Do Different Aminobisphosphonates Have Similar Preventive Effect on Experimental Thyroid Hormone-Induced Osteopenia in Rats?

We compared similar doses of three different aminobisphosphonates (BP): olpadronate (OPD), pamidronate (APD), and alendronate (ALE) on osteopenia induced by thyroxine (T4)-treatment in OVX and SHAM adult rats. Female Sprague Dawley rats (259 +/- 8 g) were treated with vehicle (SHAM+Vh and OVX+Vh), 250 microg T4/kg/day (SHAM+T4 and OVX+T4), 0.3 mg OPD/kg/day (SHAM+OPD and OVX+OPD), 0.2 mg ALE/kg/day (SHAM+ALE and OVX+ALE), 1.5 mg APD/kg/day (SHAM+APD and OVX+APD), T4+OPD (SHAM+T4+OPD and OVX+T4+OPD), T4+ALE (SHAM+T4+ALE and OVX+T4+ALE), and T4 +APD (SHAM+T4+APD and OVX+T4+APD) during a 5-week period. At the onset and at the end of the experiment, total skeleton bone mineral density (BMD) was assessed in vivo by DXA. Lumbar spine and proximal tibia BMDs were evaluated. T4 treatment to SHAM rats did not modify BGP levels significantly: neither did ovariectomy. T4 treatment to OVX rats significantly increased bone-gla-protein (BGP) levels compared with the other studied groups (P < 0.05). BP treatment reduced BGP levels to values significantly lower than SHAM rats (P < 0.05) and reduced bone alkaline phosphatase in SHAM groups (P < 0.05) but no changes were found in OVX groups. The increased D-Pyr excretion observed in SHAM+T4 rats (P = 0.056), OVX+Vh (P < 0.05), and OVX+T4 group (P < 0.001) compared with the SHAM+Vh rats was prevented by the BP treatment. OVX+Vh rats had total skeleton and proximal tibia BMD, and OVX+T4 group had total skeleton, spine, and proximal tibia BMD significantly lower than the SHAM+Vh group. BP treatment was also found to prevent this reduction. The reduced bone resorption and the prevention of bone loss showed no differences among very close, potentially equivalent doses of the three aminoBPs used. Consequently, treatment with very close similar doses of APD, ODP, and ALE prevented bone resorption and bone changes with the same efficacy.     

Long-term dosing of arzoxifene lowers cholesterol, reduces bone turnover, and preserves bone quality in ovariectomized rats.

Long-term effects of a new selective estrogen receptor modulator (SERM) arzoxifene were examined in ovariectomized (OVX) rats. Arzoxifene was administered postoperatively (po) at 0.1 mg/kg per day or 0.5 mg/kg per day to 4-month-old rats, starting 1 week after OVX for 12 months. At study termination, body weights for arzoxifene groups were 16-17% lower than OVX control, which was caused by mainly reduced gain of fat mass. Longitudinal analysis of the proximal tibial metaphysis (PTM) by computed tomography (CT) at 0, 2, 4, 6,9, and 12 months showed that OVX induced a 22% reduction in bone mineral density (BMD) at 2 months, which narrowed to a 12% difference between sham-operated (sham) and OVX rats by 12 months. Both doses of arzoxifene prevented the OVX-induced decline in BMD. Histomorphometry of the PTM showed that arzoxifene prevented bone loss by reducing osteoclast number in OVX rats. Arzoxifene maintained bone formation indices at sham levels and preserved trabecular number above OVX controls. Micro-CT analysis of lumbar vertebrae showed similar preservation of BMD compared with OVX, which were not different from sham. Compression testing of the vertebra and three-point bending testing of femoral shaft showed that strength and toughness were higher for arzoxifene-treated animals compared with OVX animals. Arzoxifene reduced serum cholesterol by 44-59% compared with OVX. Uteri wet weight from arzoxifene animals was 38-40% of sham compared with OVX rats, which were 29% of sham. Histology of the uterine endometrium showed that cell heights from both doses of arzoxifene were not significantly different from OVX controls. In summary, treatment of OVX rats with arzoxifene for nearly one-half of a lifetime maintained beneficial effects on cholesterol and the skeleton. These data suggest that arzoxifene may be a useful therapeutic agent for osteoporosis in postmenopausal women.     

Effect of 16 months of treatment with tibolone on bone mass, turnover, and biomechanical quality in mature ovariectomized rats.

Tibolone (Org OD14) is a tissue-specific steroid with estrogenic effects on the bone and vagina but not endometrium or breast and has been shown to prevent ovariectomy-induced bone loss in young and old rats. We evaluated the effect of long-term tibolone treatment on bone parameters in mature ovariectomized (OVX) rats. Six-month-old rats were allotted to one of six groups (n = 8). Sham-operated and control OVX groups received vehicle, whereas other groups (all OVX) received tibolone (125, 250, or 500 microg/day orally) or 17alpha-ethinylestradiol (EE; 24 microg/day orally) for 16 months. Treatment with tibolone prevented ovariectomy-induced bone loss in peripheral (femur and tibia) and axial (L1-L2 and L4) skeleton. In peripheral skeleton, tibolone and EE prevented loss of bone mass and quality to a similar extent. Tibolone dose-dependently inhibited trabecular bone volume loss in L1-L2 and tibia, and at 500 microg/day it inhibited 88% of L1-L2 and 55% of tibial volume loss (p < or = 0.05 in each case). Tibolone, 500 microg, resulted in 10% greater cortical strength of femur (p < or = 0.05) and 60% greater compressive strength of L4 (p < or = 0.05) compared with vehicle-treated OVX rats. Tibolone and EE inhibited bone resorption and turnover, assessed by urinary deoxypyridinoline/ creatinine and plasma osteocalcin, respectively. We conclude that 16 months of tibolone treatment prevents ovariectomy-induced deterioration of axial and peripheral skeleton and preserves cortical and trabecular bone strength by reducing bone resorption.     

