Therapeutic Mechanism Study Of Salubrinal On Non-alcoholic Fatty Liver Disease Through EIF2α Signaling Pathway

Background Obesity is an imbalance disease of energy and metabolism,and characterized by excessive local lipid deposition.When the abnormality of lipid metabolism,it will cause a series of metabolic diseases including cardiovascular disease,hyperlipidemia,hepatic steatosis,diabetes and hepatic steatosis is the main pathological change in the liver.Compared with premenopausal women,the most noticeable change of postmenopausal women is the level of hormones in their bodies.Therefore,they are more likely to obesity related metabolic disorders,and the mainly manifested in the intense lipid deposition in the abdominal cavity.Animal studies shown that animals without ovaries have higher body fat and weight,and the pathological progress of fatty liver and liver fibrosis was more rapid than that of normal female animals.In the current study,endoplasmic reticulum(ER)stress may be the pathogenesis of non-alcoholic fatty liver disease(NAFLD).Studies have shown that ER stress can be observed in NAFLD.Moreover,when ER stress continues,it will also lead to lipid deposition in the liver,resulting in the imbalance of homeostasis in hepatocytes.Furthermore,autophagy is activated under ER stress and maintains material transformation in cells as a response mechanism to stress.PERK is a sensor which can stimulate e IF2α phosphorylation and activate ATF4 transcription and translation,while p-e IF2α dephosphorylation is regulated by PP1 complex.Salubrinal is a synthetic small molecule compound,which can selectively inhibit the PP1 complex and block the dephosphorylation of p-e IF2α.Therefore,Salubrinal may provide a therapeutic strategy for ER stress-related diseases.Objectives In order to study the potential therapeutic mechanism of Salubrinal in the treatment of obesity induced non-alcoholic fatty liver disease by regulating e IF2αsignaling pathway,we used high-fat diet or with OVX ovariectomy model to detect the key role of ER stress in the development of NAFLD.In order to further clarify the mechanism,Salubrinal was used as a tool to regulate the e IF2α signal pathway,and to detect the effects of ER stress and ER-induced autophagy on regulating lipid metabolism disorder and inhibiting lipid deposition.Methods Ninety five C57BL/6 female mice of 14 weeks old were divided into five groups: control group(SC),high fat group(HF),HF with Salubrinal group(HFS),HF with ovariectomy group(HO),HO with Salubrinal group(HOS).Except for the SC group,all the mice were underwent sham operation or bilateral oophorectomy and maintained a high-fat diet.After 8 weeks,the mice in the HS group and HOS group were administrated with Salubrinal subcutaneously for another 8 weeks(the injection dose was 1mg/kg).Orbital blood was collected for blood lipid analysis,and the liver,abdomen was separated and collected for wet mass measurement.HE and oil red O staining in adipose tissue and liver samples were used to observe the histopathological changes,and the progress of disease was evaluated.The effects of Salubrrinal on lipid production and adipocyte differentiation were observed in vitro.Meanwhile,Western blot was used to detect e IF2α signal pathway and autophagy related protein expression in vivo and in vitro.Results Compared with normal mice,the serum lipid level and adipose tissue were increased in obese mice,while Salubrinal attenuated obesity and total body fat by blocking lipid disorder.Also,the histological severity of hepatic steatosis and fibrosis in liver and the changes of related biochemical indexes were suppressed in response to Salubrinalby inhibiting lipid deposition.Furthermore,in vitro and in vivo experiments showed that the lipid deposition of hepatocytes and adipocytes was significantly reduced after Salubrinal intervention.In addition,Western blot showed that Salubrinal inhibited ER stress by increasing the expression of p-e IF2α and ATF4 with a decrease in the level of CHOP.It promoted autophagy by increasing LC3II/I and inhibiting p62.Correlation analysis indicated that lipogenesis in the development of NAFLD was associated with ER stress.Conclusion In conclusion,we show that eIF2α plays an important role in the pathogenesis of obesity induced non-alcoholic fatty liver.In this study,ER stress can effectively reduce the steatosis of hepatocytes and inhibit the lipid deposition.