Prebiotic effect of Yacon in the intestinal microbiota, the Mucosal Immune System and the prevention of enteric diseases

BIBAS BONET, M.E.; VELEZ, E.M.; MESON O.; PERDIGÓN, G.

Puerto Vallarta

Workshop; 5th International Nutritional Workshop - XI Curso de Inmunonutrición. Puerto Vallarta, Mexico; 2011

In the last decades, there has been an increasing interest in the relation between colonic function and health. There are literatures suggesting that large amounts of unrefined plant foods, especially all starchy foods rich in dietary fibre, may offer protection against several diseases of the large intestine.Dietary carbohydrates that escape digestion in the small intestine undergo bacterial fermentation in the colon. This process affects the microbial ecology of the gastrointestinal tract and influences gut metabolism and function. Prebiotics are non-digestible but fermentable oligosaccharides that are specifically designed to change the composition and activity of the intestinal microbiota with the prospect to promote the health of the host. Their fermentation results in the acidification of the colonic contents and the formation of short chain fatty acids which serve as fuels in different tissues and may play a role in the regulation of cellular processes. Prebiotics specifically stimulate the growth of endogenous microbial population groups such as bifidobacteria and lactobacilli which are perceived as being beneficial to human health. The concept of prebiotics arose from the observation that inulin and fructooligosaccharides selectively stimulate the growth of bifidobacteria. Other non-digestible oligosaccharides (NDO) including xylooligosaccharides, galactooligosaccharides and isomaltooligosaccharides have also been tested for their prebiotic effect. The majority of candidate prebiotics are oligosaccharides but also include polysaccharides. To serve as a bacterial substrate in the colon, a prebiotic may not be hydrolyzed or absorbed in the upper part of the gastrointestinal. Some studies reported also potential immune-modulating properties to the prebiotics. Smallanthus sonchifolius (yacon), originating from South America, has become popular in Japan and in New Zealand for its tubers which contain beta-1,2-oligofructans as the main saccharides. The plant is also successfully cultivated in Central Europe, particularly in the Czech Republic. However, additional studies are needed to show that prebiotics and specially yacon can directly or indirectly stimulate intestinal host defenses. We evaluated the prebiotic property of yacon root flour and its influence on the intestinal microbiota and the gut immune system using a mice model, after a long-term daily consumption. We analyzed the intestinal microbiota mainly focus in bifidobacteria population. The effect on total IgA in intestinal fluid, the number of IgA +, Th1+ and Th2+ cell populations, the cells producing IL12, IL10, IL4 and IFN-g measured in the lamina propria of the small and large intestine, as well as the number of mast cell were evaluated. Histological studies of the gut, to evaluate possible modifications in this tissue due to the long term of yacon administration, and the protection against Salmonella infection were also analyzed. The results show the prebiotic effects of yacon root flour, stimulating the growth of bifidobacteria and lactobacilli in the large intestine of the mice. In the intestinal immune system, we observed an increase in total IgA, in the number of IgA+ cells, mast cells, IL4, IL10 and IFN-g producing cells, and no effect in the number of Th1 and Th2 populations. Long term of yacon root flour administration maintained the intestinal homeostasis without inflammatory effects, regulated mainly through IL-10 and IL-4 regulatory cytokines. As regard the protective effect against Salmonella enterica serovar Typhimurim infection, we observed that there was not a correlation between the number of IgA+ cells and the secretion of specific antibodies against the pathogen. The TLR4+, CD206+, IL6+ and MIP 1a+, TNF-a and IFN-g cells were increased in the lamina propria of the small intestine, as well as the phagocitic activity of the peritoneal macrophages. We demonstrated that fructooligosaccharides from Yacón roots prevent S. Typhimurium infection up to 30 days of administration through non-specific immunity with increased total s-IgA, expression of TLR4 and CD206 receptors, IL6+ and MIP1α + cells, that would improve immunological barrier mechanisms against S. Typhimurium infection.