AMPK/SHP通路在GLP-1R（胰高糖素样肽-1受体）激动剂抑制肝脏糖异生和脂肪沉积中的机制探讨

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes on chronic liver damage, characteristics of diffuse hepatocytes steatosis and fibrosis. The mortality of NAFLD patients is significantly higher than normal population. NAFLD is closely associated with insulin resistance. In previous study, we found AMP-activated protein kinase (AMPK) expression decreased, hepatocytes lipogenesis increased and hepatic lipid output reduced in high-fat induced diabetic rats. Inflammation was also involved in the pathogenesis of NAFLD. Most recently, we found that glucagon-like peptide-1 receptor (GLP-1R) agonist could alleviate hepatic lipid accumulation in high-fat diet fed db/db mice..AMPK/samll heterodimer partner (SHP) pathway is a important signal pathway on regulating hepatic glucose and lipid metabolism. Activated AMPK prompted SHP expression, then inhibit hepatic gluconeogenesis and lipogenesis. SHP also inhibited NF-kB pathway and lessened inflammation, suggested that AMPK/SHP pathway may retard the progression of NAFLD by inhibiting inflammatory response. In this study, we will investigate if GLP-1R agonist can inhibit hepatic inflammatory response, gluconeogenesis and lipid accumulation on NAFLD db/db mice or cultured human hepatoma cell lines -HepG2 in vitro. Moreover, we will determine if the benificial effects of GLP-1R agonist was dependent on AMPK/SHP pathway by AMPK or SHP recombinant adenovirus transfection and RNA interference.

非酒精性脂肪性肝病（NAFLD）是慢性肝脏损害最常见的原因之一，以弥漫性肝细胞脂肪变性为主要特征，死亡率显著高于普通人群。NAFLD与胰岛素抵抗密切相关。我们前期的研究表明：高脂饮食可诱导糖尿病大鼠肝脏腺苷酸活化蛋白激酶（AMPK）表达下降，肝脏脂肪合成增加且输出减少；炎症反应也参与了NAFLD的病理发生。最近，我们发现胰高糖素样肽-1受体（GLP-1R）激动剂能缓解高脂饮食喂养的db/db小鼠肝脏脂肪积聚。.AMPK/SHP通路是调节肝脏葡萄糖和脂肪代谢的重要信号通路。AMPK激活使SHP表达增加，抑制肝糖异生和脂肪合成。SHP还可抑制炎症反应。本研究中，我们将探讨在NAFLD动物或体外培养的人类肝细胞中,GLP-1R激动剂是否能抑制肝脏炎症反应、肝糖异生和脂肪沉积；通过使用重组腺病毒转染和RNA干扰等技术手段，进一步明确GLP-1R激动剂的肝脏保护作用是否依赖于AMPK/SHP通路。

背景：.非酒精性脂肪性肝病（NAFLD）是慢性肝脏损害最常见的原因之一，死亡率显著高于普通人群。目前，临床上尚缺乏针对NAFLD的有效治疗措施。最近，有研究发现胰高糖素样肽-1（GLP-1R）能缓解NAFLD。我们前期数据亦表明GLP-1受体激动剂（GLP-1RA）能减轻高脂喂养的小鼠肝脏脂肪积聚。.主要研究内容：.1. 高脂喂养对小鼠或高脂培养对HepG2细胞脂质含量、糖脂代谢酶、AMPK/SHP和炎症信号通路的影响；.2. GLP-1RA干预能否呈剂量或时间依赖性缓解高脂导致的肝细胞糖脂代谢和炎症变化；.3. 通过过表达或沉默SHP基因、Compound C抑制AMPK，探讨AMPK/SHP信号通路在NAFLD进展中的作用。.重要结果：.1. 高脂处理可导致小鼠肝脏或肝细胞脂肪积聚和炎症反应；.2. GLP-1RA抑制脂肪合成和炎症反应、促进脂解和β氧化，呈剂量依赖性缓解肝细胞脂肪积聚；.3. AMPK激活和SHP抑制是GLP-1RA缓解NAFLD进展的原因之一，抑制AMPK可逆转GLP-1RA的作用。.关键数据：.1. GLP-1RA通过激活AMPK、抑制SHP和SREBP-1c表达，缓解肝细胞糖异生和脂肪合成增加，促进脂肪酸β氧化，呈剂量和时间依赖性减轻高脂引起的肝细胞脂肪积聚；.2. SHP过表达使肝细胞脂肪含量增加、糖异生和脂肪合成增加、脂肪酸β氧化减少，SHP沉默则引起相反变化；.3. GLP-1RA可抑制高脂引起的肝细胞炎症反应，且依赖于AMPK和SHP；.4. AMPK抑制剂Compound C可抑制GLP-1RA引起的AMPK磷酸化，提示GLP-1RA的肝脏保护作用依赖于AMPK活化。.科学意义：.GLP-1RA能通过调控肝脏AMPK/SHP信号通路，激活AMPK、抑制SHP，进而抑制肝糖异生、减少脂肪合成、增加脂肪酸 β 氧化，抑制肝细胞炎症信号通路，延缓或阻断NAFLD的进展。本研究结果为临床治疗NAFLD提供了实验基础。