Excessive O - GlcNAcylation Causes Heart Failure and Sudden Death.

Background: Heart failure is a leading cause of death worldwide and is associated with the rising prevalence of obesity, hypertension and diabetes. O-GlcNAcylation is a post-translational modification of intracellular proteins and serves as a metabolic rheostat for cellular stress. The total levels of O-GlcNAcylation are determined by nutrient and metabolic flux, in addition to the net activity of two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Failing myocardium is marked by increased O-GlcNAcylation, but it is unknown if excessive O-GlcNAcylation contributes to cardiomyopathy and heart failure. Methods: We developed two new transgenic mouse models with myocardial overexpression of OGT and OGA to control O-GlcNAcylation independent of pathological stress. Results: We found that OGT transgenic hearts showed increased O-GlcNAcylation, and developed severe dilated cardiomyopathy, ventricular arrhythmias and premature death. In contrast, OGA transgenic hearts had lower O-GlcNAcylation but identical cardiac function to wild type littermate controls. Additionally, OGA transgenic hearts were resistant to pathological stress induced by pressure overload with attenuated myocardial O-GlcNAcylation levels after stress and decreased pathological hypertrophy compared to wild type controls. Interbreeding OGT with OGA transgenic mice rescued cardiomyopathy and premature death, despite persistent elevation of myocardial OGT. Transcriptomic and functional studies revealed disrupted mitochondrial energetics with impairment of complex I activity in hearts from OGT transgenic mice. Complex I activity was rescued by OGA transgenic interbreeding, suggesting an important role for mitochondrial complex I in O-GlcNAc mediated cardiac pathology. Conclusions: Our data provide evidence that excessive O-GlcNAcylation causes cardiomyopathy, at least in part, due to defective energetics. Enhanced OGA activity is well tolerated and attenuation of O-GlcNAcylation is beneficial against pressure overload induced pathologic remodeling and heart failure. These findings suggest attenuation of excessive O-GlcNAcylation may represent a novel therapeutic approach for cardiomyopathy.