Ghrelin对大鼠离体胰腺胰岛素分泌及Glut-2蛋白表达的影响

目的探讨Ghrelin对大鼠离体胰腺组织胰岛素分泌及葡萄糖转运蛋白-2（Glut-2）表达的影响。方法将25只Wistar大鼠随机分为正常对照组（NC组）、高糖组（HCG组）、高糖＋高浓度Ghrelin（10-8mol/L）组（HCG＋HCGh组）、高糖＋中浓度Ghrelin（10-9mol/L）组（HCG＋MCGh组）及高糖＋低浓度Ghrelin（10-10mol/L）组（HCG＋LCGh组）,每组5只。建立大鼠离体胰腺灌注模型,经腹主动脉远端相应灌注低糖（5.5 mmol/L）、单纯高糖（33.3 mmol/L）溶液或加入上述不同浓度Ghrelin的高糖（33.3 mmol/L）溶液。采用ELISA法测定门静脉流出液的胰岛素水平,采用免疫组化染色方法半定量测定Glut-2蛋白在离体胰腺组织中的表达水平,采用透射电镜观察胰岛β细胞的超微结构改变。结果 5组大鼠的空腹血浆葡萄糖（FBG）、空腹血浆胰岛素（FINS）、胰岛素抵抗指数（HOMA-IR）及胰岛素分泌指数（HOMA-β）比较差异均无统计学意义（P〉0.05）。用低糖溶液灌注时,5组大鼠门静脉流出液的胰岛素水平比较差异无统计学意义（P〉0.05）;而用高糖溶液灌注后,胰岛素的分泌在3 min和10～12 min时出现了2个高峰（以HCG＋HCGh组最高）。NC组大鼠胰岛β细胞Glut-2蛋白的平均光密度值高于其余4组（P〈0.05）。透射电镜观察结果显示,高糖各组大鼠离体胰腺的凋亡征象较NC组严重,但HCG＋HCGh组的细胞器损害程度较HCG＋MCGh组及HCG＋LCGh组轻。结论在大鼠离体胰腺中,Ghrelin可促进高浓度葡萄糖诱导的胰岛素分泌,对胰岛β细胞起保护作用。

Effect of Ghrelin on Insulin Secretion and Expression of Glut-2 Protein in Isolated Pancreas of rat

Objective To explore the effect of ghrelin on insulin secretion and expression of glucose transporter protein-2（Glut-2） in isolated pancreas of rats.Methods Twenty five Wistar rats were randomly devided into normal control group（NC group）,high concentration of glucose group（HCG group）,high concentration of glucose with high concentration of ghrelin group（10-8？mol/L,HCG＋HCGh group）,medium concentration of ghrelin group（10-9？mol/L,HCG＋MCGh group）,and low concentration of ghrelin group（10-10？mol/L,HCG＋LCGh group） with 5 rats in each group.The rat isolated pancreas perfusion models were established firstly,then from the distal end of abdominal aortas,the models were perfused with low concentration of glucose（5.5？mmol/L）,high concentration of glucose（33.3 mmol/L） or high concentration of glucose added with different concentrations of ghrelin.Levels of insulin outflowed from portal vein were tested by ELISA method,expression levels of Glut-2 protein were tested by immunohistochemical method, and ultrastructure changes of islet β cell were observed under the transmission electron microscope.Results There were no significant difference on levels of fasting blood glucose（FBG）,fasting insulins（FINS）,homeostasis model of assessment for insulin resistence index（HOMA-IR）,and homeostasis model of assessment for pancreatic β cell function（HOMA-β）,（P0.05）.There were no significant difference on insulin levels of effluent from portal vein of 5 groups（P0.05） when isolated pancreas perfused with 5.5？mmol/L glucose,while had 2 secretion peaks in 3？min and 10-12？min after 33.3 mmol/L glucose perfusion,where HCG＋HCGh group at the top.The mean density value of Glut-2 protein in NC group was higher than that of other 4 groups（P0.05）.The results of transmission electron microscopy showed that apoptosis was lighter in NC group than that of other 4 groups,and apoptosis of HCG＋HCGh group was lighter than that of HCG＋ MCGh group and HCG＋LCGh group.？Conclusions In isolated pancreas of rats,ghrelin promotes high concentration of glucose-stimulated insulin secretion,decreases expression of Glut-2 protein,and protects the islet β cell.