Ghrelin抑制胰岛β细胞胰岛素释放的机制探讨

The inhibitory effect of ghrelin on insulin release of mouse islet β-cell line and its mechanism

目的探讨ghrelin对小鼠胰腺β细胞株NIT-1细胞胰岛素释放的影响及其作用机制。方法NIT-1细胞与不同浓度ghrelin和高浓度葡萄糖孵育后,放免法测定上清液胰岛素含量,RT-PCR法检测葡萄糖转运子2(GluT2)、胰十二指肠同源盒-1(PDX-1)、含两个跨膜区的内向整流钾通道(Kir6.2)及磺酰脲受体1(SUR-1)等基因的表达。NIT-1细胞与不同浓度ghrelin孵育不同时间后,MTT法检测细胞增殖情况。结果(1)10-9mol/L至10-7mol/L ghrelin呈剂量依赖性抑制NIT-1细胞高浓度葡萄糖刺激的胰岛素释放;(2)10-7mol/L ghrelin显著降低Kir6.2 mRNA的表达,但对GluT2、PDX-1及SUR-1 mRNA的表达无明显的效应;(3)Ghrelin对NIT-1细胞的增殖无显著影响。结论Ghrelin可抑制胰岛β细胞高浓度葡萄糖刺激的胰岛素释放,该效应可能是由于下调ATP敏感性钾通道组成成分Kir6.2基因的表达所致。

Objective To explore the effect of ghrelin on insulin release of mouse pancreatic islet β-cell line （NIT 1 cells） and its probable mechanism. Methods NIT-1 cells were incubated in high- glucose DMEM with ghrelin. Then, the media was sampled for the assay of insulin by RIA. The mRNA expressions of glucose transporter 2 （GluT2）, pancreatic-duodenal homeobox-1 （PDX-1）, inwardly rectifying potassium channel with two transmembrane regions （Kit6.2） and sulphonylurea receptor 1 （SUR-1） in the cells were detected by using RT-PCR. The cell proliferation was determined by MTT assay. Results （1） 10^-9 mol/I, to 10^-7 mol/I, of ghrelin inhibited dose-dependently the high-glucose challenged insulin release of the NIT-1 cells. （2） The mRNA expression of Kir6.2, but not GluT2, PDX land SUR 1, was down-regulated by 10^-7mol/L of ghrelin. （3） Ghrelin had no effect on proliferation of the cells. Conclusions Ghrelin inhibits high glucose induced insulin secre tion of the islet β-cells. This effect may be secondary to the down-regulation for the expression of Kir6.2, a component of ATP sensitive potassium channel.