Abstract 19536: Lipid Oversupply to Cardiomyocytes Induces Sphingolipid-dependent Oxidative Stress and Induction of Mitophagy Through Ceramide Synthase 2

Introduction: Diabetic cardiomyopathy (DbCM) contributes to the high risk of heart failure (HF) in diabetics, but mechanisms underlying DbCM remain unclear. We previously showed that highly saturated fat feeding in mice altered cardiomyocyte sphingolipid profiles leading to DbCM and that some of these maladaptations were dependent on autophagy and ceramide synthase 5 (CerS5). Hypothesis: In the present study, we sought to further understand the cellular processes in which lipid overload leads to DbCM in in the context of sphingolipids. Methods: Mice fed an obesogenic diet and in vitro studies using H9c2 cardiomyocytes were utilized in this study. Results: Increased oxidative stress and enhanced apoptosis were identified in the hearts of animals subjected to lipid overload, while animals treated with the sphingolipid synthesis inhibitor myriocin were protected. Similarly, cardiomyocytes treated with palmitate showed a sphingolipid-dependent increase of reactive oxygen species (ROS) and mitophagy. Treatment with mitochondria-targeted ceramide analogs induced cardiomyocyte cell death in an increasing chain length manner, which was exacerbated by inhibiting mitophagy. This suggested that lipotoxicity to cardiomyocytes occurs in part through oxidative stress in a sphingolipid-dependent manner, and mitophagy may occur to prevent further damage. Our observation that only longer chain ceramides led to these outcomes suggested involvement of CerS2 which specifically produces very long chain ceramides (C20 and higher). Overexpression of CerS2 showed increased mitophagy in cardiomyocytes and knockdown of CerS2 by CRISPR-CAS9 technology decreased mitophagy. Conclusions: Taken together, our data suggest that lipid overload induces mitophagy potentially as a protective measure in defense from CerS2-induced mitochondrial damage, oxidative stress and cell death in DbCM.