Background Nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) is a chronic liver disease related to metabolic syndrome that can progress to liver cirrhosis. The involvement of the endoplasmic reticulum (ER) stress response in NAFLD progression and the roles played by activating factor 3 (ATF3) and the downstream nuclear protein 1 (NUPR1) are poorly understood. The aim of this study was to determine the gene expression profiles around the ATF3/NUPR1 axis in relation to the development of NAFLD using novel mouse models. Methods Fatty liver Shionogi (FLS) mice (n = 12) as a NAFLD model and FLS-ob/ob mice (n = 28) as a NASH model were fed a standard diet. The FLS mice were sacrificed at 24 weeks of age as a control, whereas the FLS-ob/ob mice were sacrificed at 24, 36, and 48 weeks of age. Hepatic steatosis, inflammation, and fibrosis were evaluated by biochemical, histological, and gene expression analyses. The expression levels of the ER-stress related genes Jun proto-oncogene (C-jun), Atf3, Nupr1, and C/EBP homologous protein (Chop) were measured in liver tissue. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Results Control mice demonstrated hepatic steatosis alone without apparent fibrosis. On the other hand, FLSob/ob mice showed severe steatohepatitis at both 24 and 36 weeks of age and severe fibrosis at both 36 and 48 weeks of age. The expression levels of Atf3, Nupr-1, and C-jun significantly increased from 24 to 48 weeks of age in FLS-ob/ob mice compared with control mice. The expression level of Chop was already high in FLS mice and maintained similar levels in FLS-ob/ob mice; the expression level was consistent with the percentage of TUNEL-positive cells. Conclusion The ATF3/NUPR1 axis plays a pivotal role in NASH progression in association with C-jun and Chop and appears to induce apoptosis from early steatosis in the NASH model mice.

Background The options for the treatment of nonalcoholic steatohepatitis (NASH) are limited. We examined the effects of ipragliflozin, a sodium-glucose cotransporter 2 inhibitor, on the fatty liver Shionogi (FLS)-ob/ ob mice, a non-alcoholic steatohepatitis mouse model. Methods FLS-ob/ob male mice were treated with vehicle (n = 10) and ipragliflozin (n = 8). Serum metabolic markers, histopathology of the liver, hepatic cholesterol and triglyceride levels and hepatic mRNA levels related to fibrosis, lipid metabolism and endoplasmic reticulum (ER) stress were compared between the two groups. Results The body weight and hepatic cholesterol and triglyceride levels were significantly decreased in the ipragliflozin group compared with the control group. Hepatic steatosis and fibrosis were significantly ameliorated by the treatment with ipragliflozin. Hepatic infiltration of macrophage, expression levels of 8-hydroxy-2-deoxyguanosine (8-OHdG) and hepatic mRNA levels of ER stress markers were not significantly modulated by the treatment with ipragliflozin. Conclusion Ipragliflozin can be a therapeutic option for patients with NASH. The precise mechanisms of action need to be clarified in future studies.