High level of serum undercarboxylated osteocalcin in patients with incident fractures during bisphosphonate treatment

Mechanistic Insights and Therapeutic Strategies in Osteoporosis: A Comprehensive Review

Osteoporosis, a metabolic bone disorder characterized by decreased bone mass per unit volume, poses a significant global health burden due to its association with heightened fracture risk and adverse impacts on patients' quality of life. This review synthesizes the current understanding of the pathophysiological mechanisms underlying osteoporosis, with a focus on key regulatory pathways governing osteoblast and osteoclast activities. These pathways include RANK/RANKL/OPG, Wingless-int (Wnt)/β-catenin, and Jagged1/Notch1 signaling, alongside the involvement of parathyroid hormone (PTH) signaling, cytokine networks, and kynurenine in bone remodeling. Pharmacotherapeutic interventions targeting these pathways play a pivotal role in osteoporosis management. Anti-resorptive agents, such as bisphosphonates, estrogen replacement therapy/hormone replacement therapy (ERT/HRT), selective estrogen receptor modulators (SERMs), calcitonin, anti-RANKL antibodies, and cathepsin K inhibitors, aim to mitigate bone resorption. Conversely, anabolic agents, including PTH and anti-sclerostin drugs, stimulate bone formation. In addition to pharmacotherapy, nutritional supplementation with calcium, vitamin D, and vitamin K2 holds promise for osteoporosis prevention. However, despite the availability of therapeutic options, a substantial proportion of osteoporotic patients remain untreated, highlighting the need for improved clinical management strategies. This comprehensive review aims to provide clinicians and researchers with a mechanistic understanding of osteoporosis pathogenesis and the therapeutic mechanisms of existing medications. By elucidating these insights, this review seeks to inform evidence-based decision-making and optimize therapeutic outcomes for patients with osteoporosis.

A comprehensive review on glucocorticoids induced osteoporosis: A medication caused disease

Glucocorticoids (GCs) are steroid hormones that are extensively used in the treatment of autoimmune diseases, inflammation, and cancer. The major ill effect of administering GCs is that it has a deleterious effect on bone, which leads to GC-induced osteoporosis. GC therapy induces bone loss and is associated with the risk of nonvertebral and vertebral fractures, as it works in combination by increasing bone reabsorption and suppressing bone formation during the initial phase of therapy. It is seen and established that GC in excess or in low dose for 3 months or more can be a risk factor for fracture, and the risk increases with an increase in dose and duration of usage. The most common cause of secondary osteoporosis is the administration of GC inside the body to treat various diseases. The degree of bone loss is directly proportional to the GC dose and the exposure duration. The first step is to evaluate the patients' risk factors for the development of glucocorticoids that induce osteoporosis, which include the dose, duration of use, patient age, sex, previous fractures, and other medical conditions.

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.

Analysis of clinical efficacy after PKP in patients of different genders

OBJECTIVE

To investigate the clinical efficacy of Percutaneous Kyphoplasty (PKP) in male and female patients.

METHOD

The clinical data of patients treated with PKP in our hospital from January 2018 to October 2020 were analyzed retrospectively. These patients were divided into female group and male group according to gender differences. The visual analogue scale (VAS) and activity function score (LAS) were recorded before operation, immediately after operation and 1 year after operation, and postoperative complications such as cement leakage and recurrent vertebral fracture were recorded. The above observation indexes between the 2 groups were statistically compared.

RESULTS

A total of 171 patients (118 in female group and 53 in male group) were included. There was no other difference between the 2 groups except that thoracic vertebral fracture was more common in women (P < .05). The VAS of female group and male group were (7.14 ± 0.61) and (7.11 ± 0.51) before operation, (3.05 ± 0.66) and (2.89 ± 0.64) after operation, 1 year after operation (1.10 ± 0.50) and (1.02 ± 0.37). There was no difference in each period between the 2 groups (P > .05). But there was a significant decrease after operation, which was recognized between the 2 groups (P < .05); The activity scores of female group and male group were (3.08 ± 0.48) and (3.07 ± 0.43) before operation, (1.86 ± 0.42) and (1.85 ± 0.50) after operation, 1 year after operation (1.01 ± 0.92) and (1.02 ± 0.14). There was no difference in each period between the 2 groups (P > .05). But there was a significant decrease after operation, which was recognized between the 2 groups (P < .05). Postoperative cement leakage was revealed in 21 cases (12.28%), 16 cases (13.56%) in female group and 5 cases (9.43%) in male group, which was no significant difference between the 2 groups. During the 1-year follow-up, postoperative recurrent vertebral fracture was revealed in 4 cases (2.34%), 2 cases (1.69%) in the female group and 2 case (3.77%) in the male group, which was also no significant difference between the 2 groups.

