Liver gene expression profile of wild type, liver-specific PTEN KO, SCAP KO and PTEN/SCAP double KO mice.

Nonalcoholic steatohepatitis (NASH), a severe form of nonalcoholic fatty liver disease, is characterized by hepatic steatosis and hepatocellular injury and progresses to cirrhosis and hepatocellular carcinoma. Sterol regulatory element-binding proteins (SREBPs) are master regulators of lipogenesis. Liver-specific PTEN knockout (KO) mice show constitutive upregulation of SREBP through PI3K-Akt pathway activation, leading to spontaneous fatty liver and subsequent HCC development. SREBP cleavage-activating protein (SCAP) plays a critical role in SREBP activation. We sought to determine the impact of SREBP inhibition on NASH and HCC development. To this end, we additionally inhibited SREBP pathway in liver-specific PTEN mice by ablating SCAP and generated liver-specific PTEN/SCAP double KO (DKO) mice. However unexpectedly, inhibition of SCAP/SREBP pathway markedly exacerbated liver injury (5weeks), fibrosis (5months), and carcinogenesis (7 months) in PTEN KO mice. To elucidate the mechanisms of liver injury in liver-specific PTEN/SCAP DKO mice, we conducted transcriptome analyses of the livers. Overall design: PTEN F/F, SCAP F/F and PTEN/SCAP F/F mice were crossed to Alb-Cre mice to generate liver-specific PTEN KO, SCAP KO and PTEN/SCAP DKO mice, respectively. Wilt type, liver-specific PTEN KO, SCAP KO and PTEN/SCAP DKO mice were fed with normal diet for 5 weeks, and total RNA samples were extracted from liver tissues. We compared relative liver gene expression levels across these mice.

非酒精性脂肪性肝炎（Nonalcoholic steatohepatitis, NASH）是非酒精性脂肪性肝病的重症亚型，以肝脂肪变与肝细胞损伤为特征，可进展为肝硬化与肝细胞癌（hepatocellular carcinoma, HCC）。固醇调节元件结合蛋白（Sterol regulatory element-binding proteins, SREBPs）是脂肪生成的核心调控因子。肝脏特异性PTEN敲除（knockout, KO）小鼠可通过PI3K-Akt信号通路激活，实现SREBP的组成性上调，进而引发自发性脂肪肝并最终诱发肝细胞癌。SREBP裂解激活蛋白（SREBP cleavage-activating protein, SCAP）在SREBP激活过程中发挥关键作用。本研究旨在明确SREBP抑制对NASH及肝细胞癌发生发展的影响。为此，我们通过敲除SCAP基因，在肝脏特异性PTEN敲除小鼠中抑制SREBP通路，并构建得到肝脏特异性PTEN/SCAP双敲除（double knockout, DKO）小鼠。但令人意外的是，SCAP/SREBP通路抑制可显著加重PTEN敲除小鼠的肝损伤（造模5周时）、肝纤维化（造模5个月时）与癌变进程（造模7个月时）。为阐明肝脏特异性PTEN/SCAP双敲除小鼠肝损伤的潜在机制，我们对其肝脏组织开展了转录组分析。实验整体设计如下：将PTEN F/F、SCAP F/F及PTEN/SCAP F/F小鼠分别与Alb-Cre小鼠杂交，以获得肝脏特异性PTEN敲除、SCAP敲除及PTEN/SCAP双敲除小鼠。将野生型（wild type）、肝脏特异性PTEN敲除、SCAP敲除及PTEN/SCAP双敲除小鼠以正常饲料饲养5周后，从其肝组织中提取总RNA样本，比较各组小鼠的肝脏基因相对表达水平。