Endothelin-1 in Obesity and Insulin Resistance

项目摘要 胰岛素抵抗(IR)在美国是一个主要的健康问题。它可以预防II型糖尿病，通常出现在 肥胖患者，两者都是心血管疾病的主要危险因素。目前， 导致IR的机制尚不完全清楚。ET-1是一种血管活性多肽，主要由 内皮细胞。在肥胖患者中，它会增加，并与IR相关。ET-1升高是对 低氧，这发生在肥胖者身上。它激活两种受体，ETA和ETB，这两种受体通常 在生理上相互对立。我们的初步数据表明，抑制啮齿动物的ETB受体 从基因或药理上讲，可改善胰岛素耐受性，降低空腹血糖。这 血糖控制的改善与血浆脂联素和脂联素的增加有关 和过氧化物酶体增殖物激活受体γ(PPAR-γ)基因。此外，脂肪细胞特异性ETB 功能增强的小鼠加剧了对高脂饮食的葡萄糖耐量，而脂肪细胞 与对照胎相比，ETB基因敲除小鼠的血糖和胰岛素耐受性有所改善。这些 数据表明，脂肪组织可能是ET-1诱导的胰岛素信号减少的靶点。一直以来 先前研究表明，激活培养脂肪细胞上的ETB受体可抑制阿司匹林的抗脂作用 胰岛素。此外，阻断ETB受体可改善睡眠呼吸暂停啮齿动物模型的胰岛素敏感性。 这些数据表明，肥胖患者体内ET-1的升高可能通过ETB促进胰岛素抵抗。 受体。因此，我们假设肥胖引起的组织缺氧促进ET-1/ETB受体 脂肪激活导致脂肪细胞IR、PPAR-γ抑制和脂联素释放减少 通过脂肪细胞，从而引起肌肉和肝脏组织的IR。为了验证这一假设，我们将在 体内和体外技术。首先，利用培养的脂肪细胞，我们将确定ETB的激活是否 受体抑制PPAR-γ，减少脂联素的分泌，引起脂肪细胞的胰岛素抵抗。下一首, 我们将在饮食诱导的肥胖和胰岛素抵抗模型中使用临床批准的ET-1受体抑制剂，我们 将利用我们实验室生产的两种新型小鼠模型，使我们能够过度表达或敲除 ETB。为了验证这一假设，我们将测试以下具体目标： 具体目标1：验证ETB受体激活直接抑制胰岛素信号转导的假设 并通过抑制PPAR-γ减少脂联素的产生。 特定目标2：验证脂肪细胞上ETB受体激活促进胰岛素抵抗的假设 通过抑制PPAR-γ和减少脂联素的释放。 具体目标3：验证ETB受体阻断可增加血浆脂联素和改善脂联素的假设 肥胖小鼠的胰岛素抵抗。

Project Summary Insulin resistance (IR) is a major health problem in the U.S. It precludes type II diabetes and is often present in patients suffering from obesity, both being major risk factors for cardiovascular disease. Currently, mechanisms leading to IR are not fully understood. ET-1 is a vasoactive peptide primarily released by endothelial cells. It is increased in patients with obesity and associated with IR. ET-1 is elevated in response to hypoxia, which occurs in individuals with obesity. It activates two receptors, ETA and ETB, which typically oppose each other physiologically. Our preliminary data indicate that inhibiting ETB receptors in rodents, either genetically or pharmacologically, improves insulin tolerance and reduces fasting blood glucose. This improvement in glucose control is associated with an increase in plasma adiponectin and adipose adiponectin and peroxisome proliferator-activated receptor gamma (PPAR-γ) mRNA. In addition, adipocyte specific ETB gain of function mice have exacerbated glucose intolerance in response to high fat feeding, while adipocyte ETB knockout mice have improved glucose and insulin tolerance compared to floxed control littermates. These data suggest the adipose tissue as a possible target for ET-1 induced reduction in insulin signaling. It has been previously shown that activation of ETB receptors on cultured adipocytes inhibits the anti-lipolytic effects of insulin. Furthermore, blockade of ETB receptors improves insulin sensitivity in a rodent model of sleep apnea. These data suggest that increased ET-1 observed in patients with obesity may promote IR via the ETB receptor. Thus, we hypothesize that that obesity induced tissue hypoxia promotes ET-1/ETB receptor activation in adipose leading to IR on adipocytes, PPAR-γ inhibition and reduced Adiponectin release by adipocytes thereby causing IR in muscle and liver tissue. To test this hypothesis, we will utilize both in vivo and in vitro techniques. First, using cultured adipocytes, we will determine whether activation of ETB receptors inhibits PPAR-γ, reduces adiponectin secretion, and causes insulin resistance on adipocytes. Next, we will used clinically approved inhibitors of ET-1 receptors in a model of diet induced obesity and IR, and we will utilize two novel mouse models that were produced by our lab that allow us to over-express or knockout the ETB. To test this hypothesis, the following specific aims will be tested: Specific aim 1: To test the hypothesis that ETB receptor activation directly inhibits insulin signaling on adipocytes and reduces adiponectin production by inhibiting PPAR-γ. Specific aim 2: To test the hypothesis that ETB receptor activation on adipocytes promotes insulin resistance by inhibiting PPAR-γ and reducing adiponectin release in mice. Specific aim 3: To test the hypothesis that ETB receptor blockade increases plasma adiponectin and improves insulin resistance in obese mice.