Exploiting novel biosensors to probe insulin-modulated signaling pathways in diabetic cardiomyopathy

For many years, the effects of diabetes on the heart were studied principally in the context of coronary artery and small vessel disease. By contrast, the pathogenesis of diabetic cardiomyopathy is less completely understood. The central aim of the proposed pilot studies is to identify mechanisms whereby insulin receptor-dependent modulation of intracellular reactive oxygen species (ROS) regulates cardiac myocyte signal transduction and physiological responses, with the ultimate goal of understanding the pathobiological basis of diabetic cardiomyopathy and identifying new drug targets.

Our long-standing studies on the biochemistry of endothelial nitric oxide synthase (eNOS) led to our recent discovery that protein phosphorylation pathways regulated by reactive oxygen species (ROS) are critical for NOS regulation. Insulin signaling has long been known to be modulated by ROS, but the molecular mechanisms are almost entirely unknown. We probed the roles of insulin-modulated ROS on cardiac myocyte function, and discovered that insulin-dependent signaling responses in cardiac myocytes are entirely dependent on the stable ROS hydrogen peroxide (H2O2). We found that cardiac myocytes isolated from mice fed a high-fat diet develop insulin resistance in cellular signaling responses involving H2O2. We cloned and characterized a series of novel differentially-targeted constructs expressing the H2O2 biosensor HyPer in the cardiotropic adeno-associated virus-9 (AAV9). We exploited these AAV9-based HyPer constructs in advanced cellular imaging approaches in mouse models in vivo to probe the roles of ROS in cardiac myocyte insulin signaling. We propose to exploit our novel H2O2 biosensors to characterize insulin-modulated ROS pathways in cardiac myocytes in a mouse model of type II diabetes.

The proposed studies will identify the physiological as well as pathophysiological pathways controlling insulin-modulated ROS responses in the heart, and may identify novel targets for the prevention and treatment of cardiac dysfunction in diabetes.

Lay summary: Many patients with diabetes suffer a form of heart failure called “diabetic cardiomyopathy”. With the increasing prevalence of diabetes in the USA, diabetic cardiomyopathy has become a public health problem without effective cures. The proposed studies will study heart cells (cardiac myocytes) using advanced imaging methods and novel biosensors to identify new therapeutic targets that may help to prevent and treat heart disease in diabetic patients.