Eldecalcitol: a review of its use in the treatment of osteoporosis

Eldecalcitol ameliorates diabetic osteoporosis and glucolipid metabolic disorder by promoting Treg cell differentiation through SOCE

Active vitamin D, known for its role in promoting osteoporosis, has immunomodulatory effects according to the latest evidence. Eldecalcitol (ED-71) is a representative of the third-generation novel active vitamin D analogs, and its specific immunological mechanisms in ameliorating diabetic osteoporosis remain unclear. We herein evaluated the therapeutic effects of ED-71 in the context of type 2 diabetes mellitus (T2DM), delving into its underlying mechanisms. In a T2DM mouse model, ED-71 attenuated bone loss and marrow adiposity. Simultaneously, it rectified imbalanced glucose homeostasis and dyslipidemia, ameliorated pancreatic β-cell damage and hepatic glycolipid metabolism disorder. Subsequently, in mice injected with the Treg cell-depleting agent CD25, we observed that the beneficial effects of ED-71 mentioned earlier were partially contingent on the Treg subsets ratio. Mechanistically, ED-71 promoted the differentiation of CD4+ T cells into Treg subsets, facilitating Ca2+ influx and the expression of ORAI1 and STIM1, pivotal proteins in store-operated Ca2+ entry (SOCE). The SOCE inhibitor, 2-APB, partially attenuated the positive effects of ED-71 observed in the above results. Overall, ED-71 regulates SOCE-mediated Treg cell differentiation, accomplishing the dual purpose of simultaneously ameliorating diabetic osteoporosis and glucolipid metabolic disorders, showcasing its potential in osteoimmunity therapy and interventions for diseases involving SOCE.

Syntheses of 25-Adamantyl-25-alkyl-2-methylidene-1α,25-dihydroxyvitamin D3 Derivatives with Structure-Function Studies of Antagonistic and Agonistic Active Vitamin D Analogs

The active form of vitamin D₃, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], is a major regulator of calcium homeostasis through activation of the vitamin D receptor (VDR). We have previously synthesized vitamin D derivatives with large adamantane (AD) rings at position 24, 25, or 26 of the side chain to study VDR agonist and/or antagonist properties. One of them-ADTK1, with an AD ring and 23,24-triple bond-shows a high VDR affinity and cell-selective VDR activity. In this study, we synthesized novel vitamin D derivatives (ADKM1-6) with an alkyl group substituted at position 25 of ADTK1 to develop more cell-selective VDR ligands. ADKM2, ADKM4, and ADKM6 had VDR transcriptional activity comparable to 1,25(OH)₂D₃ and ADTK1, although their VDR affinities were weaker. Interestingly, ADKM2 has selective VDR activity in kidney- and skin-derived cells-a unique phenotype that differs from ADTK1. Furthermore, ADKM2, ADKM4, and ADKM6 induced osteoblast differentiation in human dedifferentiated fat cells more effectively than ADTK1. The development of vitamin D derivatives with bulky modifications such as AD at position 24, 25, or 26 of the side chain is useful for increased stability and tissue selectivity in VDR-targeting therapy.

Overview of the clinical efficacy and safety of eldecalcitol for the treatment of osteoporosis

Eldecalcitol (ELD) is a new oral analog of the active form of vitamin D with anti-resorptive properties. We conducted a meta-analysis to investigate the efficacy and safety of ELD in osteoporosis. Compared with alfacalcidol, ELD significantly lowered vertebral facture risk, increased bone mineral density, but also had a higher risk of hypercalciuria.

PURPOSE

This study aimed to investigate the efficacy and safety of eldecalcitol (ELD) in osteoporosis by examining fracture rates, bone mineral density (BMD), bone turnover markers, and adverse events as outcomes.

METHODS

PubMed, EMBASE, and Cochrane Library were searched up to July 20, 2020, to identify eligible randomized controlled trials. The odds ratio (OR) or weighted mean difference (WMD) with 95% confidence interval was calculated by the random-effects model.