Prevention of bone loss in ovariectomized rats by combined treatment with risedronate and 1alpha,25-dihydroxyvitamin D3.

Bisphosphonates inhibit bone loss through inhibition of osteoclast-mediated bone resorption. At low doses, vitamin D metabolites can prevent bone loss in models of osteopenia in rats by an antiresorptive effect, while at high doses they also stimulate osteoblast activity and show an anabolic effect. Therefore, combined therapy with bisphosphonates and vitamin D analogs might be expected to be more effective than either treatment alone. It was the aim of this study to compare the efficacy of risedronate and of the naturally occurring vitamin D hormone 1alpha,25-dihydroxyvitamin D3 (calcitriol), alone and in combination, for the prevention of ovariectomy-induced bone loss in rats. One hundred ten female 4-month-old Sprague-Dawley rats were used for this experiment. Ninety rats were bilaterally ovariectomized (OVX), 10 rats were sham-operated (SHAM), and 10 rats were killed at the time of surgery as a baseline control. Groups of rats (10 rats/group) received vehicle or daily doses of 0.1 mg or 0.5 mg of risedronate or 0.05 microg or 0.1 microg of calcitriol/kg body weight, alone and in combination. Both compounds were administered orally via gavage, commencing on the day after surgery. Although estrogen deficiency-induced bone loss was prevented by individual prophylactic administration of risedronate or calcitriol, OVX rats treated with a combination of risedronate and calcitriol had higher bone mineral density (BMD), cancellous bone area (B.Ar), and bone strength in long bones and vertebrae compared with rats receiving risedronate alone. Furthermore, calcitriol enhanced the suppressive effects of risedronate on osteoclast number and partially counteracted the suppressive effects of risedronate on bone formation and histomorphometric indices of osteoblast team performance. Risedronate did not reduce the anabolic effect of calcitriol, and at the high dose it normalized hypercalcemia in calcitriol-treated OVX rats. Therefore, this study in OVX rats suggests that combined therapy with bisphosphonates and vitamin D analogs may offer advantages over the treatment with bisphosphonates or vitamin D analogs alone.     

The Phytoestrogen Genistein Reduces Bone Loss in Short-Term Ovariectomized Rats

The incidence of fractures and of osteoporosis differs between Oriental and Western Caucasian women. This may depend, at least in part, on nutritional factors, including dissimilarities in dietary intake of phytoestrogens. To investigate this possibility, 2-month-old female rats were ovariectomized (OVX) or sham-operated (SHAM), fed a casein-based diet, injected daily with subcutaneous genistein (GEN), the most abundant and best characterized phytoestrogen, or vehicle (Veh) and killed 21 days after surgery. As expected, ovariectomy resulted in loss of bone mineral density (BMD) and in uterine atrophy. However, administration of 5 mg GEN per gram body weight (b.w.) ameliorated the ovariectomy-induced loss of BMD (189 ± 2 mg/cm² in OVX and 192 ± 2 in OVX with 5 mg GEN/g b.w. per day; p<0.05). One microgram GEN per gram body weight did not affect the BMD loss and the effect of the 5 mg and 25 mg GEN per gram body weight were statistically not different. A trend toward reduced uterine atrophy (21% reduction) was noted with the 25 mg GEN dose, but not with the 1 mg and 5 mg doses. A separate experiment with 2 x 2 factorial design was conducted to elucidate the mechanism by which GEN ameliorates ovariectomy-induced bone loss. In this experiment, histomorphometry demonstrated a dramatic reduction in trabecular bone volume after ovariectomy (7.6 ± 0.7% of total bone volume in SHAM-Veh vs 3.3 ± 0.2% in OVX-Veh; p<0.01) and less bone loss in OVX rats injected with 5 mg GEN per gram per day (3.3 ± 0.2% of total bone volume in OVX-Veh vs 5.2 ± 0.4% in OVX-GEN; p<0.01). Administration of GEN was associated with higher bone formation rate per tissue volume and with a trend toward a higher number of osteoblasts per bone perimeter. The parameters of bone resorption were not affected by GEN. The concentration of serum osteocalcin and the urinary excretion of deoxypyridinoline provided corroborating results. Since production of proinflammatory cytokines is intimately involved in the pathogenesis of postmenopausal osteoporosis, the effect of GEN on lipopolysaccharide-induced in vitro production of Tumor necrosis factor-alpha (TNFa) was tested in monocytic cells from the same four rat groups. Production of TNFa was markedly elevated in OVX-Veh as compared with the SHAM-Veh rats, but this was blocked by GEN in the OVX rats. This study shows that GEN reduces both trabecular and compact bone loss after ovariectomy and that this protective effect differs from that of estrogen, since it depends on stimulation of bone formation rather than on suppression of bone resorption. Lack of action of GEN on uterine atrophy supports the possibility that this GEN dose affects target tissues via non-estrogenic mechanisms. Modulation of cytokine production may be involved in the effect of GEN on bone. Received: 27 June 1997 / Accepted: 27 October 1997     

