NR4A Orphan Receptors And Insulin Resistance

描述（由申请人提供）：胰岛素抵抗是2型糖尿病（T2 DM）和代谢综合征发病机制的核心，增加胰岛素敏感性的药物或生活方式干预构成有效的治疗和预防。噻唑烷二酮药物（TZD）通过激动核转录因子（即，PPAR 3）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。这些不良反应限制了临床应用，并突出了对可直接作用于肌肉的替代胰岛素增敏药物的需求。我们将研究NR 4A家族的孤儿核受体，这被确定为差异表达的基因在我们的人肌肉cDNA微阵列。大量的初步数据表明：（i）NR 4A 3在胰岛素抵抗的人和啮齿动物中以较低水平表达;（ii）TZD诱导NR 4A 3，表明NR 4A 3可能是TZD作用的下游;（iii）MCK-NR 4A 3转基因小鼠表现出胰岛素敏感表型;（iv）NR 4A 3受体的增加可增强胰岛素信号传导和刺激葡萄糖转运;（V）PGA 2以NR 4A 3依赖性方式起增加胰岛素敏感性的作用。为了追求这些新的观察结果，我们的总体目标是增加我们对NR 4A受体在调节胰岛素作用中的作用，它们在人类胰岛素抵抗中的作用以及它们作为治疗药物靶点的原理的理解。为了实现这一目标，我们将利用我们实验室的能力进行转化研究，包括人体代谢，人体肌肉和脂肪组织活检，转基因小鼠和培养细胞系统。基于广泛的初步数据，具体目的是：（1）评估体重减轻和TZD治疗前后胰岛素敏感、胰岛素抵抗和T2 DM人群以及胰岛素抵抗啮齿动物模型中肌肉和脂肪中NR 4A受体的表达。(2)通过对骨骼肌中NR 4A 3特异性高表达的转基因小鼠进行表型分析，确定NR 4A 3的代谢作用。在人和小鼠中，将评估NR 4A表达在全身和个体细胞和组织水平上影响胰岛素敏感性和底物代谢的能力。(3)通过研究培养的肌肉和脂肪细胞中NR 4A 3的稳定过表达和shRNA介导的抑制，确定NR 4A 3调节胰岛素作用的机制。这些研究将解决我们的初步数据表明，NR 4A 3调节胰岛素刺激的葡萄糖转运，GLUT 4易位，和胰岛素介导的信号分子磷酸化。(4)基于表明PGA 2以NR 4A 3依赖性方式增加胰岛素敏感性的初步数据，鉴定NR 4A 3的脂质介质激动剂。因此，这项工作将阐明导致胰岛素抵抗的新分子和病理生理过程，并开发新的潜在药物靶点用于治疗和预防糖尿病和心脏代谢疾病。胰岛素抵抗是导致2型糖尿病和代谢综合征的关键因素。胰岛素抵抗的治疗可以预防糖尿病并控制已经患有糖尿病的患者的血糖;然而，可用的药物具有严重的副作用，限制了它们的使用。这项研究将首次阐明一个新的孤儿核转录因子家族（NR 4A）在胰岛素抵抗中的作用，以及它们作为治疗和预防2型糖尿病新药靶点的潜力。

DESCRIPTION (provided by applicant): 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., PPAR3) 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. PUBLIC HEALTH RELEVANCE: Insulin resistance is a critical factor causing Type 2 Diabetes and the Metabolic Syndrome. Treatment of insulin resistance can prevent diabetes and control blood sugars in patients who already have the disease; however, the available medications have serious side effects which limit their use. This research will elucidate, for the first time, the role of a novel family of orphan nuclear transcription factors (NR4A) in the cause of insulin resistance, and their potential as targets for new drugs to treat and prevent Type 2 Diabetes.