Metabolic Characterization of the Novel Adipokine CTRP3

描述（由申请人提供）： 肥胖及其相关的II型糖尿病已经成为美国巨大的医疗负担， 导致每年花费数十亿美元来治疗这些代谢紊乱。需要大量的研究来了解肥胖相关的胰岛素抵抗和糖尿病的根本原因，以便有效地治疗这些疾病。Acrp 30/Adiponectin是由脂肪组织产生的胰岛素增敏多聚体蛋白，在调节全身葡萄糖和脂质代谢中起主要作用。等位基因多态性和血清脂联素水平降低与糖尿病和代谢综合征密切相关。本实验室最近发现了一个与脂联素同源的分泌蛋白家族，命名为Clq/TNF相关蛋白1-10（CTRP 1 -10）。我们已经表明，这个家族的一些成员，CTRP 1和CTRP 9，能够降低体内血糖水平，并激活AMPK和Akt信号通路在培养肌管。自从我加入Wong博士的实验室以来，我的研究重点是使用分子，生物化学和体内方法来表征CTRP 3的功能和调节。在我的研究过程中，我确定了两种特定的CTRP 3亚型（CTRP 3A和CTRP 3B），这是由基因的选择性剪接引起的。当同时表达时，CTRP 3A和CTRP 3B形成异源三聚体和异源寡聚体;这种物理复合物显著防止CTRP 3B蛋白水解裂解。I表明瘦素和炎性细胞因子调节CTRP 3的转录和蛋白水平。I证明CTRP 3蛋白的循环水平在雌性小鼠中较高，并且其水平在雌性小鼠中也显著较高。 肥胖（ob/ob）小鼠与瘦对照相比。使用纯化的重组蛋白，我表明，CTRP 3增强胰岛素激活小鼠成肌细胞中Akt信号通路的作用，此外，将重组CTRP 3注射到小鼠体内显著降低了它们的血糖水平。这些结果沿着CTRP 3与脂联素的结构同源性，表明CTRP 3具有重要的代谢功能。该提案的总体目标是确定CTRP 3的代谢功能和作用机制。我们的总体假设是CTRP 3增加胰岛素敏感性，从而增强葡萄糖代谢并促进骨骼肌增殖。我将使用体外（基于细胞培养）和体内（转基因过表达和重组蛋白注射）方法来研究CTRP 3的代谢功能。预计这项研究将加深我们对脂肪组织分泌因子（统称为脂肪因子）如何协调全身能量平衡的了解，从而为治疗代谢障碍提供新的见解。

DESCRIPTION (provided by applicant): Obesity and its associated type II diabetes have become a huge medical burden in the United States, resulting in billions of dollars being spent yearly to treat these metabolic disorders. Much research is needed to understand the underlying cause of obesity-linked insulin resistance and diabetes in order to effectively treat these disorders. Acrp30/Adiponectin is an insulin-sensitizing, multimeric protein produced by adipose tissue that plays a major role in regulating whole body glucose and lipid metabolism. Allelic polymorphism and reduced serum adiponectin levels are tightly linked to diabetes and metabolic syndrome. Our laboratory has recently discovered a family of ten novel secreted proteins homologous to adiponectin, designated as Clq/TNF-related proteins 1-10 (CTRP1-10). We have shown that some members of this family, CTRP1 and CTRP9, are able to reduce blood glucose levels in vivo and activate AMPK and Akt signaling pathways in culture myotubes. Since I joined Dr. Wong's laboratory, my research focuses on characterizing the function and regulation of CTRP3 using molecular, biochemical, and in vivo approaches. In the course of my study, I identified two specific isoforms of CTRP3 (CTRP3A and CTRP3B) that resulted from alternative splicing of the gene. When expressed concurrently, CTRP3A and CTRP3B form heterotrimers and heterooligomers; this physical complex markedly prevents CTRP3B from proteolytic cleavage. I showed that leptin and inflammatory cytokines modulate the transcript and protein levels of CTRP3.1 demonstrated that the circulating levels of CTRP3 protein are higher in female mice and its levels are also significantly higher in obese (ob/ob) mice compared to lean controls. Using purified recombinant protein, I showed that CTRP3 potentiates the action of insulin in activating the Akt signaling pathway in mouse myoblasts, and furthermore injection of recombinant CTRP3 into mice significantly lowered their blood glucose levels. These results along with the structural homology of CTRP3 to adiponectin suggest important metabolic function for CTRP3. The overall goal of this proposal is to detemnine the metabolic function and mechanisms of action of CTRP3. Our overall hypothesis is that CTRP3 increases insulin sensitivity and thus enhances glucose metabolism and promote skeletal muscle proliferation. I will use both in vitro (cell culture-based) and in vivo (transgenic over-expression and recombinant protein injection) approaches to investigate the metabolic function of CTRP3. It is anticipated that this study will advance our knowledge on how adipose tissuesecreted factors (collectively termed adipokine) coordinate systemic energy balance and thus provide novel insights to treat metabolic disorders.