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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.

Our previous studies have shown that dietary xylitol supplementation diminishes bone resorption in rats, as well as protects against ovariectomy-induced increase of bone resorption during experimental osteoporosis. Interestingly, ethanol, when given simultaneously with xylitol, is known to increase blood concentration of xylitol. On the other hand, ethanol, when given alone, has been shown to increase bone resorption. The aim of the present study was to evaluate the effects of a simultaneous dietary administration of 10% xylitol and 10% ethanol on bone resorption. Bone resorption was determined using measurement of urinary excretion of hydrogen 3 (3H) radioactivity in 3H-tetracycline prelabeled rats. Already 4 days after the beginning of dietary supplementations, excretion of 3H was about 15% lower in the xylitol group (diet supplemented with 10% xylitol) and about 25% lower in the xylitol-ethanol group (diet supplemented with 10% xylitol and 10% ethanol) as compared to the controls. The excretion of 3H in these groups remained smaller than that of the controls throughout the entire study period of 40 days. The excretion of 3 H in the xylitol-ethanol group remained also smaller than that of the xylitol group. Bone mineral density and bone mineral content were determined with a peripheral quantitative computed tomography (pQCT) system from the rat tibiae at the end of the experiment. Trabecular bone mineral density and trabecular bone mineral content were significantly greater in the xylitol group and in the xylitol-ethanol group compared to the controls. They were also greater in the xylitol-ethanol group as compared to the xylitol group. Cortical bone mineral density and cortical bone mineral content did not differ significantly between the groups. In conclusion, a simultaneous dietary supplementation with 10% xylitol and 10% ethanol seems to diminish bone resorption and to increase trabecular bone mineral density and trabecular bone mineral content in rats. These effects seem to be stronger than the effects induced by 10% xylitol supplementation alone.

Our previous studies have shown that dietary xylitol protects against weakening of bone biomechanical properties in experimental postmenopausal osteoporosis. To study whether xylitol preserves bone biomechanics also during aging, a long-term experimental study was performed with rats. Twenty-four male Sprague-Dawley rats were divided into 2 groups. The rats in the control group (NON-XYL group) were fed a basal rat and mouse no. 1 maintenance (RM1) diet, while the rats in the experimental group (XYL group) were continuously fed the same diet supplemented with 10% xylitol (wt/wt). The rats were killed after 20 months. Their femurs were prepared for biomechanical analyses and scanning analyses with peripheral quantitative computed tomography (pQCT). In 3-point bending of the femoral diaphysis, maximum load, maximum elastic load, stiffness, energy absorption, elastic energy absorption, ultimate stress, and yield stress were significantly greater in the XYL group than in the NON-XYL group. This indicates a xylitol-induced improvement of both structural and material strength properties of cortical bone. Accordingly, the maximum load of femoral neck was significantly greater in the XYL group. In the pQCT analysis of femoral diaphysis, cortical bone area, cortical thickness (CtTh) periosteal circumference, and cross-sectional moment of inertia were greater in the XYL group. The endosteal circumference was smaller in the XYL group. In the pQCT analysis of the femoral neck cortical area of the midneck was significantly greater in the XYL group. This data indicates that xylitol exerted beneficial effects on the cross-sectional architecture of the bones. In conclusion, continuous moderate dietary xylitol supplementation leads to improved bone biomechanical properties in aged rats concerning both bone structural and material strength properties.

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 Young's 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.

The effects of dietary xylitol (xyl) on bone biomechanical properties in ovariectomized rats (ovx) were studied. Forty-two 3-mo-old female Wistar rats were divided into three groups of 14. Rats in two groups were ovariectomized, while those in the control group underwent a sham operation. All rats received a basal diet, and half of the ovx were given an additional 10 g/100 g dietary xyl supplementation. Three months later the rats were killed and their tibias, femurs and humeri were prepared. The tibias were used for analyses of bone density and trabecular bone volume (BV/TV) and for the three-point bending test. The femurs were used for the torsion test and for the loading test of the femoral neck. The humeri were used for analyses of bone ash weight and bone concentrations of calcium and phosphorus. Dietary xyl gave a significant protection against ovariectomy-caused decline of tibial stress in the three-point bending test, of femoral shear stress in the torsion test, and of stress of the femoral neck, without affecting bone elasticity values. Xyl restricted the ovariectomy-caused reduction in bone density, in bone ash weight and in concentrations of bone calcium and phosphorus. Furthermore, trabecular bone loss in ovx was significantly suppressed by dietary xyl. These results indicate that a 10% dietary supplementation of xyl in ovx has a protective effect against the weakening of bone biomechanical properties. This is related to greater BV/TV and maintained bone mineral content.

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.

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 values 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.

Background Xylitol has antiadhesive effects on Streptococcus pneumoniae and inhibits its growth, and has also been found to be effective in preventing acute otitis media and has been used in intensive care as a valuable source of energy. Results We evaluated the oxidative burst of neutrophils in rats fed with and without xylitol. The mean increase in the percentage of activated neutrophils from the baseline was higher in the xylitol-exposed group than in the control group (58.1% vs 51.4%, P = 0.03 for the difference) and the mean induced increase in the median strength of the burst per neutrophil was similarly higher in the xylitol group (159.6 vs 140.3, P = 0.04). In two pneumococcal sepsis experiments rats were fed either a basal powder diet (control group) or the same diet supplemented with 10% or 20% xylitol and infected with an intraperitoneal inoculation of S. pneumoniae after two weeks. The mean survival time was 48 hours in the xylitol groups and 34 hours in the control groups (P < 0.001 in log rank test). Conclusion Xylitol has beneficial effects on both the oxidative killing of bacteria in neutrophilic leucocytes and on the survival of rats with experimental pneumococcal sepsis.

