基于“A.Muciniphila—胆汁酸—FXR/TGR5”研究云芝多糖改善NAFLD作用及其机制

Coriolus versicolor is a Chinese traditional medicinal fungus, its immunoregulation, liver protection, lipid-lowering and many other pharmacological actions have been reported in literature. Polysaccharide is the main active component of Coriolus versicolor, our group have already confirmed that Coriolus versicolor polysaccharide is potential prebiotics, which could regulate the intestinal flora of NAFLD model rats, particularly increase the abundance of metabolic diseases-related Akkermansia Muciniphila. According to these findings, we therefore propose a hypothesis that Coriolus versicolor polysaccharide improve NAFLD by regulating BAs receptor FXR/TGR5 and influencing lipid metabolism. To test this hypothesis, we will carry out the following research: (1) screen the Coriolus versicolor polysaccharide components improving NAFLD, and isolate them from Coriolus versicolor mycelium for structural analysis; (2) study on relationship between Coriolus versicolor polysaccharide efficacy and the variation of NAFLD model rats colonic intestinal flora; (3) study on A.Muciniphila regulating BAs receptor FXR/TGR5 to influence lipid metabolism and improve NAFLD by Coriolus versicolor polysaccharide efficacy. It is hoped to offer theoretical foundation for herbal polysaccharide improving NAFLD.

云芝是中国传统的药用真菌，云芝多糖是其主要生物活性物质，具有免疫调节、保肝、降血脂等多种药理作用。本课题组已经证实云芝多糖作为潜在益生元，可调节NAFLD模型大鼠肠道菌群的组成及比例，尤其使与代谢性疾病密切相关的细菌Akkermansia Muciniphila丰度显著提高。本项目假设云芝多糖通过A.Muciniphila调控BAs受体FXR/TGR5影响脂代谢，是改善NAFLD的重要的药效机制。本项目将进行以下研究: (1)从云芝发酵菌丝体中筛选获得具有改善NAFLD作用的云芝多糖，并对其分离纯化和结构解析; (2)研究NAFLD模型大鼠经云芝多糖灌胃后，结肠中微生物菌群及胆汁酸的组成及比例变化与云芝多糖药效作用的相关性; (3)研究云芝多糖通过A.Muciniphila调控BAs受体FXR/TGR5影响脂代谢发挥改善NAFLD的作用机制，为中药多糖在改善NAFLD的作用提供理论依据。

非酒精性脂肪肝病（Non-alcoholic fatty liver disease，NAFLD）是目前世界范围内最常见的慢性肝病，其发病机制尚未明确。随着代谢组学和基因测序的发展，通过“肠—肝轴”研究NAFLD成为一大热点。本课题从云芝发酵菌丝体中分离纯化出一种新的云芝多糖（YZ），糖苷键类型分析和核磁共振波谱表明云芝多糖中存在十种不同类型的糖苷键链接方式，主链由甘露糖和半乳糖组成，在甘露糖的C6和C4位分别存在两个分支结构。通过高脂饮食诱导的小鼠NAFLD模型，从肝脏形态、体重、肝脏指数、生化指标以及肝脏组织病理切片等方面评估YZ对NAFLD小鼠的治疗效果，结果表明YZ显著减少肝脏脂质积累，抑制肝脏脂肪变性，有效缓解NAFLD疾病症状。从体外细胞实验、肠道菌群的调控以及肝脏胆汁酸的调控三个方面初步研究云芝多糖治疗小鼠NAFLD的机制。实验结果表明，高剂量组小鼠的血清显著改善油酸钠诱导的L02细胞NAFLD模型的病理状况。高通量测序研究表明，云芝多糖调控NAFLD小鼠肠道菌群Firmicutes与Bacteroides丰度比值显著降低,增加与胆汁酸代谢相关菌群Bacteroides和Eubacterium coprostanoligenes group的丰度。靶向代谢组学分析小鼠肝脏胆汁酸谱，结果显示YZ组胆汁酸组成与Model组具有显著差异，存在7种差异代谢胆汁酸。综上所述，本论文基于“肠—肝轴”理论，初步研究了云芝多糖通过调控肠道菌群，影响胆汁酸代谢，从而发挥治疗NAFLD的作用，为云芝多糖治疗NAFLD提供理论基础，为NAFLD药物开发拓宽方向。