Effects Of Liraglutide On Pancreatic ATF4/CHOP Pathway In Rats Fed With High-fat Diets And Relative Mechanism Investigation

Objective:Glucagon like peptide-1(GLP-1)analogue liraglutide is a new antidiabetic drug for the treatment of type 2 diabetes,liraglutide targeted at incretin,reduced blood glucose in a glucose concentration-dependent manner,regulated the blood lipid and improve beta cell function and insulin resistance.Type 2 diabetes is a progressive disease,there are two main mechanisms,one is the beta cell dysfunction,the other is insulin resistance.In recent years,exposure to high fat conditions easily lead to endoplasmic reticulum stress(ERS),ERS is closely related to beta cell dysfunction and IR,and can lead to the occurrence and development of diabetes finally,but the mechanism is unclear.In this study,different concentrations of liraglutide were used in high-fat-fed rats to observe the effects on blood glucose and blood lipid.The expressions of glucose regulated protein 78(GRP78),activating transcription factor 4(ATF4),CCAAT / enhancer binding protein homologus protein(CHOP),tribbles homologous protein 3(TRB3)in both mRNA level and protein level were detected using a realtime PCR test and a Western blot test respectively,the effect of liraglutide on ATF4 / CHOP pathway in pancreatic ? cells in high-fat-fed rats was observed.The study provided a new research direction to reduce the incidence of diabetes and its complications.Method:Forty-four male rats were divided into four groups: control group,high fat group,intervention group 1 and intervention group2.The control group was fed with standard diet and the other three groups were fed with high fat diet.After 8 weeks of feeding,the control group and the high fat group were given subcutaneous injection of normal saline,Intervention group 1 was given subcutaneous injection of liraglutide 100?g/kg/d;intervention group 2 was given subcutaneous injection of liraglutide 200?g/kg/d.Drug intervention for 2 weeks,5 rats were randomly selected and treated with high insulin-glucose clamp test in each group,calculating glucose infusion rate.The fasting blood glucose,free fatty acid,fasting insulin,total cholesterol,triglyceride and high density lipoprotein cholesterol,low density lipoprotein cholesterol were measured in the remaining 6 rats in each group.The expression of GRP78,ATF4,CHOP and TRB3 in both mRNA level and protein level in the pancreas were determined by real-time quantitative PCR and Western blot.Results:1 General conditions of four groups.Compared with the normal control group,the levels of FBG,FFA,TC,FINS,TG and LDL-C in the high fat group were significantly increased,and HDL-C,HOMA-? and GIR were significantly decreased(P<0.01);Compared with the high fat group,the levels of FBG,FFA,TC,FINS,TG and LDL-C were significantly decreased,and the levels of HOMA-? and GIR were increased in the intervention group 2(P<0.05 or P<0.01).The levels of FFA,HOMA-? and GIR were significantly increased in the intervention group 1(P<0.05);and compared with the intervention group 1,the FBG,FFA and TC of the rats were significantly decreased in the intervention group 2(P<0.05).2 Comparison of GRP78,ATF4,CHOP and TRB3 in the pancreas mRNA expression of each group.Compared with the normal group,the mRNA levels of GRP78,ATF4,CHOP and TRB3 in the high fat group were significantly increased(P<0.01).Compared with the high fat group,the expression of GRP78,ATF4,CHOP and TRB3 mRNA were decreased in liraglutide intervention group 1 and intervention group 2(P<0.05).Compared with intervention group 1,mRNA expression of GRP78,ATF4,CHOP and TRB3 were decreased in intervention group 2(P<0.05).3 Comparison of GRP78,ATF4,CHOP and TRB3 in the pancreas protein expression of each group.Compared with the normal control group,the protein expression levels of GRP78,ATF4,CHOP and TRB3 were significantly increased in high fat group(P<0.01).Compared with the high fat group,the protein expression levels of GRP78,ATF4,CHOP and TRB3 were decreased significantly after treatment with liraglutide in intervention group 1 and intervention group 2(P<0.05).Compared with intervention group 1,tthe protein expression levels of GRP78,ATF4,CHOP and TRB3 were decreased in the intervention group 2(P<0.05).Conclusion:1.High-fat diet can develope glucose and lipid metabolism disorders,insulin resistance and islet dysfunction in high-fat-diet rats.2.Liraglutide is concentration-dependent to improve glucose and lipid metabolism disorders,relieve IR,and improve pancreatic ?-cell function.3.Liraglutide has a dose-dependent regulation of ATF4/CHOP pathway in pancreas of high-fat-fed rats,which may be related to the improvement of IR and the protection of pancreatic ?-cell function.