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型糖尿病的潜在原因，也是代谢综合征的定义特征。我们已经证明，雌激素可以保护男性免受代谢和基因紊乱的影响，这些紊乱会导致胰岛素抵抗，但随着年龄的增长，这种保护作用会消失，并与更年期相一致。与雌激素的作用类似，噻唑烷二酮（TZDs）激活ppar - γ (g)通过改变参与葡萄糖和脂肪酸代谢以及炎症的基因转录引起胰岛素致敏。我们之前已经证明，选择性骨骼肌PPAR-g缺失（MKO）会导致年轻和老年雄性小鼠的葡萄糖耐受不良和严重的胰岛素抵抗。令人惊讶的是，对雌性MKO小鼠的初步研究表明，骨骼肌PPAR-g的缺失会增强葡萄糖耐量和胰岛素敏感性，这与雄性小鼠的表型相反。随后，我们用TZD或雌二醇（E2）治疗雄性MKO小鼠，虽然TZD对骨骼肌胰岛素敏感性没有影响，但E2治疗导致胰岛素作用增加，高于WT对照小鼠，这涉及PPAR-g与雌激素受体之间的串扰。在Aim 1中，我们将验证PPAR-g降低雌激素化动物骨骼肌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，用或不加E2治疗的雄性和雌性小鼠的胰岛素敏感性。在Aim 2中，我们将验证罗格列酮激活PPAR-g的假设，即在卵巢切除和/或高脂肪饮食导致胰岛素抵抗的雌性大鼠中，降低E2的胰岛素增敏作用。在这两个目标中，我们将进行葡萄糖钳研究来评估胰岛素敏感性，并辅以体外研究来研究导致表型表达的分子机制。为此，Western blot和定量RT-PCR分析将对夹紧动物的组织进行分析，以评估肌肉和脂肪中胰岛素信号转导和基因转录的变化。这些研究对老年糖尿病妇女具有临床意义，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，并表明异常的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.