Sustained Diet-Induced Remission in Pediatric Crohn's Disease Is Associated With Kynurenine and Serotonin Pathways.

Inflammatory bowel diseases. 2023;29(5):684-694

Plain language summary

Crohn’s disease (CD) is an inflammatory bowel disease associated with alterations in intestinal tryptophan metabolism, in particular with increases in metabolites of the kynurenine pathway and decreased metabolites of the serotonin pathway. The aim of this 12-week randomised clinical study was to evaluate the effect of CD exclusion diet with partial enteral nutrition (CDED+PEN) and exclusive enteral nutrition (EEN) on intestinal tryptophan metabolism (as measured in faeces) in 43 children with mild-to-moderate CD. 13 of 15 patients on CDED+PEN and 9/13 on EEN achieved remission at week 6, and 8/9 and 6/9 patients, respectively, maintained remission at 12 weeks. Some kynurenine pathway metabolites decreased and some serotonin metabolites increased, in patients who achieved induction and maintenance of remission. These changes were similar in both intervention groups. On the other hand, in patients on EEN who did not go into remission, these changes were not observed. The authors concluded that further studies are warranted to inform whether there is a causal link and to refine nutritional interventions.


BACKGROUND Both the Crohn's disease exclusion diet combined with partial enteral nutrition (CDED+PEN) and exclusive enteral nutrition (EEN) can induce remission in mild-to-moderate pediatric Crohn's disease and are associated with a marked decrease in fecal kynurenine levels. This suggests a link between clinical outcome of dietary therapy and changes in tryptophan metabolism pathways. Here, we characterize the changes in several fecal tryptophan metabolites induced by CDED+PEN or EEN and their association with remission. METHODS A total of 21 tryptophan metabolites were quantified in fecal samples from a 12-week prospective randomized trial with CDED+PEN or EEN for induction of remission in mild to moderate pediatric Crohn's disease. Tryptophan metabolites at week 0 (W0), W6, and W12 of 73 samples were quantitatively measured by liquid chromatography coupled with triple quadrupole mass spectrometry, and data were analyzed according to clinical groups of baselines (W0), induced remission at W6, no remission, sustained remission at W12, and nonsustained remission. RESULTS Reduction in components of the kynurenine pathway, such as kynurenine and quinolinic acid, were strongly associated with induced remission with both CDED+PEN and EEN, which were maintained in sustained remission. Specific serotonin pathway metabolites, such as melatonin, N-acetylserotonin, and 5-OH-tryptophan, were significantly increased in fecal samples from patients maintaining remission at W12 with both CDED+PEN and EEN. Importantly, in samples from patients failing to sustain remission, no changes were observed. Remission induction with EEN differs from CDED+PEN, particularly the moderate effects on indole pathway metabolites. The ratios of kynurenine and melatonin and quinolinic acid and melatonin perform well as markers for sustained remission. CONCLUSIONS The reduction in specific kynurenine pathway compounds and the increase in serotonin pathway compounds are associated with diet-induced and sustained remission. Further studies are warranted to assess causality and the association of these metabolites with specific diet and lifestyle factors, affecting sustained clinical remission. We show that fecal tryptophan metabolites are associated with remission following dietary therapy in a prospective clinical trial of pediatric Crohn’s disease patients. Our study shows that reduction in some kynurenine pathway metabolites and the increase in serotonin pathway compounds are associated with diet-induced and sustained remission. These compounds may play a role in mediating the mechanism of action of dietary therapy.

Lifestyle medicine

Patient Centred Factors : Mediators/Tryptophan metabolites
Environmental Inputs : Diet
Personal Lifestyle Factors : Not applicable
Functional Laboratory Testing : Stool

Methodological quality

Jadad score : 1
Allocation concealment : Not applicable


Nutrition Evidence keywords : Enteral nutrition ; Exclusion diet