NAD+ — WHAT DOES IT DO?
NAD+ helps cells transfer electrons during fuel metabolism. It also supplies enzymes that respond to DNA damage and regulate protein activity. Cells need it for both energy production and maintenance.
Moves energy through the cell
NAD+ accepts electrons and becomes NADH. In mitochondria, NADH supplies electrons to the respiratory chain that supports ATP production. [1]
Supports mitochondrial metabolism
The transporter SLC25A51 brings NAD+ into mitochondria. Removing it reduced mitochondrial NAD+ and impaired respiration in cell experiments. [1]
Supplies DNA-repair enzymes
PARP enzymes consume NAD+ to attach ADP-ribose signals to proteins. Cell experiments linked NAD+ availability to recruitment of DNA-repair proteins. [2]
Supplies sirtuin enzymes
Sirtuins use NAD+ to modify proteins. SIRT6 research connected its activity with PARP1 activation and repair of DNA breaks under stress. [3]
How NAD+ availability connects mitochondrial energy production with DNA repair and protein regulation.
What is NAD+?
NAD+ stands for nicotinamide adenine dinucleotide. It is a coenzyme found in cells, rather than a peptide. NAD+ and its reduced form, NADH, form an electron-transfer pair used in metabolism. Enzymes such as PARPs and sirtuins also use NAD+ as a chemical substrate. [1][2][3]
Understanding the cellular focus.
NAD+ pools are organized within different cellular compartments. Whole-cell NAD+ measurements do not necessarily describe what is happening inside mitochondria. The SLC25A51 study directly demonstrates why transport and location matter. [1]
What the studies found.
Selected original papers connect the mechanisms with measured findings. Open each source for its full methods and results.
SLC25A51 is a mammalian mitochondrial NAD+ transporter
Identified SLC25A51 as a transporter for intact NAD+ into mammalian mitochondria. Loss of this protein lowered mitochondrial NAD+ and impaired respiration, while whole-cell NAD+ did not show the same decrease.
Read original source ↗Extracellular NAD+ enhances PARP-dependent DNA repair capacity independently of CD73 activity
Lower NAD+ reduced recruitment of the repair protein XRCC1 and impaired repair of experimentally induced DNA damage. NAD+ or NMN supplementation reversed these effects in the tested cell systems.
Read original source ↗SIRT6 promotes DNA repair under stress by activating PARP1
Linked SIRT6 to PARP1 activation and enhanced repair of DNA double-strand breaks under oxidative stress. This is evidence about a NAD+-dependent pathway, not a trial of a NAD+ product.
Read original source ↗A Pilot Study Investigating Changes in the Human Plasma and Urine NAD+ Metabolome During a 6 Hour Intravenous Infusion of NAD
The pilot followed plasma and urine metabolites in eight participants receiving NAD+ and three controls. It observed time-dependent metabolic changes and urinary excretion, rather than testing aging reversal or disease treatment.
Read original source ↗Human findings in context.
The 2019 pilot measured what happened to circulating NAD+ and related metabolites during a six-hour infusion. It contributes human metabolism data, but did not test physical performance, longer life, or an aging outcome. Trials of NAD+ precursors such as NR or NMN study different compounds and should be identified separately. [4]
What the findings tell us.
NAD+ is essential to cell biology; that does not mean more NAD+ always produces a better result. The cell type, compartment, baseline state, and assay determine how a change in NAD+ should be interpreted.
A closer look at the evidence.
What does NAD+ do inside mitochondria?
It participates in reactions that convert nutrients into usable energy. Its reduced partner, NADH, carries electrons toward the respiratory chain. SLC25A51 helps maintain the mitochondrial NAD+ pool. [1]
How is NAD+ connected to DNA repair?
PARPs use NAD+ to generate signals associated with DNA-damage responses. Experiments found that NAD+ depletion impaired repair-protein recruitment and DNA repair, with recovery after replenishment in the tested cells. [2]