RESULTS

ELD significantly increased lumbar BMD (WMD: 2.80; 95% CI: 1.60, 4.00; P < 0.001, 2 studies involved), total hip BMD (WMD: 2.11; 95% CI: 0.68, 3.55; P = 0.004, 2 studies involved), and femoral neck BMD (WMD: 1.78; 95% CI: 0.76, 2.79; P = 0.001, 1 study involved) compared with alfacalcidol. Moreover, ELD caused a significantly lower rate of vertebral fracture (OR: 0.52; 95% CI: 0.29-0.95; P = 0.034, 2 studies involved) than alfacalcidol, but did not lower the rate of non-vertebral facture (OR: 0.44; 95% CI: 0.06-3.05; P = 0.405, 2 studies involved) compared with alfacalcidol. ELD significantly reduced the percentage change in bone-specific alkaline phosphatase (WMD: - 15.40; 95% CI: - 20.30, - 10.60; P < 0.001, 1 study involved) and serum type I collagen C-telopeptide (WMD: - 38.50; 95% CI: - 50.00, - 27.10; P < 0.001, 1 study involved) as compared with alfacalcidol. ELD was also associated with higher risk of hypercalciuria compared with alfacalcidol (OR: 1.64; 95% CI: 1.22, 2.20; P = 0.001, 2 studies involved).

CONCLUSIONS

This systematic review indicated that ELD was superior than alfacalcidol for improving vertebral fracture risk and BMD. Further large-scale trials should be conducted to verify the long-term effects and safety of ELD in osteoporosis.

PROSPERO REGISTRATION NUMBER

CRD42020147518.

Machine learning prediction of 3CLpro SARS-CoV-2 docking scores

Molecular docking results of two training sets containing 866 and 8,696 compounds were used to train three different machine learning (ML) approaches. Neural network approaches according to Keras and TensorFlow libraries and the gradient boosted decision trees approach of XGBoost were used with DScribe’s Smooth Overlap of Atomic Positions molecular descriptors. In addition, neural networks using the SchNetPack library and descriptors were used. The ML performance was tested on three different sets, including compounds for future organic synthesis. The final evaluation of the ML predicted docking scores was based on the ZINC in vivo set, from which 1,200 compounds were randomly selected with respect to their size. The results obtained showed a consistent ML prediction capability of docking scores, and even though compounds with more than 60 atoms were found slightly overestimated they remain valid for a subsequent evaluation of their drug repurposing suitability.

[Development of Novel Biologically Active Compounds Based on Synthetic Organic Chemistry]

The aging population has had an impact on society in recent decades. Aging-associated health issues are a particularly challenging aspect to regulate. Therefore, the extension of healthy life expectancy by the application of biologically active compounds is an attractive research topic in the fields of medicinal chemistry, chemical biology, and also organic synthesis. Herein, the first total synthesis of acaulide, acaulone A and 10-keto-acaudiol A is described. These compounds were originally isolated from a culture of Acaulium sp. H-JQSF. Acaulide exhibits anti-osteoporosis activity in a prednisolone-induced osteoporotic zebrafish model; hence, this natural product is expected to be a new lead compound for anti-osteoporosis drugs. The characteristic acaulide skeletons were synthesized via late-stage Michael addition inspired by the proposed biosynthetic pathways. The conformational analysis of the 14-membered macrodiolide revealed the specific conformation that enabled the late-stage stereoselective functionalization.

Co(iii)-Catalyzed stereospecific synthesis of (E)-homoallylic alcohols with 4-vinyl-1,3-dioxan-2-ones: late-stage C–H homoallylation of indole derivatives

An Co(iii)-catalyzed stereoselective C–H homoallylation reaction to access (E)-homoallylic alcohols was developed. This protocol provides a powerful approach for the late-stage C–H homoallylation of indole-based molecules.

A Novel Vitamin D Receptor Agonist, VS-105, Improves Bone Mineral Density without Affecting Serum Calcium in a Postmenopausal Osteoporosis Rat Model

BACKGROUND AND OBJECTIVES

VS-105, a novel vitamin D receptor agonist with significantly less hypercalcemic side effects than calcitriol, is a useful tool to investigate whether or not a vitamin D receptor agonist at non-hypercalcemic doses could improve bone mineral density (BMD).

METHODS

VS-105 and calcitriol were evaluated in an ovariectomized (OVX) osteoporosis rat model and in calvariae bone organ culture.

