Loss of Rab8a-Dependent Tethering of Lipid Droplets to Mitochondria Contributes to Hypoxia-Reoxygenation Injury.

Tethering of lipid droplets (LDs) to mitochondria facilitates fatty acid oxidation and is a key adaptive response that helps cardiomyocytes cope with hypoxia-reoxygenation (HR) stress. However, the molecular mechanisms regulating these interactions during ischemia are not fully understood. We found that HR significantly decreased cardiomyocyte expression and phosphorylation of Rab8a, a small GTPase that interacts with the LD-associated protein perilipin 5 to mediate LD-mitochondria tethering. Using long-chain fatty acid (LCFA) tracking assays we confirmed that loss of Rab8a disrupted physical contact between these organelles to impair the transfer of LCFA from LDs to mitochondria. Furthermore, HR led to the accumulation of intracellular lipids via a combination of both lipolysis and lipophagy, resulting in metabolic stress. To counteract this defect, we evaluated the therapeutic potential of ALY688, a peptide agonist of adiponectin receptors known to stimulate the AMPK-Rab8a signaling axis. Our data indicated that treatment with ALY688 preserved Rab8a expression during HR, thereby maintaining LD-mitochondria interactions and improving metabolic function. These findings uncover a novel Rab8a-dependent mechanism regulating lipid metabolism under ischemic/hypoxic stress and highlight the potential of adiponectin mimetics like ALY688 to mitigate metabolic dysfunction in ischemic heart disease.