Vitamin K-dependent carboxylation of osteocalcin affects the efficacy of teriparatide (PTH(1-34)) for skeletal repair

Vitamin K-Dependent Carboxylation of Osteocalcin in Bone-Ally or Adversary of Bone Mineral Status in Rats with Experimental Chronic Kidney Disease?

Chronic kidney disease (CKD) commonly occurs with vitamin K (VK) deficiency and impaired bone mineralization. However, there are no data explaining the metabolism of endogenous VK and its role in bone mineralization in CKD. In this study, we measured serum levels of phylloquinone (VK1), menaquinone 4 and 7 (MK4, MK7), and VK-dependent proteins: osteocalcin, undercarboxylated osteocalcin (Glu-OC), and undercarboxylated matrix Gla protein (ucMGP). The carboxylated osteocalcin (Gla-OC), Glu-OC, and the expression of genes involved in VK cycle were determined in bone. The obtained results were juxtaposed with the bone mineral status of rats with CKD. The obtained results suggest that the reduced VK1 level observed in CKD rats may be caused by the accelerated conversion of VK1 to the form of menaquinones. The bone tissue possesses all enzymes, enabling the conversion of VK1 to menaquinones and VK recycling. However, in the course of CKD with hyperparathyroidism, the intensified osteoblastogenesis causes the generation of immature osteoblasts with impaired mineralization. The particular clinical significance seems to have a finding that serum osteocalcin and Glu-OC, commonly used biomarkers of VK deficiency, could be inappropriate in CKD conditions, whereas Gla-OC synthesized in bone appears to have an adverse impact on bone mineral status in this model.

Machine Learning Algorithms: Prediction and Feature Selection for Clinical Refracture after Surgically Treated Fragility Fracture

BACKGROUND

The number of patients with fragility fracture has been increasing. Although the increasing number of patients with fragility fracture increased the rate of fracture (refracture), the causes of refracture are multifactorial, and its predictors are still not clarified. In this issue, we collected a registry-based longitudinal dataset that contained more than 7000 patients with fragility fractures treated surgically to detect potential predictors for clinical refracture.

METHODS

Based on the fact that machine learning algorithms are often used for the analysis of a large-scale dataset, we developed automatic prediction models and clarified the relevant features for patients with clinical refracture. Formats of input data containing perioperative clinical information were table data. Clinical refracture was documented as the primary outcome if the diagnosis of fracture was made at postoperative outpatient care. A decision-tree-based model, LightGBM, had moderate accuracy for the prediction in the test and the independent dataset, whereas the other models had poor accuracy or worse.

RESULTS

From a clinical perspective, rheumatoid arthritis (RA) and chronic kidney disease (CKD) were noted as the relevant features for patients with clinical refracture, both of which were associated with secondary osteoporosis.

CONCLUSION

The decision-tree-based algorithm showed the precise prediction of clinical refracture, in which RA and CKD were detected as the potential predictors. Understanding these predictors may improve the management of patients with fragility fractures.

Improvement of Lipotoxicity-Induced Islet β Cellular Insulin Secretion Disorder by Osteocalcin

BACKGROUND

Osteocalcin (OCN) has been proved to be closely related with the development of type 2 diabetes mellitus (T2DM). We aimed to study if OCN could improve the disorder of islet cell caused by lipotoxicity.

METHODS

Alizarin red staining was used to investigate the mineralization. Western blotting and ELISA methods were used to measure protein expression. Immunofluorescence staining was used to investigate the protein nuclear transfer.

RESULTS

High glucose and high fat inhibited the differentiation of osteoblast precursors. Overexpression of insulin receptor (InsR^OE) significantly promoted the Runx2 and OCN expression. The increase of insulin, Gprc6a, and Glut2 by osteoblast culture medium overexpressing insulin receptor was reversed by osteocalcin neutralizing antibody. Undercarboxylated osteocalcin (ucOC) suppressed the lipotoxic islet β-cell damage caused by palmitic acid. The FOXO1 from intranuclear to extranuclear was also significantly increased after ucOC treatment compared with the group PA. Knockdown of Gprc6a or suppression of PI3K/AKT signal pathway could reverse the upregulation of GPRC6A/PI3K/AKT/FoxO1/Pdx1 caused by ucOC.

CONCLUSION

OCN could activate the FOXO1 signaling pathway to regulate GLUT2 expression and improve the insulin secretion disorder caused by lipotoxicity.

