Leloup Corinne, Tourrel-Cuzin Cécile, Magnan Christophe, Karaca Melis, Castel Julien, Carneiro Lionel, Colombani Anne-Laure, Ktorza Alain, Casteilla Louis, Pénicaud Luc
Department of Metabolism, Plasticity, and Mitochondria, Unité Mixte de Recherche 5241, Centre National de la Recherche Scientifique-Université Paul Sabatier, Institut Fédératif de Recherche 31, Toulouse, France.
Diabetes. 2009 Mar;58(3):673-81. doi: 10.2337/db07-1056. Epub 2008 Dec 10.
Insulin secretion involves complex events in which the mitochondria play a pivotal role in the generation of signals that couple glucose detection to insulin secretion. Studies on the mitochondrial generation of reactive oxygen species (ROS) generally focus on chronic nutrient exposure. Here, we investigate whether transient mitochondrial ROS production linked to glucose-induced increased respiration might act as a signal for monitoring insulin secretion.
ROS production in response to glucose was investigated in freshly isolated rat islets. ROS effects were studied using a pharmacological approach and calcium imaging.
Transient glucose increase from 5.5 to 16.7 mmol/l stimulated ROS generation, which was reversed by antioxidants. Insulin secretion was dose dependently blunted by antioxidants and highly correlated with ROS levels. The incapacity of beta-cells to secrete insulin in response to glucose with antioxidants was associated with a decrease in ROS production and in contrast to the maintenance of high levels of ATP and NADH. Then, we investigated the mitochondrial origin of ROS (mROS) as the triggering signal. Insulin release was mimicked by the mitochondrial-complex blockers, antimycin and rotenone, that generate mROS. The adding of antioxidants to mitochondrial blockers or to glucose was used to lower mROS reversed insulin secretion. Finally, calcium imaging on perifused islets using glucose stimulation or mitochondrial blockers revealed that calcium mobilization was completely reversed using the antioxidant trolox and that it was of extracellular origin. No toxic effects were present using these pharmacological approaches.
Altogether, these complementary results demonstrate that mROS production is a necessary stimulus for glucose-induced insulin secretion.
胰岛素分泌涉及复杂的事件，其中线粒体在将葡萄糖检测与胰岛素分泌相耦合的信号产生中起关键作用。关于线粒体活性氧（ROS）生成的研究通常集中在长期营养暴露方面。在此，我们研究与葡萄糖诱导的呼吸增加相关的短暂线粒体ROS产生是否可能作为监测胰岛素分泌的信号。
在新鲜分离的大鼠胰岛中研究了对葡萄糖的ROS产生情况。使用药理学方法和钙成像研究了ROS的作用。
葡萄糖从5.5毫摩尔/升短暂增加至16.7毫摩尔/升刺激了ROS的产生，抗氧化剂可使其逆转。抗氧化剂使胰岛素分泌呈剂量依赖性减弱，且与ROS水平高度相关。在存在抗氧化剂的情况下，β细胞无法对葡萄糖分泌胰岛素与ROS产生减少有关，且与高水平ATP和NADH的维持情况相反。然后，我们研究了作为触发信号的ROS（mROS）的线粒体来源。线粒体复合物阻滞剂抗霉素和鱼藤酮可模拟胰岛素释放，它们会产生mROS。向线粒体阻滞剂或葡萄糖中添加抗氧化剂以降低mROS可逆转胰岛素分泌。最后，对灌注胰岛进行钙成像，使用葡萄糖刺激或线粒体阻滞剂，结果显示使用抗氧化剂生育三烯酚可完全逆转钙动员，且钙动员源于细胞外。使用这些药理学方法未出现毒性作用存在。
总之，这些互补的结果表明，mROS的产生是葡萄糖诱导胰岛素分泌的必要刺激因素。
