NAD+ and Sirtuins

What sirtuins are

Sirtuins are a family of seven enzymes in mammals (SIRT1 through SIRT7) that require NAD+ as a cofactor to modify other proteins — mainly by removing acetyl or related chemical groups from them, a process called deacetylation.[1] Because they need NAD+ to function, sirtuin activity is sensitive to how much NAD+ is available in the specific cellular compartment where each sirtuin operates. The seven sirtuins are involved in a wide range of processes: energy metabolism, mitochondrial function, cellular stress responses, chromatin regulation, and genomic stability, distributed across different cellular locations — for example SIRT1 mainly in the nucleus and cytoplasm, SIRT3 inside mitochondria.[1] This dependence on NAD+ as a required cofactor is well-established, direct enzymology, not a contested claim.

Sirtuins, mouse lifespan, and why the framing matters

Sirtuins are widely nicknamed "longevity genes" or "anti-aging enzymes" in popular writing, a shorthand rooted in real but specific research findings. In mice, overexpressing extra copies of SIRT6 extended lifespan in males,[2] and mice engineered to overexpress SIRT1 specifically in the brain also showed extended lifespan and delayed signs of aging.[3] These are genuine, published, peer-reviewed findings — but they are mouse genetic-engineering studies, not evidence about what happens when a human takes an NAD+ precursor supplement. Overexpressing a gene throughout an animal's life from early development is a fundamentally different intervention from an adult human raising blood NAD+ levels with an oral supplement, and no human study has replicated a lifespan effect from either approach — nor could a human lifespan-extension trial be practically run on a timescale that would produce that kind of evidence.

Why "longevity genes" and "activates longevity pathways" oversimplify

Calling sirtuins "longevity genes" compresses a genuinely complicated, still-developing area of biology into a label that implies more certainty than the evidence supports, especially when it's used to describe what a supplement does in a person. Sirtuins are real, NAD+-dependent enzymes with well-documented roles in cellular processes connected to metabolism and stress resistance in laboratory models — that part is established. Whether raising NAD+ levels in a healthy adult human via NMN supplementation "activates longevity pathways" in any way that changes human healthspan or lifespan has not been demonstrated, and this hub avoids that phrase for that reason.

What human NMN trials actually show about sirtuins

No human NMN trial referenced on this hub has directly measured sirtuin activity, sirtuin-dependent gene expression, or a validated marker of sirtuin engagement in participants — trial outcomes have instead measured things like blood NAD+ levels, walking distance, insulin sensitivity, and self-reported wellbeing, detailed on NMN Dosage. A rise in blood NAD+ is consistent with more substrate being available for sirtuins to use, but it is not the same as direct evidence that sirtuin activity actually increased in a person, or that any such increase produced a health benefit.

Related reading

For the enzymes that produce the NAD+ sirtuins depend on, see The NAD+ Salvage Pathway. For other major NAD+-consuming enzyme families, see NAD+ and PARPs and NAD+ and CD38.