Hypothesis

Pulsed NMN administration aligned with fasting intervals creates a repeating metabolic cycle: during fasting, NAD+ rises, activating SIRT1, which deacetylates and activates autophagy genes (LC3, ATG5) and indirectly inhibits mTORC1 via AMPK; during refeeding, transient mTORC1 signaling supports protein synthesis and tissue repair without chronic growth signaling. This alternation mimics the proposed civilization‑versus‑survival dial, allowing cells to periodically shift from survival (mTOR low, autophagy high) to growth (mTOR moderate, biosynthesis) while maintaining NAD+‑driven mitochondrial quality control.

Mechanistic Reasoning

• SIRT1 deacetylates TSC2, enhancing its GAP activity toward Rheb, leading to momentary mTORC1 suppression [SIRT1 activates AMPK which in turn inhibits the mTORC1 complex].
• NAD+‑dependent SIRT1 also activates PGC‑1α, driving mitochondrial biogenesis and mitophagy [NMN activates SIRT1/AMPK/PGC-1α to enhance mitochondrial function and protect against neurodegeneration].
• Periodic mTORC1 inhibition permits clearance of damaged organelles, while subsequent refeeding‑driven mTORC1 activity replenishes essential proteins, preventing the deleterious effects of chronic mTOR suppression (e.g., impaired wound healing, immunosuppression).

Testable Predictions

1. In C57BL/6 mice, a regimen of 200 mg/kg NMN given orally every other day, synchronized with 16‑hour fasts, will increase median lifespan by >15% compared with ad libitum fed controls.
2. The same pulsed regimen will improve frailty index, grip strength, and locomotor activity more than continuous NMN or fasting alone.
3. Molecular readouts will show oscillatory p‑S6K (mTORC1 activity) and LC3‑II/autophagosome formation correlating with fasting/refeeding phases, whereas continuous NMN will yield constitutively elevated p‑S6K and blunted autophagic flux.
4. Pharmacologic blockade of SIRT1 (exemestane or SIRT1 inhibitor) will abolish the longevity benefit of pulsed NMN, confirming SIRT1 dependence.

Falsifiability

If pulsed NMN fails to extend lifespan or improve healthspan metrics beyond those seen with continuous NMN or fasting alone, or if mTORC1 activity does not display the predicted oscillatory pattern, the hypothesis is falsified.

References

[1] NMN activates SIRT1/AMPK/PGC-1α to enhance mitochondrial function and protect against neurodegeneration – Front Pharmacol 2025. [link] [2] NMN improved late-life adiposity, metabolic flexibility, and locomotor activity in males but not females – bioRxiv 2024. [link] [3] NMN reverses exercise benefits in obese mice – eLife 2023. [link] [4] Chronic NR supplementation elevates NAD+ in healthy middle-aged and older adults – Nat Commun 2018. [link] [5] Rare mTOR pathway variants are enriched in long-lived individuals – NAD.com article. [link] [6] SRT1720 extends lifespan and improves healthspan in mice – Cell Rep 2014. [link]