The Role of an RNA Binding Protein, Tristetrapolin, in Hepatic Glucose Metabolism and the Development of Diabetes

 描述（由申请人提供）：II型糖尿病（T2 DM）是一种代谢紊乱，其特征为胰岛素抵抗和葡萄糖稳态受损。全世界有超过1.7亿人患有T2 DM，并且这种疾病的患病率正在稳步上升;这表明迫切需要对这种疾病的分子机制进行新的见解。Tristetraprolin（TTP）是一种串联锌指蛋白，其与靶mRNA分子的3 '-非翻译区（3'-UTR）中的富含AU的元件结合，并促进其降解。几条证据表明TTP和代谢过程之间存在联系。首先，TTP是一种胰岛素应答基因，其表达减少与人类代谢综合征和胰岛素抵抗有关。第二，TTP的酵母同源物Cth 1/2 p的缺失已被证明增加参与氧化代谢的线粒体蛋白。最后，我们最近的研究结果表明，TTP mRNA和蛋白质水平在糖尿病小鼠的肝脏中降低，并且肝脏特异性TTP缺失增加了肥胖诱导的糖尿病小鼠模型中的全身葡萄糖敏感性。我们还鉴定了参与葡萄糖氧化的TTP的两个靶标，其表达在TTP敲除的原代肝细胞中增加;丙酮酸脱氢酶- E2亚基（PDC-E2），其将丙酮酸转化为乙酰辅酶A以随后用于TCA循环;和硫辛酸合成酶（LIAS），其是硫辛酸（LA）合成中的限速酶。LIAS和PDC-E2的协调调节至关重要，因为LA是PDC-E2功能所需的辅因子。我的中心假设是，胰岛素刺激的TTP表达通过调节PDC-E2和LIAS的水平来降低肝脏葡萄糖利用，并且肝脏中TTP的缺失通过其对这些蛋白质的水平和葡萄糖代谢的影响来防止DM的发展。我将在两个具体的实验中检验这个假设。 目标。在目标1中，我将确定TTP是否通过PDC依赖性途径和通过其在LA生物合成中的作用来调节肝脏葡萄糖代谢。在目标2中，我将确定肝脏TTP表达的减少是否由于其对肝脏葡萄糖利用的影响而对糖尿病的发展具有保护作用。这些调查路线是 首先，研究mRNA结合蛋白在肝脏代谢调节中的作用，并有望促进我们对TTP在调节细胞代谢中的作用的认识。这些研究可能会导致开发新的治疗葡萄糖代谢紊乱，如糖尿病。

 DESCRIPTION (provided by applicant): Type II Diabetes Mellitus (T2DM) is a metabolic disorder characterized by insulin resistance and impaired glucose homeostasis. Over 170 million people worldwide suffer from T2DM and the prevalence of this disease is steadily rising; indicating that new insights into the molecular mechanisms underlying this disease are sorely needed. Tristetraprolin (TTP) is a tandem zinc finger protein that binds to AU-rich elements in the 3'-untranslated region (3'-UTR) of target mRNA molecules, and promotes their degradation. Several lines of evidence have suggested a link between TTP and metabolic processes. First, TTP is an insulin-responsive gene and its reduced expression has been linked to metabolic syndrome and insulin-resistance in humans. Second, deletion of the yeast homolog of TTP, Cth1/2p, has been shown to increase mitochondrial proteins involved in oxidative metabolism. Lastly, our recent results show that TTP mRNA and protein levels are reduced in livers of diabetic mice, and that liver-specific deletion of TTP increases systemic glucose sensitivity in a mouse model of obesity-induced diabetes. We have also identified two targets of TTP involved in glucose oxidation whose expression increases in TTP knock-out primary hepatocytes; Pyruvate Dehydrogenase - E2 subunit (PDC-E2), which converts pyruvate into acetyl-CoA for subsequent use in the TCA cycle, and Lipoic Acid Synthase (LIAS), the rate limiting enzyme in the synthesis of lipoic acid (LA). Coordinated regulation of LIAS and PDC-E2 is crucial as LA is a required cofactor for PDC-E2 function. My central hypothesis is that insulin stimulated expression of TTP reduces hepatic glucose utilization by modulating the levels of PDC-E2 and LIAS and that loss of TTP in the liver protects against the development of DM through its effects on the levels of these proteins and glucose metabolism. I will test this hypothesis in two specific aims. In Aim 1, I will determine whether TTP regulates hepatic glucose metabolism through a PDC-dependent pathway and through its role in the biosynthesis of LA. In Aim 2, I will determine whether a reduction in hepatic TTP expression is protective against the development of diabetes due to its effects on hepatic glucose utilization. These lines of investigation are the first to look at the role of an mRNA binding protein that causes mRNA degradation in the regulation of liver metabolism and promise to advance our knowledge of the role of TTP in regulating cellular metabolism. These studies may potentially lead to the development of novel therapies for disorders of glucose metabolism, such as DM.