Hypothesis

We propose that aging can be tuned by intermittent activation of NAD+-dependent sirtuin pathways during early adulthood, thereby rewiring antagonistic pleiotropy without compromising early-life fitness.

Mechanistic Basis

Antagonistic pleiotropy arises because genes such as mTOR and HIF-1α enhance growth and reproduction early but drive senescence later Antagonistic pleiotropy theory. NAD+ levels decline with age, reducing SIRT1 activity and altering chromatin states that favor expression of late-life deleterious alleles Evolutionary aging review. Early, intermittent NAD+ boosting (e.g., via nicotinamide riboside or exercise) transiently increases SIRT1 deacetylase activity, leading to:

• Increased histone H3K9 acetylation at promoters of growth genes, sustaining their early benefit.
• Enhanced deacetylation of PGC-1α and FOXO factors, promoting stress resistance and attenuating downstream senescence programs.
• A reversible epigenetic 'rheostat' that sets the balance between AP gene expression and somatic maintenance.

Because the intervention is limited to a defined early window, the reproductive advantage remains intact while the epigenetic shift persists, reducing late-life cost.

Testable Predictions

1. In C. elegans, a brief pulse of NAD+ precursor during larval stage L4 will extend mean lifespan by ≥20% without reducing brood size.
2. In mice, intermittent NAD+ supplementation from 8–16 weeks of age will improve late-life healthspan (grip strength, glucose tolerance) while maintaining litter size and growth rate comparable to controls.
3. Chromatin immunoprecipitation sequencing will show increased SIRT1 occupancy at FOXO loci and decreased H3K27ac at mTOR promoters after the pulse, persisting into old age.

Experimental Approach

• Model 1: C. elegans N2 strain; administer NR (50 mM) for 12 h at L4 stage; monitor lifespan, fecundity, and perform ATAC-seq at day 1 and day 10.
• Model 2: C57BL/6 mice; give NR (400 mg/kg diet) intermittently (2 weeks on/2 weeks off) from 8 to 16 weeks; assess reproductive output, body composition, and perform liver ChIP‑seq for SIRT1 and H3K27ac at 6 and 18 months.
• Controls: vehicle-treated littermates; chronic NR exposure group to test fitness cost.

Potential Outcomes and Falsification

• Support: Lifespan/healthspan extension without early‑fitness loss, coupled with predicted epigenetic shifts, would support the rheostat model.
• Falsify: If the NAD+ pulse fails to extend lifespan or reduces brood size/growth, or if no lasting chromatin changes are observed, the hypothesis that early intermittent NAD+ signaling can decouple AP trade‑offs would be refuted.