采用体外批量发酵（人体结肠）模型研究人体肠道微生物群从胆碱、左旋肉碱和相关前体产生 TMA 的机制。
The use of an in-vitro batch fermentation (human colon) model for investigating mechanisms of TMA production from choline, L-carnitine and related precursors by the human gut microbiota.
机构信息
Quadram Institute Bioscience, Norwich Research Park, Norwich, NR4 7UQ, UK.
Chemistry of Flavour and Aroma Dept, National Research Centre, 33 El Buhouth St, Giza, 12622, Dokki, Egypt.
出版信息
Eur J Nutr. 2021 Oct;60(7):3987-3999. doi: 10.1007/s00394-021-02572-6. Epub 2021 May 2.
PURPOSE
Plasma trimethylamine-N-oxide (TMAO) levels have been shown to correlate with increased risk of metabolic diseases including cardiovascular diseases. TMAO exposure predominantly occurs as a consequence of gut microbiota-dependent trimethylamine (TMA) production from dietary substrates including choline, carnitine and betaine, which is then converted to TMAO in the liver. Reducing microbial TMA production is likely to be the most effective and sustainable approach to overcoming TMAO burden in humans. Current models for studying microbial TMA production have numerous weaknesses including the cost and length of human studies, differences in TMA(O) metabolism in animal models and the risk of failing to replicate multi-enzyme/multi-strain pathways when using isolated bacterial strains. The purpose of this research was to investigate TMA production from dietary precursors in an in-vitro model of the human colon.
METHODS
TMA production from choline, L-carnitine, betaine and γ-butyrobetaine was studied over 24-48 h using an in-vitro human colon model with metabolite quantification performed using LC-MS.
RESULTS
Choline was metabolised via the direct choline TMA-lyase route but not the indirect choline-betaine-TMA route, conversion of L-carnitine to TMA was slower than that of choline and involves the formation of the intermediate γ-BB, whereas the Rieske-type monooxygenase/reductase pathway for L-carnitine metabolism to TMA was negligible. The rate of TMA production from precursors was choline > carnitine > betaine > γ-BB. 3,3-Dimethyl-1-butanol (DMB) had no effect on the conversion of choline to TMA.
CONCLUSION
The metabolic routes for microbial TMA production in the colon model are consistent with observations from human studies. Thus, this model is suitable for studying gut microbiota metabolism of TMA and for screening potential therapeutic targets that aim to attenuate TMA production by the gut microbiota.
TRIAL REGISTRATION NUMBER
NCT02653001 ( http://www.clinicaltrials.gov ), registered 12 Jan 2016.
目的
已有研究表明，血浆三甲胺氧化物（TMAO）水平与包括心血管疾病在内的代谢性疾病的风险增加相关。TMAO 的暴露主要是由于肠道微生物群依赖于饮食底物（包括胆碱、肉碱和甜菜碱）产生三甲胺（TMA），然后在肝脏中转化为 TMAO。减少微生物 TMA 的产生可能是克服人类 TMAO 负担最有效和可持续的方法。目前用于研究微生物 TMA 产生的模型存在许多缺陷，包括人体研究的成本和长度、动物模型中 TMA（O）代谢的差异，以及使用分离的细菌菌株时未能复制多酶/多株途径的风险。本研究的目的是在人类结肠的体外模型中研究膳食前体物产生 TMA 的情况。
方法
使用体外人结肠模型，在 24-48 小时内研究胆碱、L-肉碱、甜菜碱和γ-丁基甜菜碱产生 TMA 的情况，并使用 LC-MS 进行代谢产物定量。
结果
胆碱通过直接胆碱 TMA 裂解酶途径代谢，但不是间接胆碱-甜菜碱-TMA 途径，L-肉碱转化为 TMA 的速度比胆碱慢，涉及中间体γ-BB 的形成，而 L-肉碱代谢为 TMA 的 Rieske 型单加氧酶/还原酶途径可以忽略不计。前体物产生 TMA 的速率为胆碱>肉碱>甜菜碱>γ-BB。3,3-二甲基-1-丁醇（DMB）对胆碱转化为 TMA 没有影响。
结论
结肠模型中微生物 TMA 产生的代谢途径与人体研究的观察结果一致。因此，该模型适合研究肠道微生物群对 TMA 的代谢，并筛选旨在减轻肠道微生物群 TMA 产生的潜在治疗靶点。
试验注册号
NCT02653001（http://www.clinicaltrials.gov），于 2016 年 1 月 12 日注册。
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