Patients with inflammatory bowel disease showed significantly lower serum levels of tryptophan than healthy controls in a recent study. Further, researchers found that among IBD patients, lower tryptophan levels were significantly correlated with increased disease activity.
They concluded that “tryptophan deficiency could contribute to development of IBD.”
Prompted by data from mouse models, investigators from Germany analyzed serum samples from 211 patients with ulcerative colitis and 234 patients with Crohn’s disease to evaluate whether clinical and serologic factors were correlated with levels of tryptophan and its metabolites. They also analyzed serum samples from 291 matched controls, and evaluated stool samples and colonic biopsies from subsets of the study participants.
They found that patients with IBD, especially those with Crohn’s disease, showed significantly lower serum levels of tryptophan compared with controls.
“This confirms earlier observations of reduced [tryptophan] serum levels in smaller cohorts,” the investigators wrote.
Additionally, tryptophan levels were negatively correlated with disease activity or C-reactive protein levels.
They also found that serum tryptophan levels were correlated with fecal microbiota composition, and that patients with active IBD showed higher levels of tryptophan metabolites, especially quinolinic acid, compared with controls, which indicated higher tryptophan degradation in these patients.
“Reduction of [tryptophan] serum levels could be caused by different factors,” including a reduced nutritional state in Crohn’s vs. UC patients, a specific absorption defect, increased catabolism of tryptophan in inflamed mucosa, and the gut microbiota itself, the investigators wrote. “Larger cohort studies in healthy subjects and patients with other inflammatory disorders are therefore warranted to understand the exact influence of host [tryptophan] metabolism on gut microbial communities.”
Finally, the researchers noted that the findings suggest tryptophan and its metabolites show promise as potential biomarkers and therapeutic targets in IBD. – by Adam Leitenberger
Disclosures: One of the researchers reports he is employed by CONARIS Research Institute AG.