RESULTS

Treatment of OVX rats by VS-105 (0.1, 0.2 or 0.5 μg/kg, intraperitoneal, 3×/week, for 90 days) significantly improved BMD in the L3 lumbar vertebra in a dose-dependent manner (sham vs. OVX/vehicle: 324 ± 14 vs. 279 ± 10 mg/cm²; VS-105 at 0.1, 0.2 and 0.5 μg/kg: 306 ± 9, 329 ± 12, and 327 ± 10 mg/cm², respectively) without affecting serum calcium (Ca). Calcitriol at 0.1 μg/kg significantly increased BMD but it also increased serum Ca. VS-105 and calcitriol at the test doses significantly suppressed serum parathyroid hormone and promoted tibia bone growth. With respect to biomarkers of bone remodeling, calcitriol and VS-105 both significantly elevated serum osteocalcin. In the calvariae bone organ culture, net Ca release was significantly less in VS-105-treated groups (vs. calcitriol).

CONCLUSIONS

VS-105 is efficacious in improving BMD in a dose range that does not affect serum Ca in OVX rats; the improvement in BMD by VS-105 is attributable to increased osteoblastic activity and reduced osteoclastic bone resorption.

The therapeutic effect to eldecalcitol + bisphosphonate is superior to bisphosphonate alone in the treatment of osteoporosis: a meta-analysis

BACKGROUND

Osteoporosis is a metabolic bone disease. Bisphosphonate (BP) and eldecalcitol (ELD) are two clinical first-line drugs for osteoporosis patients. However, the effect of ELD + BP vs. BP alone on osteoporosis treatment is still unclear. The present meta-analysis was conducted to evaluate the different therapeutic effect of BP + ELD vs. BP alone in osteoporosis treatment.

METHODS

Eligible documents that selected from online databases including PubMed, Embase, and Cochrane Library were included in this study (updated to March 3, 2020). The quality assessment of the included studies was based on the guidelines of Cochrane. Meta-analysis was performed according to criteria such as intervention plan and outcome. The indicators including bone mineral density (BMD) in all enrolled studies were included in the current analysis. Pooled odds ratios (ORs) and weighted mean differences (WMDs) with 95% confidence intervals (CI) were calculated using fixed- or random-effects models. Then, heterogeneity analysis was performed based on Cochran's Q test and I2 statistics.

RESULTS

A total of 4 studies (456 cases) with high quality were enrolled in this study. The effect of ELD + BP was superior to BP alone based on indicators including femoral neck BMD (FN-BMD) and total hip BMD (TH-BMD) in patients with followed up ≤ 6 months. Moreover, the effect of ELD + BP was superior to BP alone based on lumbar spine BMD (LS-BMD) in patients with 12 months followed up.

CONCLUSION

Therapeutic effect of ELD + BP was superior to BP alone in osteoporotic patients based on the influence of BMD.

Eldecalcitol (ED-71)-induced exosomal miR-6887-5p suppresses squamous cell carcinoma cell growth by targeting heparin-binding protein 17/fibroblast growth factor-binding protein-1 (HBp17/FGFBP-1)

Heparin-binding protein 17/fibroblast growth factor-binding protein-1 (HBp17/FGFBP-1) was purified from A431 cell-conditioned media based on its capacity to bind to fibroblast growth factor 1 and 2 (FGF-1 and FGF-2). HBp17/FGFBP-1 has been observed to induce the tumorigenic potential of epithelial cells and is highly expressed in oral cancer cell lines and tissues. HBp17/FGFBP-1 is also recognized as a pro-angiogenic molecule as a consequence of its interaction with FGF-2. We have previously reported that Eldecalcitol (ED-71), an analog of 1α,25(OH)₂D₃, downregulated the expression of HBp17/FGFBP-1 and inhibited the proliferation of squamous cell carcinoma (SCC) cells in vitro and in vivo through NF-κb inhibition. To explore the possibility of microRNA (miRNA) control of HBp17/FGFBP-1, we analyzed exosomal miRNAs from medium conditioned by A431 cells treated with ED-71. Microarray analysis revealed that 12 exosomal miRNAs were upregulated in ED-71-treated A431 cells. Among them, miR-6887-5p was identified to have a predicted mRNA target matching the 3' untranslated region (3'-UTR) of HBp17/FGFBP-1. The 3'-UTR of HBp17/FGFBP-1 was confirmed to be a direct target of miR-6887-5p in SCC/OSCC cells, as assessed with a luciferase reporter assay. Functional assessment revealed that overexpression of miR-6887-5p in SCC/OSCC cells inhibited cell proliferation and colony formation in vitro, and inhibited tumor growth in vivo compared with control. In conclusion, our present study supports a novel anti-cancer mechanism involving the regulation of HBp17/FGFBP-1 function by exosomal miR-6887-5p in SCC/OSCC cells, which has potential utility as a miRNA-based cancer therapy.

