Effect of vitamin K2 on osteoblast apoptosis: vitamin K2 inhibits apoptotic cell death of human osteoblasts induced by Fas, proteasome inhibitor, etoposide, and staurosporine

Can vitamins improve periodontal wound healing/regeneration?

Periodontitis is a complex inflammatory disorder of the tooth supporting structures, associated with microbial dysbiosis, and linked to a number if systemic conditions. Untreated it can result in an irreversible damage to the periodontal structures and eventually teeth loss. Regeneration of the lost periodontium requires an orchestration of a number of biological events on cellular and molecular level. In this context, a set of vitamins have been advocated, relying their beneficial physiological effects, to endorse the biological regenerative events of the periodontium on cellular and molecular levels. The aim of the present article is to elaborate on the question whether or not vitamins improve wound healing/regeneration, summarizing the current evidence from in vitro, animal and clinical studies, thereby shedding light on the knowledge gap in this field and highlighting future research needs. Although the present review demonstrates the current heterogeneity in the available evidence and knowledge gaps, findings suggest that vitamins, especially A, B, E, and CoQ10, as well as vitamin combinations, could exert positive attributes on the periodontal outcomes in adjunct to surgical or nonsurgical periodontal therapy.

Electrospun sandwich mesh structures loaded with naringenin and vitamin K2 polycaprolactone/gelatin nanofibers synergistically promote bone regeneration

Osteoblasts and osteoclasts play a crucial role in the dynamically coupled balance during bone regeneration and remodeling. They complement and restrict each other in the human body. Decreased osteoblasts lead to insufficient bone formation or excessive formation of osteoclasts, leading to increased bone resorption, which will destroy the structure of the bone tissue. This will greatly increase the risk of diseases such as osteoporosis and nonunions caused by bone defects. Herein, gelatin and polycaprolactone were used as substrates, and biomaterial membranes with mesh and sandwich structures were constructed using the electrospinning technology. Naringenin was loaded into the shell, and vitamin K2 was loaded into the core layer of the nanofibrous membrane. The biocompatibility and osteogenic capacity of the membranes were assessed in vitro using mouse bone marrow mesenchymal stem cells (BMSCs). During osteoclast induction, the receptor activator of nuclear factor kappa-Β ligand (RANKL) was used to coculture RAW264.7 cells with various materials. The regulatory effect of various membranes on osteoclast growth was evaluated by detecting the expression levels of osteoclast-related genes and proteins in the cells. Subsequently, we constructed a model of a rat skull defect and implanted different membranes into the defect. Then, we evaluated the new bone formation in the defect using histological staining and micro-computed tomography after 4 and 8 weeks. The results of in vitro experiments confirmed that the incorporation of naringenin and vitamin K2 stimulated the expression of osteogenesis-related genes and the secretion of osteogenesis-related proteins. Simultaneously, the results showed that naringenin and vitamin K2 inhibited the formation and growth of osteoclasts. Therefore, naringenin and vitamin K2 have a synergistic effect in promoting bone growth and regulating osteoclast growth.

The additive effect of vitamin K supplementation and bisphosphonate on fracture risk in post-menopausal osteoporosis: a randomised placebo controlled trial

This study assessed whether vitamin K, given with oral bisphosphonate, calcium and/or vitamin D has an additive effect on fracture risk in post-menopausal women with osteoporosis. No difference in bone density or bone turnover was observed although vitamin K1 supplementation led to a modest effect on parameters of hip geometry.

PURPOSE

Some clinical studies have suggested that vitamin K prevents bone loss and may improve fracture risk. The aim was to assess whether vitamin K supplementation has an additive effect on bone mineral density (BMD), hip geometry and bone turnover markers (BTMs) in post-menopausal women with osteoporosis (PMO) and sub-optimum vitamin K status receiving bisphosphonate, calcium and/or vitamin D treatment.

METHODS

We conducted a trial in 105 women aged 68.7[12.3] years with PMO and serum vitamin K1 ≤ 0.4 µg/L. They were randomised to 3 treatment arms; vitamin K1 (1 mg/day) arm, vitamin K2 arm (MK-4; 45 mg/day) or placebo for 18 months. They were on oral bisphosphonate and calcium and/or vitamin D. We measured BMD by DXA, hip geometry parameters using hip structural analysis (HSA) software and BTMs. Vitamin K1 or MK-4 supplementation was each compared to placebo. Intention to treat (ITT) and per protocol (PP) analyses were performed.

RESULTS

Changes in BMD at the total hip, femoral neck and lumbar spine and BTMs; CTX and P1NP did not differ significantly following either K1 or MK-4 supplementation compared to placebo. Following PP analysis and correction for covariates, there were significant differences in some of the HSA parameters at the intertrochanter (IT) and femoral shaft (FS): IT endocortical diameter (ED) (% change placebo:1.5 [4.1], K1 arm: -1.02 [5.07], p = 0.04), FS subperiosteal/outer diameter (OD) (placebo: 1.78 [5.3], K1 arm: 0.46 [2.23] p = 0.04), FS cross sectional area (CSA) (placebo:1.47 [4.09],K1 arm: -1.02[5.07], p = 0.03).

CONCLUSION

The addition of vitamin K1 to oral bisphosphonate with calcium and/or vitamin D treatment in PMO has a modest effect on parameters of hip geometry. Further confirmatory studies are needed.

TRIAL REGISTRATION

The study was registered at Clinicaltrial.gov:NCT01232647.

Molecules Inducing Dental Stem Cells Differentiation and Bone Regeneration: State of the Art

Teeth include mesenchymal stem cells (MSCs), which are multipotent cells that promote tooth growth and repair. Dental tissues, specifically the dental pulp and the dental bud, constitute a relevant source of multipotent stem cells, known as dental-derived stem cells (d-DSCs): dental pulp stem cells (DPSCs) and dental bud stem cells (DBSCs). Cell treatment with bone-associated factors and stimulation with small molecule compounds are, among the available methods, the ones who show excellent advantages promoting stem cell differentiation and osteogenesis. Recently, attention has been paid to studies on natural and non-natural compounds. Many fruits, vegetables, and some drugs contain molecules that can enhance MSC osteogenic differentiation and therefore bone formation. The purpose of this review is to examine research work over the past 10 years that has investigated two different types of MSCs from dental tissues that are attractive targets for bone tissue engineering: DPSCs and DBSCs. The reconstruction of bone defects, in fact, is still a challenge and therefore more research is needed; the articles reviewed are meant to identify compounds useful to stimulate d-DSC proliferation and osteogenic differentiation. We only consider the results of the research which is encouraging, assuming that the mentioned compounds are of some importance for bone regeneration.