CONCLUSION

Patients treated with PKP can immediately get pain relief and activity function improvement. PKP is a safe and effective minimally invasive surgery for both female and male patients.

Risk factors for incident vertebral fractures in osteoporosis pharmacotherapy: a 2-year, prospective, observational study

INTRODUCTION

To identify predictors for incident fractures in patients on pharmaceutical treatment for osteoporosis by a secondary analysis of the Japanese Osteoporosis Intervention Trial protocol number 4 (JOINT-04), which was a 2-year, randomized, parallel-group, controlled trial of minodronate and raloxifene in women with primary osteoporosis.

MATERIALS AND METHODS

This was a prospective, observational study using JOINT-04 data, in which biomarkers, such as undercarboxylated osteocalcin (ucOC), N-telopeptide of type 1 collagen, tartrate-resistant acid phosphatase 5b (TRACP-5b), bone alkaline phosphatase, homocysteine, and pentosidine in blood, and physical functions, such as the timed up and go test and one-leg standing test with eyes open (OLST), and the fall risk index, were measured. The relationships of incident morphometric vertebral fractures during the treatment period, as well as prevalent vertebral fractures, and baseline data were analyzed.

RESULTS

The full analysis set of the JOINT-04 included 3247 patients (1623 in the minodronate group and 1624 in the raloxifene group). The hazard ratio (95% confidence interval) for incident vertebral fractures over 2 years of pharmacotherapy, adjusted for confounders, was 0.93 (0.90-0.96) for ucOC, 1.15 (1.08-1.23) for TRACP-5b, 1.02 (1.01-1.03) for pentosidine, 0.91 (0.88-0.94) for the OLST, and 1.27 (1.01-1.60) for the fall risk index, which were all independent predictors.

CONCLUSION

Evaluating fracture risk for patients with osteoporosis considering these potential risk factors for fracture in addition to the established risk factors may be useful when starting pharmaceutical treatment.

The anti-osteoporosis effects of Vitamin K in postmenopausal women

As a common systemically muscular-skeleton disorder in aging, osteoporosis is characterized by the uninterrupted deconstruction in osseous microarchitecture. Osteoporosis can consequently lead to a significantly high risk of osteoporotic fractures, such as osteoporotic vertebral compressive fractures [OVCF] in the spine and osteoporotic femoral neck fractures, which can significantly increase the numbers of mortality and morbidity in aging people, especially in postmenopausal women. In addition, vitamin K has been demonstrated to play a key role in inhibiting osteoporotic fractures among postmenopausal women, but its long-term benefits, potential harms, and effects of the combination between vitamin K and other anti-osteoporosis medicines such as bisphosphonates or teriparatide were just extensively studied. Therefore, the present review aimed to systematically reviewed published literature on the role of vitamin K in the treatment of osteoporosis. We currently, via multiple queries strategy, searched the relevant literature in Cochrane and PubMed from January 2010 to December 2019. Subsequently, we conducteda systematic review according to the standard guideline of Preferred Reporting Item for Systematic Reviews and Meta-Analyses [PRISMA]. Finally, ten relevant works of literature met our current criteria for inclusion, and then we followed the PRISMA guideline and systematically reviewed each study by the categorized data sources and analytical approaches in each study, meanwhile set up variables and defined each study outcomes.

Genetic Variation in VKORC1 and Risk for Osteoporosis

BACKGROUND AND AIMS

The vitamin K epoxide reductase complex subunit 1 (VKORC1) plays an important role in bone development and bone metabolism by influencing the vitamin K cycle. The aim of this study was to investigate the association between VKORC1 gene polymorphisms and bone mineral density and the risk of osteoporosis.

MATERIALS AND METHODS

We determined VKORC1 gene polymorphisms (rs9923231 and rs9934488) by using polymerase chain reaction-restriction and Sanger sequencing method in 606 postmenopausal women including 288 osteoporosis patients and 318 healthy controls.

RESULTS

No significant differences were observed in the rs9934488 polymorphisms between the osteoporosis group and controls. Subgroup analyses also indicated no positive result. VKORC1 rs9923231 polymorphism increased the risk of osteoporosis in the homozygous and allelic models. A significant correlation was observed in a subgroup of the elderly (age ≥55 years). Additionally, the genotypes of the rs9923231 polymorphism were significantly associated with low body mass index, and T-score, but not with age, serum calcium, or phosphorus.

CONCLUSIONS

In conclusion, VKORC1 rs9923231 polymorphism is a genetic contributor to osteoporosis risk and it should be confirmed in large well-designed studies.

