新型抑癌基因ZHX2调节脂质代谢参与非酒精性脂肪肝的作用研究

Nonalcoholic fatty liver disease (NAFLD) is now the most common liver disease in both adults and children worldwide and it seriously threatens the health of human beings. The pathogenesis of NAFLD is complicated and has not been completely elucidated. It is increasingly recognized that hepatocyte steatosis mediated by lipid metabolism disorder plays critical roles in the development of NAFLD. Identifying key regulators of lipid metabolisms will definitely helps us to understand the pathogenesis of NAFLD. Here, in this project, we intend to identify ZHX2 as a potential key regulator of lipid metabolism. Zinc-fingers and homeoboxes 2 (ZHX2) has been recognized as a ubiquitous transcriptional repressor which regulates several liver cancer related genes. However, less is known about its biological effects in liver diseases. In 2012, for the first time, we demonstrated the tumor suppression role of ZHX2 in hepatocellular carcinoma (HCC). Very strikingly, our recent data suggests that ZHX2 can regulate the expression of various lipid metabolism-associated genes including lipid lipase, one of the most important regulators in lipid lyses. Overexpression of ZHX2 in HepG2 cells suppress lipid deposition mediated by oleic acid. Liver specific ZHX2 transgene mice show significant less lipid accumulation in liver compared to control mice. Therefore, we hypothesize that ZHX2 is a potential key regulator of lipoprotein metabolism which play an important role both in hepatocytes steatosis and in the pathogenesis of NALFD. In order to test this hypothesis, this project intends to evaluate the role of ZHX2 in NAFLD using ZHX2 transgene mice and ZHX2 knockout mice. The key targets regulated by ZHX2 during NAFLD will be identified in vitro and in vivo. The expression of ZHX2 and its targets will be tested in clinical samples in order to estimate the clinical significance of ZHX2 in NAFLD. The projects will not only contribute to illustrating the pathogenesis of NAFLD, but also provide new targets for the intervention of NAFLD.

非酒精性脂肪肝(nonalcoholic fatty liver disease,NAFLD) 发病率逐年升高，危害严重，其发病机制复杂，迄今尚未阐明。脂代谢异常介导的肝细胞脂肪变是NAFLD发生的基础，脂代谢关键调节基因的鉴定对于阐明NAFLD发生机制具有重要意义。转录抑制因子ZHX2是申请者首次发现的新型抑癌基因。申请者新近研究提示，ZHX2可以调节多种脂代谢相关基因表达，并抑制肝细胞脂肪变。据此，申请者提出：ZHX2是潜在的脂质代谢关键调控基因，在NAFLD发生中发挥重要作用。课题拟利用体内外实验及临床标本，系统研究ZHX2调节脂代谢的分子机制，明确其调控的脂代谢关键靶基因及分子通路，并阐明ZHX2在NAFLD发生中的作用。申请者长期从事ZHX2与肝病研究，工作基础良好。课题着眼于具有脂代谢调节功能的肿瘤基因研究NAFLD发生机制，创新性明显，具有重要理论意义与潜在应用价值。

肝细胞肝癌（HCC）是最为常见的肝脏肿瘤，也是世界范围内第六大常见恶性肿瘤。越来越多的研究证实非酒精性脂肪肝病（NAFLD）是肝癌发生的独立危险因素。转录因子ZHX2是影响肝癌发生的重要肿瘤抑制因子，近年发现其与血脂代谢失调存在密切关系，提示ZHX2在NAFLD-HCC发生过程中可能发挥重要作用。本项目首次证实ZHX2在体内外均具有显著抑制脂质沉积的作用，进一步研究发现，脂蛋白脂酶（LPL）在ZHX2调控脂代谢及肝细胞脂肪变中发挥关键作用。机制研究显示，ZHX2抑制LPL启动子活性，而LPL启动子Octamer作用原件的突变导致ZHX2抑制作用的丧失。免疫共沉淀 、染色质免疫共沉淀及凝胶迁移阻滞试验结果显示，ZHX2可通过与Oct-1相互作用抑制Oct-1与LPL启动子结合而发挥转录抑制作用。本研究还首次证实了LPL促进肝癌细胞增殖和小鼠体内移植瘤的生长的作用，体内外拯救实验结果表明LPL过表达显著逆转ZHX2抑制细胞增殖和脂质沉积的作用。临床研究进一步证实肝癌组织中ZHX2和LPL表达显著负相关，进一步证明了LPL在ZHX2抑癌中的关键作用。综上所述，我们研究首次阐明了ZHX2通过抑制Oct-1介导的LPL转录激活作用而下调LPL表达，从而发挥减缓NAFLD-HCC转变的重要作用。在完成计划任务书上述内容之外，本课题还系统研究了ZHX2的多种生物学活性，发现了ZHX2抑制重要膜转运蛋白P蛋白转录及HBV复制的作用，为进一步揭示ZHX2在慢性肝病中的作用提供了重要依据。本课题共发表标注SCI论文3篇，培养研究生4人，其中1人获得山东省优秀硕士论文，1人入选中国免疫学青年学者（2016年度），申报发明专利2项。