In vivo effects of dietary (1→3), (1→4)-β-D-glucans from oat on mucosal immune responses in man and mice.

Objective: Antimicrobial peptides and tight junction proteins are crucial to maintain mucosal immunity. It is known that oat β-glucan may affect intestinal immunity. Therefore, the aim of the present study was to evaluate the effect of oat β-glucan on the presence of antimicrobial peptides and tight junction protein.

Material And Methods: We analyzed antimicrobial peptide levels in fecal water prepared from 24 h ileostomic bag contents obtained from ileostomic patients consuming oat β-glucan enriched or control diets in a cross-over design. In addition, intestinal sections of mice, which received oat β-glucan via oral gavages for 3.5 days, were analyzed for lysozyme and zonula occludens-1 expression.

Results: We observed a trend toward lower lysozyme (-23%; p = 0.076) and bactericidal/permeability-increasing protein (-17%; p = 0.098) levels in oat β-glucan enriched fecal water as compared with placebo. Additionally, mice receiving oat β-glucan showed a lower lysozyme expression in stained distal small intestinal sections (p = 0.011). Staining of zonula occludens-1 was decreased in β-glucan treated mice indicating disruption of the tight junction integrity.

Conclusions: In conclusion, the consumption of oat β-glucan seems to decrease the levels of antimicrobial peptides in fecal water from human ileostomy patients and its expression in distal small intestine sections in mice. The decreased intestinal integrity in mice could be explained by the drop in antimicrobial peptides.