Low plasma phylloquinone concentration is associated with high incidence of vertebral fracture in Japanese women

Vitamin K: Infection, Inflammation, and Auto-Immunity

Vitamin K (VK) comprises a group of substances with chlorophyll quinone bioactivity and exists in nature in the form of VK1 and VK2. As its initial recognition originated from the ability to promote blood coagulation, it is known as the coagulation vitamin. However, based on extensive research, VK has shown potential for the prevention and treatment of various diseases. Studies demonstrating the beneficial effects of VK on immunity, antioxidant capacity, intestinal microbiota regulation, epithelial development, and bone protection have drawn growing interest in recent years. This review article focuses on the mechanism of action of VK and its potential preventive and therapeutic effects on infections (eg, asthma, COVID-19), inflammation (eg, in type 2 diabetes mellitus, Alzheimer's disease, Parkinson's disease, cancer, aging, atherosclerosis) and autoimmune disorders (eg, inflammatory bowel disease, type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis). In addition, VK-dependent proteins (VKDPs) are another crucial mechanism by which VK exerts anti-inflammatory and immunomodulatory effects. This review explores the potential role of VK in preventing aging, combating neurological abnormalities, and treating diseases such as cancer and diabetes. Although current research appoints VK as a therapeutic tool for practical clinical applications in infections, inflammation, and autoimmune diseases, future research is necessary to elucidate the mechanism of action in more detail and overcome current limitations.

Vitamin D Metabolites: Analytical Challenges and Clinical Relevance

Recent research activities have provided new insights in vitamin D metabolism in various conditions. Furthermore, substantial progress has been made in the analysis of vitamin D metabolites and related biomarkers, such as vitamin D binding protein. Liquid chromatography tandem mass spectrometric (LC-MS/MS) methods are capable of accurately measuring multiple vitamin D metabolites in parallel. Nevertheless, only 25(OH)D and the biologically active form 1,25(OH)2D are routinely measured in clinical practice. While 25(OH)D remains the analyte of choice for the diagnosis of vitamin D deficiency, 1,25(OH)2D is only recommended in a few conditions with a dysregulated D metabolism. 24,25(OH)2D, free and bioavailable 25(OH)D, and the vitamin D metabolite ratio (VMR) have shown promising results, but technical pitfalls in their quantification, limited clinical data and the lack of reference values, impede their use in clinical practice. LC-MS/MS is the preferred method for the measurement of all vitamin D related analytes as it offers high sensitivity and specificity. In particular, 25(OH)D and 24,25(OH)2D can accurately be measured with this technology. When interpreted together, they seem to provide a functional measure of vitamin D metabolism beyond the analysis of 25(OH)D alone. The determination of VDBP, free and bioavailable 25(OH)D is compromised by unresolved analytical issues, lacking reference intervals and insufficient clinical data. Therefore, future research activities should focus on analytical standardization and exploration of their clinical value. This review provides an overview on established and new vitamin D related biomarkers including their pathophysiological role, preanalytical and analytical aspects, expected values, indications and influencing conditions.

Vitamin K and cardiovascular complications in CKD patients

Vitamin K, well known for its role in coagulation, encompasses two major subgroups: Vitamin K1 is exclusively synthesized by plants, whereas vitamin K2 mostly originates from bacterial synthesis. Vitamin K serves as a cofactor for the enzyme γ-glutamyl carboxylase, which carboxylates and thereby activates various vitamin K dependent proteins. Several vitamin K-dependent proteins are synthesized in bone but the role of vitamin K for bone health in CKD patients, in particular the prevention of osteoporosis is still not firmly established. Here we focus on another prominent action of vitamin K, in particular vitamin K2, namely the activation of matrix Gla protein (MGP), the most potent inhibitor of cardiovascular calcifications. Multiple observational studies link relative vitamin K deficiency or low intake to cardiovascular calcification progress, morbidity and mortality. Patients with advanced chronic kidney disease (CKD) are particularly vitamin K deficient, in part because of dietary restrictions but possibly also due to impaired endogenous recycling of vitamin K. At the same time this population is characterized by markedly accelerated cardiovascular calcifications and mortality. High dose dietary supplementation with vitamin K2, in particular the most potent form menaquinone-7 (MK7), can potently reduce circulating levels of dephosphorylated uncarboxylated, i.e. inactive MGP in patients with end stage kidney disease. However, despite this compelling data basis, several randomized controlled trials with high dose MK7 supplements in patients with advanced CKD have failed to confirm cardiovascular benefits. Here we discuss potential reasons and solutions for this.