Long-term minodronic acid (ONO-5920/YM529) treatment suppresses increased bone turnover, plus prevents reduction in bone mass and bone strength in ovariectomized rats with established osteopenia

The present study examined the effect of the highly potent nitrogen-containing bisphosphonate, minodronic acid (ONO-5920/YM529), on bone mineral density (BMD), bone turnover, bone histomorphometry and bone strength in ovariectomized (OVX) rats. Female F344/DuCrj rats, aged 14 weeks, were OVX or sham operated. After 3 months, the OVX rats showed an increase in bone turnover, and a decrease in bone mass and bone strength. Minodronic acid was administered orally once a day for 12 months at doses of 0, 0.006, 0.03 and 0.15 mg/kg from 3 months after OVX. Minodronic acid dose-dependently inhibited the decrease in BMD of lumbar vertebrae and femur. In the femur, treatment with 0.15 mg/kg minodronic acid increased the BMD of distal and mid sites to sham levels. Minodronic acid dose-dependently suppressed OVX-induced increase in urinary deoxypyridinoline, a bone resorption marker, after a month of treatment and these effects were maintained for 12 months of treatment. Minodronic acid also decreased serum osteocalcin, a bone formation marker. In bone histomorphometric analysis after 12 months of treatment, OVX rats showed an increase in bone resorption (Oc.S/BS and N.Oc/BS) and bone formation (MS/BS and BFR/BV) at lumbar vertebral bodies. Minodronic acid suppressed the OVX-induced increase in bone turnover at tissue level. Trabecular bone volume, trabecular thickness and trabecular number of lumbar vertebral bodies were decreased after OVX. Minodronic acid increased these structural indices, indicating that it prevented the deterioration in trabecular architecture. In a mechanical test at 12 months of treatment, ultimate load of lumbar vertebral bodies and mid femur in the OVX-control group was decreased compared to the sham group. Minodronic acid prevented the reduction in bone strength at both sites. In particular, in the mid femur, treatment with 0.03 and 0.15 mg/kg minodronic acid increased bone strength to sham levels or greater. In conclusion, minodronic acid suppressed increased bone turnover, plus prevented the decrease in BMD, deterioration of bone microarchitecture and reduction in bone strength in OVX rats with established osteopenia. These results suggest that minodronic acid may be clinically useful for treatment of osteoporosis.     

A new selective estrogen receptor modulator, CHF 4227.01, preserves bone mass and microarchitecture in ovariectomized rats.

A new SERM, CHF 4227.01, given to 6-month-old female rats immediately after ovariectomy, preserved bone mass and bone microarchitecture without affecting uterus weight. It also decreased serum cholesterol and fat mass in estrogen-deficient rats. INTRODUCTION: We tested the effect of a new benzopyran derivative, CHF 4227.01, with selective estrogen receptor modulator (SERM) activity on bone mass and biomechanics in ovariectomized (OVX) female rats in comparison with 17alpha-ethinylestradiol (EST), raloxifene (RLX), and lasofoxifene (LFX). MATERIALS AND METHODS: Four doses of CHF 4227.01 (0.001, 0.01, 0.1, and 1 mg/kg body weight [bw]/day) were administered in OVX animals daily by gavage 5 days/week for 4 months. EST was administered at a dose of 0.1 mg/kg bw/day, whereas RLX and LSX were administered at doses of 1 and 0.1 mg/kg bw/day, respectively, by gavage. In one group (Sham), rats were operated but the ovaries not removed; another OVX group was treated only with placebo. RESULTS AND CONCLUSIONS: Treatment with CHF 4227.01 (1.0 and 0.1 mg/kg bw), EST (0.1 mg/kg bw), LFX (0.1 mg/kg bw), or RLX (1.0 mg/kg bw) prevented bone loss on the lumbar spine and the proximal femur assessed in vivo by DXA. Volumetric BMD obtained by pQCT ex vivo confirmed protection from bone loss in the spine and proximal femur among rats treated with CHF 4227.01. This effect was associated with strong inhibition of bone resorption both histologically and biochemically. Furthermore, CHF 4227.01 preserved trabecular microarchitecture, analyzed by muCT, and maintained biomechanical indices of bone strength in the spine and proximal femur, effects also observed for RLX, whereas LSX was less protective of microarchitecture. CHF 4227.01 treatment did not affect uterine weight, prevented the increase in body weight and fat mass seen in OVX animals, and decreased serum cholesterol to below the average of intact animals. In conclusion, CHF 4227.01 exhibits a promising therapeutic and safety profile as a new SERM on both skeletal and extraskeletal outcomes.     

A nonprostanoid EP4 receptor selective prostaglandin E2 agonist restores bone mass and strength in aged, ovariectomized rats.

