The Role And Mechanisms Of Hepatic Bile Acid Metabolic In Roux-en-Y Gastric Bypass Surgery For Type 2 Diabetes

IntroductionWith the developing of economy,the living for people have improved,while diabetic increased too.In the past 20 years,the numbers of diabetic have doubled which has been a serious public health problem,especially obese and type 2 diabetes mellitus(T2DM)patients.However,medical treatment,as a vital part of integrated therapy,cannot do a well job in reducing blood glucose,because of lifelong medication and poor patient compliance.As a res μ It,how to give a better treatment on T2DM is one of the most important topics in the medical domain.Since the beginning of the 1990s,bariatric surgical approaches have provided a definitive treatment for T2DM and related complications.Accumμlated studies have shown that Roux-en Y gastric bypass(RYGB)surgeries produce weight loss and improve glycemic control;however,the mechanisms of glycemic improvements are largely unknown.In this study,we established RYGB obese and T2DM rat model to explore the effect of RYGB on the bile acid pathway and investigate the molecμlar mechanisms involved in HepG2 cells.Materials and Methods1.The main materials:Forty healthy male SD Rats;HepG2 cells2.Methods:(1)Forty SD rats were randomly divided into control group,high-fat diet group,sham-operated group and operated group(N=10 in each group).The body weights,food intakes,fasting blood-glucose were monitored.The levels of serum cholesterol and triglyceride were measured before and after operation.Intraperitioneal glucose tolerance test(IPGTT)and ins μ lin tolerance test(ITT)were performed to evaluate the glucose tolerance and insμlin sensitivity.The mRNA expressions of farnesoid X receptor(FXR),small heterodimeric partner(SHP),bile salt export pump(BSEP),phosphoenolpyruvate carboxykinase(PEPCK),glucose-6-phosphatase(G6Pase),glucose transporter2,(GLUT2)and fibroblast growth factor21(FGF21)were detected by Real-time PCR and the protein levels of FXR,FGF21 and G6Pase were evaluated by Western blot.Oil red-O staining was used to measure lipid accumμlation in embedded rat livers.(2)HepG2 cells were treated with FXR agonists(GW4064,5μmol/L)or FXR inhibitors(Guggulsterone,5μmol/L)at different time(0min,30min,2h,4h,6h,12h,24h).The mRNA levels of FXR,SHP,BSEP,PEPCK and G6Pase were detected by Real-time PCR and the protein levels of FXR,SHP,PEPCK and G6Pase were detected by Western blot.The lipid accumμin livers was examined by Oil red-O staining.Resμlts1.There were no significant differences in body weights,food intakes and fasting glucose level between high-fat diet group,sham-operated group and operated group before the operation.After the operation,the body weights and the food intakes decreased in the sham operation group,and gradually returned to normal in the fourth weeks postoperative,which were similar to the high fat diet group.The body weights,food intakes and fasting blood-glucose levels significant reduced in the operated group,as compared to the high-fat diet group and sham-operated group.2.The areas under the curve of IPGTT and ITT in control group were normal.There were no differences in the areas of IPGTT and ITT curves between the high fat diet group,the sham operation group and the operation group before operation.But after operation,the areas of IPGTT and ITT curve improved significantly,as compared to the high fat diet group and the sham operation group.3.The levels of cholesterol and triglycerides in the operation group were significantly lower in operation group than those in the high fat diet group and sham operation group.Oil red-O staining showed that lipid droplets in liver significantly increased in high-fat diet group and sham-operated group compared with control group,and this effect was relieved in operation group.4.The mRNA expressions of FXR,SHP,BSEP,GLUT2 and FGF21 in operated group were significantly higher than in high-fat diet group and sham-operated group,while PEPCK and G6Pase expressions were reduced.The protein levels of FXR and FGF21 were also higher in operated group than in high-fat diet group and sham-operated group,but PEPCK and G6Pase expression were decreased.5.In HepG2 cells,the mRNA and protein expressions of FXR,SHP and BSEP were unregμlated with GW4064 treatment,an activator of FXR.That meant gluconeogenesis reduced.While gluconeogenesis was rised by FXR inhibitor Guggulsterone.Conclusions1.The body weights and food intakes significantly reduced after RYGB,improved glycemic controls and dyslipidemia and decreased liver lipid accumμlation in obesity with T2DM rat model.2.RYGB coμld obviously ameliorate gluconeogenesis which is mediated by bile acid-FXR-SHP pathway.Bile acid-FXR-SHP pathway may participate in hepatic glucolipid metabolism,thus contributing to glucose homeostasis improvement after RYGB.3.FXR pathway may participate in adjusting gluconeogenesis of HepG2 cells.