans. Rejuvenation Res 2008. (PMID 18729811) [PubMed] [DOI] [Full text] Excessive adiposity is associated with increased oxidative stress and accelerated aging. Weight loss induced by negative energy balance reduces markers of oxidation in experimental animals and humans. The long-term effects of weight loss induced by calorie restriction or increased energy expenditure induced by exercise on measures of oxidative stress and damage have not been studied in humans. The objective of the present study was to compare the effects of 20% caloric restriction or 20% exercise alone over 1 year on oxidative damage to DNA and RNA, as assessed through white blood cell and urine analyses. Eighteen men and women aged 50 to 60 years with a body mass index (BMI) between 23.5 to 29.9 kg/m(2) were assigned to one of two conditions--20% CR (n = 9) or 20% EX (n = 9)--which was designed to produce an identical energy deficit through increased energy expenditure. Compared to baseline, both interventions significantly reduced oxidative damage to both DNA (48.5% and 49.6% reduction for the CR and EX groups, respectively) and RNA (35.7% and 52.1% reduction for the CR and EX groups, respectively) measured in white blood cells. However, urinary levels of DNA and RNA oxidation products did not differ from baseline values following either 12-month intervention program. Data from the present study provide evidence that negative energy balances induced through either CR or EX result in substantial and similar improvements in markers of DNA and RNA damage to white blood cells, potentially by reducing systemic oxidative stress.
    17. ↑ 17.0 17.1 17.2 Forster MJ et al.: Genotype and age influence the effect of caloric intake on mortality in mice. FASEB J 2003. (PMID 12586746) [PubMed] [DOI] [Full text] Long-term caloric restriction (CR) has been repeatedly shown to increase life span and delay the onset of age-associated pathologies in laboratory mice and rats. The purpose of the current study was to determine whether the CR-associated increase in life span occurs in all strains of mice or only in some genotypes and whether the effects of CR and ad libitum (AL) feeding on mortality accrue gradually or are rapidly inducible and reversible. In one experiment, groups of male C57BL/6, DBA/2, and B6D2F1 mice were fed AL or CR (60% of AL) diets beginning at 4 months of age until death. In the companion study, separate groups of mice were maintained chronically on AL or CR regimens until 7, 17, or 22-24 months of age, after which, half of each AL and CR group was switched to the opposite regimen for 11 wk. This procedure yielded four experimental groups for each genotype, namely AL-->AL, AL-->CR, CR-->CR, and CR-->AL, designated according to long-term and short-term caloric regimen, respectively. Long-term CR resulted in increased median and maximum life span in C57BL/6 and B6D2F1 mice but failed to affect either parameter in the DBA/2 mice. The shift from AL-->CR increased mortality in 17- and 24-month-old mice, whereas the shift from CR-->AL did not significantly affect mortality of any age group. Such increased risk of mortality following implementation of CR at older ages was evident in all three strains but was most dramatic in DBA/2 mice. Results of this study indicate that CR does not have beneficial effects in all strains of mice, and it increases rather than decreases mortality if initiated in advanced age.
    18. ↑ 18.0 18.1 Mattison JA et al.: Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study. Nature 2012. (PMID 22932268) [PubMed] [DOI] [Full text] Calorie restriction (CR), a reduction of 10–40% in intake of a nutritious diet, is often reported as the most robust non-genetic mechanism to extend lifespan and healthspan. CR is frequently used as a tool to understand mechanisms behind ageing and age-associated diseases. In addition to and independently of increasing lifespan, CR has been reported to delay or prevent the occurrence of many chronic diseases in a variety of animals. Beneficial effects of CR on outcomes such as immune function, motor coordination and resistance to sarcopenia in rhesus monkeys have recently been reported. We report here that a CR regimen implemented in young and older age rhesus monkeys at the National Institute on Aging (NIA) has not improved survival outcomes. Our findings contrast with an ongoing study at the Wisconsin National Primate Research Center (WNPRC), which reported improved survival associated with 30% CR initiated in adult rhesus monkeys (7–14 years) and a preliminary report with a small number of CR monkeys. Over the years, both NIA and WNPRC have extensively documented beneficial health effects of CR in these two apparently parallel studies. The implications of the WNPRC findings were important as they extended CR findings beyond the laboratory rodent and to a long-lived primate. Our study suggests a separation between health effects, morbidity and mortality, and similar to what has been shown in rodents, study design, husbandry and diet composition may strongly affect the life-prolonging effect of CR in a long-lived nonhuman primate.
    19. ↑ 19.0 19.1 Sohal RS & Forster MJ: Caloric restriction and the aging process: a critique. Free Radic Biol Med 2014. (PMID 24941891) [PubMed] [DOI] [Full text] The main objective of this review is to provide an appraisal of the current status of the relationship between energy intake and the life span of animals. The concept that a reduction in food intake, or caloric restriction (CR), retards the aging process, delays the age-associated decline in physiological fitness, and extends the life span of organisms of diverse phylogenetic groups is one of the leading paradigms in gerontology. However, emerging evidence disputes some of the primary tenets of this conception. One disparity is that the CR-related increase in longevity is not universal and may not even be shared among different strains of the same species. A further misgiving is that the control animals, fed ad libitum (AL), become overweight and prone to early onset of diseases and death, and thus may not be the ideal control animals for studies concerned with comparisons of longevity. Reexamination of body weight and longevity data from a study involving over 60,000 mice and rats, conducted by a National Institute on Aging-sponsored project, suggests that CR-related increase in life span of specific genotypes is directly related to the gain in body weight under the AL feeding regimen. Additionally, CR in mammals and "dietary restriction" in organisms such as Drosophila are dissimilar phenomena, albeit they are often presented to be the very same. The latter involves a reduction in yeast rather than caloric intake, which is inconsistent with the notion of a common, conserved mechanism of CR action in different species. Although specific mechanisms by which CR affects longevity are not well understood, existing evidence supports the view that CR increases the life span of those particular genotypes that develop energy imbalance owing to AL feeding. In such groups, CR lowers body temperature, rate of metabolism, and oxidant production and retards the age-related pro-oxidizing shift in the redox state.
    20. ↑ Lee KP et al.: Lifespan and reproduction in Drosophila: New insights from nutritional geometry. Proc Natl Acad Sci U S A 2008. (PMID 18268352) [PubMed] [DOI] [Full text] Modest dietary restriction (DR) prolongs life in a wide range of organisms, spanning single-celled yeast to mammals. Here, we report the use of recent techniques in nutrition research to quantify the detailed relationship between diet, nutrient intake, lifespan, and reproduction in Drosophila melanogaster. Caloric restriction (CR) was not responsible for extending lifespan in our experimental flies. Response surfaces for lifespan and fecundity were maximized at different protein-carbohydrate intakes, with longevity highest at a protein-to-carbohydrate ratio of 1:16 and egg-laying rate maximized at 1:2. Lifetime egg production, the measure closest to fitness, was maximized at an intermediate P:C ratio of 1:4. Flies offered a choice of complementary foods regulated intake to maximize lifetime egg production. The results indicate a role for both direct costs of reproduction and other deleterious consequences of ingesting high levels of protein. We unite a body of apparently conflicting work within a common framework and provide a platform for studying aging in all organisms.
    21. ↑ 21.0 21.1 21.2 21.3 Liao CY et al.: Genetic variation in the murine lifespan response to dietary restriction: from life extension to life shortening. Aging Cell 2010. (PMID 19878144) [PubMed] [DOI] [Full text] Chronic dietary restriction (DR) is considered among the most robust life-extending interventions, but several reports indicate that DR does not always extend and may even shorten lifespan in some genotypes. An unbiased genetic screen of the lifespan response to DR has been lacking. Here, we measured the effect of one commonly used level of DR (40% reduction in food intake) on mean lifespan of virgin males and females in 41 recombinant inbred strains of mice. Mean strain-specific lifespan varied two to threefold under ad libitum (AL) feeding and 6- to 10-fold under DR, in males and females respectively. Notably, DR shortened lifespan in more strains than those in which it lengthened life. Food intake and female fertility varied markedly among strains under AL feeding, but neither predicted DR survival: therefore, strains in which DR shortened lifespan did not have low food intake or poor reproductive potential. Finally, strain-specific lifespans under DR and AL feeding were not correlated, indicating that the genetic determinants of lifespan under these two conditions differ. These results demonstrate that the lifespan response to a single level of DR exhibits wide variation amenable to genetic analysis. They also show that DR can shorten lifespan in inbred mice. Although strains with shortened lifespan under 40% DR may not respond negatively under less stringent DR, the results raise the possibility that life extension by DR may not be universal.
    22. ↑ Rikke BA et al.: Genetic dissection of dietary restriction in mice supports the metabolic efficiency model of life extension. Exp Gerontol 2010. (PMID 20452416) [PubMed] [DOI] [Full text] Dietary restriction (DR) has been used for decades to retard aging in rodents, but its mechanism of action remains an enigma. A principal roadblock has been that DR affects many different processes, making it difficult to distinguish cause and effect. To address this problem, we applied a quantitative genetics approach utilizing the ILSXISS series of mouse recombinant inbred strains. Across 42 strains, mean female lifespan ranged from 380 to 1070days on DR (fed 60% of ad libitum [AL]) and from 490 to 1020days on an AL diet. Longevity under DR and AL is under genetic control, showing 34% and 36% heritability, respectively. There was no correlation between lifespans on DR and AL; thus different genes modulate longevity under the two regimens. DR lifespans are significantly correlated with female fertility after return to an AL diet after various periods of DR (R=0.44, P=0.006). We assessed fuel efficiency (FE, ability to maintain growth and body weight independent of absolute food intake) using a multivariate approach and found it to be correlated with longevity and female fertility, suggesting possible causality. We found several quantitative trait loci responsible for these traits, mapping to chromosomes 7, 9, and 15. We present a metabolic model in which the anti-aging effects of DR are consistent with the ability to efficiently utilize dietary resources.
    23. ↑ Sohal RS et al.: Life span extension in mice by food restriction depends on an energy imbalance. J Nutr 2009. (PMID 19141702) [PubMed] [DOI] [Full text] In this study, our main objective was to determine whether energy restriction (ER) affects the rate of oxygen consumption of mice transiently or lastingly and whether metabolic rate plays a role in the ER-related extension of life span. We compared rates of resting oxygen consumption between C57BL/6 mice, whose life span is prolonged by ER, and the DBA/2 mice where it is not, at 6 and 23 mo of age, following 40% ER for 2 and 19 mo, respectively. Mice of the 2 strains that consumed food ad libitum (AL) had a similar body mass at the age of 4 mo and consumed similar amounts of food throughout the experiment; however, the body weight subsequently significantly increased (20%) in the C57BL/6 mice but did not increase significantly in the DBA/2 mice. The resting rate of oxygen consumption was normalized as per g body weight, lean body mass, organ weight, and per mouse. The resting rate of oxygen consumption at 6 mo was significantly higher in AL DBA/2 mice than the AL C57BL/6 mice for all of the criteria except organ weight. A similar difference in AL mice of the 2 strains was present at 23 mo when resting oxygen consumption was normalized to body weight. Resting oxygen consumption was lowered by ER in both age groups of each strain according to all 4 criteria used for normalization, except body weight in the C57BL/6 mice. The effect of ER on resting oxygen consumption was thus neither transient nor age or strain dependent. Our results suggest that ER-induced extension of life span occurs in the mouse genotype in which there is a positive imbalance between energy intake and energy expenditure.
