Adipocyte insulin signaling and circulating adiponectin levels

描述(由申请人提供)： 胰岛素抵抗状态，如肥胖、2型糖尿病(T2 DM)和代谢综合征(METS)与循环中低水平的脂联素有关，脂联素是一种专门由脂肪细胞产生的蛋白质。脂联素在肌肉和肝脏中具有胰岛素增敏作用，在血管系统中具有抗动脉粥样硬化特性。噻唑烷二酮(TZDS)是一类胰岛素增敏药物，可提高脂联素水平，但不依赖于它们对葡萄糖代谢的作用。胰岛素抵抗状态下这种反应和脂联素降低的机制尚不清楚。这项拟议的研究将检验这样一种假设，即胰岛素抵抗状态下脂联素下降的机制涉及脂肪细胞中胰岛素信号的受损，而提高血浆脂联素的治疗干预通过逆转这种损害来做到这一点。这项研究的目的是在对照组、T2 DM一级亲属和肥胖者中建立循环脂联素水平和脂肪细胞胰岛素信号之间的相关性。我们计划使用RT-PCR和蛋白质分析方法来评估脂联素的产生。在分离的脂肪细胞中用脉冲追逐实验检测脂联素的产生和分泌速度，用放射免疫法测定血浆脂联素。脂肪细胞的胰岛素敏感性(胰岛素的抗脂作用)将在体内使用同位素标记的代谢物在高胰岛素正血糖钳夹期间进行评估。PI3信号通路的活性，已知在胰岛素抵抗中受损，将在活组织脂肪组织中进行测量。然后，我们将试图证明，提高脂联素水平的治疗干预措施是通过通过PI 3-激酶途径改善脂肪细胞胰岛素信号来实现的。T2 DM患者将接受为期两个月的卡路里限制、二甲双胍或噻唑烷二酮治疗。治疗后，将重复脂联素、胰岛素敏感性和胰岛素信号转导措施。预防肥胖症、2型糖尿病和甲亢症患者的并发症仍然是公共卫生的优先事项。这项临床研究的预期结果可能为T2 DM、肥胖症和METS患者的潜在治疗靶点提供新的见解。

DESCRIPTION (provided by applicant): Insulin resistant states such as obesity, Type 2 diabetes (T2DM), and the Metabolic Syndrome (MetS) are associated with low circulating levels of adiponectin, a protein produced exclusively by adipocytes. Adiponectin has insulin sensitizing actions in muscle and liver, and anti-atherogenic properties in the vasculature. Thiazolidinediones (TZDs), an insulin sensitizing class of drugs, increase adiponectin levels independently of their actions on glucose metabolism. The mechanisms for this response and for decreased adiponectin in insulin resistant states are not yet understood. The proposed study will test the hypothesis that the mechanism underlying decreased adiponectin in insulin resistant states involves impaired insulin signaling in adipocytes and that therapeutic interventions that raise plasma adiponectin do so by reversing this impairment. This study will aim to establish a correlation between circulating adiponectin levels and adipocyte insulin signaling in controls, T2DM first-degree relatives, and obese subjects with and without T2DM. We plan to assess adiponectin production using RT-PCR and protein analysis methods. Adiponectin rate of production and secretion will be examined with pulse chase experiments in isolated adipocytes, and plasma adiponectin will be measured by radioimmunoassay. Adipocyte insulin sensitivity (anti-lipolytic effect of insulin) will be evaluated in vivo using isotope-labeled metabolites during hyperinsulinemic euglycemic clamp. The activity of the PI3-kinase signaling pathway, known to be impaired in insulin resistance, will be measured in biopsied adipose tissue. We will then attempt to demonstrate that therapeutic interventions which increase adiponectin levels do so by improving adipocyte insulin signaling though the PI 3-kinase pathway. T2DM subjects will be treated for two months with calorie restriction, metformin, or a thiazolidinedione. After treatment, adiponectin, insulin sensitivity, and insulin signaling measures will be repeated. The prevention of complications in patients with obesity, T2DM, and MetS continues to be a public health priority. The anticipated results of this clinical study may provide new insight into potential therapeutic targets in patients with T2DM, obesity, and MetS.