Size matters: TLR4-mediated effects of α-(1,5)-linear arabino-oligosaccharides in macrophage-like cells depend on their degree of polymerization.

Linear arabino-oligosaccharides (LAOS) produced from controlled enzymatic hydrolysis of arabinans from sugar beet are well-known because of their chain-length dependent prebiotic effects. However, it is not clear if these α-(1,5)-linked arabinose oligosaccharides can interact directly with immune system cells, as well as if its degree of polymerization (DP) influences possible biological effects. Four high purity LAOS with distinct DP were tested in macrophage-like cells exposed or not to LPS. Results shown that LAOS interact with Toll-like receptor (TLR) 4 in a chain length-dependent manner. LAOS with higher DP induce stimulatory effects mainly through the TLR4/MyD88 pathway, thereby enhancing the release of tumor necrosis factor alpha (TNF-α), interleukin (IL-) 1β, 6, 12, and chemokines including MCP-1, RANTES, IL-8, and IP-10. Notably, LAOS with lower DP appears to have an opposite effect to those counterparts with higher DP, as they does not induce the secretion of cytokines and chemokines in macrophages-like cells, while also inhibit TLR4-mediated effects induced by both lipopolysaccharide and LAOS with higher DP. These findings provide not only insights into potential biological effects of LAOS, but also reveal that controlled enzymatic hydrolysis of sugar beet arabinans may lead to dietary oligosaccharides with desired biological properties.