Fecal microbiota imbalance in Mexican children with type 1 diabetes Original paper

What was studied?

This study characterized the Mexican-children-type-1-diabetes-gut-microbiome signature by comparing fecal bacterial community structure in pediatric type 1 diabetes (T1D) at diagnosis versus longer-term insulin-treated T1D and healthy controls. Using 16S rRNA (V4) amplicon sequencing (454 pyrosequencing) plus HLA risk haplotyping and clinical-history capture, the investigators asked whether T1D status and disease stage aligned with reproducible genus-level shifts rather than broad phylum changes, and whether insulin treatment corresponded to partial “normalization” of the community profile.

Who was studied?

The cohort comprised 29 Sonoran (northwest Mexico), predominantly “mestizo” children aged 7–18 years: 8 newly diagnosed T1D cases (<2 months duration), 13 established t1d cases on insulin for ≥2 years with hba1c <8%, and 8 healthy controls (including 4 siblings of cases). all participants were antibiotic-free at least 3 before stool collection; notably, reported antibiotic treatment frequency in the year(s) diagnosis was higher than controls, a relevant exposure when interpreting microbiome differences. genetically predisposed: nearly carried one hla risk allele, high prevalence drb104 (DR4) and DRB103 (DR3) variants.

Most important findings

Overall alpha diversity (within-sample diversity) did not differ significantly across groups, but beta diversity showed that newly diagnosed T1D cases clustered apart from controls, indicating a distinct community structure at disease onset. The separation was driven primarily at the genus level: controls exhibited a Prevotella-dominant profile, whereas new-onset T1D showed significantly higher Bacteroides and reduced Prevotella, with additional depletion of Megamonas and Acidaminococcus. Children treated for ≥2 years displayed intermediate abundances, suggesting partial movement toward the control-like (Prevotella-richer) state with insulin treatment, though treated individuals were more heterogeneous and did not form a tight cluster. Importantly for a microbiome signatures database, the discriminating signal here is best summarized as a Prevotella-dominant (control) versus Bacteroides-enriched (new-onset T1D) enterotype-like pattern, without a significant Bacteroidetes/Firmicutes ratio difference, emphasizing that genus-level directionality is the clinically salient layer.

Key implications

Clinically, these data support the idea that pediatric T1D—especially at onset—correlates with a fecal microbiome configuration consistent with impaired mucosal barrier support (Prevotella-poor) and increased representation of taxa (Bacteroides) hypothesized to influence mucus dynamics and gut permeability pathways, but the cross-sectional design cannot establish causality. For translation, the most usable “signature” is the onset-specific shift toward Bacteroides enrichment with concomitant Prevotella depletion, while insulin-treated patients may partially revert yet remain variable—highlighting stage, recent antibiotic history, and diet as essential covariates when interpreting microbiome biomarkers or designing interventions.

Citation

Mejía-León ME, Petrosino JF, Ajami NJ, Domínguez-Bello MG, Calderón de la Barca AM. Fecal microbiota imbalance in Mexican children with type 1 diabetes. Sci Rep. 2014;4:3814. doi:10.1038/srep03814