Calcium supplementation does not reproduce the pharmacological efficacy of alfacalcidol for the treatment of osteoporosis in rats

Tranexamic Acid Protects Ovary and Testis Functions and Ameliorates Osteoporosis in Mice

INTRODUCTION

In a rapidly aging society, the number of people suffering from osteoporosis keeps increasing. However, effective prevention strategies for osteoporosis are not yet currently available.

OBJECTIVE

In this study, we examined the ameliorative effects of tranexamic acid on osteoporosis in 24-month-old mice.

METHODS

During the study period, mice were orally administered tranexamic acid 3 times per week.

RESULTS

Bone mineral density, which is a parameter of osteoporosis, was improved following tranexamic acid administration. In addition, female mice evidenced a stronger phenotypic improvement than male mice. In female mice treated with tranexamic acid, ovary abnormalities were reduced. Furthermore, the levels of transforming growth factor-β, hyaluronic acid, CD44, reactive oxygen species, and apoptosis, as well as the number of infiltrated neutrophils and macrophages in the ovary were lower than those in the control or solvent-administered mice. In addition, 17β-estradiol levels in blood increased when compared with the control or solvent-treated mice. In addition, administration of tranexamic acid to 24-month-old male mice decreased the level of apoptosis in the testis. However, the levels of 17β-estradiol and testosterone in blood increased compared with the control or solvent-administered mice.

CONCLUSIONS

The use of tranexamic acid had an ameliorative effect on osteoporosis, possibly by protecting ovaries and testes.

Microarchitecture and nanomechanical properties of trabecular bone after strontium administration in osteoporotic goats

Strontium (Sr) ralenate is a new agent used for the prevention and treatment of osteoporosis. As a bone-seeking element, 98% of Sr is deposited in the bone and teeth after oral ingestion. However, the effect of Sr treatment on bone microarchitecture and bone nanomechanical properties remains unclear. In this study, 18 osteoporotic goats were divided into four groups according to the treatment regimen: control, calcium alone (Ca), calcium and Sr at 24 mg/kg (Ca + 24Sr), and calcium and Sr at 40 mg/kg (Ca + 40Sr). The effects of Sr administration on bone microarchitecture and nanomechanical properties of trabecular bones were analyzed with micro-CT and nanoindentation test, respectively. Serum Sr levels increased six- and tenfold in the Ca + 24Sr and Ca + 40Sr groups, respectively. Similarly, Sr in the bone increased four- and sixfold in these two groups. Sr administration significantly increased trabecular bone volume fraction, trabecular thickness, and double-labeled new bone area. Sr administration, however, did not significantly change the nanomechanical properties of trabecular bone (elastic modulus and hardness). The data suggested that Sr administration increased trabecular bone volume and improved the microarchitecture while maintaining the intrinsic tissue properties in the osteoporotic goat model.

Effect of eldecalcitol, an active vitamin D analog, on hip structure and biomechanical properties: 3D assessment by clinical CT

The effects of an active vitamin D analog, eldecalcitol (ELD), on bone mineral density (BMD), bone geometry, and biomechanical properties of the proximal femur were investigated by using clinical CT. The subjects--a subgroup of a recent randomized, double-blind study comparing anti-fracture efficacy of ELD with alfacalcidol (ALF) - constituted 193 ambulatory patients with osteoporosis (189 postmenopausal women and 4 men aged 52-85 years, average ± SD: 70.9 ± 6.92 years) enrolled at 11 institutions. Multidetector-row CT data was acquired at baseline and at completion of 144 weeks' treatment. Cross-sectional densitometric and geometric parameters of the femoral neck were derived from three-dimensional CT data. Biomechanical properties including cross-sectional moment of inertia (CSMI), section modulus (SM) and buckling ratio (BR) of the femoral neck, and CSMI of the femoral shaft were also calculated. We found that, (1) with respect to the femoral neck cross-sectional parameters (total bone), in the ALF group, volumetric BMD (vBMD) decreased but bone mass was maintained and cross-sectional area (CSA) increased. In contrast, ELD maintained vBMD with a significant increase in bone mass and a trend toward increased CSA. (2) With respect to the femoral neck cross-sectional parameters (cortex), cortical thickness decreased in the ALF group, but was maintained in the ELD group. In the ALF group, vBMD and bone mass increased, and CSA was maintained. In the ELD group, vBMD, CSA, and bone mass increased. (3) With respect to the biomechanical properties of the femoral neck, ELD improved CSMI and SM to a greater extent than did ALF. BR increased in both the ALF and ELD groups. (4) With respect to the femoral shaft parameters, overall the results of bone geometry and CSMI of the femoral shaft were very consistent with the results for the femoral neck; however, cortical vBMD of the femoral shaft decreased significantly in both the ELD and ALF groups. In conclusion, our longitudinal analysis of hip geometry by clinical CT revealed the unexpected potential of ELD to increase cortical CSA, vBMD, and bone mass, and to maintain cortical thickness, probably through the more potent effect of ELD in mitigating endocortical bone resorption than ALF. By improving the biomechanical properties of the proximal femur, ELD may have the potential to reduce the risk of hip fractures.

