The role of bile acid metabolism recovery in treatment of C. difficile infection

描述(由申请人提供)：在过去的二十年里，艰难梭菌感染(CDI)已经达到流行的程度，这是因为出现了更强毒力的病原体菌株。粪便微生物移植(FMT)已成为许多单用抗生素治疗无效的患者的潜在解决方案。我们和其他人之前已经证明，FMT迅速恢复了与捐赠者相似的正常粪便细菌组成。我们还表明，正常微生物肠道生态的恢复伴随着粪便代谢组的重大变化，其中重要的包括粪便胆汁酸组成的正常化。对胆汁酸的关注在机制上是相关的，因为它们在艰难梭菌的生命周期中扮演着重要的角色。具体地说，牛磺胆酸盐(一种主要的胆汁酸)是一种 艰难梭菌孢子的有效发芽剂，也是艰难梭菌实验室生长介质的关键成分。相反，石胆酸盐和脱氧胆酸(主要的次生胆汁酸)分别是艰难梭菌孢子萌发和营养生长的抑制物。我们发现，RCDI患者在FMT前的粪便样本中不含有可检测到的次级胆汁酸，但确实有升高的初级胆汁酸浓度。FMT后取自同一患者的粪便样本含有类似捐赠者的粪便胆汁酸成分。因此，我们的中心假设是，用于治疗CDI患者的抗生素改变了胆汁酸代谢，有利于艰难梭菌的萌发和生长，而FMT恢复了不利于艰难梭菌扩张的正常胆汁酸组成。在这项提案中，我们将延长我们的探索性初步 结果通过定量分析FMT前后RCDI患者的胆汁酸代谢，以及检测FMT前后粪便样本对艰难梭菌临床分离株的萌发活性和生长抑制，对这一假说进行了验证。此外，我们将测试一种非FMT方法来改变不利于艰难梭菌的胆汁酸组成：胆汁酸隔离树脂，胆碱胺，与洛伐他汀联合使用。后者将被用来抑制肝脏胆汁酸合成的代偿性增加。这项工作的结果将为未来通过靶向胆汁酸代谢治疗难治性CDI患者的临床试验提供参考。

DESCRIPTION (provided by applicant): Over the past two decades Clostridium difficile infection (CDI) has reached epidemic proportions due to emergence of more virulent strains of the pathogen. Fecal microbiota transplantation (FMT) has emerged as a potential solution for many patients refractory to antibiotic treatment alone. We and others have previously shown that FMT promptly restores normal fecal bacterial composition similar to that of the donors. We had also shown that recovery of normal microbial gut ecology is accompanied by major changes in the fecal metabolome, which importantly includes normalization of fecal bile acid composition. The focus on bile acids is mechanistically relevant because they are known to play important roles in the lifecycle of C. difficile. Specifically, taurocholate (a major primary bile acid) is a potent germinant of C. difficile spores, and a critical component of C. difficile growth media in the laboratory. In contrast, lithocholate and deoxycholate (dominant secondary bile acids) are inhibitors of C. difficile spore germination and vegetative growth, respectively. We found that fecal samples from RCDI patients before FMT contain no detectable secondary bile acids, but do have elevated concentrations of primary bile acids. Fecal samples taken from the same patients after FMT contain donor-like fecal bile acid composition. Therefore, our central hypothesis is that antibiotics used to treat CDI patients alter bile acid metabolism to favor C. difficile germination and growth, and FMT restores the normal bile acid composition that is inhospitable to C. difficile expansion. In this proposal we will extend our exploratory preliminary results and test this hypothesis by performing quantitative analysis of bile acid metabolism in patients with RCDI pre- and post-FMT and testing pre- and post-FMT fecal samples for germinant activity and growth inhibition on clinical isolates of C. difficile bacteria. In additionwe will test one non-FMT approach to alter bile acid composition unfavorable to C. difficile: a bile acid sequestrant resin, cholestyramine, in combination with lovastatin. The latter will be used to inhibit compensatory increase in de novo bile acid synthesis in the liver. Results of this work wil inform future clinical trials in treating patients with refractory CDI by targeting bile acid metabolism.