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

关键词:  木香烃内酯  溃疡性结肠炎  胆汁酸  肠道菌群  

Key words:  Costunolide  Ulcerative colitis  Bile acids  Gut microbiota  

摘要:

目的 探讨木香烃内酯（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（UC）的作用机制。方法 采用3% DSS诱导C57BL/6J小鼠建立UC模型，随机分为空白对照组（CON）、模型组（MOD）、木香烃内酯低剂量组（10 mg/kg, COS.L）和高剂量组（20 mg/kg, COS.H）。评估疾病活动指数（DAI）、结肠长度及组织病理变化；16S rDNA测序分析肠道菌群组成，GC-MS检测粪便胆汁酸谱，RT-qPCR和Western blot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小鼠体重下降、结肠缩短，降低DAI评分并减轻组织病理损伤（P<0.05），改善DSS引起的胆汁酸代谢紊乱：降低初级胆汁酸（CA、CDCA、UDCA）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 blot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.H作用较为显著， mRNA显著上调，CYP7A1、CYP27A1 mRNA显著下调，此外TGR5、FGF15和SHP蛋白表达显著升高（P<0.05），CYP7A1、CYP27A1蛋白表达显著降低（P<0.05）。结论 木香烃内酯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，从而缓解溃疡性结肠炎。

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% DSS. The mice were randomly divided into four groups: control (CON), model (MOD), low-dose COS (10 mg/kg, COS.L), and high-dose COS (20 mg/kg, 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 GC-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 blot. RESULTS COS intervention significantly reversed body weight loss, colon shortening, reduced DAI scores, and alleviated histopathological damage in UC mice (P<0.05). It also improved DSS-induced bile acid metabolic disorders by decreasing levels of primary bile acids (CA, CDCA, UDCA) and increasing secondary bile acids (DCA, LCA, TUDCA) (P<0.05), while restoring gut microbiota diversity and richness. Western blot 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 mRNA was significantly upregulated, whereas CYP7A1 and CYP27A1 mRNA were downregulated. Additionally, protein expression of TGR5, FGF15, and SHP was markedly increased (P<0.05), while CYP7A1 and CYP27A1 protein expression was significantly decreased (P<0.05). CONCLUSION Costunolide alleviates ulcerative colitis by reshaping gut microbiota structure, improving bile acid metabolic disorders, and inhibiting the expression of rate-limiting enzymes in bile acid synthesis