NAD+ (nicotinamide adenine dinucleotide) is an essential cellular coenzyme that participates in oxidation-reduction reactions and serves as a substrate or co-substrate for numerous signaling enzymes. It plays an important role in metabolic pathways including glycolysis, the tricarboxylic acid cycle, fatty-acid oxidation, and mitochondrial energy metabolism.

Research has also examined NAD+ in relation to sirtuin activity, PARP-mediated processes, DNA repair, cellular stress responses, mitochondrial function, and regulation of cellular redox balance. NAD+ exists in dynamic equilibrium with its reduced form, NADH, allowing cells to transfer and manage reducing equivalents during metabolic reactions.

NAD+ remains an active area of laboratory and translational research, particularly in studies investigating cellular metabolism, aging biology, mitochondrial processes, and NAD+ homeostasis. The biological effects of manipulating NAD+ levels remain an evolving area of research.