Tian Na, Faller Lina, Leffler Daniel A, Kelly Ciaran P, Hansen Joshua, Bosch Jos A, Wei Guoxian, Paster Bruce J, Schuppan Detlef, Helmerhorst Eva J
Department of Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts, USA.
The Forsyth Institute, Department of Microbiology, Cambridge, Massachusetts, USA.
Appl Environ Microbiol. 2017 Mar 2;83(6). doi: 10.1128/AEM.03330-16. Print 2017 Mar 15.
Celiac disease (CD) is a chronic immune-mediated enteropathy induced by dietary gluten in genetically predisposed individuals. Saliva harbors the second highest bacterial load of the gastrointestinal (GI) tract after the colon. We hypothesized that enzymes produced by oral bacteria may be involved in gluten processing in the intestine and susceptibility to celiac disease. The aim of this study was to investigate salivary enzymatic activities and oral microbial profiles in healthy subjects versus patients with classical and refractory CD. Stimulated whole saliva was collected from patients with CD in remission ( = 21) and refractory CD (RCD; = 8) and was compared to healthy controls (HC; = 20) and subjects with functional GI complaints ( = 12). Salivary gluten-degrading activities were monitored with the tripeptide substrate Z-Tyr-Pro-Gln-pNA and the α-gliadin-derived immunogenic 33-mer peptide. The oral microbiome was profiled by 16S rRNA-based MiSeq analysis. Salivary glutenase activities were higher in CD patients compared to controls, both before and after normalization for protein concentration or bacterial load. The oral microbiomes of CD and RCD patients showed significant differences from that of healthy subjects, e.g., higher salivary levels of lactobacilli ( < 0.05), which may partly explain the observed higher gluten-degrading activities. While the pathophysiological link between the oral and gut microbiomes in CD needs further exploration, the presented data suggest that oral microbe-derived enzyme activities are elevated in subjects with CD, which may impact gluten processing and the presentation of immunogenic gluten epitopes to the immune system in the small intestine. Ingested gluten proteins are the triggers of intestinal inflammation in celiac disease (CD). Certain immunogenic gluten domains are resistant to intestinal proteases but can be hydrolyzed by oral microbial enzymes. Very little is known about the endogenous proteolytic processing of gluten proteins in the oral cavity. Given that this occurs prior to gluten reaching the small intestine, such enzymes are likely to contribute to the composition of the gluten digest that ultimately reaches the small intestine and causes CD. We demonstrated that endogenous salivary protease activities are incomplete, likely liberating peptides from larger gluten proteins. The potentially responsible microbes were identified. The study included refractory CD patients, who have been studied less with regard to CD pathogenesis.
乳糜泻（CD）是一种由膳食麸质在遗传易感个体中引发的慢性免疫介导性肠病。唾液中的细菌载量在胃肠道（GI）中仅次于结肠，位居第二。我们推测口腔细菌产生的酶可能参与肠道中麸质的加工过程以及乳糜泻的易感性。本研究的目的是调查健康受试者与经典型和难治性CD患者的唾液酶活性和口腔微生物谱。从缓解期CD患者（n = 21）和难治性CD（RCD；n = 8）患者中收集刺激后的全唾液，并与健康对照（HC；n = 20）和有功能性胃肠道不适的受试者（n = 12）进行比较。用三肽底物Z - Tyr - Pro - Gln - pNA和α - 麦醇溶蛋白衍生的免疫原性33肽监测唾液中麸质降解活性。通过基于16S rRNA的MiSeq分析对口腔微生物群进行分析。在对蛋白质浓度或细菌载量进行标准化前后，CD患者的唾液谷氨酰胺转氨酶活性均高于对照组。CD和RCD患者的口腔微生物群与健康受试者的口腔微生物群存在显著差异，例如唾液中乳酸杆菌水平较高（P < 0.05），这可能部分解释了观察到的较高的麸质降解活性。虽然CD中口腔和肠道微生物群之间的病理生理联系需要进一步探索，但所呈现的数据表明，CD患者口腔微生物衍生的酶活性升高，这可能影响麸质加工以及免疫原性麸质表位在小肠中向免疫系统的呈递。摄入的麸质蛋白是乳糜泻（CD）肠道炎症的触发因素。某些免疫原性麸质结构域对肠道蛋白酶具有抗性，但可被口腔微生物酶水解。关于口腔中麸质蛋白的内源性蛋白水解加工知之甚少。鉴于此过程发生在麸质到达小肠之前，此类酶可能会影响最终到达小肠并引发CD的麸质消化产物的组成。我们证明内源性唾液蛋白酶活性不完整，可能从较大的麸质蛋白中释放出肽段。鉴定出了可能负责的微生物。该研究纳入了难治性CD患者，在CD发病机制方面对其研究较少。
