Department of Hepatology, Graduate School of Medicine, Osaka City University, Osaka 545-8585, Japan.
Lab Invest. 2010 Feb;90(2):245-56. doi: 10.1038/labinvest.2009.123. Epub 2009 Nov 30.
Fatty liver disease has become a health problem related to metabolic syndrome worldwide, although its molecular pathogenesis requires further study. It is also unclear whether advanced fibrosis of steatohepatitis will regress when diet is controlled. The aim of this study was to investigate whether the resolution of fibrosis occurs in steatohepatitis induced by a methionine-choline-deficient diet (MCDD). Manifestation of endoplasmic reticulum (ER) stress in this model was also studied. Nonalcoholic steatohepatitis with advanced fibrosis was induced in rats by feeding them an MCDD for 10 weeks. Instead of MCDD, a methionine-choline control diet (CD) was given for the last 2 weeks to the experimental group. Fibrosis and inflammation were determined by tissue staining. Protein and gene expressions were determined by immunoblotting and quantitative reverse transcription-PCR (RT-PCR), respectively. Expressions of caspase-7, caspase-12, glucose-regulated protein 78 (GRP78), and protein disulfide isomerase were evaluated to clarify the presence of ER stress. Changing the diet from MCDD to CD triggered the reduction of fat in hepatocytes, a decrease in inflammatory gene expression and oxidative stress, and regression of fibrosis accompanied by the disappearance of activated stellate cells and macrophages. Immunohistochemistry, immunoblotting, and RT-PCR analysis all indicated the occurrence of ER stress in steatohepatitis, while it recovered immediately after changing the diet from MCCD to CD. The ratio of hepatocyte proliferation/apoptotis increased significantly during the recovery stage. This simple experiment clearly shows that changing the diet from MCDD to a normal diet (CD) triggers the resolution of hepatic inflammatory and fibrotic reactions and hepatocyte apoptosis, suggesting that MCDD-induced steatohepatitis is also reversible. ER stress appears and disappears in association with the generation and regression of steatohepatitis, respectively, with fibrosis.
非酒精性脂肪性肝病已成为与代谢综合征相关的全球性健康问题，尽管其分子发病机制仍需进一步研究。饮食控制时，脂肪性肝炎的晚期纤维化是否会消退尚不清楚。本研究旨在探讨在蛋氨酸-胆碱缺乏饮食（MCDD）诱导的脂肪性肝炎中是否会发生纤维化消退。还研究了该模型中内质网（ER）应激的表现。通过用 MCDD 喂养大鼠 10 周，诱导非酒精性脂肪性肝炎伴晚期纤维化。实验组在最后 2 周给予蛋氨酸-胆碱对照饮食（CD）代替 MCDD。通过组织染色确定纤维化和炎症。通过免疫印迹和定量逆转录-PCR（RT-PCR）分别确定蛋白质和基因表达。评估半胱氨酸天冬氨酸蛋白酶-7、半胱氨酸天冬氨酸蛋白酶-12、葡萄糖调节蛋白 78（GRP78）和蛋白二硫键异构酶的表达以阐明 ER 应激的存在。从 MCDD 改为 CD 饮食会触发肝细胞脂肪减少、炎症基因表达和氧化应激降低以及纤维化消退，同时伴随着激活的星状细胞和巨噬细胞的消失。免疫组织化学、免疫印迹和 RT-PCR 分析均表明脂肪性肝炎存在 ER 应激，而从 MCCD 改为 CD 后，ER 应激立即恢复。在恢复阶段，肝细胞增殖/凋亡的比例显著增加。这个简单的实验清楚地表明，从 MCDD 改为正常饮食（CD）会触发肝炎症和纤维化反应以及肝细胞凋亡的消退，提示 MCDD 诱导的脂肪性肝炎也是可逆的。ER 应激与脂肪性肝炎的发生和消退相关联，分别出现和消失，伴随着纤维化。
