NAD+

NAD+ (Nicotinamide adenine dinucleotide, oxidised form) is a dinucleotide coenzyme central to cellular energy metabolism, sirtuin-mediated gene regulation, PARP-mediated DNA damage repair, and calcium signalling through CD38-generated cyclic ADP-ribose. NAD+ participates in over 500 enzymatic reactions, alternating between its oxidised (NAD+) and reduced (NADH) forms as a hydride carrier in the oxidative metabolic reactions that drive mitochondrial electron transport and ATP synthesis.

The NAD+ research field has been transformed by the discovery that intracellular NAD+ levels decline with age — approximately 50% reduction between young adult and aged tissue in published rodent studies, with similar trends in human cross-sectional analyses. This decline reduces the activity of all NAD+-dependent enzymes: seven sirtuins (SIRT1-7), 17 PARP isoforms, and CD38/BST1. The sirtuin family is most studied in the context of NAD+ biology — SIRT1 deacetylates PGC-1alpha (activating mitochondrial biogenesis), FOXO transcription factors (stress response activation), NFkB (anti-inflammatory), and p53 (reduced apoptosis sensitivity); SIRT3 deacetylates multiple mitochondrial metabolic enzymes (IDH2, SOD2, LCAD, NDUFA9) connecting NAD+ availability to mitochondrial oxidative metabolism efficiency.

PARP1 is the primary NAD+ consumer during DNA damage: each ADP-ribosylation event on DNA repair proteins consumes one NAD+ molecule, and severe damage triggers massive PARP1 hyperactivation that can deplete cellular NAD+ to levels causing energy failure (parthanatos). Research examining the NAD+-PARP axis uses PARP inhibitors (olaparib, niraparib) to prevent NAD+ consumption and quantify how much of the NAD+ pool is consumed by basal versus damage-induced PARP activity.

The NAD+ salvage pathway maintains intracellular NAD+ through recycling of nicotinamide released by sirtuin and PARP reactions. NAMPT (nicotinamide phosphoribosyltransferase) — the rate-limiting salvage enzyme — converts nicotinamide to NMN, which NMNAT enzymes convert to NAD+. NNMT (nicotinamide N-methyltransferase, inhibited by 5-Amino-1MQ) competes with NAMPT for nicotinamide, diverting it away from NAD+ salvage. The NNMT-NAMPT competition establishes the mechanistic connection between 5-Amino-1MQ and NAD+ research tools.

CD38 expression increases with age and inflammation, becoming a dominant NAD+ hydrolase in aged tissues and driving much of the age-related NAD+ decline (Camacho-Pereira et al., Cell Metabolism, 2016). CD38 knockout mice maintain higher NAD+ and show metabolic advantages in ageing, establishing CD38 as a therapeutic target for age-related NAD+ decline. Research using exogenous NAD+ alongside CD38 inhibitors (78c, apigenin) allows quantification of CD38-mediated consumption versus salvage pathway contributions to cellular NAD+ dynamics.

Exogenous NAD+ is membrane-impermeant under normal conditions — the charged dinucleotide does not passively cross lipid bilayers. Extracellular NAD+ research examines its effects through: CD38/CD157 ectonucleotidase-mediated metabolism on cell surfaces; P2Y11 and P2X7 purinergic receptor activation; and generation of cell-permeant ADP-ribose and cADPR downstream of CD38. For direct intracellular NAD+ supplementation, NMN or NR are cell-permeant precursors typically preferred over NAD+ itself.

MW: 663.43 g/mol. CAS: 53-84-9. Highly hygroscopic — store sealed at -20°C; equilibrate to room temperature before opening. Reconstitute in sterile water at 100mM stock. For laboratory and analytical research purposes only.

NAD+ measurement methodology: for intracellular NAD+ quantification in research models treated with exogenous NAD+ or NAD+ pathway modulators, use the enzymatic cycling assay (NAD+ converted to NADH by alcohol dehydrogenase, then NADH quantified by thiazolyl blue reduction) or bioluminescent NAD+/NADH-Glo kit (Promega). For cellular NAD+/NADH ratio, use the SoNar or Peredox genetically encoded fluorescent biosensors in transfected cells, enabling real-time NAD+ redox state monitoring by confocal imaging. CD38 inhibitor controls: apigenin (50uM) or compound 78c selectively inhibit CD38 ectoenzyme activity, allowing quantification of CD38's contribution to NAD+ hydrolysis in any given cell model. MW: 663.43 g/mol. CAS: 53-84-9. Highly hygroscopic — equilibrate sealed vial to room temperature before opening. Reconstitute in sterile water at 100mM. For laboratory and analytical research purposes only.