REACTIVE OXYGEN SPECIES (ROS), MITOCHONDRIAL DYSFUNCTION AND T2D (PROT 1)

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 2型糖尿病(T2 DM)是一种胰岛素抵抗状态，其特征是高血糖、血浆FFA水平升高、胰岛素靶组织(肌肉和肝脏)和β细胞中脂肪过度堆积。血浆FFA/细胞内脂质含量升高会对肌肉的胰岛素敏感性和β细胞功能产生有害影响，这被称为“脂毒性”。我们和其他人已经证实，T2 DM患者骨骼肌中参与氧化磷酸化和Krebs循环的多种线粒体基因表达减少，并在T2 DM患者中观察到遗传易感性、胰岛素抵抗的线粒体基因表达。我们假设存在一个自我永久化的负反馈循环，线粒体缺陷(遗传的或后天的)导致FACoA氧化受损和ROS生成增加。通过激活炎症通路(核因子-kB、p38MAPK、JNK)，胞内FACoA和ROS增加，导致胰岛素信号转导通路的关键元件丝氨酸磷酸化，从而导致胰岛素抵抗。 “糖毒性”也与T2 DM肌肉胰岛素抵抗和进行性胰岛细胞衰竭的发展有关。在人类中，血糖或氨基葡萄糖的慢性生理性升高会导致肌肉中的胰岛素抵抗，而在啮齿类动物中，氨基葡萄糖输注会损害线粒体基因的表达，抑制氧化磷酸化，并减少基础能量消耗。我们推测，细胞的慢性葡萄糖超载，就像慢性脂质超载一样，会导致ROS生成增加，并激活抑制胰岛素信号的炎症途径。 在本研究中，我们将研究：(1)线粒体功能障碍、ROS/RNS生成增加以及炎症途径的氧化应激激活在瘦型和肥胖型2型糖尿病个体、糖尿病父母的正常糖耐量胰岛素抵抗后代和肥胖正常糖耐量个体肌肉胰岛素信号受损和胰岛素抵抗的发生发展中的作用；(2)长期(3天)单输脂(使血浆FFA倍增)、单用氨基葡萄糖(和葡萄糖)、单用氨基葡萄糖(和葡萄糖)加脂肪对健康受试者肌肉线粒体功能、ROS/RNS的产生、应激激活的炎症通路、胰岛素信号转导和胰岛素敏感性的影响；(3)PPAR-y激动剂(吡格列酮)或抗氧化剂(α-硫辛酸)治疗是否可以改善T2 DM患者和正常糖耐量、胰岛素抵抗后代的线粒体功能障碍，减少ROS/RNS的产生，抑制应激激活的炎症通路，改善胰岛素信号转导，逆转胰岛素抵抗，增强β细胞功能。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Type 2 diabetes mellitus (T2DM) is an insulin resistant state characterized by hyperglycemia, elevated plasma FFA levels, and excessive lipid accumulation in insulin target tissues (muscle and live) and in beta cells. Elevated plasma FFA/intracellular lipid content exerts deleterious effects on muscle insulin sensitivity and beta cell function and this has been referred to a "lipotoxicity". We and others have demonstrated decreased expression of multiple mitochondrial genes involved in oxidative phosphorylation and the Krebs cycle in skeletal muscle from T2DM and genetically predisposed, insulin resistant mitochondrial gene expression observed in T2DM. We postulate that there is a self perpetuating negative feedback cycle whereby a mitochondrial defect (genetic or acquired) leads to impaired FACoA oxidation and increased generation of ROS. The resultant increases in cyctosolic FACoA and ROS, through activation of inflammatory pathways (NF-kB, p38 MAPK, JNK), causes serine phosphorylation of key elements of the insulin signaling cascade causing insulin resistance. "Glucotoxicity" also has been implicated in the development of muscle insulin resistance and progressive beta cell failure in T2DM. In humans a chronic physiologic increase in plasma glucose or glucosamine causes insulin resistance in muscle and, in rodents, glucosamine infusion impairs mitochondrial gene expression, inhibits oxidative phosphorylation, and reduces basal energy expenditure. We postulate that chronic glucose overload of cells, like chronic lipid overload, leads to increased ROS generation and activation of inflammatory pathways that inhibit insulin signaling. In the present study we shall examine: (1) the role of mitochondrial dysfunction, increased generation of ROS/RNS, and oxidative stress-activation of inflammatory pathways in the development of impaired muscle insulin signaling and insulin resistance in lean and obese type 2 diabetic individuals, in the normal-glucose-tolerant insulin-resistant offspring of two diabetic parents, and in obese normal-glucose-tolerant individuals; (2) the effect of chronic (3 day) infusion of lipid alone (to double plasma FFA), glucosamine (and glucose) alone, and glucosamine (and glucose) plus lipid on muscle mitochondrial function, generation of ROS/RNS, stress-activated inflammatory pathways, insulin signaling and insulin sensitivity in healthy subjects; (3) whether treatment with a PPAR-y agonist (pioglitazone) or an antioxidant (alpha lipoic acid) can amerliorate mitochondrial dysfunction, reduce the generation of ROS/RNS, inhibit stress-activated inflammatory pathways, improve insulin signaling, reverse insulin resistance, and enhance beta cell function in T2DM patients and in normal glucose-tolerant, insulin resistant offspring.