Does Chronic Low-Level Lead (Pb) Exposure Increase Diabetes Susceptibility?

环境健康领域一个重要且尚未解决的问题是，暴露于常见的环境毒物是否会增加患糖尿病的风险，特别是与其他常见的代谢应激因素（如肥胖）结合时。虽然铅（Pb）暴露和血液水平在过去十年中有所下降，肥胖和铅暴露之间的相互作用是一个相关的问题，在大部分美国人口的环境和生活方式的因素与暴露于持久性环境毒物，如铅共存。了解有毒物质暴露和其他可能促进代谢不稳定和疾病的身体和社会压力之间的合作相互作用，将是巨大的意义，在划定疾病/有毒物质病因，以及建立早期干预措施，为这些人群的风险最大。本项目的目标是表征铅暴露对代谢应激啮齿动物糖尿病风险的影响，并确定铅影响代谢平衡的体外机制。肥胖大鼠的初步研究结果表明，铅暴露促进代谢不稳定和糖尿病。体外培养肝细胞的数据表明，铅干扰胰岛素抑制肝葡萄糖产生的能力，这将有助于体内高血糖症的发展。这些结果共同形成了本提案的假设：与肥胖相结合，铅暴露增加糖尿病的易感性和/或严重性。有两个具体目标：1）在已建立的肥胖啮齿动物模型Zucker糖尿病肥胖（ZDF）大鼠中表征铅暴露导致糖尿病的程度; 2）建立体外细胞模型以研究铅影响肝脏中胰岛素信号传导和葡萄糖稳态的机制。肝癌细胞和原代肝细胞制备的瘦和肥胖的ZDF大鼠将被用来确定铅影响胰岛素敏感性和葡萄糖代谢的代谢正常和应激细胞的机制。将使用mRNA分离和基因表达分析的标准体外技术来建立该体外细胞模型。

An important and unresolved question in the environmental health field is whether exposure to common environmental toxicants increases the risk of developing diabetes, especially in combination with other common metabolic stressors, such as obesity. Although lead (Pb) exposure and blood levels have declined over the past decade, the interaction between obesity and Pb exposure is a relevant issue in large sections of the US population where environmental and lifestyle factors co-exist with exposure to persistent environmental toxicants, such as Pb. Understanding the cooperative interaction between toxicant exposure and additional physical and social stressors that may promote metabolic instability and disease will be of enormous significance in delineating disease/toxicant etiology as well as establishing earlier interventions for those populations most at risk. The goals of this project are to characterize the effect of Pb exposure on diabetes risk in metabolically stressed rodents and to identify the in vitro mechanisms by which Pb affects metabolic balance. Preliminary findings in obese rats suggest that Pb exposure promotes metabolic instability and diabetes. In vitro data from cultured hepatocytes show that Pb interferes with the ability of insulin to suppress hepatic glucose production, which would contribute to the development of hyperglycemia in vivo. Together these results form the hypothesis of this proposal: In combination with obesity, Pb exposure increases diabetes susceptibility and/or severity. There are two specific aims: 1) Characterize the extent to which Pb exposure causes diabetes in a well-established rodent model of obesity, Zucker Diabetic Fatty (ZDF) rats, and 2) establish in vitro cellular models to study the mechanism by which Pb affects insulin signaling and glucose homeostasis in liver. Hepatoma cells and primary hepatocytes prepared from lean and obese ZDF rats will be used to identify the mechanism by which Pb affects insulin sensitivity and glucose metabolism in metabolically normal and stressed cells. Standard in vitro techniques for mRNA isolation and gene expression analysis will be utilized to establish this in vitro cell model.