IAPP对钙调控胰岛素分泌的影响及其在β细胞功能减退中的作用研究

The mechanism of islet amyloid (mainly composed of IAPP) of its inhibition of insulin secretion in pancreatic islet remains unclear. Studies suggest that high concentrations of IAPP accelerate β-cell damage and apoptosis, resulting in reduction of insulin secretion. However, the applicant's preliminary researches have proved that high concentrations of IAPP can decrease high voltage activated calcium channel current and the level of intracellular calcium under the high-glucose condition in a short period of time; sulfonylurea-stimulated insulin secretion reduction is synchronized with the intracellular calcium concentration decrease. The changes of intracellular calcium concentration are closely related to insulin secretion. Therefore, IAPP is very likely to affect insulin secretion by its influence on the calcium channel function and its related signal transduction pathways. This project intends to focus on researching the impact of IAPP on L-type calcium channel in β-cell by means of techniques such as patch clamp, immune co-precipitation, and confocal microscopy and through direct acting or ATP-sensitive potassium channel. Meanwhile to make analysis of the influence of IAPP on the R-type calcium channels and intracellular calcium stores to clarify any other routes that would reduce the IAPP levels of intracellular calcium; analysis of the effect of IAPP on ATP-sensitive potassium channels as sulfonylurea drugs' targets; and to explore its relationship with secondary sulfonylurea failure. Our aim is to provide some new ideas for early clinical intervention and the development of new drugs for diabetes.

胰岛淀粉样蛋白（主要成分IAPP）在胰岛中的沉积抑制胰岛素分泌的机制尚不完全清楚，诸多研究认为高浓度IAPP使β细胞损伤凋亡加速，导致胰岛素分泌减少。但申请人前期研究发现高浓度IAPP短时间内可使高糖条件下β细胞高电压激活钙通道电流减小，胞内钙离子浓度降低；磺脲类降糖药刺激的胰岛素分泌减少且与胞内钙离子浓度降低同步。胞内钙离子浓度变化与胰岛素分泌密切相关，因此IAPP极有可能通过影响钙通道功能及其相关信号转导途径而影响胰岛素分泌。本课题拟重点以膜片钳、免疫共沉淀和共聚焦显微镜等技术研究IAPP对β细胞L型钙通道的影响，是直接作用还是通过ATP敏感钾通道而介导。同时分析IAPP对R型钙通道及胞内钙库的影响，以明确IAPP使胞内钙离子减少的其他途径；分析IAPP对磺脲类降糖药作用靶标ATP敏感钾通道的影响，探讨其与磺脲类降糖药继发失效的相关性，为糖尿病的早期临床干预及新药研发提供新思路。

胰岛淀粉样蛋白（主要成分IAPP）在胰岛中的沉积抑制胰岛素分泌的机制尚不完全清楚，诸多研究认为高浓度IAPP使β细胞损伤凋亡加速，导致胰岛素分泌减少。但申请人前期研究发现高浓度IAPP短时间内可使高糖条件下β细胞高电压激活钙通道峰值电流减小，胞内Ca2+浓度降低；磺脲类降糖药刺激的胰岛素分泌减少且与胞内Ca2+浓度降低同步。胞内Ca2+浓度变化与胰岛素分泌密切相关，因此IAPP极有可能通过影响钙通道功能及其相关信号转导途径而影响胰岛素分泌。本课题重点研究了（1）IAPP对INS-1细胞KATP通道及胞内钙库的影响，同时分析了（2）IAPP对钾通道的作用机制。结果表明：（1）IAPP短时间孵育后抑制葡萄糖刺激的INS-1细胞内Ca2+浓度的升高作用主要是通过影响膜上钙通道实现的，与胞内钙库Ca2+的释放无直接相关性；（2）关于IAPP对钾通道的作用机制的数据正在整理拟发表过程中（故请暂缓公开，具体研究内容可见后面正文）。