NAD+ (Direct).

Nicotinamide riboside is phosphorylated by NRK1/NRK2 to nicotinamide mononucleotide and then adenylylated to NAD+. It is a direct entry point into the salvage pathway that maintains the NAD+ pool.

NMN sits one enzymatic step from NAD+, converted by the NMNAT enzymes. Supplying it raises the substrate available for that final adenylylation.

Nicotinic acid enters NAD+ synthesis through the Preiss-Handler pathway via nicotinic acid mononucleotide and NAAD. It is a separate on-ramp from the nicotinamide salvage route.

Nicotinamide is recycled to NMN by NAMPT, the rate-limiting salvage enzyme, and then on to NAD+. Most NAD+ turnover in human tissue runs through this loop.

Tryptophan is converted through the kynurenine pathway to quinolinic acid and then to nicotinic acid mononucleotide. It is the only route that builds NAD+ from scratch rather than recycling it.

Excess nicotinamide is cleared by NNMT, which spends a methyl group from S-adenosylmethionine on each molecule. Betaine remethylates homocysteine back to methionine and helps keep that methyl pool stocked.

The same NNMT methylation draw is served by folate-dependent remethylation of homocysteine. 5-MTHF supplies the methyl group that methionine synthase transfers.

Methionine synthase needs cobalamin to move a methyl group from 5-MTHF to homocysteine. Without it the folate route cannot replenish the methyl pool that nicotinamide clearance draws on.

NADH hands its electrons to complex I, whose prosthetic group is FMN, made from riboflavin. Flavin status sets how fast NADH is reoxidised back to NAD+.

Ubiquinone accepts the electrons complex I strips from NADH. A working CoQ pool is what allows NADH to be turned back into NAD+ during oxidative phosphorylation.

Sirtuins consume NAD+ as a co-substrate for every deacetylation they perform. Resveratrol is studied as a sirtuin modulator, though whether it activates the enzyme directly is still argued.

CD38 is a major NAD+ consuming glycohydrolase in tissue. Apigenin inhibits CD38, which slows the rate at which the NAD+ pool is degraded.

Quercetin is a flavonoid inhibitor of CD38, the same NAD+ consuming enzyme apigenin acts on. Reducing consumption sits alongside raising precursor supply.

NAD+ and NADH are the oxidised and reduced halves of one couple, interconverted by every dehydrogenase in central metabolism. What matters physiologically is the ratio between them, not either alone.

Lipoamide is the swinging arm in the pyruvate and alpha-ketoglutarate dehydrogenase complexes, and the E3 subunit regenerates it by reducing NAD+ to NADH. The two work in one catalytic cycle.

Sirtuin enzymes consume NAD+ as a co-substrate when they deacetylate their targets, so sirtuin activity and NAD+ availability sit on the same pathway. Pterostilbene is studied as a sirtuin-directed polyphenol and is commonly formulated alongside NAD+ precursors for that reason. The pairing is mechanistic and preclinical rather than a demonstrated clinical additive effect.

Spermidine is studied for its effect on autophagy signalling, a process that intersects with NAD+ dependent deacetylases in the same regulatory network. Both are marketed for cellular maintenance and are often stacked on that shared rationale. No human combination trial establishes an additive effect, so read the pairing as mechanistic.

Urolithin A is studied for mitophagy signalling while NAD+ is the electron acceptor that keeps mitochondrial dehydrogenases turning over. The two act at different points of mitochondrial housekeeping rather than on the same enzyme. Any combined effect in people has not been measured.

Magnesium is the counter-ion for ATP and a required cofactor for the kinases and adenylyltransferases that build and use nucleotides, including the salvage steps that regenerate NAD+. Without adequate magnesium those phosphotransfer reactions run poorly regardless of NAD+ supply. This is settled biochemistry rather than a combination trial result.

The body can make NAD+ from tryptophan through the kynurenine route, and kynureninase in that route is a pyridoxal-5-phosphate enzyme. Low B6 status slows the conversion so more of the requirement falls on preformed niacin equivalents. The relationship is a textbook cofactor dependency.

Thiamine pyrophosphate drives the pyruvate and alpha-ketoglutarate dehydrogenase complexes, and both of those complexes reduce NAD+ to NADH as they run. Adequate thiamine is therefore part of what makes NAD+ useful as an electron acceptor in normal energy metabolism. This is a shared-pathway relationship, not a demonstrated clinical stack.

Pantothenic acid becomes coenzyme A, the carrier that delivers acetyl groups into the citric acid cycle where NAD+ picks up the electrons. The two cofactors work in series on the same fuel-oxidation route. Neither substitutes for the other.

Semidehydroascorbate reductase uses reduced pyridine nucleotide to regenerate ascorbate after it has donated an electron, which links vitamin C recycling to cellular NAD+ and NADH balance. Ascorbate status therefore sits downstream of the same redox pool. The link is enzymatic rather than an outcome measured in a combination trial.

Cysteine is the rate-limiting building block for glutathione, and glutathione is returned to its reduced form by a reductase that runs on the phosphorylated form of the same pyridine nucleotide pool. Cysteine supply and nucleotide redox status therefore constrain each other. Read it as mechanistic biochemistry.

Glutathione reductase regenerates reduced glutathione using NADPH, which cells make from the NAD+ pool through the pentose phosphate route and nucleotide kinases. Antioxidant capacity is thus tied to nucleotide availability. This describes a cofactor chain, not a measured clinical benefit of taking both.

Alcohol dehydrogenase and several other NAD+ dependent dehydrogenases are zinc metalloenzymes that need the metal in the catalytic site to transfer hydride to the nucleotide. Zinc status therefore shapes how much of the NAD+ pool can be used by those enzymes. Standard enzymology, no trial needed.

Copper sits in cytochrome c oxidase at the end of the electron transport chain, the step that ultimately allows NADH to be reoxidised back to NAD+. If terminal oxidation stalls, the NAD+ to NADH ratio shifts. The two nutrients act at opposite ends of the same electron route.

Iron-sulfur clusters in complex I accept electrons directly from NADH, so iron status is part of what determines how quickly NADH is turned back into NAD+. Both nutrients are needed for normal mitochondrial electron flow. This is a pathway relationship rather than an absorption interaction.

Creatine buffers ATP by phosphate transfer while NAD+ supports the dehydrogenase steps that generate ATP in the first place, so the two support cellular energy handling at different stages. They are frequently combined on that logic. No trial has measured the pair together in people.

Carnitine carries long-chain fatty acids into the mitochondrion, and each round of beta-oxidation there reduces NAD+ to NADH. Fatty acid oxidation therefore consumes the NAD+ pool as a normal part of energy production. The relationship is stoichiometric biochemistry.