Abstract 12746: Impaired Autophagic Flux in Ischemic/Reperfused Diabetic Heart and Its Reversal by a Novel Orally Active Adiponectin Receptor Agonist via AMPK-Mediated Autophagosome Formation and AMPK-Independent Autophagosome Clearance

Abstract

Autophagy is increasingly recognized as an important regulator of myocardial ischemia/reperfusion (MI/R) injury. However, whether and how autophagy is altered in the ischemic/reperfused diabetic heart remains unknown. Normal control (NC), high-fat-diet-induced diabetic (HFD), and adiponectin (APN) knockout (APNKO) mice were subjected to MI/R (30 minutes/3-24 hours) and treated with vehicle or AdipoRon (50 mg/kg gavage, 10 minutes before MI; or 10 mg/kg IP, 10 min before R). Compared to NC mice, autophagosome formation was significantly inhibited and autophagosome clearance was nearly completely blocked in the HFD heart after MI/R (P<0.01). APNKO largely reproduced the phenotypic alterations observed in the HFD heart, with both autophagosome formation and clearance inhibited after MI/R (P<0.01 vs. WT). Treatment of HFD and APKNO mice with AdipoRon stimulated autophagosome formation, increased autophagosome clearance, reduced infarct size, and improved cardiac function (P<0.01). Mechanistically, AdipoRon caused significant phosphorylation of AMPK, BeclineT119, and VPS34S16, and enhanced expression of lysosome protein LAMP2. Compound C pretreatment abolished AdipoRon-induced BeclineT119 and VPS34S164 phosphorylation without altering AdipoRon-induced LAMP2 expression. In vitro AdipoRon treatment of adult wild type cardiomyocytes enhanced phosphorylation of AMPK, BeclineT119, and VPS34S164. These effects are lost in cardiomyocytes isolated from cardiomyocyte-specific AMPK dominant negative mice (AMPK-DN). In contrast, AdipoRon-stimulated LAMP2 expression was preserved in AMPK-DN cardiomyocytes. Collectively, these results demonstrated for the first time that hypoadiponectinemia during diabetic conditions impairs autophagic flux in cardiomyocytes after MI/R via marked inhibition of both autophagosome clearance and formation. Administration of an orally active APN receptor agonist increased autophagosome formation via AMPK activation, and stimulated autophagosome clearance in an AMPK-independent fashion. Improving autophagic flux by restoring APN signaling systems might be a novel intervention against MI/R injury in diabetic conditions.