脱氧胆酸介导的肠道菌群失衡和胆汁酸代谢异常促进肠炎发生发展的机制研究

Mechanism study on genesis and development of enteritis induced by deoxycholic acid-mediating dysbosis of intestinal microbiota and bile acid abnormal metabolism

目的观察并分析脱氧胆酸在诱导小鼠肠炎过程中对肠道菌群及胆汁酸代谢的影响。方法将20只C57BL/6J小鼠随机均分为脱氧胆酸组和对照组,脱氧胆酸组小鼠给予含0.2%脱氧胆酸饲料,对照组给予常规饲料,连续喂养24周。采用HE染色观察肠道组织炎症程度并作评分,采用焦磷酸测序法分析肠道菌群变化,超高效液相色谱-串联质谱联用技术(HPLC-MS)定量分析小鼠粪便中各级胆汁酸的含量,实时荧光定量PCR检测胆汁酸相关基因的转录情况。结果脱氧胆酸组回肠末端和结肠病理组织学炎症评分显著高于对照组(均P<0.05)。与对照组相比,脱氧胆酸组粪便菌群多样性明显降低,厚壁菌门比例下降,梭菌属ⅩⅠⅤa比例显著下降(均P<0.05)。脱氧胆酸组小鼠粪便中总胆汁酸、次级胆汁酸、非结合胆汁酸、牛磺-α-鼠胆酸浓度显著高于对照组(均P<0.05)。与对照组相比,脱氧胆酸组胆汁酸转运基因有机溶质转运蛋白β(Ost-β)、胆汁酸信号分子法尼醇受体(FXR)、成纤维细胞生长因子15(FGF15)表达均明显减少(均P<0.05),而肝脏胆汁酸合成限速酶基因Cyp7a1、Cyp7b1和Cyp27a1表达明显增加(均P<0.05)。结论脱氧胆酸能诱导小鼠肠炎发生发展,可能与其破坏肠道菌群平衡以及通过FXR-FGF15信号通路促进肝脏胆汁酸合成有关。

Objective To observe and analyze the influence of deoxycholic acid(DCA)on intestinal microbiota and bile acid metabolism during the process of enteritis induced by DCA in mice.Methods Twenty C57BL/6J mice were randomly and equally divided into DCA group and control group.The mice in DCA group were developed by feeding the feed with 0.2%DCA and the mice in control group were developed with routine feed for 24 weeks.The degree of intestinal tissue inflammation was evaluated by HE staining and scored,the change of intestinal microbiota was analyzed by pyrosequencing,bile acid levels of all grades in faeces were detected by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS),the expressions of bile acid-related genes were detected by quantitive real-time PCR.Results The intestinal histology scores in DCA group was significantly higher than that of the control group(both P<0.05).The diversity of fecal microbiota in the DCA group was significantly reduced,the percentage of Firmicutes at the phylum level and the percentage of Clostridium XIVa at the genus level were significantly decreased(both P<0.05).The total bile acid,secondary bile acid,unconjugated bile acid and tauro-α-muricholic acid(T-α-MCA)of mice faeces in DCA group were significant higher than those in control group(all P<0.05).The expression of biliary acid transporter gene organic solute transporterβ(Ost-β),farnesoid X receptor(FXR)and fibroblast growth factor 15(FGF15)in DCA group decreased significantly(all P<0.05),while the expressions of liver bile synthesis rate-limiting enzymes Cyp7a1,Cyp7b1 and Cyp27a1 increased obviously(all P<0.05).Conclusions DCA can induce the progress of enteritis,which may be related to its destruction of intestinal microbiota in mice and the promotion of liver bile acid synthesis through FXR-FGF15 signaling pathway.