Hypothesis

Intermittent low-dose rapamycin (3-10 mg weekly) enhances the gut microbial conversion of NMN or NR to nicotinic acid, leading to greater and more sustained NAD+ accumulation in peripheral tissues such as skeletal muscle and brain compared to NAD+ precursor supplementation alone.

Rationale

Recent human trials show NMN and NR (1 g daily) double circulating NAD+ after 14 days via gut microbiota conversion to nicotinic acid, which also raises short‑chain fatty acids with anti‑inflammatory effects Scientists Unveil Results from Human Trial. However, tissue‑specific NAD+ increases remain inconsistent, especially in brain and muscle Clinical evidence for the use of NAD+ precursors. Rapamycin at low intermittent doses inhibits mTORC1, alters gut microbiome composition, and can increase microbial enzyme activity that favors nicotinic acid production Rapamycin Dosing for Longevity. Combining rapamycin with NAD+ precursors may therefore synergize to raise tissue NAD+ where precursor alone fails.

Predictions

1. Participants receiving rapamycin plus NMN (1 g/day) will show a significantly larger increase in muscle NAD+ (measured by ^31P‑MRS) and cerebral NAD+ (estimated via PET with NAD+-specific tracer) after 28 days than those receiving NMN alone or rapamycin alone.
2. The increase in tissue NAD+ will correlate with a reduction in biological age acceleration as measured by the MOMAC AI clock or other multi‑omic deep learning biological age models Development and validation of deep learning-based biological ages.
3. The combined regimen will not increase immunosuppression markers (e.g., CD4+ count, infection incidence) beyond baseline, confirming safety of low‑dose intermittent rapamycin.

Experimental Design

A randomized, double‑blind, 2×2 factorial trial in 120 healthy adults aged 50‑70: Factor A (rapamycin: 5 mg weekly vs placebo), Factor A (NAD+ precursor: NMN 1 g/day vs placebo). Primary outcomes: change in muscle NAD+ (MRS) and brain NAD+ (PET) at day 28. Secondary outcomes: circulating NAD+, SCFA levels, immune cell phenotypes, and change in multi‑omic biological age (Delta Age = biological age – chronological age) at baseline and day 28.

Potential Outcomes

If the hypothesis is correct, the rapamycin+NMN arm will show additive NAD+ elevation in tissue and a measurable slowing of biological age acceleration. Failure to observe increased tissue NAD+ or age‑metric improvement would falsify the hypothesis, suggesting that rapamycin does not enhance microbial conversion or that tissue NAD+ bioavailability is limited by other factors.

References

[1] Scientists Unveil Results from Human Trial https://www.nmn.com/news/scientists-unveil-results-from-human-trial-directly-comparing-three-nad-precursors [2] Clinical evidence for the use of NAD+ precursors https://sciexplor.com/articles/Geromedicine.2025.0008 [3] Rapamycin Dosing for Longevity https://www.gethealthspan.com/research/article/rapamycin-dosing-for-longevity [4] Development and validation of deep learning-based biological ages https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2025.1532884/full