Vitamin K2 promotes the osteogenic differentiation of periodontal ligament stem cells via the Wnt/β-catenin signaling pathway

OBJECTIVE

Vitamin K2 (MK-4, menaquinone 4) plays an important role in osteoprotection. The present study aimed to examine the effect of MK-4 on the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) in vitro and probed the potential signaling pathway.

DESIGN

PDLSCs were isolated from extracted premolars by tissue block culture method and were identified by flow cytometry. Cell Counting Kit-8 (CCK-8) and colony formation assays were used to determine the effect of MK-4 on the proliferation of PDLSCs. Alkaline phosphatase (ALP) activity was analyzed quantitatively, and extracellular matrix mineralization was examined by Alizarin Red S staining. The mRNA and protein expression levels of ALP, Runx Family Transcription Factor 2 (Runx2), osteocalcin (OCN), and Sp7 Transcription Factor (SP7; Osterix) were measured by qRT-PCR and Western blot. In addition, after adding the inhibitor XAV-939, Western blot was used to assess the correlation with the Wnt/β-catenin signaling pathway. The above results were obtained by observing at least three fields randomly, and each experiment was repeated at least three times.

RESULTS

This study found that 10^-5 M MK-4 significantly promoted the osteogenic differentiation of PDLSCs. Gene and protein expression levels of ALP, Runx2, OCN, and Osterix were all upregulated compared with control. Remarkably, after blocking the Wnt/β-catenin signaling pathway with XAV-939, the effect of MK-4 was apparently reversed.

CONCLUSION

These results demonstrate that MK-4 can promote the osteogenic differentiation of PDLSCs, which is likely related to the activation of the Wnt/β-catenin signaling pathway.

Comparison of the Efficacy and Renal Safety of Bisphosphonate Between Low-Dose/High-Frequency and High-Dose/Low-Frequency Regimens in a Late-Stage Chronic Kidney Disease Rat Model

The efficacy and renal safety of low-dose/high-frequency (LDHF) dosing and high-dose/low-frequency (HDLF) dosing of bisphosphonates (BPs) are comparable in patients with normal kidney function but might be different in patients with late-stage chronic kidney disease (CKD). This study aimed to compare the efficacy and renal safety of two different dosage regimens of a BP, alendronate (ALN), in stage 4 CKD using a rat model. Male, 10-week-old Sprague-Dawley rats were subjected to either 5/6 nephrectomy or sham surgery. The animals received subcutaneous administration of vehicle (daily) or ALN in LDHF dosage regimen (LDHF-ALN: 0.05 mg/kg/day) or HDLF dosage regimen (HDLF-ALN: 0.70 mg/kg/2 weeks). Medications commenced at 20 weeks of age and continued for 10 weeks. Micro-computed tomography, histological analysis, infrared spectroscopic imaging, and serum and urine assays were performed to examine the efficacy and renal safety of the ALN regimens. Both LDHF-ALN and HDLF-ALN increased bone mass, improved micro-structure, and enhanced mechanical properties, without causing further renal impairment in CKD rats. Histologically, however, HDLF-ALN more efficiently suppressed bone turnover, leading to more mineralized trabecular bone, than LDHF-ALN in CKD rats, whereas such differences between LDHF-ALN and HDLF-ALN were not observed in sham rats. Both LDHF-ALN and HDLF-ALN showed therapeutic effects on high bone turnover osteoporosis in CKD stage 4 rats without causing further renal impairment. However, as HDLF-ALN more efficiently suppressed bone turnover than LDHF-ALN in late-stage CKD, HDLF-ALN might be more appropriate than LDHF-ALN for fracture prevention in high bone turnover osteoporosis patients with late-stage CKD.

Role of vitamin K2 in bone metabolism: a point of view and a short reappraisal of the literature

Vitamin K₂ (vit K₂) belongs to a large group of fat-soluble compounds whose formulation is MK (menaquinone) (MK-2 to MK-14), that seem to be involved in different biological functions. In particular, vit K₂ has been recently recognized as efficacious and safe in treatment of bone loss, as it contributes to structural integrity of osteocalcin (OC), the major non-collagenous protein typically found in bone matrix. Several studies proved low vit K₂ intake is linked to bone loss and to increased fracture risk in both sexes. Nowadays, vit K₂ supplementation is considered a significant manner to enhance the association of calcium and vitamin D whose role on bone health is largely recognized. On the other hand, vit K₂ may be used alone or with other drugs to preserve bone quality/strength from skeletal degradation after menopause and/or in patients affected by secondary osteoporosis. In this paper, we review the most recent data about vit K₂ on skeleton.

