Targeted stool metabolomics suggests exploratory catecholamine- and tryptophan-linked metabolic features in autism...

Gut-brain axis dysregulation and microbiome-linked metabolic alterations have been implicated in autism spectrum disorder (ASD), but the contribution of gut-derived neuroactive metabolites remains incompletely characterized.

We conducted a cross-sectional case-control study of 59 participants (32 ASD, 27 controls) and quantified 18 stool metabolites related to catecholamine synthesis, inhibitory neurotransmission, and tryptophan-linked NAD+-precursor metabolism using targeted liquid chromatography-tandem mass spectrometry. Group differences were assessed using fold-change analysis and linear models adjusted for age and sex. Random forest models evaluated classification performance, and within-group Spearman correlations were used to examine metabolic relationships.

Norepinephrine showed the largest increase in ASD, whereas dopamine and tetrahydrobiopterin exhibited nominal group differences that did not remain significant after correction for multiple testing. A three-metabolite panel comprising tetrahydrobiopterin, γ-aminobutyric acid, and kynurenine showed exploratory discrimination between groups (area under the receiver operating characteristic curve = 0.750, 95% confidence interval 0.622-0.878), but this performance requires external validation. Correlation analysis revealed conserved bile acid coupling in both groups. In controls, tryptophan was positively associated with kynurenine, whereas this relationship was not observed in ASD. Instead, ASD samples showed broader associations between tryptophan and metabolites linked to neurotransmission and NAD+-precursor metabolism.

Stool metabolite profiling revealed altered organization of tryptophan- and catecholamine-linked metabolic associations in ASD and identified a small metabolite panel with exploratory discriminative potential. These findings provide a foundation for future studies examining gut-derived neuroactive metabolites in ASD and their relationship to gut-brain axis biology.