Obesity is associated with cardiac insulin resistance and contractile dysfunction, which contribute to the development of heart failure. The RhoA-Rho kinase (ROCK) pathway has been reported to modulate insulin resistance, but whether it is implicated in obesity-induced cardiac dysfunction is not known. To test this, wild-type (WT) and ROCK2(+/-) mice were fed normal chow or a high-fat diet (HFD) for 17 wk. Whole body insulin resistance, determined by an insulin tolerance test, was observed in HFD-WT, but not HFD-ROCK2(+/-), mice. The echocardiographically determined myocardial performance index, a measure of global systolic and diastolic function, was significantly increased in HFD-WT mice, indicating a deterioration of cardiac function. However, no change in myocardial performance index was found in hearts from HFD-ROCK2(+/-) mice. Speckle-tracking-based strain echocardiography also revealed regional impairment in left ventricular wall motion in hearts from HFD-WT, but not HFD-ROCK2(+/-), mice. Activity of ROCK1 and ROCK2 was significantly increased in hearts from HFD-WT mice, and GLUT4 expression was significantly reduced. Insulin-induced phosphorylation of insulin receptor substrate (IRS) Tyr(612), Akt, and AS160 was also impaired in these hearts, while Ser(307) phosphorylation of IRS was increased. In contrast, the increase in ROCK2, but not ROCK1, activity was prevented in hearts from HFD-ROCK2(+/-) mice, and cardiac levels of TNFα were reduced. This was associated with normalization of IRS phosphorylation, downstream insulin signaling, and GLUT4 expression. These data suggest that increased activation of ROCK2 contributes to obesity-induced cardiac dysfunction and insulin resistance and that inhibition of ROCK2 may constitute a novel approach to treat this condition.
Keywords: ROCK2; heart; insulin receptor substrate phosphorylation; insulin signaling.
Copyright © 2015 the American Physiological Society.