Role of Vitamin K in Bone and Muscle Metabolism

Vitamin K, a cofactor for the γ-glutamyl carboxylase enzyme, is required for the post-translational activation of osteocalcin and matrix Gla protein, which play a key role in bone and muscle homeostasis. In vivo and in vitro models for osteoporosis and sarcopenia suggest the vitamin K could exert a positive effect in both conditions. In bone, it increases osteoblastogenesis, whilst decreases osteoclast formation and function. In muscle, it is associated with increased satellite cell proliferation and migration and might play a role in energy metabolism. Observational trials suggest that high levels of vitamin K are associated with increased bone mineral density and reduced fracture risk. However, interventional studies for vitamin K supplementation yielded conflicting results. Clinical trials in sarcopenia suggest that vitamin K supplementation could improve muscle mass and function. One of the main limitations on the vitamin K studies are the technical challenges to measure its levels in serum. Thus, they are obtained from indirect sources like food questionnaires, or levels of undercarboxylated proteins, which can be affected by other environmental or biological processes. Although current research appoints to a beneficial effect of vitamin K in bone and muscle, further studies overcoming the current limitations are required in order to incorporate this supplementation in the clinical management of patients with osteosarcopenia.

Efficacy and safety of vitamin K2 for postmenopausal women with osteoporosis at a long-term follow-up: meta-analysis and systematic review

INTRODUCTION

Vitamin K2 supplementation has been revealed to be effective in the prevention and treatment of osteoporosis in Japan, but further proof for the effectiveness of this practice is still needed.

OBJECTIVE

To investigate whether vitamin K2 supplementation plays a role in maintaining bone mineral density (BMD) and reducing the incidence of fractures for postmenopausal women with osteoporosis at a long-term follow-up.

MATERIALS AND METHODS

We searched systematically throughout the databases of PubMed, Cochrane library, and EMBASE from the dates of their inception to November 16 2021 in this meta-analysis and systematic review, using keywords vitamin K2 and osteoporosis.

RESULTS

Nine RCTs with 6853 participants met the inclusion criteria. Vitamin K2 was associated with a significantly increased percentage change of lumbar BMD and forearm BMD (WMD 2.17, 95% CI [1.59-2.76] and WMD 1.57, 95% CI [1.15-1.99]). There were significant differences in undercarboxylated osteocalcin (uc-OC) reduction (WMD -0.96, 95% CI [-0.70 to 0.21]) and osteocalcin (OC) increment (WMD 26.52, 95% CI [17.06-35.98]). Adverse reaction analysis showed that there seemed to be higher adverse reaction rates in the vitamin K2 group (RR = 1.33, 95% CI [1.11-1.59]), but no serious adverse events related to vitamin K2 supplementation.

CONCLUSION

This meta-analysis and systematic review seemed to support the hypothesis that vitamin K2 plays an important role in the maintenance and improvement of BMD, and it decreases uc-OC and increases OC significantly at a long-term follow-up. Vitamin K2 supplementation is beneficial and safe in the treatment of osteoporosis for postmenopausal women.

Gradient radiation breeding and culture domestication of menaquinone producing strains

By comparing the survival rate and positive mutation rate of the primary mutagenic strain and progeny mutagenic strain under different radiation doses, the results showed that the tolerance of the mutagenic strain to radiation dose increased with the increase of the mutagenic generations. We adopted an improved gradient radiation breeding strategy to improve the breeding efficiency. The strains were treated with radiation in four stages. The first stage was low energy N⁺ ion implantation (ion energy 15 keV, dose 80 × 2.6 × 10¹³ cm^-2). In the second stage, the energy and dose of N⁺ ion reached to 20 keV, 90 × 2.6 × 10¹³ cm^-2. In the third stage, ⁶⁰Co-γ radiation (dose of 1.56 kGy) was used. In the fourth stage, the radiation dose of ⁶⁰Co-γ increased to 1.82 kGy. After each stage of radiation, the MK (Menaquinone) precursor 1, 4-dihydroxy-2-naphthalate (DHNA) was used as the stress factor to domesticate the mutant strains. By gradually increasing the concentration of DHNA in the culture medium, the substrate tolerance of Flavobacterium sp. was effectively improved. By measuring SOD (superoxide dismutase) activity and malondialdehyde, it showed that the cell damage caused by radiation mutagenesis to the offspring mutant was less than that of the primary mutant. Changes in membrane permeability and membrane potential of the mutant strains were reflected in changes in fluorescence intensity of luciferin diacetate and rhodamine 123, which could explain the enhanced substrate tolerance of strain F-2. After gradient radiation breeding and culture acclimation, the biomass of mutant Strain F-2 was 6.59 g/L, and the MK yield was 9.59 mg/L.

Is vitamin K2 a treatment choice for atypical femoral fractures in patients with secondary osteoporosis?

An atypical femoral fracture (AFF) is a rare complication associated with excessive inhibition of osteoclast expression during treatment of osteoporosis. We herein describe a patient who had been treated with alendronate for more than 10 years and subsequently developed an AFF that healed after treatment with vitamin K₂ (VK2). We also discuss the potential beneficial effects of VK2 on the healing of AFFs. A 48-year-old Asian man with secondary osteoporosis was treated with alendronate for more than 10 years. The patient underwent surgical treatment for a complete AFF of the right femur. Six months postoperatively, he complained of pain in his left thigh. X-ray examination revealed an incomplete AFF of the left femoral shaft. He was then treated with VK2. After 4 months of VK2 treatment, the patient reported that the pain in his left thigh had decreased, and follow-up X-ray examination demonstrated healing of the left AFF line. This case report indicates that VK2 may be a potential direction for pharmacological treatment of AFFs in future research.

Vitamin K and D Supplementation and Bone Health in Chronic Kidney Disease-Apart or Together?

Vitamin K (VK) and vitamin D (VD) deficiency/insufficiency is a common feature of chronic kidney disease (CKD), leading to impaired bone quality and a higher risk of fractures. CKD patients, with disturbances in VK and VD metabolism, do not have sufficient levels of these vitamins for maintaining normal bone formation and mineralization. So far, there has been no consensus on what serum VK and VD levels can be considered sufficient in this particular population. Moreover, there are no clear guidelines how supplementation of these vitamins should be carried out in the course of CKD. Based on the existing results of preclinical studies and clinical evidence, this review intends to discuss the effect of VK and VD on bone remodeling in CKD. Although the mechanisms of action and the effects of these vitamins on bone are distinct, we try to find evidence for synergy between them in relation to bone metabolism, to answer the question of whether combined supplementation of VK and VD will be more beneficial for bone health in the CKD population than administering each of these vitamins separately.

Effect of Vitamin K2 Alone or in Combination on Various Bone Turnover Markers Amongst Postmenopausal Females

Background

Osteoporosis is common in postmenopausal women. Some studies have demonstrated the usefulness of vitamin K through the action of bone-specific proteins and osteoblast and osteoclast activities. However, no systematic review had explored this aspect in postmenopausal women. Hence, this systematic review aimed to explore the effect of vitamin K₂ alone or in combination with other agents (vitamin D₃ or calcium) on various bone turnover markers (BTMs) and bone mineral density (BMD) in postmenopausal women.