Biomimetic hydroxyapatite/poly xylitol sebacic adibate/vitamin K nanocomposite for enhancing bone regeneration

Hydroxyapatite (HAP) is a significant bone mineral that establishes bone strength. HAP composites in combination with biodegradable and bioactive polymer poly xylitol sebacic adipate (PXSA) would result in a constant release at target sites. Numerous studies have shown that vitamin K (VK) might possess a vital function in bone metabolism. The purpose of the present study was to inspect the synthesized composite HAP/PXSA/VK in developing polymeric biomaterials composite for the application of bone tissue regeneration. FTIR, X-ray diffraction, SEM and TEM techniques were applied to characterize the prepared composites. The release of VK from the HAP/PXSA/VK composite was evidenced through UV-Vis spectroscopy. In vitro studies proved that the HAP/PXSA/VK composite is appropriate for mesenchymal stem cell culture. Compared to pure HAP prepared following the same method, HAP/PXSA/VK composite provided favourable microstructures and good biodegradation distinctiveness for the application of tissue engineering, as well as tissue in-growth characteristics and improved scaffold cell penetration. This work reveals that the HAP/PXSA/VK composites have the potential for applications in bone tissue engineering.

Optimal administration frequency and dose of teriparatide for acceleration of biomechanical healing of long-bone fracture in a mouse model

Despite preclinical studies demonstrating the effectiveness of teriparatide for skeletal repair in small animals, inconclusive data from clinical trials have raised questions regarding the optimal teriparatide dosing regimen for bone repair. To address this, we assessed the effect of teriparatide frequency and dose on long-bone healing using a mouse femur osteotomy/fracture model. Eight-week-old male ICR mice were subjected to open femur osteotomies, then randomized into following five groups (n = 8 per group): vehicle; low dose/high frequency: 3 μg/kg/dose, 3 times/day; low dose/low frequency: 9 μg/kg/dose, 1 time/day; high dose/high frequency: 9 μg/kg/dose, 3 times/day; high dose/low frequency: 27 μg/kg/dose, 1 time/day. Skeletal repair was assessed by microcomputed tomography, mechanical testing, and histology 4 weeks after surgery. High-dose and/or high-frequency teriparatide treatment increased callus bone volume but failed to have a significant impact on the biomechanical recovery of fractured femurs, possibly because of impaired cortical shell formation in fracture calluses. Meanwhile, low-dose/low-frequency teriparatide therapy enhanced callus bone formation without interfering with cortical shell formation despite a lesser increase in callus bone volume, leading to significant two and fourfold increases in ultimate load and stiffness, respectively. Our findings demonstrate that administering teriparatide at higher doses and/or higher frequencies raises fracture callus volume but does not always accelerate the biomechanical recovery of fractured bone, which points to the importance of finding the optimal teriparatide dosing regimen for accelerating skeletal repair.

Effects of combined menaquinone-4 and PTH1-34 treatment on osetogenesis and angiogenesis in calvarial defect in osteopenic rats

PURPOSE

The aim of this study was to evaluate the effect of combining human parathyroid hormone (1-34) (PTH_1-34; PTH) and menaquinone-4 (MK-4) on calvarial bone defect repair in osteopenic rats.

METHODS

Fourteen week olds were subject to craniotomy for the establishment of osteopenic animal models fed through a chronically low-protein diet. After that, critical calvarial defect model was established and all rats were randomly divided into four groups: sham, MK-4, PTH, and PTH + MK-4. The animals received MK-4 (30 mg/kg/day), PTH_1-34 (60 μg/kg, three times a week), or PTH_1-34 (60 μg/kg, three times a week) plus MK-4 (30 mg/kg/day) for 8 weeks, respectively. Serum γ-carboxylated osteocalcin (Gla-OC) levels, histological and immunofluorescent labeling were employed to evaluate the bone formation and mineralization in calvarial bone defect. In addition, Microfil perfusion, immunohistochemical, and micro-CT suggested enhanced angiogenesis and bone formation in calvarial bone healing.

RESULTS

In this study, treatment with either PTH_1-34 or MK-4 promoted bone formation and vascular formation in calvarial bone defects compared with the sham group. In addition, combined treatment of PTH_1-34 plus MK-4 increased serum level of Gla-OC, improved vascular number and vascular density, and enhanced bone formation in calvarial bone defect in osteopenic conditions as compared with monotherapy.

