Dietary (1→3), (1→4)-β-d-glucans from oat activate nuclear factor-κB in intestinal leukocytes and enterocytes from mice

Dietary components, like β-glucans, can modulate the intestinal immune response. We previously showed that fecal water enriched with oat β-glucan stimulated the cytokine-induced immune response of enterocytes. It is, however, unclear whether β-glucans activate nuclear factor-κB (NF-κB) pathways in the intestine in vivo and if so, whether enterocytes, intestinal leukocytes, or both respond to β-glucans. We evaluated the effects of an oral gavage of 3 mg dietary oat (1→3), (1→4)-β-d-glucans that was administered twice daily during 3.5 days on intestinal NF-κB transactivation and subsequent cytokine production of intestinal leukocytes and enterocytes in 16 NF-κB reporter mice. We hypothesized that oat β-glucan activates the central immune transcription factor NF-κB and increased cytokine secretion, as we previously reported immune stimulating effects by oat β-glucan. We found that mice that were administered oat β-glucans (n = 8) showed an increased intestinal NF-κB transactivation in leukocytes (P = .021) and enterocytes (P = .012), particularly in the proximal part of the small intestine (ileum), as compared to placebo mice (n = 8). Surprisingly, NF-κB was not activated in the colon. Furthermore, the level of interleukin 12 was increased in intestinal lysates from all compartments, whereas the concentration of interferon γ was decreased in the proximal small intestine (P = .046). Finally, tumor necrosis factor α showed a trend toward a reduced production in the colon (P = .057). Because we have earlier shown that human enterocyte cell lines do not express the β-glucan receptor dectin-1 in vitro, we now conclude that after consumption, dietary oat β-glucans most likely firstly activate the intestinal leukocytes, which in turn increases cellular activation of enterocytes.