Lipid peroxidation-induced chemical modifications of insulin signaling proteins

描述（由申请人提供）： 本研究的目的是描述2型糖尿病模型中干扰胰岛素信号通路的脂质过氧化机制。由于糖尿病中脂质过氧化作用增强，毒性终产物如4-羟基壬烯醛积累并可化学修饰胰岛素信号蛋白，从而导致胰岛素抗性的发展。一个新兴的假说涉及炎症和促炎阶段作为导致疾病中活性氧和氮物质（ROS/RNS）过度产生的致病因素，越来越多的证据表明诱导型一氧化氮合酶（iNOS）和有害的过氧亚硝酸盐参与其中。iNOS的表达也被大多数（如果不是全部的话）胰岛素抵抗诱导剂上调，因此大量的数据暗示了酶在胰岛素抵抗相关过程中的作用。我的初步数据表明，在1型和2型糖尿病中，脂质自由基在肝脏中形成。大量的蛋白质自由基形成， 4-羟基壬烯醛的积累是由羟基自由基的产生介导的;脂质自由基的形成和脂质过氧化反应是由iNOS过表达产生的羟基自由基引发的;这一发现表明过氧亚硝酸盐参与了初级氧化剂。此外，在2型糖尿病大鼠模型中也存在类似的脂质自由基产生模式，且iNOS显著参与;终产物4-羟基壬烯醛可能通过对胰岛素受体底物蛋白进行化学修饰来干扰胰岛素信号传导途径。在这个提议中，我打算进一步扩展这些初步研究，1 -研究在肥胖2型糖尿病模型中iNOS驱动的自由基依赖性脂质过氧化的启动作用; 2 -表征2型糖尿病动物中胰岛素抵抗进展的脂质过氧化驱动机制; 3 -研究潜在的药理学治疗以减轻和/或延迟2型糖尿病中脂质过氧化介导的损伤和胰岛素抵抗。这些问题构成了本提案中描述的工作的核心，我相信这将深刻影响我们对糖尿病，肥胖和胰岛素抵抗中氧化应激和自由基机制的理解。

DESCRIPTION (provided by applicant): Project summary The aim of this study is to characterize lipid peroxidation mechanisms that are interfering with the insulin signaling pathway in a type 2 diabetes model. As a result of enhanced lipid peroxidation in diabetes, toxic end- products such as 4-hydroxynonenal accumulate and may chemically modify the insulin signaling proteins, contributing to the development of insulin resistance. An emerging hypothesis relates inflammation and a proinflammatory stage as causative factors leading to the overproduction of reactive oxygen and nitrogen species (ROS/RNS) in the disease, with increasing evidence for the involvement of inducible nitric oxide synthase (iNOS) and the deleterious peroxynitrite. The expression of iNOS is upregulated by most, if not all, inducers of insulin resistance as well, and therefore considerable amount of data implies the role of the enzyme in insulin resistance-related processes. My preliminary data demonstrate that both in type 1 and type 2 diabetes, lipid radicals were formed in the liver. The extensive protein radical formation and 4- hydroxynonenal accumulation is mediated by hydroxyl radical production; the lipid radical formation and lipid peroxidation were initiated by the hydroxyl radical derived from iNOS overexpression; this finding suggests peroxynitrite involvement as a primary oxidant. Moreover, a similar pattern of lipid radical production exists in a type 2 diabetic rat model with significant iNOS involvement; and the end product 4-hydroxynonenal may interfere with the insulin signaling pathway by making chemical modification on the insulin receptor substrate protein. In this proposal, I intend to further extend these initial studies by 1 - investigating the role of iNOS- driven free radical-dependent initiation of lipid peroxidation in a model of obese type 2 diabetes; 2 - characterizing lipid peroxidation-driven mechanisms underlying the progression of insulin resistance in type 2 diabetic animals; 3 - investigating potential pharmacologic treatments to attenuate and/or delay lipid peroxidation-mediated damage and insulin resistance in type 2 diabetes. These questions compose the core of the work described in this proposal which I believe will profoundly impact our understanding of oxidative stress and free radical mechanisms in diabetes, obesity and insulin resistance.