Effects of alfacalcidol on mechanical properties and collagen cross-links of the femoral diaphysis in glucocorticoid-treated rats

Bone fragility is increased in glucocorticoid (GC)-induced osteopenia even though GC-treated patients have higher bone mineral density (BMD), suggesting that the impaired bone quality may affect bone strength. This study was conducted to clarify the effects of GC on bone strength and collagen cross-links of adult rats and the effect of coadministration of alfacalcidol (ALF), a prodrug of active vitamin D(3). Six-month-old male Wistar-Imamichi rats (n = 32) were divided into the following four groups with equal average body weight: (1) 4-week age-matched controls, (2) 4-week GC (prednisolone, 10 mg/kg daily, i.m.) with concomitant administration of vehicle, (3) 4-week GC with concomitant administration of ALF (0.05 μg/kg daily, p.o.), and (4) 4-week GC with concomitant administration of ALF (0.1 μg/kg daily, p.o.). At the end of treatment, BMD, collagen cross-links, mechanical properties of the femoral midshaft, bone metabolic markers, and biochemical parameters were analyzed. In the GC group, femoral bone strength decreased without any change of BMD. This was accompanied by a decrease in the content of enzymatic cross-links. ALF (0.1 μg/kg) inhibited the GC-induced reduction in bone strength. The content of mature cross-links in the 0.1-μg/kg ALF group was significantly higher than that in the GC group. GC treatment caused a decrease in bone metabolic markers and serum calcium levels, which was counteracted by ALF coadministration. Preventive treatment with ALF inhibited the deterioration of bone mechanical properties primarily in association with the restoration of enzymatic cross-link formation and amelioration of the adverse effects of GC treatment on calcium metabolism.

Recent progress in bone imaging for osteoporosis research

Advances in bone imaging techniques have provided tools for analyzing bone structure at the macro-, micro- and nano-level. Quantitative assessment of macrostructure can be achieved using dual X-ray absorptiometry (DXA) and quantitative computed tomography (QCT), particularly volumetric quantitative CT (vQCT). In vivo quantitative techniques for assessing the microstructure of trabecular bone non-invasively and non-destructively include high-resolution CT (HR-CT) and high-resolution magnetic resonance (HR-MR). Compared with MR imaging, CT-based techniques have the advantage of directly visualizing the bone in the axial skeleton, with high spatial resolution, but the disadvantage of delivering a considerable radiation dose. Micro-CT (μCT), which provides a higher resolution of the microstructure and is principally applicable in vitro, has undergone technological advances such that it is now able to elucidate the physiological skeletal change mechanisms associated with aging and determine the effects of therapeutic intervention on the bone microstructure. In particular, synchrotron μCT (SR-CT) provides a more detailed view of trabecular structure at the nano-level. For the assessment of hip geometry, DXA-based hip structure analysis (HSA) and CT-based HSA have been developed. DXA-based HSA is a convenient tool for analyzing biomechanical properties and for assuming cross-sectional hip geometry based on two-dimensional (2D) data, whereas CT-based HSA provides these parameters three-dimensionally in robust relationship with biomechanical properties, at the cost of greater radiation exposure and the lengthy time required for the analytical procedure. Further progress in bone imaging technology is promising to bring new aspects of bone structure in relation to bone strength to light, and to establish a means for analyzing bone structural properties in the everyday clinical setting.

