The Effect Of Sijunzi Granule On Prediabetes In Rats And The Potential Mechanisms Implicated

Objiective: To observe the ameliorative effect of Sijunzi(SJZ)granule on pancreates in rats and the possible mechanism implicated.Methods: 1.Animal experiment: Prediabetes in rats was established by feeding high-sugar and high-fat diet.Then the rats were randomly divided into control group,model group,high-dose of SJZ granule group(10.50 g/kg·d)and low dose of SJZ granule group(5.25 g/kg.d).Rats were given SJZ granule or distilled water intragastrically daily for 10 weeks.Fasting blood glucose(FBG),fasting serum insulin(FINS),glycated hemoglobin(GHb),triglyceride(TG),total cholesterol(TC),low density lipoprotein cholesterol(LDL-C)and high density lipoprotein cholesterol(HDL-C)were determined on the 2nd,4th,6th,8th and 10 th weekend.Levels of insulin resistance were evaluated as HOMA-IR.At the end of the experiment,rats were subjected to an Oral glucose tolerance test(OGTT)and the values of area under curve(AUC)were calculated.Pancreatic islet cell apoptosis was observed by TUNEL staining.Levels of GRP78,ATF4,CHOP proteins expressions and phosphorylated PERK protein as well as the apoptosis-related proteins Bcl-2 and Bax were examined by Western blot analysis.2.MIN6 cell experiment: SJZ granule containing serum was prepared by serum pharmacological method.The MIN6 cells were divided into control group,model group,blank serum group,high-dose of SJZ granule group and low dose of SJZ granule group.Following pre-incubation with Sijunzi granules-containing serum for 24 hours,MIN6 cells were exposed to palmitic acid(0.4 mmol/L)for 24 hours.Cell viability was detected by CCK-8 assay.Cellapoptosis was determined by flow cytometry.Protein levels of GRP78,p-PERK,ATF4 and CHOP were measured by Western blot analysis.Results: 1.Animal experiment: Compared with the normal group,in prediabetic rats,levels of FBG,FINS,GHb,HOMA-IR,TG,TC and LDL-C were markedly higher(P<0.05 or P <0.01).The level of glucose tolerance and HDL-C decreased significantly(P <0.05 or P <0.01).Obvious cell apoptosis was observed in islets of prediabetic rats.Besides,the levels of GRP78,ATF4,CHOP,p-PERK protein and pro-apoptotic protein Bax all increased notably(P <0.05 or P<0.01).The anti-apoptotic protein Bcl-2 decreased markedly(P <0.01).Compared with the model group,supplementation with SJZ granule resulted in a significant reduction of FBG,FINS,GHb,HOMA-IR,TG,TC and LDL-C in prediabetic rats(P <0.05 or P <0.01).The level of glucose tolerance increased notably(P <0.01)and the apoptosis of pancreatic islet cell was significantly decreased.The levels of GRP78,ATF4,CHOP,p-PERK and Bax protein expressions were all decreased evidently(P <0.05 or P <0.01)and the Bcl-2 protein was increased obviously(P <0.01).2.MIN6 cell experiment:Compared with the normal group,palmitic acid significantly reduced the viability of MIN6 cells(P <0.01)and augmented markedly the number of apoptosis of MIN6cells(P <0.05 or P <0.01).The levels of GRP78,ATF4,CHOP and p-PERK protein expressions were all decreased evidently(P <0.05 or P <0.01).Compared with the model group,pretreatment with SJZ granules-containing serum significantly ameliorated palmitic acid-induced cell injury and apoptosis(P <0.05 or P <0.01).The levels of endoplasmic reticulum stress-related GRP78,ATF4,CHOP and p-PERK protein expressions were down-regulated significantly.Conclusion: SJZ granules can markedly ameliorate the symptom of prediabetic rats,and its relevant mechanism may be contributed to the reduction of insulin resistance and the inhibition of pancreatic islet cell apoptosis and the regulation of Bcl-2 family proteins expression.SJZ granules can suppress pancreatic islet cell apoptosis and its mechanism possibly related to the inhibition of endoplasmic reticulum stress-related PERK-CHOP signaling pathway.