Methods

MEDLINE, ScienceDirect, PubMed, and Google Scholar were searched to identify relevant studies using specific inclusion criteria. Data extraction and quality assessment were carried out using standardized tests, and the results were narratively synthesized and presented in the form of tables.

Results

Vitamin K₂ was beneficial in inducing an improvement or preventing deterioration, as evidenced by the BMD and osteocalcin (OC), undercarboxylated OC (ucOC), carboxylated OC (cOC), and γ-carboxylated OC levels. However, its effect was not conclusive when procollagen type 1 N-terminal propeptide, carboxyterminal propeptide of type I procollagen, C-terminal telopeptide of type I collagen, bone alkaline phosphatase, deoxypyridinoline, and N-terminal telopeptide levels (NTX) and ucOC:cOC or cOC:ucOC, and NTX:creatinine ratios were examined.

Conclusions

Vitamin K₂ supplementation combined with vitamin D and calcium was found to be advantageous. However, vitamin K₂ supplementation cannot replace the existing treatment options. In addition, vitamin K₂ should be used with caution, considering its interactions with food and other drugs.

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.

Effect of Low-Dose Vitamin K2 Supplementation on Bone Mineral Density in Middle-Aged and Elderly Chinese: A Randomized Controlled Study

Previous studies indicated a positive effect of vitamin K2 (VK2) supplementation on bone turnover biomarkers and bone mineral density (BMD), but the doses varied, and few studies have focused on the difference between VK2 supplementation alone and in combination with calcium and vitamin D₃. The aim of this study was to explore a low and effective dose of VK2 for improving BMD, and to examine whether the co-supplementation of VK2, calcium and vitamin D₃ would bring greater effects. In this trial, a total of 311 community-dwelling men and postmenopausal women aged 50 and 75 years were randomly assigned to four groups, receiving placebo, 50 µg/day, 90 µg/day or co-supplementation with calcium (500 mg/day) and vitamin D₃ (10 µg/day) for 1 year. At the endpoint, the bone loss of femoral neck was significantly lower in postmenopausal women in the two 90 µg groups (treatment × time, p = 0.006) compared with placebo, but no effects in men. Serum biomarkers cOC/ucOC ratio increased in the intervention groups (treatment × time, p < 0.001). VK2 supplementation in dose of 90 µg/day performed a significant effect on reducing bone loss in postmenopausal women, but in combination with calcium and vitamin D₃ brought no additional effects.Trial registration This trial was registered at http://www.chictr.org.cn as chiCTR1800019240.

Protective Effects of Vitamin K Compounds on the Proteomic Profile of Osteoblasts under Oxidative Stress Conditions

Oxidative stress, which accompanies the pathogenesis of many bone diseases, contributes to the reduction of osteoblast activity, resulting in the inhibition of differentiation. This study aimed to assess the effect of vitamins K1 and K2 (MK4 and MK7) on the proteomic profile of human osteoblasts cell line under oxidative conditions induced by hydrogen peroxide (H₂O₂). The analysis was performed using QExactiveHF mass spectrometer with a nanoelectrospray ionization source. The osteoblast protein exposed to oxidative stress and vitamin K was compared with the proteome of cells exposed only to oxidative stress. Our proteomic analysis identified 1234 proteins changed after 5 days, 967 after 15 days, and 1214 after 20 days of culture. We observed the most frequent changes in the expression of proteins with catalytic activity or protein/DNA binding properties (45% and 40%, respectively). Significant changes were also observed in proteins with transcription/translation regulator activity (2–6%), regulators of molecular functions (5–6%), signal transducers (1–4%), transporters (4–6%), and structural molecules (3–5%). Our results clearly show that vitamins K protect cells from H₂O₂-induced changes in protein expression, primarily through their effects on transcriptional regulators and transporter proteins. As a result, vitamins K can support the formation, remodeling, and mineralization of bone tissue.

Increased Consumption of Plant Foods Is Associated with Increased Bone Mineral Density

OBJECTIVES

To determine the relationship between plant food consumption and bone mineral density (BMD) in a healthy population when age, gender, BMI and physical activity are accounted for.

DESIGN

Cross-sectional study.

SETTING

Participants were recruited from the Sydney Adventist hospital and the University of New South Wales, Sydney, Australia.

PARTICIPANTS

33 males and 40 females (total n=73) participated in this study. The mean age was 56.1 ± 8.5 years. All participants were non-diabetic and in general good health.

MEASUREMENTS

A principle component analysis (PCA) was performed on 12 month self-report food intake data, gathered using the Cancer Council Victoria Dietary Questionnaire for Epidemiological Studies Version 2. Dual-energy X-ray absorptiometry was used to measure total BMD. Fasting plasma total protein, calcium and 25-Hydroxy Vitamin D levels were analysed by the Sydney Adventist Hospital pathology laboratory. Anthropometric measures were obtained using a standardized protocol. Self-reported physical activity levels were assessed using the International Physical Activity Questionnaire.

RESULTS

The PCA revealed three principle components. These were termed 'Meat Based', 'Junk Food' and 'Plant Based.' After controlling for age, gender, physical activity and BMI, the Plant Based component correlated positively with BMD (p=0.054, R2=0.439) and T-score (p=0.053, R2=0.221). Using a similar model no association between the Meat Based component and BMD or T-score was found. However, when the Plant Based component was included the Meat Based component correlated positively with BMD (p=0.046, R2=0.474) and T-score (p=0.046, R2=0.279). There was no significant association between the Junk Food component and BMD or T-score. People in the third Plant (927 ± 339 vs 751 ± 255 g/day, p=0.025) and Meat Based (921 ± 270 vs 676 ± 241 g/day, p=0.002) tertile had higher calcium intakes than those in the first. People in the second Plant Based tertile had higher plasma Vitamin D levels than those in the first (63.5 ± 16.8 vs. 52.3 ± 22.1 nmol/L, p=0.053) while those in the third Junk Food tertile had lower levels than those in the first (52.4 ± 18.5 vs. 65.4 ± 19.8 nmol/L, p=0.027). No association between Plant Based tertiles and protein intake was observed, however those in the third Meat Based (99.7 ± 25.1 vs. 50.9 ± 13.8 g/day, p=0.000) and Junk Food (87.4 ± 30.7 vs. 56.6 ± 22.2 g/day, p=0.000) tertile had higher protein intake compared to those in the first tertile.

CONCLUSION

In a healthy middle aged population with normal BMD, an increase in plant food consumption, either alone or in combination with a diet containing meat, is associated with improved bone mineralisation markers. This positive relationship is most likely due to the extensive range of micronutrients and phytochemicals packaged within plants.

