NAD+

NAD+ is a critical coenzyme found in all living cells, serving as a central mediator of energy metabolism and a key substrate for enzymes involved in DNA repair, gene expression, and cellular stress response. Its systemic levels decline significantly with age, making it a major focus of longevity research.

NAD+ functions as an electron carrier in the mitochondrial electron transport chain, accepting electrons from NADH to generate ATP via oxidative phosphorylation. Beyond energy metabolism, NAD+ is the sole substrate for sirtuin deacetylases (SIRT1–SIRT7) and PARPs, which regulate chromatin structure, DNA damage repair, and inflammatory signaling.