Deciphering the differential effects of human milk oligosaccharides (HMOs) on infant and adult microbiota: insights from a novel “gut microbe-host interaction” model

Human milk oligosaccharides (HMOs) modulate gut microbiota and intestinal barrier integrity; however, age-dependent microbiota-mediated effects remain insufficiently defined. This study employed a controlled in vitro “microbe-host interaction” model to evaluate direct and fermentation-mediated effects of 2′-fucosyllactose (2’-FL) and 3-fucosyllactose (3-FL) on epithelial barrier function. Infant and adult microbiota were encapsulated and co-cultured with T84 epithelial cells, while barrier resistance and gene expression related to glycocalyx and tight junctions (TJs) were quantified under basal and disruption conditions. 3-FL exerted superior direct protective effects, enhancing glycocalyx-associated gene expression and mitigating barrier impairment. Microbial metabolism differed by age. Infant microbiota produced primarily one of short-chain fatty acids (SCFAs) acetate, lactate, and succinate whereas adult microbiota generated SCFAs, particularly butyrate. Butyrate improved barrier resistance and modulated glycocalyx integrity. These findings demonstrate structure-dependent HMOs activity and age-specific microbial metabolic responses, highlighting mechanistic links between microbial fermentation and epithelial barrier regulation.