Diabetes is a growing problem in all parts of the World. Clinical trials and animal models of type I and type II diabetes have shown that hyperactivity of angiotensin-II (Ang-II) signaling pathways contribute to the development of diabetes and diabetic complications. Of clinical relevance, blockade of the renin-angiotensin system (RAS) prevents new-onset diabetes and reduces the risk of diabetic complications. Angiotensin converting enzyme (ACE) 2 is a recently discovered mono- carboxypeptidase and the first homolog of ACE. It is thought to inhibit Ang-II signaling cascades mostly by cleaving Ang-II to generate Ang-(1-7), which effects oppose Ang-II and are mediated by the Mas receptor. The enzyme is present in various tissues and organs, including the kidney, liver, adipose tissue and pancreas. Its expression is elevated in the endocrine pancreas in diabetes and in the early phase during diabetic nephropathy. Pancreatic islets express both RAS components and NADPH oxidase (Nox) components, which are key elements in mediating oxidative stress. In the islet Ang-II and oxidative stress are both capable of decreasing insulin gene expression and secretion. ACE2 is hypothesized to oppose the ACE/Ang-II/AT1 receptor axis and may protect pancreatic beta- cell function by inhibiting both Nox activity and the Ang-II-mediated reduction of insulin gene expression and secretion. To manipulate ACE2 expression, we generated a novel adenovirus coding for ACE2 and reported increased ACE2 mRNA, protein and activity in cells and tissues. We hypothesize that ACE2 over-expression in the pancreas will reduce oxidative stress and ameliorate beta-cell function, thus leading to improved glucose homeostasis in diabetic mice. To test this hypothesis, we will address the following specific aims: 1) Determine the existence of a relationship between ACE2 expression and/or activity and diabetes;2) Evaluate the consequences of ACE2 over-expression in diabetic mice;3) Establish whether ACE2 over-expression improves pancreatic beta-cell function in diabetes. To achieve these goals, we will first use ACE2 knockout and db/db mouse (type 2 diabetes) models to establish the relationship between ACE2 and diabetes. Then we will combine state of the art molecular, pharmacological and physiological tools for in vitro (isolated islets) and in vivo (pancreas) gene therapy in pre-diabetic and young diabetic db/db mice. Finally, we will address the mechanisms by which ACE2 could potentially counterbalance the deleterious effects of the hyperactive RAS in diabetes. This proposal will show evidence of the beneficial effects of ACE2 over-expression on the normalization of blood glucose and highlight ACE2 as a new target for the treatment of diabetes.
Approximately 8% of Americans are affected by diabetes, a well known risk factor for cardiovascular diseases, and it is expected to grow due to the current obesity epidemic in the Western World. Using gene therapy in a mouse model of type 2 diabetes, this application will describe the ability of a new enzyme, ACE2, to regulate blood glucose levels. If confirmed, ACE2 could become a new target for the treatment of type 2 diabetes.
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