Effects of difructose anhydride III on calcium absorption in small and large intestines of rats.

Difructose anhydride III (DFA III; di-D-fructo-furanose 1,2':2,3' dianhydride) was prepared from inulin with Arthrobacter sp. H65-7 inulin fructotransferase (depolymerizing (inulase II; EC 2.4.1.93). DFA III is not hydrolyzed by enzymes in the small intestine, but is metabolized by microorganisms in the large intestine. We investigated the effects of DFA III on calcium absorption in two experiments. In the in vivo experiment, we examined the effects of DFA III, fructooligosaccharides, and raffinose on calcium absorption in male Sprague-Dawley rats 5 weeks old at start of the experiment and given feed containing 3% of one of these oligosaccharides for two weeks. The apparent calcium absorption was significantly higher in rats fed any of these oligosaccharides than in control rats, and the increase with DFA III was the greatest. Absorption in both the small and large intestines was affected. In rats fed DFA III, the cecal wall thickened and soluble calcium and the amounts of some organic acids were higher than in the control groups. In an in vitro experiment with everted jejunal and ileal sacs of rats, calcium absorption was higher when DFA III was present in the mucosal fluid at all concentrations tested (up to 200 mM). In the jejunal sacs, the increase in calcium absorption depended on the DFA III concentration. In the ileal sacs, the absorption was maximum at 50 mM DFA III and did not increase further at higher concentrations. These results indicate that intact DFA III stimulates calcium absorption in the small intestine, and that cecal fermentation of DFA III may contribute to the increase in calcium absorption by the large intestine.