The efficacy and safety of menatetrenone in the management of osteoporosis: a systematic review and meta-analysis of randomized controlled trials

In our systematic review and meta-analysis, we comprehensively evaluated menatetrenone in the management of osteoporosis. We found that menatetrenone decreased the ratio of undercarboxylated osteocalcin to osteocalcin (ucOC/OC) and improved lumbar BMD compared with placebo based on the 18 studies assessed. However, its benefit in fracture risk control was uncertain.

INTRODUCTION

We performed a systematic review and meta-analysis of the efficacy and safety of menatetrenone in managing osteoporosis.

METHODS

PubMed, Cochrane Library, Embase, ClinicalTrials.gov , and three Chinese literature databases (CNKI, CBM, Wanfang) were searched for relevant randomized controlled trials (RCTs) published before October 5, 2017, comparing menatetrenone with other anti-osteoporotic drugs or placebo in treating osteoporosis. The pooled risk ratio (RR) or mean difference (MD) and 95% confidence interval (CI) were calculated using fixed-effects or random-effects meta-analysis.

RESULTS

Eighteen RCTs (8882 patients) were included. Pooled analyses showed that menatetrenone was more effective than placebo in improving lumbar bone mineral density (BMD) (five studies, N = 658, MD = 0.05 g/cm², 95% CI 0.01 to 0.09 g/cm²) and decreasing ucOC/OC (two studies, N = 75, MD = - 21.78%, 95% CI - 33.68 to - 9.87%). Compared with placebo, menatetrenone was associated with a nonsignificantly decreased risk of vertebral fracture (five studies, N = 5508, RR = 0.87, 95% CI 0.64 to 1.20). Evidence on other anti-osteoporotic drugs as comparators was limited and revealed no significantly different effects of menatetrenone on BMD or fracture risks. Furthermore, compared with placebo, menatetrenone significantly increased the incidence of adverse events (AEs) (two studies, N = 1949, RR = 1.47, 95% CI 1.07 to 2.02) and adverse drug reactions (four studies, N = 6102, RR = 1.29, 95% CI 1.07 to 1.56). However, no significant difference in the incidence of serious AEs was found between menatetrenone and placebo.

CONCLUSIONS

Menatetrenone significantly decreases ucOC and might improve lumbar BMD in osteoporotic patients. However, its benefit in fracture risk control is uncertain.

Beneficial Effects of Vitamins K and D3 on Redox Balance of Human Osteoblasts Cultured with Hydroxyapatite-Based Biomaterials

Hydroxyapatite-based biomaterials are commonly used in surgery to repair bone damage. However, the introduction of biomaterials into the body can cause metabolic alterations, including redox imbalance. Because vitamins D3 and K (K1, MK-4, MK-7) have pronounced osteoinductive, anti-inflammatory, and antioxidant properties, it is suggested that they may reduce the adverse effects of biomaterials. The aim of this study was to investigate the effects of vitamins D3 and K, used alone and in combination, on the redox metabolism of human osteoblasts (hFOB 1.19 cell line) cultured in the presence of hydroxyapatite-based biomaterials (Maxgraft, Cerabone, Apatos, and Gen-Os). Culturing of the osteoblasts in the presence of hydroxyapatite-based biomaterials resulted in oxidative stress manifested by increased production of reactive oxygen species and decrease of glutathione level and glutathione peroxidase activity. Such redox imbalance leads to lipid peroxidation manifested by an increase of 4-hydroxynonenal level, which is known to influence the growth of bone cells. Vitamins D3 and K were shown to help maintain redox balance and prevent lipid peroxidation in osteoblasts cultured with hydroxyapatite-based biomaterials. The strongest effect was observed for the combination of vitamin D3 and MK-7. Moreover, vitamins promoted growth of the osteoblasts, manifested by increased DNA biosynthesis. Therefore, it is suggested that the use of vitamins D3 and K may protect redox balance and support the growth of osteoblasts affected by hydroxyapatite-based biomaterials.

Prior administration of vitamin K2 improves the therapeutic effects of zoledronic acid in ovariectomized rats by antagonizing zoledronic acid-induced inhibition of osteoblasts proliferation and mineralization

Zoledronic acid (ZA) exerts complex influence on bone by suppressing bone resorption, mostly due to the direct osteoclasts inhibition and uncertain influence on osteoblasts. Vitamin K₂ (VK₂, Menaquinone-4) as an anabolic agent stimulates bone formation via anti-apoptosis in osteoblasts and mild osteoclasts inhibition. Based on these knowledge, the therapeutic effect of the combined or sequential therapy of VK₂ and ZA depends on the influence on the osteoblasts, since both cases exert similar inhibitory effect on osteoclasts. In a series of in vitro studies, we confirmed the protective effect of VK₂ in osteoblasts culture, especially when followed by exposure to ZA, and the proliferation and mineralization inhibition induced by ZA towards osteoblasts. For mechanism study, expression of bcl-2/bax, Runx2 and Sost in cells were examined. For in vivo studies, an osteoporosis animal model was established in rats via ovariectomy (OVX) and subjected to sequential treatment, namely VK₂ followed by ZA. Bone mineral density (BMD) was measured by Dual energy X-ray absorptionmetry (DEXA), morphology and mechanical parameters by micro-computed tomography (micro-CT), mechanical strength by an electro-hydraulic fatigue-testing machine. The bone calcium, hydroxyproline content, blood lipids were evaluated using microplate technique, and the bone surface turnover was evaluated using the fluorescence in corporation method. It was found that VK₂ pretreatment partially prevented the inhibition of bone formation caused by ZA, which was reflected by indices like BMD, bone calcium content and bone strength. The underling mechanisms for protection of VK₂ pretreatment, mainly demonstrated via in vitro studies, included inhibiting apoptosis and depressing Sost expression in osteoblasts, which in turn improved the osteoporosis therapeutic effects of ZA. These findings suggested that pretreatment with VK₂ before ZA therapy might serve a new long-term therapy protocol for osteoporosis.

Vitamin K and Bone Metabolism: A Review of the Latest Evidence in Preclinical Studies

Bone is a metabolically active tissue that renews itself throughout one's life. Cytokines along with several hormonal, nutritional, and growth factors are involved in tightly regulated bone remodeling. Accordingly, vitamin K as a multifunctional vitamin has been recently deemed appreciable as a topic of research as it plays a pivotal role in maintenance of the bone strength, and it has been proved to have a positive impact on the bone metabolism. Vitamin K exerts its anabolic effect on the bone turnover in different ways such as promoting osteoblast differentiation, upregulating transcription of specific genes in osteoblasts, and activating the bone-associated vitamin k dependent proteins which play critical roles in extracellular bone matrix mineralization. There is also credible evidence to support the effects of vitamin k2 on differentiation of other mesenchymal stem cells into osteoblast. The main objective of the present paper is to comprehensively outline the preclinical studies on the properties of vitamin K and its effects on the bone metabolism. The evidence could shed light on further clinical studies to improve osteogenesis in bone graft surgeries.

