Background/Objectives: Nopalea cochenillifera (L.) Salm-Dyck cladodes are rich in dietary fiber, polyphenols, and minerals, which are known to exert antioxidant and immunomodulatory effects. However, the mechanisms and active constituents have not been fully elucidated. In this study, we investigated the effects of continuous N. cochenillifera consumption on lipid metabolism, immune function, and the gut microbiota in mice. Methods: The feed was made using freeze-dried and powdered cladodes of N. cochenillifera. Male C57BL/6J mice were assigned to four groups: control diet (C), control diet plus 10% N. cochenillifera (CN), high-fat diet (FC), and high-fat diet plus 10% N. cochenillifera (FN). Results: Cactus supplementation reduced the body and liver weights that were elevated by the high-fat diet. Serum total cholesterol and free fatty acids were increased in the FC group compared with the C group, while cactus intake lowered these levels and enhanced fecal cholesterol excretion. Cactus consumption also elevated fecal total IgA and mucin contents. IL-4 expression in Peyer’s patches was significantly increased in the FN group compared with the FC group. Gut microbiota analysis showed significant differences in β-diversity, along with increased α-diversity and higher abundance of Lachnospiraceae, following cactus intake. Conclusions: These findings suggest that N. cochenillifera intake increases gut microbiota diversity, which enhances intestinal barrier function and thereby contributes to improved lipid metabolism and immune regulation.

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.