Comparison of effects of alfacalcidol and alendronate on mechanical properties and bone collagen cross-links of callus in the fracture repair rat model

Both bone density and quality are important determinants of bone strength. Bone quality is prescribed by matrix characteristic including collagen cross-linking and bone structural characteristics and is important in reinforcement of bone strength. We investigated the effects of alfacalcidol (ALF), a prodrug of calcitriol, and alendronate (ALN), a bisphosphanate, on the mechanical properties and content of enzymatic cross-links in femoral bone using a fracture repair rat model. Forty 3-month-old female Wistar-Imamichi rats were randomized into 4 groups: SHAM (sham-operated+vehicle), OVX (ovariectomy+vehicle), ALF (ovariectomy+ALF, 0.1 microg/kg/d, p.o.) and ALN (ovariectomy+ALN, 10 microg/kg/d, s.c.). Treatment began immediately after SHAM or OVX surgery. Three weeks later, all animals underwent transverse osteotomies at the midshaft of the left femur. Treatment was continued and rats were sacrificed at 12 weeks post-fracture for evaluation by X-ray radiography, micro-CT, pQCT, biomechanical testing and bone histomorphometry. In the ALN group, no new cortical shell appeared and the callus diameter was significantly larger than in the OVX group (p<0.05). Stiffness of fractured callus in the ALF group, but not in the ALN group, was significantly higher than in the OVX group. Young's modulus in the ALN group was significantly decreased compared to the OVX group. Moreover, micro-CT analysis showed that ALN treatment increased the lowly mineralized bone in the callus by, resulting in the highest content of woven bone area and lowest content of lamellar bone. The total amount of enzymatic cross-links in both the ALF and ALN groups was significantly higher than in the OVX control group. Of particular interest, the Pyr-to-Dpyr ratio was significantly decreased by ALF administration, suggesting that ALF but not ALN normalized the enzymatic cross-link patterns in fractured bone to the control level. In conclusion, ALN and ALF treatment increased bone strength via the distinctive effect on bone mass and quality. ALN formed larger calluses and increased enzymatic cross-links despite delayed woven bone remodeling into lamellar bone, whereas ALF treatment induced lamellar bone formation coincided with increasing in the enzymatic cross-linking and normalizing the cross-link pattern in callus to native bone pattern.

The morphology and lattice structure of bone crystal after strontium treatment in goats

Strontium (Sr) compounds have become increasingly popular in osteoporosis treatment. As a bone seeking element, 98% of Sr deposits in bone and teeth after oral ingestion. However, the quality of new bone after Sr deposition is yet to be extensively investigated. In this study, eight osteopenic goats were divided into two groups: Ca + 40Sr (five goats) and controls (three goats). Controls were fed with low calcium feeds. Ca phosphate was supplied at 100 mg/(kg day), and Sr phosphate at 40 mg/(kg day) in the Ca + 40Sr group. The newly formed bone at the outer cortical area of the femur with Sr deposition was identified from tetracycline labels, and the morphology and lattice structure of the crystals in these regions were investigated. Results showed that Sr concentrations of bone tissue significantly increased 144.37% for Sr administration without significant change in Ca concentration, and the ingested Sr mainly deposited in new bone. The crystal isolated from new bone exhibited the typical character of biological apatite as determined by Fourier transform infrared spectroscopy and selected-area electron diffraction. Transmission electron microscopy examination showed that a crystal with width of 8-10 nm grew along with the (002) lattice and aligned with the same direction in both groups. The elemental analysis of crystals showed that the ingested Sr deposited mainly in the bone matrix or was absorbed on the bone crystal surface, while only a limited amount of Sr replaced Ca in apatite crystals. Our findings showed that Sr administration at current dosages for prevention and treatment of osteoporosis might not change the bone crystal morphology and structure.

