Dietary Xylitol Retards the Ovariectomy-Induced Increase of Bone Turnover in Rats

Abstract.

The effects of 10% dietary xylitol supplementation in ovariectomized rats were studied on the degradation of bone organic and inorganic structures. The osseal concentrations of hydroxyproline, pyridinoline, and deoxypyridinoline were analyzed by high-performance liquid chromatography. Bone resorption was measured in [³H]tetracycline-prelabeled rats by urinary excretion of ³H, and by the amount of ³H preserved in bone. Bone trabeculation was measured by a computer image analyzer from sections stained by the method of von Kossa. The amount of collagen in bone organic fraction was lower in ovariectomized rats as compared with the sham-operated controls. This most likely is partly a consequence of an increased resorption, and partly a consequence of a higher proportion of immature periosteal bone in the ovariectomized animals, leading to a higher ratio of noncollagenous protein to collagen. The number of pyridinium crosslinks was lower in proportion, indicating no selective changes in the structure of collagen. Dietary xylitol significantly retarded the ovariectomy-associated decrease in the relative amount of collagen and the number of its mature crosslinks. Ovariectomy doubled the excretion of ³H and caused a significant decrease in the amount of ³H preserved in bone; both these changes were significantly retarded by the 10% dietary xylitol supplementation. Ovariectomy significantly decreased the volume of bone trabeculae, but this effect was also significantly inhibited by the xylitol supplementation in the diet. In conclusion, these findings suggest a dietary xylitol-induced normalizing effect on the rate of bone turnover in ovariectomized rats.