Improvement Of GLP-1 Secretion Disorder In Rats With Pre-diabetes By Sijunzi Decoction And Its Mechanisms

Objective: To study the mechanisms of GLP-1 secretion disorder in rats with pre-diabetes and observe the effect of Sijunzi Decoction.Methods: 1.Animal experiment: SD(Sprague Dawley)rats were randomly divided into four groups,namely the normal control group,the pre-diabetes model group,and the Sijunzi Decoction low,high dose groups(5.25 g/kg,10.5 g /kg).The rat model of pre-diabetes was established by the method of high-sugar and high-fat diet,that is,the normal control group was fed with normal diet,and the other three groups were fed with high-sugar and high-fat diet.Rats in the low,high dose groups were given a corresponding dose of Sijunzi Decoction every day.Normal control group and model group were given the corresponding volume of normal saline by intragastric administration for 10 weeks.8 rats were randomly selected from each group at weekends 2,4,6,8 and 10 after the start of the experiment and measure the Fasting blood glucose(FBG),Total Cholesterol(TC),High-density lipoprotein cholesterol(HDL-C),Triglyceride(TG),Low-density lipoprotein cholesterol(LDL-C),Glycated hemoglobin(GHB),Fasting serum insulin(FINS)and GLP-1 secretion after Fasting 12 h.Rats at the 10 th weekend were selected for oral glucose tolerance(OGTT)and TUNEL staining was used to detect the apoptosis of ileal cells in each group.Western blot was used to detect the expression of apoptosis-related proteins Bcl-2 and Bax,as well as the expression of endoplasmic reticulum stress-related proteins.2.STC-1 cell experiment: STC-1 cells were uniformly inoculated in the cell culture flask,and the cells were randomly divided into the normal group,the model group,the control group,and the low,high dose groups of Sijunzi Decoction.The normal group and the model group were cultured by adding ordinary medium,while the control group and the low and high dose groups were cultured by adding normal serum medium and serum medium containing Sijunzi Decoction(10%).After 24 h of incubation,the normal group was further cultured with fresh ordinary medium for 72 h,and the rest groups were further cultured with medium containing palmitic acid(0.4mmol /L)for 72 h.CCK8 assay was used to detect the activity of STC-1 cells and the apoptosis level of STC-1 cells in each group was detected by flow cytometry.The activity of Caspase-3,Caspase-9 in STC-1 cells was detected by colorimetry and the expression levels of Bcl-2,Bax as well as Endoplasmic reticulum stress related proteins in STC-1 cells were detected by Wsetern blot.Results: 1.Animal experiment: Compared with the normal group,the body weight,FBG,TC,TG,LDL-C,GHB and FINS of the rats in the prediabetes model group were significantly increased(P <0.01 or P <0.05).HDL-C and Serum GLP-1 secretion was significantly reduced(P <0.01).Bax,p-PERK and CHOP protein expressions were significantly increased(p <0.01),and Bcl-2 protein expression levels were significantly decreased(p <0.01).The apoptosis level of ileal cells was significantly increased.Compared with the model group,Sijunzi Decoction can significantly improve the apoptosis of ileal cells in rats with pre-diabetes and reduce the levels of body weight,FBG,serum TC,TG,LDL-C,GHB,Bax,p-PERK and CHOP as well assignificantly increase the levels of serum HDL-C,GLP-1 secretion and Bcl-2 protein(p <0.01 or p <0.05).2.STC-1 cell experiment:(1)Compared with the normal group,the cell activity of the model group was significantly decreased(P <0.01),the apoptosis rate was significantly increased and the expression levels of p-PERK and CHOP were significantly increased(P <0.01),while Sijunzi Decoction could significantly improve the activity of STC-1 cells(P <0.01 or P <0.05),and down-regulate the expression levels of p-PERK and CHOP proteins(P <0.01).(2).Sijunzi Decoction can significantly improve the level of apoptosis and injury of STC-1cells,up-regulate the expression of Bcl-2 protein(P <0.05),down-regulate the expression of Bax protein(P <0.01 or P <0.05),and reduce the activity of Caspase-3and Caspase-9(P <0.01 or P <0.05).Conclusion: 1.Sijunzi Decoction can significantly improve the GLP-1 secretion level in rats with pre-diabetes,which may be related to the mechanism that Sijunzi Decoction down-regulate the Bax protein expression level and up-regulate the Bcl-2protein expression level in the ileal tissues of rats by inhibiting endoplasmic reticulum stress 2.Sijunzi Decoction can significantly improve the level of apoptosis andinjury of STC-1 cells,up-regulate the expression of Bcl-2 protein,down-regulate the expression of Bax protein,and reduce the activity of Caspase-3 and Caspase-9.