肠道胆汁酸代谢失衡在氟喹诺酮类药物致血糖紊乱中的作用及机制

A variety of fluoroquinolone agents have been reported to cause dysglycemia. Intestinal bile acids act as signaling molecules via G protein-coupled receptor TGR5 and the nuclear receptor FXR to stimulate or inhibit glucagon-like peptide 1(GLP-1) secretion and regulate glucose homeostasis. Different bile acids exert different effects on TGR5 and FXR. Fluoroquinolone agents are antibacterial drug which may also affect the function and expression of some transporters in intestinal tract. Our previous studies proved the stimulation effect of fluoroquinolone agents on GLP-1 secretion and showed that TGR5 pathway was involved, which indicated that disturbance of intestinal bile acids metabolism be one of the important mechanisms of fluoroquinolone-induced dysglycemia. Ciprofloxacin is served as a representative drug in this research. The effect of ciprofloxacin-induced changes of intestinal bile acids composition on GLP-1 secretion and the relation with TGR5 and FXR will be investigated. Gut microbiota and enterohepatic circulation of bile acids are two main mechanisms for changes of intestinal bile acids composition. Therefore the relation between ciprofloxacin-induced changes of gut microbiota and intestinal bile acid pool will be further studied. Besides, bile acids absorption and bile excretion will also be investigated to explore the effect of ciprofloxacin on enterohepatic circulation of bile acids. Our findings have important implications for understanding the mechanism of fluoroquinolones-induced dysglycemia, as well as providing guidance for rational use of fluoroquinolones and prediction of drug adverse effects.

氟喹诺酮类药物临床使用往往伴随血糖紊乱不良反应。肠道胆汁酸分别通过G蛋白偶联受体(TGR5)或法尼醇X受体(FXR)促进或抑制胰高血糖素样肽-1(GLP-1)释放，不同胆汁酸成分对TGR5和FXR作用是不同的。氟喹诺酮药物属于抗菌药，同时影响一些肠道转运体功能。前期研究显示氟喹诺酮药物也影响GLP-1分泌，该过程与TGR5有关，提示肠道胆汁酸代谢紊乱可能是氟喹诺酮药物诱发血糖紊乱主要原因之一。本项目以环丙沙星为代表，从在体和细胞两个层面研究环丙沙星引起肠道胆汁酸组成改变及其对GLP-1分泌的影响，以及与TGR5和FXR的关系。围绕影响肠道胆汁酸组成的关键因素，肠道菌群和胆汁酸肠肝循环，分析环丙沙星干预后肠道菌群分布与肠道胆汁酸谱改变的相关性以及环丙沙星对肠道胆汁酸吸收和胆汁酸胆汁排泄影响。其研究成果有助于揭示氟喹诺酮药物引起血糖紊乱机制，对该类药物临床合理使用和不良反应预测具有重要意义。

抗菌药物的使用会引起一定程度的胆汁酸谱改变。在本项目中，重点研究了两种典型的氟喹诺酮类抗菌药物环丙沙星和莫西沙星对胆汁酸代谢谱的改变，并比较两者的差异。我们发现，环丙沙星和莫西沙星干预后血清及胆汁中总胆汁酸浓度降低，肠道总胆汁酸增加，同时分析发现环丙沙星较莫西沙星显著增加牛磺酸结合型胆汁酸，并显著减少次级胆汁酸。本研究采用胆汁酸疏水性指数评价胆汁酸代谢谱的整体改变，发现环丙沙星能够显著降低大鼠体内胆汁酸疏水指数，而莫西沙星对胆汁酸疏水性指数影响不明显。由于环丙沙星和莫西沙星具有不同的抗菌谱，其对肠道菌群的作用也不尽相同，环丙沙星显著增加Firmicutes，抑制Bacteroidetes，而莫西沙星对Firmicutes和Bacteroidetes均有所抑制，环丙沙星和莫西沙星对肠道菌群的不同的作用可能是其对胆汁酸代谢谱产生不同影响的原因之一。氟喹诺酮药物会引起一定程度的血糖波动，本研究发现环丙沙星对正常大鼠血糖及GLP-1影响并不明显，而莫西沙星能够显著升高正常大鼠空腹血糖并减少GLP-1的分泌。Western blot实验发现环丙沙星对正常大鼠肠道TGR5表达及FXR表达没有明显影响，莫西沙星给药组大鼠肠道TGR5表达显著下调，FXR表达显著上调，可见，环丙沙星与莫西沙星对FXR和TGR5受体表达的不同调控作用可能是两者对血糖调控作用不同的原因之一。进一步在离体细胞水平上考察药物引起胆汁酸改变与血糖波动的相关性，发现随着TCA/LCA比值的升高GLP-1分泌增加，但TCDCA/LCA比值增加GLP-1分泌受抑，由此可见，不同肠道胆汁酸组成对GLP-1分泌的影响不同。本研究成果有助于阐明氟喹诺酮药物对胆汁酸代谢的影响，胆汁酸代谢谱改变以及相关调控蛋白改变与该类药物引起血糖波动有一定的相关性，研究结果能够为临床上感染患者使用氟喹诺酮类抗菌药时选择合适药物提供理论依据。