CP432 is a newly discovered, nonprostanoid EP4 receptor selective prostaglandin E2 agonist. CP432 stimulates trabecular and cortical bone formation and restores bone mass and bone strength in aged ovariectomized rats with established osteopenia. INTRODUCTION: The purpose of this study was to determine whether a newly discovered, nonprostanoid EP4 receptor selective prostaglandin E2 (PGE2) agonist, CP432, could produce bone anabolic effects in aged, ovariectomized (OVX) rats with established osteopenia. MATERIALS AND METHODS: CP432 at 0.3, 1, or 3 mg/kg/day was given for 6 weeks by subcutaneous injection to 12-month-old rats that had been OVX for 8.5 months. The effects on bone mass, bone formation, bone resorption, and bone strength were determined. RESULTS: Total femoral BMD increased significantly in OVX rats treated with CP432 at all doses. CP432 completely restored trabecular bone volume of the third lumbar vertebral body accompanied with a dose-dependent decrease in osteoclast number and osteoclast surface and a dose-dependent increase in mineralizing surface, mineral apposition rate, and bone formation rate-tissue reference in OVX rats. CP432 at 1 and 3 mg/kg/day significantly increased total tissue area, cortical bone area, and periosteal and endocortical bone formation in the tibial shafts compared with both sham and OVX controls. CP432 at all doses significantly and dose-dependently increased ultimate strength in the fifth lumber vertebral body compared with both sham and OVX controls. At 1 and 3 mg/kg/day, CP432 significantly increased maximal load in a three-point bending test of femoral shaft compared with both sham and OVX controls. CONCLUSIONS: CP432 completely restored trabecular and cortical bone mass and strength in established osteopenic, aged OVX rats by stimulating bone formation and inhibiting bone resorption on trabecular and cortical surfaces.     

The New Selective Estrogen Receptor Modulator MDL 103,323 Increases Bone Mineral Density and Bone Strength in Adult Ovariectomized Rats

Selective estrogen receptor modulators (SERMs) can prevent the bone loss induced by ovariectomy (OVX), but it is not established whether they can increase bone mass and strength in a curative protocol in ovariectomized osteopenic animals. We investigated the influence of a SERM of the new generation, MDL 103,323, on areal bone mineral density (BMD), as measured by dual-energy X-ray absorptiometry, bone strength and remodeling in OVX osteopenic rats. Nine weeks after OVX, 8-month-old rats were divided into six groups of 10 animals. MDL 103,323 was given by gavage at doses of 0.01, 0.1 or 0.6 mg/kg body weight, 5 days a week. The effect of MDL 103,323 was compared with that of the bisphosphonate pamidronate (APD), which was injected subcutaneously at a dose of 1.6 mmol/kg body weight for 5 days every 4 weeks. Lumbar spine (LS), femoral neck (FN), proximal tibia (PT) and midshaft tibia (MT) BMD, bone strength, and proximal tibia histomorphometry, serum osteocalcin, urinary total deoxypyridinoline and serum insulin-like growth factor I (IGF-I) were measured. After 16 weeks of treatment, BMD changes (means ± SEM) were −11.4 ± 2.2, +4.0 ± 2.1 and +6.4 ± 1.0% respectively in OVX controls, in rats treated with 0.1 mg/kg MDL 103,323 (p<0.05) and in APD-treated rats (p<0.02) at the level of LS; −0.4 ± 1.1, +6.7 ± 1.4, +7.2 ± 1.8% (p<0.01 and NS) at the level of FN; and −2.6 ± 1.2%, +5.8 ± 1.2, +6.9 ± 1.4% (p<0.03 and 0.01) at the level of PT. MDL 103,323-treated animals had a higher trabecular bone volume, a higher number of trabeculae and smaller intertrabecular spaces compared with OVX controls. Vertebral body ultimate strength was 186 ± 13, 292 ± 16, 249 ± 23 N (p<0.05) in OVX controls, MDL 103,323-treated rats and APD-treated rats, respectively. The administration of 0.6 mg/kg of MDL 103,323 did not further increase BMD or bone strength, indicating a bell-shaped dose–response curve. MDL 103,323 lowered plasma osteocalcin concentration and urinary deoxypyridinoline excretion. In rats treated with 0.1 mg/kg MDL 103,323, plasma IGF-I was increased as compared with OVX controls (664 ± 36 ng/ml vs 527 ± 39 ng/ml, p<0.05). In conclusion, these results indicate that this new SERM positively influences BMD and lumbar spine bone strength in estrogen-deficient rats. Received: 30 October 1998 / Accepted: 12 April 1999     

Du-Zhong (Eucommia ulmoides Oliv.) cortex extract prevent OVX-induced osteoporosis in rats

Du-Zhong, rich in polyphenolic compounds such as lignans, phenolic acid, and flavonoids, is a kidney-tonifying herbal medicine with a long history of safe use for treatment of bone fractures and joint diseases in China. In the present study, we examined whether Du-Zhong cortex extract (DZCE) with graded doses exerted its preventive effects on estrogen deficiency-induced osteoporosis. Eighty 3-month-old female Sprague-Dawley rats were used and randomly assigned into sham-operated group (Sham) and five ovariectomy (OVX) subgroups, i.e. OVX with vehicle (OVX); OVX with 17alpha-ethinylestradiol (E(2), 25 microg/kg/day); OVX with DZCE of graded doses (100, 300, or 500 mg/kg/day). Daily oral administration of DZCE or E(2) started on week 4 after OVX for 16 weeks. Treatment with DZCE at higher doses (300 or 500 mg/kg/day) was found to be able to significantly prevent OVX-induced decrease in biomechanical quality of femur such as maximum stress and Young's modulus. The mechanical changes were associated with the prevention of a further bone mineral density (BMD) decrease or even with some improvements in microarchitecture. DZCE dose-dependently inhibited total BMD decrease in the femur caused by OVX, which was accompanied by a significant decrease in skeletal remodeling, as was evidenced by the decreased levels of the bone turnover markers osteocalcin (OC), alkaline phosphatese (ALP), deoxypyridinoline (DPD), and urinary Ca and P excretions. muCT analysis of the femoral metaphysis showed that DZCE at the highest doses (500 mg/kg/day) significantly prevents decrease in bone volume/tissue volume (BV/TV), connect density (Conn.D), trabecula number (Tb.N) and trabecula thickness (Tb.Th), and increase in trabecula separation (Tb.Sp) and structure model index (SMI) in OVX rats. We conclude that 16 weeks of DZCE treatment improves bone biomechanical quality through modifications of BMD, and trabecular microarchitecture without hyperplastic effect on uterus, and it might be a potential alternative medicine for treatment of postmenopausal osteoporosis.     