The Role of Vitamin K in Humans: Implication in Aging and Age-Associated Diseases

As human life expectancy is rising, the incidence of age-associated diseases will also increase. Scientific evidence has revealed that healthy diets, including good fats, vitamins, minerals, or polyphenolics, could have antioxidant and anti-inflammatory activities, with antiaging effects. Recent studies demonstrated that vitamin K is a vital cofactor in activating several proteins, which act against age-related syndromes. Thus, vitamin K can carboxylate osteocalcin (a protein capable of transporting and fixing calcium in bone), activate matrix Gla protein (an inhibitor of vascular calcification and cardiovascular events) and carboxylate Gas6 protein (involved in brain physiology and a cognitive decline and neurodegenerative disease inhibitor). By improving insulin sensitivity, vitamin K lowers diabetes risk. It also exerts antiproliferative, proapoptotic, autophagic effects and has been associated with a reduced risk of cancer. Recent research shows that protein S, another vitamin K-dependent protein, can prevent the cytokine storm observed in COVID-19 cases. The reduced activation of protein S due to the pneumonia-induced vitamin K depletion was correlated with higher thrombogenicity and possibly fatal outcomes in COVID-19 patients. Our review aimed to present the latest scientific evidence about vitamin K and its role in preventing age-associated diseases and/or improving the effectiveness of medical treatments in mature adults ˃50 years old.

Vitamin K Nutrition and Bone Health

Vitamin K is essential for blood coagulation and plays an important role in extrahepatic metabolism, such as in bone and blood vessels, and in energy metabolism. This review discusses the assessment of vitamin K sufficiency and the role of vitamin K in bone health. To elucidate the exact role of vitamin K in other organs, accurate tools for assessing vitamin K deficiency or insufficiency are crucial. Undercarboxylated vitamin K-dependent protein levels can be measured to evaluate tissue-specific vitamin K deficiency/insufficiency. Vitamin K has genomic action through steroid and xenobiotic receptor (SXR); however, the importance of this action requires further study. Recent studies have revealed that the bone-specific, vitamin K-dependent protein osteocalcin has a close relationship with energy metabolism through insulin sensitivity. Among the organs that produce vitamin K-dependent proteins, bone has attracted the most attention, as vitamin K deficiency has been consistently associated with bone fractures. Although vitamin K treatment addresses vitamin K deficiency and is believed to promote bone health, the corresponding findings on fracture risk reduction are conflicting. We also discuss the similarity of other vitamin supplementations on fracture risk. Future clinical studies are needed to further elucidate the effect of vitamin K on fracture risk.

Vitamin K deficiency, evaluated with higher serum ucOC, was correlated with poor bone status in women

BACKGROUND

An increase in serum undercarboxylated osteocalcin concentrations suggests vitamin K deficiency. Clinical intervention studies suggested that the vitamin K supplementation might contribute to preventing bone loss in postmenopausal women. Evidence on the relationship between serum undercarboxylated osteocalcin (ucOC) levels and bone parameters of quantitative ultrasound (QUS) is limited. We examined the correlation between serum ucOC concentrations and bone status as measured by QUS among middle-aged and older Japanese men and women.

METHODS

The subjects were community-dwelling men (n = 358) and women (n = 503) aged ≥ 40 years in Japan. Heel QUS parameters, including the stiffness index, speed of sound, and broadband ultrasound attenuation, were measured. Serum ucOC concentrations were measured by electrochemiluminescence immunoassay. Grip strength was measured in the dominant hand. Information on alcohol drinking, current smoking, exercise, and menopause in women was collected.

RESULTS

Serum ucOC concentrations were significantly associated with age in both sexes. Serum ucOC concentrations in men were higher at ≥ 80 years than those in the age groups of 40-49, 50-59, and 60-69 years. Serum ucOC concentrations in women were higher in the age groups of 50-59 and 60-69 years than those at 40-49 years. Partial correlation analysis adjusting for covariates (age, body mass index, grip strength, alcohol drinking, current smoking, and exercise in men; age, body mass index, grip strength, alcohol drinking, current smoking, exercise, and menopause in women) showed that serum ucOC concentrations were negatively significantly correlated with all QUS parameters in women. Serum ucOC concentrations were not correlated with them in men.

CONCLUSIONS

Vitamin K deficiency, evaluated with higher serum ucOC, was correlated with poor bone status in women.

