Prebiotic modulation of FMT donor microbiota enhances MASLD-relevant taxa and functions in an in vitro gut model

Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly non-alcoholic fatty liver disease) is a prevalent and progressive condition closely linked to gut microbiota composition. Fecal microbiota transplantation (FMT) may help restore a health-associated microbiome, but its efficacy is often limited by inconsistent engraftment of beneficial taxa. Prebiotics may selectively support keystone microbes associated with reduced MASLD risk. This study evaluated two prebiotics, inulin and xylooligosaccharides (XOS), for their ability to modulate the microbiota of healthy FMT donors in an in vitro gut model, focusing on enriching beneficial taxa and functions associated with MASLD resilience.

Stool from eight clinically qualified FMT donors was cultured anaerobically for 24 h with or without prebiotics. Microbiota composition was assessed by 16S rRNA gene sequencing and short-chain fatty acid (SCFA) concentrations were measured using nuclear magnetic resonance. Functional potential was inferred using predictive metagenomic analysis. Prebiotic responses were highly donor-specific, yet both inulin and XOS consistently enriched Bifidobacterium and Bacteroides-genera associated with SCFA production and metabolic health. XOS preferentially enriched Lactobacillus and Parabacteroides, while inulin enhanced Holdemanella and Mediterraneibacter. Functional pathways relevant to MASLD pathophysiology were enriched, including carbohydrate metabolism, vitamin biosynthesis, fatty acid metabolism, and tryptophan degradation. Both prebiotics significantly increased acetate levels, while butyrate showed a donor-dependent increasing trend.

These findings suggest that prebiotic supplementation can selectively enrich MASLD-relevant microbial taxa and functions in donor-derived FMT material, supporting their potential as adjuvants to enhance the efficacy and disease-specificity of FMT interventions for MASLD.