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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

刘方, 朱依纯^*

复旦大学上海医学院生理学与病理生理学系，上海 200032

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、300 nmol/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、300 nmol/kg)使大鼠血浆胰岛素浓度在腹腔注射葡萄糖后15 min 显著下降，并且使大鼠血糖在腹腔注射葡萄糖后90 min 明显升高。βTC-6 细胞孵育实验结果显示，UII 孵育2 h 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。

关键词： 尾加压素I I ; 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：R3

[Urotensin II inhibits glucokinase expression and glucose induced insulin secretion.] [Ariticle in Chinese]

LIU Fang, ZHU Yi-Chun^*

Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai 200032, China

Abstract

The purpose of the present study is to investigate the effects of urotensin II (UII) on insulin secretion in islet β cells and theunderlying mechanism. Glucose tolerance test was performed in Wistar rats to evaluate the effect of UII on the levels of plasma glucoseand insulin. Static incubation experiment was employed to investigate the effect of UII on glucose-induced insulin secretion (GIIS) inβTC-6 cells. After the incubation, insulin content and mRNA level in βTC-6 cells were analyzed. Finally, Western blot was used to findout if UII could change the expression levels of pancreatic duodenal homeobox-1 (PDX-1) and glucokinase (GCK). It was observed thatintravenous administration of UII (30, 300 nmol/kg) resulted in a significant decrease in insulin level 15 min after glucose load, andinduced an obvious increase in plasma glucose 90 min after the load. In vitro, two hours of UII incubation inhibited GIIS in βTC-6 cellswithout affecting insulin content and mRNA levels. The inhibitory effect of UII was blocked by UII receptor antagonist (urantide), andpartially 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 transcriptionin β cells, was not affected. These results suggest that UII-induced inhibition of GIIS in βTC-6 cells are mediated by UII receptorand PKC pathway, as well as somatostatin receptor which could be activated by high dose of UII. The inhibitory effect of UII oninsulin secretion is rather associated with a suppression of GCK expression than a regulation on PDX-1 expression.

Key words: urotensin II; glucose tolerance; insulin; protein kinase C; glucokinase; receptors, somatostatin

收稿日期：2009-12-22　　录用日期：2010-03-08

通讯作者：朱依纯　　E-mail: yczhu@shmu.edu.cn

引用本文：

刘方, 朱依纯. 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[J]. 生理学报 2010; 62 (2): 129-136.

LIU Fang, ZHU Yi-Chun. [Urotensin II inhibits glucokinase expression and glucose induced insulin secretion.] [Ariticle in Chinese] . Acta Physiol Sin 2010; 62 (2): 129-136 (in Chinese with English abstract).