The effects of clodronate on increased bone turnover and bone loss due to ovariectomy in rats

The present study was carried out to investigate the ability of clodronate to inhibit ovariectomy-induced bone loss and increased bone turnover in rats. Estradiol was administered as a reference compound. Seventy Sprague-Dawley rats were ovariectomized (OVX) or sham-operated (Sham) at the age of 90 days and divided into seven groups. Two Sham and two OVX groups received subcutaneously either the vehicle of clodronate or the vehicle of estradiol. Other OVX groups were given s.c. either disodium clodronate at two dose levels (5 mg/kg or 12.5 mg/kg twice a week) or 17β-estradiol (10 μg/kg five times a week) for 8 weeks. Femur length, volume, dry weight, and ash weight were determined, and proximal ends of tibiae were used for bone histomorphometry. Markers of bone metabolism were measured from urine and serum. A significant loss of 54% of trabecular bone area of proximal tibial metaphysis was found at 8 weeks after ovariectomy. Clodronate and estradiol inhibited (p < 0.001) this osteopenia. Both drugs prevented the decrease in ash weight/volume of the femur. The inhibitory effect of clodronate and estradiol on bone resorption in OVX rats could be detected also in decreased urinary excretion of hydroxyproline and lysylpyridinoline (p < 0.001). Clodronate and estradiol decreased (p < 0.001) the ovariectomy-induced enhanced tibial endocortical mineral apposition rate (Ec.MAR) on the lateral cortex to the level of the Sham group. In contrast, periosteal MAR analyzed on the medial side of tibial cortical bone did not change significantly in the OVX/Veh group. Estradiol decreased periosteal MAR to below the level in the Sham group (p < 0.01). These results suggest that ovariectomy of growing rats resulted in tibial and femoral osteopenia two months later. Clodronate as well as estradiol can suppress bone resorption and turnover in ovariectomized rats, inhibiting the development of osteopenia. Both clodronate doses (5 and 12.5 mg/kg) had beneficial effects in ovariectomized animals.     

Strontium ranelate improves bone strength in ovariectomized rat by positively influencing bone resistance determinants

Summary  Treatment of adult ovariectomized (OVX) rats with strontium ranelate prevented vertebral biomechanics degradation as a result of the prevention of bone loss and micro-architecture deterioration associated to an effect on intrinsic bone material quality. Strontium ranelate influenced the determinants of bone strength by prevention of ovariectomy-induced changes which contribute to explain strontium ranelate antifracture efficacy. Introduction  Strontium ranelate effects on the determinants of bone strength in OVX rats were evaluated. Methods  Adult female Sprague–Dawley rats were OVX, then treated daily for 52 weeks with 125, 250, or 625 mg strontium ranelate/kg. Bone strength, mass, micro-architecture, turnover, and intrinsic quality were assessed. Results  Strontium ranelate prevented ovariectomy-induced deterioration in mechanical properties with energy necessary for fracture completely maintained vs. SHAM at 625 mg/kg/day, which corresponds to the clinical dose. This was related to a dose-dependent effect on bone volume, higher trabeculae number, and lower trabecular separation in strontium ranelate vs. OVX. Load and energy required to induce lamella deformation were higher with strontium ranelate than in OVX and in SHAM, indicating that the bone formed with strontium ranelate is able to withstand greater damage before fracture. Bone formation was maintained high or even increased in strontium ranelate as shown by mineralizing surfaces and alkaline phosphatase while strontium ranelate led to reductions in deoxypyridinoline. Conclusion  Strontium ranelate administered at 625 mg/kg/day for 52 weeks prevented OVX-induced biomechanical properties deterioration by influencing the determinants of bone strength: it prevented bone loss and micro-architecture degradation in association with an effect on intrinsic bone quality. These beneficial effects on bone contribute to explain strontium ranelate antifracture efficacy.     

