Fig. 1. Biosynthesis and depletion processes of nicotinamide mononucleotide (NMN). CD38: cluster of differentiation 38; NAD⁺: nicotinamide adenine dinucleotide; NAM: nicotinamide; NAMPT: nicotinamide phosphoribosyltransferase; NMNAT: nicotinamide mononucleotide adenylyl transferase; NR: nicotinamide riboside; NRK: nicotinamide riboside kinase; PARP: poly(adenosine diphosphate (ADP)-ribose) polymerase; SARM1: sterile alpha and Toll/interleukin-1 receptor (TIR) motif-containing protein 1.