Glossary
NAD+
NAD+ is a redox cofactor that sirtuins, PARPs and CD38 also consume as a substrate. What that dual role means for metabolic models and lab handling.
NAD+ — the oxidised form of nicotinamide adenine dinucleotide — is a small dinucleotide cofactor present in all cells. As the NAD+/NADH pair it carries electrons through glycolysis, the tricarboxylic acid pathway and oxidative phosphorylation. Unlike a conventional catalytic cofactor, however, NAD+ is also used up: sirtuins, PARP enzymes and the ectoenzyme CD38 break its glycosidic bond, liberate nicotinamide and put the ADP-ribose part to work in protein deacylation, DNA-damage signalling or calcium signalling.
Its place in metabolic research
Since NAD+ is consumed and not simply recycled, the intracellular level of NAD+ is treated as a rate-limiting factor in metabolism and ageing models. Rodent work published from about 2013 described falling tissue NAD+ with age and changes in sirtuin-dependent measures when precursors were given; human evidence is much more limited and consists mainly of biomarker endpoints, not outcomes. That is why catalogues place NAD+ beside its precursor NMN and beside mitochondrial-derived peptides investigated on related mitochondrial endpoints.
It is handled differently from a peptide: NAD+ attracts moisture and breaks down in water much more quickly than a freeze-dried peptide, so research protocols usually call for aqueous working solutions to be made up fresh, kept chilled and shielded from alkaline pH.
Related terms and material
AMPK · senolytic · in vitro. Reference material: NAD+ and the NAD+ & glutathione collection. Further reading: NAD+ vs NMN.