A new LC-MS assay for the quantitative analysis of vitamin K metabolites in human urine

Vitamin K (VK), in both its phylloquinone and menaquinone forms, has been hypothesized to undergo ω- and β-oxidation on its hydrophobic side chain in order to generate the observed urinary metabolites, K acid I and K acid II, which are excreted primarily as glucuronide conjugates. Synthetic standards of K acid I, K acid II, and a putative intermediate metabolite, menaquinone (MK)1 ω-COOH, were used to develop and optimize a new atmospheric pressure negative chemical ionization LC-MS/MS assay for the quantitation of these compounds in urine from untreated individuals and subjects treated with a high dose VK supplement. VK catabolites were extracted from urine, deconjugated, and converted to their methyl ester derivatives using previously reported methodology. The assay showed a high degree of sensitivity, with limits of detection below 10-50 fmol of metabolite per milliliter of urine, as well as an inter-assay precision of 8-12%. Metabolite standards provided unambiguous evidence for MK1 ω-COOH as a new human urinary metabolite of VK. This assay provides a minimally invasive, highly sensitive, and specific alternative for monitoring VK status in humans.

Multiple vitamin deficiencies additively increase the risk of incident fractures in Japanese postmenopausal women

The associations of multiple vitamin deficiencies on incident fractures were uncertain, the relationships between serum vitamin markers and incident bone fractures were investigated in Japanese postmenopausal women. The number of deficiencies was additively associated with incident fracture after adjustment for possible confounding factors including the treatment of osteoporosis.

INTRODUCTION

To evaluate the associations of multiple vitamin deficiencies on incident fractures, the relationships between serum vitamin markers and incident bone fractures were investigated in Japanese postmenopausal women.

METHODS

This analysis used a subset of the ongoing cohort maintained by a primary care institution. Inclusion criteria of the present study were postmenopausal women aged ≥ 50 years, without vitamin supplementation and secondary osteoporosis. Baseline serum concentrations of 25-hydroxyvitamin D (25(OH)D), undercarboxylated osteocalcin (ucOC), and homocysteine (Hcy) were measured to assess vitamin D, vitamin K, and vitamin B, respectively. Since 25(OH) D positively relates to vitamin D, ucOC and Hcy negatively relate to vitamin K and vitamin B nutrients, respectively, the subjects with lower (25(OH)D) or higher (ucOC or Hcy) values than each median value was defined as subjects with the corresponding vitamin deficiency. Subjects were divided into four groups according to the number of deficiency: no deficiency, single deficiency, double deficiencies, and triple deficiencies. Relationships between the vitamin deficiencies and incident fractures were evaluated by Cox regression analysis.

RESULTS

A total of 889 subjects were included in this analysis; their mean and SD age was 68.3 ± 9.5 years, and the follow-up period was 6.3 ± 5.1 years. The numbers of subjects in the four groups were 139 (15.6%), 304 (34.2%), 316 (35.5%), and 130 (14.6%) for the groups with no, single, double, and triple deficiencies, respectively. Incident fractures were observed in 264 subjects (29.7%) during the observation period. The number of deficiencies was significantly associated with incident fracture (hazard ratio 1.25, 95% confidence interval 1.04-1.50, P = 0.018) after adjustment for possible confounding factors including the treatment of osteoporosis.

CONCLUSION

Accumulation of vitamin deficiencies was related to incident fractures.

α-Tocopherol Intake Decreases Phylloquinone Concentration in Bone but Does Not Affect Bone Metabolism in Rats

Previous studies have shown that α-tocopherol intake lowers phylloquinone (PK) concentration in some extrahepatic tissues in rats. The study's aim was to clarify the effect of α-tocopherol intake on vitamin K concentration in bone, as well as the physiological action of vitamin K. Male Wistar rats were divided into 4 groups. Over a 3-mo period, the K-free group was fed a vitamin K-free diet with 50 mg RRR-α-tocopherol/kg, the E-free group was fed a diet containing 0.75 mg PK/kg without vitamin E, the control group was fed a diet containing 0.75 mg PK/kg with 50 mg RRR-α-tocopherol/kg, and the E-excess group was fed a diet containing 0.75 mg PK/kg with 500 mg RRR-α-tocopherol/kg. PK concentration in the liver was higher in E-excess rats than in E-free rats, was lower in the tibias of control rats than in those of E-free rats, and was lower in E-excess rats than in control rats. Menaquinone-4 (MK-4) concentration in the liver was higher in E-excess rats than in E-free and control rats. However, MK-4 concentrations in the tibias of E-free, control, and E-excess rats were almost the same. Blood coagulation activity was lower in K-free rats than in the other rats but was not affected by the level of α-tocopherol intake. Additionally, dietary intake of PK and α-tocopherol did not affect uncarboxylated-osteocalcin concentration in the serum, femur density, or expression of the genes related to bone resorption and formation in the femur. These results suggest that α-tocopherol intake decreases PK concentration in bone but does not affect bone metabolism in rats.

