A metabolic pathway for bile acid dehydroxylation by the gut microbiome
A metabolic pathway for bile acid dehydroxylation by the gut microbiome
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肠道微生物组胆汁酸脱羟基的代谢途径
DOI：
10.1038/s41586-020-2396-4
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发表时间：
2020-06-17
期刊：
影响因子：
64.8
通讯作者：
Fischbach, Michael A.
中科院分区：
文献类型：
--
作者：
Funabashi, Masanori;Grove, Tyler L.;Fischbach, Michael A.
在人类肠道微生物中产生二级胆汁酸DCA和LCA的生物合成途径已被充分表征，被工程化到另一种细菌宿主中，并用于赋予无菌小鼠中的DCA生产-肠道微生物途径工程的重要原理证明。其中最丰富的代谢物是次级胆汁酸脱氧胆酸（DCA）和石胆酸（LCA），其积累浓度约为500 μ M，已知可阻断艰难梭菌的生长（1），促进肝细胞癌（2），并通过G蛋白偶联受体TGR 5调节宿主代谢（参考文献5）。（三））。更广泛地说，DCA、LCA及其衍生物是胆汁酸再循环池的主要成分（4）;该池的大小和组成是原发性胆汁性胆管炎和非酒精性脂肪性肝炎治疗的靶点。尽管如此，尽管DCA和LCA对宿主生理学有明显的影响，但对其生物合成基因的不完全了解以及缺乏能够修饰其天然微生物生产者的遗传工具限制了我们调节宿主中次级胆汁酸水平的能力。在这里，我们完成了DCA和LCA的途径，通过分配和表征酶的还原臂中的每个步骤，揭示了一种策略，其中类固醇核心的A-B环被瞬时转化为电子受体的两个还原步骤进行的Fe-S flavoenzymes。使用厌氧体外重建，我们建立了一套六个酶是必要的，足够的八步转化胆酸DCA。然后，我们将该途径工程化到生孢梭菌中，在非生产性微生物上生产DCA和LCA，并证明微生物组衍生的途径可以异源表达和控制。这些数据建立了一个完整的途径，两个核心组成部分的胆汁酸池。
The biosynthetic pathway that produces the secondary bile acids DCA and LCA in human gut microbes has been fully characterized, engineered into another bacterial host, and used to confer DCA production in germ-free mice-an important proof-of-principle for the engineering of gut microbial pathways.The gut microbiota synthesize hundreds of molecules, many of which influence host physiology. Among the most abundant metabolites are the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA), which accumulate at concentrations of around 500 mu M and are known to block the growth ofClostridium difficile(1), promote hepatocellular carcinoma(2)and modulate host metabolism via the G-protein-coupled receptor TGR5 (ref.(3)). More broadly, DCA, LCA and their derivatives are major components of the recirculating pool of bile acids(4); the size and composition of this pool are a target of therapies for primary biliary cholangitis and nonalcoholic steatohepatitis. Nonetheless, despite the clear impact of DCA and LCA on host physiology, an incomplete knowledge of their biosynthetic genes and a lack of genetic tools to enable modification of their native microbial producers limit our ability to modulate secondary bile acid levels in the host. Here we complete the pathway to DCA and LCA by assigning and characterizing enzymes for each of the steps in its reductive arm, revealing a strategy in which the A-B rings of the steroid core are transiently converted into an electron acceptor for two reductive steps carried out by Fe-S flavoenzymes. Using anaerobic in vitro reconstitution, we establish that a set of six enzymes is necessary and sufficient for the eight-step conversion of cholic acid to DCA. We then engineer the pathway intoClostridium sporogenes, conferring production of DCA and LCA on a nonproducing commensal and demonstrating that a microbiome-derived pathway can be expressed and controlled heterologously. These data establish a complete pathway to two central components of the bile acid pool.