Patanè G, Piro S, Anello M, Rabuazzo A M, Vigneri R, Purrello F
Institute of Internal Medicine, Endocrinology and Metabolism, 'Signorelli' Diabetes Center, University of Catania, Ospedale Garibaldi, Catania, Italy.
Br J Pharmacol. 2000 Mar;129(5):887-92. doi: 10.1038/sj.bjp.0703131.
An increased sensitivity to glucose was observed in islets pre-exposed for 1 h to glibenclamide (0.1 micromol 1(-1)), but not to tolbutamide (100 micromol l(-1)), as indicated by a shift to the left of the dose-response curve (EC(50) at 5.8+/-0.3 mmol l(-1) glucose vs 10.6+/-0.8 in control islets; n=11, P<0.005). According to this secretory pattern also glucose utilization at 2.5 and 5.0 mmol l(-1) glucose was higher in islets exposed to glibenclamide. Since binding to mitochondria results in an increased enzyme activity, we measured hexokinase (HK) and glucokinase (GK) activity both in a cytosolic and in a mitochondrion-enriched fractions. Cytosolic hexokinase activity was similar in islets exposed to glibenclamide and in control islets but mitochondrial hexokinase activity was significantly increased after exposure to glibenclamide (124+/-7 vs 51+/-9 nmol microgram prot(-1) 90 min(-1), P<0.01), with no change in the enzyme protein content. In contrast, glucokinase activity in the two groups of islets was similar. When in islets < exposed to glibenclamide hexokinase binding to mitochondria was inhibited by the addition of 20 nmol l(-1) dicyclohexylcarbodiimide (DCC), no increase of glucose sensitivity was observed (EC(50) 10.9+/-1.3 mmol l(-1) glucose, n=3, similar to that of control islets). These data indicate that a 1 h exposure to glibenclamide causes the beta cell to become more sensitive to glucose. This increased sensitivity is associated with (and may be due to) an increased hexokinase activity, in particular the mitochondrial-bound, more active, form. This mechanism may contribute to the hypoglycemic action of this drug.
预先用格列本脲（0.1微摩尔/升）处理1小时的胰岛对葡萄糖的敏感性增加，但用甲苯磺丁脲（100微摩尔/升）处理则无此现象，剂量-反应曲线向左移动表明了这一点（在5.8±0.3毫摩尔/升葡萄糖时的半数有效浓度（EC50）与对照胰岛中的10.6±0.8相比；n = 11，P < 0.005）。根据这种分泌模式，暴露于格列本脲的胰岛在2.5和5.0毫摩尔/升葡萄糖时的葡萄糖利用率也更高。由于与线粒体结合会导致酶活性增加，我们在富含线粒体的部分和胞质部分都测量了己糖激酶（HK）和葡萄糖激酶（GK）的活性。暴露于格列本脲的胰岛和对照胰岛中的胞质己糖激酶活性相似，但暴露于格列本脲后线粒体己糖激酶活性显著增加（124±7对51±9纳摩尔/微克蛋白-1 90分钟-1，P < 0.01），酶蛋白含量无变化。相比之下，两组胰岛中的葡萄糖激酶活性相似。当在暴露于格列本脲的胰岛中加入20纳摩尔/升二环己基碳二亚胺（DCC）抑制己糖激酶与线粒体的结合时，未观察到葡萄糖敏感性增加（EC50为10.9±1.3毫摩尔/升葡萄糖，n = 3，与对照胰岛相似）。这些数据表明，暴露于格列本脲1小时会使β细胞对葡萄糖更敏感。这种敏感性增加与（可能是由于）己糖激酶活性增加有关，特别是线粒体结合的、更具活性的形式。这种机制可能有助于该药物的降血糖作用。
