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    基于“肠道菌群-胆汁酸”轴探讨木香烃内酯治疗溃疡性结肠炎的作用机制

    Mechanism Investigation of Costunolide in Treating Ulcerative Colitis via the Gut Microbiota-Bile Acid Axis

      摘要
    • 摘要:
      目的  探讨木香烃内酯(costunolide，COS)调控“肠道菌群-胆汁酸”轴稳态，抑制胆汁酸合成限速酶表达，从而缓解溃疡性结肠炎(ulcerative colitis，UC)的作用机制。
      方法 采用3%葡聚糖硫酸钠(DSS)诱导C57BL/6J小鼠建立UC模型，随机分为空白组、模型组、COS低剂量组(10 mg·kg−1)和高剂量组(20 mg·kg−1)。评估疾病活动指数(disease activity index，DAI)、结肠长度及组织病理变化；16S rDNA测序分析肠道菌群组成，LC-MS检测粪便胆汁酸谱，RT-qPCR和Western blotting检测肝脏及结肠组织中FXR、TGR5及其下游信号分子(FGF15、SHP、CYP7A1、CYP27A1)的mRNA和蛋白表达。
      结果 COS干预显著逆转UC小鼠体质量下降、结肠缩短，其可降低DAI评分并减轻组织病理损伤(P<0.05或P<0.01或P<0.001)，改善DSS引起的胆汁酸代谢紊乱：降低初级胆汁酸(CA、CDCA、TCDCA)水平，提高次级胆汁酸(DCA、LCA、TUDCA)含量(P<0.05)，同时恢复肠道菌群多样性及丰富度。Western blotting与RT-qPCR结果显示，COS可调节胆汁酸合成相关分子的表达，尤以COS高剂量组作用较为显著，TGR5、FGF15和SHP mRNA表达显著升高(P<0.05或P<0.01或P<0.001)，CYP7A1、CYP27A1 mRNA表达显著降低(P<0.001)，此外TGR5 蛋白显著上调(P<0.01)，CYP7A1、CYP27A1 蛋白显著下调(P<0.05)。
      结论 COS可通过重塑肠道菌群结构、改善胆汁酸代谢紊乱，并抑制胆汁酸合成限速酶的表达，从而缓解UC症状。

       

      Abstract:
      OBJECTIVE To investigate the mechanism by which costunolide(COS) alleviates ulcerative colitis(UC) through regulating the homeostasis of the “gut microbiota-bile acid” axis and inhibiting the expression of rate-limiting enzymes in bile acid synthesis.
      METHODS UC model was established in C57BL/6J mice using 3% dextran sulfate sodium. The mice were randomly divided into four groups: control(CON), model(MOD), low-dose COS(10 mg·kg−1, COS.L), and high-dose COS(20 mg·kg−1, COS.H). Disease activity index(DAI), colon length, and histopathological changes were assessed. Gut microbiota composition was analyzed by 16S rDNA sequencing; fecal bile acid profiles were determined using LC-MS; and mRNA and protein expression of FXR, TGR5, and their downstream signaling molecules(FGF15, SHP, CYP7A1, CYP27A1) in liver and colon tissues were measured via RT-qPCR and Western blotting.
      RESULTS COS intervention significantly reversed body weight loss, colon shortening, reduced DAI scores, and alleviated histopathological damage in UC mice(P<0.05 or P<0.01 or P<0.001). It also improved DSS-induced bile acid metabolic disorders by decreasing levels of primary bile acids(CA, CDCA, TCDCA) and increasing secondary bile acids(DCA, LCA, TUDCA)(P<0.05), while restoring gut microbiota diversity and richness. Western blotting and RT-qPCR results showed that COS regulated the expression of bile acid synthesis-related molecules, with more pronounced effects in the COS.H group. Specifically, TGR5, FGF15, and SHP mRNA levels were significantly increased (P<0.05 or P<0.01 or P<0.001), whereas CYP7A1 and CYP27A1 mRNA levels were significantly decreased (P<0.001). In addition, TGR5 protein expression was significantly upregulated (P<0.01), while CYP7A1 and CYP27A1 protein expression was significantly downregulated (P<0.05).
      CONCLUSION COS alleviates UC colitis by reshaping gut microbiota structure, improving bile acid metabolic disorders, and inhibiting the expression of rate-limiting enzymes in bile acid synthesis.

       

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