Fecal tryptophan metabolism predicts the development of infant eczema: a prospective longitudinal study
Author(s)
Type
Journal Article
Abstract
Early-life microbial metabolism of tryptophan plays a critical role in immune modulation and may influence susceptibility to inflammatory disorders such as eczema. However, longitudinal human data linking microbial tryptophan metabolism to eczema onset are limited. We conducted a prospective cohort study of 40 term-born UK infants, followed from birth to 24 months, stratified by early-onset (infants developing eczema <12 months, n = 12) or late-onset (infants developing eczema ≥12 months, n = 7) doctor-diagnosed eczema. Fecal samples underwent targeted tryptophan LC–MS metabolomics and 16S rRNA sequencing. Tryptophan metabolomics revealed dynamic changes in tryptophan metabolites that were associated with disease status compared to healthy infants. Infants with early-onset eczema (<12 months) exhibited elevated tryptophan and tryptamine levels at 6 months, while those with late-onset eczema (≥12 months) showed reduced indole-3-lactic acid (ILA) levels prior to diagnosis at 9 months. 16S and metabolomics correlations highlighted a metabolic shift in Bifidobacterium from ILA, a metabolite that predominated fecal metabolome during early infancy but decreases by 12 months, coinciding with increased indole-3-aldehyde (I3AD) metabolism by Bifidobacterium. Receiver operating characteristic (ROC) curve analysis identified a small panel of early predictive indole-pathway markers, including tryptophan and the indole/indole-3-sulfate (I3S), I3S/ILA, and tryptophan/ILA ratios, discriminating both early- and late-onset eczema development. Our findings reveal distinct, time-dependent disruptions in microbial tryptophan cometabolism associated with eczema onset. ILA may serve as a biomarker for the diagnosis of infantile eczema. Further validation studies to establish its clinical utility are now required.
Date Issued
2026-12-31
Date Acceptance
2026-03-31
Citation
Gut Microbes, 2026, 18 (1)
ISSN
1949-0976
Publisher
Taylor & Francis Group
Start Page
2655171
Journal / Book Title
Gut Microbes
Volume
18
Issue
1
Copyright Statement
© 2026 The Author(s). Published with license by Taylor & Francis Group, LLC.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permitsunrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allowthe posting of the Accepted Manuscript in a repository by the author(s) or with their consent.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41947046
Subjects
Infantile eczema
infant gut microbiome
longitudinal
tryptophan metabolism
Humans
Tryptophan
Infant
Feces
Prospective Studies
Longitudinal Studies
Male
Female
Eczema
Gastrointestinal Microbiome
Infant, Newborn
Metabolomics
Biomarkers
Bifidobacterium
Bacteria
Indoles
RNA, Ribosomal, 16S
Metabolome
United Kingdom
Publication Status
Published
Coverage Spatial
United States
Article Number
2655171
Date Publish Online
2026-04-07