Hypothesis

Combining intermittent senolytic dosing with low-dose metabolic modulators (rapamycin or metformin) will prevent senescence rebound by simultaneously clearing existing senescent cells and suppressing de novo senescence through mTOR/AKT pathway inhibition and enhanced autophagy.

Rationale

• Senolytics like D+Q clear existing senescent cells but do not block the drivers of new senescence, leading to rebound (Targeting Cellular Senescence for Healthy Aging).
• Metabolic modulators inhibit mTOR (rapamycin) or activate AMPK (metformin), reducing SASP production and promoting autophagic clearance of damaged organelles, thereby lowering the stress that induces de novo senescence (Targeting Cellular Senescence for Healthy Aging; Development and Application of a Senolytic Predictor).
• Low-dose regimens avoid the toxicity of chronic mTOR inhibition while retaining enough pathway suppression to blunt paracrine senescence signals.

Experimental Design

1. Animal model: 20‑month-old C57BL/6 mice, n=10 per group.
2. Groups: (a) Vehicle control, (b) Intermittent D+Q (5 mg/kg dasatinib + 50 mg/kg quercetin, 1 day/week), (c) Low-dose rapamycin (0.5 mg/kg food, continuous), (d) D+Q + low-dose rapamycin, (e) D+Q + low-dose metformin (200 mg/kg drinking water).
3. Duration: 6 months.
4. Readouts:
   • Senescent cell burden (p16^Ink4a^+ and SA-β-gal) in liver, kidney, and muscle at months 0, 3, 6.
   • SASP cytokines (IL-6, IL-8, MMP-3) in plasma via ELISA.
   • Autophagic flux (LC3-II/I, p62) in tissue lysates.
   • Functional assays: grip strength, treadmill endurance, and frailty index.
5. Predictions:
   • Groups receiving D+Q alone will show initial senescent cell reduction at month 1 followed by rebound to baseline by month 6.
   • Groups receiving D+Q plus metabolic modulator will maintain ≥50% lower senescent cell burden throughout, with attenuated SASP and enhanced autophagy markers.
   • Functional improvements will be significantly greater in combination groups vs D+Q alone (p<0.05, ANOVA with post‑hoc Tukey).

Falsifiability

If the combination does not suppress senescence rebound—i.e., senescent cell levels and SASP return to control levels despite metabolic modulator co‑administration—the hypothesis is falsified. Conversely, a sustained reduction supports the mechanistic claim that metabolic suppression of de novo senescence complements senolytic clearance.

Potential Mechanistic Insight

Metabolic modulators may lower mitochondrial ROS and inhibit the cGAS‑STING pathway triggered by cytosolic DNA from stressed cells, a known upstream activator of the senescence program. By dampening this stress‑sensing axis, the tissue microenvironment becomes less permissive for newly senescent cells to emerge after senolytic‑mediated clearance.