炎症致胰岛β细胞功能障碍的新机制 - 异常折叠胰岛素原积聚

In the early phase of type 1 diabetes (T1DM), a clear molecular mechanism for increased pro-inflammatory cytokines in islets leading to beta cells dysfunction is still lacking. Previously, we found that, (1) Atypical folded proinsulin precursor molecules exist in beta cells. (2) Pro-inflammatory cytokines resulted in abundant proportion of unfolded proinsulin precursor aggregation intracellularly. (3) Activation of cAMP/PKA signal pathway can promote proinsulin processing and improve secretory dysfunction of beta cells due to abnormal folded proinsulin accumulation significantly. We proposed hypothesis that pro-inflammatory cytokines leading to atypical folded proinsulin precursor molecules accumulation and beta cell dysfunction is associated with cAMP/PKA - unfolded protein response (UPR) signal pathway. This research proposal to illustrate the new mechanism has not been reported. According to the novel viewpoint, islet Min6 beta cells, pancreatic islets and Non-Obese diabetic (NOD) mice model would be employed, and Western blot, isotope labeling strategy, GFP-LC3 fusion tracer proteins transfection, siRNA and transgenic technology would be used to investigate the relationship and mechanisms between intracellular atypical folding/ aggregation of proinsulin precursor molecules and pancreatic beta cells dysfunction under the inflammatic condition. This study would also provide a new avenue for the research and development of drugs on diabetes mellitus in the future.

1型糖尿病（T1DM）早期，胰岛内炎症因子显著增加导致β细胞功能障碍，其发生机制仍不清楚。我们前期研究发现：①胰岛β细胞内存在异常折叠的胰岛素原前体分子；②炎症因子导致β细胞内异常折叠胰岛素原大量积聚；③激活cAMP/PKA信号通路能够显著改善因异常折叠胰岛素原积聚所致的β细胞功能障碍。因此，我们提出假说：炎症因子导致异常折叠胰岛素原在胞内大量积聚并引发β细胞功能障碍，其机制可能与cAMP/PKA-UPR信号通路有关。本研究所提出的这一新机制尚未见报道。我们将从这一新视点，通过胰岛β细胞系、离体胰岛和非肥胖糖尿病（NOD）小鼠，采用免疫印迹杂交、同位素代谢标记、GFP-LC3 融合蛋白转染示踪、siRNA和转基因等技术手段，从分子、细胞、组织及动物整体水平，为揭示炎症环境下胰岛β细胞内异常折叠胰岛素原的积聚与胰岛β细胞功能障碍的相关关系和发生机制奠定基础，为糖尿病的治疗药物研发提供新思路。

项目的背景：当胰岛β细胞遭受炎症因子的持续强烈攻击（T1DM）时，UPR信号通路处于过度激活状态。然而，炎症环境下，胰岛β细胞内胰岛素原前体分子积聚的发生机制是什么？如何继而引发β细胞的功能障碍？减轻异常折叠胰岛素原积聚状态能否有效恢复β细胞功能，这些仍有待进一步研究。.主要研究内容：①探究炎症致异常折叠胰岛素原积聚对胰岛β细胞功能的影响；②解析炎症致异常折叠胰岛素原积聚的发生机制以及与胰岛β细胞功能障碍的因果关系；③明确cAMP/PKA-UPR信号通路在异常折叠胰岛素原积聚引发β细胞功能障碍过程中的作用；④通过T1DM模型动物实验论证异常折叠胰岛素原积聚是炎症引发胰岛β细胞功能障碍的重要机制。.重要结果：①炎症因子导致胰岛β细胞数量减少和功能障碍；②NOD小鼠随着病程进展，胰岛β细胞数量逐渐减少；③炎症因子抑制Min6细胞增殖，增加Min6细胞凋亡，影响Min6细胞周期、亚细胞结构和胰岛素分泌数量。.关键数据：①胰岛β细胞内存在异常折叠的胰岛素原前体分子；②胰岛素原异常折叠和胞内积聚影响胰岛素原单体的生成；③ cAMP/PKA途径参与胰岛素原异常折叠和胰岛素分泌；④炎症因子导致胰岛素原异常折叠和积聚；⑤炎症因子对Min6细胞LncRNA表达谱的影响，继而影响胰岛β细胞的凋亡；⑥炎症因子干扰Min6细胞代谢组学：对嘧啶代谢和三羧酸（TCA）循环均有影响。.科学意义：①我们在研究基础上提出糖尿病发生机制新理论：β细胞内结构成熟的胰岛素原单体和未正常折叠的胰岛素原前体分子之间平衡被打破时，大量异常折叠胰岛素原滞留于胞内，进而引发胰岛β细胞功能障碍。②本课题组证实：炎症因子加重胰岛β细胞内异常折叠的胰岛素原前体分子的积聚状态，cAMP/PKA-UPR途径参与异常折叠胰岛素原积聚、引发β细胞功能障碍。