选择性阻断胰岛局部RAS对α细胞胰高血糖素分泌功能的调控作用及机制研究

胰高血糖素分泌功能异常在糖尿病及其慢性并发症的发生、发展过程中起重要作用，我们前期研究初步发现阻断胰岛局部肾素血管紧张素系统（RAS）使db/db小鼠血糖改善、β细胞自身胰岛素敏感性增强的同时，胰高血糖素分泌水平降低，但对分泌时相的具体作用和机制尚不清楚。本课题拟运用RNA干扰、葡萄糖灌流、RT-PCR、Western Blot、流式细胞术等实验技术,进一步研究选择性阻断原代胰岛及α细胞株RAS表达对胰高血糖素分泌的调控作用及可能机制，包括胰高血糖素动态分泌时相，胰岛素、生长抑素、GABA等旁分泌激素作用于α细胞的信号通路及其在调控胰高血糖素分泌中的作用，以及对α细胞氧化应激、凋亡的影响。以上研究为进一步阐明RAS阻断防治糖尿病的作用靶点和分子机制提供实验依据，并为糖尿病早期干预提供新的思路和手段。

Dysfunction of glucagon secretion plays an important role in the pathogenesis of type 2 diabetes and its chronic complications. Our previous study has demonstreted preliminarily that intra-islet inhibition of RAS expression led to improved glucose tolerance, increased insulin sensitivity of beta-cell itself, and simultaneously downregulation of glucagon secretion. Yet the detailed impact on glucagon dynamic secretion and potential mechanisms remain unknown. In the present project, by utilizing small interfering RNA (siRNA) to selectively inhibit the expression levels of angiotensin II type 1 receptor (AT1R) in local islet, we aim to investigate the effects of RAS blockage on glucagon dynamic secretion in isolated islets of db/db mice and alpha-cell line via perifusion. To explore the potential mechanisms involved, we plan to examine the activities of signaling pathway of insulin,somatostatin and GABA upon alpha-cell, the level of oxidative stress and apoptosis by RT-PCR, Western Blot,and flow cytometry. Thus may demonstrate part of the mechanisms of diabetes prevention by RAS blockage observed in a series of clinical studies, and provide a new method for early prevention and treatment of diabetes.