Endothelial Basis of Obesity-induced Insulin Resistance

项目摘要/摘要 Fc受体(FCR)调节细胞内信号转导免疫效应细胞中的免疫球蛋白G结合 系统。我们之前已经发现，被称为FcγRIIB的抑制性FCR也在骨骼中表达 肌肉微血管内皮细胞和全局FcγRIIB缺失小鼠免受高脂饮食的保护 高脂蛋白(HFD)诱导的胰岛素抵抗。为了探讨内皮细胞FcγRIIB在胰岛素代谢中的作用，我们 通过与FcγRIIB杂交获得内皮细胞特异性缺失FcγRIIB的小鼠品系 (FcγRIIBfl/f1)与VE Cherin-Cre小鼠(FcγRIIBf1/f1：VECad-Cre)，喂以对照饲料或高脂饲料。 我们发现Fc-γRIIBfl/fl：VECad-Cre小鼠对高脂饮食诱导的外周胰岛素抵抗有保护作用 以及葡萄糖向骨骼肌输送的障碍。此外，我们还发现，免疫球蛋白 从饲喂HFD的野生型小鼠(HFD-Ig G)分离，但不从对照组饲喂饲料的小鼠(Con-Ig G)分离到Ig G， FcγRIIB基因转移到缺乏内源性免疫球蛋白的小鼠(B-/-小鼠)诱导胰岛素抵抗 与Con-Ig G相比，HFD-Ig G在其Fc结构域中的唾液酸化程度较低。治疗 N-乙酰-D-甘露糖胺(ManNAc)增加蛋白唾液酸化的野生型小鼠的研究 高脂饲料诱导的胰岛素抵抗。此外，从肥胖型2型糖尿病(T2 DM)中分离出免疫球蛋白 患者，但不是来自非T2 DM患者，通过FcγRIIB在B-/-小鼠中诱导胰岛素抵抗。基于 这些新发现，拟议项目的总体目标是确定免疫球蛋白唾液酸化是如何 饮食诱导肥胖的调节失调及内皮Fc、γ、RIIB在发病机制中的作用 使用小鼠模型和培养细胞研究与DIO相关的胰岛素抵抗。目标1将决定如何 HFD减少了免疫球蛋白的唾液酸化，主要集中在B细胞中调节免疫球蛋白唾液酸化的过程。我们 还将确定ManNAc如何预防HFD诱导的胰岛素抵抗。目标2将决定如何 内皮FcγRIIB介导高脂饮食诱导的外周胰岛素抵抗，验证了以下假设 HFDIg G激活内皮细胞FcγRIIB启动细胞内信号转导 胰岛素的血管内皮细胞转运。目标3将确定免疫球蛋白唾液酸化及其诱导能力 小鼠的胰岛素抵抗与人类的DIO相关的胰岛素抵抗有关，使用现有的 一组肥胖和胰岛素敏感的受试者。使用高度翻译的方法， 我们将测试FcγRIIb在内皮细胞中的新概念和B细胞中Ig G的修饰是至关重要的 参与胰岛素抵抗和T2 DM的发病机制。我们预计，新的知识 Gain将带来新的预防和治疗措施来对抗胰岛素抵抗， 肥胖和其他慢性炎症性疾病的特征。

Project Summary/Abstract Fc receptors (FcR) modulate intracellular signaling upon IgG binding in the effector cells in the immune system. We have previously found that the inhibitory FcR known as FcγRIIB is also expressed in skeletal muscle microvascular endothelium, and that global FcγRIIB null mice are protected from high-fat diet (HFD)-induced insulin resistance. To explore the role of endothelial FcγRIIB in insulin metabolism, we generated the mouse strain lacking FcγRIIB specifically in endothelial cells by crossing floxed FcγRIIB (FcγRIIBfl/fl) with VE Cadherin-Cre mice (FcγRIIBfl/fl:VECad-Cre), and fed them with control diet or HFD. We found that FcγRIIBfl/fl:VECad-Cre mice are protected from HFD-induced peripheral insulin resistance and from impairment of glucose delivery to the skeletal muscle. Furthermore, we discovered that IgG isolated from HFD-fed wild-type mice (HFD-IgG), but not IgG from control diet-fed mice (Con-IgG), induces insulin resistance when transferred into mice lacking endogenous IgG (B-/- mice) in an FcγRIIB dependent manner, and that HFD-IgG is less sialylated in its Fc domain compared to Con-IgG. Treatment of wild-type mice with N-Acetyl-D-mannosamine (ManNAc) that increases protein sialylation ameliorated HFD-induced insulin resistance. Moreover, IgG isolated from obese type 2 diabetes mellitus (T2DM) patients, but not from non-T2DM subjects, induced insulin resistance in B-/- mice via FcγRIIB. Based upon these novel findings, the overall goal of the proposed project is to determine how IgG sialylation is dysregulated in diet-induced obesity (DIO) and how endothelial FcγRIIB contributes to the pathogenesis of DIO-related insulin resistance using both mouse models and cultured cells. Aim 1 will determine how HFD decreases sialylation of IgG, focusing on the process in B cells that modulates IgG sialylation. We will also determine how ManNAc prevents HFD-induced insulin resistance. Aim 2 will determine how endothelial FcγRIIB mediates HFD-induced peripheral insulin resistance, testing the hypothesis that activation of endothelial FcγRIIB by HFD-IgG initiates intracellular signaling that leads to attenuation of transendothelial transport of insulin. Aim 3 will determine whether IgG sialylation and its ability to induce insulin resistance in mice are associated with DIO-related insulin resistance in humans, using existing cohorts of subjects with a range of obesity and insulin sensitivity. Using a highly translational approach, we will test the novel concept that FcγRIIB in endothelium and modification of IgG in B cells are critically involved in the pathogenesis of insulin resistance and T2DM. We anticipate that the new knowledge gained will lead to novel preventative and treatment measures to combat the insulin resistance that characterizes obesity and other chronic inflammatory conditions.