Akkermansia muciniphila的肠道黏膜屏障调控作用及其机制研究

Lipid metabolic disorders associated metabolic diseases are characterized by altered gut microbiota, chronic low-grade inflammation, and gut barrier disruption. Evidence has shown that microbial composition and the mechanisms of interaction with the host that affect gut barrier function and thus reduces metabolic endotoxemia, might be the key regulators of metabolic health. Akkermansia muciniphila, which is a mucin-degrading bacterium that resides in the mucus layer, is significantly reduced in obese patients, which suggests that A. muciniphila is a potential regulator of lipid metabolism. Our previous preliminary experimental study in animals has found that A. muciniphila can reverse the lipid metabolism in rats with high-fat diet (HFD), however, its mechanisms remains unclear.The aim of our present study was to investigate the role of A. muciniphila on the intestinal mucosal barrier in the rat models of obesity induced by high fat diet. The effects of A. muciniphila on intestinal mucosal barrier were observed in the intestinal microbiota, metabolic endotoxemia, inflammatory response, lipid metabolism and its key regulators such as Fasting-induced adipose factor / angiopoietin-like protein 4 (Fiaf/Angptl4). And we also try to understand the role of A. muciniphila on the NOD1 related signaling transduction pathways by up-regulating and down-regulating the expression of NOD1 in HT-29 cell lines. Then we also explore the changes of key protein or protein kinase in the glucose and lipid metabolism related signaling transduction pathways. According to our present study, we will understand the specific mechanisms of A. muciniphila in the intestinal mucosal protection and lipid metabolism regulation in a deeper level, which will reveal the role of A. muciniphila in the development of dyslipidemic related metabolic diseases and provide a scientific basis for A. muciniphila to be developed into probiotics.

脂肪代谢紊乱相关代谢性疾病的特征是肠道菌群改变、慢性低度炎症和肠道黏膜屏障破坏。有证据表明肠道黏膜屏障完整性有助于阻止内毒素入血，是肠道菌群调控代谢性疾病慢性低度炎症的关键环节，Akkermansia muciniphila (Akk)在肥胖宿主体内显著减少，具有潜在的脂肪代谢调控活性，前期研究已发现Akk对高脂饮食大鼠脂肪代谢的逆转效应，但其作用机制不明。本课题拟采用Akk干预高脂饮食肥胖大鼠模型，从Akk对肠道菌群、代谢性内毒素血症、炎症反应、脂肪代谢及其关键调控因子的影响方面解析Akk对肠道黏膜屏障的调控作用，并采用正向和反向调控HT-29细胞上NOD1的表达，探明Akk可通过NOD1介导的相关信号转导通路调控肠道黏膜屏障，明确Akk参与肠道黏膜屏障调控作用的可能分子机制，进而揭示Akk在代谢性疾病发生发展过程中的作用规律，为开发Akk为肠道益生菌提供科学依据。

肠道菌群失衡、慢性低度炎症和肠黏膜屏障破坏是脂肪代谢紊乱相关代谢性疾病的主要特征。研究发现，Akkermansia muciniphila (Akk)在众多代谢性疾病中的丰度显著下降，这一改变可能与代谢性疾病的发生密切相关。本研究制备了高脂饮食肥胖小鼠模型，而后应用Akk进行干预，发现Akk可显著降低肥胖小鼠的体重和脂肪含量，可降低系统性炎症反应，重建肠道菌群，并可显著改善肠道黏膜屏障功能，提高脂肪代谢关键蛋白Angptl4的表达，提示AKK可以调控肠道黏膜脂质代谢。进一步对HT-29细胞上的NOD1受体进行siRNA干扰，采用Akk进行干预NOD1沉默的HT-29细胞，不能有效的提高紧密连接蛋白Occludin的水平，发现其可通过NF-kB信号转导通路发挥黏膜免疫调控作用。这些研究揭示了Akk可通过NOD1介导的NF-kB信号转导通路发挥肠道黏膜屏障功能的调控作用，显著改善脂肪代谢，改善代谢性疾病的临床表征，提示Akk是一株潜在的益生菌菌株，本研究将为开发Akk为肠道益生菌提供实验基础和理论依据。