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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.

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.

SCOPE: The major receptor for β(1-3)-glucans on immune cells is considered to be Dectin-1 receptor. Particulate β-glucans induce stronger immune responses than soluble β-glucans by clustering of Dectin-1 receptors. Here it was hypothesized that activation of other pattern recognition receptors such as Toll-like receptor 4 (TLR4) activation can also contribute to enhanced activity of immune cells after exposure to particulate β-glucans.METHODS AND RESULTS: To test this hypothesis, reporter cell lines were designed expressing TLR4 with either Dectin-1A or Dectin-1B, i.e. one of the two transcript variants of human Dectin-1 receptors. Enhanced NF-κB activation was observed after stimulation with particulate β-glucans in both Dectin-1A-TLR4 and the Dectin-1B-TLR4 cell lines. This was different with soluble β-glucans, which enhanced activation in Dectin-1A-TLR4 cell lines but not in Dectin-1B-TLR4 cells. The synergistic activation of TLR4 and Dectin-1 by particulate β-glucans was confirmed in human dendritic cells. The effects of particulate β-glucan induced TLR4-binding were regulatory as blocking TLR4 enhanced pro-inflammatory cytokine IL-23, IL-4, IL-6, and TNF-α production.CONCLUSION: These results suggest that TLR4 and Dectin-1 are synergistically activated by particulate β-glucans wherein, TLR4 activates an immune regulatory pathway in human dendritic cells. Our data suggest that β-glucan is an immune-regulatory ligand for TLR4. This article is protected by copyright. All rights reserved.

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.