Effect of vitamin K in bone metabolism and vascular calcification: A review of mechanisms of action and evidences

Osteoporosis is a public health concern associated with an increased risk of bone fractures and vascular calcification. Vitamin K presents unique benefits on these issues, although understudied. The two main forms of vitamin K are phylloquinone (vitamin K₁) and menaquinone (vitamin K₂). In this study, it was especially investigated the action of vitamin K₂ in bones and vessels. Vitamin K₂ has shown to stimulate bone formation by promoting osteoblast differentiation and carboxylation of osteocalcin, and increasing alkaline phosphatase, insulin-like growth factor-1, growth differentiation factor-15, and stanniocalcin 2 levels. Furthermore, vitamin K₂ reduces the pro-apoptotic proteins Fas and Bax in osteoblasts, and decreases osteoclast differentiation by increasing osteoprotegerin and reducing the receptor activator of nuclear factor kappa-B ligand. In blood vessels, vitamin K₂ reduces the formation of hydroxyapatite, through the carboxylation of matrix Gla protein and Gla rich protein, inhibits the apoptosis of vascular smooth muscle cells, by increasing growth arrest-specific gene 6, and reduces the transdifferentiation of vascular smooth muscle cells to osteoblasts. The commonly used dosage of vitamin K₂ in human studies is 45 mg/day and its application can be an interesting strategy in benefitting bone and vascular health, especially to osteoporotic post-menopausal women.

Regulation of bone remodeling by vitamin K2

All living tissues require essential nutrients such as amino acids, fatty acids, carbohydrates, minerals, vitamins, and water. The skeleton requires nutrients for development, maintaining bone mass and density. If the skeletal nutritional requirements are not met, the consequences can be quite severe. In recent years, there has been growing interest in promotion of bone health and inhibition of vascular calcification by vitamin K2. This vitamin regulates bone remodeling, an important process necessary to maintain adult bone. Bone remodeling involves removal of old or damaged bone by osteoclasts and its replacement by new bone formed by osteoblasts. The remodeling process is tightly regulated, when the balance between bone resorption and bone formation shifts to a net bone loss results in the development of osteoporosis in both men and women. In this review, we focus on our current understanding of the effects of vitamin K2 on bone cells and its role in prevention and treatment of osteoporosis.

Does vitamin K2 play a role in the prevention and treatment of osteoporosis for postmenopausal women: a meta-analysis of randomized controlled trials

To identify the role of vitamin K2 for the prevention and treatment of osteoporosis in postmenopausal women, we conducted this meta-analysis of 19 randomized controlled trials. Our results showed that vitamin K2 might play a role in maintaining the bone mineral density and in reducing the incidence of fractures for postmenopausal women with osteoporosis.

INTRODUCTION

Vitamin K2 has been revealed to be effective in the prevention and treatment of osteoporosis in Japan, which was not confirmed in western countries. Thus, we conduct this meta-analysis to verify the hypothesis that vitamin K2 plays a role in the prevention and treatment of osteoporosis for postmenopausal women.

METHODS

We searched the Cochrane Library, Pub Med, EMBASE, and ISI web of knowledge (until December 1, 2013) and reference lists of eligible articles. A meta-analysis of all-including randomized controlled trials was then performed.

RESULTS

Nineteen randomized controlled trials encompassing 6759 participants have met the inclusion criteria. Subgroup analysis of postmenopausal women with osteoporosis revealed a significant improvement of vertebral BMD for both medium-term and long-term results favoring vitamin K2 group (p < 0.00001 and p = 0.0005). However, no significant difference in BMD changes was revealed for the non-osteoporosis subgroup analysis. As for the incidence of fractures, pooled analysis of the seven related studies demonstrated no significant difference in the incidence of fractures favoring vitamin K2 (RR = 0.63, p = 0.08). However, sensitivity analysis by rejecting the study inducing heterogeneity demonstrated a significant difference in the incidence of fractures favoring vitamin K2 (RR = 0.50, p = 0.0005). Significant differences were found in undercarboxylated osteocalcin reduction and osteocalcin increment. The result of adverse reaction analysis showed that vitamin K2 group seemed to have a higher adverse reaction rate (RR = 1.22, p = 0.06).

CONCLUSIONS

This meta-analysis seemed to support the hypothesis that vitamin K2 plays kind of a role in the maintenance and improvement of vertebral BMD and the prevention of fractures in postmenopausal women with osteoporosis. The reduction of undercarboxylated osteocalcin and increment of osteocalcin may have some relation to the process of bone mineralization. However, the effect of vitamin K2 for postmenopausal women without osteoporosis had not been identified. Further high-quality RCTs with large sample size are needed to confirm the role of vitamin K2 in osteoporosis for postmenopausal women.

LC, a novel estrone-rhein hybrid compound, promotes proliferation and differentiation and protects against cell death in human osteoblastic MG-63 cells

Estrogen analogs are promising drugs for postmenopausal osteoporosis, but because of their possible side effects, estrogens which exert their estrogenic effects selectively on bone are desired. Based on our previous studies that rhein had high affinity for the bone mineral, we synthesized estrone-rhein hybrid compounds and confirmed that one of these hybrid compounds, LC, exhibited a selective profile in the bone and prevented bone loss but had no effect on endometrium growth in ovariectomized rats. However, the mechanisms underlying its actions on human bone cells have remained largely unknown. Here we show that LC increases proliferation and differentiation and opposes cisplatin-induced apoptosis in human osteoblastic MG-63 cells containing two estrogen receptor (ER) isoforms. LC promotes proliferation by altering cell cycle distribution whereas LC-mediated survival may be associated with up-regulation of X-linked inhibitor of apoptosis (XIAP) expression. Treatment with the ER antagonist ICI 182,780 abolishes the above actions of LC on osteoblast-derived cells. Using small interfering double-stranded RNAs technology, we further demonstrate that the effects of LC on proliferation and survival are mediated by both ERα and ERβ but those on differentiation primarily by ERα. Moreover, we demonstrate that LC may promote activation of the classic estrogen response element (ERE) pathway through increasing steroid receptor coactivator (SRC)-3 expression. Meanwhile, we find that regulation of osteoblastic proliferation and survival by LC involves Ras/MEK/ERK and PI3K/Akt signaling. Therefore, using rhein for conjugating compounds is a promising method of effectively targeting estrogens to the bone.