Molecular Mechanisms and Emerging Therapeutics for Osteoporosis

Osteoporosis is the most common chronic metabolic bone disease. It has been estimated that more than 10 million people in the United States and 200 million men and women worldwide have osteoporosis. Given that the aging population is rapidly increasing in many countries, osteoporosis could become a global challenge with an impact on the quality of life of the affected individuals. Osteoporosis can be defined as a condition characterized by low bone density and increased risk of fractures due to the deterioration of the bone architecture. Thus, the major goal of treatment is to reduce the risk for fractures. There are several treatment options, mostly medications that can control disease progression in risk groups, such as postmenopausal women and elderly men. Recent studies on the basic molecular mechanisms and clinical implications of osteoporosis have identified novel therapeutic targets. Emerging therapies targeting novel disease mechanisms could provide powerful approaches for osteoporosis management in the future. Here, we review the etiology of osteoporosis and the molecular mechanism of bone remodeling, present current pharmacological options, and discuss emerging therapies targeting novel mechanisms, investigational treatments, and new promising therapeutic approaches.

Beneficial Effects of Vitamin K Status on Glycemic Regulation and Diabetes Mellitus: A Mini-Review

Type 2 diabetes mellitus is a chronic disease that is characterized by hyperglycemia, insulin resistance, and dysfunctional insulin secretion. Glycemic control remains a crucial contributor to the progression of type 2 diabetes mellitus as well as the prevention or delay in the onset of diabetes-related complications. Vitamin K is a fat-soluble vitamin that plays an important role in the regulation of the glycemic status. Supplementation of vitamin K may reduce the risk of diabetes mellitus and improve insulin sensitivity. This mini-review summarizes the recent insights into the beneficial effects of vitamin K and its possible mechanism of action on insulin sensitivity and glycemic status, thereby suppressing the progression of diabetes mellitus.

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.

Molecular-Based Treatment Strategies for Osteoporosis: A Literature Review

Osteoporosis is an unavoidable public health problem in an aging or aged society. Anti-resorptive agents (calcitonin, estrogen, and selective estrogen-receptor modulators, bisphosphonates, anti-receptor activator of nuclear factor κB ligand antibody along with calcium and vitamin D supplementations) and anabolic agents (parathyroid hormone and related peptide analogs, sclerostin inhibitors) have major roles in current treatment regimens and are used alone or in combination based on the pathological condition. Recent advancements in the molecular understanding of bone metabolism and in bioengineering will open the door to future treatment paradigms for osteoporosis, including antibody agents, stem cells, and gene therapies. This review provides an overview of the molecular mechanisms, clinical evidence, and potential adverse effects of drugs that are currently used or under development for the treatment of osteoporosis to aid clinicians in deciding how to select the best treatment option.

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.

Comparison of concurrent treatment with vitamin K2 and risedronate compared with treatment with risedronate alone in patients with osteoporosis: Japanese Osteoporosis Intervention Trial-03

The aim of this study was to investigate the efficacy of concurrent treatment with vitamin K₂ and risedronate compared with treatment with risedronate alone in patients with osteoporosis and to explore subsets of patients for which concurrent treatment is particularly efficacious. Women with osteoporosis aged 65 years or older were recruited from 123 institutes in Japan and allocated to take either vitamin K₂ (45 mg/day) and risedronate (2.5 mg/day or 17.5 mg/week) or risedronate (2.5 mg/day or 17.5 mg/week) alone. The primary end point was the incidence of any fracture (vertebral and nonvertebral). The secondary end points were bone mineral density, height, undercarboxylated osteocalcin concentration, quality of life, and safety. Over a 2-year follow-up, vertebral or nonvertebral fractures occurred in 117 or 22 sites respectively among 931 patients in the risedronate and vitamin K₂ group and in 104 or 26 sites respectively among 943 patients in the risedronate alone group. The rates of any incident fracture were similar between the two groups (incidence rate ratio 1.074, 95 % confidence interval 0.811-1.422, p = 0.62), implying that the primary end point was not met. There were no differences in the degree of increase in bone mineral density between the two groups. Undercarboxylated osteocalcin concentration decreased from 5.81 ± 3.93 ng/mL to 2.59 ± 1.52 ng/mL at 6 months in the risedronate and vitamin K₂ group, whereas the change in the risedronate alone group was minimal (from 5.96 ± 4.36 ng/mL to 4.05 ± 3.40 ng/mL at 6 months) (p < 0.01). The treatment discontinuation rate was higher in the risedronate and vitamin K₂ group than in the risedronate alone group (10.0 % vs 6.7 %). No unknown adverse drug reactions were reported. In conclusion, concurrent treatment with vitamin K₂ and risedronate was not efficacious compared with monotherapy with risedronate in terms of fracture prevention.

