| ObjectiveGlucagon-like peptide 1(GLP1) agonists are promising therapeutic agents in the treatment of diabetes mellitus.It is still unclear that the effect of exendin-4 on pancreatic islets αcell in diabetic rats. We measured the serum glucagon levels by radioimmunoassay in order to study the effect of exendin-4 on the glucagon secretion in diabetic rats.To investigate whether the morphological changes and expression of glucagon in the alpha cell in diabetic rats differ from those in Wistar rats, Pancreas HE staining and Immunohistochemical study was performed. All of these studies were designed to investigate the effects of exendin-4 on the function of pancreatic islets α cell and thus maybe useful in the study of pathophysiology of type 2 diabetes mellitus.MethodsRats were rendered diabetic by a single dose of streptozotocin(STZ,35mg/kg body weight(bw)) intraperitoneally administered 。A total of 40 male Wistar rats were randomly divided into the normal control group(group NC,n=10) and the diabetic model group(n=30). Because of death in the experimental process,thus,totally of 25 STZ-induced type-2 diabetic rats(STZ-rats) were involved in this study.Among the 25 included animals,3 rats in the diabetic control group(DC group), 8 rats in the low dose of EX-4 group(EXLgroup)( 5μg/kg),9 rats in the high dose of EX-4 group(EXHgroup,n=9)(20μg/kg). All rats were sacrificed after exendin-4 treatment for eight weeks. Timing twice daily(9:00 am and 5:00 pm) injection, NC, DC were injected PBS, for 8 weeks. Eight weeks after the intervention, fasting 12 h, the next morning,to the administration of 0h, 1h, 2h, 3h, blood from jugular venous were drawn to measure blood sugar, serum samples of serum glucagon were measured by radioimmunoassay. Pancreatic tissue is stripped, is fixed in neutral buffered formalin, paraffin-embedded tissue was cut into pieces for later use. HE staining of paraffin sections to was performed to observe the morphological changes of α cell,the levels of glucagon expression were observed by immunohistochemical, in order to observe the quantitative changes of α cell.Results1.The levels of blood glucagon in each groupThe blood glucagon in the DC group、EXL group and the EXH group were much higher than that in the NC group before intervention. In this experiment, after 8 weeks of intervention, we observed significantly lower levels of blood glucagon from rats with type 2 diabetes than diabetic controls, in which the EXH group experienced much lower levels of blood glucagon.2.Time course graphs showing the effect of exendin-4 treatment on blood glucose levels in each groupDiabetic rats had significantly(P<0.05) elevated blood glucose levels compared with normal control group. Treatment of diabetic rats with exendin-4 resulted in a significant(P<0.05) reduction in blood glucose level compared with untreated diabetic rats. The levels of blood glucose in the EXH group were lower than that in the EXL group. The results show that exendin-4 can reduce the blood glucose in a dose-dependent manner compared with basal levels.3.The changes of pancreas α cells with immunohistochemical stainingThe diabetic rats’ pancreases had more glucagon-positive cells than those of control animals. While exendin-4 treatment for 8 weeks resulted in significant decreases in the percentage distribution of glucagon-positive cells in both control and diabetic groups. Besides, there was a reduction of the percentage of pancreatic islet α cells in the EXH group than those in the EXL group.4. Pancreatic tissue of rats’ HE staining resultsThe volume of islets in NC group is relatively large, evenly distributed in the nucleus cytoplasm.. Endocrine islets,and exocrine pancreatic lobules are clearly visible. In DC and experimental group, the volume of islet cells is reduced, and the is closely distributed,red blood cells can be seen between the islet capillaries distributed within the lumen. Islet β cells showed varying degrees of degeneration. Acinar volume decreases, the cytoplasm becomes loose, the cells showed nuclear condensation and darker stained and nucleus aer distributed at the bottom of the cytoplasm.While the islet size DC group decreases meanwhile the number reduced. Compared with the DC group, both the endocrine and exocrine pancreatic gland lobule in the EX group is clearly visible, but the volume of the islet increases. Islet cell nuclear lysis and necrosis in EXH group is less than in EXL group.ConclusionExendin-4 can reduced the amounts of pancreatic islets αcell in diabetic rats, suppressed glucagon secretion, and therefore suppressed the function of pancreatic islets α cell. |
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