National Food Institute, Technical University of Denmark, Kgs. Lyngby, Denmark.
Department of Environmental Science, Aarhus University, Roskilde, Denmark.
Environ Pollut. 2018 Feb;233:364-376. doi: 10.1016/j.envpol.2017.10.016. Epub 2017 Nov 5.
Recently, concerns have been raised that residues of glyphosate-based herbicides may interfere with the homeostasis of the intestinal bacterial community and thereby affect the health of humans or animals. The biochemical pathway for aromatic amino acid synthesis (Shikimate pathway), which is specifically inhibited by glyphosate, is shared by plants and numerous bacterial species. Several in vitro studies have shown that various groups of intestinal bacteria may be differently affected by glyphosate. Here, we present results from an animal exposure trial combining deep 16S rRNA gene sequencing of the bacterial community with liquid chromatography mass spectrometry (LC-MS) based metabolic profiling of aromatic amino acids and their downstream metabolites. We found that glyphosate as well as the commercial formulation Glyfonova450 PLUS administered at up to fifty times the established European Acceptable Daily Intake (ADI = 0.5 mg/kg body weight) had very limited effects on bacterial community composition in Sprague Dawley rats during a two-week exposure trial. The effect of glyphosate on prototrophic bacterial growth was highly dependent on the availability of aromatic amino acids, suggesting that the observed limited effect on bacterial composition was due to the presence of sufficient amounts of aromatic amino acids in the intestinal environment. A strong correlation was observed between intestinal concentrations of glyphosate and intestinal pH, which may partly be explained by an observed reduction in acetic acid produced by the gut bacteria. We conclude that sufficient intestinal levels of aromatic amino acids provided by the diet alleviates the need for bacterial synthesis of aromatic amino acids and thus prevents an antimicrobial effect of glyphosate in vivo. It is however possible that the situation is different in cases of human malnutrition or in production animals.
最近，人们担心草甘膦类除草剂的残留可能会干扰肠道细菌群落的内稳态，从而影响人类或动物的健康。草甘膦特异性抑制的芳香族氨基酸合成的生化途径（莽草酸途径）与植物和许多细菌物种共享。几项体外研究表明，各种肠道细菌群体可能受到草甘膦的不同影响。在这里，我们结合细菌群落的深度 16S rRNA 基因测序和基于液相色谱-质谱（LC-MS）的芳香族氨基酸及其下游代谢物的代谢谱分析，展示了一项动物暴露试验的结果。我们发现，草甘膦以及以欧洲可接受日摄入量（ADI=0.5mg/kg 体重）的 50 倍给药的商业制剂 Glyfonova450 PLUS 在为期两周的暴露试验中，对 Sprague Dawley 大鼠肠道细菌群落组成的影响非常有限。草甘膦对原养型细菌生长的影响高度依赖于芳香族氨基酸的可用性，这表明对细菌组成的观察到的有限影响是由于肠道环境中存在足够量的芳香族氨基酸。在肠道中观察到草甘膦浓度和肠道 pH 值之间存在很强的相关性，这可能部分是由于肠道细菌产生的乙酸减少。我们得出的结论是，饮食中提供足够的肠道芳香族氨基酸水平可减轻细菌合成芳香族氨基酸的需求，从而防止草甘膦在体内产生抗菌作用。然而，在人类营养不良或生产动物的情况下，情况可能有所不同。