Vitamin K suppresses the lipopolysaccharide-induced expression of inflammatory cytokines in cultured macrophage-like cells via the inhibition of the activation of nuclear factor κB through the repression of IKKα/β phosphorylation

Vitamin K is essential for blood coagulation and bone metabolism in mammals. This vitamin functions as a cofactor in the posttranslational synthesis of γ-carboxyglutamic acid (Gla) from glutamic acid residues. However, other functions of vitamin K have been reported recently. We previously found that vitamin K suppresses the inflammatory reaction induced by lipopolysaccharide (LPS) in rats and human macrophage-like THP-1 cells. In this study, we further investigated the mechanism underlying the anti-inflammatory effect of vitamin K by using cultures of LPS-treated human- and mouse-derived cells. All the vitamin K analogues analyzed in our study exhibited varied levels of anti-inflammatory activity. The isoprenyl side chain structures, except geranylgeraniol, of these analogues did not show such activity; warfarin did not interfere with this activity. The results of our study suggest that the 2-methyl-1,4-naphtoquinone ring structure contributes to express the anti-inflammatory activity, which is independent of the Gla formation activity of vitamin K. Furthermore, menaquinone-4, a form of vitamin K₂, reduced the activation of nuclear factor κB (NFκB) and inhibited the phosphorylation of IKKα/β after treatment of cells with LPS. These results clearly show that the anti-inflammatory activity of vitamin K is mediated via the inactivation of the NFκB signaling pathway.

Vitamin K promotes mineralization, osteoblast-to-osteocyte transition, and an anticatabolic phenotype by {gamma}-carboxylation-dependent and -independent mechanisms

The vitamin K family members phylloquinone (vitamin K1) and the menaquinones (vitamin K2) are under study for their roles in bone metabolism and as potential therapeutic agents for skeletal diseases. We have investigated the effects of two naturally occurring homologs, phytonadione (vitamin K1) and menatetrenone (vitamin K2), and those of the synthetic vitamin K, menadione (vitamin K3), on human primary osteoblasts. All homologs promoted in vitro mineralization by these cells. Vitamin K1-induced mineralization was highly sensitive to warfarin, whereas that induced by vitamins K2 and K3 was less sensitive, implying that gamma-carboxylation and other mechanisms, possibly genomic actions through activation of the steroid xenobiotic receptor, are involved in the effect. The positive effect on mineralization was associated with decreased matrix synthesis, evidenced by a decrease from control in expression of type I collagen mRNA, implying a maturational effect. Incubation in the presence of vitamin K2 or K3 in a three-dimensional type I collagen gel culture system resulted in increased numbers of cells with elongated cytoplasmic processes resembling osteocytes. This effect was not warfarin sensitive. Addition of calcein to vitamin K-treated cells revealed vitamin K-dependent deposition of mineral associated with cell processes. These effects are consistent with vitamin K promoting the osteoblast-to-osteocyte transition in humans. To test whether vitamin K may also act on mature osteocytes, we tested the effects of vitamin K on MLO-Y4 cells. Vitamin K reduced receptor activator of NF-kappaB ligand expression relative to osteoprotegerin by MLO-Y4 cells, an effect also seen in human cultures. Together, our findings suggest that vitamin K promotes the osteoblast-to-osteocyte transition, at the same time decreasing the osteoclastogenic potential of these cells. These may be mechanisms by which vitamin K optimizes bone formation and integrity in vivo and may help explain the net positive effect of vitamin K on bone formation.

Assessment of bone mineral density and markers of bone turnover in children under long-term oral anticoagulant therapy

Oral anticoagulants antagonize vitamin K action and potentially impair the carboxylation of osteocalcin, a protein essential for normal bone matrix formation. In the present study, bone mineral density (BMD) and bone turnover markers were evaluated in 23 children under long-term oral anticoagulant therapy. BMD of the lumbar spine was assessed (Dual Energy x-ray Absorptiometry) and reported as z score. Osteoblast [bone alkaline phosphatase, osteocalcin (Gla-Oc), amino-terminal procollagen 1 extension peptide] and osteoclast (urinary calcium and deoxypyridinoline, serum cross-linked C telopeptide) activity markers were measured. Vitamin D {[25(OH) D], parathormone, calcium, phosphorus, magnesium} and vitamin K status [factors II, VII, IX, X, protein C, protein S, undercarboxylated osteocalcin (Glu-Oc)] were determined. The above parameters were also evaluated in 25 healthy controls. Patients presented with higher levels in Glu-Oc, parathormone, and bone resorption markers, lower levels in bone formation markers and 25(OH) D, whereas 52% of them showed signs of osteopenia (-1>BMD z score>-2.5). Statistical analysis demonstrated that anticoagulant therapy was an independent predictor of alterations in Glu-Oc, Gla-Oc, bone alkaline phosphatase, amino-terminal procollagen 1 extension peptide, and serum cross-linked C telopeptide levels. It seems that long-term use of coumarin derivatives may cause osteopenia in children with the risk of developing osteoporosis later in life.

Estrogen and the selective estrogen receptor modulator (SERM) protection against cell death in estrogen receptor alpha and beta expressing U2OS cells

In the current work, we compared the ability of 17beta-estradiol (E2) and the selective estrogen receptor modulators (SERMs), tamoxifen (Tam), raloxifene (Ral) and ospemifene (Osp) to promote the survival of osteoblast-derived cells against etoposide-induced apoptosis. In order to compare the roles of the two estrogen receptor (ER) isotypes, we created a U2OS human osteosarcoma cell line stably expressing either ERalpha (ERalpha) or ERbeta (ERbeta). Transfection with either of the ERs was able to render the U2OS cells sensitive to E2. We show that E2 opposed etoposide-induced apoptosis and that the effect was mediated via both ER isotypes. The ER isotype selective agonists propyl-pyrazole-triol (PPT) and diarylpropionitrile (DPN) had the same effect in U2OS/ERalpha and U2OS/ERbeta cells, respectively. Osp also opposed apoptosis at least in U2OS/ERalpha cells. Tam and Ral were not able to protect against etoposide-induced cell death. In order to evaluate the protective effects of E2 and Osp upon etoposide challenge, we studied the expression of two E2-regulated, osteoblast-produced cytokines, IL-6 and OPG in E2 and SERM-treated U2OS/ERalpha and U2OS/ERbeta cells. Etoposide strongly increased expression of IL-6 and decreased that of OPG. E2 opposed IL-6 increase only in U2OS/ERalpha cells and OPG decrease primarily in ERbeta cells. Osp opposed the effect of etoposide on OPG primarily in U2OS/ERbeta cells but interestingly, it had little effect on IL-6 expression. E2, PPT, DNP and Osp also inhibited etoposide-induced death and cytokine changes in SAOS-2 osteosarcoma cells expressing endogenous ERalpha and ERbeta. Collectively, our results suggest that the osteoblast protective anti-apoptotic effects of E2 are mediated by both ERalpha and ERbeta but those of Osp primarily by ERalpha. In addition, E2 and Osp opposed the etoposide-induced increase of IL-6 and decrease of OPG which changes would increase osteoclastic activity. These anti-resorptive effects of E2 and Osp upon etoposide challenge differed from each other and they seemed to be differentially mediated in ERalpha and ERbeta expressing osteoblast-derived U2OS cells.

