Chronic Rho-kinase inhibition improves left ventricular contractile dysfunction in early type-1 diabetes by increasing myosin cross-bridge extension

Impaired actin-myosin cross-bridge (CB) dynamics correlate with impaired left ventricular (LV) function in early diabetic cardiomyopathy (DCM). Elevated expression and activity of Rho kinase (ROCK) contributes to the development of DCM. ROCK targets several sarcomeric proteins including myosin light chain 2, myosin binding protein-C (MyBP-C), troponin I (TnI) and troponin T that all have important roles in regulating CB dynamics and contractility of the myocardium. Our aim was to examine if chronic ROCK inhibition prevents impaired CB dynamics and LV dysfunction in a rat model of early diabetes, and whether these changes are associated with changes in myofilament phosphorylation state. Seven days post-diabetes induction (65 mg/kg ip, streptozotocin), diabetic rats received the ROCK inhibitor, fasudil (10 mg/kg/day ip) or vehicle for 14 days. Rats underwent cardiac catheterization to assess LV function simultaneous with X-ray diffraction using synchrotron radiation to assess in situ CB dynamics. Compared to controls, diabetic rats developed mild systolic and diastolic dysfunction, which was attenuated by fasudil. End-diastolic and systolic myosin proximity to actin filaments were significantly reduced in diabetic rats (P