Hypothesis

Combining daily NMNH (500 mg) with intermittent low-dose rapamycin (5 mg once weekly) will produce a greater reduction in LinAge2 after 12 weeks than either intervention alone, driven by synergistic increases in tissue NAD+ and SCFA production that attenuate mTORC1 signaling in immune cells.

Rationale

• NMNH reliably triples circulating NAD+ in adults aged 40‑65 over 90 days 2. Recent work shows gut Enterocloster aldensis converts NMN/NR to nicotinic acid, the actual NAD+ precursor, while raising beneficial SCFAs 1. This microbial conversion sustains NAD+ elevation and may modulate host metabolism.
• Low‑dose rapamycin inhibits mTORC1, a pathway that consumes NAD+ and promotes inflammaging. Pulse dosing (5 mg weekly) is hypothesized to improve immune metabolic flexibility without causing chronic immunosuppression, though human dose‑response data are lacking.
• LinAge2 outperforms epigenetic clocks in predicting mortality, gait speed and functional independence by integrating clinical proteomic markers that reflect metabolic syndrome 5. Because LinAge2 captures modifiable drivers such as NAD+-dependent sirtuin activity and mTORC1‑related phosphoproteins, it should be sensitive to combined NAD+ augmentation and mTORC1 inhibition.

Prediction

Participants receiving NMNH + rapamycin will show a mean LinAge2 reduction of ≥1.5 years after 12 weeks, whereas NMNH alone or rapamycin alone will each yield ≤0.8 year reduction. The combined group will also exhibit higher fecal butyrate levels and increased peripheral blood NAD+/NADH ratio compared with monotherapies.

Testable Design

A randomized, double‑blind, 4‑arm parallel trial (n=40 per arm) in healthy adults aged 45‑65:

1. Placebo
2. NMNH 500 mg daily
3. Rapamycin 5 mg oral once weekly
4. NMNH 500 mg daily + rapamycin 5 mg weekly Primary outcome: change in LinAge2 from baseline to week 12. Secondary outcomes: fasting NAD+ metabolites, fecal SCFA concentrations, circulating inflammatory cytokines (IL‑6, TNF‑α), and mTORC1 activity measured by phospho‑S6K in PBMCs.

Falsifiability

If the combination arm does not produce a statistically significant greater LinAge2 improvement than the best monotherapy (p > 0.05, effect size <0.3), the hypothesis is falsified. Likewise, if NAD+ or SCFA changes do not correlate with LinAge2 shifts, the proposed mechanistic link is unsupported.

Mechanistic Insight

We propose that microbiota‑derived nicotinic acid from NMNH supplementation raises hepatic NAD+, enhancing SIRT1‑dependent deacetylation of LKB1, which subsequently activates AMPK. AMPK activation suppresses mTORC1 signaling, an effect amplified by weekly rapamycin pulses that prevent feedback activation of AKT. The resulting dual inhibition of mTORC1 reduces NF‑κB‑driven inflammation and improves proteostatic markers captured by LinAge2, providing a causal pathway rather than mere correlation.