    24. ↑ Ross MH et al.: Dietary practices and growth responses as predictors of longevity. Nature 1976. (PMID 958413) [PubMed] [DOI]
    25. ↑ Life Extension: Myth of Caloric Restriction Refuted, https://www.aerzteblatt.de/nachrichten/35192/Lebensverlaengerung-Mythos-der-Kalorienrestriktion-widerlegt
    26. ↑ Colman RJ et al.: Caloric restriction delays disease onset and mortality in rhesus monkeys. Science 2009. (PMID 19590001) [PubMed] [DOI] [Full text] Caloric restriction (CR), without malnutrition, delays aging and extends life span in diverse species; however, its effect on resistance to illness and mortality in primates has not been clearly established. We report findings of a 20-year longitudinal adult-onset CR study in rhesus monkeys aimed at filling this critical gap in aging research. In a population of rhesus macaques maintained at the Wisconsin National Primate Research Center, moderate CR lowered the incidence of aging-related deaths. At the time point reported, 50% of control fed animals survived as compared with 80% of the CR animals. Furthermore, CR delayed the onset of age-associated pathologies. Specifically, CR reduced the incidence of diabetes, cancer, cardiovascular disease, and brain atrophy. These data demonstrate that CR slows aging in a primate species.
    27. ↑ Lucanic M et al.: Impact of genetic background and experimental reproducibility on identifying chemical compounds with robust longevity effects. Nat Commun 2017. (PMID 28220799) [PubMed] [DOI] [Full text] Limiting the debilitating consequences of ageing is a major medical challenge of our time. Robust pharmacological interventions that promote healthy ageing across diverse genetic backgrounds may engage conserved longevity pathways. Here we report results from the Caenorhabditis Intervention Testing Program in assessing longevity variation across 22 Caenorhabditis strains spanning 3 species, using multiple replicates collected across three independent laboratories. Reproducibility between test sites is high, whereas individual trial reproducibility is relatively low. Of ten pro-longevity chemicals tested, six significantly extend lifespan in at least one strain. Three reported dietary restriction mimetics are mainly effective across C. elegans strains, indicating species and strain-specific responses. In contrast, the amyloid dye ThioflavinT is both potent and robust across the strains. Our results highlight promising pharmacological leads and demonstrate the importance of assessing lifespans of discrete cohorts across repeat studies to capture biological variation in the search for reproducible ageing interventions.
    28. ↑ Piper MD & Partridge L: Dietary restriction in Drosophila: delayed aging or experimental artefact?. PLoS Genet 2007. (PMID 17465680) [PubMed] [DOI] [Full text] Lifespan can be extended by reduction of dietary intake. This practice is referred to as dietary restriction (DR), and extension of lifespan by DR is evolutionarily conserved in taxonomically diverse organisms including yeast, invertebrates, and mammals. Although these two often-stated facts carry the implication that the mechanisms of DR are also evolutionarily conserved, extension of lifespan could be a case of evolutionary convergence, with different underlying mechanisms in different taxa. Furthermore, extension of lifespan by different methods of DR in the same organism may operate through different mechanisms. These topics remain unresolved because of the very fact that the mechanisms of DR are unknown. Given these uncertainties, it is essential that work on the mechanisms of DR is not clouded by imprecise descriptions of methods or by technical problems. Here we review the recent literature on DR in Drosophila to point out some methodological issues that can obscure mechanistic interpretations. We also indicate some experiments that could be performed to determine if DR in Drosophila operates through similar mechanisms to the process in rodents.
    29. ↑ Liao CY et al.: Genetic variation in responses to dietary restriction--an unbiased tool for hypothesis testing. Exp Gerontol 2013. (PMID 23562825) [PubMed] [DOI] [Full text] Dietary restriction (DR) extends lifespan in a wide range of animal models. A major obstacle to understanding how DR modulates lifespan and aging-related dysfunction is the multiplicity of physiological and molecular changes associated with DR. Unraveling their importance to the longevity effect of DR remains a major challenge. In this perspective, we review the marked genetic variation in the response to DR of multiple recombinant inbred (RI) mouse strains. We illustrate how this genetic variation can be exploited to probe the mechanisms mediating lifespan extension by DR, as well as uncover its limits as an intervention. RI strains exhibit marked variation in their lifespan as well as physiological responses to DR. Quantitative genetic and statistical tools can use this phenotypic variation to probe the importance of physiological and molecular changes that have been hypothesized to play roles in DR-mediated lifespan extension.
    30. ↑ 30.0 30.1 Wilson, Kenneth Anthony and Beck, Jennifer and Nelson, Christopher S. and Hilsabeck, Tyler A. and Promislow, Daniel and Brem, Rachel B. and Kapahi, Pankaj, Genome-Wide Analyses for Lifespan and Healthspan in D. Melanogaster Reveal Decima as a Regulator of Insulin-Like Peptide Production (July 16, 2019) [DOI]
    31. ↑ Di Francesco A et al.: A time to fast. Science 2018. (PMID 30442801) [PubMed] [DOI] [Full text] Nutrient composition and caloric intake have traditionally been used to devise optimized diets for various phases of life. Adjustment of meal size and frequency have emerged as powerful tools to ameliorate and postpone the onset of disease and delay aging, whereas periods of fasting, with or without reduced energy intake, can have profound health benefits. The underlying physiological processes involve periodic shifts of metabolic fuel sources, promotion of repair mechanisms, and the optimization of energy utilization for cellular and organismal health. Future research endeavors should be directed to the integration of a balanced nutritious diet with controlled meal size and patterns and periods of fasting to develop better strategies to prevent, postpone, and treat the socioeconomical burden of chronic diseases associated with aging.
    32. ↑ 32.0 32.1 Hwangbo DS et al.: Mechanisms of Lifespan Regulation by Calorie Restriction and Intermittent Fasting in Model Organisms. Nutrients 2020. (PMID 32344591) [PubMed] [DOI] [Full text] Genetic and pharmacological interventions have successfully extended healthspan and lifespan in animals, but their genetic interventions are not appropriate options for human applications and pharmacological intervention needs more solid clinical evidence. Consequently, dietary manipulations are the only practical and probable strategies to promote health and longevity in humans. Caloric restriction (CR), reduction of calorie intake to a level that does not compromise overall health, has been considered as being one of the most promising dietary interventions to extend lifespan in humans. Although it is straightforward, continuous reduction of calorie or food intake is not easy to practice in real lives of humans. Recently, fasting-related interventions such as intermittent fasting (IF) and time-restricted feeding (TRF) have emerged as alternatives of CR. Here, we review the history of CR and fasting-related strategies in animal models, discuss the molecular mechanisms underlying these interventions, and propose future directions that can fill the missing gaps in the current understanding of these dietary interventions. CR and fasting appear to extend lifespan by both partially overlapping common mechanisms such as the target of rapamycin (TOR) pathway and circadian clock, and distinct independent mechanisms that remain to be discovered. We propose that a systems approach combining global transcriptomic, metabolomic, and proteomic analyses followed by genetic perturbation studies targeting multiple candidate pathways will allow us to better understand how CR and fasting interact with each other to promote longevity.
    33. ↑ Heilbronn LK et al.: Effect of 6-month calorie restriction on biomarkers of longevity, metabolic adaptation, and oxidative stress in overweight individuals: a randomized controlled trial. JAMA 2006. (PMID 16595757) [PubMed] [DOI] [Full text] CONTEXT: Prolonged calorie restriction increases life span in rodents. Whether prolonged calorie restriction affects biomarkers of longevity or markers of oxidative stress, or reduces metabolic rate beyond that expected from reduced metabolic mass, has not been investigated in humans. OBJECTIVE: To examine the effects of 6 months of calorie restriction, with or without exercise, in overweight, nonobese (body mass index, 25 to <30) men and women. DESIGN, SETTING, AND PARTICIPANTS: Randomized controlled trial of healthy, sedentary men and women (N = 48) conducted between March 2002 and August 2004 at a research center in Baton Rouge, La. INTERVENTION: Participants were randomized to 1 of 4 groups for 6 months: control (weight maintenance diet); calorie restriction (25% calorie restriction of baseline energy requirements); calorie restriction with exercise (12.5% calorie restriction plus 12.5% increase in energy expenditure by structured exercise); very low-calorie diet (890 kcal/d until 15% weight reduction, followed by a weight maintenance diet). MAIN OUTCOME MEASURES: Body composition; dehydroepiandrosterone sulfate (DHEAS), glucose, and insulin levels; protein carbonyls; DNA damage; 24-hour energy expenditure; and core body temperature. RESULTS: Mean (SEM) weight change at 6 months in the 4 groups was as follows: controls, -1.0% (1.1%); calorie restriction, -10.4% (0.9%); calorie restriction with exercise, -10.0% (0.8%); and very low-calorie diet, -13.9% (0.7%). At 6 months, fasting insulin levels were significantly reduced from baseline in the intervention groups (all P<.01), whereas DHEAS and glucose levels were unchanged. Core body temperature was reduced in the calorie restriction and calorie restriction with exercise groups (both P<.05). After adjustment for changes in body composition, sedentary 24-hour energy expenditure was unchanged in controls, but decreased in the calorie restriction (-135 kcal/d [42 kcal/d]), calorie restriction with exercise (-117 kcal/d [52 kcal/d]), and very low-calorie diet (-125 kcal/d [35 kcal/d]) groups (all P<.008). These "metabolic adaptations" (~ 6% more than expected based on loss of metabolic mass) were statistically different from controls (P<.05). Protein carbonyl concentrations were not changed from baseline to month 6 in any group, whereas DNA damage was also reduced from baseline in all intervention groups (P <.005). CONCLUSIONS: Our findings suggest that 2 biomarkers of longevity (fasting insulin level and body temperature) are decreased by prolonged calorie restriction in humans and support the theory that metabolic rate is reduced beyond the level expected from reduced metabolic body mass. Studies of longer duration are required to determine if calorie restriction attenuates the aging process in humans. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00099151.
    34. ↑ Fontana L et al.: Long-term calorie restriction is highly effective in reducing the risk for atherosclerosis in humans. Proc Natl Acad Sci U S A 2004. (PMID 15096581) [PubMed] [DOI] [Full text] Little is known regarding the long-term effects of caloric restriction (CR) on the risk for atherosclerosis. We evaluated the effect of CR on risk factors for atherosclerosis in individuals who are restricting food intake to slow aging. We studied 18 individuals who had been on CR for an average of 6 years and 18 age-matched healthy individuals on typical American diets. We measured serum lipids and lipoproteins, fasting plasma glucose and insulin, blood pressure (BP), high-sensitivity C-reactive protein (CRP), platelet-derived growth factor AB (PDGF-AB), body composition, and carotid artery intima-media thickness (IMT). The CR group were leaner than the comparison group (body mass index, 19.6 +/- 1.9 vs. 25.9 +/- 3.2 kg/m(2); percent body fat, 8.7 +/- 7% vs. 24 +/- 8%). Serum total cholesterol (Tchol), low-density lipoprotein cholesterol, ratio of Tchol to high-density lipoprotein cholesterol (HDL-C), triglycerides, fasting glucose, fasting insulin, CRP, PDFG-AB, and systolic and diastolic BP were all markedly lower, whereas HDL-C was higher, in the CR than in the American diet group. Medical records indicated that the CR group had serum lipid-lipoprotein and BP levels in the usual range for individuals on typical American diets, and similar to those of the comparison group, before they began CR. Carotid artery IMT was approximately 40% less in the CR group than in the comparison group. Based on a range of risk factors, it appears that long-term CR has a powerful protective effect against atherosclerosis. This interpretation is supported by the finding of a low carotid artery IMT.
