Abstract 10730: Pkm2 Ablation Dysregulates Cardiac Glucose Metabolism in Mice

Abstract

Introduction: The predominant isoform of pyruvate kinase (PKM1) directs pyruvate to the Krebs cycle for oxidative metabolism in the healthy heart. Our lab described a hypoxia-mediated switch to the alternatively spliced isoform PKM2. The lower PKM activity of dimerized PKM2 redirects glycolytic metabolites to the pentose phosphate pathway (PPP) and lactate production. Recently, we have found that mice with deletion of Pkm2 had profound depletion of cardiac basal glucose and higher ROS levels compared to controls. Hypothesis: We hypothesize that glucose metabolism is dysregulated in the absence of Pkm2, where the remaining isoform PKM1 promotes oxidative metabolism, leading to accumulation of ROS. Methods: Global Pkm2 KO mice were used for this study. Transcript abundance was determined by RNA-seq and RT-qPCR. Cardiomyocytes were isolated according to an established Langendorff-free method, and metabolites were traced using [U- 13 C] glucose with LC/MS (n=3). ROS concentration was measured using DCFDA in cardiomyocytes incubated at 1% O 2 (n=4). Inflammatory marker C-reactive protein (CRP) was measured in plasma of mice before and after myocardial infarction (n=12). Results: Although glucose uptake was similar, glucose was redirected to fatty acid synthesis, the polyol pathway, and the PPP, and away from oxidative metabolism in Pkm2 KO cardiomyocytes. Despite the increased flux into the PPP, NADPH production was low. Assessment of ROS levels in normoxia revealed that Pkm2 KO cardiomyocytes had higher levels of ROS, possibly stimulating the inflammatory response in Pkm2 KO mice. CRP levels were higher in Pkm2 KO plasma at baseline. ROS remained high in Pkm2 KO cardiomyocytes after hypoxic treatment and CRP remained high in Pkm2 KO plasma after MI. Conclusions: Increased expression of Pkm1 in the Pkm2 KO mice increases flux of metabolites through oxidative metabolism, exacerbating mitochondrial ROS and activating the PPP. Although NADPH levels should have correlated with increased PPP flux, the low NADPH production in Pkm2 KO cardiomyocytes suggest rapid consumption of NADPH by ROS and fatty acid synthesis. This study suggests a role for hypoxia-stimulated PKM2 accumulation in stabilizing glucose flux to mitigate oxidative stress in the ischemic heart.