Mechanisms of cadmium-induced dysglycemia

项目摘要/摘要 镉(Cd)是一种普遍存在的环境和工业污染物，目前在美国排名第七 EPA/ATSDR危险物质优先清单，是一种已知的人类致癌物，会导致肾脏、肝脏 和骨骼损伤。CD与糖尿病(DM)和糖尿病前期有关，在流行病学和 实验研究。在一项对美国人群的研究中，25%的糖尿病患者或糖尿病前期患者患有 尿镉水平升高。目前尚不清楚镉是如何扰乱血糖水平的。然而，CD曝光是 与职业性接触和镉接触者的低血清胰岛素水平有关 在动物实验中抑制葡萄糖刺激的胰岛素分泌。对于大部分糖尿病受损患者来说 在葡萄糖刺激下，胰岛素的分泌发生在II型糖尿病的进展中。建议的总体目标是 该项目旨在确定镉导致葡萄糖刺激的胰岛素释放受损的机制。正常 胰岛素分泌和胰腺β细胞功能依赖于细胞间的黏附；尤其重要的是 钙依赖的细胞黏附分子E-钙粘附素的作用。镉已被证明扰乱E-钙粘附素 肾脏中介导的细胞-细胞黏附。初步研究将确定暴露剂量和持续时间的范围 在分离的胰岛和胰腺β细胞系MIN6中导致坏死和/或凋亡的细胞死亡的Cd。 后续的研究将确定葡萄糖刺激的胰岛素释放受损是否是对 剂量和持续时间下镉诱导的全身性氧化应激反应或能量状态改变(ADP/ATP) 低于导致细胞死亡的暴露。活细胞成像研究将用于敏感的 检测氧化应激介质产生的变化的荧光团。目标二中概述的研究 将决定Cd导致E-钙粘附素介导的细胞-细胞黏附与葡萄糖相关的丧失的能力- 刺激分离的胰岛和MIN6细胞释放胰岛素。更多的研究将检验这些影响 与E-钙粘蛋白的胞外区和siRNA结合的E-钙粘素抗体实验性地破坏 细胞-细胞黏附实验确定镉对抑制葡萄糖刺激的胰岛素是否有协同作用 放手。目标三将确定镉是否导致电压门控钙通道阻断，从而导致随后的 在分离的胰岛和MIN6细胞中，葡萄糖刺激的胰岛素释放受损。更多的研究将确定 在存在或不存在的情况下，Cd对葡萄糖刺激的胰岛素释放有协同作用 L类电压门控型钙通道阻滞剂。此外，活细胞成像将与荧光团一起使用， 选择性检测细胞内镉、锌或钙的变化。在目标二和目标三中，体内研究使用了 具有良好特征的长期镉中毒模型将用于验证体外研究结果。总的来说，这些 研究将确定镉的糖尿病致病作用的机制，镉是一种广泛存在的环境污染物 这与糖尿病和糖尿病前期有关。

Project Summary/Abstract Cadmium (Cd) is a ubiquitous environmental and industrial pollutant that currently ranks seventh on the US EPA/ATSDR Priority List of Hazardous Substances and is a known human carcinogen that causes kidney, liver and bone damage. Cd is associated with diabetes mellitus (DM) and prediabetes in epidemiological and experimental studies. In a study of the US population, 25% of individuals that were diabetic or prediabetic had elevated urinary Cd levels. It is unknown how Cd disrupts blood glucose levels. However, Cd exposure is associated with low serum insulin levels in individuals with occupational exposure and Cd has been shown to impair glucose-stimulated insulin secretion in animal studies. For a large subsection of patients with DM impaired glucose-stimulated insulin, secretion occurs in the progression of type II DM. The overall aim of the proposed project is to determine the mechanism by which Cd causes impaired glucose-stimulated insulin release. Normal insulin secretion and pancreatic β-cell function are dependent upon cell-cell adhesion; especially important is the role of the calcium-dependent cell adhesion molecule, E-cadherin. Cd has been shown to disrupt E-cadherin mediated cell-cell adhesion in the kidney. Initial studies will establish a range of doses and duration of exposure of Cd that result in necrotic and/or apoptotic cell death in isolated islets and the pancreatic β-cell line, MIN6. Subsequent studies will be determined if impaired glucose-stimulated insulin release is a response to a generalized Cd-induced oxidative stress response or altered energy status (ADP/ATP) at doses and durations of exposure below those that cause cell death. Live cell imaging studies will be utilized with sensitive fluorophores to detect changes in the production of mediators of oxidative stress. Studies outlined in Aim two will determine the ability of Cd to cause loss of E-cadherin mediated cell-cell adhesion in relation to glucose- stimulated insulin release in isolated islets and the MIN6 cell line. Additional studies will examine the effects of E-cadherin antibodies that bind to the extracellular domain and siRNA of E-cadherin to experimentally disrupt cell-cell adhesion to determine if there are synergistic effects of Cd on inhibiting glucose-stimulated insulin release. Aim three will determine if Cd causes voltage-gated calcium channel blockade resulting in subsequent impaired glucose-stimulated insulin release in isolated islets and MIN6 cells. Additional studies will determine if there are synergistic effects of Cd to impair glucose-stimulated insulin release in the presence or absence of the L-type voltage-gated calcium channel blockers. Also, live cell imaging will be utilized with fluorophores that selectively detect changes of intracellular Cd, zinc or calcium. In Aims two and three, in vivo studies using a well-characterized model of long term Cd poisoning will be used to verify the in vitro findings. Overall, these studies will identify the mechanism of the diabetogenic effects of Cd, a widespread environmental contaminant that is associated with DM and prediabetes.