Study of impaired insulin exocytosis in diabetes mellitus by imaging technique

近年来，世界范围内糖尿病患者数量显著增加，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紧迫任务。由于胰岛素释放受损是2型糖尿病的特征，阐明正常和受损的胰岛素分泌机制是重要的。在本研究中，我们开发了全内反射荧光（TIRF）成像系统，并将该成像系统应用于胰腺β细胞。该系统通过监测胰岛素颗粒在质膜上的动态运动，是揭示胰岛素对接融合系统的有力工具。我们发现胰岛素释放第一阶段的颗粒融合主要来自于形态上先前停泊的颗粒，而第二阶段的颗粒融合来自于最初储存在细胞内的新颗粒。我们还发现先前停靠的颗粒与质膜上的syntaxin 1A簇共定位，并从它们融合。最后我们发现，在糖尿病β细胞中，syntaxin 1A簇减少，从而码头颗粒减少，导致糖尿病状态下第一阶段胰岛素释放减少。

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.