Eldecalcitol is more effective in promoting osteogenesis than alfacalcidol in Cyp27b1-knockout mice

Calcium (Ca) absorption from the intestinal tract is promoted by active vitamin D (1α,25D3). Vitamin D not only promotes Ca homeostasis, but it also inhibits bone resorption and promotes osteogenesis, thus playing a role in the maintenance of normal bone metabolism. Because 1α,25D3 plays an important role in osteogenesis, vitamin D formulations, such as alfacalcidol (ALF) and eldecalcitol (ELD), are used for treating osteoporosis. While it is known that, in contrast to ALF, ELD is an active ligand that directly acts on bone, the reason for its superior osteogenesis effects is unknown. Cyp27b1-knockout mice (Cyp27b1-/-mice) are congenitally deficient in 1α,25D3 and exhibit marked hypocalcemia and high parathyroid hormone levels, resulting in osteodystrophy involving bone hypocalcification and growth plate cartilage hypertrophy. However, because the vitamin D receptor is expressed normally in Cyp27b1-/-mice, they respond normally to 1α,25D3. Accordingly, in Cyp27b1-/-mice, the pharmacological effects of exogenously administered active vitamin D derivatives can be analyzed without being affected by 1α,25D3. We used Cyp27b1-/-mice to characterize and clarify the superior osteogenic effects of ELD on the bone in comparison with ALF. The results indicated that compared to ALF, ELD strongly induces ECaC2, calbindin-D9k, and CYP24A1 in the duodenum, promoting Ca absorption and decreasing the plasma concentration of 1α,25D3, resulting in improved osteogenesis. Because bone morphological measurements demonstrated that ELD has stronger effects on bone calcification, trabecular formation, and cancellous bone density than ALF, ELD appears to be a more effective therapeutic agent for treating postmenopausal osteoporosis, in which cancellous bone density decreases markedly. By using Cyp27b1-/-mice, this study was the first to succeed in clarifying the osteogenic effect of ELD without any influence of endogenous 1α,25D3. Furthermore, ELD more strongly enhanced bone mineralization, trabecular proliferation, and cancellous bone density than did ALF. Thus, ELD is expected to show an effect on postmenopausal osteoporosis, in which cancellous bone mineral density decreases markedly. In the future, this study may enable the development of next-generation active vitamin D derivatives with higher affinity for bone than ELD.

25 S-Adamantyl-23-yne-26,27-dinor-1α,25-dihydroxyvitamin D3: Synthesis, Tissue Selective Biological Activities, and X-ray Crystal Structural Analysis of Its Vitamin D Receptor Complex

Both 25 R- and 25 S-25-adamantyl-23-yne-26,27-dinor-1α,25-dihydroxyvitamin D₃ (4a and 4b) were stereoselectively synthesized by a Pd(0)-catalyzed ring closure and Suzuki-Miyaura coupling between enol-triflate 7 and alkenyl-boronic ester 8. The 25 S isomer (4b) showed high vitamin D receptor (VDR) affinity (50% of that of the natural hormone 1α,25-dihydroxyvitamin D₃, 1) and transactivation potency (kidney HEK293, 90%). In endogenous gene expression, it showed high cell-type selectivity for kidney cells (HEK293, CYP24A1 160% of 1), bone cells (MG63, osteocalcin 64%), and monocytes (U937, CAMP 96%) over intestine (SW480, CYP24A1 8%) and skin (HaCaT, CYP24A1 7%) cells. The X-ray crystal structural analysis of 4b in complex with rat VDR-ligand binding domain (LBD) showed the highest Cα positional shift from the 1/VDR-LBD complex at helix 11. Helix 11 of the 4b and 1 VDR-LBD complexes also showed significant differences in surface properties. These results suggest that 4b should be examined further as another candidate for a mild preventive osteoporosis agent.

