Diabetic cardiomyopathy (DCM) is a major cause of morbidity and mortality in the United States and is a rising global epidemic in parallel with the worldwide prevalence of obesity and type-2 diabetes mellitus (T2DM). However, the underlying molecular mechanisms in DCM remain poorly understood. It is believed that hyperinsulinemia might promote adverse consequences in the DCM hearts with T2DM and obesity. Recently, our collaborator, Dr. Kevin Xiang?s lab has discovered a novel mechanism that hyperinsulinemia might impair myocardial contractility by inhibiting adrenergic signaling and identified a direct interaction between insulin and adrenergic pathways of the heart in a T2DM C57J/B6 mouse model generated by feeding a high fat diet (HFD). Importantly, they have shown that the PKA phosphorylation of cardiac troponin I (cTnI, a critical sarcomeric regulatory protein) in response to adrenergic stimulation was impaired in HFD animals. Although post- translational modifications (PTM) of the sarcomeric proteins are known to be an important mechanism in the regulation of cardiac contraction and relaxation, its specific role in DCM hearts remains largely uncharacterized. Given that diastolic dysfunction and cardiomyocyte hypertrophy were ameliorated by a greater glycemic control in diabetic mice, I hypothesize that metabolic proteins will undergo various PTMs, like acetylation and phosphorylation, leading to a less efficient metabolic state and a reduced energy state, which will ultimately culminate in multiple altered sarcomeric PTMs and reduced contractility. Herein, I propose to utilize a novel ultra- high resolution mass spectrometry (MS)-based top-down proteomics platform to comprehensively characterize the sarcomeric proteins PTMs in DCM hearts. Moreover, I propose to investigate the interplay between sarcomeric PTMs and the metabolic state in DCM.
The specific aims of this proposal include: 1) Identify PTM changes of key regulatory sarcomeric proteins in response to T2DM-associated hyperinsulinemia in heart tissue using a top-down proteomics strategy and link the sarcomeric changes with alterations in cardiac contractility found by echocardiography measurements of HFD and normal chow (control) mice. 2) Identify changes in metabolic energy stores in parallel with lipid energy stores with attention to specific acyl chain information like acyl length, degrees of unsaturation, and lipid head group by utilizing a comprehensive metabolomics and lipidomics extraction protocol in DCM samples. 3) Identify PTM changes of metabolic proteins using a two- dimensional liquid chromatography mass spectrometry-based top-down proteomics platform and link the measured changes to the contractile dysfunction. The success of the proposed research will offer new insights into the molecular mechanism underlying DCM and may identify new therapeutic targets.
Diabetic cardiomyopathy (DCM) is a major cause of morbidity and mortality in the United States and is a rising global epidemic in parallel with the worldwide prevalence of obesity and type-2 diabetes mellitus, but the underlying molecular mechanisms remain poorly understood. This proposal aims to characterize the metabolic and contractile dysfunction in diabetic cardiomyopathy (DCM) using mass spectrometry-based proteomics and metabolomics. The success of the proposed research will offer new insights into the molecular mechanism underlying DCM which could aid in the development of future therapeutics to halt progression of DCM.
