Probiotic Regulation of Vitamin D Receptor in Intestinal Inflammation

Diet in western societies is characterized by a high intake of fat and refined carbohydrates which can alter gut microflora.Gut bacteria can modulate immune function as well as behaviour through the gut-brain axis.Lactobacillus helveticus and Bifidobacterium infantis are probiotics used clinically with immunomodulatory effects.The aim of this study was to examine if host diet alters the ability of probiotics to modulate immune function and behaviour under normal and inflammatory conditions.Methods: At weaning, wild type (WT) and IL-10 deficient (IL-10 -/-) 129/SvEv mice were placed on a standard mouse chow or a western style chow (fat 40%, carb 40%) ± Lactobacillus helveticus ROO52 (10 9 cfu/d) or Bifidobacterium infantis ROO33 (10 9 cfu/d) for 21 days.Animal weight and food eaten were monitored weekly.To examine mucosal immune function, large and small intestine were homogenized and analyzed for cytokine expression by MesoScale discovery platform.Spatial memory and anxiety-like behavior was assessed in a Barnes maze.Terminal Restriction Fragment Length Polymorphism (TRFLP) was used to analyze the faecal microflora in stool samples.Results: WT and IL-10 -/-mice on the western diet had a significantly higher weight gain per mass of food eaten.L. helveticus, but not B. infantis, reduced the western-diet induced weight gain.Mice on the western diet also had decreased microbial diversity and alterations in composition within the phyla Firmicutes.IL-10 -/-mice on normal chow developed colitis with high expression of pro-inflammatory cytokines.A western diet further increased expression of IL-1β and IL-12 in the small intestine, but had an immunosuppressive effect in the colon, with decreased expression of IFNγ, IL-1β, IL-8, and TNFα.L. helveticus prevented the western-diet induced alterations in cytokine expression in the small intestine, but not in the colon.L. Helveticus induced IL-1β, IL-2, IL-4, and IL-5 in WT mice on a chow, but not a western, diet.A western diet suppressed IFNγ, IL-1β, and IL-8 expression in the colon of WT mice, and this was not prevented by L. helveticus.IL-10 -/-mice had greater anxiety and reduced exploratory behavior in the Barnes maze as compared with WT mice.Mice on the western diet had decreased learning ability and enhanced anxiety.L. helveticus enhanced learning ability and increased exploratory behavior in IL-10 -/-mice on both diets.In WT mice, L. helveticus increased exploratory behaviour only in mice on the western diet.Conclusion: Both WT and IL-10 -/-mice on a western diet had increased weight gain, altered gut microflora, an impairment of learning behavior, and altered gut cytokine secretion.The ability of probiotic strains to modulate these factors was genotype-, strain-and diet-dependent.These findings have direct relevance to the clinical use of probiotics.