Cardiovascular pathologies are the most deleterious outcomes of the insulin resistant syndrome and evidence links them to derangements in the renin angiotensin system (RAS). Our studies in dietary (fructose feeding) and genetic (leptin receptor mutant, db/db) models of insulin resistance show that there is increased insulin, impaired glucose tolerance and increased blood pressure (BP). We hypothesize that the cardiovascular changes are related to an imbalance between angiotensin converting enzyme (ACE) which produces angiotensin II (Ang II) and ACE2 which produces Ang (1-7). Data documents developmental, age-related changes in BP and ACE/ACE2 balance in db/db mice as well as changes in ACE/ACE2 after fructose overload. Using a sophisticated series of in vivo cardiovascular tests along with mass spectrometric (MS) assays for ACE activity, immunoassays for Ang peptide forms, molecular methods for mRNA quantification and siRNA gene silencing, we plan to follow the etiology and treatment of dietary and genetic forms of insulin resistant diabetes. The questions to be addressed are the following: 1) What is the nature of the changes in ACE/ACE2 balance in the fructose model of insulin resistance and what is the effect of blockade of the RAS and Ang receptors?;2) What is the nature of the changes in ACE/ACE2 balance in the genetic db/db model of insulin resistance and what is the effect of blockade of the RAS and Ang receptors? and 3) What is the effect of genetic manipulation of ACE/ACE2 and Ang receptors on the cardiovascular and metabolic response to dietary induced insulin resistance? We will use transgenic mice which over- express ACE and mice which lack ACE2 as well as shRNA gene silencing for Ang receptors. The research program should provide new information on the endocrine enzymatic mediators of the cardiovascular pathologies associated with experimental models for type-2 diabetes.
Insulin resistant diabetes is a major health problem with cardiovascular dysfunction being a primary cause of mortality and morbidity. The proposed research project will study the development of cardiovascular and metabolic derangements in animal models of insulin resistance. The hypothesis is that changes in the renin angiotensin system, specifically angiotensin converting enzyme balance, are a key factor.
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