HSP70-FTO轴在非酒精性脂肪性肝病中的作用及机制研究

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing year by year and showing younger-age trend, has become the most common liver disease.The accumulation of fatty acids and triacylglycerols in the liver is the prerequisite and basis for the occurrence of NAFLD, but the specific molecular mechanism is still unclear.Our previous study found that HSP70 and FTO were up-regulated in high fat-induced mouse liver tissue and palmitate-induced steatosis model.In vitro confocal experiments revealed that HSP70 promoted FTO nuclear transfer as molecular chaperones on high fat. Further studies showed that down-regulation of hepatic HSP70 expression by HSP70 shRNA-related adenovirus can significantly improve the degree of hepatic steatosis. In addition, vitro studies found that FTO promoted lipid synthesis of HepG2 hepatocytes.Based on the above findings,we hypothesize that HSP70 may be involved in the pathogenesis of NAFLD through FTO.In order to prove this hypothesis, we overexpress and silence HSP70 or FTO in hepatocytes respectively by lentivirus and adeno-associated virus in vitro or in vivo to observe their effects on liver lipid synthesis and accumulation. Furthermore, HSP70 gene overexpression and FTO gene interference were used to further confirm whether HSP70 is involved in the pathogenesis of NAFLD through FTO. Finally, we study the interaction between HSP70 and FTO through confocal microscopy, Co-IP and GST-pull down techniques ,and reveal the role of HSP70 in the pathogenesis of NAFLD and provide new ideas and targets for clinical treatment of NAFLD.

非酒精性脂肪性肝病（NAFLD）是最常见的肝脏疾病。三酰甘油沉积是NAFLD病理基础，但分子机制尚不明确。课题组前期研究发现，在高脂喂养肥胖小鼠的肝脏及棕榈酸诱导的HepG2肝细胞中热休克蛋白70（HSP70）和肥胖相关基因（FTO）表达均显著上调。利用HSP70shRNA下调肥胖小鼠肝脏HSP70能显著改善肝脏脂质沉积。共聚焦等实验提示HSP70参与FTO核内转移，而FTO促进肝细胞脂质合成。基于上述结果，我们提出HSP70可能通过FTO参与NAFLD的发生。为证明该假说，本课题通过病毒载体在体内外过表达或沉默HSP70或FTO，观察两者对肝脂质沉积的影响。再利用HSP70过表达和FTO干扰验证HSP70通过FTO参与肝脂质沉积；最后，用GST-pull down、Co-IP等技术证实HSP70与FTO相互作用。本课题将揭示HSP70在NAFLD发病中的作用和机制，为其治疗提供新靶点。

非酒精性脂肪性肝病（NAFLD）是目前最常见的肝脏疾病，但其发生机制尚不清楚。本课题的旨在探讨HSP70-FTO轴在NAFLD中的作用和机制。在研究中我们发现：1）HSP70促进肝内脂质沉积：HSP70在体内外NAFLD模型中表达升高，过表达HSP70促进肝内脂质沉积，而沉默HSP70抑制脂质沉积；2）HSP70与FTO关系：HSP70与FTO之间相互作用，抑制FTO的泛素化及其降解，并促进FTO的核转移；3）FTO促进肝内脂质沉积：FTO在体内外NAFLD模型中表达升高，过表达FTO促进肝内脂质沉积，而沉默FTO抑制脂质沉积；4）FTO通过抑制PPARα发挥作用：FTO抑制PPARα表达，激活后者可逆转FTO促进肝细胞脂质沉积作用；5）TRIM21是FTO上游的泛素酶：TRIM21与FTO存在直接相互作用，促进FTO的泛素化；6）TRIM21抑制肝内脂质沉积：TRIM21在NAFLD模型中表达降低，过表达TRIM21抑制肝内脂质沉积。综上所述，HSP70-FTO促进肝内脂质沉积，而FTO的泛素化酶TRIM21抑制肝内脂质沉积及NAFLD的发生。本研究进一步阐明了NAFLD的发生机制，为其治疗提供潜在的治疗靶点。