肠道罗尔斯顿菌（Ralstonia）与非酒精性脂肪肝（NAFLD）因果关系及患病风险研究

Identifying key species from the complex gut microbiota and studying its function is a major task in the microbiome research field. Recently, our group completed Guangdong Gut Microbiome Project, which surveyed around eight thousand subjects using random sampling, and identified that gut Ralstonia was highly correlated with non-alcoholic fatty liver disease (NAFLD). Ralstonia is rarely detected in Western populations, so its research is highly limited. We hypothesize that: Ralstonia in human gut microbiota can causally aggravate host NAFLD and therefore can increase disease risk. In the present study, we ought to examine the cause-effect relationship between gut Ralstonia and host NAFLD in germ-free mice. Chronic inflammation, FIAF, ethanol and TMA pathways will be examined to explore mechanisms. Meanwhile, a follow-up study will be conducted to examine if individuals with higher Ralstonia would have significantly higher risk of developing NAFLD compared to those with lower Ralstonia in their gut. This study aims to identify a unique gut bacterial species that promotes host NAFLD in the local population, therefore offers a new target in the prognosis and treatment of NAFLD.

从复杂的肠道菌群中识别关键菌，鉴定其功能，是人体微生物组研究的重要内容。课题组近期开展广东省肠道菌群与慢性病调查，通过随机分层抽样八千余社区人群，发现Ralstonia是NAFLD显著相关菌属之一，高低Ralstonia两组人群NAFLD患病率相差十倍。Ralstonia在广东省人群肠道普遍存在，但在西方人群检出率低，相关研究少。假设：肠道Ralstonia与NAFLD存在因果关系，是本地人群NAFLD重要风险因子。本课题拟通过无菌鼠定植实验，验证Ralstonia与NAFLD的因果关系；检测慢性炎症、断食诱导脂肪因子、乙醇、三甲胺等通路，探索其潜在作用途径；在前期人群横断面调查基础上，建立随访队列，比较罗尔斯顿菌高低两组五年NAFLD新发率，探明其相对危险度。本研究有望阐明罗尔斯顿菌是否为一类独特的促进本地人群NAFLD的关键菌，为NAFLD风险评价及预防干预提供新靶点。

肠道菌群与宿主的健康密切相关，从中挖掘新的标志物，阐明其作用机制，量化其风险评估价值，是菌群标志物研究的重要途径。本项目基于前期大数据分析所发现的Ralstonia和脂肪肝的关系，开展深入和相关的研究。（1）给与小鼠灌胃Ralstonia，并未发现其导致小鼠代谢功能紊乱，但发现Ralstonia和Fusobacterium可能存在协同作用，当同时灌胃两种细菌时，Fusobacterium可破坏屏障，进而Ralstonia表现出对宿主代谢的影响，说明Ralstonia可能对宿主代谢能够起作用，但需要其他细菌的协同作用；（2）建立了基于16S rRNA基因的Fusobacterium亚群分类方法，阐明华南地区人群Fusobacterium的分布特征，说明在该人群重，除了具核梭杆菌，其他如坏死梭杆菌、变异梭杆菌、溃疡梭杆菌等均值得关注；（3）代谢紊乱的关键终点事件是卒中，我们进而研究卒中与肠道菌群之间的关系，首先发现卒中患者存在肠道菌群紊乱-恢复的动态轨迹，其中以肠杆菌为主要变化特征。进而发现卒中伴发肠道菌群再灌注，产生大量氧自由基与过氧亚硝基，进而产生硝酸盐，而硝酸盐呼吸导致肠道中肠杆菌富集，而肠杆菌反过来通过LPS-TLR4途径激活系统性炎症，加重脑损伤。在课题的资助下，申请人发表SCI论文两篇（Gut 2020，2021），并获得国家自然科学基金优秀青年基金资助。