Morphometric evidence that YM175, a bisphosphonate, reduces trabecular bone resorption in ovariectomized dogs with dietary calcium restriction.

We examined mechanisms by which incadronate disodium (YM175) prevented bone resorption in ovariectomized dogs with dietary calcium restriction using the morphometrical method. YM175 (0.01-1.0 mg/kg) was given to ovariectomized dogs for 18 months. Because lumbar bone mineral density remained constant at month 17, we assumed that the trabecular bone resorption rate was equal to the bone formation rate and that wall thickness equaled resorption cavity depth. YM175 decreased both the bone resorption rate per number of osteoclasts and resorption cavity depth of cancellous pockets which were increased in ovariectomized dogs. These results suggest that YM175 reduces bone loss by decreasing the resorbing activity of osteoclasts.

Inhibitory effects of YM175, a bisphosphonate, on the progression of experimental periodontitis in beagle dogs.

This study examined the efficacy of YM175 [disodium dihydrogen (cycloheptylamino) methylene-1, 1-bisphosphonate] in reducing alveolar bone loss caused by experimental periodontitis in beagle dogs. Thirty-six dogs were used and divided into 6 groups. Periodontitis was induced in 30 dogs (groups 2-6) by ligating the bilateral mandibular third and fourth premolar teeth with silk ligatures and by feeding a soft diet. Six dogs were sham-operated (group 1). Saline (placebo), flurbiprofen (0.02 mg/kg) and YM175 (0.01, 0.1 and 1.0 mg/kg) were administered to the dogs (groups 2-6) 5 d/wk for 25 wk. Radiographic and morphometric analyses were performed. In placebo-treated animals (group 2), the ligation caused a significant decrease in the alveolar bone height by 0.57 and 1.91 mm at 2 and 25 wk, respectively. YM175 (1.0 mg/kg) prevented the decrease in bone height by 47 and 31% at 2 and 25 wk. YM175 (0.1 mg/kg) and flurbiprofen tended to prevent bone loss after 15 wk. Although the ligation elicited no significant change in bone mineral density, it significantly decreased bone volume. YM175 (1.0 mg/kg) and flurbiprofen tended to increase the bone volume. The number of formative or resorptive Haversian canals and the bone turnover through the periosteal bone surface were increased by the ligation, indicating the increased turnover of the cortical bone. YM175 (1.0 mg/kg) reduced the increased bone turnover. The gingival index was maximally increased at 2 wk and was suppressed by YM175. These results suggest that YM175 prevents alveolar bone loss by reducing the increased alveolar bone turnover in dogs with periodontitis.

Increase of bone mass and mechanical strength in rats after treatment with a novel bisphosphonate, YM175, for two years.

We have evaluated the relationship between bone mass and mechanical properties of bone from male and female rats treated with YM175, a novel bisphosphonate, for 104 weeks. YM175 [disodium (cycloheptylamino) methylenediphosphonate monohydrate] was given via the drinking water at a concentration of 0, 0.005, 0.015, 0.05, or 0.15%. Since the mortality in the male 0.15% group exceeded the exclusion criteria (75%) at week 88, this-group was omitted from the study. Mean daily intake of YM175 was 2.2-22.1 mg/kg for males and 3.6-104 mg/kg for females. After the treatment, mechanical properties and ash weight of the humerus were determined. In males, 0.015 and 0.05% of YM175 (6.6-22.1 mg/kg) significantly increased failure load of the midshaft. In females, failure load and stiffness of the midshaft tended to be increased by YM175 (up to 104 mg/kg). Furthermore, ultimate compressive load at the humeral metaphysis treated with the highest dose of YM175 was 2- or 3.5-fold greater than that of untreated male or female control. Ash weight of the humerus was increased dose-dependently and was positively correlated with failure load of the midshaft. These findings indicate that treatment for 2 years with YM175 increased bone mass and mechanical strength without blocking bone mineralization.

Prevention of bone loss by bisphosphonate YM175 in ovariectomized dogs with dietary calcium restriction.