Role of macrophages in LPS-induced osteoblast and PDL cell apoptosis

In periradicular lesions and periodontal disease, bacterial invasion leads to chronic inflammation resulting in disruption of the structural integrity of the periodontal ligament and progressive alveolar bone destruction. The pathogenesis of these conditions has been attributed not only to bacterial-induced tissue destruction but also to a defect in periodontal tissue repair. Accumulated data have also shown that lipopolysaccharide (LPS) can directly induce cell death or apoptosis in many cell types, including macrophages, osteoblasts, vascular endothelial cells, hepatocytes and myocytes. The present study hypothesized that bacterial LPS-induced apoptosis in osteoblasts and periodontal ligament fibroblasts (PDL cells) is an important contributing factor to the defect in periodontal tissue repair in periodontal and periapical disease. Macrophages have been shown to respond to bacterial LPS by increasing the production of proinflammatory cytokines. In addition, large numbers of macrophages are present in inflamed periodontal tissue. We speculated that macrophages were a potential candidate cell for mediating apoptosis in osteoblasts and PDL cells in response to bacteria-derived LPS. The macrophage-like cell line, RAW 264.7, was stimulated with LPS, and the conditioned medium was used to treat osteoblasts and PDL cells. Bacterial LPS had no direct apoptotic effect on mouse osteoblasts or PDL cells, whereas the conditioned medium from LPS-activated macrophages was able to induce apoptosis in these cells. To evaluate the contribution of tumor necrosis factor-alpha (TNF-alpha) released from macrophages on osteoblast and PDL cell apoptosis, cells were incubated with conditioned medium from LPS-treated macrophages in the presence and absence of anti-TNF-alpha neutralizing antibodies. TNF-alpha neutralizing antibody pretreatment inhibited the effect of conditioned medium from LPS-treated macrophages on osteoblast and PDL cell apoptosis in a dose-dependent manner. These results suggest that LPS could indirectly induce apoptosis in osteoblasts and PDL cells through the induction of TNF-alpha release from macrophages. These studies provide insight into a potential mechanism by which bacterial-derived LPS could contribute to defective periodontal and bone tissue repair in periodontal and periapical disease.

Regulation of apoptosis in osteoclasts and osteoblastic cells

In postnatal life, the skeleton undergoes continuous remodeling in which osteoclasts resorb aged or damaged bone, leaving space for osteoblasts to make new bone. The balance of proliferation, differentiation, and apoptosis of bone cells determines the size of osteoclast or osteoblast populations at any given time. Bone cells constantly receive signals from adjacent cells, hormones, and bone matrix that regulate their proliferation, activity, and survival. Thus, the amount of bone and its microarchitecture before and after the menopause or following therapeutic intervention with drugs, such as sex hormones, glucocorticoids, parathyroid hormone, and bisphosphonates, is determined in part by effects of these on survival of osteoclasts, osteoblasts, and osteocytes. Understanding the mechanisms and regulation of bone cell apoptosis will enhance our knowledge of bone cell function and help us to develop better therapeutics for the management of osteoporosis and other bone diseases.

Vitamin D inhibits Fas ligand-induced apoptosis in human osteoblasts by regulating components of both the mitochondrial and Fas-related pathways

Apoptosis plays an important role in the regulation of bone turnover. Previously, we showed that 1,25(OH)2D3, the active form of vitamin D, may increase osteoblast survival by inhibiting apoptosis induced by serum deprivation. Human osteoblasts express the Fas receptor on their surface and its interaction with Fas ligand has been closely associated with human osteoblast apoptosis. To investigate the mechanism of 1,25(OH)2D3 inhibition of apoptosis in osteoblasts isolated from human calvaria, cells were exposed to Fas antibody. Visualization of apoptotic cells using annexin V revealed a significant decrease in apoptosis at 48 h in the presence of 1,25(OH)2D3 (14 +/- 4%, P < 0.04) compared with non-treated cells (52 +/- 4%). Furthermore, flow cytometric analysis of TUNEL-labeled osteoblasts showed a significant decrease in apoptotic cells in 1,25(OH)2D3-treated cultures (12 +/- 2%) at 48 h compared with non-treated cultures (44 +/- 3%, P < 0.04). Additionally, cells treated with 1,25(OH)2D3 survived longer as found by MTS analysis. To further explore the mechanism of 1,25(OH)2D3-mediated inhibition of apoptosis, we examined the changes in activation of death domain proteins, cleavage of caspases and mitochondrial regulators of apoptosis by Western blot analysis. A significant inhibition of caspase-8 cleavage and activity in 1,25(OH)2D3-treated cells was observed in conjunction with a decrease in the expression of the proapoptotic protein Bax with a significant increase in the expression of antiapoptotic protein Bcl-2. Furthermore, the levels of p21Cip1/WAF1, which inhibits the cleavage of caspase-8, was found to be highly induced in 1,25(OH)2D3-treated cells. In summary, these results demonstrate that the anti-apoptotic effect of 1,25(OH)2D3 in human osteoblasts after the activation of Fas-ligand is mediated by the regulation of components of both the mitochondrial and Fas-related pathways.

Antagonism between apoptotic (Bax/Bcl-2) and anti-apoptotic (IAP) signals in human osteoblastic cells under vector-averaged gravity condition

A functional disorder associated with weightlessness is well documented in osteoblasts. The apototic features of this disorder are poorly understood. Harmful stress induces apoptosis in cells via mitochondria and/or Fas. The Bax triggers cytochrome c release from mitochondria, which can be blocked by the Bcl-2. Released cytochrome c then activates the initiator caspase, caspase-9, which can be blocked by the anti-apototic (IAP) family of molecules. The effector caspase, caspase-3, finally exerts DNA fragmentation. We conducted this study to examine the apoptotic effects of vector-averaged gravity on normal human osteoblastic cells. Cell culture flasks were incubated on the clinostat, which generated vector-averaged gravity condition (simulated microgravity) for 12, 24, 48, and 96 hours. Upon termination of clinostat cultures, the cell number and cell viability were assessed. DNA fragmentation was analyzed on the agarose-gel electrophoresis. The mRNA levels for Bax, Bcl-2, XIAP, and caspase-3 genes were analyzed by semi-quantitative RT-PCR. Twenty-four hours after starting clinostat rotation, the ratios of Bax/Bcl-2 mRNA levels (indicator of apoptosis) were significantly increased to 136% of the 1G static controls. However, the XIAP mRNA levels (anti-apoptotic molecule) were increased concomitantly to 138% of the 1G static controls. Thus, cell proliferation or cell viability was not affected by vector-averaged gravity. DNA fragmentation was not observed in clinostat group as well as in control group. Finally, the caspase-3 mRNA levels were not affected by vector-averaged gravity. Simulated microgravity might modulate some apoptotic signals upstream the mitochondrial pathway.

