博士生会||文献共享-《Metabolic retroconversion of trimethylamine N-oxide and the gut microbiota》报道Anne L. McCartney and Marc

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文献共享第四十六期||《Metabolic retroconversion of trimethylamine N-oxide and the gut microbiota》报道Anne L. McCartney and Marc-Emmanuel Dumas课题组在肠道菌群研究领域中的新进展

肠道微生物群将膳食中的甲胺胆碱、肉碱、磷脂酰胆碱分解为一系列的代谢产物，包括三甲胺（TMA）。然而，这些联合微生物体是如何利用氧化三甲胺（TMAO）的，我们知之甚少。

利用氘化氧化三甲胺进行C57BL6/J小鼠喂养的实验表明，微生物可将氧化三甲胺转化为三甲胺，吸收入血的三甲胺又转化为氧化三甲胺。在抗生素治疗的小鼠中，将TMAO转化为TMA的微生物活性被抑制，导致氘化TMAO直接进入血液。在接种人粪便的分批培养发酵系统中，TMAO的存在刺激了肠道菌群的生长。在固体和液体培养基上对66株人源性粪便和盲肠细菌进行了TMAO筛选，利用¹HNMR分析了废旧培养基中的代谢产物。与体外发酵试验一样，TMAO对肠道杆菌科细菌的生长有促进作用，这些细菌产生的TMA大部分来自TMAO。与粪便中的其他细菌相比，从盲肠/小肠分离得到的大肠埃希菌可产生更多的TMA。在TMAO存在的条件下生长时，乳酸杆菌产生的乳酸的量增加，但不产生大量的TMA。混合发酵系统中，梭状芽孢杆菌、双歧杆菌和棒状菌与TMA的产量呈现显著正相关，但在纯培养条件下，TMAO不会产生大量的TMA。结论：肠道微生物（主要是肠道杆菌科）可将TMAO还原为TMA，TMA被宿主从肠道吸收进入血液，宿主肝酶又将其转化为TMAO，这是代谢逆转录的一个例子。TMAO对微生物代谢的影响取决于肠道细菌的分离来源和分类群。混合微生物群发酵系统的代谢组学和大量的数据相关性，没有给出肠道微生物群成员将TMAO转化为TMA的真实图片，只有通过补充纯培养和额外的代谢组学研究，我们才可能增加对人类肠道微生物群对TMAO生物转化的认识。

*Ln- prefix, different numbers indicate isolates recovered from different individuals

†DSMZ, Leibniz Institute DSMZ – German Collection of Microorganisms and Cell Cultures

Fig. 1 In vivo confirmation of metabolic retroconversion of TMAO. Reduction of d9 -TMAO to d9 -TMA was quantified by UPLC–MS/MS up to 6 h after d9 -TMAO gavage and antibiotic treatment, together with unlabelled TMA and TMAO levels. Plasma quantification of post-gavage a d9 -TMA and b d9 -TMAO. *Significantly (P<0.05; t test and corrected for multiple comparison using the Holm–Sidak method) different from the respective groups not treated with antibiotics. c d9 –TMA bioavailability (AUC). d d9 -TMAO bioavailability (AUC). Plasma quantification of post-gavage unlabelled/endogenous.e TMA and f TMAO. *Significant between d9 and d9 antibiotic treatment; $significant between TMAO and TMAO antibiotic treatment. g Unlabelled/endogenous TMA bioavailability (AUC). h Unlabelled/endogenous TMAO bioavailability (AUC). Data (n=6 per group) are shown as mean±SEM (a, b,e, f). Differences between the bioavailabilities (c, d, g, h) were assessed using one-way analysis of variance (ANOVA), followed by Holm–Sidak post hoc tests. Data with different superscript letters are significantly different (P<0.05).

Fig. 2 Effect of TMAO on mixed faecal microbial population in vitro. a Enumeration of selected bacteria in fermentation vessels by FISH analysis. Red lines, TMAO-containing systems; blue lines, negative controls. Data are shown as mean+SD (n=3). Eub338, total bacteria; Ent, Enterobacteriaceae; Bif164, Bifidobacterium spp.; Lab158, lactic acid bacteria. *Statistically significantly different (adjusted P<0.05) from the control at the same time point. Full data are shown in Additional file 1: Figure S1. b1H-NMR data for batch culture samples. Data are shown as mean±SD (n=3). Red lines, TMAO-containing systems; blue lines, negative controls. *Statistically significantly different (P<0.05) from the negative control at the same time point. c Bidirectional clustering of correlation matrix of FISH data and data for the six metabolites found in the highest amounts in the NMR spectra from the batch-culture samples.+ Adjusted P value (Benjamini–Hochberg) statistically significant (P<0.05). FISH and metabolite data and a table of correlations and adjusted P values (Benjamini–Hochberg) for the batch-culture samples are available in Additional file 1: Table S3–S5.

Fig. 3 Influence of TMAO on growth and metabolism of pure cultures of gut bacteria. a Representative growth curves for isolates grown in the presence and absence of TMAO. Red lines, TMAO-supplemented cultures; blue lines, negative controls. Data are shown as mean±SD (n=3). b Biplot showing production of various metabolites when isolates were grown in the presence of TMAO. Summary of data from Additional file 1: Table S2. The larger a circle, the more of the metabolite produced by an isolate. c Differences in metabolites produced when caecal and faecal isolates of Escherichia coli were grown in the presence (+) and absence (−) of 1% TMAO. Adjusted (Benjamini–Hochberg) P values indicate the caecal isolates were significantly different from the faecal isolates for a particular metabolite. d Lactate production by lactic acid bacteria was increased in the presence of TMAO. Enterobacteriaceae, n=20; Bifidobacteriaceae, n=17; Streptococcaceae, n=7; Enterococcaceae, n=5. Members of the Enterococcaceae and Streptococcaceae are homofermenters (produce only lactic acid from glucose fermentation), whereas the Bifidobacteriaceae are heterofermenters (produce ethanol, CO 2 , and lactic acid from glucose fermentation), though it should be noted the bifidobacteria included in this study were grown on raffinose-containing media. Red, TMAO-containing medium; blue, negative control. *Statistically significantly different from its negative control (adjusted P value <0.05)

参考文献 

链接：https://doi.org/10.1186/s40168-018-0461-0

Hoyles L , Jiménez-Pranteda, Maria L, Chilloux J , et al. Metabolic retroconversion of trimethylamine N-oxide and the gut microbiota[J]. Microbiome, 2018, 6(1):73.