    35. ↑ Fontana L et al.: Calorie restriction or exercise: effects on coronary heart disease risk factors. A randomized, controlled trial. Am J Physiol Endocrinol Metab 2007. (PMID 17389710) [PubMed] [DOI] Coronary heart disease (CHD) risk factors and the risk of CHD increase with increased adiposity. Fat loss induced by negative energy balance improves all metabolic CHD risk factors. To determine whether fat loss induced by long-term calorie restriction (CR) or increased energy expenditure induced by exercise (EX) has different effects on CHD risk factors in nonobese subjects, we conducted a 1-yr controlled trial involving 48 nonobese subjects who were randomly assigned to one of three groups: CR, 20% CR diet (n = 18); EX, 20% increase in energy expenditure through daily exercise with no increase in energy intake (n = 18); or HL, healthy lifestyle guidelines (n = 10). Subjects were 29 women and 17 men aged 57 +/- 3 yr, with BMI 27.3 +/- 2.0 kg/m(2). Assessments included total body fat by DEXA, lipoproteins, blood pressure, HOMA-IR, C-reactive protein (CRP), and estimated 10-yr CHD risk score. Body fat decreased by 6.3 +/- 3.8 kg in CR, 5.6 +/- 4.4 kg in EX, and 0.4 +/- 1.7 kg in HL, which corresponded to reductions of 24.9, 22.3, and 1.2% of baseline body fat mass, respectively. These CR- and EX-induced energy deficits were accompanied by reductions in most of the major CHD risk factors, including plasma LDL-cholesterol, total cholesterol/HDL ratio, HOMA-IR index, and CRP concentrations that were similar in the two intervention groups. Data from the present study provide evidence that CR- and EX-induced negative energy balance result in substantial and similar improvements in the major risk factors for CHD in normal-weight and overweight middle-aged adults.
    36. ↑ Weiss EP et al.: Improvements in glucose tolerance and insulin action induced by increasing energy expenditure or decreasing energy intake: a randomized controlled trial. Am J Clin Nutr 2006. (PMID 17093155) [PubMed] [DOI] [Full text] BACKGROUND: Weight loss, through calorie restriction or increases in energy expenditure via exercise, improves glucose tolerance and insulin action. However, exercise-induced energy expenditure may further improve glucoregulation through mechanisms independent of weight loss. OBJECTIVE: The objective was to assess the hypothesis that weight loss through exercise-induced energy expenditure improves glucoregulation and circulating factors involved in insulin action to a greater extent than does similar weight loss through calorie restriction. DESIGN: Sedentary men and women aged 50-60 y with a body mass index (kg/m(2)) of 23.5-29.9 were randomly assigned to 1 of 2 weight-loss interventions [12 mo of exercise training (EX group; n = 18) or calorie restriction (CR group; n = 18)] or to a healthy lifestyle (HL) control group (n = 10). The insulin sensitivity index and areas under the curve for glucose and insulin were assessed with an oral-glucose-tolerance test. Adiponectin and tumor necrosis factor alpha concentrations were measured in fasting serum. Fat mass was measured by dual-energy X-ray absorptiometry. RESULTS: Yearlong energy deficits were not significantly different between the EX and CR groups, as evidenced by body weight and fat mass changes. The insulin sensitivity index increased and the glucose and insulin areas under the curve decreased in the EX and CR groups, remained unchanged in the HL group, and did not differ significantly between the EX and CR groups. Marginally significant increases in adiponectin and decreases in the ratio of tumor necrosis factor alpha to adiponectin occurred in the EX and CR groups but not in the HL group. CONCLUSIONS: Weight loss induced by exercise training or calorie restriction improves glucose tolerance and insulin action in nonobese, healthy, middle-aged men and women. However, it does not appear that exercise training-induced weight loss results in greater improvements than those that result from calorie restriction alone.
    37. ↑ Larson-Meyer DE et al.: Effect of calorie restriction with or without exercise on insulin sensitivity, beta-cell function, fat cell size, and ectopic lipid in overweight subjects. Diabetes Care 2006. (PMID 16732018) [PubMed] [DOI] [Full text] OBJECTIVE: The purpose of this article was to determine the relationships among total body fat, visceral adipose tissue (VAT), fat cell size (FCS), ectopic fat deposition in liver (intrahepatic lipid [IHL]) and muscle (intramyocellular lipid [IMCL]), and insulin sensitivity index (S(i)) in healthy overweight, glucose-tolerant subjects and the effects of calorie restriction by diet alone or in conjunction with exercise on these variables. RESEARCH DESIGN AND METHODS: Forty-eight overweight volunteers were randomly assigned to four groups: control (100% of energy requirements), 25% calorie restriction (CR), 12.5% calorie restriction +12.5% energy expenditure through structured exercise (CREX), or 15% weight loss by a low-calorie diet followed by weight maintenance for 6 months (LCD). Weight, percent body fat, VAT, IMCL, IHL, FCS, and S(i) were assessed at baseline and month 6. RESULTS: At baseline, FCS was related to VAT and IHL (P < 0.05) but not to IMCL. FCS was also the strongest determinant of S(i) (P < 0.01). Weight loss at month 6 was 1 +/- 1% (control, mean +/- SE), 10 +/- 1% (CR), 10 +/- 1% (CREX), and 14 +/- 1% (LCD). VAT, FCS, percent body fat, and IHL were reduced in the three intervention groups (P < 0.01), but IMCL was unchanged. S(i) was increased at month 6 (P = 0.05) in the CREX (37 +/- 18%) and LCD (70 +/- 34%) groups (P < 0.05) and tended to increase in the CR group (40 +/- 20%, P = 0.08). Together the improvements in S(i) were related to loss in weight, fat mass, and VAT, but not IHL, IMCL, or FCS. CONCLUSIONS: Large adipocytes lead to lipid deposition in visceral and hepatic tissues, promoting insulin resistance. Calorie restriction by diet alone or with exercise reverses this trend.
    38. ↑ Meyer TE et al.: Long-term caloric restriction ameliorates the decline in diastolic function in humans. J Am Coll Cardiol 2006. (PMID 16412867) [PubMed] [DOI] OBJECTIVES: We determined whether caloric restriction (CR) has cardiac-specific effects that attenuate the established aging-associated impairments in diastolic function (DF). BACKGROUND: Caloric restriction retards the aging process in small mammals; however, no information is available on the effects of long-term CR on human aging. In healthy individuals, Doppler echocardiography has established the pattern of aging-associated DF impairment, whereas little change is observed in systolic function (SF). METHODS: Diastolic function was assessed in 25 subjects (age 53 +/- 12 years) practicing CR for 6.5 +/- 4.6 years and 25 age- and gender-matched control subjects consuming Western diets. Diastolic function was quantified by transmitral flow, Doppler tissue imaging, and model-based image processing (MBIP) of E waves. C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta1 (TGF-beta1) were also measured. RESULTS: No difference in SF was observed between groups; however, standard transmitral Doppler flow DF indexes of the CR group were similar to those of younger individuals, and MBIP-based, flow-derived DF indexes, reflecting chamber viscoelasticity and stiffness, were significantly lower than in control subjects. Blood pressure, serum CRP, TNF-alpha, and TGF-beta(1) levels were significantly lower in the CR group (102 +/- 10/61 +/- 7 mm Hg, 0.3 +/- 0.3 mg/l, 0.8 +/- 0.5 pg/ml, 29.4 +/- 6.9 ng/ml, respectively) compared with the Western diet group (131 +/- 11/83 +/- 6 mm Hg, 1.9 +/- 2.8 mg/l, 1.5 +/- 1.0 pg/ml, 35.4 +/- 7.1 ng/ml, respectively). CONCLUSIONS: Caloric restriction has cardiac-specific effects that ameliorate aging-associated changes in DF. These beneficial effects on cardiac function might be mediated by the effect of CR on blood pressure, systemic inflammation, and myocardial fibrosis.
    39. ↑ Fontana L: The scientific basis of caloric restriction leading to longer life. Curr Opin Gastroenterol 2009. (PMID 19262201) [PubMed] [DOI] PURPOSE OF THE REVIEW: The present review discusses the current state of knowledge regarding the effects of calorie restriction in modulating metabolism and aging. RECENT FINDINGS: There are currently no interventions or gene manipulations that can prevent, stop or reverse the aging process. However, there are a number of interventions that can slow down aging and prolong maximal lifespan up to 60% in experimental animals. Long-term calorie restriction without malnutrition and reduced function mutations in the insulin/IGF-1 signaling pathway are the most robust interventions known to increase maximal lifespan and healthspan in rodents. Although it is currently not known if long-term calorie restriction with adequate nutrition extends maximal lifespan in humans, we do know that long-term calorie restriction without malnutrition results in some of the same metabolic and hormonal adaptations related to longevity in calorie restriction rodents. Moreover, calorie restriction with adequate nutrition protects against obesity, type 2 diabetes, hypertension and atherosclerosis, which are leading causes of morbidity, disability and mortality. SUMMARY: More studies are needed to elucidate the molecular mechanisms underlying the beneficial effects of calorie restriction in humans and to characterize new markers of aging/longevity that can assist clinicians in predicting mortality and morbidity of the general population.
    40. ↑ In Search of the Fountain of Youth: The Example of Calorie Restriction, https://www.heise.de/tp/features/Auf-der-Suche-nach-dem-Jungbrunnen-das-Beispiel-Kalorienreduktion-3395506.html
    41. ↑ Green CL et al.: Molecular mechanisms of dietary restriction promoting health and longevity. Nat Rev Mol Cell Biol 2022. (PMID 34518687) [PubMed] [DOI] [Full text] Dietary restriction with adequate nutrition is the gold standard for delaying ageing and extending healthspan and lifespan in diverse species, including rodents and non-human primates. In this Review, we discuss the effects of dietary restriction in these mammalian model organisms and discuss accumulating data that suggest that dietary restriction results in many of the same physiological, metabolic and molecular changes responsible for the prevention of multiple ageing-associated diseases in humans. We further discuss how different forms of fasting, protein restriction and specific reductions in the levels of essential amino acids such as methionine and the branched-chain amino acids selectively impact the activity of AKT, FOXO, mTOR, nicotinamide adenine dinucleotide (NAD+), AMP-activated protein kinase (AMPK) and fibroblast growth factor 21 (FGF21), which are key components of some of the most important nutrient-sensing geroprotective signalling pathways that promote healthy longevity.
    42. ↑ O'Keefe JH et al.: A Pesco-Mediterranean Diet With Intermittent Fasting: JACC Review Topic of the Week. J Am Coll Cardiol 2020. (PMID 32943166) [PubMed] [DOI] As opportunistic omnivores, humans are evolutionarily adapted to obtain calories and nutrients from both plant and animal food sources. Today, many people overconsume animal products, often-processed meats high in saturated fats and chemical additives. Alternatively, strict veganism can cause nutritional deficiencies and predispose to osteopenia, sarcopenia, and anemia. A logical compromise is a plant-rich diet with fish/seafood as principal sources of animal food. This paper reviews cumulative evidence regarding diet and health, incorporating data from landmark clinical trials of the Mediterranean diet and recommendations from recent authoritative guidelines, to support the hypothesis that a Pesco-Mediterranean diet is ideal for optimizing cardiovascular health. The foundation of this diet is vegetables, fruits, nuts, seeds, legumes, whole grains, and extra-virgin olive oil with fish/seafood and fermented dairy products. Beverages of choice are water, coffee, and tea. Time-restricted eating is recommended, whereby intermittent fasting is done for 12 to 16 h each day.
