NR4A Orphan Receptors And Insulin Resistance

摘要 胰岛素抵抗是2型糖尿病(T2 DM)及其代谢的核心发病机制 增加胰岛素敏感性的药物或生活方式干预构成了有效的治疗方法 和预防。噻唑烷二酮类药物(TZD)通过核转录因子(即， PPAR？)以增强胰岛素敏感性；然而，TZD治疗与不良反应有关，包括 体重增加和心力衰竭。这些不良影响限制了临床应用，并强调了 可直接作用于肌肉的替代胰岛素增敏药物。我们将研究NR4A家族 孤儿核受体，它们被确认为人类肌肉上差异表达的基因 CDNA微阵列。大量的初步数据表明：(I)NR4A3在 胰岛素抵抗的人和啮齿动物；(Ii)TZD诱导NR4A3提示NR4A3可能是 TZD作用下游；(Iii)MCK-NR4A3转基因小鼠表现出胰岛素敏感的表型；(Iv) NR4A3受体的增加可以增强胰岛素信号和刺激葡萄糖运输；(V) PGA2以NR4A3依赖的方式增加胰岛素敏感性。去追寻这些小说 观察，我们的总体目标是增加我们对NR4A受体在 调节胰岛素的作用，它们在人类胰岛素抵抗中的作用，以及它们作为 治疗性药物靶标。为了实现这一目标，我们将利用我们实验室的翻译能力 研究包括人类新陈代谢、人类肌肉和脂肪组织活检、转基因小鼠和 培养的细胞系统。基于广泛的初步数据，具体目标是：(1)评估表达 胰岛素敏感、胰岛素抵抗和2型糖尿病患者肌肉和脂肪中NR4A受体的变化 在减肥和TZD治疗后，以及在胰岛素抵抗的啮齿动物模型中。(2)确立新陈代谢作用 通过对骨骼肌特异性高表达NR4A3的转基因小鼠进行表型鉴定。在……里面 人类和小鼠的NR4A表达将被评估其影响胰岛素敏感性和 在全身和单个细胞和组织水平上的底物代谢。(三)确定 NR4A3通过研究稳定高表达和shRNA调节胰岛素作用的机制 NR4A3在培养的肌肉和脂肪细胞中的介导抑制。这些研究将解决我们的 初步数据表明，NR4A3调节胰岛素刺激的葡萄糖转运，GLUT4 易位，以及胰岛素介导的信号分子的磷酸化。(4)确定脂质介体 NR4A3激动剂的初步数据表明，PGA2增加了 NR4A3依赖方式。因此，这项工作将阐明新的分子和病理生理学 促进胰岛素抵抗的过程，并为治疗和开发新的潜在药物靶点 预防糖尿病和心脏代谢性疾病。

Abstract Insulin resistance is central to the pathogenesis of Type 2 Diabetes (T2DM) and the Metabolic Syndrome, and drugs or lifestyle interventions that increase insulin sensitivity constitute effective therapy and prevention. Thiazolidinedione drugs (TZDs) act through agonism of nuclear transcription factors (i.e., PPAR¿) to enhance insulin sensitivity; however, TZD therapy is associated with adverse effects, including weight gain and heart failure. These untoward effects limit clinical utility, and highlight the need for alternative insulin-sensitizing medications that can act directly on muscle. We will study the NR4A family of orphan nuclear receptors, which were identified as differentially expressed genes on our human muscle cDNA microarrays. Extensive preliminary data indicate that: (i) NR4A3 is expressed at lower levels in insulin-resistant humans and rodents; (ii) TZDs induce NR4A3 suggesting that NR4A3 may be downstream of TZD action; (iii) MCK-NR4A3 transgenic mice exhibit an insulin sensitive phenotype; (iv) an increase in NR4A3 receptors can augment insulin signaling and stimulation of glucose transport; (v) PGA2 acts to increase insulin sensitivity in a NR4A3 dependent manner. To pursue these novel observations, our overall goal is to increase our understanding of the role of NR4A receptors in modulating insulin action, their role in human insulin resistance, and their rationale as a therapeutic drug target. To achieve this goal, we will apply our laboratory's capacity for translational research including human metabolism, human muscle and adipose tissue biopsies, transgenic mice, and cultured cell systems. Based on extensive preliminary data, the specific aims are: (1) Assess expression of NR4A receptors in muscle and fat in insulin sensitive, insulin resistant, and T2DM humans, before and after weight loss and TZD treatment, and in insulin resistant rodent models. (2) Establish metabolic role of NR4A3 by phenotyping transgenic mice with specific hyperexpression of NR4A3 in skeletal muscle. In both human and mouse, NR4A expression will be assessed for its ability to affect insulin sensitivity and substrate metabolism at the level of whole body and individual cells and tissues. (3) Determine mechanisms by which NR4A3 regulates insulin action by studying stable hyperexpression and shRNA- mediated suppression of NR4A3 in cultured muscle and adipose cells. These studies will address our preliminary data indicating that NR4A3 modulates insulin-stimulated glucose transport, GLUT4 translocation, and insulin-mediated phosphorylation of signaling molecules. (4) Identify lipid mediator agonists of NR4A3 based on preliminary data indicating that PGA2 increases insulin sensitivity in a NR4A3 dependent manner. Thus, this work will elucidate novel molecules and pathophysiologic processes contributing to insulin resistance, and develop new potential drug targets for the treatment and prevention of diabetes and cardiometabolic disease.