CONCLUSIONS

In summary, this study indicated that PTH_1-34 plus MK-4 combination therapy accelerated bone formation and angiogenesis in calvarial bone defects in presence of osteopenia.

Combined treatment with vitamin K2 and PTH enhanced bone formation in ovariectomized rats and increased differentiation of osteoblast in vitro

Osteoporosis is accompanied by insufficient osteogenic capacity. Several lines of evidence suggested that solutions to enhance osteoblastogenesis were important strategies for osteoporotic bone defect repair. This study investigated the effect of combined treatment with vitamin K2 and PTH on bone formation in calvarial bone defect in osteoporotic rats and its influence on osteoblast in vitro. Bilateral ovariectomy was used in SPF Sprague Dawley rats to generate an osteoporosis model. Subsequently, a calvarial defect model was established and all osteoporotic rats were randomly assigned to the following groups: control, VK (vitamin K2, 30 mg/kg everyday), PTH (recombinant human PTH (1-34), 60 μg/kg, three times a week) or VK + PTH (vitamin K2, 30 mg/kg everyday plus PTH, 60 μg/kg three times a week) for 8 weeks. In vitro, bone marrow-derived stem cells (BMSCs) were cultured and treated with vitamin K2, PTH or vitamin K2+PTH. ALP staining and western blot were performed to observe the influence of combined treatment on BMSCs. Bone formation within calvarial defect were assessed by serum γ-carboxylated osteocalcin (Gla-OC), micro-CT, histological and immunofluorescent labeling. In this study, combined treatment of PTH and vitamin K2 showed positive effects on preventing bone loss in femurs in OVX rats. Combined treatment increased serum Gla-OC and promoted bone formation in osteoporotic calvarial bone defects. Immunohistochemistry showed that OCN and RUNX2 were more highly expressed in the VK + PTH group than in the control groups. In vitro studies results suggested that combined treatment with PTH and vitamin K2 increased expression of ALP, BMP2 and RUNX2 in BMSCs. Our data suggested that the combination of vitamin K2 and PTH increased differentiation of osteoblast and had a synergistic effect on bone formation in osteoporotic calvarial bone defect.

Effects of combined human parathyroid hormone (1-34) and menaquinone-4 treatment on the interface of hydroxyapatite-coated titanium implants in the femur of osteoporotic rats

The objective of this study was to investigate the effects of human parathyroid hormone (1-34) (PTH_1-34; PTH) plus menaquinone-4 (vitamin K₂; MK) on the osseous integration of hydroxyapatite (HA)-coated implants in osteoporotic rats. Ovariectomized female Sprague-Dawley rats were used for the study. Twelve weeks after bilateral ovariectomy, HA-coated titanium implants were inserted bilaterally in the femoral medullary canal of the remaining 40 ovariectomized rats. All animals were then randomly assigned to four groups: Control, MK, PTH and PTH + MK. The rats from groups MK, PTH and PTH + MK received vitamin K₂ (30 mg/kg/day), PTH_1-34 (60 μg/kg, three times a week), or both for 12 weeks. Thereafter, serum levels of γ-carboxylated osteocalcin (Gla-OC) were quantitated by ELISA and the bilateral femurs of rats were harvested for evaluation. The combination of PTH and MK clearly increased the serum levels of Gla-OC (a specific marker for bone formation) compared to PTH or MK alone. The results of our study indicated that all treated groups had increased new bone formation around the surface of implants and increased push-out force compared to Control. In addition, PTH + MK treatment showed the strongest effects in histological, micro-computed tomography and biomechanical tests. In summary, our results confirm that treatment with PTH_1-34 and MK together may have a therapeutic advantage over PTH or MK monotherapy on bone healing around HA-coated implants in osteoporotic rats.