    43. ↑ Wilson KA et al.: Evaluating the beneficial effects of dietary restrictions: A framework for precision nutrigeroscience. Cell Metab 2021. (PMID 34555343) [PubMed] [DOI] [Full text] Dietary restriction (DR) has long been viewed as the most robust nongenetic means to extend lifespan and healthspan. Many aging-associated mechanisms are nutrient responsive, but despite the ubiquitous functions of these pathways, the benefits of DR often vary among individuals and even among tissues within an individual, challenging the aging research field. Furthermore, it is often assumed that lifespan interventions like DR will also extend healthspan, which is thus often ignored in aging studies. In this review, we provide an overview of DR as an intervention and discuss the mechanisms by which it affects lifespan and various healthspan measures. We also review studies that demonstrate exceptions to the standing paradigm of DR being beneficial, thus raising new questions that future studies must address. We detail critical factors for the proposed field of precision nutrigeroscience, which would utilize individualized treatments and predict outcomes using biomarkers based on genotype, sex, tissue, and age.
    44. ↑ Williamson DA et al.: Is caloric restriction associated with development of eating-disorder symptoms? Results from the CALERIE trial. Health Psychol 2008. (PMID 18248104) [PubMed] [DOI] OBJECTIVE: This study tested a secondary hypothesis of the CALERIE trial (Heilbronn et al., 2006) that a 12-month period of intentional dietary restriction would be associated with an increase in eating disorder symptoms. DESIGN: To test this hypothesis, 48 overweight adults were randomly assigned to four treatment arms in a 12-month study: (1) 25% calorie restriction, (2) 12.5% calorie restriction and 12.5% increased energy expenditure by structured exercise, (3) low-calorie diet, and (4) healthy diet (no-calorie restriction). MAIN OUTCOME MEASURES: Primary outcome measures for the study were changes in: eating disorder symptoms, mood, dietary restraint, body weight, and energy balance. RESULTS: All three dietary restriction arms were associated with increased dietary restraint and negative energy balance, but not with increased ED symptoms or other harmful psychological effects. Participants in the three calorie restriction arms lost significant amounts of body weight. The psychological and behavioral effects were maintained during a 6-month follow-up period. CONCLUSION: These results did not support the hypothesis that caloric restriction causes increased eating disorder symptoms in overweight adults. In general, caloric restriction had either benign or beneficial psychological and behavioral effects.
    45. ↑ 45.0 45.1 Marzetti E et al.: Cellular mechanisms of cardioprotection by calorie restriction: state of the science and future perspectives. Clin Geriatr Med 2009. (PMID 19944269) [PubMed] [DOI] [Full text] Evidence from animal models and preliminary studies in humans indicates that calorie restriction (CR) delays cardiac aging and can prevent cardiovascular disease. These effects are mediated by a wide spectrum of biochemical and cellular adaptations, including redox homeostasis, mitochondrial function, inflammation, apoptosis, and autophagy. Despite the beneficial effects of CR, its large-scale implementation is challenged by applicability issues as well as health concerns. However, preclinical studies indicate that specific compounds, such as resveratrol, may mimic many of the effects of CR, thus potentially obviating the need for drastic food intake reductions. Results from ongoing clinical trials will reveal whether the intriguing alternative of CR mimetics represents a safe and effective strategy to promote cardiovascular health and delay cardiac aging in humans.
    46. ↑ Keys et al.; "The Biology of Human Starvation" , pp. 1133
    47. ↑ Morley JE et al.: Antiaging, longevity and calorie restriction. Curr Opin Clin Nutr Metab Care 2010. (PMID 19851100) [PubMed] [DOI] PURPOSE OF REVIEW: The role of calorie restriction in humans is controversial. Recently, new data in monkeys and humans have provided new insights into the potential role of calorie restriction in longevity. RECENT FINDINGS: A study in rhesus monkeys showed a reduction in aging-associated mortality. A number of controlled studies have suggested a variety of beneficial effects during studies of 6-12 months in humans. Major negative effects in humans were loss of muscle mass, muscle strength and loss of bone. SUMMARY: Dietary restriction in rodents has not been shown to be effective when started in older rodents. Weight loss in humans over 60 years of age is associated with increased mortality, hip fracture and increased institutionalization. Calorie restriction in older persons should be considered experimental and potentially dangerous. Exercise at present appears to be a preferable treatment for older persons.
    48. ↑ 48.0 48.1 48.2 Fontana L & Klein S: Aging, adiposity, and calorie restriction. JAMA 2007. (PMID 17341713) [PubMed] [DOI] CONTEXT: Excessive calorie intake and subsequent obesity increases the risk of developing chronic disease and decreases life expectancy. In rodent models, calorie restriction with adequate nutrient intake decreases the risk of developing chronic disease and extends maximum life span. OBJECTIVE: To evaluate the physiological and clinical implications of calorie restriction with adequate nutrient intake. EVIDENCE ACQUISITION: Search of PubMed (1966-December 2006) using terms encompassing various aspects of calorie restriction, dietary restriction, aging, longevity, life span, adiposity, and obesity; hand search of journals that focus on obesity, geriatrics, or aging; and search of reference lists of pertinent research and review articles and books. Reviewed reports (both basic science and clinical) included epidemiologic studies, case-control studies, and randomized controlled trials, with quality of data assessed by taking into account publication in a peer-reviewed journal, number of animals or individuals studied, objectivity of measurements, and techniques used to minimize bias. EVIDENCE SYNTHESIS: It is not known whether calorie restriction extends maximum life span or life expectancy in lean humans. However, calorie restriction in adult men and women causes many of the same metabolic adaptations that occur in calorie-restricted rodents and monkeys, including decreased metabolic, hormonal, and inflammatory risk factors for diabetes, cardiovascular disease, and possibly cancer. Excessive calorie restriction causes malnutrition and has adverse clinical effects. CONCLUSIONS: Calorie restriction in adult men and women causes beneficial metabolic, hormonal, and functional changes, but the precise amount of calorie intake or body fat mass associated with optimal health and maximum longevity in humans is not known. In addition, it is possible that even moderate calorie restriction may be harmful in specific patient populations, such as lean persons who have minimal amounts of body fat.
    49. ↑ de Cabo R et al.: Serum from calorie-restricted animals delays senescence and extends the lifespan of normal human fibroblasts in vitro. Aging (Albany NY) 2015. (PMID 25855056) [PubMed] [DOI] [Full text] The cumulative effects of cellular senescence and cell loss over time in various tissues and organs are considered major contributing factors to the ageing process. In various organisms, caloric restriction (CR) slows ageing and increases lifespan, at least in part, by activating nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases of the sirtuin family. Here, we use an in vitro model of CR to study the effects of this dietary regime on replicative senescence, cellular lifespan and modulation of the SIRT1 signaling pathway in normal human diploid fibroblasts. We found that serum from calorie-restricted animals was able to delay senescence and significantly increase replicative lifespan in these cells, when compared to serum from ad libitum fed animals. These effects correlated with CR-mediated increases in SIRT1 and decreases in p53 expression levels. In addition, we show that manipulation of SIRT1 levels by either over-expression or siRNA-mediated knockdown resulted in delayed and accelerated cellular senescence, respectively. Our results demonstrate that CR can delay senescence and increase replicative lifespan of normal human diploid fibroblasts in vitro and suggest that SIRT1 plays an important role in these processes.
    50. ↑ M. Tostlebe: Disproportionalität der Aktivitäten der mitochondrialen Atmungskettenkomplexe im Myokard und in der Skelettmuskulatur im Alter. Dissertation, Martin-Luther-Universität Halle-Wittenberg, 2005.
    51. ↑ Csiszar A et al.: Anti-oxidative and anti-inflammatory vasoprotective effects of caloric restriction in aging: role of circulating factors and SIRT1. Mech Ageing Dev 2009. (PMID 19549533) [PubMed] [DOI] [Full text] Endothelial dysfunction, oxidative stress and inflammation are associated with vascular aging and promote the development of cardiovascular disease. Caloric restriction (CR) mitigates conditions associated with aging, but its effects on vascular dysfunction during aging remain poorly defined. To determine whether CR exerts vasoprotective effects in aging, aortas of ad libitum (AL) fed young and aged and CR-aged F344 rats were compared. Aging in AL-rats was associated with impaired acetylcholine-induced relaxation, vascular oxidative stress and increased NF-kappaB activity. Lifelong CR significantly improved endothelial function, attenuated vascular ROS production, inhibited NF-kappaB activity and down-regulated inflammatory genes. To elucidate the role of circulating factors in mediation of the vasoprotective effects of CR, we determined whether sera obtained from CR animals can confer anti-oxidant and anti-inflammatory effects in cultured coronary arterial endothelial cells (CAECs), mimicking the effects of CR. In CAECs cultured in the presence of AL serum TNFalpha elicited oxidative stress, NF-kappaB activation and inflammatory gene expression. By contrast, treatment of CAECs with CR serum attenuated TNFalpha-induced ROS generation and prevented NF-kappaB activation and induction of inflammatory genes. siRNA knockdown of SIRT1 mitigated the anti-oxidant and anti-inflammatory effects of CR serum. CR exerts anti-oxidant and anti-inflammatory vascular effects, which are likely mediated by circulating factors, in part, via a SIRT1-dependent pathway.
    52. ↑ Skrha J: Effect of caloric restriction on oxidative markers. Adv Clin Chem 2009. (PMID 19634782) [PubMed] Caloric restriction is associated with a decreased level of oxidative stress. Reactive oxygen species (ROS) generated predominantly in mitochondria are attenuated by decreased caloric intake. On the other hand, antioxidative mechanisms are frequently accelerated by increased gene expression or activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, paraoxonase, etc.). Measurement of different oxidative stress markers in relationship to caloric restriction is therefore important in experimental as well as clinical studies. Estimation of ROS in tissues and fluids is typically performed by measurement of oxidant products (i.e., malondialdehyde, F-2-isoprostanes, nitrotyrosine) and markers of antioxidant system (enzymes, glutathione, alpha-tocopherol, ascorbic acid, ubichinone, etc.). Because both components are critical to objectively understand the oxidative stress state, tangible biochemical data is required in order to comprehensively elucidate pathobiologic mechanisms and potential therapeutic regimes involving lifestyle changes that include caloric restriction or moderate physical activity.
    53. ↑ 53.0 53.1 Ramis MR et al.: Caloric restriction, resveratrol and melatonin: Role of SIRT1 and implications for aging and related-diseases. Mech Ageing Dev 2015. (PMID 25824609) [PubMed] [DOI] Aging is an inevitable and multifactorial biological process. Free radicals have been implicated in aging processes; it is hypothesized that they cause cumulative oxidative damage to crucial macromolecules and are responsible for failure of multiple physiological mechanisms. However, recent investigations have also suggested that free radicals can act as modulators of several signaling pathways such as those related to sirtuins. Caloric restriction is a non-genetic manipulation that extends lifespan of several species and improves healthspan; the belief that many of these benefits are due to the induction of sirtuins has led to the search for sirtuin activators, especially sirtuin 1, the most studied. Resveratrol, a polyphenol found in red grapes, was first known for its antioxidant and antifungal properties, and subsequently has been reported several biological effects, including the activation of sirtuins. Endogenously-produced melatonin, a powerful free radical scavenger, declines with age and its loss contributes to degenerative conditions of aging. Recently, it was reported that melatonin also activates sirtuins, in addition to other functions, such as regulator of circadian rhythms or anti-inflammatory properties. The fact that melatonin and resveratrol are present in various foods, exhibiting possible synergistic effects, suggests the use of dietary ingredients to promote health and longevity.
