Gut microbiome generated phenylacetylglutamine from dietary protein is associated with Crohn's Disease and exacerbates colitis in mouse model possibly via platelet activation.

OBJECTIVES: To better understand the interplay of diet and gut microbiota in Crohn's disease (CD), taking advantage of a newly-onset treatment naïve CD cohort. We focus on phenylacetylglutamine (PAGln), a diet-derived meta-organismal prothrombotic metabolite.

DESIGN: We collected fecal and serum samples from a CD cohort (n=136) and healthy controls (n=126) prior to treatment, and quantified serum PAGln using LC-MS/MS. Diet was assessed using food-frequency questionnaires. Mice (C57BL/6) were fed high/low protein diets and administered DSS to examine plasma PAGly, thrombosis potential, and colitis severity. PAGly or saline was administered to DSS-induced colitis mice, colitis severity and colonic tissue gene expression were examined. P-selectin and CD40L expression were determined in human platelet-rich plasma (n=5-6) after exposure to platelet agonists following PAGln priming. Bioinformatic analysis and bacterial culturing identified the main contributor of PAGln in CD.

RESULTS: PAGln, a meta-organismal prothrombotic metabolite, is associated with CD. Administration of PAGly exacerbated colitis in mouse model and upregulated coagulation-related biological processes. Antiplatelet medicine, dipyridamole, attenuated PAGly enhanced colitis susceptibility. PAGln enhanced platelet activation and CD40L expression in platelet rich plasma ex vivo. Further study revealed that high dietary protein intake and increased abundance of phenylacetic acid (PAA)-producing Proteobacteria mediated by phenylpyruvate decarboxylase act in concert to cause the elevated PAGln levels in CD patients.

CONCLUSION: Taken together, ppdc-carrying Proteobacteria generated PAGln from dietary protein is associated with CD and exacerbates colitis possibly via platelet-induced coagulation and inflammation These results suggest that PAGln is a potential early diagnostic marker and therapeutic target of CD.