Nicotinamide Mononucleotide (NMN): Difference between revisions

One hypothesis is that NMN can directly enter cells through specific transporters. The ''Slc12a8'' transporter in the aged mouse ileum is an example, suggested to facilitate NMN's direct absorption<ref name="ref160">{{pmid|31131364}}</ref>. However, this notion has faced challenges due to conflicting research findings<ref name="ref161">[Source 161]</ref><ref name="ref162">[Source 162]</ref>, and the functionality of ''Slc12a8'' in humans is yet to be conclusively determined.

An alternative and more widely accepted theory proposes that NMN is not directly used by cells. Instead, it is first converted to '''Nicotinamide Riboside (NR)''' through dephosphorylation before cellular absorption. This conversion is mediated by ectonucleotidases like CD73. Upon entry into the cell as NR via equilibrative nucleoside transporters (ENT1, ENT2, and ENT4), it is phosphorylated into NMN<ref name="ref162">[Source 162]</ref><ref name="ref163">[Source 163]</ref>. Studies, such as those by Kim et al., indicate that orally ingested NMN is predominantly converted to NR in intestinal tissue before absorption, challenging the direct precursor role of NMN{{pmid|37463842}}<ref name="ref168">[Source 168]</ref>.