Bone response to treatment with lower doses of conjugated estrogens with and without medroxyprogesterone acetate in early postmenopausal women

Lower doses of conjugated estrogens (CE) alone or combined with lower doses of medroxyprogesterone acetate (MPA) increase mean bone mineral density (BMD) from baseline at the spine and hip in early postmenopausal women. However, not all women on therapy gain BMD. The incidence of continued bone loss (defined as a loss of BMD of >2% from baseline) among women using lower doses of CE and CE/MPA is unknown. This randomized, double-blind, placebo-controlled, multicenter substudy of the Womens Health, Osteoporosis, Progestin, Estrogen (Womens HOPE) trial investigated the incidence of continued bone loss with lower-dose CE and CE/MPA. Eight hundred twenty-two healthy postmenopausal women with intact uteri received CE 0.625, CE 0.625/MPA 2.5, CE 0.45, CE 0.45/MPA 2.5, CE 0.45/MPA 1.5, CE 0.3, CE 0.3/MPA 1.5 (all doses in mg/day), or placebo for 2 years along with 600 mg/day of calcium. Changes from baseline in spine and total hip BMD were compared among treatment groups in an intent-to-treat analysis. At 12 months, <10% of women on active treatment lost >2% of spinal BMD (except CE 0.3/MPA 1.5 [15.6%]), compared with 41.2% of women on placebo. At 24 months, the percentages of women on active treatment who lost >2% of spine BMD ranged from 4.5% with CE 0.45/MPA 1.5–15.6% with CE 0.3/MPA 1.5, compared with 55.2% of women taking placebo. More than 85% of women on active treatment did not experience continued BMD loss at the hip at 12 months and 24 months, in contrast to 30.6% of women on placebo at 12 months and 36.5% at 24 months. Women receiving active treatment who lost >2% of spine or hip BMD also had a lesser reduction in biochemical markers of bone turnover. In summary, continued bone loss among early postmenopausal women treated with lower doses of CE or CE/MPA is uncommon.This revised version was published online in January 2005 with corrections to Table figures.     

Minodronic acid (ONO-5920/YM529) prevents decrease in bone mineral density and bone strength, and improves bone microarchitecture in ovariectomized cynomolgus monkeys

This study examined the effect of the highly potent nitrogen-containing bisphosphonate, minodronic acid (ONO-5920/YM529), on bone mineral density (BMD), bone turnover, bone microarchitecture and bone strength in ovariectomized (OVX) cynomolgus monkeys. Skeletally mature female cynomolgus monkeys, aged 9-17 years, were ovariectomized or sham-operated. Minodronic acid was administered orally once a day in doses of 0, 0.015, and 0.15 mg/kg from the day after surgery for 17 months. Bone resorption markers (urinary N-terminal cross-linking telopeptide of type I collagen and deoxypyridinoline), bone formation markers (serum osteocalcin and bone alkaline phosphatase) and lumbar vertebral BMD were measured at baseline and at 4, 8, 12 and 16 months after surgery. Treatment with minodronic acid dose-dependently inhibited OVX-induced increase in bone turnover markers and decrease in lumbar vertebral BMD, and minodronic acid at 0.15 mg/kg completely prevented these changes. At 17 months after surgery, minodronic acid also suppressed bone resorption (Oc.S/BS and N.Oc/BS) and bone formation (OS/BS, MS/BS, MAR, BFR/BS, and BFR/BV) in the lumbar vertebral bodies and tibia. In the mechanical tests, ultimate load on lumbar vertebral bodies and femoral neck of the OVX-control animals were significantly reduced compared to the sham animals. Minodronic acid prevented these reductions in bone strength at 0.15 mg/kg. There was significant correlation between BMD and bone strength, suggesting that the increase in bone strength was associated with the increase in BMD produced by minodronic acid. In micro-CT analysis of the lumbar vertebral bodies, minodronic acid improved trabecular architecture, converting rod structures into plate structures, and preventing the increase in trabecular disconnectivity at 0.15 mg/kg. In conclusion, similar to patients with postmenopausal osteoporosis, reduction in bone strength of lumbar vertebral bodies and femoral neck was clearly demonstrated in OVX cynomolgus monkeys. Minodronic acid prevented these reductions at a once-daily oral administration. Also, minodronic acid prevented OVX-induced changes in bone turnover, bone mass and bone microarchitecture. Long-term minodronic acid treatment was well tolerated and no adverse effects could be detected. These results suggest that minodronic acid may be a clinically useful drug for osteoporosis.     

孕激素对去势雌性大鼠骨密度及骨形态计量作用的初步研究

目的　了解孕激素对去势雌性大鼠骨密度及骨形态计量作用。方法　 5 0只 6月龄Wistar雌性大鼠随机分为 5组 :假手术组和卵巢切除组、卵巢切除后分别加安宫黄体酮 2mg组、安宫黄体酮 2 0mg组和倍美力组。手术后 7d喂药 ,用药后 3个月处死。测定各组大鼠子宫湿重、全身及股骨骨密度并取大鼠椎骨、胫骨组织切片进行形态计量分析。结果　两组孕激素组子宫湿重与卵巢切除组相同 ,均显著低于假手术组与倍美力组 (P <0 0 0 1)。假手术、雌、孕激素组全身骨密度测定均大于卵巢切除组 (P <0 0 5 )。各组股骨骨密度无显著差异。组织切片观察显示 ,假手术与倍美力组骨小梁粗壮、饱满、结构完整 ;卵巢切除组则纤细、断裂、完整性差。孕激素组骨小梁结构优于卵巢切除组但不及假手术及倍美力组。计量分析显示孕激素组椎骨骨小梁面积明显大于卵巢切除组(P <0 0 5 ) ,但低于倍美力组 (P <0 0 5 )。胫骨骨小梁面积与卵巢切除组相仿 ,均明显低于假手术和倍美力组 (P <0 0 5 )。孕激素 2mg与 2 0mg组间无明显差异。结论　两种剂量的安宫黄体酮对卵巢切除大鼠骨质疏松均有一定防治作用 ,但从骨组织形态计量分析 ,其作用较弱 ,与结合雌激素相比 ,尚不足以维持骨量     

A new vitamin D analog, 2MD, restores trabecular and cortical bone mass and strength in ovariectomized rats with established osteopenia.

