The impact of PPAR-gamma and estrogen receptor crosstalk on insulin action

描述（由申请人提供）：胰岛素抵抗是2型糖尿病的根本原因，也是代谢综合征的定义特征。我们已经表明，雌激素提供了保护，从代谢和遗传干扰已知导致胰岛素抵抗的男性，这种保护是失去了与年龄和符合更年期。与雌激素的作用类似，噻唑烷二酮（TZD）激活的PPAR-gamma（g）通过改变参与葡萄糖和脂肪酸代谢以及炎症的基因的转录而引起胰岛素敏化。我们以前已经表明，选择性骨骼肌PPAR-g缺失（MKO）导致葡萄糖耐受不良和严重的胰岛素抵抗，在年轻和老年雄性小鼠。令人惊讶的是，在雌性MKO小鼠中的初步研究表明，骨骼肌PPAR-g的损失产生增强的葡萄糖耐量和胰岛素敏感性，这是与雄性所描述的表型相反的表型。随后，我们用TZD或雌二醇（E2）处理雄性MKO小鼠，虽然TZD对骨骼肌胰岛素敏感性没有影响，但E2处理引起高于WT对照小鼠观察到的胰岛素作用增加，这暗示PPAR-g和雌激素受体之间的串扰。在目的1中，我们将测试PPAR-g降低雌激素化动物骨骼肌中ER作用的假设。我们将评估在存在（fl/fl对照）或不存在骨骼肌PPAR-g（MKO）的情况下用或不用E2处理的雄性和雌性小鼠中的胰岛素敏感性。在目的2中，我们将检验罗格列酮对PPAR-g的激活作用减弱E2对雌性大鼠的胰岛素增敏作用的假设，雌性大鼠因卵巢切除术和/或高脂饮食而产生胰岛素抵抗。在这两个目标中，我们将进行葡萄糖钳夹研究，以评估胰岛素敏感性，并辅之以体外研究，以研究导致表型表达的分子机制。为此，将对从钳夹动物采集的组织进行Western印迹和定量RT-PCR分析，以评估肌肉和脂肪中胰岛素信号转导和基因转录的变化。这些研究对于高龄糖尿病女性具有临床重要性，因为这些激动剂对基因转录的相互作用尚不清楚。此外，我们的目标是阐明核受体串扰在基因转录调控中的重要性，并表明异常串扰是胰岛素抵抗和肥胖的潜在机制。

DESCRIPTION (provided by applicant): Insulin resistance is an underlying cause of type 2 diabetes and a defining feature of the Metabolic Syndrome. We have shown that estrogen provides protection from metabolic and genetic perturbations known to cause insulin resistance in males and this protection is lost with age and coinciding with menopause. Similar to the effects of estrogen, PPAR-gamma (g) activation by thiazolidinediones (TZDs) causes insulin sensitization via alterations is transcription of genes involved in glucose and fatty acid metabolism as well as inflammation. We have previously shown that selective skeletal muscle PPAR-g deletion (MKO) causes glucose intolerance and severe insulin resistance in young and aged male mice. Surprisingly, preliminary studies in female MKO mice show that loss of skeletal muscle PPAR-g yields enhanced glucose tolerance and insulin sensitivity, a phenotype opposite of that described for males. Subsequently we have treated male MKO mice with a TZD or estradiol (E2), and while the TZD was without effect on skeletal muscle insulin sensitivity, E2 treatment caused increased insulin action above that observed for WT control mice which implicates a crosstalk between PPAR-g and the estrogen receptor. In Aim 1, we will test the hypothesis that PPAR-g decreases ER action in skeletal muscle from estrogenized animals. We will assess insulin sensitivity in male and female mice treated with or without E2 in the presence (fl/fl Control) or absence of skeletal muscle PPAR-g (MKO). In Aim 2 we will test the hypothesis that PPAR-g activation by Rosiglitazone diminishes the insulin sensitizing effects of E2 in female rats rendered insulin resistant by ovariectomy and or high fat diet. In both aims we will perform glucose clamp studies to assess insulin sensitivity complemented by in vitro studies to investigate the molecular mechanisms leading to phenotypic expression. To this end, Western blot and quantitative RT-PCR analyses will be performed on tissues harvested from clamped animals to assess alterations in insulin signal transduction and gene transcription in muscle and fat. These studies are of clinical importance for diabetic women of advanced age as the interaction of these agonists on gene transcription is unknown. Additionally our goal is to elucidate the importance of nuclear receptor crosstalk in the regulation of gene transcription and show that aberrant crosstalk is an underlying mechanism of insulin resistance and obesity.