Longevity & aging

NAD+

A coenzyme present in every living cell, central to energy metabolism.

About

Nicotinamide adenine dinucleotide is not a peptide but a coenzyme, present in every living cell and required for a large number of enzymatic reactions. It is included here because it appears throughout longevity and metabolic research and is frequently discussed alongside the peptides in this catalogue. Cellular concentrations of NAD+ decline with age, an observation that motivates much of the current research interest.

Mechanism

NAD+ functions as an electron carrier in redox reactions, cycling between its oxidised and reduced forms during glycolysis, the citric acid cycle and oxidative phosphorylation. Beyond that metabolic role, it is a required substrate for sirtuins and for PARP enzymes involved in DNA repair — consuming reactions that link its availability to processes studied in the ageing literature. Because NAD+ is consumed rather than merely recycled by these enzymes, its cellular pool depends on continuous synthesis through salvage pathways.

What research has examined

Research has examined NAD+ metabolism in mitochondrial function, DNA repair and sirtuin-dependent signalling.