DIETARY XYLITOL RETARDS THE OVARIECTOMY-INDUCED INCREASE OF BONE TURNOVER IN RATS

The effects of 10% dietary xylitol supplementation in ovariectomized r ats were studied on the degradation of bone organic and inorganic stru ctures. The osseal concentrations of hydroxyproline, pyridinoline, and deoxypyridinoline were analyzed by high-performance liquid chromatogr aphy. Bone resorption was measured in [H-3]tetracycline-prelabeled rat s by urinary excretion of H-3, and by the amount of H-3 preserved in b one. Bone trabeculation was measured by a computer image analyzer from sections stained by the method of von Kossa. The amount of collagen i n bone organic fraction was lower in ovariectomized rats as compared w ith the sham-operated controls. This most likely is partly a consequen ce of an increased resorption, and partly a consequence of a higher pr oportion of immature periosteal bone in the ovariectomized animals, le ading to a higher ratio of noncollagenous protein to collagen. The num ber of pyridinium crosslinks was lower in proportion, indicating no se lective changes in the structure of collagen. Dietary xylitol signific antly retarded the ovariectomy-associated decrease in the relative amo unt of collagen and the number of its mature crosslinks. Ovariectomy d oubled the excretion of H-3 and caused a significant decrease in the a mount of H-3 preserved in bone; both these changes were significantly retarded by the 10% dietary xylitol supplementation. Ovariectomy signi ficantly decreased the volume of bone trabeculae, but this effect was also significantly inhibited by the xylitol supplementation in the die t. In conclusion, these findings suggest a dietary xylitol-induced nor malizing effect on the rate of bone turnover in ovariectomized rats.