Hypothesis

Intermittent fasting (IF) reprograms heterogeneous senescent cells into a metabolically uniform state that increases their dependence on BCL‑2 family anti‑apoptotic proteins, thereby sensitizing them to senolytic clearance and lowering inflammaging.

Mechanistic Rationale

Senescent cells display variable SASP composition and differential reliance on survival pathways, which underlies the 30‑70 % clearance ceiling of current senolytics 2. IF activates AMPK and suppresses mTORC1, triggering autophagic flux and reducing mitochondrial ROS production. Lower ROS diminishes oxidative damage to lysosomal membranes, enhancing autophagic degradation of damaged mitochondria and limiting the release of mitochondrial DNA that fuels cGAS‑STING‑NF‑κB signaling. Consequently, the NF‑κB‑driven SASP shifts toward a less heterogeneous, predominantly IL‑6/IL‑8 profile that correlates with heightened BCL‑2 and BCL‑xL expression as a compensatory survival signal.

This metabolic rewiring creates a synthetic lethal context: senescent cells become more vulnerable to BCL‑2 inhibitors (e.g., navitoclax) while retaining their proliferative arrest. Supporting data show that AMPK activation can downregulate MCL‑1, shifting the apoptotic balance toward BCL‑2 dependence 3. IF‑induced NAD⁺ elevation further sustains SIRT1 activity, which deacetylates p53 and promotes a senescent phenotype less reliant on p53‑mediated survival pathways.

Experimental Design

1. Model: Use naturally aged (24‑month) C57BL/6 mice exhibiting elevated p16^Ink4a^‑positive senescent cells in liver and adipose tissue.
2. Groups (n=10 per group):
   • Control ad libitum diet + vehicle
   • IF (16 h fast/8 h feed) + vehicle
   • Ad libitum + navitoclax (50 mg/kg, twice weekly)
   • IF + navitoclax (same dosing)
3. Intervention Duration: 8 weeks.
4. Readouts:
   • Flow cytometry for p16^Ink4a^^+; CD9^+; senescence-associated β‑galactosidase.
   • SASP profiling (IL‑6, IL‑8, MMP‑3) via multiplex ELISA.
   • Tissue inflammaging markers (serum CRP, hepatic NF‑κB p65 nuclear translocation).
   • Autophagic flux (LC3‑II/I ratio, p62 levels) and mitochondrial ROS (MitoSOX).
   • Functional assays: grip strength, glucose tolerance, and cognitive maze performance.
5. Statistical Analysis: Two‑way ANOVA with post‑hoc Tukey test; significance set at p<0.05.

Predicted Outcomes

• IF alone will modestly reduce senescent cell burden (~15‑20 %) via enhanced autophagy.
• Navitoclax alone will replicate the reported 30‑70 % clearance range.
• The IF + navitoclax combination is expected to achieve >85 % reduction in p16^Ink4a^^+ cells across tissues, reflecting overcoming of senolytic resistance.
• SASP heterogeneity will decrease, with a dominant IL‑6/IL‑8 signature and lowered overall SASP intensity.
• Inflammaging biomarkers (serum CRP, hepatic NF‑κB activity) will decline proportionally to senescent cell loss, correlating with improved physical and cognitive function.

Falsifiability

If IF fails to sensitize senescent cells to navitoclax—i.e., the combination does not surpass the clearance achieved by navitoclax alone or does not reduce SASP heterogeneity—the hypothesis is refuted. Similarly, if autophagic inhibition (e.g., chloroquine co‑treatment) abrogates the synergistic effect, the proposed mechanism is challenged.

Implications

Validating this hypothesis would establish a non‑pharmacological senosensitizer that standardizes senescent cell vulnerability, enabling lower doses of BCL‑2‑targeted senolytics and mitigating off‑target toxicity. It also links nutritional interventions directly to the molecular inflammaging axis, offering a translatable strategy for aging‑related therapeutics.