6β-乙基-鹅去氧胆酸抑制肝脏脂肪酸转运治疗非酒精性脂肪肝的机制

In China, the increasing incidence of non-alcoholic fatty liver disease (NAFLD) has been well documented and listed on the top among the liver diseases. The different mechanisms contributing to NAFLD included that the increased hepatocellular uptake of Long Chain Fatty Acids （LCFA） occurs due to obesity. The free fatty acid transport protein 5 (FATP5), which is one of LCFA transportors, only expressed in livers of mice. FATP5 knockout mice exhibited lower levels of hepatic triglycerides due to a high-fat diet because of decreased high fat food intake but not regular chow intake. The molecular mechanisms to decrease the high fat food intake that FATP5 transports and regulates the hormone Oleoyl-Estrone (OE) whose structure is similar to free fatty acid beause the OE regulated the high fat food intake. Chenodeoxycholic acid (CDCA), 6β-ethyl-CDCA and deoxycholic acid (DCA) showed to be FATP5 inhibitors by high-throughput screening of inhibitors on FATP5 or FATP2 overexpressed 293 cell lines, but CDCA and 6α-ethyl-CDCA increased hepatic LCFA uptake within 20 minutes in mice, but 6β-ethyl-CDCA decrease the hepatic LCFA uptake. CDCA and 6α-ethyl-CDCA are the farnesoid X receptor （FXR） agonists. So, we speculate that the CDCA and 6α-ethyl-CDCA activated FXR and promoted hepatic uptake of LCFA. In this project, we will confirm that 6β-ethyl-CDCA is effect by targeting FATP5 for NAFLD treatment; We will discover the FXR signaling pathway that regulates hepatic uptake of LCFA with lentivirus FXR shRNA and FXR knock out mice for selecting the new therapeutic targets on the NAFLD in the future; We will prove the FATP5 transports OE into cells and liver for metablism by tracing fluereocent labeling OE in vitro and in vivo; We will combine the 6β-ethyl-CDCA and OE to treat the obecity and NAFLD to increase the efficacy of OE.

非酒精性脂肪肝（NAFLD）尚缺乏有效治疗靶点和药物，病理机制包括肝脏摄入长链脂肪酸（LCFA）过多。LCFA转运蛋白5（FATP5）只在肝表达，构建FATP5敲除小鼠，发现其自发减少进食高脂肪食物，改善了NAFLD。我们进一步筛选到鹅去氧胆酸（CDCA）、6β-乙基-鹅去氧胆酸(6β-e-CDCA)和去氧胆酸(DCA)是FATP5的抑制剂，发现DCA抑制FATP5改善了小鼠脂肪肝，但胆汁酸X受体（FXR）激动剂CDCA和6α-e-CDCA却促进小鼠肝脏摄入LCFA。本项目将在细胞水平研究胆汁酸激活肝FXR增强FATP5功能的信号通路，在转基因小鼠中研究6β-e-CDCA通过抑制FATP5转运LCFA功能和抑制类似于脂肪酸的激素油酰雌酮转运入肝代谢，治疗NAFLD和肥胖，从而明确肝内FATP5的上下游调控机制，为NAFLD治疗提供靶向FATP5的潜在药物和FXR信号通路中新的治疗靶点。

非酒精性脂肪肝病（NAFLD）尚缺乏有效治疗靶点和药物，病理机制包括肝脏摄入长链脂肪酸（LCFA）过多。LCFA转运蛋白5（FATP5）是肝脏脂肪酸转运蛋白之一，主要在肝表达，构建FATP5敲除小鼠，发现其自发减少进食高脂肪食物，改善了NAFLD。.本项目成功构建高表达hFATP5转基因小鼠模型，合成荧光标记的长链脂肪酸，为长链脂肪酸转运提供了良好的动物模型及研究手段。用高通量方法筛选出hFATP5小分子高效抑制物6β-乙酰-鹅去氧胆酸（e-CDCA），并在细胞水平验证了该分子的强效抑制hFATP5的脂肪酸转运。我们使用6a-e-CDCA治疗高脂肪饮食的hFATP5转基因小鼠，发现其能显著降低该小鼠的体重并持续低于对照组151天，转换为普通食物后小鼠体重恢复到高脂肪食物前水平。猜想其内在分子机制是激活法尼酯X受体（FXR）信号通路可增强FATP5的转运功能促进肝脏脂肪酸吸收，而6a-e-CDCA和脂肪酸竞争性抑制FATP5功能。在细胞水平验证此机制，用FXR激动剂CDCA和6a-e-CDCA可促进小鼠肝脏摄入长链脂肪酸，敲低FXR表达，可抑制这种促进作用。我们正用FXR（-/-）小鼠体内实验来验证这个猜想。