Gut microbiota-driven dysbiosis of the SCFA-immune axis in pediatric allergic rhinitis-constipation comorbidity: mechanisms and synbiotic remodeling.

BACKGROUND

The coexistence of allergic rhinitis (AR) and functional constipation (FC) in children reflects complex gut-immune interactions; however, the contribution of microbiota-derived short-chain fatty acids (SCFAs) to immune-metabolic dysregulation remains poorly defined.

METHODS

Fecal microbiota from 57 AR-FC children (aged 0-6 years) and 59 age-matched healthy controls (HC) were profiled using 16S rRNA gene sequencing, and functional pathways were inferred via PICRUSt2. A subset of 13 preschoolers (aged 3-7 years) underwent a 3-month synbiotic intervention (multi-strain probiotics combined with dietary fiber), with paired pre- and post-treatment samples analyzed.

RESULTS

AR-FC subjects exhibited reduced α- diversity (P = 0.003) and depletion of SCFAs-producing taxa (Faecalibacterium prausnitzii: Log2FC = -2.1, P = 0.001; Bacteroides stercoris: Log2FC = -1.8, P = 0.005). Alterations were observed in functional pathways, including upregulated proteasome activity (P = 0.01, potentially linked to antigen processing) and suppressed LPS biosynthesis (P = 0.02, suggestive of impaired innate immunity). Synbiotic administration enriched Faecalibacterium abundance (+54.8%, P < 0.05) and alleviated constipation but reduced Bifidobacterium (-85.2%, P < 0.05), reflecting substrate competition. Following synbiotic intervention, metabolic remodeling was characterized by increased sulfur assimilation (+83.2% sulfate reduction, P = 0.04) and diminished β-lactam resistance (-35.4%, P = 0.03).

CONCLUSION

Gut dysbiosis in AR-FC comorbidity is associated with disruption of the microbiota-SCFA-immune axis, which may correlate with mucosal barrier defects and a potential bias toward T helper 2 (Th2) polarization. Although synbiotic therapy induced taxonomic shifts and improved gastrointestinal function, our findings highlight the need for strain-specific formulations to achieve comprehensive immune and intestinal restoration.