Level of serum undercarboxylated osteocalcin correlates with bone quality assessed by calcaneal quantitative ultrasound sonometry in young Japanese females

The diagnostic criteria of osteoporosis were established based on bone mineral density (BMD). Therefore, BMD measured by dual energy X-ray absorptiometry has been recognized as the gold standard to diagnose osteoporosis. However, discrepancies between fracture risk and BMD have been recognized. Bone is composed of collagen scaffold reinforced by hydroxyapatite. Both protein scaffold and hydroxyapatite are involved in bone quality. BMD may indicate bone mineralization but potentially fail to assess the protein scaffold. Vitamin K contributes to bone mineralization and as a protein scaffold. A deficiency of vitamin K upregulates the level of serum undercarboxylated osteocalcin (ucOC), and serum ucOC correlates with fracture risk. However, direct association of ucOC and bone quality has not been demonstrated. For the present study, a total of 49 healthy young Japanese female college students underwent calcaneal; quantitative ultrasound sonometry (QUS) and determination of serological bone metabolic markers. QUS parameters were significantly correlated with serum 25-hydroxyvitamin D (25-OH-D) concentrations (P<0.05). A significant negative correlation was also identified between log transformed serum ucOC concentrations [Ln(ucOC)] and a QUS parameter, speed of sound (SOS) (P<0.05). Stepwise multiple regression analysis indicated that Ln(ucOC) was an independent determinant of SOS, and 25-OH-D was an independent determinant of the other two QUS parameters, transmission index (TI) and synthetic parameter osteo-sono-assessment index. As vitamin D is involved in bone mineralization, TI may reflect the mineralization. Correlation of vitamin K status, indicated by ucOC, with SOS may clarify the correlation between vitamin K status and bone quality, although the material factors that connect them have not been identified.

Comparison of the effects of 12 months of monthly minodronate monotherapy and monthly minodronate combination therapy with vitamin K2 or eldecalcitol in patients with primary osteoporosis

The aim of this observational, nonrandomized study was to compare the effects of 12 months of monthly minodronate (MIN; 50 mg/month) monotherapy and MIN combination therapy with vitamin K2 (VK; 45 mg/day) or eldecalcitol (ELD; 0.75 μg/day) in treatment-naïve patients with primary osteoporosis. Patients (n = 193; 178 postmenopausal women and 15 men; mean age 71.6 years) were treated with (1) MIN monotherapy (n = 63), (2) MIN plus VK combination therapy (n = 50), or (3) MIN plus ELD combination therapy (n = 80) for 12 months. Changes in bone mineral density (BMD) and the levels of serum bone turnover markers were monitored. No significant difference was observed in baseline BMD among the three groups. After 12 months, BMD increased by 2.93, 4.65, and 6.55 % in the lumbar spine, 0.66, 2.57, and 3.42 % in the total hip, and 0.05, 2.06, and 3.58 % in the femoral neck in groups 1, 2, and 3, respectively. The BMD increase induced by MIN plus ELD combination therapy was significantly greater than that induced by MIN monotherapy in the lumbar spine (P = 0.0002), total hip (P = 0.003), and femoral neck (P = 0.004), and also that induced by MIN plus VK combination therapy in the lumbar spine (P = 0.03). MIN plus ELD combination therapy compared with MIN monotherapy resulted in a greater decrease in serum procollagen type I N-terminal propeptide levels (-37.4 % vs -54.6 %; P = 0.001) and tartrate-resistant acid phosphatase isoform 5b levels (-41.1 % vs -52.9 %; P = 0.009) at 3 months, and a greater decrease in procollagen type I N-terminal propeptide levels (-64.3 % vs -50.3 %; P = 0.03) and a decrease in intact parathyroid hormone levels (-12.3 % vs 14.0 %; P = 0.01) at 12 months. Combination therapy with MIN and VK or ELD for 12 months showed additive effects in decreasing the levels of bone turnover markers compared with MIN monotherapy, whereas MIN plus ELD combination therapy resulted in the highest BMD increase compared with MIN monotherapy and MIN plus VK combination therapy.

Increased undercarboxylated osteocalcin/intact osteocalcin ratio in patients undergoing hemodialysis

Serum undercarboxylated osteocalcin (ucOC)/intact osteocalcin (iOC) ratio increased >1.0 in the patients undergoing hemodialysis, particularly in those with high bone turnover state. Consequently, serum ucOC/iOC ratio might lose its significance as a bone metabolic marker to indicate vitamin K deficiency in hemodialysis patients.

INTRODUCTION

Serum intact osteocalcin (iOC), undercarboxylated OC (ucOC), and the ucOC/iOC ratio are considered clinically relevant indices in pre-dialysis chronic kidney disease (CKD) and hemodialysis (HD) patients, despite their accumulation in uremic serum.

