Role of CD40 in Obesity-Induced Adipose Tissue Inflammation & Insulin Resistance

描述(由申请人提供)：肥胖引起的炎症是胰岛素抵抗和2型糖尿病发病机制的一个促成因素。脂肪组织巨噬细胞(ATM)和脂肪组织T细胞(ATT)在肥胖期间都会积聚。ATM和ATT产生的促炎信号会削弱脂肪组织中的胰岛素作用。然而，对于ATT和ATM如何在肥胖期间启动和维持脂肪组织炎症并产生胰岛素抵抗缺乏明确的了解。我们小组正在探索一种假设，即脂肪组织中ATM和ATT之间的通信是塑造脂肪中炎症环境的核心。我们发现，在饮食诱导的肥胖过程中，内脏脂肪中CD40的表达增加，自动取款机表达CD40。CD40是一种跨膜糖蛋白，属于肿瘤坏死因子受体超家族。CD40的配体CD40L(或CD154)在活化的T淋巴细胞上高度表达。CD40-CD40L信号已被证明在T细胞启动、效应功能和启动T细胞介导的免疫中起关键作用。我们的初步数据支持一个模型，在该模型中，来自高脂饮食暴露的信号诱导ATM上的CD40促进CD4+ATT的激活和扩张。这一应用的中心假设是，CD40-CD40L通路介导ATM和ATT之间的通信，促进ATM激活，驱动抗原特异性的CD4+ATT的扩张，并在肥胖时诱导炎症和胰岛素抵抗。这项培训计划的目标是让学员严格测试这一模型，同时学习和应用免疫学技术来测量培养细胞和脂肪中的ATM功能和ATT反应。在目标1中，我们将确定脂肪细胞如何调节ATM中CD40的表达。具体地说，我们将检验脂肪细胞肥大和死亡激活ATM中TLR4和NF-：B信号通路以诱导CD40表达的工作假说。在目标2中，我们将研究CD40激活对M1和M2 ATM生物学的影响。这些实验将测试CD40激活是否诱导ATM的成熟和细胞因子的产生，以及CD40激活是否参与ATM对ATT的调节。在目标3中，我们将检验这一工作假设，即白细胞中CD40的激活是肥胖期间内脏脂肪中炎症信号产生的主要原因。拟议的实验将提供一个关于CD40-CD40L信号是否以及如何在肥胖诱导的炎症中起作用的明确理解。该培训方案专门为促进免疫学和新陈代谢领域的交叉培训而设计。受训人员将发展ATM生物学和肥胖引起的炎症调控方面的专业知识，学习与ATM和ATT调控相关的关键免疫学概念，并接受免疫学家和肥胖研究人员使用的最先进技术的培训。

DESCRIPTION (provided by applicant): Obesity-induced inflammation is a contributing factor in the pathogenesis of insulin resistance and Type 2 diabetes. Both adipose tissue macrophages (ATMs) and adipose tissue T cells (ATTs) accumulate during obesity. ATMs and ATTs produce pro-inflammatory signals that impair insulin action in adipose tissue. However, a clear understanding of how ATTs and ATMs communicate to initiate and sustain adipose tissue inflammation and generate insulin resistance during obesity is lacking. Our group is exploring the hypothesis that communication between ATMs and ATTs in adipose tissue is central to shaping the inflammatory environment in fat. We have found that CD40 expression is increased in visceral fat during diet-induced obesity and that ATMs express CD40. CD40 is a transmembrane glycoprotein belonging to the TNF receptor superfamily. The ligand for CD40, CD40L (or CD154), is highly expressed on activated T lymphocytes. CD40- CD40L signaling has been shown to be critical for T cell priming, effector function, and initiation of T cell- mediated immunity. Our preliminary data support a model in which signals derived from high fat diet exposure induce CD40 on ATMs to promote activation and expansion of CD4+ ATTs. The central hypothesis of this application is that the CD40-CD40L pathway mediates communication between ATMs and ATTs to promote ATM activation to drive expansion of antigen-specific CD4+ ATTs and induce inflammation and insulin resistance during obesity. The goal of this training proposal is for the trainee to rigorously test this model while learning and applying immunology techniques to measure ATM function and ATT responses in cultured cells and in fat. In Aim 1, we will determine how CD40 expression in ATMs is regulated by adipocytes. Specifically, we will test the working hypothesis that adipocyte hypertrophy and death activates TLR4 and NF-:B signaling pathways in ATMs to induce CD40 expression. In Aim 2, we will examine the effects of CD40 activation on the biology of M1 and M2 ATMs. The proposed experiments will test whether CD40 activation induced maturation and cytokine production by ATMs, and whether CD40 activation participates in the regulation of ATTs by ATMs. In Aim 3, we will test the working hypothesis that CD40 activation in leukocytes is principally responsible for the generation of inflammatory signals in visceral fat during obesity. The proposed experiments will provide a clear understanding as to whether and how CD40-CD40L signaling contributes to obesity- induced inflammation. The training proposal is specifically designed to promote cross training in the fields of immunology and metabolism. The trainee will develop expertise in ATM biology and regulation of obesity- induced inflammation, learn key immunological concepts relevant to the regulation of ATMs and ATTs, and receive training in state of the art techniques used by immunologists and obesity researchers.