尾加压素Ⅱ抑制葡萄糖激酶的表达和葡萄糖诱导的胰岛素分泌  

Urotensin Ⅱ inhibits glucokinase expression and glucose-induced insulin secretion

作　　者：刘方[1] 朱依纯[1] 

机构地区：[1]复旦大学上海医学院生理学与病理生理学系,上海200032

出　　处：《生理学报》2010年第2期129-136,共8页Acta Physiologica Sinica

基　　金：supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (No. 2009ZX09303-006; 2009ZX09301-011)

摘　　要：本研究旨在探讨尾加压素II(urotensin II,UII)对胰岛β细胞功能的影响及其机制。在整体实验中,采用Wistar大鼠进行糖耐量试验,检测不同剂量UII(3、30、300nmol/kg)对大鼠血糖和胰岛素水平的影响;在细胞实验中,βTC-6细胞孵育实验检测UII对葡萄糖引起的胰岛素分泌(glucose-induced insulin secretion,GIIS)的影响,酸化乙醇抽提法和实时荧光定量PCR分别测定细胞内胰岛素含量和mRNA的水平,Western blot检测胰十二指肠同源盒1(pancreatic duodenal homeobox-1,PDX-1)和葡萄糖激酶(glucokinase,GCK)表达水平。糖耐量试验结果显示,相对对照组,急性静脉注射较高剂量的UII(30、300nmol/kg)使大鼠血浆胰岛素浓度在腹腔注射葡萄糖后15min显著下降,并且使大鼠血糖在腹腔注射葡萄糖后90min明显升高。βTC-6细胞孵育实验结果显示,UII孵育2h能抑制βTC-6细胞的GIIS,但是对细胞内的胰岛素含量和mRNA水平没有影响。UII对GIIS的抑制作用可以被UII受体拮抗剂urantide所阻断,部分被蛋白激酶C(protein kinase C,PKC)非特异性抑制剂chelerythrine chloride(CTC)和生长抑素受体非特异性拮抗剂cyclosomatostatin(CSS)所阻断。Western blot结果显示,UII抑制了βTC-6细胞内GCK的表达,但对PDX-1表达量没有影响。以上结果表明,UII通过激活其特异性受体(较高浓度的UII可能同时激活生长抑素受体)抑制胰岛β细胞GIIS,其作用机制涉及PKC通路的激活、GCK表达受抑所引起的胰岛素颗粒胞吐作用的减弱,但不涉及胰岛素本身表达的下降。The purpose of the present study is to investigate the effects of urotensin II （UII） on insulin secretion in islet β cells and the underlying mechanism.Glucose tolerance test was performed in Wistar rats to evaluate the effect of UII on the levels of plasma glucose and insulin.Static incubation experiment was employed to investigate the effect of UII on glucose-induced insulin secretion （GIIS） in βTC-6 cells.After the incubation,insulin content and mRNA level in βTC-6 cells were analyzed.Finally,Western blot was used to find out if UII could change the expression levels of pancreatic duodenal homeobox-1 （PDX-1） and glucokinase （GCK）.It was observed that intravenous administration of UII （30,300 nmol/kg） resulted in a significant decrease in insulin level 15 min after glucose load,and induced an obvious increase in plasma glucose 90 min after the load.In vitro,two hours of UII incubation inhibited GIIS in βTC-6 cells without affecting insulin content and mRNA levels.The inhibitory effect of UII was blocked by UII receptor antagonist （urantide）,and partially blunted by protein kinase C （PKC） inhibitor （chelerythrine） and somatostatin receptor antagonist （cyclosomatostatin）.Moreover,we found that GCK protein level was significantly reduced by UII,while PDX-1,a key regulator of insulin gene transcrip- tion in β cells,was not affected.These results suggest that UII-induced inhibition of GIIS in βTC-6 cells are mediated by UII receptor and PKC pathway,as well as somatostatin receptor which could be activated by high dose of UII.The inhibitory effect of UII on insulin secretion is rather associated with a suppression of GCK expression than a regulation on PDX-1 expression.

关 键 词：尾加压素II 糖耐量 胰岛素 蛋白激酶C 葡萄糖激酶 生长抑素受体 

分 类 号：R587.1[医药卫生—内分泌]