Abstract 18978: Lysine Acetylation of Pyruvate Dehydrogenase Reduces Enzymatic Activity and Contributes to Impaired Substrate Metabolism in the Failing Myocardium

Introduction: Many heart failure (HF) associated non-histone proteins are modified by post-translational lysine acetylation which regulates protein activity and affects cardiac function. Hypothesis: We hypothesized that acetylation of mitochondrial proteins involved in cardiac metabolism mediate metabolic changes in the failing myocardium. We focused on pyruvate dehydrogenase (PDH) which converts pyruvate, the end-product of glycolysis, to acetyl-CoA, a substrate of the citric acid cycle. Methods: Human myocardial tissue from HF patients, failing rodent myocardium after transverse aortic constriction (TAC) induced pressure-overload HF and human cardiomyocyte-like AC16 cells were used. Western Blot, immunoprecipitation assays and mass spectrometry were performed to analyze protein expression and acetylation levels. Results: In our studies, we observed a significant increase in overall cardiac protein acetylation in both HF patients (5.8-fold, p<0.05) and in TAC mice (1.8-fold) versus controls. Interestingly, these changes are correlated with a 72% decrease in mitochondrial deacetylase SirT3 expression. The sirtuin inhibitor nicotinamide (NAM) was used to induce mitochondrial protein acetylation. In AC16 cells, NAM treatment leads to a 1.4-fold increase in PDH acetylation level and a 26% decrease in PDH activity was observed (p<0.01). Interestingly, immunoprecipitation assays showed that several PDH associated proteins are also acetylated in response to NAM treatment. Human proteomic mass spectrometry screening confirmed increased PDH acetylation in failing human myocardium compared to control samples. Furthermore, PDH expression is reduced by 47% in failing human myocardium compared to controls (p<0.01). Finally, PDH activity was found to be decreased by 56% (p<0.01) in human failing myocardium compared to controls. Conclusions: Together, our data suggest that increased acetylation of PDH due to reduced SirT3 expression in HF contributes to altered mitochondrial substrate metabolism and is associated with cardiac dysfunction. These findings suggest a novel role for acetylation of PDH in the failing myocardium.