Study summary · research use only
Nicotinamide riboside and nicotinamide mononucleotide facilitate NAD(+) synthesis via enterohepatic circulation
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
In this mouse study, the authors traced the metabolic fate of orally and intravenously administered nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) using NAD+ metabolomics. Only a small portion of orally administered NMN and NR was reported to be directly absorbed from the small intestine, with most undergoing gut microbiota-mediated deamidation and conversion to nicotinic acid (NA). Intravenously administered NMN and NR were reported to be rapidly degraded into nicotinamide, secreted to bile, and then deamidated to NA by gut microbiota, with enterohepatic circulated NA preferentially used in the liver. The authors describe NMN and NR as being indirectly converted to NAD+ via these metabolic pathways.
Abstract
Decreased nicotinamide adenine dinucleotide (oxidized form) (NAD+) levels are reportedly associated with several aging-related disorders. Thus, supplementation with NAD+ precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), exhibits beneficial effects against these disorders. However, the in vivo metabolic pathways of NMN and NR remain to be elucidated. In this study, we comprehensively analyzed the fate of orally and intravenously administered NMN and NR in mice using NAD+ metabolomics. We found that only a small portion of orally administered NMN and NR was directly absorbed from the small intestine and that most of them underwent gut microbiota-mediated deamidation and conversion to nicotinic acid (NA). Moreover, intravenously administered NMN and NR were rapidly degraded into nicotinamide and secreted to bile followed by deamidation to NA by gut microbiota. Thus, enterohepatic circulated NA is preferentially used in the liver. These findings showed that NMN and NR are indirectly converted to NAD+ via unexpected metabolic pathways.
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