Effects of 1-Kestose and Nystose on the Intestinal Microorganisms and Immune System in Mice

Abstract

Fructooligosaccharides (FOSs) are short and medium chains of fructose in which two to nine fructosyl units are bound by β2,1glycosidic linkages and a glucose molecule is present at the end of the chain joined by an α1,2 glycosidic bond. Fructooligosaccharides occur in various plants such as onions, asparagus, artichokes and garlic. 1) Shortchain FOSs (scFOSs), such as 1kestose, nystose and 1Fβfructofuranosylnystose can also be enzymatically synthesized from sucrose. 2,3) Fructooligosaccharides are prebiotics that have been studied in detail and they are widely used as a food ingredient. 46) A commercially available FOS product comprises a mixture of scFOSs. 4) The primary physiological function of FOSs is the preferential stimulation of colonic Bi-fidobacteria. The effect has been confirmed in experimental animal models and in humans. 710) Other physiological functions of FOSs include the improvement of calcium bioavailability, the modulation of lipid metabolism and the inhibition of potential pathogen metabolism. 5,11,12) These functions are mainly due to the indigestibility 13) and selective fermentability of FOSs in the gastrointestinal system. 14) Studies have recently focused more on the immuno-modulating effect of oligosaccharides. 15,16) Nakamura et al. 17) reported that FOSs enhance the IgA response in the intestine of infant mice and Hosono et al. 18) also showed that the amounts of fecal IgA and of IgA secretion by Peyer s Patch cells are increased in FOStreated mice. Furthermore, Nicole et al. 19) and Pierre et al. 20) demonstrated that dietary FOSs influence gutassociated lym-phoid tissue. Although beneficial colonic bacteria proliferation and shortchain fatty acid production in the gut are thought to be involved in the action mechanism of FOSs on the immune system, details have not been fully established. Furthermore , whether the prebiotic and immunomodulating activities differ among FOSs in vivo and in vitro remains obscure. We investigated the effects of 1kestose and nystose, which are major components of a dietary FOSproduct, on intestinal microorganisms and on the splenocyte response to mitogenic stimulation in mice. MATERIALS AND METHODS Animals. Female 6weekold BALBc mice obtained from Charles River Japan (Yokohama, Japan) were maintained at 2224 C and around 50% relative humidity under a 12 h lightdark cycle. A commercial diet (CE2, Clea Japan, Tokyo, Japan) and water were available ad libitum. The mice were separated by body weight into three experimental groups consisting of five animals. The experimental protocol was approved by the Animal Experiment Committee of Rakuno Gakuen University and the animals were managed in accordance with the Guide for the Care and Use of Laboratory Animals of the same institution. Bacterial strains. Lactobacillus reuteri JCM 1081, Lactobacillus murinus JCM 1717 T and Lactobacillus in-testinalis JCM 7548 T purchased from the Japan Collection of Microorganisms were cultured at 37 C in MRS medium for DNA extraction. Preparation and administration of 1-kestose and nystose. Crystalline 1kestose and nystose were prepared by the method of Takeda et al. 3) The FOSs were dissolved in sterilized distilled water at a concentration of 10 mgmL and orally administered to mice via an intubation Abstract: We investigated the effects of the major short chain fructooligosaccharides, 1-kestose and nystose, on the intestinal microorganisms and on the intestinal and systemic immune responses of mice. Both 1-kestose and nystose promoted intestinal Lactobacillus number. However, the balance of Lb. reuteri and Lb. intesti-nalis, the major Lactobacillus species in the mice was not altered. The IgA content in the feces of mice treated with both 1-kestose and nystose increased from day 4 to day 7 after starting the administration and returned to the same level of control mice on day 14. Splenocyte responses to Con A, anti-CD3 plus anti-CD28 antibod-ies and LPS were reduced by 1-kestose and nystose. Nystose lowered IL-2, IFN-γ, IL-12 and IL-4 secretion from the splenocytes more than 1-kestose. These results suggested that both 1-kestose and nystose can influence the microorganisms as well as the intestinal and systemic immune responses, but to different degrees.