Abstract 14079: Targeted Deletion of Cardiac miR-17-92 Cluster Exacerbates Ischemic Myocardial Injury in Diabetic Mice Through Induction of Sphingolipid Biosynthesis and Cardiomyocyte Inflammation

Abstract

Background: The miR-17-92 cluster is indispensable for normal cardiac development and its deletion leads to cardiovascular disease. Aberrancies in bioactive sphingolipid metabolism, specifically ceramide (CER), contribute to diabetic cardiomyopathy, where induction of ceramide synthases (CerS) predicts elevated risk of cardiovascular complications. We investigated the role of miR-17-92 in suppression of ceramide synthesis to attenuate cardiac inflammation following myocardial ischemia/reperfusion (I/R) injury in diabetic mice. Methods and Results: Hearts from adult high-fat-diet fed diabetic tamoxifen-inducible cardiac-specific miR-17-92-deficient (miR-17-92-def) and wild type (WT) mice were subjected to 30 min of myocardial ischemia (I) and 60 min of reperfusion (R) in Langendorff mode. Myocardial infarct size was exacerbated with severe ventricular dysfunction in diabetic miR-17-92-def mice as compared to diabetic WT mice ( Fig. A ). Cardiomyocytes isolated from diabetic miR-17-92-def and WT mice were subjected to 40 min simulated ischemia and 2-hr reoxygenation (SI/RO). Immunofluorescence staining demonstrated an enhanced inflammasome formation with ASC (apoptosis speck-like protein with a caspase recruitment domain) aggregation ( Fig. B ) and caspase-1 activation ( Fig. C ) following SI/RO in cardiomyocytes isolated from diabetic miR-17-92-def mice. Lipidomics analysis revealed that C16:0 ceramide, a product of Ceramide Synthase 6 (CerS6), was induced after I/R injury and was more prominent in the hearts of diabetic miR-17-92-def mice (Fig. D). Western blot analysis revealed that CerS6 expression was nearly undetectable in the hearts of diabetic WT mice, but was dramatically induced by I/R in diabetic miR-17-92-def mice ( Fig. E ). Conclusion: The deletion of cardiac miR-17-92 exacerbates myocardial I/R injury under diabetic condition through accumulation of CER by inducing CerS6 and stimulating inflammation in cardiomyocytes.