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

项目总结/摘要 2型糖尿病（T2 D）是由于全身性糖尿病后胰腺胰岛素释放减少所致。 胰岛素抵抗胰岛内产生胰岛素的β细胞负责 维持血糖稳态; T2 D中胰岛素释放功能障碍由以下原因引起： β细胞功能和质量降低。β细胞的胰岛素分泌受协调的 通过含有间隙连接的连接蛋白-36建立的跨越胰岛的电信号 （GJs）。GJ确保有组织的钙信号传导，导致适当的胰岛素分泌和β细胞 生存初步数据显示，GJ在暴露于亲- 炎症环境和响应于升高的循环游离脂肪酸（FFA）。给定 T2 D发作与脂肪细胞来源的循环促炎因子和 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 通过FFA受体（GPR 40）介导的GJ解偶联功能障碍，最终诱导改变 Ca 2+信号传导、胰岛素分泌减少和β细胞死亡。此外，我们假设， 在这些条件下防止GJ解偶联可以防止糖尿病诱导的胰岛功能障碍。 为了检验这些假设，小鼠和人胰岛都将暴露于浓度为 细胞因子和棕榈酸酯，模拟糖尿病前期环境。FFA信号机制将 在用GPR 40的化学拮抗剂/激动剂和已知的GPR 40 效应分子（包括磷脂酶-C和蛋白激酶-C δ途径）。我们还将 检查分离自糖尿病前期、瘦素受体缺陷型小鼠（“db/db”）的胰岛，所述小鼠模拟T2 D。在 为了防止GJ解偶联和T2 D相关的胰岛功能障碍，我们将合成 靶向Cx 36基序的调节应答偶联的新型抑制性模拟肽 到FFA/细胞因子。在每种情况下，都将结合使用最先进的显微镜技术 通过测量GJ偶联，钙信号传导， 胰岛素分泌和β细胞活力。这些研究的结果将确定机制， 胰岛功能障碍发生在疾病的早期，可能是T2 D发病的促发因素。我们 还将描述新的治疗干预的机会，以保护β细胞群，胰岛素 分泌功能和改善2型糖尿病患者的血糖控制。

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.