An orally active, highly potent analog of 1alpha,25-dihydroxyvitamin D3, 2MD, restores trabecular and cortical bone mass and strength by stimulating periosteal bone formation and decreasing trabecular bone resorption in OVX rats with established osteopenia. INTRODUCTION: The purposes of this study were to determine the effects of long-term treatment with 2-methylene-19-nor-(20S)-1alpha,25(OH)2D3 (2MD) on restoring bone mass and bone strength in ovariectomized (OVX) rats with established osteopenia and 2MD effects on bone formation and bone resorption on trabecular and cortical bone surfaces. MATERIALS AND METHODS: Sprague-Dawley female rats were sham-operated (sham) or OVX at 4 months of age. Beginning at 8 weeks after OVX, OVX rats were orally dosed with 2MD at 0.5, 1, 2.5, 5, or 10 ng/kg/day for 16 weeks. Serum calcium was measured at 6, 13, and 16 weeks after treatment, and bone mass and structure, bone formation, bone resorption, and bone strength were determined at the end of the study. RESULTS: Serum calcium did not change significantly with 2MD at 0.5 or 1 ng/kg/day, whereas it significantly increased at 2.5, 5, or 10 ng/kg/day. 2MD significantly and dose-dependently increased total body BMD, total BMC, and stiffness of femoral shaft (FS), maximal load and stiffness of femoral neck, and toughness of the fifth lumbar vertebral body (L5) at all doses compared with OVX controls. In 2MD-treated OVX rats, there was a dose-dependent increase in total BMD and total BMC of the distal femoral metaphysis (DFM), trabecular bone volume of L3, ultimate strength and stiffness of L5, and maximal load of FS compared with OVX controls at dosages>or=1 ng/kg/day. At dosages>2.5 ng/kg/day, most of the bone mass and bone strength related parameters were significantly higher in 2MD-treated OVX rats compared with sham controls. Bone histomorphometric analysis of L3 showed dose-dependent decreases in osteoclast number and osteoclast surface on trabecular bone surface and a dose-dependent increase in periosteal bone formation associated with 2MD treatment. CONCLUSIONS: 2MD not only restored both trabecular and cortical bone mass but also added bone to the osteopenic OVX rats beyond that of sham controls by stimulating bone formation on the periosteal surface and decreasing bone resorption on the trabecular surface. 2MD increased bone mass and strength at doses that did not induced hypercalcemia.     

The Less Potent Estrogenic Effect of Tamoxifen on Bone in Ovariectomized Rats With Established Osteopenia

The longitudinal effects of tamoxifen (TAM) treatment on bone metabolism, spinal bone mineral density (BMD), and bone mineral content (BMC) were compared with those of estrogen in ovariectomized (OVX) rats with established osteopenia. The 6-month-old rats were divided into Sham (n = 8) and OVX (n = 24) groups. First, the OVX rats were allowed to lose bone for 6 weeks. Six weeks after ovariectomy they were divided into three groups: (1) OVX rats treated with solvent vehicle (OVX+Vehicle), (2) OVX rats injected with TAM subcutaneously six times a week at a dosage of 1.0 mg/kg body weight (OVX+TAM), (3) OVX rats injected with 17-β estradiol subcutaneously six times a week at a dosage of 0.1 mg/kg body weight (OVX+ET). The longitudinal effects of TAM and estrogen on bone were studied by dual energy X-ray absorptiometry (DXA) and biochemical markers including urinary pyridinoline (Pyr) and deoxypyridinoline (Dpyr). Ovariectomy resulted in a significant increase in urinary Pyr, Dpyr, and a significant decrease in spine BMD and BMC. TAM treatment completely inhibited the further bone loss in OVX rats with established osteopenia, however, estrogen increased spine BMD and BMC significantly compared with OVX+Vehicle, OVX+TAM, and baseline of treatment. Both TAM and estrogen treatment decreased urinary Pyr and Dpyr significantly in OVX rats. Our findings indicate that TAM acts as an estrogen agonist with respect to effects on spine BMD, BMC, and bone resorption in OVX rats with established osteopenia, but fails to restore spine BMD and BMC to the extent observed with estrogen in this study.     