Effect of eldecalcitol on articular cartilage through the regulation of transcription factor Erg in a murine model of knee osteoarthritis

Clinical studies have reported an association between low blood levels of 25-hydroxyvitamin D and the progression of osteoarthritis (OA), but the mechanism and effects of vitamin D signaling on articular chondrocytes and cartilage remains unclear. The purpose of this study was to investigate the effects of vitamin D on articular cartilage degeneration using eldecalcitol (ED-71), which is an active vitamin D₃ analog. Eight-week old male C57BL/6NCrSlc mice were subjected to experimental surgery to induce OA and local treatments with 10 μL ED-71 (0.5 μg/mL) were administered weekly. Four and 12 weeks after surgery, joints were evaluated using histological scoring systems. In addition, gene expression was analyzed in chondrocytes that were isolated from wildtype neonatal mice, cultured, and treated with ED-71 (10^-8 M). Joints treated with ED-71 demonstrated slowed progression of OA at 4 weeks after surgery, but few effects were observed at 12 weeks after surgery. Ets-related gene (Erg) expression was upregulated in OA articular cartilage, and further increased by ED-71 treatment. In primary chondrocytes cultured with ED-71, the gene expression of Erg and lubricin/proteoglycan 4 significantly increased, as compared to that of cells cultured without ED-71. Local treatment with ED-71 reduced degenerative changes to the articular cartilage during the early phase of experimental OA. Regulation of Erg by ED-71 in articular cartilage could confer resistance to early osteoarthritic changes.

A vitamin D analogue, eldecalcitol, enhances expression of fast myosin heavy chain subtypes in differentiated C2C12 myoblasts

BACKGROUND

Several lines of evidence indicate that the active form of vitamin D has an anabolic effect on skeletal muscle. Eldecalcitol, an analogue of the active form of vitamin D, has the potential to increase bone density and decrease fracture risk. The objective of this study was to investigate the effect of eldecalcitol in C2C12 myogenic cells.

METHODS

C2C12 cells were grown to confluency and the culture medium was replaced with low-glucose DMEM containing 2% horse serum. Eldecalcitol was added at a concentration of 1, 10 or 100 nM. Gene expression profiles of vitamin D receptor (VDR), MyoD, IGF-1, neonatal myosin heavy chain (MHC), and the fast MHC subtypes Ia, IIa, IIb and IId/x were analyzed by quantitative RT-PCR. Protein expression of MHC subtypes was evaluated by western blotting and immunostaining.

RESULTS

Eldecalcitol upregulated gene expression of VDR, MyoD and IGF-1. Incubation with eldecalcitol in the absence of serum followed by the addition of serum after 1 h was associated with greater increases in the expression of these genes compared with co-incubation with eldecalcitol and serum. Gene expression of MHC subtypes IIa, IIb and IId/x was significantly increased by eldecalcitol. Protein expression of fast MHC subtypes was significantly increased by eldecalcitol at 1 and 10 nM.

CONCLUSION

Similar to the active form of vitamin D, eldecalcitol had an anabolic effect on fast MHC subtypes. Taking into account its pharmacokinetic profile, eldecalcitol is expected to be beneficial for the maintenance and improvement of muscle function in elderly individuals.

Eldecalcitol prevents endothelial dysfunction in postmenopausal osteoporosis model rats

Postmenopausal women have high incidence of cardiovascular events as estrogen deficiency can cause endothelial dysfunction. Vitamin D is reported to be beneficial on endothelial function, but it remains controversial whether vitamin D is effective for endothelial dysfunction under the treatment for osteoporosis in postmenopausal women. The aim of this study was to evaluate the endothelial protective effect of eldecalcitol (ELD) in ovariectomized (OVX) rats. ELD (20  ng/kg) was orally administrated five times a week for 4 weeks from 1 day after surgery. After that, flow-mediated dilation (FMD) as an indicator of endothelial function was measured by high-resolution ultrasound in the femoral artery of living rats. ELD ameliorated the reduction of FMD in OVX rats. ELD inhibited the increase in NOX4, nitrotyrosine, and p65 and the decrease in dimer/monomer ratio of nitric oxide synthase in OVX rat femoral arteries. ELD also prevented the decrease in peroxisome proliferator-activated receptor gamma (PPARγ) in femoral arteries and cultured endothelial cells. Although PPARγ is known to inhibit osteoblastogenesis, ELD understandably increased bone mineral density of OVX rats without increase in PPARγ in bone marrow. These results suggest that ELD prevented the deterioration of endothelial function under condition of preventing bone loss in OVX rats. This endothelial protective effect of ELD might be exerted through improvement of endothelial nitric oxide synthase uncoupling, which is mediated by an antioxidative effect through normalization of vascular PPARγ/NF-κB signaling.