Combined treatment of vitamin K and teriparatide on bone metabolism and biomechanics in rats with osteoporosis

Postmenopausal osteoporosis is a degenerative disease caused by lack of estrogen whereby bone degeneration exceeds bone formation, resulting in loss of bone mass. Various drugs have been utilized in an attempt to ameliorate bone strength in such patients. The aim of the present study was to compare the effects of vitamin K or teriparatide alone and combined on bone metabolism and biomechanics in rats with osteoporosis. The ovaries of rats were excised to construct a rat model of osteoporosis. Rats were subjected to oral intake of vitamin K or subcutaneous injection of teriparatide or both for 8 weeks. ELISA was used to detect the content of carboxylated-type of osteocalcin (Gla-OC) and C-telopeptide of type I collagen (CTX-I) in serum. Bone density of shaft of femur and metaphyseal bone was measured. Three-point bending test was performed to analyze the load-deformation curve of femur. Undecalcified sections of femur were stained with toluidine blue to measure bone histomorphometric static, dynamic and bone resorption parameters. Compared with monotherapy, vitamin K combined with teriparatide significantly increased serum Gla-OC level and the number of osteoblast, decreased serum CTX-I level, reduced the number of osteoclasts and increased bone density and strength. This study showed that the efficacy of vitamin K combined with teriparatide is better than that of monotherapy. This combined treatment can promote bone formation, inhibit bone degradation, and improve bone density and strength.

Response to teriparatide in Chinese patients with established osteoporosis: osteocalcin and lumbar spine bone-mineral density changes from teriparatide Phase III study

Teriparatide is the first anabolic agent for osteoporosis, and this analysis aimed to understand responses to teriparatide in Chinese patients with established osteoporosis in subgroups. In this Phase III study of teriparatide in China, 362 patients were randomized at a 2:1 ratio to receive subcutaneous teriparatide (20 μg/day) or intranasal salmon calcitonin (200 IU/day) for 24 weeks. Teriparatide treatment produced a significantly greater increase in lumbar spine bone-mineral density (LS-BMD) in postmenopausal women than calcitonin at the 24-week end point. The relationship between osteocalcin (OCN) and LS-BMD was evaluated, and the greatest correlation was found between absolute OCN change at week 12 and percentage change in LS-BMD for patients in the teriparatide group (r=0.24, P<0.001). The correlation weakened at week 24 (r=0.16, P=0.02) and was negligibly negative for calcitonin-treated patients. Proportions of patients achieving >10 μg/L absolute OCN change from baseline in the teriparatide- and calcitonin-treated groups were 81% and 6% at week 12, respectively (P<0.001). Proportions of patients with increased LS-BMD ≥3% at week 24 from baseline were 71% and 35% in the teriparatide- and calcitonin-treated groups, respectively (P<0.001). Proportions of patients meeting both criteria were 63% for the teriparatide group and 1% for the calcitonin-treated group (P<0.001). Subgroup analysis suggested that significant increases in LS-BMD and OCN can be achieved in patients receiving teriparatide, regardless of baseline age, LS-BMD, and fracture times. The rate of treatment-emergent adverse events in each subgroup was similar to the overall analysis.

Efficacy and safety of osteoporosis medications in a rat model of late-stage chronic kidney disease accompanied by secondary hyperparathyroidism and hyperphosphatemia

This study showed that bisphosphonate was safe and effective for the treatment of bone disorders in stage 4 chronic kidney disease (CKD) rats. Intermittent teriparatide therapy showed an anabolic action on bone even under secondary hyperparathyroidism conditions without having an adverse effect on mineral metabolism in late-stage CKD.

INTRODUCTION

Patients with late-stage CKD are at high risk for fragility fractures. However, there are no consensus on the efficacy and safety of osteoporosis medications for patients with late-stage CKD. In the present study, we aimed to examine the efficacy and safety of alendronate (ALN) and teriparatide (TPD) for treating bone disorder in late-stage CKD with pre-existing secondary hyperparathyroidism using a rat model of CKD.

METHODS

Male 10-week-old Sprague-Dawley rats were subjected to a 5/6 nephrectomy or sham surgery and randomized into the following four groups: sham, vehicle (saline subcutaneous (sc) daily), ALN (50 μg/kg sc daily), and TPD (40 μg/kg sc daily). Medications commenced at 24 weeks of age and continued for 4 weeks. Micro-computed tomography, histological analysis, infrared spectroscopic imaging, and serum assays were performed.

RESULTS

Nephrectomized rats developed hyperphosphatemia, secondary hyperparathyroidism (SHPT), and high creatinine, equivalent to CKD stage 4 in humans. ALN suppressed the bone turnover and increased the degree of mineralization in cortical bone, resulting in an improvement in the mechanical properties. TPD further increased the bone turnover and significantly increased the degree of mineralization, micro-geometry, and bone volume, resulting in a significant improvement in the mechanical properties. Both ALN and TPD had no adverse effect on renal function and mineral metabolism.