METHODS

Serum iOC and ucOC were measured along with serum intact parathyroid hormone (iPTH), bone alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase (TRACP)-5b in 89 pre-dialysis CKD and 189 HD patients.

RESULTS

Serum iOC and ucOC showed significantly negative correlations with estimated glomerular filtration rate in pre-dialysis CKD patients, although serum ucOC/iOC ratio did not correlate. Serum ucOC was significantly greater in HD patients than in pre-dialysis CKD patients, while serum iOC did not differ significantly, resulting in serum ucOC/iOC ratio >1.0 in 135 (71.4%) out of 189 HD patients. HD patients with high serum ucOC/iOC ratio (>1.0) had a significantly younger age and significantly higher values of body mass index, serum creatinine, albumin, phosphate, iPTH, and TRACP-5b than those with low ucOC/iOC ratio (≤ 1.0). The baseline iPTH and P1NP correlated with the changes of the ucOC/iOC ratio during the 2 days of the inter-dialytic period. Multivariate analysis showed that log [ucOC/iOC] in HD patients was significantly associated with log [iPTH], log [BAP], or log [TRACP-5b].

CONCLUSIONS

Serum ucOC/iOC ratio >1.0 was observed in as high as 71.4% of HD patients, preferentially with high bone turnover state, in comparison with pre-dialysis CKD patients. These data suggested that serum ucOC/iOC ratio might lose its significance as a bone metabolic marker to indicate vitamin K deficiency in HD patients.

A four-season molecule: osteocalcin. Updates in its physiological roles

Osteocalcin (OC) is the main non-collagenous hydroxyapatite-binding protein synthesized by osteoblasts, odontoblasts, and hypertrophic chondrocytes. It has a regulatory role in mineralization and it is considered a marker of bone cell metabolism. Recent findings evidenced new extra-skeletal roles for OC, depicting it as a real hormone. OC shares many functional features with the common hormones, such as tissue-specific expression, circadian rhythm, and synthesis as a pre-pro-molecule. However, it has some peculiar features making it a unique molecule: OC exists in different forms based on the degree of carboxylation. Indeed, OC has three glutamic acid residues, in position 17, 21, and 24, which are subject to γ-carboxylation, through the action of a vitamin K-dependent γ-glutamyl carboxytransferase. The degree of carboxylation, and thus the negative charge density, determines the affinity for the calcium ions deposited in the extracellular matrix of the bone. The modulation of the carboxylation could, thus, represent the mechanism by which the body controls the circulating levels, and hence the hormonal function, of OC. There are evidences linking OC, and the bone metabolism, with a series of endocrine (glucose metabolism, energy metabolism, fertility) physiological (muscle activity) and pathological functions (ectopic calcification). Aim of this review is to give a full overview of the physiological roles of OC by collecting the newest experimental findings on this intriguing molecule.

Vitamin K: an old vitamin in a new perspective

The topic of "Vitamin K" is currently booming on the health products market. Vitamin K is known to be important for blood coagulation. Current research increasingly indicates that the antihaemorrhagic vitamin has a considerable benefit in the prevention and treatment of bone and vascular disease. Vitamin K1 (phylloquinone) is more abundant in foods but less bioactive than the vitamin K2 menaquinones (especially MK-7, menaquinone-7). Vitamin K compounds undergo oxidation-reduction cycling within the endoplasmic reticulum membrane, donating electrons to activate specific proteins via enzymatic gamma-carboxylation of glutamate groups before being enzymatically reduced. Along with coagulation factors (II, VII, IX, X, and prothrombin), protein C and protein S, osteocalcin (OC), matrix Gla protein (MGP), periostin, Gas6, and other vitamin K-dependent (VKD) proteins support calcium homeostasis, inhibit vessel wall calcification, support endothelial integrity, facilitate bone mineralization, are involved in tissue renewal and cell growth control, and have numerous other effects. The following review describes the history of vitamin K, the physiological significance of the K vitamers, updates skeletal and cardiovascular benefits and important interactions with drugs.

Vitamin K₂ therapy for postmenopausal osteoporosis

Vitamin K may play an important role in the prevention of fractures in postmenopausal women with osteoporosis. Menatetrenone is the brand name of a synthetic vitamin K₂ that is chemically identical to menaquinone-4. The present review study aimed to clarify the effect of menatetrenone on the skeleton in postmenopausal women with osteoporosis, by reviewing the results of randomized controlled trials (RCTs) in the literature. RCTs that investigated the effect of menatetrenone on bone mineral density (BMD), measured by dual-energy X-ray absorptiometry and fracture incidence in postmenopausal women with osteoporosis, were identified by a PubMed search for literature published in English. Eight studies met the criteria for RCTs. Small RCTs showed that menatetrenone monotherapy decreased serum undercarboxylated osteocalcin (ucOC) concentrations, modestly increased lumbar spine BMD, and reduced the incidence of fractures (mainly vertebral fracture), and that combined alendronate and menatetrenone therapy enhanced the decrease in serum ucOC concentrations and further increased femoral neck BMD. This review of the literature revealed positive evidence for the effects of menatetrenone monotherapy on fracture incidence in postmenopausal women with osteoporosis. Further studies are required to clarify the efficacy of menatetrenone in combination with bisphosphonates against fractures in postmenopausal women with osteoporosis.