Vitamin D in cancer chemoprevention

CONTEXT

There is increasing evidence that Vitamin D (Vit D) and its metabolites, besides their well-known calcium-related functions, may also exert antiproliferative, pro-differentiating, and immune modulatory effects on tumor cells in vitro and may also delay tumor growth in vivo.

OBJECTIVE

The aim of this review is to provide fresh insight into the most recent advances on the role of Vit D and its analogues as chemopreventive drugs in cancer therapy.

METHODS

A systematic review of experimental and clinical studies on Vit D and cancer was undertaken by using the major electronic health database including ISI Web of Science, Medline, PubMed, Scopus and Google Scholar.

RESULTS AND CONCLUSION

Experimental and clinical observations suggest that Vit D and its analogues may be effective in preventing the malignant transformation and/or the progression of various types of human tumors including breast cancer, prostate cancer, colorectal cancer, and some hematological malignances. These findings suggest the possibility of the clinical use of these molecules as novel potential chemopreventive and anticancer agents.

HDX reveals unique fragment ligands for the vitamin D receptor

Modulation of the vitamin D receptor (VDR) with a ligand has the potential to be useful for the oral treatment of osteoporosis. One component of our lead generation strategy to identify synthetic ligands for VDR included a fragment based drug design approach. Screening of ligands in a VDR fluorescence polarization assay and a RXR/VDR conformation sensing assay resulted in the identification of multiple fragment hits (lean >0.30). These fragment scaffolds were subsequently evaluated for interaction with the VDR ligand binding domain using hydrogen-deuterium exchange (HDX) mass spectrometry. Significant protection of H/D exchange was observed for some fragments in helixes 3, 7, and 8 of the ligand binding domain, regions which are similar to those seen for the natural hormone VD3. The fragments appear to mimic the A-ring of VD3 thereby providing viable starting points for synthetic expansion.

Eldecalcitol for the treatment of osteoporosis

Eldecalcitol (1α, 25-dihydroxy-2β-[3-hydroxypropyloxy] vitamin D₃; ED-71) is a new analog of the active form of vitamin D. Eldecalcitol has recently been approved for the treatment of osteoporosis in Japan. In addition to regulation of calcium metabolism carried out by conventional vitamin D analogs, eldecalcitol possesses a strong inhibitory effect on bone resorption and causes a significant increase in bone mineral density. A Phase III clinical trial on osteoporosis showed that eldecalcitol reduced the incidence of new vertebral fractures over 3 years by 26% compared with alfacalcidol. Although the overall risk of nonvertebral fractures was not reduced by eldecalcitol, the risk of wrist fracture was decreased significantly in the eldecalcitol group (71%) compared with the alfacalcidol group. The serum level of 25-hydroxyvitamin D (25[OH]D) was normalized by supplementation of native vitamin D in this trial, so the desirable effects on bone by eldecalcitol were considered to be derived from its distinctive pharmacological action. Increased blood calcium was observed in 21% of patients treated with eldecalcitol, and hypercalcemia (>11.5 mg/dL) occurred in 0.4% of eldecalcitol recipients, so serum calcium concentration should be monitored after starting eldecalcitol treatment. Eldecalcitol has dual effects on the metabolism of bone and calcium and is useful for the treatment of osteoporosis, especially for elderly patients (who frequently suffer from vitamin D deficiency). This article reviews the clinical efficacy and safety of eldecalcitol in the treatment of osteoporosis.

