Chemerin, Complement, and Insulin Resistance

描述(由申请人提供)： 代谢综合征影响了所有退伍军人患者的25%。Chmerin是一种趋化因子和脂肪因子，其受体CMKLR1在脂肪形成和脂肪细胞代谢中起重要作用。CMKLR1-/-小鼠出现糖耐量异常。血清趋化蛋白升高与2型糖尿病(T2D)相关，而趋化蛋白基因中的SNP与T2D风险增加相关。Chmerin是作为一种非活性前体分泌的，其激活和失活依赖于其C-末端的特定蛋白水解酶。我们已经针对不同的人和小鼠趋化蛋白亚型开发了特定的ELISA。活化的补体C3a和C5a在胰岛素抵抗(IR)的发生发展中起重要作用。羧肽酶B2(CPB2)通过使补体C3a和C5a失活来调节体内补体活性。CPB2也激活趋化蛋白。我们已经在不同的炎症性疾病小鼠模型中使用了CPB2-/-小鼠。我们假设补体和趋化蛋白的激活在小鼠和人类的IR和代谢综合征的发展中都是关键的。我们推测，CPB2的缺失将导致补体的激活增加，从而导致IR的发生。具体目的1.测定肥胖小鼠脂肪组织和外周血中C3a、C5a及不同趋化蛋白亚型的水平。我们的初步研究表明，喂食HFD的肥胖小鼠血浆和皮下脂肪组织中趋化蛋白156S的水平增加，趋化蛋白156是小鼠体内最活跃的趋化蛋白形式。我们将在一项为期24周的HFD诱导的肥胖研究中检查补体和趋化蛋白激活的时间进程，然后限制卡路里，并与其他炎症生物标记物的关系。我们还将评估脂肪细胞中补体和趋化蛋白激活之间是否存在串扰。特定目的2.测定人体脂肪组织和外周血中C3a、C5a及不同趋化蛋白亚型的水平。2.1接受减肥手术和术后6个月的肥胖患者。我们的初步研究表明，接受减肥手术的患者血浆、大网膜和皮下脂肪组织中趋化蛋白最活跃的形式--趋化蛋白157S的水平升高。他们还提高了脂肪组织中的C5a水平。我们将检测100名接受减肥手术的患者和50名非糖尿病对照组患者的血浆和脂肪组织中补体和不同趋化蛋白亚型的水平。我们将把这些水平与其他细胞因子和脂肪因子联系起来。2.2评估趋化蛋白异构体和补体作为IR生物标志物的潜力。血浆样本将来自胰岛素抵抗(肥胖或瘦)或胰岛素敏感(肥胖或瘦)的患者，他们的胰岛素敏感性或抵抗状态已被严格定义。我们将测定四组各25个样本中C3a、C5a和趋化蛋白亚型的水平，以评估这些参数是否可以作为IR的生物标志物。具体目的3.确定CPB2-/-小鼠是否易发生HFD诱导的IR。为了测试CPB2-/-小鼠是否对IR更敏感，WT和CPB2-/-小鼠将被置于高脂饮食或低脂饮食8周。IR将通过葡萄糖和胰岛素耐受，以及肝脏脂肪变性来评估。如果CPB2-/-小鼠容易发生IR，我们将尝试使用C3a或C5a受体拮抗剂来逆转表型。不同趋化蛋白亚型的水平也将被测定。我们是唯一拥有特定趋化蛋白ELISA的小组，这种ELISA允许研究人类和小鼠体内趋化蛋白水平的变化。这将是第一次确定CPB2在IR中的作用的研究。这些研究将提供有关IR中补体和趋化蛋白激活的新信息，并可能为代谢综合征的风险评估和确定新的治疗靶点带来创新的诊断工具。

DESCRIPTION (provided by applicant): Metabolic syndrome affects 25% of all Veteran's patients. Chemerin, a chemoattractant and an adipokine, and its receptor CMKLR1, are important in adipogenesis and adipocyte metabolism. CMKLR1-/- mice develop glucose intolerance. Elevated serum chemerin is associated with type 2 diabetes (T2D), and a SNP in the chemerin gene correlates with an increased risk of T2D. Chemerin is secreted as an inactive precursor, and its activation and inactivation is dependent on specific proteolytic cleavages at its C-terminus. We have developed specific ELISAs for the different human and mouse chemerin isoforms. Activated complement C3a and C5a are important in the development of insulin resistance (IR). Carboxypeptidase B2 (CPB2) regulates in vivo complement activity by inactivating both C3a and C5a. CPB2 also activates chemerin. We have utilized CPB2-/- mice in different mouse models of inflammatory disease. We hypothesize that activation of both complement and chemerin are critical in the development of IR and metabolic syndrome in mice and humans. We speculate that the absence of CPB2 will result in increased activation of complement and the development of IR. Specific Aim 1. Determine the levels of C3a, C5a and the different chemerin isoforms in adipose tissues and peripheral blood in a mouse model of obesity. Our preliminary studies show that HFD-fed obese mice have increased levels of chemerin 156S, the most active form of chemerin in mice, in the plasma and subcutaneous adipose tissues. We will examine the time course of complement and chemerin activation over a 24-week HFD-induced obesity study, followed by calorie restriction, in relationship to other inflammatory biomarkers. We will also assess if there is crosstalk between complement and chemerin activation in adipocytes. Specific Aim 2. Determine the levels of C3a, C5a and the different chemerin isoforms in adipose tissues and peripheral blood in humans. 2.1 Obese patients undergoing bariatric surgery and 6-month post-surgery. Our preliminary studies show that patients undergoing bariatric surgery have elevated levels of chem157S, the most active form of chemerin in humans, in the plasma and omental and subcutaneous adipose tissues. They also have elevated C5a levels in adipose tissue. We will examine the levels of complement and different chemerin isoforms in the plasma and adipose tissue of 100 patients undergoing bariatric surgery and 50 nondiabetic control patients. We will correlate these levels with other cytokines and adipokines. 2.2 Assess the potential of chemerin isoforms and complement as a biomarker for IR. Plasma samples will be obtained from patients who are either insulin-resistant (obese or lean), or insulin- sensitive (obese or lean), whose insulin sensitivity or resistance status had been rigorously defined. We will determine the levels of C3a, C5a and chemerin isoforms in 25 samples from each of the four groups to assess whether these parameters can act as a biomarker for IR. Specific Aim 3. Determine if the CPB2-/- mice are predisposed to the development of HFD-induced IR. To test whether CPB2- /- mice are more susceptible to IR, WT and CPB2-/- mice will be placed on HFD or low-fat diet for 8- weeks. IR will be assessed by glucose and insulin intolerance, and hepatic steatosis. If CPB2-/- mice are predisposed to IR, we will attempt to reverse the phenotype using either a C3a or C5a receptor antagonist. Levels of different chemerin isoforms will also be determined. We are the only group that has specific chemerin ELISAs, which permits study of in vivo changes of chemerin levels in humans and mice. This will be the first study to define the role of CPB2 in IR. These studies will provide new information on the activation of complement and chemerin in IR, and may lead to innovative diagnostic tools for the risk assessment of metabolic syndrome and the identification of new therapeutic targets.