Hypothesis: The age-related decline in tissue homeostasis stems not from diminished mitophagy capacity, but from a decoupling of the hierarchical signaling cascade that normally coordinates selective autophagy pathway prioritization. Urolithin A's geroprotective effects may operate by re-synchronizing this hierarchy—specifically restoring the AMPK-mediated energy-sensing cascade that normally prioritizes mitochondrial quality control under metabolic stress. This re-synchronization may be more critical than UA's direct PINK1/Parkin upregulation.

Mechanistic rationale: The research demonstrates that selective autophagy pathways compete for limited Atg machinery, suggesting the cell operates a resource allocation algorithm. The finding that inflammation induces maladaptive ER-phagy prioritization indicates this hierarchy is physiologically regulated rather than passively determined. We propose that aging desynchronizes the energy-sensing kinases (AMPK, mTOR) from their downstream autophagy receptor selectivity, causing inappropriate pathway activation regardless of cellular context. Urolithin A's simultaneous AMPK activation and mTOR inhibition may rebuild the temporal coupling between metabolic state detection and autophagic substrate selection.

Testable predictions: First, in aged primary cells, we'd measure the phase-locking between AMPK activation peaks and Parkin mitochondrial recruitment—predicting desynchronization that UA treatment rescues. Second, comparing autophagic flux across multiple pathways (mitophagy, ER-phagy, pexophagy) in young versus old tissue with and without UA would reveal whether pathway coordination ratios normalize rather than just singular mitophagy enhancement. Third, engineered uncoupling of AMPK-Parkin signaling should abolish UA's benefits despite preserved general autophagy induction, confirming hierarchical restoration rather than pathway bias as the mechanism.

Falsifiability: If UA benefits persist after genetic disruption of AMPK-Parkin coupling while general autophagy induction remains intact, the hypothesis is falsified.