Effects of Dietary Fat on the Hepatotoxicity of Environmental Arsenic

每三个美国成年人中就有一个肥胖，并患有某种形式的非酒精性脂肪肝 （NAFLD）。大多数肥胖个体会有脂肪变性（脂肪肝），但只有约20%的人会有 更严重的脂肪性肝炎（脂肪肝伴炎症和肝损伤）。目前还没有FDA批准的 治疗任何阶段的NAFLD。因此，至关重要的是，我们要了解 促进NAFLD从脂肪变性进展为脂肪性肝炎。我们之前的研究表明， 饮用砷污染的饮用水是NAFLD进展的重要危险因素。 初步的蛋白质组学分析表明，大量的蛋白质，控制在 在砷增强的NAFLD小鼠的肝脏中，HNF-4a的转录水平降低。 机制研究表明，这种锌指转录因子的表达没有改变，但 其DNA结合活性在翻译后水平受到抑制。已知HNF-4a是由翻译后调节的。 修饰（PTM），砷有可能影响锌结合，半胱氨酸氧化， 精氨酸甲基化和赖氨酸乙酰化。关于HNF-4a的PTM是如何调节的知之甚少，或者 这些调节过程的破坏如何导致肝脏疾病。为了跟进这些重要的 调查结果，目前的建议的目的是描绘的机制，环境砷 暴露促进了喂食西式饮食的小鼠从脂肪变性到脂肪性肝炎的进展， 富含饱和脂肪待检验的中心假设是HNF-4a介导的基因的改变 砷诱导的表达在NAFLD从脂肪变性到脂肪性肝炎的进展中起关键作用 in this model模型.这一假设将在三个具体目标中得到检验。首先，我们将定义特定的分子 砷与HNF-4a锌指结构域的相互作用。第二，我们将分析这些机制， 砷影响HNF-4a的PTM，以及这些变化如何转化为改变的DNA结合活性， 反式激活潜力第三，我们将确定小鼠肝脏HNF-4a的翻译后修饰， 高脂肪饮食和接触受砷污染的饮用水，并将这些变化与占用率联系起来 在参与脂质代谢和炎症的基因中的HNF-4a反应元件。这个型号的 炎性肝损伤与美国人口有关，在美国，高脂肪饮食是常见的， 砷暴露水平通常低于明显肝毒性的阈值。获得的新信息 从这些研究将描绘途径，被砷改变，这是重要的病因学 NAFLD。

One of every three American adults is obese and is afflicted with some form of non-alcoholic fatty liver disease (NAFLD). The majority of obese individuals will have steatosis (fatty liver), but only about 20% will have the more serious condition of steatohepatitis (fatty liver with inflammation and liver injury). There is still no FDA-approved therapy for any stage of NAFLD. Therefore, it is critical that we understand the multiple factors that promote progression from steatosis to steatohepatitis in NAFLD. Our previous studies have shown that consumption of arsenic-contaminated drinking water is an important risk factor for progression of NAFLD. Preliminary proteomic analysis demonstrated that the abundance of a number of proteins that are controlled at the transcriptional level by HNF-4a was decreased in the livers of mice with arsenic-enhanced NAFLD. Mechanistic studies showed that the expression of this zinc finger transcription factor was not altered, but that its DNA binding activity was inhibited at the post-translational level. HNF-4a is known to be regulated by posttranslational modifications (PTMs), and arsenic has the potential to affect zinc binding, cysteine oxidation, arginine methylation and lysine acetylation. Very little is known about how PTMs of HNF-4a are regulated, or how disruption of these regulatory processes contributes to liver disease. To follow up on these important findings, the objective of the current proposal is to delineate the mechanisms by which environmental arsenic exposure promotes the progression from steatosis to steatohepatitis in mice fed a Western-style diet that is high in saturated fat. The central hypothesis to be tested is that alterations in HNF-4a-mediated gene expression induced by arsenic play a critical role in the progression of NAFLD from steatosis to steatohepatitis in this model. This hypothesis will be tested in three Specific Aims. First, we will define the specific molecular interactions of arsenic with the zinc finger domain of HNF-4a. Second, we will analyze the mechanisms by which arsenic affects PTMs of HNF-4a, and how these changes translate into altered DNA binding activity and transactivation potential. Third, we will define the post-translational modifications of hepatic HNF-4a in mice fed a high fat diet and exposed to arsenic-contaminated drinking water, and relate these changes to the occupancy of HNF-4a-response elements in genes involved in lipid metabolism and inflammation. This model of inflammatory liver injury is relevant to the United States population, where high fat diets are common and arsenic exposure levels are typically below the threshold for overt hepatotoxicity. The new information obtained from these studies will delineate pathways that are altered by arsenic and that are important in the etiology of NAFLD.