Complex dietary polysaccharide modulates gut immune function and microbiota, and promotes protection from autoimmune diabetes

Abstract

Summary The dietary supplement and prebiotic values of β ‐glucan‐rich products have been widely recognized and dietary approaches for modulating autoimmunity have been increasingly explored, we assess the impact of oral administration of high‐purity yeast β ‐glucan ( YBG ) on gut immune function, microbiota and type 1 diabetes (T1D) using mouse models. Oral administration of this non‐digestible complex polysaccharide caused a dectin‐1‐dependent immune response involving increased expression of interleukin‐10 ( IL ‐10), retinaldehyde dehydrogenase (Raldh) and pro‐inflammatory cytokines in the gut mucosa. YBG ‐exposed intestinal dendritic cells induced/expanded primarily Foxp3 + , IL ‐10 + and IL‐17 + T cells, ex vivo . Importantly, prolonged oral administration of low‐dose YBG at pre‐diabetic stage suppressed insulitis and significantly delayed the appearance of T1D in non‐obese diabetic ( NOD ) mice. Further, prolonged treatment with YBG showed increased Foxp3 + T‐cell frequencies, and a significant change in the gut microbiota, particularly an increase in the abundance of Bacteroidetes and a decrease in the Firmicute members. Oral administration of YBG , together with Raldh‐substrate and β ‐cell antigen, resulted in better protection of NOD mice from T1D. These observations suggest that YBG not only has a prebiotic property, but also an oral tolerogenic‐adjuvant‐like effect, and these features could be exploited for modulating autoimmunity in T1D.