Synchronizing mTOR Oscillations via Time-Restricted Feeding to Enhance Senolytic Efficacy: A Testable Hypothesis

Hypothesis: Daily cycles of time-restricted feeding (TRF) generate predictable oscillations in mTORC1 activity that transiently sensitize senescent cells to senolytic drugs by priming lysosomal pathways. When senolytics such as dasatinib plus quercetin (D+Q) are administered during the trough of mTORC1 activity, lysosomal permeabilization and cathepsin release are amplified, leading to selective synthetic lethality in SASP‑high cells. This mechanistic sync predicts that aligning senolytic dosing with the circadian nadir of mTOR signaling will yield greater senescent cell clearance and downstream healthspan benefits than either intervention alone or untimed dosing.

Mechanistic rationale: TRF entrains hepatic and peripheral clocks, driving rhythmic expression of REV‑ERBα and BMAL1, which in turn repress and activate mTORC1 signaling (see circadian regulation of metabolism [2]). During the fasting phase, AMPK activation inhibits mTORC1, upregulating TFEB‑dependent lysosomal biogenesis and autophagy flux. Senescent cells exhibit heightened lysosomal dependence for survival due to increased catabolic load of SASP components. Pharmacologic senolytics induce lysosomal membrane permeabilization; a primed lysosomal state lowers the threshold for cathepsin‑mediated apoptosis. Thus, the temporal window of low mTORC1/high lysosomal activity creates a synthetic lethal senescent‑cell vulnerability that is absent during the fed, mTORC1‑high phase.

Experimental design: Use aged (20‑month) C57BL/6 mice implanted with subcutaneous osmotic pumps delivering D+Q or vehicle. Mice are assigned to four groups (n=15 per group): (1) ad libitum feeding + vehicle, (2) ad libitum feeding + D+Q given at ZT6 (mid‑active phase), (3) TRF (8‑hour feeding window aligned to dark phase) + vehicle, (4) TRF + D+Q administered at ZT2 (2 h after lights‑on, corresponding to the predicted mTORC1 trough). Primary endpoints after 4 weeks: (a) senescent cell burden in adipose, kidney, and brain measured by p16^Ink4a^ immunostaining and SA‑β‑gal activity; (b) SASP cytokine plasma levels (IL‑6, IL‑1β, MMP‑9) via ELISA; (c) functional assays (grip strength, treadmill endurance, spontaneous activity). Secondary endpoints: lysosomal cathepsin B activity in sorted p16^+ cells, TFEB nuclear localization, and mTORC1 readouts (p‑S6K).

Predictions and falsifiability: If the hypothesis is correct, group 4 will show a statistically significant (>30 %) reduction in senescent cell burden and SASP compared with groups 2 and 3, and superior functional improvements. Lack of difference between timed and untimed D+Q under TRF, or absence of enhanced lysosomal markers in senescent cells from group 4, would falsify the mechanistic claim. Additionally, disrupting the clock with Bmal1 knockout in hematopoietic cells should abolish the timing effect, providing a genetic test.

This hypothesis extends the observed independent benefits of senolytics and TRF by proposing a concrete, temporally gated interaction that can be directly tested with existing tools, moving the combinatorial strategy from speculation to a rigorously falsifiable experimental plan.