Mediators and Modifiers of NF-kappaB in Insulin Resistance

描述（由申请人提供）：本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发病机制中的关键作用。我们现在知道，肥胖和高脂肪饮食（HFD）会激活脂肪和肝脏中的这一途径，脂肪和肝脏中NF-kappaB的激活会导致胰岛素抵抗，至少部分原因是促炎细胞因子（IL-6、抵抗素、il -1 β、tnf - α）的产生。基因或药理学上抑制ikkβ和NF-kappaB，以及细胞因子中和可逆转动物和/或人类的胰岛素抵抗。在患者中观察到的炎症标志物升高很容易在啮齿动物模型中重现，饮食和遗传诱导的胰岛素抵抗。这些在啮齿类动物和人类身上都是相反的，同时胰岛素抵抗得到改善，甘油三酯、游离脂肪酸和葡萄糖水平显著降低。为了继续发展和测试这些假设，我们现在提出了一个全面的计划，以确定调节NF-kappaB信号和胰岛素抵抗的细胞内蛋白。除上述细胞因子外，HFD和肥胖在脂肪和肝脏中诱导的其他NF-kappaB靶点与代谢综合征和动脉粥样硬化相关（CRP、PAI-1、SAA-1、VCAM1、ICAM1、iNOS和COX2）。作为本提案的主题，我们还发现在肥胖/HFD啮齿动物模型的脂肪和肝脏中，A20、IKKi/epsilon和IkappaBzeta的组成性、NF-kappaB依赖性表达。这些通常可诱导的NF-kappaB信号调节因子和/或介质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NF-kappaB信号；NF-kappaB诱导IKKi/epsilon的表达，IKKi/epsilon是一种抑制胰岛素信号传导的丝氨酸/苏氨酸激酶；而IkappaBzeta与IkappaBalpha不同，它选择性地增加了一些NF-kappaB靶点（如IL-6）的表达。本应用程序中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串扰，进一步研究了HFD/肥胖诱导的胰岛素抵抗的机制。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，并可能确定新的、更有选择性的治疗干预靶点。

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.