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Oat beta-Glucans were studied for their immunological impact before and after enzymatic digestion in order to enhance the efficacy of oat beta-Glucans for application in functional foods. Oat beta-Glucan is reported to have minimal impact compared to its fungal counterpart in vitro. Digestion with endo-glucanase enhanced its efficacy towards stimulating MCP-1, RANTES, IL-8, and IL-4 production in human dendritic cells as compared to the nondigested beta-Glucan. This effect resulted from an enhanced activation of the Dectin-1 receptor. Our data suggest that the immune-stimulation was dependent on the beta-(1-3) linkages and the reduced particle size of digested beta-Glucans. Thus, we show that enzymatic pre-digestion of dietary fibres such as oat beta-Glucan enhances its impact on specific immune receptors. We also demonstrate that particle size and/or molecular weight of oat beta-Glucans and exposure of specific binding sites for the receptors might be important tools for designing efficacious functional feed and food additives. (C) 2015 Elsevier Ltd. All rights reserved.

ScopeArabinoxylan is one of the most commonly consumed dietary fiber. Immunomodulation by arabinoxylan is documented but the mechanisms by which these immune-effects are accomplished are unknown.Methods and resultsBy applying reporter cell lines for Toll-like receptors (TLRs) and Dectin-1, we demonstrated that arabinoxylan interacts with Dectin-1 receptors and not with TLRs. Arabinoxylan activates Dectin-1 to a similar magnitude as soluble -glucans. Soluble beta-glucans are known to inhibit the particulate beta-glucan-induced activation of Dectin-1. As arabinoxylan is also soluble, the inhibiting capacity of arabinoxylan on particulate -glucan-activated Dectin-1 cell lines was studied. It was found that this inhibition was similar to that of soluble -glucan and was caused predominantly by inhibition of the Dectin-1A transcript variant. The Dectin-1 inhibitory function of arabinoxylan was further confirmed in human dendritic cells that demonstrated reduced production of IL-10 and TNF-alpha The production of the antifungal cytokines IL-4 and IL-23 were increased in dendritic cells stimulated with arabinoxylan and particulate -glucan. In contrast to soluble -glucan, arabinoxylan did not enhance production of IL-10, TNF-alpha, and IL-23.ConclusionArabinoxylan activates Dectin-1 and supports antifungal immune responses in human dendritic cells. The mode of action of arabinoxylan is similar but not identical to that of soluble beta-glucans.

Contains fulltext : 170614.pdf (Publisher’s version ) (Open Access) It has been shown in vitro that only specific dietary fibers contribute to immunity, but studies in vivo are not conclusive. Here, we investigated degree of polymerization (DP) dependent effects of beta2-->1-fructans on immunity via microbiota-dependent and -independent effects. To this end, conventional or germ-free mice received short- or long-chain beta2-->1-fructan for 5 days. Immune cell populations in the spleen, mesenteric lymph nodes (MLNs), and Peyer's patches (PPs) were analyzed with flow cytometry, genome-wide gene expression in the ileum was measured with microarray, and gut microbiota composition was analyzed with 16S rRNA sequencing of fecal samples. We found that beta2-->1-fructans modulated immunity by both microbiota and microbiota-independent effects. Moreover, effects were dependent on the chain-length of the beta2-->1-fructans type polymer. Both short- and long-chain beta2-->1-fructans enhanced T-helper 1 cells in PPs, whereas only short-chain beta2-->1-fructans increased regulatory T cells and CD11b-CD103- dendritic cells (DCs) in the MLN. A common feature after short- and long-chain beta2-->1-fructan treatment was enhanced 2-alpha-l-fucosyltransferase 2 expression and other IL-22-dependent genes in the ileum of conventional mice. These effects were not associated with shifts in gut microbiota composition, or altered production of short-chain fatty acids. Both short- and long-chain beta2-->1-fructans also induced immune effects in germ-free animals, demonstrating direct effect independent from the gut microbiota. Also, these effects were dependent on the chain-length of the beta2-->1-fructans. Short-chain beta2-->1-fructan induced lower CD80 expression by CD11b-CD103- DCs in PPs, whereas long-chain beta2-->1-fructan specifically modulated B cell responses in germ-free mice. In conclusion, support of immunity is determined by the chemical structure of beta2-->1-fructans and is partially microbiota independent.

Sufficient dietary fibre intake reduces the risk of several diseases, but the mechanisms linking fibre structure and health effects remain unclear. To analyse the influence of the amount of methyl groups esterified to the backbone, lemon pectins of different degrees of methyl esterification (30, 56, and 74DM) were studied for immune receptor activating potential and epithelial barrier protection. In reporter assays, the pectins demonstrated TLR/MyD88 dependent activation of NF-kappa B/AP-1, which increased with increasing pectin DM. To analyse the importance of backbone structure, the pectins were enzymatically digested into oligomers, which abrogated TLR activating potential. The 30 and 74DM pectins induced strong protection of the epithelial barrier measured by T84 transepithelial electrical resistance (TEER). These results indicate that activation of immune cells by lemon pectins is TLR dependent, and the intact polymer backbone is indispensable for activation. In addition, DM is a determining factor in activating potential and epithelial barrier protective effects. (C) 2016 Elsevier Ltd. All rights reserved.

Scope: In the present study, the direct interaction of commonly consumed fibers with epithelial or dendritic cells (DCs) was studied.Methods and results: The fibers were characterized for their sugar composition and chain length profile. When in direct contact, fibers activate DCs only mildly. This was different when DCs and fibers were co-cultured together with supernatants from human epithelial cells (Caco spent medium). Caco spent medium enhanced the production of IL-12, IL-1Ra, IL-6, IL-8, TNF-alpha, MCP-1 (monocyte chemotactic protein), and MIP-1 alpha but this was strongly attenuated by the dietary fibers. This attenuating effect on proinflammatory cytokines was dependent on the interaction of the fibers with Toll-like receptors as it was reduced by Pepinh-myd88. The interaction of galacto-oligosaccharides, chicory inulin, wheat arabinoxylan, barley beta-glucan with epithelial cells and DCs led to changes in the production of the Th1 cytokines in autologous T cells, while chicory inulin, and barley beta-glucan reduced the Th2 cytokine IL-6. The Treg-promoting cytokine IL-10 was induced by galacto-oligosaccharides whereas chicory inulin decreased the IL-10 production.Conclusions: Our results suggest that dietary fibers can modulate the host immune system not only by the recognized mechanism of effects on microbiota but also by direct interaction with the consumer's mucosa. This modulation is dietary fiber type dependent.