NAD⁺ is a pyridine nucleotide coenzyme found in all living cells, where it plays a central role in oxidation-reduction (redox) reactions, acting as an electron carrier in metabolic pathways such as glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation. It exists in oxidized (NAD⁺) and reduced (NADH) forms and is essential for ATP production.

Beyond its role in energy metabolism, NAD⁺ is a critical substrate for several enzyme families, including sirtuins, PARPs (poly ADP-ribose polymerases), and CD38, which are involved in DNA repair, gene expression, cellular signaling, and immune responses. Declining levels of NAD⁺ have been associated with aging, neurodegeneration, and metabolic disorders, making it a major focus of longevity and regenerative medicine research.

Studies also explore NAD⁺ supplementation and precursors such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) to restore intracellular NAD⁺ levels and enhance mitochondrial and cellular resilience. Its broad biochemical relevance makes NAD⁺ a cornerstone of research in cell biology, metabolism, and age-related disease.