Vitamin K2 regulation of bone homeostasis is mediated by the steroid and xenobiotic receptor SXR

Vitamin K2 is a critical nutrient required for blood clotting that also plays an important role in bone formation. Vitamin K2 supplementation up-regulates the expression of bone markers, increases bone density in vivo, and is used clinically in the management of osteoporosis. The mechanism of vitamin K2 action in bone formation was thought to involve its normal role as an essential cofactor for gamma-carboxylation of bone matrix proteins. However, there is evidence that suggests vitamin K2 also has a transcriptional regulatory function. Vitamin K2 bound to and activated the orphan nuclear receptor SXR and induced expression of the SXR target gene, CYP3A4, identifying it as a bona fide SXR ligand. Vitamin K2 treatment of osteosarcoma cells increased mRNA levels for the osteoblast markers bone alkaline phosphatase, osteoprotegerin, osteopontin, and matrix Gla protein. The known SXR activators rifampicin and hyperforin induced this panel of bone markers to an extent similar to vitamin K2. Vitamin K2 was able to induce bone markers in primary osteocytes isolated from wild-type murine calvaria but not in cells isolated from mice deficient in the SXR ortholog PXR. We infer that vitamin K2 is a transcriptional regulator of bone-specific genes that acts through SXR to favor the expression of osteoblastic markers. Thus, SXR has a novel role as a mediator of bone homeostasis in addition to its role as a xenobiotic sensor. An important implication of this work is that a subset of SXR activators may function as effective therapeutic agents for the management of osteoporosis.

High serum levels of menatetrenone in male patients with ossification of the posterior longitudinal ligament

STUDY DESIGN

This work was performed to investigate the role of vitamin K (VK) in the pathogenesis of ossification of posterior longitudinal ligament (OPLL), by analyzing the biochemical markers of the blood samples of OPLL patients and responses of ligament cells derived from OPLL lesion to VK2.

OBJECTIVES

The pathogenesis of OPLL, classified as a form of diffuse idiopathic skeletal hyperostosis, is still unclear. In this study, we investigated the role of menaquinone (VK2) in patients with OPLL (OPLL patients) and the effects of VK2 on ligament cells isolated from OPLL lesion.

METHODS

Serum levels of intact osteocalcin, glu-osteocalcin, MK-4, -7 (VK2 variants) and other minerals in spot blood samples were measured in 24 OPLL patients and in 24 age-matched control patients (non-OPLL patients). The cultured cells isolated from an OPLL patient were treated with MK-4. Alkaline phosphatase (Al-p) activity and osteocalcin release were measured after 2 weeks of culture.

RESULTS

In the clinical study, the serum MK-4 in male OPLL patients was significantly higher than that in male non-OPLL patients. However, among female patients, the difference was not significant. Although the serum osteocalcin in females was significantly higher than that in males, there was no significant difference between the OPLL and non-OPLL groups. In in vitro study, MK-4 did not increase Al-p activity in the ligament cells isolated from nonossified region of OPLL patient. Osteoblastic activity of the cultured cells was not stimulated by MK-4.

CONCLUSION

From these results and previous reports, we propose the possibility of the impediment in VK2 metabolism in OPLL patients. The results also implicate the gender tendency in OPLL, because the difference of serum level of MK-4 in OPLL patients was significant only in male.

TGF-beta1 inhibits multiple caspases induced by TNF-alpha in murine osteoblastic MC3T3-E1 cells

Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine that induces apoptosis in a number of cell systems, including osteoblasts. Transforming growth factor beta1 (TGF-beta1) is an abundant growth factor that is known to stimulate bone formation. This study was designed to examine the role of TGF-beta1 on TNF-alpha-induced apoptosis in murine osteoblastic MC3T3-E1 cells. Total RNA was extracted from MC3T3-E1 cells treated with 20 ng/ml of TNF-alpha, 10 ng/ml of TGF-beta1, or combination, for 6 h. TNF-alpha exerted a variety of effects on the apoptotic gene expression in osteoblasts. Ribonuclease protection assays (RPA) revealed that TNF-alpha upregulated the mRNA levels of caspase-1, -7, -11, -12, and FAS. Western blot analysis showed enhanced processing of caspase-1, -7, -11, and -12, with the appearance of their activated enzymes 24 h after TNF-alpha treatment. In addition, caspase-3-like activity was significantly activated following TNF-alpha treatment. Levels of cleaved poly(ADP-ribose) polymerase and FAS protein were also elevated by TNF-alpha. Finally, Hoechst staining, terminal deoxynucleotidyl-transferase nick-end labeling (TUNEL) assay, and oligonucleosome ELISA all indicated that TNF-alpha induced apoptosis. In contrast, the addition of TGF-beta1 attenuated all of the aforementioned effects of TNF-alpha. Our results demonstrate that TGF-beta1 can decrease TNF-alpha-induced apoptosis in murine osteoblasts at least in part by attenuating TNF-alpha-induced caspase gene expression.

Extrahepatic manifestations of cholestasis

Pruritus, fatigue and metabolic bone disease represent three major extrahepatic manifestations of chronic cholestatic liver disease that considerably affect the patient's quality of life. The present article reviews pathogenetic aspects of and current therapeutic approaches to extrahepatic manifestations of cholestatic liver disease. Pathogenesis of pruritus of cholestasis remains poorly understood. The involvement of putative peripherally acting pruritogens, such as bile acids or endogenous opioids, is being discussed. More recently, central mechanisms, including an increased central opioidergic tone and pertubations in the serotonergic system have been proposed. Treatment of the underlying disease is beneficial also for the control of cholestasis-associated pruritus. Current therapeutic recommendations include ursodeoxycholic acid, cholestyramine, rifampicin and opioid antagonists. Liver transplantation may be indicated when severe pruritus is refractory to medical treatment. Fatigue is being recognized as the most frequent and one of the most disabling complaints in chronic cholestasis. Fatigue is presumably of central origin and its association with other neuropsychiatric disorders (e.g. depression, obsessive-compulsive disorders) is consistent with defective central neurotransmission. No specific therapies are currently available and a healthy lifestyle, regular sleep and avoidance of unnecessary stress and other precipiting factors are recommended. Antidepressant therapy may be warranted in selected patients. Osteopenia and osteoporosis are common in chronic cholestatic liver disease, whereas osteomalacia is rare. The pathophysiology of cholestasis-associated metabolic bone disease is regarded as multifactorial. Therapeutic recommendations include regular exercise, calcium and vitamin D supplementation in late stage disease, hormone replacement therapy in postmenopausal women and bisphosphonates.