Insulin Resistance Mediates Crosstalk between Skeletal Muscle and the Heart to Prevent Cardiac Dysfunction

Abstract

Obesity and type 2 diabetes milieus (T2DM) are the leading causes of cardiovascular morbidity and mortality. Although insulin resistance is believed to underlie these disorders, a paradox exists that obese patients with cardiovascular diseases have better prognoses relative to leaner patients with the same diagnoses, whereas improvement of insulin sensitivity by thiazolidines significantly increases the risk of heart failure in T2DM patients. Using mice with skeletal muscle-specific deletion of the insulin receptor gene (MIRKO), we resolved this dilemma by demonstrating that insulin resistance in the skeletal muscle prevents myocardial hypertrophy and dysfunction in response to diet-induced obesity. In spite of aggregating obesity, insulin resistance selectively protected the heart, but not other metabolic tissues, from mitochondrial dysfunction and insulin resistance in MIRKO mice, leading to significant attenuation of inflammation and apoptosis of cardiomyocytes. Together, our findings revealed an unexpected role of insulin resistance as a double edge sword, calling for reevaluation of ongoing efforts for targeting insulin resistance for the treatment of metabolic diseases. Significance statementInsulin resistance is commonly recognized as one of the major causes of T2DM and other aging-related chronic diseases. However, cumulative efforts in targeting insulin resistance for the treatment of T2DM and other metabolic disorders have not met with great success due to unwanted side effects on heart failure. Here we report that insulin resistance in skeletal muscle is a double edge sword. On one hand, insulin resistance in skeletal muscle aggregates obesity and its related metabolic syndromes, and on the other it protects the heart from the development of myocardial hypertrophy, dysfunction, and apoptosis in response to DIO. Our findings call for reevaluation of the ongoing strategies in targeting insulin resistance as a novel treatment for T2DM and other metabolic diseases.