Novel AMPK/ORP8-lipophagy axis: A therapeutic target for asiaticoside-mediated cardioprotection against ischemia-reperfusion injury in hyperlipidemia

Background: Hyperlipidemia significantly exacerbates myocardial ischemia-reperfusion (I/R) injurfy through lipid metabolic dysfunction and lipotoxicity. Current evidence suggests that lipid droplet accumulation and impaired lipophagy represent critical pathological mechanisms underlying cardiac dysfunction in hyperlipidemic conditions. This study investigated the cardioprotective effects of asiaticoside (AS) against myocardial I/R injury in hyperlipidemic mice and elucidated its underlying mechanisms, emphasizing the AMPK/ORP8-mediated lipophagy pathway.

Methods: Hyperlipidemic C57BL/6 mice were established using high-fat diet feeding and subjected to myocardial I/R injury. Mice received AS (12.5, 25, or 50 mg/kg) treatment for 4 weeks prior to surgery. In vitro experiments involved H9C2 cardiomyocytes treated with palmitic acid followed by hypoxia/reoxygenation. The role of AMPK/ORP8 signaling was evaluated using pharmacological modulators [AMPK Activator (A-769662) and AMPK Inhibitor (Compound C)] and genetic manipulation (ORP8 siRNA knockdown).

Results: AS dose-dependently improved cardiac function parameters, reduced myocardial infarct size (LVEF and LVFS) and decreased triglyceride and cardiac injury biomarkers (cTnI, LDH, CK-MB) in hyperlipidemic I/R mice. Treatment with AS significantly reduced cardiac lipid accumulation and triglyceride content while enhancing lipophagy markers (LC3B-II and Beclin-1) and reducing p62 levels. Mechanistically, AS activated AMPK phosphorylation and upregulated ORP8 expression, which was accompanied by enhanced lipophagy flux. In H9C2 cells, AS protected against palmitic acid-induced lipotoxicity and H/R injury through AMPK/ORP8-dependent lipophagy activation. AMPK inhibition (Compound C) or ORP8 knockdown significantly attenuated AS's protective effects, while AMPK activation (A-769,662) potentiated these benefits, which were reversed to some extent by ORP8 silencing.

Conclusions: This study demonstrates that AS mitigates myocardial I/R injury in hyperlipidemic conditions by promoting lipophagy through the AMPK/ORP8 signaling axis. The AMPK/ORP8-lipophagy pathway represents a novel therapeutic target for metabolic cardiovascular diseases, and AS emerges as a promising cardioprotective agent with significant translational potential.

AMPK/ORP8 signaling pathway; Asiaticoside; Hyperlipidemia; Lipid metabolism; Lipophagy; Myocardial ischemia-reperfusion injury.