Design of a randomized clinical trial of concurrent treatment with vitamin K2 and risedronate compared to risedronate alone in osteoporotic patients: Japanese Osteoporosis Intervention Trial-03 (JOINT-03)

Concurrent treatments with bisphosphonates and vitamin K are promising given that bisphosphonates possibly interfere with vitamin K activation. This is a prospective, multi-center, open-labeled, randomized trial of the efficacy of concurrent treatment with vitamin K2 and risedronate compared with risedronate alone and to explore subsets of patients for which concurrent treatment is particularly efficacious (trial identification number UMIN000000991). Inclusion criteria are women who meet the criteria for pharmacological therapy for osteoporosis, aged ≥65 years, have any of pre-specified risk factors, can walk unassisted, and are able to answer questionnaires. Exclusion criteria are prior warfarin use, secondary osteoporosis or non-osteoporotic metabolic bone diseases, contraindication for vitamin K2 and risedronate, hyper- or hypoparathyroidism, mental disorders, prevalent vertebral fracture at ≥6 sites, severe degenerative spinal deformation between T4 and L4, serious heart, liver, or kidney disease, or bisphosphonate use within the previous 6 months. Patients were recruited from 123 institutes between January 2008 and February 2010, and allocated to vitamin K2 (45 mg/day) and risedronate (2.5 mg/day or 17.5 mg/week) or risedronate alone (2.5 mg/day or 17.5 mg/week) groups. Primary endpoint is a vertebral or non-vertebral fracture. Secondary endpoints are bone mineral density, height, undercarboxylated osteocalcin, JOQOL, EQ-5D and safety. A sample size of 910 subjects per group and 2-year follow-up will provide 80 % power to detect 35 % risk reduction for fracture, with a two-sided significance level of 5 %. Subgroup analysis stratified to adjustment factors for random allocation, body mass index, 25-hydroxyvitamin D, estimated glomerular filtration rate, grade of vertebral fracture, JOQOL, EQ-5D, and co-morbidity is pre-specified.

Effects of risedronate alone or combined with vitamin K2 on serum undercarboxylated osteocalcin and osteocalcin levels in postmenopausal osteoporosis

Risedronate decreases osteoporotic fracture incidence; however, its effects remain unclear in elderly osteoporotic patients. Vitamin K mediates carboxylation of osteocalcin (OC), and high undercarboxylated osteocalcin (ucOC) levels indicate vitamin K deficiency and increased osteoporotic fracture risk. We aimed to evaluate the effects of risedronate alone or combined with vitamin K2 on serum ucOC, OC, and incidence of vertebral fractures in elderly osteoporotic patients. A total of 101 women with postmenopausal osteoporosis aged >60 years were randomly stratified into two groups-R group (n = 51), treated with risedronate alone; and R + K group (n = 50), treated with risedronate and vitamin K2. Serum ucOC, OC and incidence of vertebral fractures were evaluated before treatment and at 6 and 12 months post-treatment. Decreased ucOC rates at 6 and 12 months were not significant between groups. However, at 6 and 12 months, decreased OC rates in the R group (p < 0.01 and 0.05, respectively) were significantly higher than in the R + K group, and ucOC/OC change rates in the R group (p < 0.05 and 0.001, respectively) were significantly lower than in the R + K group. Vertebral fracture incidence was not significantly different between the groups at 6 and 12 months. ucOC levels in patients with incident vertebral fractures were significantly higher than in patients without incident vertebral fractures in the R group at 6 months (p < 0.05). Although no significant difference was observed for ucOC decrease rate and incidence of vertebral fractures between treatments, ucOC levels in patients with incident vertebral fractures were significantly greater than in patients without when using risedronate alone.

Menatetrenone for the treatment of osteoporosis

INTRODUCTION

The effect of the anti-osteoporosis medicine, menatetrenone (vitamin K(2); menaquinone-4) on the skeleton remains a matter of controversy. The objective of the present review study was to evaluate the effect of menatetrenone on the skeleton of postmenopausal women, men and glucocorticoid-treated patients.

METHODS

PubMed was used to search the literature for randomized controlled trials (RCTs), meta-analyses and systematic reviews. Thirteen RCTs, one meta-analysis and one systematic review were available for analysis.