We have evaluated the effects of YM175 (disodium dihydrogen (cycloheptylamino) methylenebisphosphonate monohydrate), a novel bisphosphonate, on bone mineral densities (BMD) at the lumbar spine and forelimb in ovariectomized beagles with dietary calcium restriction. Groups 1 and 2 were given a sham operation and Groups 3-6 were ovariectomized. One month later (month 0), a low calcium diet was given to Groups 2-6. Groups 4-6 were orally treated with YM175 at doses of 0.01, 0.1 and 1.0 mg/kg, respectively, for 18 months. Changes in BMD at the lumbar spine and left forelimb were determined serially by dual energy X-ray absorptiometry. Calcium restriction decreased lumbar BMD by 19% at month 2 and by up to 30% at month 17 compared to its baseline value, but ovariectomy itself had a minimal effect on bone mass in dogs with restricted calcium intake. YM175 (1 mg/kg) prevented the bone loss at month 2 and YM175 at 0.1 mg/kg or more inhibited the BMD reduction at month 17. The magnitude of BMD reduction of the forelimb was less remarkable as compared to that of the lumbar spine. Urinary hydroxyproline excretion and plasma osteocalcin levels were increased by calcium restriction, indicating a high turnover of bone. YM175 reduced hydroxyproline excretion but not osteocalcin levels. These results indicate that YM175 prevents bone loss induced by calcium restriction and ovariectomy through partially normalizing high bone turnover.

Effects of the bisphosphonate YM175 on bone mineral density, strength, structure, and turnover in ovariectomized beagles on concomitant dietary calcium restriction.

We evaluated the effect of YM175 on bone in ovariectomized beagles fed a calcium-restricted diet for 18 months. Groups 1 (n = 6) and 2 (n = 6) underwent sham operation, and groups 3-6 were ovariectomized at the age of 21 months. Group 1 was fed standard dog chow (calcium: 1.4%), and groups 2-6 were given a low calcium diet (0.14%). Groups 3 (n = 7), 4 (n = 7), 5 (n = 7), and 6 (n = 7) were given YM175 orally at doses of 0, 0.01, 0.1, and 1.0 mg/kg/day, respectively. At the end of the experimental period, bone mineral density values measured in the lumbar (L2) vertebra, the femoral neck, and the midfemur, were reduced in groups 2 and 3. Bone strength, measured by compression tests on L2 body and L3 cancellous core specimens and by bending tests on the femoral neck, also decreased. YM175 treatment dose-dependently increased the values of these parameters. However, the reduction in torsional stiffness in the midfemur was not completely prevented. In the L4 body, trabecular thickness decreased in group 2 and trabecular separation increased in group 3. YM175 treatment prevented these changes, and the values in group 6 were maintained at the same levels as those in group 1. Bone formation rates were increased in groups 2 and 3. YM175 treatment decreased these indices, but the reduction was incomplete even with the highest dose (group 6). These results demonstrate that, in our model, YM175 maintained the mass, structure, and mechanical properties of cancellous bone. Increased bone turnover was not completely prevented by the doses employed, but the balance between net resorption and formation in one remodeling cycle would have been equilibrated by YM175.

Isolation and identification of canine plasma components suspected as uremic toxins.

Suspected uremic substances contained in four fractions, which had been selected as the suspected canine uremic peaks in the previous study, were isolated by two stages of preparative liquid chromatography (PLC) from plasma of uremic dogs treated with the ligation of the ureter, and then their physicochemical properties were examined. The primary separation of the suspected uremic peaks were performed with the same anion exchange resin as used in the analytical HPLC in the previous study. Analytical reverse phase HPLC showed that three of 4 suspected uremic peaks almost consisted of single substances, but the other contained several substances. Main subfractions of these peaks were successfully isolated by the secondary stage reverse phase PLC. By means of thin layer chromatography, ultraviolet absorption spectrometry and proton-nuclear magnetic resonance spectroscopy, components of 4 main peaks were confirmed to be small molecules such as a pyridine derivative, uric acid, hippuric acid and kynurenic acid, respectively.