肠道菌群介导二甲双胍促进溃疡性结肠炎粘液屏障修复的作用及机制研究

Gut microbiota dysbiosis and intestinal mucus barrier disruption are the important mechanism of ulcerative colitis (UC) pathogenesis. Restoring mucus barrier and promoting mucosal healing is the therapeutic target of UC. Recent studies have found that the classic anti-diabetic agent metformin has extensive effects, and its anti-inflammatory and hypoglycemic effects are most likely to relying on gut microbiota. Our previous study have confirmed that metformin has the effects of alleviating colonic inflammation and even repairing mucus barrier in UC mice model, and the intestinal microbiota composition in UC patients presented the specific reduction of short chain fatty acids(SCFAs) producing bacteria. So, does the gut microbiota mediate the beneficial effects of metformin on promoting restoration of mucus barrier in UC? And what is the specific regulatory mechanism behind it? In this project we try to answer these questions. We will apply a series of microbiomics, fecal transplantation and genetic manipulation methods in animal models, and to evaluate the dynamic changes of intestinal flora and its main metabolites SCFAs before and after metformin-treated UC mice, to investigate the protective effect and possible mechanism of metformin in mucus barrier repair in UC, especially to clarify the mechanism of NLRP6 signalling pathway, the centre regulator of mucus secretion, in the regulation of mucus barrier restoration of metformin. Our purpose is to provide an alternative medicine and a novel idea for the treatment of UC in the perspective of gut barrier repair and restoration.

肠道菌群失衡和粘液屏障受损是溃疡性结肠炎（UC）的重要发病机制，修复屏障、促进粘膜愈合是UC的治疗目标。近年发现，经典抗糖尿病药物二甲双胍的降糖及抗炎作用很可能依赖于肠道菌群。申请者在前期研究中已证实二甲双胍具有改善UC小鼠结肠炎、促进粘液屏障修复的作用，并且发现UC患者肠道菌群出现产短链脂肪酸（SCFAs）菌的特征性减少。那么，肠菌及其代谢产物SCFAs是否介导了二甲双胍促进UC粘液屏障修复的获益效应？其中具体的调控机制是什么？本研究拟在动物整体、组织及分子水平，采用微生物组学、肠菌移植、基因干预等方法，阐明肠菌及其代谢产物SCFAs介导二甲双胍促进UC粘液屏障修复、减缓结肠炎症的潜在作用，并深入探讨以NLRP6炎性小体为中心的粘液屏障调控分子在肠菌/SCFAs介导的二甲双胍保护效应中的具体机制，从肠粘膜屏障修复角度为UC的治疗提供一种新思路和备选药物。

肠道菌群紊乱和粘液屏障受损是溃疡性结肠炎（UC）的重要发病机制。修复粘液屏障、促进粘膜愈合是UC治疗的关键目标。近年研究发现，经典抗糖尿病药物二甲双胍的降糖及抗炎作用很可能依赖于肠道菌群。在本项目中，我们证实了肠上皮屏障一个新的保护性机制：二甲双胍通过调节肠道菌群，特别是富集产SCFAs肠菌，维护肠上皮屏障功能，促进UC粘膜修复。本项目主要采用微生物组学、肠菌移植、基因干预等方法，从动物整体、组织及分子水平阐明二甲双胍促进UC粘液屏障修复、减缓结肠炎症的潜在作用机制。体外实验证明了二甲双胍可以保护单层肠上皮细胞屏障功能，表现为能够显著稳定肠上皮的完整性、抑制细菌易位和降低跨膜转运的通透性。二甲双胍可以通过依赖AMPKα1介导的JNK信号通路激活产生抑制作用，减少紧密连接蛋白丢失和细菌易位的发生，参与保护肠上皮屏障功能。动物实验证实了二甲双胍在小鼠结肠炎中可以促进杯状细胞分化以及粘蛋白分泌，维护粘液屏障功能，减少细菌易位，减轻结肠炎的发生。同时，微生物组测序结果表明二甲双胍可以调节肠道菌群，主要表现为富集肠道产SCFAs菌，特别是Akkermansia muciniphila。抗生素清除肠道菌群可以显著削弱二甲双胍的粘液屏障保护作用。我们进一步发现Akkermansia muciniphila亦可促进杯状细胞粘蛋白分泌，加速粘液屏障修复，进而缓解小鼠结肠炎。这表明二甲双胍可以通过富集Akkermansia muciniphila（产SCFAs菌）进而促进杯状细胞的分化、成熟以及MUC2粘蛋白的合成、分泌，增强粘液屏障功能，减少细菌易位，降低肠道通透性，实现治疗UC的目标。