This is a competitive renewal of RO1 DK45935. The overall goal of this project is to identify changes in gene expression in skeletal muscle of humans and rodents with Type 2 diabetes mellitus and to define the role of such changes in the pathophysiology of diabetes. Using subtraction cloning and PCR-differential display, we have identified 11 alterations in gene expression in muscle from patients with Type 2 diabetes and 17 alterations in an animal model of Type 2 diabetes, the ob/ob mouse. In addition, we have characterized aspects of regulation and possible roles for several of these genes in diabetes and insulin resistance, including glycogen phosphorylase, genes of the mitochondrial genome, elongation factor 1alpha, geranylgeranyl pyrophosphate synthase, and the novel GTPase Rad. We have also identified variations in two candidate genes for Type 2 diabetes that can influence the expression of genes: one is a triplet expansion in the Frederick's ataxia gene and the other is a novel activating mutation in PPARgamma, a known regulator of insulin sensitivity via its action on gene expression. In the coming period we propose to focus on the role of gene expression in the pathophysiology of diabetes using normal and mutant PPARgamma as tools to identify insulin resistance/ sensitivity pathways, and to expand the search for alterations in gene expression using newer and more powerful DNA chip array technology.
The specific aims are to: l) Characterize normal and mutant PPARgamma as potential obesity/diabetes genes by construction and characterization of transgenic mice expressing these genes in adipose tissue and muscle; 2) Identify changes in gene expression of various tissues of mice overexpressing normal and mutant PPARgamma in muscle vs. fat with and without thiazolidinedione (TZD) treatment; 3) Determine the effect of a muscle-specific knockout of PPARgamma on insulin sensitivity and TZD-induced changes in gene expression; 4) Identify alterations in gene expression in muscle from humans with Type 2 diabetes using DNA chip analysis and characterize the relationship of these changes to metabolic control, type of diabetes (those limited to Type 2 diabetes may reflect primary defects or specific alterations due to insulin resistance); and the effect of insulin-sensitizing TZDs on the alterations in gene expression in the Type 2 diabetic; and 5) Analyze alterations in gene expression in other insulin resistant states, particularly obesity, and in normoglycemic offspring of diabetic parents subgrouped by presence or absence of insulin resistance.
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