RESULTS

Except for one large Japanese RCT (Phase IV trial: Osteoporotic Fracture (OF) study, n = 4378), RCTs with small sample size showed non-significant or modest effect on bone mineral density (BMD) in postmenopausal women and patients treated with glucocorticoid, positive effect on hip geometry in postmenopausal women and efficacy against fractures (mainly vertebral fractures) in postmenopausal women with osteoporosis. A post hoc analysis of the OF study showed that the incidence of vertebral fractures decreased in postmenopausal women with at least five vertebral fractures. A meta-analysis study, but not a systematic review study, showed efficacy against vertebral and non-vertebral fractures mainly in postmenopausal women with osteoporosis. There was no available evidence for men with osteoporosis.

CONCLUSION

The present review of the literature revealed some evidence of a positive effect of menatetrenone on the skeleton of postmenopausal women and in patients treated with glucocorticoid.

EXPERT OPINION

Menatetrenone is considered to be a second-line medicine for postmenopausal osteoporotic women with an increased risk for vertebral fractures.

Serum undercarboxylated osteocalcin level increases with 48 weeks of teriparatide treatment in pre-treated elderly rheumatoid arthritis patients who use anti-resorptive drugs

AIM

The serum undercarboxylated osteocalcin (ucOC) level, a biochemical bone marker of vitamin K insufficiency, is often affected by anti-osteoporosis drugs. There have been no reports regarding the relationship between ucOC and teriparatide.

SUBJECTS AND METHODS

We conducted a prospective observational study of 26 female rheumatoid arthritis (RA) patients. The patients were divided into 3 groups: those who underwent a direct switch from anti-resorptive drugs to teriparatide (12 cases), those who started teriparatide without pre-treatment (5 cases), and the control patients (9 cases). The median age (interquartile range) of the patients in each group was 75 (67-77), 82 (78-84), and 69 (62-80) yr, respectively. All patients, except controls, received 48-week treatments of teriparatide. We analyzed the median 48-week changes from baseline of the serum ucOC levels with the Steel-Dwass method.

RESULTS

The median change from baseline in the direct switch group was higher than that in other groups (p<0.05).

CONCLUSIONS

The serum ucOC levels increased with treatment of teriparatide in elderly RA patients, especially when the patients received pre-treatment.

Post-menopausal women with rheumatoid arthritis who are treated with raloxifene or alendronate or glucocorticoids have lower serum undercarboxylated osteocalcin levels

BACKGROUND

Serum undercarboxylated osteocalcin (ucOC) is a biochemical bone marker of vitamin K insufficiency. It had been reported that bone resorption inhibitors tend to decrease the serum ucOC level in patients with primary osteoporosis. In rheumatoid arthritis (RA) patients, these results have never been reported.

AIM

We investigated risk factors which could change serum ucOC level in post-menopausal women with RA (no.=100).

SUBJECTS AND METHODS

Twenty patients received no bone resorption inhibitor (control), 30 received raloxifene (RLX), while 50 received alendronate (ALN). This cross-sectional study was limited to patients with low RA disease activity (Disease Activity Score-28 ≤3.2). We measured serum ucOC, and the data were analyzed by multivariable analysis, including ucOC and the other variables.

RESULTS

Scheffe's F test demonstrated a significant difference in serum ucOC levels between controls and the RLX group (p<0.01), and between controls and the ALN group (p<0.01). Serum ucOC levels were low in both treated groups. An adjusted multivariate analysis was performed for the variables: bone resorption inhibitor use, serum alkaline phosphatase, glucocorticoid dose, age, estimated glomerular filtration rate and matrix metalloproteinase 3. As a result, serum ucOC inversely correlated with bone resorption inhibitor use (p<0.01) and oral glucocorticoid dose (p<0.01), which were independent risk factors of lowering ucOC.

CONCLUSIONS

Bone resorption inhibitors and glucocorticoids were independent risk factors for lowering serum ucOC levels in post-menopausal RA patients.

