The kynurenine pathway is upregulated by methyl-deficient diet and changes are averted by probiotics.

SCOPE Probiotics exert immunomodulatory effects and may influence tryptophan metabolism in the host. Deficiency of nutrients related to C1 metabolism might stimulate inflammation by enhancing the kynurenine pathway. We used Sprague Dawley rats to investigate whether a methyl deficient diet (MDD) may influence tryptophan/kynurenine pathways and cytokines and whether probiotics can mitigate these effects. METHODS Rats were fed a control or MDD diet. Animals on the MDD diet received vehicle, probiotics (L. helveticus R0052 and B. longum R0175), choline, or probiotics + choline for 10 weeks (n = 10 per group). Concentrations of plasma kynurenine metabolites and the methylation and inflammatory markers in plasma and liver were measured. RESULTS MDD animals (versus controls) showed upregulation of plasma kynurenine, kynurenic acid, xanthurenic acid, 3-hydroxyxanthranilic acid, quinolinic acid, nicotinic acid, and nicotinamide (all p < 0.05). In the MDD rats, the probiotics (versus vehicle) caused lower anthranilic acid and a trend towards lower kynurenic acid and picolinic acid. Compared to probiotics alone, probiotics + choline was associated with a reduced enrichment of the bacterial strains in cecum.The interventions had no effect on inflammatory markers. CONCLUSIONS Probiotics counterbalanced the effect of MDD diet and downregulated downstream metabolites of the kynurenine pathway. This article is protected by copyright. All rights reserved.