Mediators and Modifiers of NF-kappaB in Insulin Resistance

描述(由申请人提供)：这项资助的前一个周期假设炎症性IKKbeta/NF-kappaB通路在肥胖和饮食诱导的胰岛素抵抗的发病机制中发挥关键作用。我们现在知道，肥胖和高脂饮食(HFD)会激活脂肪和肝脏中的这一途径，而脂肪和肝脏中核因子-kappaB的激活会导致胰岛素抵抗，至少部分是由于促炎细胞因子(IL-6、抵抗素、IL-1β、肿瘤坏死因子-α)的产生。在动物和/或人类中，从遗传或药物上抑制IKKβ和NF-kappaB，以及细胞因子中和，可以逆转胰岛素抵抗。在患者身上看到的炎症标志物的升高很容易在啮齿动物模型中复制，饮食和遗传诱导的胰岛素抵抗。在啮齿动物和人类中，这些都是相反的，同时胰岛素抵抗的改善和甘油三酯、游离脂肪酸和葡萄糖水平的显著降低。为了继续开发和测试这些假说，我们现在提出了一个全面的计划，以确定调节核因子-kappaB信号和胰岛素抵抗的细胞内蛋白。除上述细胞因子外，HFD诱导的其他核因子-kappaB以及脂肪和肝脏中的肥胖与代谢综合征和动脉粥样硬化(CRP、PAI-1、SAA-1、VCAM1、ICAM1、iNOS和COX2)有关。作为本提案的主题，我们还看到A20、Ikki/epsilon和IkappaBzeta在肥胖/HFD啮齿动物模型的脂肪和肝脏中有结构性的、依赖于NF-kappaB的表达。这些通常可诱导的核因子-kappaB信号调节因子和/或介体在宿主防御中具有有趣的功能。我们计划确定它们是否也在胰岛素抵抗中起作用。A20诱导通过改变上游信号蛋白的泛素化来限制核因子-kappaB信号；核因子-kappaB诱导抑制胰岛素信号转导的丝氨酸/苏氨酸激酶Ikki/epsilon的表达；而与IkappaBalpha不同，IkappaBzeta选择性地增加一些有趣的核因子-kappaB靶标的表达，如IL-6。本申请中介绍的实验确定了这些蛋白质在脂肪和肝脏中的体内作用，通过观察组织特异性效应和器官间相互作用，进一步深入探讨了高脂/肥胖诱导胰岛素抵抗的机制。这些发现将提高我们对亚急性“炎症”在胰岛素抵抗、T2D和代谢综合征中的作用的理解，并可能为治疗干预确定新的和更具选择性的靶点。

DESCRIPTION (provided by applicant): The previous cycle of this grant hypothesized a critical role for the inflammatory IKKbeta/NF-kappaB pathway in the pathogenesis of obesity- and diet-induced insulin resistance. We now know that the pathway is activated in fat and liver by obesity and high fat diet (HFD) and that activation of NF-kappaB in fat and liver causes insulin resistance, at least in part due to the production of proinflammatory cytokines (IL-6, resistin, IL-1beta, TNF-alpha). Inhibition of IKKbeta and NF-kappaB, either genetically or pharmacologically, and cytokine neutralization reverse insulin resistance in animals and/or humans. Elevations in inflammatory markers that are seen in patients are readily reproduced in rodent models dietary and genetically induced insulin resistance. These are reversed in both rodents and humans in parallel with improvements in insulin resistance and dramatic reductions in triglyceride, free fatty acid and glucose levels. To continue developing and testing these hypotheses, we now propose a comprehensive plan to identify intracellular proteins that modulate NF-kappaB signaling and insulin resistance. In addition to the cytokines listed above, other NF-kappaB targets induced by HFD and obesity in fat and liver are associated with the metabolic syndrome and atherosclerosis (CRP, PAI-1, SAA-1, VCAM1, ICAM1, iNOS and COX2). As the subject of this proposal we also see constitutive, NF-kappaB dependent expression of A20, IKKi/epsilon, and IkappaBzeta, in fat and liver of obese/HFD rodent models. These normally inducible regulators and/or mediators of NF-kappaB signaling have intriguing functions in host defense. We plan to determine if they also function in insulin resistance. A20 induction limits NF-kappaB signaling by altering the ubiquitination of upstream signaling proteins; NF-kappaB induces the expression of IKKi/epsilon, a Ser/Thr kinase that inhibits insulin signaling; and IkappaBzeta, unlike IkappaBalpha, selectively increases expression of a few interesting NF-kappaB targets such as IL-6. Experiments presented in this application determine the in vivo roles of these proteins in fat and liver, delving further into the mechanisms of HFD/obesity-induced insulin resistance by looking both at tissue-specific effects and inter-organ cross-talk. The findings will improve our understanding of the role of subacute 'inflammation' in insulin resistance, T2D and the metabolic syndrome, and may identify new and more selective targets for therapeutic intervention.