    54. ↑ Nagarajan S et al.: Uncoupling reproduction from metabolism extends chronological lifespan in yeast. Proc Natl Acad Sci U S A 2014. (PMID 24706810) [PubMed] [DOI] [Full text] Studies of replicative and chronological lifespan in Saccharomyces cerevisiae have advanced understanding of longevity in all eukaryotes. Chronological lifespan in this species is defined as the age-dependent viability of nondividing cells. To date this parameter has only been estimated under calorie restriction, mimicked by starvation. Because postmitotic cells in higher eukaryotes often do not starve, we developed a model yeast system to study cells as they age in the absence of calorie restriction. Yeast cells were encapsulated in a matrix consisting of calcium alginate to form ∼3 mm beads that were packed into bioreactors and fed ad libitum. Under these conditions cells ceased to divide, became heat shock and zymolyase resistant, yet retained high fermentative capacity. Over the course of 17 d, immobilized yeast cells maintained >95% viability, whereas the viability of starving, freely suspended (planktonic) cells decreased to <10%. Immobilized cells exhibited a stable pattern of gene expression that differed markedly from growing or starving planktonic cells, highly expressing genes in glycolysis, cell wall remodeling, and stress resistance, but decreasing transcription of genes in the tricarboxylic acid cycle, and genes that regulate the cell cycle, including master cyclins CDC28 and CLN1. Stress resistance transcription factor MSN4 and its upstream effector RIM15 are conspicuously up-regulated in the immobilized state, and an immobilized rim15 knockout strain fails to exhibit the long-lived, growth-arrested phenotype, suggesting that altered regulation of the Rim15-mediated nutrient-sensing pathway plays an important role in extending yeast chronological lifespan under calorie-unrestricted conditions.
    55. ↑ Huberts DH et al.: Calorie restriction does not elicit a robust extension of replicative lifespan in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2014. (PMID 25071164) [PubMed] [DOI] [Full text] Calorie restriction (CR) is often described as the most robust manner to extend lifespan in a large variety of organisms. Hence, considerable research effort is directed toward understanding the mechanisms underlying CR, especially in the yeast Saccharomyces cerevisiae. However, the effect of CR on lifespan has never been systematically reviewed in this organism. Here, we performed a meta-analysis of replicative lifespan (RLS) data published in more than 40 different papers. Our analysis revealed that there is significant variation in the reported RLS data, which appears to be mainly due to the low number of cells analyzed per experiment. Furthermore, we found that the RLS measured at 2% (wt/vol) glucose in CR experiments is partly biased toward shorter lifespans compared with identical lifespan measurements from other studies. Excluding the 2% (wt/vol) glucose experiments from CR experiments, we determined that the average RLS of the yeast strains BY4741 and BY4742 is 25.9 buds at 2% (wt/vol) glucose and 30.2 buds under CR conditions. RLS measurements with a microfluidic dissection platform produced identical RLS data at 2% (wt/vol) glucose. However, CR conditions did not induce lifespan extension. As we excluded obvious methodological differences, such as temperature and medium, as causes, we conclude that subtle method-specific factors are crucial to induce lifespan extension under CR conditions in S. cerevisiae.
    56. ↑ Tapia PC: Sublethal mitochondrial stress with an attendant stoichiometric augmentation of reactive oxygen species may precipitate many of the beneficial alterations in cellular physiology produced by caloric restriction, intermittent fasting, exercise and dietary phytonutrients: "Mitohormesis" for health and vitality. Med Hypotheses 2006. (PMID 16242247) [PubMed] [DOI] The precise mechanistic sequence producing the beneficial effects on health and lifespan seen with interventions as diverse as caloric restriction, intermittent fasting, exercise, and consumption of dietary phytonutrients is still under active characterization, with large swaths of the research community kept in relative isolation from one another. Among the explanatory models capable of assisting in the identification of precipitating elements responsible for beneficial influences on physiology seen in these states, the hormesis perspective on biological systems under stress has yielded considerable insight into likely evolutionarily consistent organizing principles functioning in all four conditions. Recent experimental findings provide the tantalizing initial lodestones for an entirely new research front examining molecular substrates of stress resistance. In this novel body of research, a surprising new twist has emerged: Reactive oxygen species, derived from the mitochondrial electron transport system, may be necessary triggering elements for a sequence of events that result in benefits ranging from the transiently cytoprotective to organismal-level longevity. With the recent appreciation that reactive oxygen species and reactive nitrogen species function as signaling elements in a interconnected matrix of signal transduction, the entire basis of many widely accepted theories of aging that predominated in the past may need to be reconsidered to facilitate the formulation of an new perspective more correctly informed by the most contemporaneous experimental findings. This perspective, the mitohormesis theory, can be used in many disparate domains of inquiry to potentially explain previous findings, as well as point to new targets of research. The utility of this perspective for research on aging is significant, but beyond that this perspective emphasizes the pressing need to rigorously characterize the specific contribution of the stoichiometry of reactive oxygen species and reactive nitrogen species in the various compartments of the cell to cytoprotection and vitality. Previous findings regarding the influences of free radical chemistry on cellular physiology may have represented assessments examining the consequences of isolated elevation of signaling elements within a larger signal transductive apparatus, rather than definitive characterizations of the only modality of reactive oxygen species (and reactive nitrogen species) influence. In applying this perspective, it may be necessary for the research community, as well as the practicing clinician, to engender a more sanguine perspective on organelle level physiology, as it is now plausible that such entities have an evolutionarily orchestrated capacity to self-regulate that may be pathologically disturbed by overzealous use of antioxidants, particularly in the healthy.
    57. ↑ Ristow M & Zarse K: How increased oxidative stress promotes longevity and metabolic health: The concept of mitochondrial hormesis (mitohormesis). Exp Gerontol 2010. (PMID 20350594) [PubMed] [DOI] Recent evidence suggests that calorie restriction and specifically reduced glucose metabolism induces mitochondrial metabolism to extend life span in various model organisms, including Saccharomyces cerevisiae, Drosophila melanogaster, Caenorhabditis elegans and possibly mice. In conflict with Harman's free radical theory of aging (FRTA), these effects may be due to increased formation of reactive oxygen species (ROS) within the mitochondria causing an adaptive response that culminates in subsequently increased stress resistance assumed to ultimately cause a long-term reduction of oxidative stress. This type of retrograde response has been named mitochondrial hormesis or mitohormesis, and may in addition be applicable to the health-promoting effects of physical exercise in humans and, hypothetically, impaired insulin/IGF-1-signaling in model organisms. Consistently, abrogation of this mitochondrial ROS signal by antioxidants impairs the lifespan-extending and health-promoting capabilities of glucose restriction and physical exercise, respectively. In summary, the findings discussed in this review indicate that ROS are essential signaling molecules which are required to promote health and longevity. Hence, the concept of mitohormesis provides a common mechanistic denominator for the physiological effects of physical exercise, reduced calorie uptake, glucose restriction, and possibly beyond.
    58. ↑ Wang Y: Molecular Links between Caloric Restriction and Sir2/SIRT1 Activation. Diabetes Metab J 2014. (PMID 25349818) [PubMed] [DOI] [Full text] Ageing is the most significant risk factor for a range of prevalent diseases, including cancer, cardiovascular disease, and diabetes. Accordingly, interventions are needed for delaying or preventing disorders associated with the ageing process, i.e., promotion of healthy ageing. Calorie restriction is the only nongenetic and the most robust approach to slow the process of ageing in evolutionarily divergent species, ranging from yeasts, worms, and flies to mammals. Although it has been known for more than 80 years that calorie restriction increases lifespan, a mechanistic understanding of this phenomenon remains elusive. Yeast silent information regulator 2 (Sir2), the founding member of the sirtuin family of protein deacetylases, and its mammalian homologue Sir2-like protein 1 (SIRT1), have been suggested to promote survival and longevity of organisms. SIRT1 exerts protective effects against a number of age-associated disorders. Caloric restriction increases both Sir2 and SIRT1 activity. This review focuses on the mechanistic insights between caloric restriction and Sir2/SIRT1 activation. A number of molecular links, including nicotinamide adenine dinucleotide, nicotinamide, biotin, and related metabolites, are suggested to be the most important conduits mediating caloric restriction-induced Sir2/SIRT1 activation and lifespan extension.
    59. ↑ Cantó C & Auwerx J: Caloric restriction, SIRT1 and longevity. Trends Endocrinol Metab 2009. (PMID 19713122) [PubMed] [DOI] [Full text] More than 70 years after its initial report, caloric restriction stands strong as the most consistent non-pharmacological intervention increasing lifespan and protecting against metabolic disease. Among the different mechanisms by which caloric restriction might act, Sir2/SIRT1 (Silent information regulator 2/Silent information regulator T1) has been the focus of much attention because of its ability to integrate sensing of the metabolic status with adaptive transcriptional outputs. This review focuses on gathered evidence suggesting that Sir2/SIRT1 is a key mediator of the beneficial effects of caloric restriction and addresses the main questions that still need to be answered to consolidate this hypothesis.
    60. ↑ Ghosh HS et al.: SIRT1 negatively regulates the mammalian target of rapamycin. PLoS One 2010. (PMID 20169165) [PubMed] [DOI] [Full text] The IGF/mTOR pathway, which is modulated by nutrients, growth factors, energy status and cellular stress regulates aging in various organisms. SIRT1 is a NAD+ dependent deacetylase that is known to regulate caloric restriction mediated longevity in model organisms, and has also been linked to the insulin/IGF signaling pathway. Here we investigated the potential regulation of mTOR signaling by SIRT1 in response to nutrients and cellular stress. We demonstrate that SIRT1 deficiency results in elevated mTOR signaling, which is not abolished by stress conditions. The SIRT1 activator resveratrol reduces, whereas SIRT1 inhibitor nicotinamide enhances mTOR activity in a SIRT1 dependent manner. Furthermore, we demonstrate that SIRT1 interacts with TSC2, a component of the mTOR inhibitory-complex upstream to mTORC1, and regulates mTOR signaling in a TSC2 dependent manner. These results demonstrate that SIRT1 negatively regulates mTOR signaling potentially through the TSC1/2 complex.
    61. ↑ Austad S: Recent advances in vertebrate aging research 2009. Aging Cell 2010. (PMID 20331443) [PubMed] [DOI] Among the notable trends seen in this year's highlights in mammalian aging research is an awakening of interest in the assessment of age-related measures of mouse health in addition to the traditional focus on longevity. One finding of note is that overexpression of telomerase extended life and improved several indices of health in mice that had previously been genetically rendered cancer resistant. In another study, resveratrol supplementation led to amelioration of several degenerative conditions without affecting mouse lifespan. A primate dietary restriction (DR) study found that restriction led to major improvements in glucoregulatory status along with provocative but less striking effects on survival. Visceral fat removal in rats improved their survival, although not as dramatically as DR. An unexpected result showing the power of genetic background effects was that DR shortened the lifespan of long-lived mice bearing Prop1(df), whereas a previous report in a different background had found DR to extend the lifespan of Prop1(df) mice. Treatment with the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, enhanced the survival of even elderly mice and improved their vaccine response. Genetic inhibition of a TOR target made female, but not male, mice live longer. This year saw the mTOR network firmly established as a major modulator of mammalian lifespan.