不同剂量蛇床子素对OPG基因敲除小鼠和去卵巢骨质疏松大鼠作用疗效的比较研究

目的 观察不同剂量蛇床子素对OPG基因敲除小鼠和去卵巢骨质疏松大鼠的影响。方法 选择3种不同剂量的蛇床子素作用于OPG基因敲除小鼠和去卵巢骨质疏松大鼠,以双能X骨密度仪检测动物全身骨密度的变化;将动物腰椎做硬组织切片,并进行骨形态计量学分析其骨小梁的变化。结果 对于OPG基因敲除小鼠,蛇床子素能提高其全身BMD,以中剂量（10mg/（kg?d））组提高最为明显,低剂量（5mg/（kg?d））次之,而高剂量（15mg/（kg?d））组效果最差。蛇床子素能提高OPG基因敲除小鼠腰椎骨小梁体积分数,增加骨小梁数目,增加骨小梁厚度,降低骨小梁分离度,其中以5mg/(kg?d)组作用最明显,其次为10mg/(kg?d)组,而15mg/(kg?d)组则效果最差;对于去卵巢骨质疏松大鼠,不同剂量的蛇床子素均能显著提高大鼠全身BMD,其中以中剂量（100mg/（kg?d））组为最佳。蛇床子素能显著提高大鼠腰椎骨小梁体积分数,以100mg/（kg?d）组最明显。显著增加大鼠腰椎骨小梁数目,以75mg/（kg?d）组最明显。蛇床子素100mg/（kg?d）组能增加大鼠腰椎骨小梁厚度。不同剂量的蛇床子素均能显著降低大鼠腰椎骨小梁分离度,其中以75mg/（kg?d）组和100mg/（kg?d）组最明显。结论 蛇床子素能促进骨形成,抑制骨吸收,从而起到抗骨质疏松的作用,其疗效与给药剂量密切相关。     

中等强度跑台运动对去卵巢大鼠后肢骨骨矿物含量和骨密度的双重调节作用

目的 观察中等强度跑台运动对去卵巢大鼠后肢骨骨矿物含量(BMC)和骨密度(BMD)的影响.方法 将60只3月龄未经产雌性SD大鼠按体重随机分为假手术、去卵巢静止、去卵巢运动Ⅰ、去卵巢运动Ⅱ、去卵巢运动Ⅲ和去卵巢运动Ⅳ 6个组.各运动组经1周的跑台适应训练后,按实验设计分别进行为期14周的正式跑台训练.实验结束时,腹主动脉取血处死大鼠,双能χ-射线骨密度仪检测右侧游离股骨和胫骨的BMC和BMD.结果 ①与假手术组相比,去卵巢静止组股骨近端和远端以及胫骨近端BMC和BMD显著下降,但股骨中段以及胫骨中段和远端BMC和BMD无显著变化.②与去卵巢静止组相比,去卵巢运动Ⅰ组股骨近端和远端BMC显著增加,股骨中段以及胫骨3个部位BMC均无显著变化;去卵巢运动Ⅱ组和Ⅲ组股骨和胫骨3个部位BMC 均无显著变化;去卵巢运动Ⅳ组股骨3个部位BMC均无显著变化,而胫骨3个部位BMC均显著下降.③与去卵巢静止组相比,去卵巢运动Ⅰ组股骨近端和远端以及胫骨近端BMD 显著增加, 而股骨中段和胫骨中段和远端BMD无显著变化;去卵巢运动Ⅱ组和Ⅲ组股骨和胫骨任何部位BMD均没有显著变化;去卵巢运动Ⅳ组股骨3个部位BMD无显著变化,而胫骨3个部位BMD却显著下降.结论 较低中等强度跑台运动能减缓去卵巢大鼠股骨近端和远端骨矿物含量和骨密度的下降;而较高中等强度跑台运动却能加速去卵巢大鼠胫骨近端骨矿物含量和骨密度的下降.     

Different responsiveness of alveolar and tibial bone to bone loss stimuli.

Mandibular and systemic bone loss are poorly associated. We compared the effect of isocaloric protein undernutrition and/or ovariectomy on BMD and microstructure of mandibular alveolar and proximal tibia sites in adult rats. Mandibular bone was significantly less affected. INTRODUCTION: Whether mandibular bone and axial or peripheral skeleton respond similarly to systemic bone loss remains a subject of controversy. We have previously shown that mechanical loading during mastication influences bone mass and architecture of the mandibular alveolar bone. Isocaloric protein undernutrition and ovariectomy are known to cause bone loss and deterioration of bone microarchitecture at various axial and peripheral skeletal sites. We studied how the mandible, which is subjected to heavy, abrupt, and intermittent forces during mastication, responds to low-protein intake and/or ovariectomy and compared this response to that of the proximal tibia in adult rats. MATERIALS AND METHODS: Forty-four 6-month-old female Sprague-Dawley rats underwent transabdominal ovariectomy (OVX; n=22) or sham operation (n=22) and were pair-fed isocaloric diets containing either 15% or 2.5% casein (sham 15%, n=11; sham 2.5%, n=11; OVX 15%, n=11; and OVX 2.5%, n=11) for 16 weeks. BMD and bone microarchitecture parameters (e.g., bone volume fraction [BV/TV] and trabecular thickness and number) of the mandible and the proximal tibia were measured at the end of the experiment using DXA and microCT. RESULTS: Mandibular alveolar bone was negatively influenced by both protein undernutrition and OVX, but to a significantly lesser extent than the proximal tibia. In sham-operated animals, low-protein intake led to a 17.3% reduction of BV/TV in the mandible and 84.6% in the tibia (p<0.001). In normal protein diet-fed animals, OVX led to a reduction of BV/TV of 4.9% in the mandible but 82% in the tibia (p<0.001). In the mandible, protein undernutrition resulted in thinner trabeculae (p<0.05), whereas OVX led to a reduction of trabecular number (p<0.05). CONCLUSIONS: Mandibular alveolar bone was found to be less sensitive to either protein undernutrition or OVX than the proximal tibia spongiosa. We hypothesize that the mechanical loading of the alveolar process during mastication may protect the alveolar bone from the detrimental effects observed in other skeletal sites, such as the proximal tibia. Morphological and embryological differences between the two skeletal sites might also play a role.