Galacto-Oligosaccharides Reshape Mucin O-Glycan Profiles to Enhance Small Intestinal Barrier Development in Early Life.

The mucin barrier is essential for postnatal gut homeostasis, but whether galacto-oligosaccharides (GOS) regulate mucin glycosylation remains unclear. Here, we investigated the effects of early-life GOS supplementation on mucin O-glycans and intestinal barrier development in piglets using UPLC, MALDI-TOF-MS, immunofluorescence, lectin staining, and histomorphological analyses. GOS supplementation significantly increased jejunal villus width, mucosal thickness, goblet cell numbers, and MUC2 expression during early life. Glycomic profiling revealed selective remodeling of mucin O-glycans, characterized by increased core 1/3 and α2,3-sialylated glycans and reduced core 2/4 and α2,6-sialylated structures. These alterations were accompanied by upregulation of C1GALT1, GALNTs, and ST3GALs, and downregulation of ST6GALNACs and neuraminidases. Lectin staining further confirmed enhanced α2,3-sialylation and reduced α2,6-sialylation. Collectively, these results demonstrate that dietary GOS promotes intestinal barrier development and selectively modulates the composition and sialylation of mucin O-glycans, providing novel mechanistic insight into how prebiotics support gut health in early life.