Effect of GGCX gene polymorphism on the responses of serum undercarboxylated osteocalcin and bone turnover markers after treatment with vitamin K2 (menatetrenone) among postmenopausal Thai women

The purpose of this study was to evaluate the influence of gamma-glutamyl transferase (GGCX) gene polymorphisms on the response of serum undercarboxylated osteocalcin (ucOC) and bone turnover markers 3 months after treatment with menatetrenone. One hundred and forty postmenopausal Thai women were enrolled and assigned to receive 45 mg/day treatment of menatetrenone (MK-4) concurrently with calcium 1.2 g and vitamin D 400 IU for 3 months. Demographic characteristics, GGCX genotyping, serum bone turnover markers and ucOC levels were obtained from all participants at baseline. We evaluated the reduction of ucOC at 3 months and the reduction of beta-CTx and P1NP at 1 and 3 months. The responses were compared between the different genotypes of GG and GA + AA groups. There was a significant reduction of serum ucOC, beta-CTx and P1NP from the baseline at 3 months (p < 0.001) though there was no significant difference between genotypes (GG vs. GA + AA; p > 0.05). Nonetheless, a subgroup analysis of postmenopausal women who 65 years of age or over (N = 37) revealed a significant difference between the two groups in the reduction of ucOC. Menatetrenone significantly reduced serum ucOC as well as beta-CTX and P1NP from the baseline. GGCX polymorphism appeared to have an influence over the reduction of ucOC especially in older women (age ≥65). Furthermore, the groups which have "A" allele trend to being more efficient in reducing the serum ucOC level than the group which does not have it.

Three-year experience with combined treatment with alendronate and alfacalcidol in Japanese patients with severe bone loss and osteoporotic fracture

Purpose:

Combined treatment with alendronate and alfacalcidol is more useful to increase bone mineral density (BMD) than alendronate or alfacalcidol alone. A retrospective study was conducted to investigate the 3-year outcome of combined treatment with alendronate and alfacalcidol in patients with severe bone loss (BMD ≤ 50% of the young adult mean) and osteoporotic fracture.

Methods:

Thirty-four patients (six men and 28 postmenopausal women) with primary or secondary osteoporosis who had been treated with alendronate and alfacalcidol for more than 3 years were analyzed. The lumbar spine or total hip BMD and bone turnover markers were monitored, and the incidence of osteoporotic fractures was assessed.

Results:

The urinary level of cross-linked N-terminal telopeptides of type I collagen and serum level of alkaline phosphatase significantly decreased (−42.5% at 3 months and −18.9% at 3 years), and the lumbar spine BMD, but not the total hip BMD, significantly increased (14.8% at 3 years), compared with the baseline values. However, the incidence of vertebral and nonvertebral fractures was 26.5% and 2.9%, respectively, suggesting a high incidence of vertebral fractures.

Conclusion:

The results of the present study suggest that combined treatment with alendronate and alfacalcidol may be useful to reduce bone turnover and increase the lumbar spine BMD in patients with severe bone loss and osteoporotic fracture. However, its efficacy against vertebral fractures appears not to be sufficient. Thus, anabolic agents such as teriparatide should be taken into consideration as first-line drugs in patients with severe osteoporosis.

The effect of acute exercise on undercarboxylated osteocalcin in obese men

SUMMARY

The purpose of this study was to examine if the reduction in glucose post-exercise is mediated by undercarboxylated osteocalcin (unOC). Obese men were randomly assigned to do aerobic or power exercises. The change in unOC levels was correlated with the change in glucose levels post-exercise. The reduction in glucose post-acute exercise may be partly related to increased unOC.

INTRODUCTION

Osteocalcin (OC) in its undercarboxylated (unOC) form may contribute to the regulation of glucose homeostasis. As exercise reduces serum glucose and improves insulin sensitivity in obese individuals and individuals with type 2 diabetes (T2DM), we hypothesised that this benefit was partly mediated by unOC.

METHODS

Twenty-eight middle-aged (52.4 ± 1.2 years, mean ± SEM), obese (BMI = 32.1 ± 0.9 kg m(-2)) men were randomly assigned to do either 45 min of aerobic (cycling at 75% of VO(2peak)) or power (leg press at 75% of one repetition maximum plus jumping sequence) exercises. Blood samples were taken at baseline and up to 2 h post-exercise.

RESULTS

At baseline, unOC was negatively correlated with glucose levels (r = -0.53, p = 0.003) and glycosylated haemoglobin (HbA1c) (r = -0.37, p = 0.035). Both aerobic and power exercises reduced serum glucose (from 7.4 ± 1.2 to 5.1 ± 0.5 mmol L(-1), p = 0.01 and 8.5 ± 1.2 to 6.0 ± 0.6 mmol L(-1), p = 0.01, respectively). Aerobic exercise significantly increased OC, unOC and high-molecular-weight adiponectin, while power exercise had a limited effect on OC and unOC. Overall, those with higher baseline glucose and HbA1c had greater reductions in glucose levels after exercise (r = -0.46, p = 0.013 and r = -0.43, p = 0.019, respectively). In a sub-group of obese people with T2DM, the percentage change in unOC levels was correlated with the percentage change in glucose levels post-exercise (r = -0.51, p = 0.038).

CONCLUSIONS

This study reports that the reduction in serum glucose post-acute exercise (especially aerobic exercise) may be partly related to increased unOC.