Hypothesis: BMAL1‑TFEB Axis Links Circadian Timing to Lysosomal Clearance and Senescence Suppression

Core idea: The circadian transcription factor BMAL1 directly drives expression of the lysosomal biogenesis regulator TFEB, linking circadian amplitude to autophagic clearance of damaged proteins and organelles. When circadian rhythms weaken, TFEB activity falls, lysosomal function declines, and senescent cells accumulate due to impaired clearance. Restoring TFEB activity through timed NAD+ precursors rescues lysosomal function and reduces senescence independent of global rhythm amplitude.

Testable predictions

1. In young Bmal1‑deficient mice, hepatic TFEB mRNA and protein levels will be reduced despite normal feeding cycles.
2. Pharmacological activation of TFEB (e.g., with timed nicotinamide riboside) will restore lysosomal markers (LAMP1, Cathepsin B) and lower p21^Waf1^/SASP in Bmal1‑KO tissues.
3. Genetic ablation of TFEB will block the senolytic effect of timed melatonin or exercise in aged wild‑type mice, proving TFEB is downstream of the circadian anti‑aging firewall.
4. Overexpressing TFEB in senescent human fibroblasts will decrease SASP secretion and increase autophagic flux, even when core clock genes are silenced by siRNA.

Experimental approach

• Use liver‑specific Bmal1 floxed mice crossed with TFEB luciferase reporters to monitor circadian TFEB activity.
• Treat groups with timed NAD+ supplementation (ZT0) vs. constant dosing; measure lysosomal mass (LysoTracker), autophagic flux (LC3‑II turnover), senescence (SA‑β‑gal, p16^Ink4a^), and SASP (IL‑6, MCP‑1) by ELISA.
• Include TFEB knockout or siRNA controls to test necessity.
• Validate in primary human fibroblasts transfected with BMAL1 siRNA and treated with timed NR; assess TFEB nuclear translocation, lysosomal function, and SASP.

Falsifiability: If timed NAD+ fails to improve lysosomal markers or reduce senescence in Bmal1‑deficient contexts, or if TFEB loss does not abolish the protective effect of circadian interventions, the hypothesis is refuted.

Potential impact: Positions TFEB as a circadian‑gated effector of the anti‑aging firewall, suggesting that chronopharmacological targeting of lysosomal biogenesis could complement or replace broad clock‑modulating strategies.