The Protective Effect Of Oligopeptide FLPNF On Dexamethasone-Induced Apoptosis Of Islet Beta Cells

Objective: To investigate the effect of oligopeptide FLPNF on islet beta cell apoptosis and glucose stimulated insulin secretion declines induced by dexamethasone and to explore their potential mechanisms involved.Methods: The rat islet beta cell line INS-1 strain was studied as research object when the research groups included group Control,group DEX,group FLPNF,group FLPNF+DEX,group Ghrelin,group Ghrelin+DEX,group NFGAIL and group NFGAIL+DEX.CCK-8 assay was used to detect the cell viability.TUNEL staining method and AV(Annexin VFITC)/PI method were used to detect cell apoptosis and evaluate the ratio of cell apoptosis.Western blot was used to evaluate the expression of apoptosis-related proteins including Bcl-2,Bax and cleaved Caspase-3.ELISA assay was used to detect the cell function of glucose stimulated insulin secretion.Western blot was also used to evaluate the expression of glucose transport-related protein Glut2.Software Graph Pad Prism 5.0 was used to process the data obtained from each index,with p <0.05 as statistically significant difference.Results: Under the treatment of the oligopeptide FLPNF alone,the cell viability and status of INS-1 cells were not significantly changed,the apoptosis rate and apoptosis-related proteins were not significantly varied,the expression of the glucose transport-related protein Glut2 was not markedly elevated while the amount of glucose stimulated insulin secretion was not significantly changed.Under the treatment of dexamethasone alone,cell viability of INS-1 cell was obviously decreased with the nuclear shrinkage and cracking observed as cell damage,the density of cell apoptosis was higher with the apoptosis rate reaching(40.6 + 2.4)%,the expression of apoptosis related proteins Bcl-2 was significantly reduced,as the expression of Bax and cleaved Caspase 3 was increased obviously,the glucose stimulated insulin secretion was markedly decreased,and the expression of glucose transport-related protein Glut2 was significantly reduced;After dexamethasone combined with oligopeptide FLPNF,cell viability of INS-1 cell increased with cell state improved,apoptotic cell went sparse,as the apoptosis rate fell down to(27.2 +2.0)%(P<0.001),the expression of apoptosis related proteins Bcl-2 was upregulated,concurrently the expression of Bax and cleaved Caspase-3 were downregulated,glucose stimulated insulin secretion was enhanced,and the expression of glucose transport-related protein Glut2 was upregulated,the oligopeptide FLPNF significantly reduced the dexamethasone-induced apoptosis of INS-1 cells as well as improved the glucose stimulated insulin secretion;In the group Ghrelin,which was set as a positive control,there were no significant changes in various indexes of the INS-1 cells,When combined with dexamethasone,compared with the group under the treatment of dexamethasone alone,cell viability of INS-1 cells increased,the apoptosis rate decreased,the expression of apoptosis related proteins Bcl-2 was significantly increased,and the expression of Bax and cleaved Caspase-3 were transparently decreased.There was no significant change in various indexes of INS-1 cells under the treatment of NFGAIL alone,when dexamethasone combined with oligopeptide NFGAIL,there was no significant change in the expression of apoptosis-related proteins in INS-1 cells compared with the group under the treatment of dexamethasone alone,while the apoptosis density of INS-1 cells was slightly higher than that under the treatment of dexamethasone alone.Conclusion: The oligopeptide FLPNF protects against the islet beta cell apoptosis induced by dexamethasone through upregulating expression of Bcl-2 and downregulating expression of Bax and cleaved Caspase-3,meantime,the oligopeptide FLPNF improves the function of glucose stimulated insulin secretion by upregulating protein Glut2 in islet beta cells.Above all,oligopeptide FLPNF has an apparent protective effect against islet beta cell apoptosis induced by dexamethasone.