Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) are biosynthetic precursors to an essential molecule for metabolism– nicotinamide adenine dinucleotide (NAD+).
Numerous studies indicate NAD+ levels decrease significantly during aging, with restoration of NAD+ levels in aged animals extending lifespan and promoting health. Research on the two molecules indicates supplementation with either increases NAD+ levels during aging.
The molecular structures of NMN and NR are roughly the same, except NMN has an added phosphate group. This added phosphate group makes NMN a larger molecule than NR. Some scientists believe NMN is too large to cross cellular membranes and must convert to NR before entering cells, where NAD+ biosynthesis occurs. Otherwise, NMN would need to get transported into cells by a transporter specific for NMN, such as Slc12a8.
Genomics data, which analyzes entire gene sets of humans, indicate the gene encoding this transporter exists in humans. The question is whether the transporter gets expressed in humans similar to mice, thus allowing NMN transport across the cell membrane. According to a genomics database, which examines entire gene sets of humans, SLC12A8 is expressed in humans “…with highest levels in small intestine, stomach, testis, thyroid, and colon.” Thus, the possibility exists this NMN-specific transporter is expressed similarly in the gut of humans and has a similar role in NMN absorption as well.
Confirming this NMN-specific transporter’s expression pattern in the gut of humans will require further research. If studies confirm a similar expression pattern of this transporter for NMN between mice and humans, the possibility remains NMN constitutes the more efficient and effective precursor compared to NR.
NMN vs NR: The Differences Between These 2 NAD+ Precursors. Nmn.com. (2022). Retrieved 29 June 2022, from https://www.nmn.com/precursors/nmn-vs-nr.