Fig. 6

Dietary tryptophan availability alters systemic circulating host and bacterial metabolites. Serum was collected from mice fed a low- or high-tryptophan diet colonized with either B6 or B6+L. reuteri microbiota following a 30-day EAE course and analyzed via UPLC-MS/MS as outlined in Fig. 4A, B. Data were analyzed independent of the microbiota to highlight effect of diet alone. A Partial least squares-discriminant analysis (PLS-DA) of total metabolites. B Top 15 metabolites as variables of importance in the PLS-DA projection (VIP) along component 1. C Volcano plot of differentially abundant metabolites, passing a threshold of |FoldChange|>1.5 and P<0.05. Positive fold-change indicates higher abundance in high-tryptophan-fed mice exhibiting higher EAE severity (Fig. 4). Heatmaps of differentially abundant bacterial (C) and mammalian (D) tryptophan-associated metabolites analyzed one-way ANOVA. Post hoc analysis using Fisher’s LSD of selected bile acids (E–H) and nicotinamide associated (I, J) are represented as log-transformed and mean centered abundance plots