CONCLUSIONS

BP is safe and effective for the treatment of bone disorders in stage 4 CKD rats. Intermittent TPD therapy showed an anabolic action on bone even under SHPT conditions without having an adverse effect on mineral metabolism in late-stage CKD.

Protective effect of VK2 on glucocorticoid-treated MC3T3-E1 cells

Glucocorticoids (GCs) contribute to the increased incidence of secondary osteoporosis and osteonecrosis, and medications for the prevention and treatment of these complications have been investigated for many years. Vitamin K₂ (VK₂) has been proven to promote bone formation both in vitro and in vivo. In this study, we examined the effects of VK₂ on dexamethasone (DEX)-treated MC3T3-E1 osteoblastic cells. We observed that VK₂ promoted the proliferation and enhanced the survival of dexamethasone-treated MC3T3-E1 cells. In addition, VK₂ upregulated the expression levels of osteogenic marker proteins, such as Runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteocalcin, which were significantly inhibited by dexamethasone. On the whole, our findings indicate that VK₂ has the potential to antagonize the effects of GCs on MC3T3-E1 cells, and may thus prove to be a promising agent for the prevention and treatment of GC-induced osteoporosis and osteonecrosis.

Relationship between velvet antler ossification and PTH and androgen serum levels in Tarim Red deer (Cervus elaphus)

Ossification degree is one of the primary variables affecting the medicinal value of velvet antler. Multiple factors regulate the calcification of velvet antler. We studied the relationship between the ossification of velvet antlers and the serum levels of parathyroid hormone (PTH) and androgen (ADG) in Tarim red deer. Enzyme-linked immunosorbent assays (ELISA) and atomic absorption spectrometry demonstrated that the changes in serum PTH and ADG levels nearly paralleled antler ossification during Tarim red deer antler mineralization. These results suggest that regulating the levels of serum PTH and ADG could decrease the calcification rate of velvet antlers in Tarim red deer. We conclude that PTH might increase antler ossification via the cAMP signaling pathway, and ADG possesses the dual roles of promoting both antler ossification and growth in Tarim red deer. This study suggests that we might be able to artificially control antler ossification to improve its medical value via the PTH or/and ADG pathway. J. Exp. Zool. 323A: 696-703, 2015. © 2015 Wiley Periodicals, Inc.

Endocrine role of bone: recent and emerging perspectives beyond osteocalcin

Recent developments in endocrinology, made possible by the combination of mouse genetics, integrative physiology and clinical observations have resulted in rapid and unanticipated advances in the field of skeletal biology. Indeed, the skeleton, classically viewed as a structural scaffold necessary for mobility, and regulator of calcium-phosphorus homoeostasis and maintenance of the haematopoietic niche has now been identified as an important regulator of male fertility and whole-body glucose metabolism, in addition to the classical insulin target tissues. These seminal findings confirm bone to be a true endocrine organ. This review is intended to detail the key events commencing from the elucidation of osteocalcin (OC) in bone metabolism to identification of new and emerging candidates that may regulate energy metabolism independently of OC.

Effects of the combination of vitamin K and teriparatide on the bone metabolism in ovariectomized rats

The purpose of the present study was to evaluate the combined effects of vitamin K (VK) and teriparatide (TPTD) on bone mineral density (BMD), mechanical strength and other parameters for bone metabolism using a rat ovariectomized osteoporosis model. Ovariectomized female Sprague-Dawley rats were administered with VK (an oral dose of 30 mg/kg/day), TPTD (a subcutaneous dose of 30 µg/kg, three times a week) or a combination for 8 weeks. Thereafter, serum levels of γ-carboxylated osteocalcin (Gla-OC) were quantitated by ELISA; BMD and mechanical strength were measured by computed tomography and biomechanical testing, respectively at the femoral metaphysis. Additionally, histomorphometry was performed using the toluidine blue-stained coronal sections of distal femur. The combination of VK and TPTD clearly increased the serum levels of Gla-OC (a specific marker for bone formation) and osteoblast surface (the number of osteoblasts attaching with the surface of cancellous bone), compared to VK or TPTD alone. In addition, the combination of the two agents improved the BMD and bone strength of the femur in the ovariectomized rats, compared to VK or TPTD alone. Taken together, these findings suggest that the treatment with VK and TPTD may have a therapeutic advantage over VK or TPTD monotherapy for postmenopausal osteoporosis, possibly by enhancing the bone formation through the actions on OC and osteoblasts.