Trimethylamine (TMA) is a tertiary amine with a characteristic fishy odour. It is synthesised from dietary constituents, including choline, L-carnitine, betaine and lecithin by the action of microbial enzymes during both healthy and diseased conditions in humans. Trimethylaminuria (TMAU) is a disease typified by its association with the characteristic fishy odour because of decreased TMA metabolism and excessive TMA excretion. Besides TMAU, a number of other diseases are associated with abnormal levels of TMA, including renal disorders, cancer, obesity, diabetes, cardiovascular diseases and neuropsychiatric disorders. Aside from its role in pathobiology, TMA is a precursor of trimethylamine-N-oxide that has been associated with an increased risk of athero-thrombogenesis. Additionally, TMA is a major air pollutant originating from vehicular exhaust, food waste and animal husbandry industry. The adverse effects of TMA need to be monitored given its ubiquitous presence in air and easy absorption through human skin. In this review, we highlight multifaceted attributes of TMA with an emphasis on its physiological, pathological and environmental impacts. We propose a clinical surveillance of human TMA levels that can fully assess its role as a potential marker of microbial dysbiosis-based diseases.

中文翻译：

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三甲胺在人体中的复杂代谢：内源性和外源性来源

三甲胺 (TMA) 是一种具有特殊鱼腥味的叔胺。它是由膳食成分合成的，包括胆碱、左旋肉碱、甜菜碱和卵磷脂，通过微生物酶在人类健康和疾病条件下的作用。三甲基氨基尿症 (TMAU) 是一种典型的疾病，其特征是由于 TMA 代谢降低和 TMA 排泄过多而与特征性鱼腥味有关。除 TMAU 外，许多其他疾病与 TMA 水平异常有关，包括肾脏疾病、癌症、肥胖症、糖尿病、心血管疾病和神经精神疾病。除了在病理生物学中的作用外，TMA 还是三甲胺-N-氧化物的前体，与动脉粥样硬化血栓形成的风险增加有关。此外，TMA 是源自汽车尾气的主要空气污染物，食物垃圾和畜牧业。鉴于 TMA 在空气中无处不在且易于通过人体皮肤吸收，因此需要监测其不利影响。在这篇综述中，我们强调了 TMA 的多方面属性，重点是其生理、病理和环境影响。我们建议对人类 TMA 水平进行临床监测，以充分评估其作为基于微生物失调疾病的潜在标志物的作用。