Effects Of Punica Glucoside On Glucose And Lipid Metabolism And Hepatic Oxidative Stress In T2DM Mice

ObjectiveTo observe the effects and to explore the mechanism of punicalagin in glucose and lipid metabolism,liver oxidative stress and endoplasmic reticulum stress were induced in type 2 diabetes mellitus(T2DM)mice by intraperitoneal injection of high fat diet combined with low dose STZ.MethodsFrom among 8-week-old male ICR mice,which were fed a normal diet for 7 days,7 mice were randomly selected as normal in relation to the high fat group.Mice in the high fat group were fed a high fat diet for 8 weeks.Each group was administered 100 mg/kg streptozotocin(STZ)by intraperitoneal injection,and the model of type 2 diabetes was established.The mice were randomly divided into the model group and the punicalagin group.Mice in punicalagin groups were administered 40%punicalagin at 200 mg/kg(low dose)or 400 mg/kg(high dose),while those in the model group and normal control group were given distilled water.Drug delivery was executed as follows:0.1 ml/10 g body mass,once a day in the morning every day for the experimental period.The T2DM mice were fed a high fat diet,and the normal mice were fed ordinary feed for 5 weeks.During the period of administration,we observed and recorded the parameters,body weight,food intake,and fasting blood glucose(FBG)levels of mice in each group.The oral glucose tolerance test(OGTT)was performed on each group before the end of the experiment.Five weeks after drug administration,eyeball blood was collected and levels of the following components were measured:fasting blood glucose(FBG),serum insulin(FINS),total cholesterol(TC),triglyceride(TG),serum high density lipoprotein(HDL-C),serum very low density lipoprotein(LDL-C),aspartate aminotransferase(AST),alanine aminotransferase(ALT),serum creatinine(Cr),urea nitrogen(BUN),malondialdehyde(MDA),superoxide dismutase(SOD),glutathione(GSH),nitric oxide(NO),and peroxidase(CAT).The liver tissue homogenate kit was used to detect the content of MDA and GSH in liver tissue.The insulin sensitivity index(ISI)was calculated;the weight of the liver tissue was determined,and the ratio of liver weight to body weight was calculated.The liver tissue of mice was harvested and fixed with 10%formalin.The sections were embedded in paraffin and sliced;the pathological morphology of liver tissue was observed by HE staining.Western blot method was performed to detect the protein expressions of GRP78 and p-eIF2 alpha in liver tissue homogenate.RT-PCR assay was performed to detect the gene expressions of GRP78,eIF2,ATF4 and CHOP in liver tissue.The protein expressions of GRP78 and p-eIF2 alpha were detected by immunohistochemical staining in the paraffinized sections of liver tissue.Results1.Glycolipid metabolism and insulin sensitivity:compared with the model group,both the low and high dose punicalagin groups showed significantly reduced body weight,food intake,and liver index of T2DM mice(P<0.01).punicalagin can decrease the levels of FBG,TC,TG,LDL-C,and free fatty acids(FFA)in T2DM mice(P<0.01),increase the HDL-C content(P<0.01),reduce FINS level,improve the level of ISI,and improve the results of OGTT(P<0.01).2,Liver and kidney function and Liver Pathomorphology:Punicalagin can improve the levels of AST,ALT,TG,Cr,and BUN in serum of T2DM mice(P<0.01)and improve the liver and kidney tissues in mice under T2DM conditions.Punicalagin can improve the pathological morphology of the liver tissue of T2DM mice and protect the liver.3.Oxidative stressand Endoplasmic reticulum stress:Punicalagin can reduce the content of MDA and NO in serum of T2DM mice and increase the content of SOD and GSH in the liver tissue(P<0.01),but significant improvements were not observed in CAT levels(P>0.05).It can reduce the content of MDA in liver tissue and increase the content of GSH in tissue.Punicalagin can significantly reduce the mRNA expression of GRP78,eIF2a,ATF4,and CHOP.The low and high doses of punicalagin can reduce the level of eIF2a alpha phosphorylation and the protein expression of CHOP and GRP78.Conclusions1.Punicalagin in T2DM mice can reduce fasting blood glucose levels,food intake,and body weight.It can improve the insulin sensitivity of T2DM mice,improve glucose tolerance,protect islet energy,and improve the metabolism of sugar.2.Punicalagin glycosides can effectively regulate the function of liver and kidney,and protect the function of liver and kidney.Punicalagin glucoside can reduce the liver weight ratio of T2DM mice,improve the indices of blood lipid,and reduce the liver lipid deposition.3.Punicalagin can effectively improve the oxidative stress in T2DM by eliminating reactive oxygen free radicals,relieve endoplasmic reticulum stress,and improve insulin resistance in the liver.Based on the mechanisms underlying endoplasmic reticulum stress,we elucidated the regulatory effects of punicalagin on glycolipid metabolism in type 2 diabetes and on the improvement of liver injury.We also explored new natural medicines for the prevention and treatment of T2DM.