Natural history and risk factors for bone loss in postmenopausal Caucasian women: a 15-year follow-up population-based study

In this 15-year follow-up study, we found that the estimated rate of bone loss at the femoral neck (FN) for women aged 45-68 was linear at a rate of 1.67% per year, but quadratic for lumbar spine (LS) at a rate of 3.12% initially, and slowing down with age. We also confirmed the protective role of HRT, increasing weight, and lean mass in long-term bone loss.

INTRODUCTION

The objective was to describe the natural history of bone loss and explore the role of environmental factors in postmenopausal women over a 15-year period.

METHODS

Bone mineral density (BMD) at the FN and the LS were measured in postmenopausal women from the Chingford Study. Height, weight, HRT status, and calcium/vitamin D supplement were assessed at each visit. Osteoarthritis of hip and spine was assessed by X-ray at baseline and at year 8.

RESULTS

A total of 955 postmenopausal women with an average age of 54.7 at baseline were included. Both FN and LS BMD decreased significantly with age (p<0.0001). The decline was larger in the LS (-3.12% per year), which showed a quadratic relationship, than in the FN (-1.67% per year) with a linear relationship. The rate of bone loss was reduced by one third annually for the FN and LS respectively in current HRT users. Change in weight was positively associated with both DeltaFN and DeltaLS BMD (beta=0.16% and 0.09% change in DeltaFN and DeltaLS BMD per kilogramme change in weight respectively, p<0.0001 for both sites). Spine OA and progression were positively associated with DeltaLS BMD (beta=1.22% change in DeltaLS BMD per grade in spine OA and 0.45% change in DeltaLS BMD for patients who progressed, p<0.0001 for spine OA and p=0.002 for spine OA progression). Spine OA (beta=0.54% change in DeltaFN BMD per grade, p<0.0001), but not progression, and hip OA were positively associated with DeltaFN BMD. Furthermore, both age and body weight at baseline were positively associated with both DeltaFN and DeltaLS BMD (beta=0.02-0.04% change in DeltaFN and DeltaLS BMD per year increase in age at baseline and 0.004-0.007% change in DeltaFN and DeltaLS BMD per kilogramme increase in weight at baseline, all p<0.0001).

CONCLUSION

This large population-based longitudinal study demonstrated that the decline of BMD over 15 years is linear with age for the FN, but quadratic for the LS. The study confirmed the protective role of HRT, increased weight and lean mass in long-term bone loss.

Alfacalcidol-stimulated focal bone formation on the cancellous surface and increased bone formation on the periosteal surface of the lumbar vertebrae of adult female rats

PURPOSE

To investigate the skeletal effects of alfacalcidol alone or in combination with exercise in intact adult female rats.

METHODS

Seventy-four 8.5-month-old rats were orally administered 0, 0.005, 0.025, 0.05 or 0.1 microg/kg of alfacalcidol for 12 weeks, alone or in combination with exercise. Cancellous bone histomorphometric measurements were performed on the second lumbar vertebra.

RESULTS

At 0.05 and 0.1 microg/kg, alfacalcidol caused a significant increase in cancellous bone volume, accompanied by an increase in trabecular architecture. Percent eroded surface, bone resorption and formation were suppressed by alfacalcidol treatment. However, mineral apposition rate was significantly increased, indicating osteoblast activity was increased. A positive balance between bone formation and resorption was observed in the rats treated with the highest dose of alfacalcidol. Alfacalcidol induced a unique bone formation site ("bouton") on the cancellous surface. These boutons connected adjacent trabeculae and increased trabecular thickness. They exhibited both smooth and scalloped cement lines, suggesting that they were formed by minimodeling- and remodeling-based bone formation. Furthermore, alfacalcidol at 0.1 microg/kg increased periosteal bone formation of the lumbar transverse processes. Bipedal stance exercise alone did not have an effect on bone balance and bone turnover. There were no interactions between alfacalcidol and bipedal stance exercise except for a decrease in bone resorption.

CONCLUSION

Alfacalcidol exhibited both anti-catabolic and anabolic effects on bone in intact female rats. The effect of combined treatment with alfacalcidol and bipedal stance exercise was no better than that of alfacalcidol alone.