以肠道菌群为靶向的农用杀菌剂甲霜灵对幼鼠代谢表型的影响及对映体选择性

Nowadays, the amount of the production, usage and residue of fungicides has been unprecedented raised, which increased the personal health risk. As the target of fungicides, microbiota host in child intestinal might be disturbed by the xenobiotics through daily diet, especially when exposure during critical developmental times. Impact of fungicides on host and microbial function has been little studied albeit for the hotspot on the profound influence on human physiology by microbes. Furthermore, chiral nature of fungicides largely injected uncertainty and complex to risk assessment on these fungicides. The current project chooses the widespread used metalaxyl as the model compound to investigate the health risk for chiral fungicides. Firstly, we characterize the residue level of both parental chemical and its metabolite in children. Accordingly, the exposure experiment will take on young mice to clarify the enantioselective alteration of metabolic phenotypes by targeting on gut microbiome. Procedure details are listed as followed: we detected the metagenomics to analysis the perturbation of microbiome by enantiomers of metalaxyl; Build upon metabolomics, we analysis the altered metabolic phenotypes and try to clarify its correlation to the functional changes of gut microbiome. The object of this project is to supplement the information on the risk assessment of the chiral pesticides, and further support original data and pave new way for research on the health risk of children.

农用杀菌剂生产和使用量及环境残留量的日益攀升，增加了其生态及人群健康风险，而人体肠道微生物特别是儿童肠道菌群极易受外源物质尤其是抗生素干扰。然而饮食暴露农用杀菌剂对儿童肠道微生物的扰动及其健康风险几乎处于空白。而某些杀菌剂的手性特征又增加了风险评估不确定性及复杂性。本项目拟选择甲霜灵为模式化合物,一方面，从甲霜灵在儿童尿液中的残留水平及可能的手性代谢产物分析入手，评估人体甲霜灵残留现状，为在体实验暴露剂量的选定做出参考，同时通过对儿童尿液分析可以表征人体代谢特征；另一方面，以3周龄断奶幼鼠为研究模型，运用整体代谢组学技术检测幼鼠对甲霜灵各异构体应答的代谢指纹图谱，结合肠道元基因组测序方法分析肠道菌群的结构及功能的改变；推断甲霜灵的选择性代谢差异对肠道菌群的干扰而导致宿主代谢表型改变的潜在机制。本研究为儿童时期农用杀菌剂暴露的健康风险评价提供新的研究思路，为手性农药健康风险的评价注入新的数据

在项目执行的周期内，项目组成员严格按照计划任务书，聚焦甲霜灵对青春期小鼠肠道微生物扰动和代谢表型变化为核心，开展手性作物杀菌剂对非靶标生物毒性效应的机制研究。研究发现甲霜灵对映体会干扰大鼠体内的正常代谢活动，且两种对映体造成的干扰效应具有对映体选择性。甲霜灵对映体的暴露过程中，大鼠的生物代谢网络必然会受到影响，相应的，其内源性代谢物的种类及浓度也会发生改变。当大鼠暴露在R-甲霜灵时，大鼠体内共3条通路发生了显著性变化，包括缬氨酸、亮氨酸以及异亮氨酸的合成通路，酮体的合成和降解通路，甘油酯代谢通路。而在S-甲霜灵暴露后，共有6条通路发生了显著性改变，分别是糖酵解通路，缬氨酸、亮氨酸、异亮氨酸的合成通路，甘氨酸、丝氨酸、苏氨酸的代谢通路，酮体的合成和降解通路，甘油磷脂的代谢通路，以及甘油脂的代谢通路。大鼠肠道内容物丁酸盐类小分子在R-甲霜灵暴露下显著上调。对比R-甲霜灵暴露后幼年大鼠肠道菌群变化发现肠道中与肠道屏障通透性相关的菌群和丁酸盐代谢相关肠道微生物发生了显著地扰动效应。结合肠道菌群变化和肠道内容物代谢小分子分析，说明R-甲霜灵杀菌活性强的异构体可能通过干扰肠道微生物进而引起肠道内容物小分子丁酸盐类化合物的变化，而丁酸盐类小分子又是引发生物体免疫紊乱的潜在因素。