Study of impaired insulin exocytosis in diabetes mellitus by imaging technique

近年来，糖尿病患者在全球范围内显著增加，并引起脑血管疾病和心血管事件，因此，糖尿病患者的发病预防和血糖控制已成为人类健康和医疗经济的当务之急。由于2型糖尿病患者的胰岛素分泌功能受损，因此阐明正常和受损的胰岛素分泌机制具有重要意义。在本研究中，我们开发了全内反射荧光（TIRF）成像系统，并将此成像系统应用于胰腺β细胞。我们的系统是一个强大的工具，揭示胰岛素对接和融合系统，通过监测胰岛素颗粒在质膜上的动态运动。我们发现，在第一阶段胰岛素释放的颗粒融合起源于形态学上以前停靠的颗粒，而在第二阶段的颗粒融合来自最初储存在细胞内的新人。我们还发现之前对接的颗粒与质膜中的突触融合蛋白1A簇共定位，并与它们融合。最后我们发现糖尿病状态下β细胞中syntaxin 1A簇减少，从而对接颗粒减少，导致胰岛素第一时相释放减少。

In these years the number of diabetic patients significantly increased worldwide and caused cerebrovascular disorder and heart vascular events, therefore, the onset prevention and restricted blood sugar levels control of diabetic patients are regarded as urgent business for both human health and medical economy. Because impaired insulin release is characteristics in type 2 diabetes, to elucidate the mechanism of normal and impaired insulin exocytosis is important. In this study, we developed the imaging system of total internal reflection fluorescence(TIRF) and applied this imaging system to pancreatic beta cells. Our system is a powerful tool for disclosure of insulin docking and fusion system by monitoring the dynamic motion of insulin granules on the plasma membrane. We found that granules fusing during the first phase insulin release originated mostly from morphologically previously docked granules, whereas granules fusing during the second phase arose from newcomers that were originally stored intracellulary. We also found that previously docked granules were colocalized with syntaxin 1A clusters in the plasma membrane, and fused from them. Finally we found that in diabetic beta cells, syntaxin 1A clusters decreased, thereby, docked granules decreased, as a result, first phase of insulin release decreased in the diabetic status.