Mitochondrial Dysfunction and Adipose Insulin Resistance

描述(由申请人提供)：各种动物、细胞培养和分子研究表明，氧化应激增加和活性氧物种(ROS)的积累(如超氧阴离子和羟基自由基)与2型糖尿病有关。虽然多年来一直被认识到，但尚不清楚氧化应激/ROS是疾病病因中的偶然因素还是因果因素。然而，最近利用各种功能丧失和获得分析的工作表明，氧化应激与胰岛素抵抗有因果关系，但分子机制仍不清楚。这项应用将介绍我们实验室使用动物和细胞培养模型得出的新的令人信服的发现，这些模型建立了脂肪细胞中的抗氧化防御系统与线粒体功能、氧化磷酸化、信号转导和胰岛素抵抗发展之间的分子联系。我们提出了一个新的假说，该假说得到了来自基因组、蛋白质组、代谢组学和分子分析的初步研究的支持，这些研究表明，线粒体蛋白质与生物活性脂质的共价修饰和线粒体硫氧还蛋白的氧化是这一过程的中心。发起这一氧化应激挑战的新发现描述了肿瘤坏死因子1(TnF1)对谷胱甘肽S转移酶A4的下调作用，为激活c-jun NH2末端激酶(已建立的胰岛素敏感性调节因子)的分子级联反应奠定了基础。此外，我们提出的新发现表明，GSTA4的下调不仅是在胰岛素抵抗的动物模型中观察到的过程，而且也选择性地发生在肥胖、胰岛素抵抗但不肥胖的胰岛素敏感者中，从而提供了肥胖和胰岛素抵抗之间的分子差异。这一应用建立在Bernlohr、Griffin和Arriaga实验室最近获得的证据的基础上，这些证据在功能上将氧化应激与胰岛素抵抗联系起来。总而言之，这些研究导致了我们的中心假设：脂肪细胞中GSTA4的表达减少导致多个蛋白质靶点的羰基化增加。甲基化进而引发一系列分子事件，导致线粒体功能障碍和ROS的产生。ROS的产生导致硫氧还蛋白2(Trx2)的氧化和Trx2-ASK1-JNK/p38信号系统的激活，从而导致胰岛素抵抗。为了验证这一假设，提出了以下四个特定目标：特定目标1.评估线粒体蛋白的甲基化并确定目标蛋白。具体目的2.评估细胞培养和动物模型中ROS的产生和线粒体电子传递系统。特定目的3.低脂和高脂饲料饲养的aP2-HA-GSTA4转基因小鼠的建立和鉴定。具体目的4.在动物和细胞培养模型中研究细胞代谢和Trx2-ASK1-JNK途径。 公共卫生相关性：各种动物、细胞培养和分子研究表明，氧化应激增加和活性氧簇(ROS)积累与2型糖尿病相关。虽然多年来一直被认识到，但尚不清楚氧化应激/ROS是疾病病因中的偶然因素还是因果因素。这项应用将介绍我们实验室使用动物和细胞培养模型得出的新的令人信服的发现，这些模型建立了脂肪细胞中的抗氧化防御系统与线粒体功能、氧化磷酸化、信号转导和胰岛素抵抗发展之间的分子联系。我们提出的新发现表明，GSTA4的下调不仅是在胰岛素抵抗的动物模型中观察到的过程，而且也选择性地发生在肥胖、胰岛素抵抗但不肥胖的胰岛素敏感者中，从而提供了肥胖和胰岛素抵抗之间的分子差异。如果这一假设被证明是正确的，这项研究将立即转化为人类生物学，并为如何对抗2型糖尿病提供一个新的视角。

DESCRIPTION (provided by applicant): A variety of animal, cell culture and molecular studies have correlated increased oxidative stress and the accumulation of reactive oxygen species (ROS) such as superoxide anion and hydroxyl radicals to type 2 diabetes. While appreciated for years, it was unclear if oxidative stress / ROS was a casual or causal factor in the etiology of the disease. However, more recent work utilizing a variety of loss and gain of function analyses have indicated that oxidative stress is causally linked to insulin resistance but that the molecular mechanisms remain obscure. This application will profile new and compelling findings from our laboratories using animal and cell culture models that establish a molecular linkage between the antioxidant defense system in adipose cells with mitochondrial function, oxidative phosphorylation, signal transduction and the development of insulin resistance. We present a novel hypothesis supported by preliminary studies from genomic, proteomic, metabolomic and molecular analyses that point toward the covalent modification of mitochondrial proteins with bioactive lipids and the oxidation of mitochondrial thioredoxin as central to the process. Initiating this oxidative stress challenge are new findings that describe the tumor necrosis factor 1 (TNF1) dependent down regulation of glutathione S-transferase A4 setting the stage for a molecular cascade of events that activates the c-JUN NH2-terminal kinase (JNK), an established regulator of insulin sensitivity. Moreover, we present new findings that demonstrate that the down regulation of GSTA4 is not merely a process observed in animal models of insulin resistance but also occurs selectively in obese, insulin resistant, but not obese, insulin sensitive humans thereby providing a molecular differentiation between obesity and insulin resistance. This application builds on recent evidence obtained in the Bernlohr, Griffin and Arriaga laboratories that functionally links oxidative stress to insulin resistance. These studies in sum lead to our central hypothesis: decreased expression of GSTA4 in adipocytes leads to increased carbonylation of multiple protein targets. Carbonylation in turn initiates a cascade of molecular events leading to mitochondrial dysfunction and ROS production. ROS production leads to the oxidation of Thioredoxin 2 (Trx2) and the activation of Trx2-ASK1-JNK/p38 signaling system contributing to insulin resistance. To test this hypothesis, the following four specific aims are proposed: Specific Aim 1. Evaluate mitochondrial protein carbonylation and identify target proteins. Specific Aim 2. Assess ROS production and mitochondrial electron transport system in cell culture and animal models. Specific Aim 3. Develop and characterize aP2-HA-GSTA4 transgenic mice maintained on low and high fat diets. Specific Aim 4. Characterize cellular metabolism and the Trx2-ASK1-JNK pathway in animal and cell culture models. PUBLIC HEALTH RELEVANCE: A variety of animal, cell culture and molecular studies have correlated increased oxidative stress and the accumulation of reactive oxygen species (ROS) to type 2 diabetes. While appreciated for years, it was unclear if oxidative stress / ROS was a casual or causal factor in the etiology of the disease. This application will profile new and compelling findings from our laboratories using animal and cell culture models that establish a molecular linkage between the antioxidant defense system in adipose cells with mitochondrial function, oxidative phosphorylation, signal transduction and the development of insulin resistance. We present new findings that demonstrate that the down regulation of GSTA4 is not merely a process observed in animal models of insulin resistance but also occurs selectively in obese, insulin resistant, but not obese, insulin sensitive humans thereby providing a molecular differentiation between obesity and insulin resistance. If the hypothesis is proven to be correct, the study would be immediately translatable to human biology and afford a new view of how type 2 diabetes may be combated.