The NAD+ Metabolome

What "the NAD+ metabolome" means

Researchers use "NAD+ metabolome" (sometimes "NADome") as a working term for the family of related molecules that make, use, or derive from NAD+ — not a single fixed, universally standardized panel.[1] Different studies measure different subsets of this family depending on their equipment, budget, and question, so a claim about "the NAD+ metabolome" in one paper may cover a different list of molecules than in another. Treat the term as a useful shorthand for a related family of metabolites, not evidence that every study measured the same thing.

What's typically included

Depending on the study, the NAD+ metabolome can include: NAD+ and NADH (the oxidized and reduced forms of the core redox coenzyme, covered in full on NAD+ Redox Biology and the NAD+/NADH Ratio); NADP+ and NADPH (the phosphorylated counterparts used mainly in biosynthesis and antioxidant defense, not interchangeable with NAD+/NADH); the precursors NMN, NR, nicotinamide (NAM), and nicotinic acid; methylated nicotinamide breakdown products such as N-methylnicotinamide (MeNAM) and its further oxidation products 2PY and 4PY; and, where relevant to enzymes that consume NAD+ (covered on NAD+ and CD38 and NAD+ and PARPs), ADP-ribose-related products such as ADP-ribose (ADPR) and cyclic ADP-ribose (cADPR).[1] Not every study measures all of these, and a study that measures only two or three of them is not thereby measuring "the whole metabolome."

How these molecules are actually measured

Modern NAD+ metabolome studies rely on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), a technique that separates molecules by their chemical properties and then identifies and quantifies them by mass — replacing older indirect enzymatic assays that measured a proxy reaction rather than the molecule itself.[2] This matters for interpretation: when a 2021 methodology review compared enzymatic-assay-based NADPH:NADP+ ratios (historically reported around 100) against direct LC-MS measurement of the same ratio in rat tissue (found to be roughly 3.3 or as low as 0.04, depending on tissue), the review concluded that much of the discrepancy in the literature reflects analytical method differences, not true biological variability.[2] A finding of "NAD+ metabolome changed" should always be read alongside which specific method produced it.

Sample type, pre-analytical handling, and degradation

Where a sample comes from matters as much as how it's analyzed. Blood plasma, peripheral blood mononuclear cells (PBMCs), whole blood, skin biopsies, and cerebrospinal fluid have all been used across different NMN studies, and concentrations are not directly comparable across sample types. Handling immediately after collection is unusually important for this metabolite family: enzymatic activity that continues after sample collection can degrade NAD+ to roughly 1% of its true in-life concentration within minutes if extraction doesn't rapidly inactivate those enzymes, while nicotinamide (NAM) levels can simultaneously rise more than tenfold from that same ongoing enzymatic activity.[2] Oxidized forms (NAD+, NADP+) and reduced forms (NADH, NADPH) also have different chemical stability requirements — oxidized forms are more stable under acidic conditions, reduced forms under alkaline conditions — so a single extraction protocol optimized for one can distort measurement of the other.[2] A study that doesn't report its quenching and extraction method should be read with that specific gap in mind.

What has actually been measured after human NMN dosing

Blood or serum NAD+ is the most consistently reported metabolite across published human NMN trials.[3] Beyond NAD+ alone, several individual trials have directly measured additional, specifically named species rather than a generic "metabolome" label: one 14-day dose-response pilot measured intact circulating NMN itself alongside NAD+ and a broader NAD metabolome panel;[4] a 60-day trial measured the NAD+/NADH ratio directly, confirming NADH (not just NAD+) as a reported analyte;[5] a 12-week trial measured serum nicotinamide alongside NAD+ metabolism;[6] and a 14-day, four-arm comparison trial directly measured NAD+, NADH, NADP(H), nicotinamide, nicotinamide riboside, and nicotinic acid together in whole blood.[7] Separately, in a single-dose pharmacokinetic study that did not measure intact NMN itself, the downstream methylated metabolites 2PY and 4PY were the reported analytes.[8] This is not an exhaustive review of every metabolite reported in the full text of every published NMN trial — some trials may report additional analytes in supplementary data not reflected here — but it is enough to show that human NMN research has measured more than blood NAD+ alone, even though NAD+ remains by far the most common single analyte.

Related reading

For what NAD+ itself does, see What Is NAD+? and What Does NAD+ Do?. For how the body makes NAD+, see How the Body Makes NAD+. For what's known about NMN's own path through the body, see NMN Pharmacokinetics, Metabolism, and Bioavailability.