Therapeutic Opportunities of Targeting Tissue Factor Signaling in Obesity

描述(申请人提供)：肥胖症在西方社会已经达到流行的程度。然而，其发病机制尚不完全清楚，治疗选择仍然有限。我们的目标是评估一种新的方法，即抑制组织因子(TF)信号转导的抗体，用于治疗肥胖和代谢综合征。除了促凝作用外，TF在炎症和血管生成中还具有不依赖凝血的功能。因此，VIIa与Tf的结合也通过G蛋白偶联的蛋白酶激活受体-2(PAR2)产生直接信号。高脂饮食(HFD)喂养的C57BL/6J肥胖小鼠模型模拟了人类的摄食行为(吞噬过度)、体重增加/能量代谢以及以胰岛素抵抗和2型糖尿病为特征的代谢综合征的发展。我们发现TF和PAR2在HFD诱导的肥胖小鼠的脂肪组织(AT)中共表达，并在脂肪组织中升高。此外，缺乏Tf(TF4CT小鼠)或PAR2细胞质结构域的小鼠可以免受高脂饮食诱导的肥胖和随后发生的胰岛素抵抗的影响。在肥胖的野生型小鼠中，一种阻断Tf-VIIa结合的抗体可以迅速改善胰岛素抵抗。表达人转铁蛋白的肥胖转基因小鼠在接受特异性阻断转铁蛋白信号的单抗治疗时，胰岛素抵抗也得到了改善。这项资助的总体目标是确定转铁蛋白信号在肥胖发病机制中的作用，长期目标是推进这一途径的合理药理学靶向，以对抗肥胖及其并发症。在目标1中，我们将使用野生型、TF4CT、PAR2-/-和双缺陷TF4CT/PAR2-/-小鼠以及从这些基因敲除小鼠分离的骨髓(BM)嵌合体和脂肪细胞来表征TF-VIIa-PAR2信号支持肥胖发展的作用、细胞靶点和机制。在目标2中，我们将使用多种方法，包括TF4CT和PAR2-/-小鼠的BM嵌合体以及分离的AT巨噬细胞来验证巨噬细胞TF-PAR2信号在脂肪炎症和胰岛素抵抗中的作用。在目标3中，我们将描述抗转铁蛋白治疗策略逆转肥胖和胰岛素抵抗的机制和有效性。评估在表达人转铁蛋白的转基因小鼠中选择性抑制直接转铁蛋白-VIIa-PAR2信号的单抗的效果，将确定这种策略的治疗潜力，该策略具有最低限度的出血并发症风险。这些研究将为TF信号在肥胖中的作用提供基本的见解，并在这些途径中测试一种创新的治疗方法，以改善肥胖的代谢并发症。

DESCRIPTION (provided by applicant): Obesity has reached epidemic proportions in western societies. However, mechanisms contributing to its pathology are incompletely understood, and, treatment options remain limited. Our goal is to evaluate a novel approach, antibodies that inhibit tissue factor (TF) signaling, in the treatment of obesity and the metabolic syndrome. In addition to its procoagulant role, TF has coagulation-independent functions in inflammation and angiogenesis. Thus, binding of VIIa to TF also leads to direct signaling via the G-protein coupled protease activated receptor-2 (PAR2). The high fat diet (HFD) fed C57BL/6J mouse model of obesity simulates the human condition, including feeding behavior (hyperphagia), weight gain/energy metabolism, and the development of the metabolic syndrome characterized by insulin resistance and type 2 diabetes. We show that TF and PAR2 are co expressed in adipose tissues (AT) and elevated in adipose tissues of HFD-induced obese mice. Moreover, mice lacking the cytoplasmic domain of TF (TF4CT mice) or PAR2 are protected from HFD- induced obesity and the subsequent development of insulin resistance. In obese wild-type mice, an antibody that blocks TF-VIIa binding rapidly improves insulin resistance. Insulin resistance was also ameliorated in obese transgenic mice that express human TF when they were treated with a monoclonal antibody that specifically blocked TF signaling. The overall goal of this grant is to characterize the contributions of TF signaling to the pathogenesis of obesity with the long term goal to advance a rational pharmacological targeting of this pathway to combat obesity and its complications. In Aim 1 we will use Wild type, TF4CT , PAR2-/-, and double deficient TF4CT /PAR2-/- mice together with bone marrow (BM) chimeras and adipocytes isolated from these knock-out mice to characterize the contribution, cellular targets and mechanisms by which TF-VIIa- PAR2 signaling supports the development of obesity. In Aim 2 we will use a variety of approaches including BM chimeras of TF4CT and PAR2-/- mice and isolated AT macrophages to validate that macrophage TF-PAR2 signaling contributes to adipose inflammation and insulin resistance. In Aim 3 we will characterize the mechanism and efficacy of anti-TF treatment strategies in reversing obesity and insulin resistance. Evaluating the effect of monoclonal antibodies that selectively inhibit direct TF-VIIa-PAR2 signaling in transgenic mice expressing human TF will determine the therapeutic potential of such a strategy that carries minimal risk of bleeding complications. These studies will provide fundamental insights into the role of TF signaling in obesity, and test an innovative therapeutic approach in these pathways to improve metabolic complications of obesity.