Project Summary/Abstract Cardiovascular disease (CVD) and type II diabetes (TIID) are intimately linked, as TIID more than doubles a patient’s risk of developing CVD. This pathology is termed ‘diabetic cardiomyopathy’ (DC), and occurs independent of other risk factors. A major but poorly understood component of DC pathogenesis is impaired insulin signaling, or insulin resistance (IR). However, current therapeutics center on blood glucose management and reduction, rather than insulin sensitivity restoration. As such, this proposal centers upon the identification and investigation of putative major molecular mediators of cardiac insulin sensitivity and resistance, in an effort to identify novel therapeutic targets for DC to reduce disease burden. Utilizing unbiased genome-wide studies, my laboratory identified ‘regulated in development and DNA damage 1’ (Redd1, also Ddit4) as the most transcriptionally active, insulin-inducible gene in the murine heart. This increase in transcriptional activity translated to increases in both REDD1 gene and protein expression. REDD1 is known to inhibit mTORC1 signaling, but the exact mechanism by which this occurs is unknown. Notably, REDD1 is shown to be involved in both insulin sensitivity and resistance. Our preliminary data indicate that high fat diet (HFD) and fatty acids increase REDD1 expression, further suggesting a role for REDD1 in IR. Our data also outline a novel mechanism in which insulin increases REDD1 expression, nuclear localization, and chromatin binding. This increase in chromatin binding is associated with alterations in transcriptional activity, enhancing the transcriptional activity of oxidative metabolic genes in the heart. Thus, it is our hypothesis that high fat diet prevents REDD1 nuclear localization, resulting in suppressed oxidative metabolism mainly via the loss of REDD1-dependent transcriptional regulation, as well as enhanced inhibition of mTORC1, ultimately driving IR. We will test this hypothesis with two specific aims. We will, first, determine the role of REDD1 in mediating cardiac insulin resistance and, second, investigate the mechanism of REDD1 nuclear localization and its transcriptional role in mediating cardiac insulin sensitivity. Here, we will utilize a novel murine model with cardiac REDD1 deletion for in vivo studies and isolate cardiomyocytes for in vitro studies. These mice or cardiomyocytes will be subjected to high fat/fatty acids to induce insulin resistance. We will also employ a novel REDD1 mutant to examine the contribution of REDD1 nuclear localization to cardiac insulin sensitivity and resistance. Overall, we expect that high fat will prevent insulin-inducible REDD1 nuclear localization, chromatin binding, and activation of oxidative metabolic genes. We hypothesize that this is a major mechanism by which high fat mediates IR. These studies are critical, as we predict that restoration of nuclear REDD1 will restore cardiac sensitivity to insulin, prevent subsequ...