    62. ↑ Harrison DE et al.: Rapamycin fed late in life extends lifespan in genetically heterogeneous mice. Nature 2009. (PMID 19587680) [PubMed] [DOI] [Full text] Inhibition of the TOR signalling pathway by genetic or pharmacological intervention extends lifespan in invertebrates, including yeast, nematodes and fruitflies; however, whether inhibition of mTOR signalling can extend lifespan in a mammalian species was unknown. Here we report that rapamycin, an inhibitor of the mTOR pathway, extends median and maximal lifespan of both male and female mice when fed beginning at 600 days of age. On the basis of age at 90% mortality, rapamycin led to an increase of 14% for females and 9% for males. The effect was seen at three independent test sites in genetically heterogeneous mice, chosen to avoid genotype-specific effects on disease susceptibility. Disease patterns of rapamycin-treated mice did not differ from those of control mice. In a separate study, rapamycin fed to mice beginning at 270 days of age also increased survival in both males and females, based on an interim analysis conducted near the median survival point. Rapamycin may extend lifespan by postponing death from cancer, by retarding mechanisms of ageing, or both. To our knowledge, these are the first results to demonstrate a role for mTOR signalling in the regulation of mammalian lifespan, as well as pharmacological extension of lifespan in both genders. These findings have implications for further development of interventions targeting mTOR for the treatment and prevention of age-related diseases.
    63. ↑ Anderson RM & Weindruch R: Metabolic reprogramming in dietary restriction. Interdiscip Top Gerontol 2007. (PMID 17063031) [PubMed] [DOI] [Full text] It is widely accepted that energy intake restriction without essential nutrient deficiency delays the onset of aging and extends life span. The mechanism underlying this phenomenon is still unknown though a number of different, nonmutually exclusive explanations have been proposed. In each of these, different facets of physiology play the more significant role in the mechanism of aging retardation. Some examples include the altered lipid composition model, the immune response model and models describing changes in endocrine function. In this paper we propose the hypothesis that metabolic reprogramming is the key event in the mechanism of dietary restriction, and the physiological effects at the cellular, tissue and organismal level may be understood in terms of this initial event.
    64. ↑ Higami Y et al.: Adipose tissue energy metabolism: altered gene expression profile of mice subjected to long-term caloric restriction. FASEB J 2004. (PMID 14688200) [PubMed] [DOI] We investigated the influences of short-term and lifespan-prolonging long-term caloric restriction (LCR) on gene expression in white adipose tissue (WAT). Over 11,000 genes were examined using high-density oligonucleotide microarrays in four groups of 10- to 11-month-old male C57Bl6 mice that were either fasted for 18 h before death (F), subjected to short-term caloric restriction for 23 days (SCR), or LCR for 9 months and compared with nonfasted control (CO) mice. Only a few transcripts of F and SCR were differentially expressed compared with CO mice. In contrast, 345 transcripts of 6,266 genes found to be expressed in WAT were altered significantly by LCR. The expression of several genes encoding proteins involved in energy metabolism was increased by LCR. Further, many of the shifts in gene expression after LCR are known to occur during adipocyte differentiation. Selected LCR-associated alterations of gene expression were supported by quantitative reverse transcriptase-polymerase chain reaction, histology, and histochemical examinations. Our data provide new insights on the metabolic state associated with aging retardation by LCR.
    65. ↑ Higami Y et al.: Energy restriction lowers the expression of genes linked to inflammation, the cytoskeleton, the extracellular matrix, and angiogenesis in mouse adipose tissue. J Nutr 2006. (PMID 16424110) [PubMed] [DOI] Using high-density oligonucleotide microarrays, we examined the actions of energy restriction (ER) on the expression of >11,000 genes in epididymal white adipose tissue (WAT) of 10- to 11-mo-old male C57Bl6 mice. Four groups were studied: controls not subjected to food restriction (CO), food-restricted 18 h before being killed (FR), short-term ER for 23 d (SER), and long-term ER for 9 mo (LER). As we reported previously, compared with CO mice, FR and SER minimally influenced the gene expression profiles; however, 345 transcripts of 6,266 genes determined to be expressed in WAT were significantly altered by LER. We focus here on the 109 (31%) of these genes that were involved in either inflammation (56 genes), cytoskeleton (16 genes), extracellular matrix (23 genes), or angiogenesis (14 genes). Among these 109 genes, 104 transcripts (95%) were down regulated by LER. Western blotting for heat shock protein 47 and osteonectin, and immunohistochemical staining for hypoxia inducible factor (HIF)-1alpha), supported the microarray data that LER down regulated the expressions of these genes. Additionally, a 75% reduction in adipocyte size with LER reflected the change in the expression of genes involved in cell morphology. Our findings provide evidence that LER suppresses the expression of genes encoding inflammatory molecules in WAT while promoting structural remodeling of the cytoskeleton, extracellular matrix, and vasculature. These alterations may play an important role in the protection against WAT-derived inflammation and in lifespan extension by LER.
    66. ↑ Anderson RM et al.: Caloric restriction and aging: studies in mice and monkeys. Toxicol Pathol 2009. (PMID 19075044) [PubMed] [DOI] [Full text] It is widely accepted that caloric restriction (CR) without malnutrition delays the onset of aging and extends lifespan in diverse animal models including yeast, worms, flies, and laboratory rodents. The mechanism underlying this phenomenon is still unknown. We have hypothesized that a reprogramming of energy metabolism is a key event in the mechanism of CR (Anderson and Weindruch 2007). Data will be presented from studies of mice on CR, the results of which lend support to this hypothesis. Effects of long-term CR (but not short-term CR) on gene expression in white adipose tissue (WAT) are overt. In mice and monkeys, a chronic 30% reduction in energy intake yields a decrease in adiposity of approximately 70%. In mouse epididymal WAT, long-term CR causes overt shifts in the gene expression profile: CR increases the expression of genes involved in energy metabolism (Higami et al. 2004), and it down-regulates the expression of more than 50 pro-inflammatory genes (Higami et al. 2006). Whether aging retardation occurs in primates on CR is unknown. We have been investigating this issue in rhesus monkeys subjected to CR since 1989 and will discuss the current status of this project. A new finding from this project is that CR reduces the rate of age-associated muscle loss (sarcopenia) in monkeys (Colman et al. 2008).
    67. ↑ Mazzoccoli G et al.: Caloric restriction and aging stem cells: the stick and the carrot?. Exp Gerontol 2014. (PMID 24211426) [PubMed] [DOI] Adult tissue stem cells have the ability to adjust to environmental changes and affect also the proliferation of neighboring cells, with important consequences on tissue maintenance and regeneration. Stem cell renewal and proliferation is strongly regulated during aging of the organism. Caloric restriction is the most powerful anti-aging strategy conserved throughout evolution in the animal kingdom. Recent studies relate the properties of caloric restriction to its ability in reprogramming stem-like cell states and in prolonging the capacity of stem cells to self-renew, proliferate, differentiate, and replace cells in several adult tissues. However this general paradigm presents with exceptions. The scope of this review is to highlight how caloric restriction impacts on diverse stem cell compartments and, by doing so, might differentially delay aging in the tissues of lower and higher organisms.
    68. ↑ Maalouf M et al.: The neuroprotective properties of calorie restriction, the ketogenic diet, and ketone bodies. Brain Res Rev 2009. (PMID 18845187) [PubMed] [DOI] [Full text] Both calorie restriction and the ketogenic diet possess broad therapeutic potential in various clinical settings and in various animal models of neurological disease. Following calorie restriction or consumption of a ketogenic diet, there is notable improvement in mitochondrial function, a decrease in the expression of apoptotic and inflammatory mediators and an increase in the activity of neurotrophic factors. However, despite these intriguing observations, it is not yet clear which of these mechanisms account for the observed neuroprotective effects. Furthermore, limited compliance and concern for adverse effects hamper efforts at broader clinical application. Recent research aimed at identifying compounds that can reproduce, at least partially, the neuroprotective effects of the diets with less demanding changes to food intake suggests that ketone bodies might represent an appropriate candidate. Ketone bodies protect neurons against multiple types of neuronal injury and are associated with mitochondrial effects similar to those described during calorie restriction or ketogenic diet treatment. The present review summarizes the neuroprotective effects of calorie restriction, of the ketogenic diet and of ketone bodies, and compares their putative mechanisms of action.
    69. ↑ 69.0 69.1 Lin AL et al.: Caloric restriction increases ketone bodies metabolism and preserves blood flow in aging brain. Neurobiol Aging 2015. (PMID 25896951) [PubMed] [DOI] [Full text] Caloric restriction (CR) has been shown to increase the life span and health span of a broad range of species. However, CR effects on in vivo brain functions are far from explored. In this study, we used multimetric neuroimaging methods to characterize the CR-induced changes of brain metabolic and vascular functions in aging rats. We found that old rats (24 months of age) with CR diet had reduced glucose uptake and lactate concentration, but increased ketone bodies level, compared with the age-matched and young (5 months of age) controls. The shifted metabolism was associated with preserved vascular function: old CR rats also had maintained cerebral blood flow relative to the age-matched controls. When investigating the metabolites in mitochondrial tricarboxylic acid cycle, we found that citrate and α-ketoglutarate were preserved in the old CR rats. We suggest that CR is neuroprotective; ketone bodies, cerebral blood flow, and α-ketoglutarate may play important roles in preserving brain physiology in aging.
    70. ↑ Minina EA et al.: Autophagy mediates caloric restriction-induced lifespan extension in Arabidopsis. Aging Cell 2013. (PMID 23331488) [PubMed] [DOI] Caloric restriction (CR) extends lifespan in various heterotrophic organisms ranging from yeasts to mammals, but whether a similar phenomenon occurs in plants remains unknown. Plants are autotrophs and use their photosynthetic machinery to convert light energy into the chemical energy of glucose and other organic compounds. As the rate of photosynthesis is proportional to the level of photosynthetically active radiation, the CR in plants can be modeled by lowering light intensity. Here, we report that low light intensity extends the lifespan in Arabidopsis through the mechanisms triggering autophagy, the major catabolic process that recycles damaged and potentially harmful cellular material. Knockout of autophagy-related genes results in the short lifespan and suppression of the lifespan-extending effect of the CR. Our data demonstrate that the autophagy-dependent mechanism of CR-induced lifespan extension is conserved between autotrophs and heterotrophs.
