GI bacteria changes in animal models due to prebiotics
Résumé
Publisher Summary Studies using a mixed fiber diet have emphasized the strong impact of dietary fibers (DF) on gut microbiota. As an example, a high-fiber diet containing 40% soya cake, 20% crude potato starch, 19% wheat bran, and 5% each of apple pectin and carob gum, given for 4 weeks to rats, led to a daily fecal output of anaerobes 71 times higher than a fiber-free diet. Similarly, daily excretion of total fermentation products was 20 times higher, with an increase of propionate and butyrate proportions. It is estimated that apples could provide 10%–30% of the daily intake of fiber. Using a diet containing 100 g of apple fiber/kg, it has been shown that soluble dietary fiber (SDF) excreted in feces of rats was 10.9% of the SDF ingested, which suggests a low resistance to fermentation of this fraction, while only 43% of the ingested insoluble fiber was fermented. The effects of five DF from different sources (carrot, wheat bran, cocoa seed, pea hull, and oat husks) have been assessed in human microbiota-associated (HMA) rats. HMA rats are initially germ-free rats colonized after weaning with the fecal microbiota of a healthy human volunteer. Use of this animal model is justified by the phylogenetic and metabolic differences between rats and human microbiota and the knowledge that HMA rodents globally retain the characteristics of the human donor microbiota. All of the diets contained 100 g fiber/kg and were given for 8 weeks. Both carrot and cocoa led to a higher proportion of acetate and a lower proportion of propionate in the cecum, and to a large production of methane. The concentration of lactate was significantly higher in rats fed on the carrot-fiber diet.