Hypothesis

Intermittent rapamycin (5–10 mg weekly) combined with daily NMN (500 mg) will reduce GrimAge and DunedinPACE more than monotherapy after 12 weeks.

Rationale

• Rapamycin inhibits mTORC1, triggering autophagy and improving immune function [4][5].
• NMN raises NAD+, activating SIRT1, which deacetylates mTOR pathway components and enhances mitochondrial health [6].
• Combined mTOR inhibition and SIRT1 activation may synergistically reset epigenetic age markers, an effect not yet shown for either agent alone [1][2][3].

Mechanistic Insight

mTORC1 suppression lowers NF‑κB activity and reduces secretion of senescence‑associated secretory phenotype (SASP) factors, which are linked to methylation changes at GrimAge CpG sites. SIRT1 activation promotes deacetylation of histones and DNA repair enzymes, facilitating active demethylation pathways. Simultaneous mTORC1 inhibition and SIRT1 upregulation creates a metabolic state that favors NAD+-dependent TET enzyme activity, accelerating removal of methyl groups from age‑associated loci. This dual action provides a mechanistic basis for expecting a greater epigenetic age shift than either intervention alone.

Experimental Design

A randomized, double‑blind, crossover trial with 60 participants aged 60–80.

• Arm A: rapamycin 5 mg weekly + placebo NMN.
• Arm B: placebo rapamycin + NMN 500 mg daily.
• Arm C: rapamycin 5 mg weekly + NMN 500 mg daily.
• Arm D: double placebo. Each period lasts 12 weeks with a 4‑week washout. Primary outcome: change in GrimAge and DunedinPACE from baseline to end of each period. Secondary outcomes: cytokine panel (IL‑6, TNF‑α), lipid profile (LDL, HDL, triglycerides), fasting glucose, insulin, and plasma NAD+ concentration. Statistical plan: paired t‑tests comparing each active arm to placebo within participants; Bonferroni correction for three comparisons. Power analysis assumes a within‑subject standard deviation of 1.2 years for GrimAge; 30 completers per arm give 80% power to detect a 0.8‑year difference at α=0.05.

Predicted Outcomes

• Arm C will show a mean GrimAge drop of ≥1.5 years and DunedinPACE reduction of ≥0.05 units, surpassing the sum of effects seen in Arms A and B.
• Arms A and B will each produce modest, non‑significant changes (≤0.4 years GrimAge change).
• No arm will worsen metabolic markers beyond safety thresholds; transient LDL increase ≤10 % expected with rapamycin but reversible.
• Plasma NAD+ will rise ≥30 % in NMN‑containing arms, confirming target engagement.

Potential Pitfalls

• Variability in epigenetic clock measurements may obscure small effects; using duplicate runs and averaging can reduce noise.
• Rapamycin’s long half‑life may cause carryover; the washout period is based on its ~60‑hour half‑life in elderly.
• Participant adherence to daily NMN will be monitored via pill count and plasma NAD+ levels.
• Potential off‑target effects of high‑dose NMN (e.g., methyl‑group depletion) will be tracked via homocysteine levels.

If the co‑treatment fails to outperform monotherapies, the hypothesis that mTOR‑SIRT1 crosstalk drives reversible epigenetic aging in humans will be falsified.