AMPK Plays A Critical Role On Geniposide Preventing Cell Injury And Dysfunction Induced By High Concentration Of Glucose In Pancreatic ? Cells

Type 2 diabetes mellitus(T2DM)is a common multifactorial,polygenic disease characterized with a defect of insulin secretion,abnormity of insulin receptor and ? cell dysfunction.Glucose-stimulated insulin secretion(GSIS)is of great significance to control glucose homeostasis,maintain the normal physiological function of ? cells.Furthermore,the impairment of GSIS is a crucial element of ? cell failure and T2 DM.Moreover,most of the drugs currently available for the treatment of T2 DM have failed to address the core defects of beta cell damage and dysfunction in diabetetreatment.Geniposide is a natural compound extracted from Gardenia jasminoides Ellis.Previous work confirmed that geniposide was a GLP-1R selective agonist,which acutely enhanced GSIS in response to the stimulation of low or moderately high concentrations of glucose in INS-1 cells and pancreatic islets ? cells.However,geniposide exerted a contrary role on GSIS when exposed to high concentrations of glucose.Geniposidic reduced the blood glucose of diabetic mice and increased the secretion of insulin.Mealwhile,geniposide also enhanced the viability of pancreatic beta cells induced by high concentrations of glucose,Unfortunately,the associated molecular mechanisms about geniposide regulating GSIS in rat INS-1 pancreatic ? cells and the role of geniposide on cell injury induced by high glucose are not clear.In recent years,a growing body of evidence suggests that production and release of insulin and insulin gene expression are closely related to the activity of AMPK,and many drugs for the treatment of T2 DM have been focused on the novel target that activate AMPK directly or indirectly.Therefore,AMPK is becoming increasingly important target for the treament of T2 DM treatment.Research purposes:The first part: we design to investigate the role of AMPK on the geniposide regulating GSIS in rat INS-1 pancreatic ? cellsThe second part: This study is to explore the association about geniposide antagonizing high glucose-induced pancreatic ? cells injury with AMPK.Research methods:Firstly,from the perspective of cellular energy metabolism,the effect of geniposide on phosphorylation of AMPK and ACC were detected by Western blotting analysis in the presence of low or high concentrations of glucose.AMPK activator,AMPK inhibitor and AMPK siRNA on glucose absorption,metabolism and insulin secretion in pancreatic beta cells were examined by ELISA.Additionaly,treatment of pancreatic beta cells 24,48 and 72 hours with geniposide in the presence of high concentrations of glucose,the effect of geniposide on high glucose induced viability of pancreatic beta cells was detected by MTT assay.In addition,the effect of AMPK activator,AMPK inhibitor or AMPK siRNA on geniposide regulating HO-1,Bcl-2,Bax protein expression and the ratio change of Bcl-2/Bax were detected by Western blotting analysis.We also examined the effect of geniposide on the caspase-3 activity which is the key execution protein in the process of cell apoptosis.Results and Conclusions:(1)Our data suggested that geniposide obviously enhanced phosphorylation of AMPK in the presence of low glucose,but not in the presence of high glucose in INS-1 cells.(2)AMPK inhibitor and AMPK siRNA remarkably attenuated the role of geniposide on glucose uptake and metabolism(ATP production)and GSIS in INS-1 cells.(3)Geniposide significantly increased the viability of pancreatic beta cells induced by high glucose.(4)Geniposide increased the protein levels of cell apoptosis-associated enzymes including HO-1,Bcl-2,but decreased the protein levels of Bax significantly.Moreover,geniposide directly prevented the cleavage of caspase-3 induced by high glucose,and this effect was also evidently inhibited by the AMPK inhibitor and AMPK siRNA in high glucose-treated INS-1 cells.(5)AMPK activator potentiated the role of geniposide on the protein levels of HO-1,Bcl-2,Bax and the cleavage of caspase-3.All in all,these data collectively suggesting that AMPK might be involved in the role of geniposide regulating GSIS.Besides,we also identified the role of AMPK on the dyfunction and cell injury induced by high concentrations of glucose in pancreatic beta cells,and preliminarily clarified the associated molecular mechanism about that,which provided some new ideas and targets for the prevention and treatment of T2 DM.