Pauli T. Mattila

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 Youngs 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.

IMPROVED BONE BIOMECHANICAL PROPERTIES IN RATS AFTER ORAL XYLITOL ADMINISTRATION

Abstract. The effects of 5, 10, and 20% dietary xylitol supplementations on the biomechanical properties, histological architecture, and the contents of collagen, pyridinoline, and deoxypyridinoline in long bones of rats were studied. Tibiae were used for the three-point bending test, and femurs were used for the torsion and loading test of the femoral neck. The 10 and 20% oral xylitol administrations caused a significant increase of tibial stress, femoral shear stress, and stress of the femoral neck as compared with the controls. Parallel, but not significant, effects were also seen in the 5% xylitol supplementation group. No significant differences in strain or Youngs modulus of the tibiae were detected between the groups. An increased shear modulus of elasticity in femurs was detected in the 20% supplementation group as compared with the controls. The histomorphometrical data for the secondary spongiosa of the proximal tibia revealed that trabecular bone volume was significantly greater in all dietary xylitol supplementation groups as compared with the controls. The bone volume increased along with increasing xylitol content. No significant differences between the groups were detected concerning the amount of collagen per dry weight of organic matrix, the concentrations of pyridinoline or deoxypyridinoline in collagen, or the ratio of these crosslinks. This suggests no xylitol-dependent selective changes in these structures of bone collagen. In conclusion, dietary xylitol supplementation in rats improves the biomechanical properties of bone and increases the trabecular bone volume dose dependently.

Diminished bone resorption in rats after oral xylitol administration: A dose-response study

The effects of 5, 10, and 20% dietary xylitol supplementations on the resorption of bone were studied. The resorption was measured by the urinary excretion of [3H] radioactivity from [3H]tetracycline-prelabeled rats. The 10 and 20% oral xylitol administrations caused a significant decrease in the excretion of [3H] as compared with the control group with no xylitol supplementation. The effect was detected as early as 2 days after the beginning of xylitol-feeding and was maintained throughout the experimental period of 31 days. The retarding effect on bone resorption was about 25% in the 10% xylitol group, about 40% in the 20% xylitol group, and undetectable in the 5% xylitol group. The amount of preserved [3H] radioactivity in the tibiae of the 10 and 20% xylitol groups after the experiment clearly exceeded the valties of the control group. The mechanism of the retarded bone resorption caused by dietary xylitol still remains obscure, but an increased absorption of calcium may be involved. In conclusion, dietary xylitol supplementation in rats seems to retard the bone resorption in a dose-dependent way. The effect is achieved rapidly and is maintained at least over a period of 1 month xylitol feeding.

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.

Dietary xylitol protects against the imbalance in bone metabolism during the early phase of collagen type II–induced arthritis in dark agouti rats

The aim of the present study was to evaluate the changes in bone metabolism during the early phase of type II collagen-induced arthritis in rats and to evaluate whether a 10% dietary xylitol supplementation is able to protect against these changes. Arthritis was induced in female dark agouti rats by injections of type II homologous rat collagen emulsified with an equal volume of incomplete Freund adjuvant. In one group, the diet was supplemented with 10% xylitol. After 17 days, the rats were killed. Serum osteocalcin, as a marker of bone formation, and serum tartrate-resistant acid phosphatase, as a marker of bone resorption, were measured. Histologic measurements were made from Masson-Goldner trichrome-stained sections of distal tibiae. All the collagen-injected rats had arthritic symptoms at the end of the experiment. Serum osteocalcin was significantly higher in the collagen-injected rats fed a xylitol-supplemented diet (CI-X) than in the collagen-injected rats not fed xylitol (CI) and in the controls. Serum tartrate-resistant acid phosphatase was significantly higher in the CI and CI-X groups than in the controls. Trabecular bone volume was significantly lower in the CI group as compared with the CI-X and control groups. These results suggest that, at the time of the appearance of arthritic symptoms, bone resorption activity is high, but bone formation is not severely affected. Furthermore, dietary xylitol seems to protect against the imbalance of bone metabolism during the early phase of collagen type II-induced arthritis.

Dietary Xylitol Protects Against Osseal Changes in Experimental Osteoporosis

Xylitol is a five-carbon polyalcohol, pentitol, which is widely distributed in nature. Most fruits, berries, and plants contain xylitol, the richest natural sources being plums, strawberries, raspberries, cauliflower, and endives (1). Considerable amounts of xylitol also occur as an intermediate of the mammalian carbohydrate metabolism. In the human body 5–15 grams of xylitol is formed daily (2).