Type 2 Diabetes Mellitus is an important cause of morbidity and mortality, largely through its long-term cardiovascular consequences: Approximately two-thirds of all diabetes-related deaths are manifestations of cardiovascular disease. Recent work has implicated both the renin-angiotensin system and reactive oxygen species (ROS) in the pathogenesis and vascular complications of insulin resistance. We hypothesize that ROS represent the mechanism by which angiotensin II (Ang II) contributes to insulin resistance in the vasculature, and that they mediate many of the vasculopathies associated with this disease. In preliminary experiments, we have identified a novel potential molecular target, phosphoinositide-dependent kinase-1 (PDK-1), which may be the kinase responsible for angiotensin II-induced refractoriness to insulin. In this project, we will plan to determine the relationship between ROS and vascular insulin resistance in an animal model of type 2 diabetes, and to investigate the involvement of Ang II in mediating this pathway. These experiments will be performed in db/db mice, and the consequences of the interaction between Ang II and insulin will be investigated by assessing vascular glucose transport, aortic hypertrophy, endothelium-dependent relaxation and inflammation. In the second specific aim, we will define the role of nox4-derived ROS in mediating the effects of type 2 diabetes on vascular function. These studies will involve both cell culture work (antisense, siRNAs) and animal models (p22phox overexpressing mice as a model of nox4 overexpression crossed with db/db mice). Finally, we plan to determine the role of the redox-sensitive kinase PDK-1 in mediating the exacerbation of insuIin resistance by Ang II. We will use both a cell culture model and type 2 diabetic mice to explore in depth the relationship between PDK-1 and insulin-induced signaling pathways in VSMCs exposed to Ang II and insulin. These experiments will provide comprehensive information on how Ang II and RC compromised vascular function and as such may suggest new therapeutic targets for treatment of this burgeoning clinical problem.
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