OBJECTIVETo study role of endoplasmic reticulum stress in the development of fatty liver fibrosis induced by methionine-choline-deficient diet in rats.

METHODSNon-alcoholic steatohepatitis was induced by 10 weeks- methionine-choline-deficient diet (MCDD), Markers of endoplasmic reticulum stress were determined by immunoblotting and real-time PCR.

RESULTSThe number of apoptotic hepatocytes, The expression levels of endoplasmic reticulum stress markers were increased significantly in MCDD group compared to control group (probability value less than 0.05 or probability value less than 0.01), while ratio of hepatocyte proliferation/apoptosis was decreased in MCDD group (probability value less than 0.01). The number of hepatocytes apoptosis, and the expression levels of endoplasmic reticulum stress markers were decreased significantly 2 weeks after the feeding with normal diet in MCDD group (probability value less than 0.05 or probability value less than 0.01).

CONCLUSIONMCDD induces endoplasmic reticulum stress and fibrosis in rats.

Animals ; Apoptosis ; Caspases ; genetics ; metabolism ; Cell Proliferation ; Choline ; administration & dosage ; metabolism ; Choline Deficiency ; Diet ; Disease Models, Animal ; Endoplasmic Reticulum ; physiology ; Fatty Liver ; complications ; Liver ; metabolism ; pathology ; Liver Cirrhosis ; diet therapy ; etiology ; physiopathology ; Male ; Methionine ; deficiency ; RNA, Messenger ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Wistar

OBJECTIVETo clarify the effects of endoplasmic reticulum stress (ER stress) and mitogen-activated protein kinase (MAPK) on hepatocyte apoptosis in rats with non-alcoholic fatty liver fibrosis induced by methionine-choline-deficient diet (MCDD).

METHODSNonalcoholic steatohepatitis with advanced fibrosis was induced in rats by giving a MCDD for 10 weeks (group M). A methionine-choline-control diet (MCCD) instead of MCDD was given for the last 2 weeks to the experimental group (group R). Steatosis, fibrosis and inflammation were determined by tissue staining. The activation of hepatic stellate cells and oxidative stress were determined by immunostaining, immunoblotting or real time-PCR (RT-PCR), respectively. Hepatocyte apoptosis was determined by TUNEL staining. Expressions of glucose-regulated protein 78 (GRP78), caspase-12, caspase-7, cleaved caspase-7, caspase-3, cleaved caspase-3, and caspase-9 were evaluated to clarify the presence of ER stress. Expressions of c-Jun, ERK1/2, p-ERK1/2 were evaluated to clarify the states of MAPK signaling.

RESULTSChanging the diet from MCDD to MCCD triggered the reduction of fat in hepatocytes, a decrease in inflammatory response, oxidative stress, and fibrosis. The protein expressions of ERP78, caspase-12, caspase-7, and cleaved caspase-7 were increased significantly in group M compared with normal control group (group N, P < 0.05 or P < 0.01), the mRNA expressions of ERP78, caspase-12, and caspase-7 were also increased significantly in group M compared with group N (3.03 ± 0.41 vs 2.12 ± 0.37, 1.86 ± 0.36 vs 0.78 ± 0.20, and 2.38 ± 0.19 vs 1.84 ± 0.13, respectively, P < 0.05 or P < 0.01), while they recovered immediately in group R. In contrast, the protein levels of caspase-3, cleaved caspase-3 and mRNA expressions of caspase-3 and caspase-9 revealed no significant differences in three groups (P > 0.05). The mRNA expressions of c-Jun and protein levels of ERK1 and p-ERK1 were increased significantly in group M compared with group N (P < 0.01), while they recovered immediately after changing the diet from MCDD to MCCD.

CONCLUSIONSER stress plays a role in the development and regression of non-alcoholic fatty liver fibrosis induced by MCDD, however, ER stress-related caspase-12 pathway may not be the main mechanism of hepatic apoptosis, and MAPK signaling may play an important role in hepatic apoptosis in the model.

Animals ; Apoptosis ; Caspase 12 ; metabolism ; Caspase 3 ; metabolism ; Caspase 7 ; metabolism ; Caspase 9 ; metabolism ; Choline Deficiency ; Diet ; Endoplasmic Reticulum Stress ; physiology ; Fatty Liver ; etiology ; metabolism ; pathology ; Heat-Shock Proteins ; metabolism ; Hepatocytes ; pathology ; Liver Cirrhosis ; etiology ; metabolism ; pathology ; Male ; Methionine ; deficiency ; Mitogen-Activated Protein Kinases ; metabolism ; Non-alcoholic Fatty Liver Disease ; Proto-Oncogene Proteins c-jun ; metabolism ; RNA, Messenger ; metabolism ; Rats ; Rats, Wistar ; Signal Transduction