益生菌中的D-色氨酸对肠道微生物群及过敏性呼吸道疾病的影响

D-Tryptophan from probiotic bacteria influences the gut microbiome and allergic airway disease

Kepert et al. Journal of Allergy and Clinical Immunology  (2016)

DOI 10.1016/j.jaci.2016.09.003 

益生菌已被证明可改变免疫反应，是免疫疾病中的替代疗法之一。然而，除了急性感染性腹泻，临床试验对益生菌针对不同的适应症的一级预防效果高度不一致。欧洲食品安全局指出，益生菌在预防过敏症状方面的作用尚未确定。

即使在健康个体中，肠道微生物群在个体中也存在显著差异，在疾病条件下，微生物群以及免疫力也可能发生实质性改变。因此，很难预测单个患者益生菌菌株的精确功能。从益生菌中提取的特定物质是一种潜在的替代方法。

本研究旨在鉴定和表征一种生物活性益生菌代谢产物，以预防过敏性气道疾病。

Abstract

Background: Chronic immune diseases, such as asthma, are highly prevalent. Currently available pharmaceuticals improve symptoms but cannot cure the disease. This prompted demands for alternatives to pharmaceuticals, such as probiotics, for the prevention of allergic disease. However, clinical trials have produced inconsistent results. This is at least partly explained by the highly complex crosstalk among probiotic bacteria, the host’s microbiota, and immune cells. The identification of a bioactive substance from probiotic bacteria could circumvent this difficulty. 

Objective: We sought to identify and characterize a bioactive probiotic metabolite for potential prevention of allergic airway disease. 

Methods: Probiotic supernatants were screened for their ability to concordantly decrease the constitutive CCL17 secretion of a human Hodgkin lymphoma cell line and prevent upregulation of costimulatory molecules of LPS-stimulated human dendritic cells. 

Results: Supernatants from 13 of 37 tested probiotic strains showed immunoactivity. Bioassay-guided chromatographic fractionation of 2 supernatants according to polarity, followed by total ion chromatography and mass spectrometry, yielded C11H12N2O2 as the molecular formula of a bioactive substance. Proton nuclear magnetic resonance and enantiomeric separation identified D-tryptophan. In contrast, L-tryptophan and 11 other D-amino acids were inactive. Feeding D-tryptophan to mice before experimental asthma induction increased numbers of lung and gut regulatory T cells, decreased lung TH2 responses, and ameliorated allergic airway inflammation and hyperresponsiveness. Allergic airway inflammation reduced gut microbial diversity, which was increased by D-tryptophan. 

Conclusions: D-tryptophan is a newly identified product from probiotic bacteria. Our findings support the concept that defined bacterial products can be exploited in novel preventative strategies for chronic immune diseases.

关键词：肠道微生物；D-色氨酸；益生菌；细菌代谢物；免疫调节；过敏性气道疾病

研究对象：6至8周大的雌性BALB/C小鼠

实验方法：为了定量测定小鼠血清中的D-色氨酸，将D-色氨酸（Sigma Aldrich，St.Louis，USA）溶解在浓度为1.8mg/dl或18mg/dl（每只小鼠约0.09和0.9mg/天）的饮用水中。对照动物接受纯水（每组n=8）。为了检测过敏性呼吸道疾病的预防作用，小鼠在第一次致敏前至少提前3天开始接受50毫摩尔/升D-色氨酸，直到第25天死亡。

检测方法：16S rRNA 基因组测序

研究结果：

1.在实验性哮喘诱导之前，向小鼠喂食D-色氨酸，可以增加肺和肠道调节性T细胞数量，降低肺Th2反应，改善过敏性气道炎症和高反应性；

2.过敏性气道炎症降低了肠道微生物的多样性，但D-色氨酸诱导肠道调节性T细胞增殖，增加过敏性气道炎症的肠道微生物多样性。

结论：D-色氨酸（bacteria-derived D-tryptophan）是一种新发现的益生菌产物，它的作用可能比之前所认为的要广泛。我们的研究结果表明，这类益生菌产物，可能会被用于慢性免疫疾病新的预防策略。

Figure 1. Oral D-Tryptophan reduces allergic airway inflammation. 

图1. 口服D-色氨酸减少过敏性气道炎症。

知几未来研究院正在搭建一个“疾病-肠道菌群”知识库。

你可以在公众号对话框回复“IBD”或“肠易激综合征”，查看与疾病相关的菌群；

也可以回复“双歧杆菌”或“Hp”，查看与细菌相关的疾病。

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