DIETARY XYLITOL SUPPLEMENTATION PREVENTS OSTEOPOROTIC CHANGES IN STREPTOZOTOCIN-DIABETIC RATS

The effects of 10% and 20% dietary xylitol supplementation on the biom echanical 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 thre e groups were administered a single injection of streptozotocin (50 mg /kg body weight) to induce type I diabetes, while animals in the fourt h 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 s upplemented with 10% and 20% xylitol (wt/wt). After 3 months, the rats were killed and the long bones were prepared for analysis. The 10% an d 20% dietary xylitol supplementation significantly prevented the type I diabetes-induced decrease in the mechanical stress resistance of th e 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 e lasticity in the torsion test. These findings indicate that dietary xy litol protects against the weakening of the bone strength properties o f both cortical and trabecular bone without affecting the elastic-plas tic properties. Supplementation with 10% and 20% dietary xylitol signi ficantly prevented the type I diabetes-induced decrease of humeral ash weight and tibial density. Histomorphometric data for the secondary s pongiosa of the proximal tibia showed that 10% and 20% dietary xylitol supplementation also significantly prevented the type I diabetes-indu ced loss of trabecular bone volume. In conclusion, dietary xylitol sup plementation protects against the weakening of bone biomechanical prop erties in streptozotocin-diabetic rats. This is related to the preserv ed bone mineral content and preserved trabecular bone volume. Copyrigh t (C) 1998 by W.B. Saunders Company.