Dietary xylitol supplementation prevents osteoporotic changes in streptozotocin-diabetic rats

The effects of 10% and 20% dietary xylitol supplementation on the biomechanical properties, trabeculation, and mineral content of long bones were studied in streptozotocin-diabetic rats. Forty 3-month-old male Wistar rats were divided randomly into four groups of 10. Rats in three groups were administered a single injection of streptozotocin (50 mg/kg body weight) to induce type I diabetes, while animals in the fourth group were given a sham injection of physiological saline. The sham-injected group and one of the streptozotocin-diabetic groups were fed the basal diet, while the two diabetic groups were fed the same diet supplemented with 10% and 20% xylitol (wt/wt). After 3 months, the rats were killed and the long bones were prepared for analysis. The 10% and 20% dietary xylitol supplementation significantly prevented the type I diabetes-induced decrease in the mechanical stress resistance of the tibia in the three-point bending test, the shear stress of the femur in the torsion test, and the stress resistance of the femoral neck in the loading test. No statistically significant differences were found between any groups in the values for strain or Young's modulus in the three-point bending test, or in the values for the shear modulus of elasticity in the torsion test. These findings indicate that dietary xylitol protects against the weakening of the bone strength properties of both cortical and trabecular bone without affecting the elastic-plastic properties. Supplementation with 10% and 20% dietary xylitol significantly prevented the type I diabetes-induced decrease of humeral ash weight and tibial density. Histomorphometric data for the secondary spongiosa of the proximal tibia showed that 10% and 20% dietary xylitol supplementation also significantly prevented the type I diabetes-induced loss of trabecular bone volume. In conclusion, dietary xylitol supplementation protects against the weakening of bone biomechanical properties in streptozotocin-diabetic rats. This is related to the preserved bone mineral content and preserved trabecular bone volume. Copyright (C) 1998 by W.B. Saunders Company.