Background: Dietary xylitol has been shown to increase the amounts of newly synthesized collagen, and to decrease fluorescence of the collagenase-soluble fraction in the skin of both healthy and diabetic rats. As in diabetic rats, a decreased rate of collagen synthesis and increased collagen fluorescence has also been detected in the skin of aged rats. We hypothesize that dietary xylitol supplementation may protect against these changes during aging. Objective: The purpose of the present study was to investigate whether a long-term dietary supplementation can protect against the decrease in the amounts of newly synthesized collagen, and against the increase in fluorescence in the collagenase-soluble fraction in the skin of aged rats. Methods:Twenty-four male Sprague-Dawley rats were used in the study. After weaning, the rats were divided into 2 groups of 12 animals. The rats in the control group were fed a basal RM1 diet, while the rats in the experimental group were fed the same diet supplemented with 10% xylitol. After 20 months, the rats were killed and pieces of skin from their dorsal areas were excised. The thickness of the samples was measured with a micrometer screw gauge. The collagen contents of rat skin were measured as hydroxyproline, and glycosylation as fluorescent intensity of collagen. Statistical significances of the differences between the groups were determined using the unpaired t test. Results: No general side effects were detected in the rats during the experimental period. The skin of the xylitol-fed rats was a little thicker than that of the control rats. The hydroxyproline content of the acid-soluble fraction was significantly greater in the xylitol group as compared to the controls. However, there were no significant differences in the hydroxyproline content of the collagenase-soluble fraction between the groups. The fluorescence of the collagenase-soluble fraction was significantly smaller in the xylitol-fed aged rats than in the aged rats fed the basal diet. Conclusions: The results of this study indicate that xylitol caused an increase in the amount of newly synthesized collagen and a decrease in collagen fluorescence in the skin of aged rats.

Background: Our previous studies have shown that dietary xylitol supplementation protects against the loss of bone mineral after ovariectomy. The ovariectomy-induced decrease in trabecular bone volume is significantly retarded by dietary xylitol. Objective: To study whether dietary xylitol can protect against bone loss also during aging, a long-term experimental study was performed with rats. Methods: Twenty-four male Sprague-Dawley rats were divided into two groups. The rats in the control group were fed a basal RM1 diet, while the rats in the experimental group were continuously fed the same diet supplemented with 10% (w/w) xylitol. The rats were killed after 20 months. Their tibiae were used for the analyses of bone density and trabecular bone volume, and their femurs were used for the scanning analyses with peripheral quantitative computed tomography (pQCT). Results: The tibial density of the xylitol-fed aged group (1.73 ± 0.14 g/mm3) was significantly greater than that of the aged group without xylitol (1.56 ± 0.14 g/ mm3). The trabecular bone volume of the xylitol-fed rats was 21.2 ± 4.0%. It was significantly greater than that of the rats not receiving xylitol (9.3 ± 4.3%). The pQCT-measured cortical bone mineral density and the pQTC-measured cortical bone mineral content of the femoral diaphysis were significantly greater in the xylitol-fed group than in the control group. The trabecular bone mineral density and the trabecular bone mineral content of the femoral distal metaphysis were also significantly greater in the xylitol-fed group than in the non-xylitol group. The total bone mineral density and the total bone mineral content of the femoral neck in the xylitol-fed aged group significantly exceeded those in the aged group without xylitol supplementation. Conclusions: A continuous moderate dietary xylitol supplementation leads to increased bone volume and increased bone mineral content in the long bones of aged rats. This indicates a xylitol-induced protection against aging-related osteoporotic changes.

The effects of three-month dietary xylitol supplementation on the amounts and hexose contents of acid-soluble collagen as well as on the amounts and fluorescence of collagenase-soluble collagen were studied in healthy and streptozotocin-diabetic male rats. Collagen was extracted from skin samples. In the healthy rats, supplementation with xylitol (10%) increased the hydroxyproline content of the acid-soluble fraction and skin thickness. In diabetic rats receiving and not receiving xylitol, the acid-soluble collagen fraction was markedly lower than in healthy rats. However, its amount was significantly elevated when xylitol had been added to the diet. Supplementation with xylitol caused no changes in the amounts of collagenase-soluble fraction in either healthy or diabetic rats. Supplementation with xylitol (10%) significantly decreased the hexose content of acid-soluble collagen and the fluorescence of the collagenase-soluble fraction in both healthy and diabetic rats. The results indicate that dietary xylitol affects collagen synthesis and collagen glycosylation.

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).

A xylitol-induced reduction in dentin formation has been observed in molars of post-weanling rats, but the effect in older animals with a slower rate of secondary dentinogenesis has not been investigated. We examined the effects of different concentrations of dietary xylitol on dentinogenesis in molars of young adult rats. The control group received a commercial basal diet, while for the other 3 groups, the same diet was supplemented with 5, 10 and 20% of xylitol. After 8 weeks, dentin thickness beneath the main fissures in the mandibular 1st and 2nd molars was measured. The final body weights did not differ between the groups. Dentin formation in the 1st molars of the 10 and 20% xylitol groups was significantly lower as compared to the controls, whereas no difference was found between these 2 groups. In conclusion, dietary xylitol reduces dentin formation in young adult rats in spite of the slow rate of dentinogenesis.