Dietary Agaro-Oligosaccharides Are Associated with Higher Colonic Mucin-Related Marker Levels in Mice and MUC2 mRNA Expression in HT-29 Cells

Agaro-oligosaccharides (AOSs) are agar-derived oligosaccharides composed of D-galactose and 3,6-anhydro-L-galactose. This study investigated the effects of dietary AOS on colonic mucin-related markers and their relationships with the cecal microbiota and short-chain fatty acids (SCFAs) in normal mice. Female BALB/c mice received a control diet or a diet with 5% cellulose replaced by AOS for 28 days (six mice in two cages per group). Colonic mucin-related markers, cecal microbiota, and SCFAs were assessed alongside in vitro experiments using Akkermansia muciniphila and HT-29 cells. AOS increased colonic Alcian blue–periodic acid–Schiff-positive area, fecal mucin content, and colonic Muc2 and Spdef mRNA expression. 16S rRNA sequencing revealed higher Akkermansia abundance, while species-specific qPCR indicated a higher A. muciniphila-to-total bacterial 16S rRNA gene copy ratio. Cecal acetate, propionate, and butyrate concentrations decreased; estimated total amounts decreased for acetate and butyrate but not significantly for propionate. In vitro, AOS increased A. muciniphila culture OD660 at 0.2–0.5% but decreased it at 1.0% and increased HT-29 MUC2 mRNA expression after 2 h. Despite limited cage-level replication and untested barrier function and microbial causality, these findings associate dietary AOS substitution with increased colonic mucin-related markers and a short-term MUC2 mRNA response in HT-29 cells.