    71. ↑ Cavallini G et al.: Towards an understanding of the anti-aging mechanism of caloric restriction. Curr Aging Sci 2008. (PMID 20021367) [PubMed] [DOI] Accumulation of oxidatively altered cell components may play a role in the age-related cell deterioration and associated diseases. Caloric restriction is the most robust anti-aging intervention that extends lifespan and retards the appearance of age-associated diseases. Autophagy is a highly conserved cell-repair process in which the cytoplasm, including excess or aberrant organelles, is sequestered into double-membrane vesicles and delivered to the degradative vacuoles. Autophagy has an essential role in adaptation to fasting and changing environmental conditions. Several pieces of evidence show that autophagy may be an essential part in the anti-aging mechanism of caloric restriction: 1. The function of autophagy declines with increasing age; 2. The temporal pattern of the decline parallels the changes in biomarkers of membrane aging and in amino acid and hormone signalling. 3. These age-dependent changes in autophagy are prevented by calorie restriction. 4. The prevention of the changes in autophagy and biomarkers of aging co-varies with the effects of calorie restriction on life-span. 5. A long-lasting inhibition of autophagy accelerates the process of aging. 6. A long-lasting stimulation of autophagy retards the process of aging in rats. 7. Stimulation of autophagy may rescue older cells from accumulation of altered mtDNA. 8. Stimulation of autophagy counteracts the age-related hypercholesterolemia in rodents. It is suggested that the pharmacological intensification of suppression of aging (P.I.S.A. treatment) by the stimulation of autophagy might prove to be a big step towards retardation of aging and prevention of age-associated diseases in humans.
    72. ↑ Roth GS et al.: Effects of dietary caloric restriction and aging on thyroid hormones of rhesus monkeys. Horm Metab Res 2002. (PMID 12189585) [PubMed] [DOI] Plasma levels of thyroid hormones - triiodothyronine (T 3 ), thyroxin (T 4 ), and thyroid-stimulating hormone (TSH) were measured in male and female rhesus monkeys (Macaca mulatta) fed either ad libitum or a 30 % calorie-restricted (CR) diet (males for 11 years; females for 6 years). The same hormones were measured in another group of young male rhesus monkeys during adaptation to the 30 % CR regimen. Both long- and shorter-term CR diet lowered total T 3 in plasma of the monkeys. The effect appeared to be greater in younger monkeys than in older counterparts. No effects of CR diet were detected for either free or total T 4, although unlike T 3, levels of this hormone decreased with age. TSH levels also decreased with age, and were increased by long-term CR diet in older monkeys only. No consistent effects of shorter-term CR diet were observed for TSH. In the light of the effects of the thyroid axis on overall metabolism, these results suggest a possible mechanism by which CR diets may elicit their well-known beneficial 'anti-aging' effects in mammals.
    73. ↑ Testa G et al.: Calorie restriction and dietary restriction mimetics: a strategy for improving healthy aging and longevity. Curr Pharm Des 2014. (PMID 24079773) [PubMed] [DOI] Improvements in health care have increased human life expectancy in recent decades, and the elderly population is thus increasing in most developed countries. Unfortunately this still means increased years of poor health or disability. Since it is not yet possible to modify our genetic background, the best anti-aging strategy is currently to intervene on environmental factors, aiming to reduce the incidence of risk factors of poor health. Calorie restriction (CR) with adequate nutrition is the only non-genetic, and the most consistent non-pharmacological intervention that extends lifespan in model organisms from yeast to mammals, and protects against the deterioration of biological functions, delaying or reducing the risk of many age-related diseases. The biological mechanisms of CR's beneficial effects include modifications in energy metabolism, oxidative stress, insulin sensitivity, inflammation, autophagy, neuroendocrine function and induction of hormesis/xenohormesis response. The molecular signalling pathways mediating the anti-aging effect of CR include sirtuins, peroxisome proliferator activated receptor G coactivator-1α, AMP-activated protein kinase, insulin/insulin growth factor-1, and target of rapamycin, which form a pretty interacting network. However, most people would not comply with such a rigorous dietary program; research is thus increasingly aimed at determining the feasibility and efficacy of natural and/or pharmacological CR mimetic molecules/ treatments without lowering food intake, particularly in mid- to late-life periods. Likely candidates act on the same signalling pathways as CR, and include resveratrol and other polyphenols, rapamycin, 2-deoxy-D-glucose and other glycolytic inhibitors, insulin pathway and AMP-activated protein kinase activators, autophagy stimulators, alpha-lipoic acid, and other antioxidants.
    74. ↑ Ingram DK et al.: Calorie restriction mimetics: an emerging research field. Aging Cell 2006. (PMID 16626389) [PubMed] [DOI] When considering all possible aging interventions evaluated to date, it is clear that calorie restriction (CR) remains the most robust. Studies in numerous species have demonstrated that reduction of calories 30-50% below ad libitum levels of a nutritious diet can increase lifespan, reduce the incidence and delay the onset of age-related diseases, improve stress resistance, and decelerate functional decline. A current major focus of this research area is whether this nutritional intervention is relevant to human aging. Evidence emerging from studies in rhesus monkeys suggests that their response to CR parallels that observed in rodents. To assess CR effects in humans, clinical trials have been initiated. However, even if results from these studies could eventually substantiate CR as an effective pro-longevity strategy for humans, the utility of this intervention would be hampered because of the degree and length of restriction required. As an alternative strategy, new research has focused on the development of 'CR mimetics'. The objective of this strategy is to identify compounds that mimic CR effects by targeting metabolic and stress response pathways affected by CR, but without actually restricting caloric intake. For example, drugs that inhibit glycolysis (2-deoxyglucose), enhance insulin action (metformin), or affect stress signaling pathways (resveratrol), are being assessed as CR mimetics (CRM). Promising results have emerged from initial studies regarding physiological responses which resemble those observed in CR (e.g. reduced body temperature and plasma insulin) as well as protection against neurotoxicity (e.g. enhanced dopamine action and up-regulated neurotrophic factors). Ultimately, lifespan analyses in addition to expanded toxicity studies must be accomplished to fully assess the potential of any CRM. Nonetheless, this strategy clearly offers a very promising and expanding research endeavor.
    75. ↑ Yao J et al.: 2-Deoxy-D-glucose treatment induces ketogenesis, sustains mitochondrial function, and reduces pathology in female mouse model of Alzheimer's disease. PLoS One 2011. (PMID 21747957) [PubMed] [DOI] [Full text] Previously, we demonstrated that mitochondrial bioenergetic deficits preceded Alzheimer's disease (AD) pathology in the female triple-transgenic AD (3xTgAD) mouse model. In parallel, 3xTgAD mice exhibited elevated expression of ketogenic markers, indicating a compensatory mechanism for energy production in brain. This compensatory response to generate an alternative fuel source was temporary and diminished with disease progression. To determine whether this compensatory alternative fuel system could be sustained, we investigated the impact of 2-deoxy-D-glucose (2-DG), a compound known to induce ketogenesis, on bioenergetic function and AD pathology burden in brain. 6-month-old female 3xTgAD mice were fed either a regular diet (AIN-93G) or a diet containing 0.04% 2-DG for 7 weeks. 2-DG diet significantly increased serum ketone body level and brain expression of enzymes required for ketone body metabolism. The 2-DG-induced maintenance of mitochondrial bioenergetics was paralleled by simultaneous reduction in oxidative stress. Further, 2-DG treated mice exhibited a significant reduction of both amyloid precursor protein (APP) and amyloid beta (Aβ) oligomers, which was paralleled by significantly increased α-secretase and decreased γ-secretase expression, indicating that 2-DG induced a shift towards a non-amyloidogenic pathway. In addition, 2-DG increased expression of genes involved in Aβ clearance pathways, degradation, sequestering, and transport. Concomitant with increased bioenergetic capacity and reduced β-amyloid burden, 2-DG significantly increased expression of neurotrophic growth factors, BDNF and NGF. Results of these analyses demonstrate that dietary 2-DG treatment increased ketogenesis and ketone metabolism, enhanced mitochondrial bioenergetic capacity, reduced β-amyloid generation and increased mechanisms of β-amyloid clearance. Further, these data link bioenergetic capacity with β-amyloid generation and demonstrate that β-amyloid burden was dynamic and reversible, as 2-DG reduced activation of the amyloidogenic pathway and increased mechanisms of β-amyloid clearance. Collectively, these data provide preclinical evidence for dietary 2-DG as a disease-modifying intervention to delay progression of bioenergetic deficits in brain and associated β-amyloid burden.
    76. ↑ MARK A. LANE, DONALD K. INGRAM, and GEORGE S. ROTH. 2-Deoxy-D-Glucose Feeding in Rats Mimics Physiologic Effects of Calorie Restriction. Journal of Anti-Aging Medicine.Jan 1998.327-337. [DOI]
    77. ↑ Smith DL et al.: Metformin supplementation and life span in Fischer-344 rats. J Gerontol A Biol Sci Med Sci 2010. (PMID 20304770) [PubMed] [DOI] [Full text] Calorie restriction (CR) has been known for more than 70 years to extend life span and delay disease in rodent models. Metformin administration in rodent disease models has been shown to delay cancer incidence and progression, reduce cardiovascular disease and extend life span. To more directly test the potential of metformin supplementation (300 mg/kg/day) as a CR mimetic, life-span studies were performed in Fischer-344 rats and compared with ad libitum feeding and CR (30%). The CR group had significantly reduced food intake and body weight throughout the study. Body weight was significantly reduced in the metformin group compared with control during the middle of the study, despite similar weekly food intake. Although CR significantly extended early life span (25th quantile), metformin supplementation did not significantly increase life span at any quantile (25th, 50th, 75th, or 90th), overall or maximum life span (p > .05) compared with control.
    78. ↑ Lebovitz HE & Feinglos MN: Mechanism of action of the second-generation sulfonylurea glipizide. Am J Med 1983. (PMID 6369967) [PubMed] [DOI] Glipizide, a second-generation sulfonylurea, has potent antidiabetic actions in patients with noninsulin-dependent diabetes mellitus. The effects of glipizide treatment on insulin sensitivity, glucose-mediated insulin secretion, and glucose utilization were measured in newly diagnosed or untreated patients with noninsulin-dependent diabetes mellitus. The data indicate that the antidiabetic action of glipizide is primarily mediated by a potentiation of insulin action and, to a less significant and more variable degree, by an increase in nutrient-mediated insulin secretion. Studies in normal mice and dogs show that glipizide potentiation of insulin action is associated with an increase in plasma membrane insulin receptor number, involves some postreceptor events, and is significantly greater on peripheral uptake of glucose than suppression of hepatic glucose production. The initial event in glipizide action on beta cells appears to be binding to a specific plasma membrane receptor.
    79. ↑ Ye JM et al.: Direct demonstration of lipid sequestration as a mechanism by which rosiglitazone prevents fatty-acid-induced insulin resistance in the rat: comparison with metformin. Diabetologia 2004. (PMID 15232684) [PubMed] [DOI] AIMS/HYPOTHESIS: Thiazolidinediones can enhance clearance of whole-body non-esterified fatty acids and protect against the insulin resistance that develops during an acute lipid load. The present study used [(3)H]-R-bromopalmitate to compare the effects of the thiazolidinedione, rosiglitazone, and the biguanide, metformin, on insulin action and the tissue-specific fate of non-esterified fatty acids in rats during lipid infusion. METHODS: Normal rats were treated with rosiglitazone or metformin for 7 days. Triglyceride/heparin (to elevate non-esterified fatty acids) or glycerol (control) were then infused for 5 h, with a hyperinsulinaemic clamp being performed between the 3rd and 5th hours. RESULTS: Rosiglitazone and metformin prevented fatty-acid-induced insulin resistance (reduced clamp glucose infusion rate). Both drugs improved insulin-mediated suppression of hepatic glucose output but only rosiglitazone enhanced systemic non-esterified fatty acid clearance (plateau plasma non-esterified fatty acids reduced by 40%). Despite this decrease in plateau plasma non-esterified fatty acids, rosiglitazone increased fatty acid uptake (two-fold) into adipose tissue and reduced fatty acid uptake into liver (by 40%) and muscle (by 30%), as well as reducing liver long-chain fatty acyl CoA accumulation (by 30%). Both rosiglitazone and metformin increased liver AMP-activated protein kinase activity, a possible mediator of the protective effects on insulin action, but in contrast to rosiglitazone, metformin had no significant effect on non-esterified fatty acid kinetics or relative tissue fatty acid uptake. CONCLUSIONS/INTERPRETATION: These results directly demonstrate the "lipid steal" mechanism, by which thiazolidinediones help prevent fatty-acid-induced insulin resistance. The contrasting mechanisms of action of rosiglitazone and metformin could be beneficial when both drugs are used in combination to treat insulin resistance.