Sphingosine-1-phosphate-mediated osteoclast precursor monocyte migration is a critical point of control in antibone-resorptive action of active vitamin D

The migration and positioning of osteoclast precursor monocytes are controlled by the blood-enriched lipid mediator sphingosine-1-phosphate (S1P) and have recently been shown to be critical points of control in osteoclastogenesis and bone homeostasis. Here, we show that calcitriol, which is the hormonally active form of vitamin D, and its therapeutically used analog, eldecalcitol, inhibit bone resorption by modulating this mechanism. Vitamin D analogs have been used clinically for treating osteoporosis, although the mode of its pharmacologic action remains to be fully elucidated. In this study, we found that active vitamin D reduced the expression of S1PR2, a chemorepulsive receptor for blood S1P, on circulating osteoclast precursor monocytes both in vitro and in vivo. Calcitriol- or eldecalcitol-treated monocytoid RAW264.7 cells, which display osteoclast precursor-like properties, migrated readily to S1P. Concordantly, the mobility of circulating CX3CR1(+) osteoclast precursor monocytes was significantly increased on systemic administration of active vitamin D. These results show a mechanism for active vitamin D in controlling the migratory behavior of circulating osteoclast precursors, and this action should be conducive to limiting osteoclastic bone resorption in vivo.

The effect of cholecalciferol and calcitriol on biochemical bone markers in HIV type 1-infected males: results of a clinical trial

HIV-1-infected patients have an increased risk of osteoporosis and fractures. The main objective of this study was to evaluate the bone metabolism in HIV-1-infected patients exposed to calcitriol and cholecalciferol. We also investigated the relationship between T cells and bone markers. We conducted a placebo-controlled randomized study running for 16 weeks including 61 HIV-1-infected males, of whom 51 completed the protocol. Nineteen participants were randomized to daily treatment with (A) 0.5-1.0 μg calcitriol and 1,200 IU (30 μg) cholecalciferol, 17 participants to (B) 1,200 IU cholecalciferol, and 15 participants to (C) placebo. At baseline and after 16 weeks, we determined collagen type 1 trimeric cross-linked peptide (CTx), procollagen type 1 N-terminal peptide (P1NP), parathyroid hormone (PTH), ionized calcium, 25-hydroxyvitamin D (25OHD), and 1,25-dihydroxyvitamin D [1,25(OH)2D]. We determined naive CD4(+) and CD8(+), activated CD4(+) and CD8(+), and regulatory CD4(+)CD25(+)CD127(low) T lymphocytes. Baseline levels of P1NP and CTx correlated (coefficient 0.5, p<0.001) with each other but not with PTH, 25OHD, or 1,25(OH)2D. In patients receiving calcitriol and cholecalciferol, the mean levels of P1NP (p<0.001) and CTx (p= 0.002) declined significantly compared to our placebo group. Based on changes in P1NP and CTx, we estimated that net bone formation occurred more frequently in group A compared to groups B and C. PTH correlated inversely with naive CD4(+) and CD8(+) cells. Otherwise, no relationships between bone markers and T lymphocytes were demonstrated. Supplementation with calcitriol and cholecalciferol induced biochemical indications of bone formation in HIV-1 patients.

Eldecalcitol: newly developed active vitamin D(3) analog for the treatment of osteoporosis

INTRODUCTION

Eldecalcitol is an active vitamin D(3) analog, characterized by high stability in the circulation and also in the peripheral tissues, and by strong activity in increasing bone mass in osteoporotic patients. The objective of the present review was to evaluate the effect of eldecalcitol on bone compared with active vitamin D or placebo in preclinical and clinical studies.

AREAS COVERED

Eldecalcitol increased bone mineral density and reduced bone turnover markers greater than alfacalcidol and placebo. Interestingly, in a 3-year clinical trial, bone resorption marker remained suppressed during the eldecalcitol treatment, whereas bone formation markers gradually recovered after initial suppression. The incidences of vertebral fractures and wrist fractures in eldecalcitol-treated group were significantly lower than those in alfacalcidol-treated group by 26 and 71%, respectively. In the patients whose baseline bone turnover was low, eldecalcitol treatment did not further suppress bone turnover markers during the 3-year treatment period.

EXPERT OPINION

Eldecalcitol reduced wrist fractures much greater than alfacalcidol and one of the reasons may be a stronger effect of eldecalcitol on preventing falls. Although the effect of eldecalcitol on bone turnover markers was stronger than that of alfacalcidol or placebo, eldecalcitol is not a mere antibone resorptive agent, rather act as a bone turnover modulator.