SIRT3 Deficiency Impairs Hypoxic Signaling, Reprograms Basal Glycolytic Metabolism and Exacerbates Myocardial Ischemic Injury

Abstract

Increased glycolytic metabolism is critical for maintaining homeostasis of cardiomyocytes and endothelial cells (EC) during myocardial ischemia. Sirtuin 3 (SIRT3) is involved in epigenetic regulation of variety of cellular functions. The present study investigated the role of SIRT3 in altering glycolytic metabolism and hypoxia/ischemia responses using SIRT3 knockout (SIRT3 KO) mice and SIRT3 deficient EC. In vitro, exposure of EC to hypoxia up to 24 hours resulted in a gradual increase in HIF‐2α expression in WT and SIRT3 KO‐EC. Interestingly, hypoxia‐induced HIF‐2α expression was less in SIRT3 KO‐EC compared to EC isolated from WT mice. Moreover, hypoxia‐induced VEGF expression was reduced in SIRT3 KO‐EC. Using Seahorse XFe24 analyzer, EC glycolysis and mitochondrial function were further examined. Basal glycolysis, glycolytic reserve and glycolytic capacity were dramatically reduced in Sirt3 KO‐EC compared to WT‐EC. Moreover, Sirt3KO EC exhibited higher oxygen consumption rate than WT‐EC. Intriguingly, treatment with prolyl‐hydroxylase inhibitor‐dimethyloxalylglycine (DMOG) or VEGF rescued the impaired basal glycolytic metabolism in Sirt3 KO‐EC. Treatment with DMOG resulted in a reduction of basal oxygen consumption in WT‐EC, but failed to reduce basal oxygen consumption in Sirt3 KO‐EC. In vivo, SIRT3 KO mice subjected to ischemia exhibited a larger infarct size and impaired cardiac function compared to WT mice. VEGF and glycolytic enzyme PFKFB3 levels were significantly decreased in the heart of SIRT3 KO relative to WT mice. These studies suggest that the loss of SIRT3 aggravates myocardial ischemic injury by altering hypoxic signaling, glycolytic metabolism and increasing oxygen consumption.