基于粪菌移植的麦冬多糖经肠道菌群-胆汁酸轴抗NAFLD起效机制研究

This project was aimed to investigate the mechanism of the anti-NAFLD effects of MDG-1, a polysaccharide extracted from the root of Ophiopogon japonicas. In our previous studies, MDG-1 was shown to block the progression of NAFLD while regulating the intestinal flora in a diet-induced obesity (DIO) mice model. In addition, the polysaccharide also had the potential beneficial effects on the bile acids metabolism profile. Based on these, in this research, we firstly raised the hypothesis that the possible mechanism of the anti-NAFLD effect of MDG-1 was through the gut microbiota-bile acids axis. .To prove this hypothesis, we attempted to build a fecal microbiota transplantation model from a DIO mice model, aimed to reinforce the foundation between MDG-1 and gut-microbiota by finding the consistency from both two sides of the fecal microbiota transplantation model through pharmacodynamics, bile acid metabolism and bacterial diversity analysis. Furthermore, by using the environmental factors analysis, antibiotics and Z-Guggulsterone, we tried to uncover the relationships between gut microbiota and bile acids signaling pathway to facilitate to reveal the detail metabolism of MDG-1.

本项目围绕麦冬多糖MDG-1抗非酒精性脂肪性肝病（non-alcoholic fatty liver disease，NAFLD）的起效机制展开研究。前期已知MDG-1可有效延缓NAFLD的进展，改善膳食诱导肥胖（diet-induced obesity, DIO）小鼠肠道菌群微环境，并影响体内胆汁酸的代谢水平。基于此，本项目首次提出MDG-1通过影响肠道菌群-胆汁酸轴起到延缓NAFLD进展的科学假说。.本项目以DIO小鼠为研究对象，引入粪菌移植的实验设计，通过挖掘供、受体小鼠在药效、胆汁酸代谢及菌群多样性上存在的一致性，夯实MDG-1与菌群靶点间的研究基础。又通过环境因子关联分析，揭示多糖调控下的菌群与胆汁酸代谢通路之间的紧密联系。再运用抗生素干扰和受体抑制剂，反向验证由“多糖-菌群-胆汁酸代谢-宿主疗效”构成的科学假说。最终，阐明麦冬多糖经肠道菌群-胆汁酸轴抗NAFLD的具体起效机制。

麦冬多糖是从传统中药麦冬中提取得到的一种β-D-果聚糖。课题组前期研究发现，口服麦冬多糖具有减重、降脂，干预胆汁酸重吸收，并对肠道菌群的整体结构有影响。且因机体无代谢β-D-型果聚糖的酶，推测其起效机制可能是与肠道菌群有关。基于此，研究以DIO小鼠模型为研究对象，引入粪菌移植（fecal microbiota transplantation, FMT）的实验设计，借助分子生物学、代谢组学和宏基因组学分析手段，揭示“多糖-肠道菌群-宿主药效”间的相互关联。. 整体药效学研究发现，口服麦冬多糖及FMT可通过影响DIO小鼠能量代谢、肠屏障、核受体家族等相关mRNA和蛋白的表达水平，达到改善高脂条件下宿主体重过快增长、血脂升高、组织慢性炎症和肠屏障通透性的效果，且该药效无法在抗生素干扰组中得以观察。. 肠道菌群多样性研究发现，口服多糖可以丰富肠道菌群多样性，提高拟杆菌门/厚壁菌门的比值；环境因子关联分析证明，肠道优势菌属Akkermansia与脂代谢紊乱各参数密切相关。同时，粪菌移植8周后的OTU分析表明供、受体小鼠肠道菌群相似性接近90%；且属水平上，供、受体具有一致性。. 代谢组学研究发现，口服多糖可以回调因高脂饮食偏离正常的整体代谢趋势，影响丁酸、丙酸等参与能量代谢、氨基酸代谢和胆汁酸代谢通路的关键代谢产物的含量，从代谢组学的角度为阐述麦冬多糖改善脂质代谢紊乱的起效机制提供实验依据。. 基于宏基因组学研究，发现口服多糖可以极大地提高肠道菌群的多样性，Akkermansia菌属为优势菌属。LEfSe分析提示，Akkermansia muciniphila为DIO小鼠肠道内的优势菌种。代谢通路比较分析指出，麦冬多糖影响下的肠道菌群对宿主能量代谢、氨基酸代谢、脂肪酸合成、胆汁酸代谢有影响。. 综上，麦冬多糖可通过增加Akkermansia_muciniphila菌属诱导SCFAs产生改善能量代谢，抑制肝脏中脂肪生成和炎症基因的表达，同时可保护肠道屏障完整性，并阻止有害代谢物的流出缓解NAFLD的炎症发生。口服麦冬多糖可通过恢复肠道微生物群的平衡有效干预DIO小鼠的NAFLD进展。