The Colonic Bacteria and Rates of Small Intestinal Nutrient Transport of Mice Fed Diets with Inulin and Oligofructose

The densities and metabolic characteristics of the gastrointestinal tract bacteria are responsive to dietary supplements of nondigestible oligosaccharides (NDO), but little is known about the influences on the small intestine. Therefore, the colonic bacteria and the dimensions and transport functions of the small intestine were compared among mice (B6C 3F1 strain) fed diets with 10% cellulose (control) or with the cellulose replaced entirely with the NDO inulin or oligofructose or partially (2.5% oligofructose and 7.5% cellulose). Mice fed diets with 10% inulin or oligofructose had higher densities of anaerobes, aerobes, bacteroides, and lactobacilli, and lower proportions of enterics than mice fed a diet with 10% cellulose. Inulin, but not oligofructose, resulted in higher densities of streptococci. The small intestine was longer and weighed more when mice were fed 10% inulin with intermediate values for 10% oligofructose. Relative to control mice, rates of glucose transport and absorption of leucine, proline and glycyl-sarcosine (nmol/mg-min) were lower when mice were fed diets with 10%oligofructose and inulin, whereas only leucine was lower when mice were fed the diet with 2.5% oligofructose. Our findings indicate supplementing diets with the NDO oligofructose and inulin 1) change the assemblages of colonic bacteria, 2) influence the dimensions and absorptive functions of the small intestine, and 3) may be useful for managing the gastrointestinal ecosystem, but 4) the specific responses vary among the types and amounts of NDO and among animal models.