Molecular Mechanism of type 2 diabetes mellitus-mediated heart failure with preserved ejection fraction
Type 2 diabetes mellitus (T2DM) is a metabolic disease associated with several comorbidities, including cardiac dysfunction leading to heart failure with preserved ejection fraction (HFpEF), in turn resulting in T2DM-induced cardiomyopathy (T2DM-CM). However, the molecular mechanisms underlying the development of T2DM-CM are poorly understood. It is hypothesized that molecular alterations in myopathic genes induced by diabetes promote the development of HFpEF, whereas cardiac myosin inhibitors can rescue the resultant T2DM-induced cardiomyopathy. To test this hypothesis, a Leptin receptor-deficient db/db homozygous (Lepr db/db) mouse model was used to define the pathogenesis of T2DM-CM. Echocardiographic studies at 4 and 6 months revealed that Lepr db/db hearts started developing cardiac dysfunction by four months, and left ventricular hypertrophy with diastolic dysfunction was evident at 6 months. Strikingly, the level of cardiac myosin binding protein-C phosphorylation was significantly increased in Lepr db/db mouse hearts. RNA-seq data analysis, followed by functional enrichment, revealed the differential regulation of genes related to cardiac dysfunction in Lepr db/db heart tissues. Finally, using isolated skinned papillary muscles and freshly isolated cardiomyocytes, CAMZYOS (mavacamten, which is a prescription heart medicine used for symptomatic obstructive hypertrophic cardiomyopathy treatment (herein after denotes as MYK-461), was tested for its ability to rescue T2DM-CM. Compared with controls, MYK-461 significantly reduced force generation in papillary muscle fibers and cardiomyocyte contractility in the db/db group. This line of evidence shows that 1) T2DM-CM is associated with hyperphosphorylation of cardiac myosin binding protein-C and 2) MYK-461 significantly lessened disease progression, suggesting its promise as a therapeutic treatment for HFpEF. Overall design: To investigate the molecular mechanism underlying the development of T2DM CM, 6 months old leptin receptor deficient db/db homozygous mouse models were employed to understand the development of diabetic cardiomyopathy using  in vivo echocardiographic features, phosphorylation status of Mybpc3 and high throughput RNA sequencing of cardiac tissues.