Short-chain fructooligosaccharides, in spite of being fermented in the upper part of the large intestine, have anti-inflammatory activity in the TNBS model of colitis

Previous studies have demonstrated the anti-inflammatory effect of fructooligosaccharides (FOS) on intestinal inflammation. The aim of the present study was to elucidate whether the colonic fermentation of these carbohydrates is a prerequisite for this anti-inflammatory activity. With this aim short chain-FOS (SC-FOS) were used for an in vitro fermentation to elucidate the time of fermentation of these compounds. For the in vivo experiments female Wistar rats were fed several diets with different sources of fibre (5 g/kg): cellulose for control rats (n = 30) or SC-FOS (n = 20) with a high content of kestose (GF(2)) for the SC-FOS group. After one month of feeding the different diets 10 rats from each group were sacrificed to analyze cecal and colonic microflora, SCFA production and pH of intestinal contents. A distal colonic inflammation was induced to other 10 rats from each group by the administration of 10 mg of TNBS dissolved in 0.25 ml of 50% ethanol (v/v). The rest of the rats from the control group (n = 10) were rendered healthy. One week after TNBS treatment rats were sacrificed and several inflammatory parameters as well as intestinal microbiota and SCFA contents were analyzed. In vitro fermentation experiments showed that SC-FOS are fermented during the first 12 h after incorporating the oligosaccharides to intestinal contents, thus suggesting a preferential fermentation of these carbohydrates in the ileum and cecum. In fact, SC-FOS increased cecal lactobacilli and bifidobacteria counts as well as SCFA production in healthy rats. In colitic rats, SC-FOS feeding caused a decrease of MPO activity, leukotriene B4 (LTB4) production and iNOS expression. This anti-inflammatory effect was evidenced macroscopically by a significant reduction in the extent of colonic damage. SC-FOS also promoted a more favorable intestinal microbiota, increasing lactobacilli and bifidobacteria counts. In conclusion, although oligosaccharides are preferentially fermented in the upper parts of the large intestine, its prebiotic effect is extended to the distal colonic segments, thus exerting a positive effect on colonic inflammation.