The role of gap junction coupling in regulating islet dysfunction in type2 diabetes

项目摘要/摘要 2型糖尿病(T2D)是系统性红斑狼疮后胰腺胰岛素释放减少的结果 胰岛素抵抗。朗格汉斯胰岛内产生胰岛素的β细胞负责 维持血糖稳态；T2D结果显示胰岛素释放功能障碍 β细胞功能和质量降低。β-细胞的胰岛素分泌受协调调节 胰岛上的电信号，这是由包含间隙连接的连接蛋白-36建立的 (GJS)。GJS确保有组织的钙信号，导致正常的胰岛素分泌和β-细胞 生死存亡。初步数据显示，GJS在暴露于亲水化合物时容易解偶联。 炎症环境和对循环游离脂肪酸(FFAs)升高的反应。vt.给出 T2D的发病与脂肪细胞来源的循环促炎因子的增加有关 细胞因子和游离脂肪酸，我们假设游离脂肪酸和促炎细胞因子诱导胰岛 FFA受体(GPR40)介导的GJ解偶联功能障碍，最终导致改变 Ca~(2+)信号、胰岛素分泌减少和β细胞死亡。此外，我们假设 在这种情况下防止GJ解偶联可以防止糖尿病引起的胰岛功能障碍。 为了验证这些假设，小鼠和人类的胰岛都将暴露在浓度为 模拟糖尿病前期环境的细胞因子和棕榈酸酯。FFA信令机制将 在用GPR40的化学拮抗剂/激动剂和已知的GPR40处理的胰岛中描绘 效应分子(包括磷脂酶-C和蛋白激酶-Cδ通路)。我们还将 检查从糖尿病前期瘦素受体缺陷小鼠(“db/db”)分离的胰岛，这些小鼠建立了T2D模型。在……里面 在T2D中预防GJ解偶联和相关的胰岛功能障碍的努力，我们将合成 针对Cx36基序调节反应偶联的新型抑制性模拟多肽 对脂肪酸/细胞因子的影响。在每一种情况下，都将结合使用最先进的显微镜技术 已建立的方法通过测量GJ偶联，钙信号， 胰岛素分泌和β细胞活性。这些研究的结果将定义 胰岛功能障碍发生在疾病的早期，可能是T2D发病的诱因。我们 还将勾勒出保存β的新型治疗干预措施的机会-细胞团、胰岛素 2型糖尿病患者的分泌功能和改善血糖控制。

Project Summary/Abstract Type2 diabetes (T2D) is the result of reduced insulin release from the pancreas following systemic insulin resistance. Insulin-producing β-cells within the islets of Langerhans are responsible for maintaining blood glucose homeostasis; and dysfunctional insulin release in T2D results from reduced β-cell function and mass. Insulin secretion from β-cells is regulated by coordinated electrical signaling across the islet, which is established by Connexin-36 containing gap junctions (GJs). GJs ensure organized calcium signaling, resulting in proper insulin secretion and β-cell survival. Preliminary data shows that GJs are prone to uncoupling upon exposure to a pro- inflammatory environment and in response to elevated circulating free fatty acids (FFAs). Given that T2D onset is associated with increases in both adipocyte-derived circulating pro-inflammatory cytokines and FFAs, we hypothesize that FFAs and pro-inflammatory cytokines induce islet dysfunction via FFA receptor (GPR40)-mediated GJ uncoupling, which ultimately induces altered Ca2+ signaling, reduced insulin secretion and β-cell death. Furthermore, we hypothesize that preventing GJ uncoupling under these conditions can prevent diabetes-induced islet dysfunction. To test these hypotheses, both mouse and human islets will be exposed to concentrations of cytokines and palmitate that mimic the pre-diabetic environment. FFA signaling mechanisms will be delineated in islets treated with chemical antagonists/agonists of GPR40 and known GPR40 effector molecules (including phospholipase-C and protein kinase-Cδ pathways). We will also examine islets isolated from pre-diabetic, leptin receptor deficient mice (“db/db”) that model T2D. In an effort to prevent GJ uncoupling and associated islet dysfunction in T2D, we will synthesize novel inhibitory mimetic peptides targeted against Cx36 motifs that regulate coupling in response to FFAs/cytokines. In each case, state-of-the-art microscopy techniques will be used in conjunction with established methods to assess islet function by measuring GJ coupling, calcium signaling, insulin secretion and β-cell viability. Results from these studies will define mechanisms by which islet dysfunction occurs in early in the disease that could be precipitating factors to T2D onset. We will also delineate opportunities for novel therapeutic interventions to preserve β-cell mass, insulin secretory function and improve glycemic control in type2 diabetic patients.