Hormonal control of NASH development and progression

摘要/摘要 非酒精性脂肪性肝病(NAFLD)代表了一系列的病理，从简单的脂肪变性到 非酒精性脂肪性肝炎(伴有肝细胞损伤的纳氏脂肪变性)伴或不伴纤维化。NAFLD是 在肥胖和糖尿病患者中普遍存在，是心血管疾病的独立危险因素 和死亡率。在VA患者群体中，肥胖/糖尿病/NASH的患病率高于 对一般人群来说，这是一种主要的临床和经济负担。目前还没有经过验证的医学疗法 预防和治疗纳什。因此，了解导致NASH的机制是很重要的 开发，目标是为未来的药物开发确定新的目标。当前应用程序 已发表的生长激素抑制肝脏脂肪的临床和实验证据综述 蓄积，防止肝脏损伤。我们已发表和未发表的数据表明GH介导了这些效应 通过增强STAT5B活性直接在肝细胞水平发挥作用。概述了将使用 肝细胞特异型腺病毒相关载体(AAV)在成年小鼠体内传递转基因以测试 假设减少肝细胞特异性GHR介导的转录因子STAT5B的激活， 直接促进成人NASH的发生和肝细胞STAT5B的选择性增强 活动将防止和逆转NASH。以下具体目标(SA)将检验这一假设。SA1- 确定增强肝细胞STAT5B活性是否可以减缓或预防饮食诱导的脂肪变性和NASH 有或无肝细胞GHR信号和IGF1产生的发展。SA2-确定是否 在饮食诱导的脂肪肝中观察到的肝脏pSTAT5B的减少是由于肝脏GH的发展 抵抗。SA3-确定增强肝细胞STAT5B活性是否可以逆转既定饮食- 诱导性NASH。检查的终点包括：1)肝脏脂肪变性和损伤的组织病理学评估；2) 气相色谱-液质联用法测定肝脏脂质含量及组成 3)免疫印迹法检测肝脏GH受体介导的下游信号的激活状态 分析；4)评估肝脏脂肪和葡萄糖加工中重要基因的表达 蛋白质印迹分析；5)评估全身胰岛素敏感性和糖耐量，以及， 用间接量热法测定葡萄糖/脂肪的利用率。完成这些研究将提供有关以下方面的新信息 生长激素如何直接调控肝细胞功能，抑制脂肪变性，预防肝损伤。这些信息可能 揭示治疗NASH的新药物靶点。

SUMMARY/ABSTRACT Non-alcoholic fatty liver disease (NAFLD) represents a spectrum of pathologies ranging from simple steatosis to non-alcoholic steatohepatitis (NASH – steatosis with hepatocellular injury) with or without fibrosis. NAFLD is prevalent in obese and diabetic patients, and represents an independent risk factor for cardiovascular disease and mortality. Within the VA patient population, the prevalence of obesity/diabetes/NASH is higher than in the general population and represents a major clinical and economic burden. There are no proven medical therapies to prevent and treat NASH. Therefore, it is important to understand the mechanisms that contribute to NASH development, with the goal to identify novel targets for future drug development. The current application overviews published clinical and experimental evidence that growth hormone (GH) suppresses hepatic fat accumulation and prevents liver injury. Our published and unpublished data indicate GH mediates these effects directly at the level of the hepatocyte by enhancing STAT5B activity. Studies are outlined that will use hepatocyte-specific adenoviral-associated vector (AAV) delivery of transgenes in adult mice to test the HYPOTHESIS- Reduction in hepatocyte-specific GHR-mediated activation of the transcription factor, STAT5B, directly contributes to adult-onset NASH development and selective enhancement of hepatocyte-STAT5B activity will prevent and reverse NASH. The following Specific Aims (SA) will test this hypothesis. SA1- Determine if augmenting hepatocyte STAT5B activity can slow or prevent diet-induced steatosis and NASH development in the presence or absence of hepatocyte GHR-signaling and IGF1 production. SA2- Determine if the reduction in hepatic pSTAT5B, observed in diet-induced fatty livers, is due to the development of hepatic GH resistance. SA3 - Determine if enhancing the activity of hepatocyte STAT5B can reverse established diet- induced NASH. Endpoints examined include: 1) histopathologic assessment of hepatic steatosis and injury; 2) determination of hepatic lipid content and composition by gas chromatography- and liquid chromatography mass spectroscopy; 3) activation status of hepatic GH receptor-mediated downstream signals by Western blot analysis; 4) evaluation of hepatic expression of genes important in lipid and glucose processing by qPCR and Western blot analysis; 5) assessment of whole body insulin sensitivity and glucose tolerance, as well as, glucose/lipid utilization by indirect calorimetry. Completion of these studies will provide new information regarding how GH directly controls hepatocyte function to inhibit steatosis and prevent liver injury. This information could reveal novel drug targets to treat NASH.