    80. ↑ Rimbach G et al.: Dietary isoflavones in the prevention of cardiovascular disease--a molecular perspective. Food Chem Toxicol 2008. (PMID 17689850) [PubMed] [DOI] The Food and Drugs Administration has approved a health claim for soy based on clinical trials and epidemiological data indicating that high soy consumption is associated with a lower risk of coronary artery disease. Soy products contain a group of compounds called isoflavones, with genistein and daidzein being the most abundant. A number of cardioprotective benefits have been attributed to dietary isoflavones including a reduction in LDL cholesterol, an inhibition of pro-inflammatory cytokines, cell adhesion proteins and inducible nitric oxide production, potential reduction in the susceptibility of the LDL particle to oxidation, inhibition of platelet aggregation and an improvement in vascular reactivity. There is increasing interest in the use of nutrigenomic methods to understand the mechanisms by which isoflavones induce these changes, and in the use of nutrigenetics to understand why the effects vary between individuals. Nutrigenomics is a rapidly growing field making use of molecular biology methodologies, such as microarray technology and proteomics, to study how specific nutrients or diets affect gene expression and cellular protein levels. The analysis of differential gene expression and protein levels in endothelial cells, macrophages and smooth muscle cells is critical to elucidating the sequence of events leading to the formation of atherosclerotic lesions, and to understanding the potential anti-atherogenic properties of soy isoflavones. An increasing number of studies demonstrate a significant impact of genetic variation on changes in cardiovascular risk factors in response to dietary intervention. Nutrigenetic effects of this type have recently been reported for dietary isoflavones, and may help to explain some of the disparities in the current literature concerning isoflavones and cardiovascular health.
    81. ↑ Agarwal B & Baur JA: Resveratrol and life extension. Ann N Y Acad Sci 2011. (PMID 21261652) [PubMed] [DOI] Age is the most important risk factor for diseases affecting the Western world, and slowing age-related degeneration would greatly improve the quality of human life. In rodents, caloric restriction (CR) extends lifespan by up to 50%. However, attempts to mimic the effects of CR pharmacologically have been limited by our poor understanding of the mechanisms involved. SIRT1 is proposed to mediate key aspects of CR, and small molecule activators may therefore act as CR mimetics. The polyphenol resveratrol activates SIRT1 in an in vitro assay, and produces changes that resemble CR in vivo, including improvements in insulin sensitivity, endurance, and overall survival in obese mice. However, resveratrol has numerous other targets that could contribute to its health benefits. Moreover, unlike bona fide CR, resveratrol has not been shown to extend lifespan in lean mice. Overexpression of SIRT1 or treatment with a novel activator is sufficient to improve metabolism, supporting the idea that resveratrol could act through this pathway. However, the poor phenotype of SIRT1 null mice has thus far precluded a more definitive test.
    82. ↑ Yamauchi T et al.: The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity. Nat Med 2001. (PMID 11479627) [PubMed] [DOI] Adiponectin is an adipocyte-derived hormone. Recent genome-wide scans have mapped a susceptibility locus for type 2 diabetes and metabolic syndrome to chromosome 3q27, where the gene encoding adiponectin is located. Here we show that decreased expression of adiponectin correlates with insulin resistance in mouse models of altered insulin sensitivity. Adiponectin decreases insulin resistance by decreasing triglyceride content in muscle and liver in obese mice. This effect results from increased expression of molecules involved in both fatty-acid combustion and energy dissipation in muscle. Moreover, insulin resistance in lipoatrophic mice was completely reversed by the combination of physiological doses of adiponectin and leptin, but only partially by either adiponectin or leptin alone. We conclude that decreased adiponectin is implicated in the development of insulin resistance in mouse models of both obesity and lipoatrophy. These data also indicate that the replenishment of adiponectin might provide a novel treatment modality for insulin resistance and type 2 diabetes.
    83. ↑ Chiba T et al.: Development of calorie restriction mimetics as therapeutics for obesity, diabetes, inflammatory and neurodegenerative diseases. Curr Genomics 2010. (PMID 21629433) [PubMed] [DOI] [Full text] Calorie restriction (CR) is the most robust intervention that decreases morbidity and mortality, and thereby increases the lifespan of many organisms. Although the signaling pathways involved in the beneficial effects of CR are not yet fully understood. Several candidate pathways and key molecules have been identified. The effects of CR are highly conserved from lower organisms such as yeast to higher mammals such as rodents and monkeys. Recent studies have also demonstrated beneficial effects of CR in humans, although we need much longer studies to evaluate whether CR also increases the lifespan of humans. In reality, it is difficult for us to conduct CR interventions in humans because the subjects must be kept in a state of hunger and the duration of this state needed to achieve a clinically meaningful effect is still unknown. Thus, research in this field is focusing on the development of molecules that mimic the beneficial effects of CR without reducing food intake. Some of these candidate molecules include plant-derived functional chemicals (phyto-chemicals), synthetic small molecules, and endocrine molecules such as adipokines. Several studies have already shown that this research field may yield novel drugs for the treatment of age-related diseases such as diabetes. In this article, we describe the target pathways, candidate molecules, and strategies to develop CR mimetics.
    84. ↑ Menssen A et al.: The c-MYC oncoprotein, the NAMPT enzyme, the SIRT1-inhibitor DBC1, and the SIRT1 deacetylase form a positive feedback loop. Proc Natl Acad Sci U S A 2012. (PMID 22190494) [PubMed] [DOI] [Full text] Silent information regulator 1 (SIRT1) represents an NAD(+)-dependent deacetylase that inhibits proapoptotic factors including p53. Here we determined whether SIRT1 is downstream of the prototypic c-MYC oncogene, which is activated in the majority of tumors. Elevated expression of c-MYC in human colorectal cancer correlated with increased SIRT1 protein levels. Activation of a conditional c-MYC allele induced increased levels of SIRT1 protein, NAD(+), and nicotinamide-phosphoribosyltransferase (NAMPT) mRNA in several cell types. This increase in SIRT1 required the induction of the NAMPT gene by c-MYC. NAMPT is the rate-limiting enzyme of the NAD(+) salvage pathway and enhances SIRT1 activity by increasing the amount of NAD(+). c-MYC also contributed to SIRT1 activation by sequestering the SIRT1 inhibitor deleted in breast cancer 1 (DBC1) from the SIRT1 protein. In primary human fibroblasts previously immortalized by introduction of c-MYC, down-regulation of SIRT1 induced senescence and apoptosis. In various cell lines inactivation of SIRT1 by RNA interference, chemical inhibitors, or ectopic DBC1 enhanced c-MYC-induced apoptosis. Furthermore, SIRT1 directly bound to and deacetylated c-MYC. Enforced SIRT1 expression increased and depletion/inhibition of SIRT1 reduced c-MYC stability. Depletion/inhibition of SIRT1 correlated with reduced lysine 63-linked polyubiquitination of c-Myc, which presumably destabilizes c-MYC by supporting degradative lysine 48-linked polyubiquitination. Moreover, SIRT1 enhanced the transcriptional activity of c-MYC. Taken together, these results show that c-MYC activates SIRT1, which in turn promotes c-MYC function. Furthermore, SIRT1 suppressed cellular senescence in cells with deregulated c-MYC expression and also inhibited c-MYC-induced apoptosis. Constitutive activation of this positive feedback loop may contribute to the development and maintenance of tumors in the context of deregulated c-MYC.
    85. ↑ Mattison JA et al.: Caloric restriction improves health and survival of rhesus monkeys. Nat Commun 2017. (PMID 28094793) [PubMed] [DOI] [Full text] Caloric restriction (CR) without malnutrition extends lifespan and delays the onset of age-related disorders in most species but its impact in nonhuman primates has been controversial. In the late 1980s two parallel studies were initiated to determine the effect of CR in rhesus monkeys. The University of Wisconsin study reported a significant positive impact of CR on survival, but the National Institute on Aging study detected no significant survival effect. Here we present a direct comparison of longitudinal data from both studies including survival, bodyweight, food intake, fasting glucose levels and age-related morbidity. We describe differences in study design that could contribute to differences in outcomes, and we report species specificity in the impact of CR in terms of optimal onset and diet. Taken together these data confirm that health benefits of CR are conserved in monkeys and suggest that CR mechanisms are likely translatable to human health.
    86. ↑ Colman RJ et al.: Caloric restriction reduces age-related and all-cause mortality in rhesus monkeys. Nat Commun 2014. (PMID 24691430) [PubMed] [DOI] [Full text] Caloric restriction (CR) without malnutrition increases longevity and delays the onset of age-associated disorders in short-lived species, from unicellular organisms to laboratory mice and rats. The value of CR as a tool to understand human ageing relies on translatability of CR's effects in primates. Here we show that CR significantly improves age-related and all-cause survival in monkeys on a long-term ~30% restricted diet since young adulthood. These data contrast with observations in the 2012 NIA intramural study report, where a difference in survival was not detected between control-fed and CR monkeys. A comparison of body weight of control animals from both studies with each other, and against data collected in a multi-centred relational database of primate ageing, suggests that the NIA control monkeys were effectively undergoing CR. Our data indicate that the benefits of CR on ageing are conserved in primates.
    87. ↑ Waziry R et al.: Effect of long-term caloric restriction on DNA methylation measures of biological aging in healthy adults from the CALERIE trial. Nat Aging 2023. (PMID 37118425) [PubMed] [DOI] [Full text] The geroscience hypothesis proposes that therapy to slow or reverse molecular changes that occur with aging can delay or prevent multiple chronic diseases and extend healthy lifespan1-3. Caloric restriction (CR), defined as lessening caloric intake without depriving essential nutrients4, results in changes in molecular processes that have been associated with aging, including DNA methylation (DNAm)5-7, and is established to increase healthy lifespan in multiple species8,9. Here we report the results of a post hoc analysis of the influence of CR on DNAm measures of aging in blood samples from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) trial, a randomized controlled trial in which n = 220 adults without obesity were randomized to 25% CR or ad libitum control diet for 2 yr (ref. 10). We found that CALERIE intervention slowed the pace of aging, as measured by the DunedinPACE DNAm algorithm, but did not lead to significant changes in biological age estimates measured by various DNAm clocks including PhenoAge and GrimAge. Treatment effect sizes were small. Nevertheless, modest slowing of the pace of aging can have profound effects on population health11-13. The finding that CR modified DunedinPACE in a randomized controlled trial supports the geroscience hypothesis, building on evidence from small and uncontrolled studies14-16 and contrasting with reports that biological aging may not be modifiable17. Ultimately, a conclusive test of the geroscience hypothesis will require trials with long-term follow-up to establish effects of intervention on primary healthy-aging endpoints, including incidence of chronic disease and mortality18-20.
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