Relation Between Circulating Vitamin K1 and Osteoporosis in the Lumbar Spine in Syrian Post-Menopausal Women

Background:

In the past two decades, Vitamin K has been receiving more attention due to its role in bone health and metabolism. The bone mineral density does not remain steady with age, particularly declining after menopause.

Objective:

This study is aimed to investigate the relationship between bone mineral density and serum vitamin K1 levels in post-menopausal women, and to evaluate serum vitamin K1 levels as a potential biomarker for postmenopausal osteoporosis.

Methods:

Serum levels of vitamin k1 were measured in 23 postmenopausal osteoporotic women, and in 15 postmenopausal healthy control women using a standardized Enzyme-Linked Immune Sorbent Assay (ELISA) kit. Bone mineral density BMD was assessed at the lumbar spine.

Results:

The mean serum vitamin k1 level was significantly lower in the postmenopausal osteoporotic women group than in the normal control group (mean=0.794 vs3.61ng/ml, P< 0.0001), and serum vitamin k1 concentration was positively correlated with lumbar spine BMD among postmenopausal osteoporotic women (R=0.533, p = 0.009), and in postmenopausal healthy control (R=0.563, p = 0.02).

Diagnostic sensitivity and specificity of vitamin k1 for osteoporosis were 90% and 98%, respectively (cut-off value: 0.853 ng/ml). The area under the ROC curve (AUC) value for vitamin k1 was 0.984 the odd ratio result was 18.66.

Conclusion:

Our results suggest that vitamin K1 may contribute to maintain bone mineral density. Vitamin K1 may have a role in diagnosing post-menopausal osteoporosis. Vitamin K1 may be a valuable diagnostic as well as therapeutic marker in post-menopausal osteoporosis.

Vitamin K homologs as potential biomarkers for disease activity in patients with rheumatoid arthritis

The aim of this study was to evaluate the possible role of vitamin K homologs as potential biomarkers for disease activity in patients with rheumatoid arthritis (RA). In this study, 42 patients with RA and 40 healthy controls were enrolled. Serum levels of vitamin K homologs were measured using a high-performance liquid chromatography-fluorescence method. Different biochemical and clinical markers for disease activity were measured and correlated with serum levels of vitamin K homologs. There were no significant differences between RA patients and healthy subjects in demographic data. Patients with RA showed significantly higher levels of biochemical markers compared with healthy subjects (p < 0.001). These markers included rheumatoid factor (RF), anticyclic citrullinated polypeptide (anti-CCP), undercarboxylated osteocalcin (ucOC), matrix metalloproteinase (MMP-3), C-reactive protein (CRP), and disease activity score assessing 28 joints with erythrocyte sedimentation rate (DAS28-ESR). In addition, serum levels of vitamin K homologs were reduced in RA patients, and the levels of menaquinone-4 (MK-4) and menaquinone-7 (MK-7) were moderately to strongly inversely correlated with the clinical articular features in RA patients, whereas phylloquinone (PK) levels were weakly correlated. Serum levels of MK-4, MK-7 and PK were strongly inversely correlated with ucOC, MMP-3 and DAS28-ESR in RA patients. In contrast, serum levels of MK-4, MK-7 and PK were weakly correlated with CRP, RF and anti-CCP. These results suggest that serum levels of vitamin K homologs may be considered as potential biomarkers for disease activity. In addition, the results confirm the role of vitamin K deficiency in the etiology of RA.

Vitamin K and osteoporosis: Myth or reality?

Vitamin K is a liposoluble vitamin. The predominant dietary form, phylloquinone or vitamin K1, is found in plants and green vegetables; whereas menaquinone, or vitamin K2, is endogenously synthesized by intestinal bacteria and includes several subtypes that differ in side chain length. Aside from its established role in blood clotting, several studies now support a critical function of vitamin K in improving bone health. Vitamin K is in fact required for osteocalcin carboxylation that in turn regulates bone mineral accretion; it seems to promote the transition of osteoblasts to osteocytes and also limits the process of osteoclastogenesis. Several observational and interventional studies have examined the relationship between vitamin K and bone metabolism, but findings are conflicting and unclear. This systematic review aims to investigate the impact of vitamin K (plasma levels, dietary intake, and oral supplementation) on bone health with a particular interest in bone remodeling, mineral density and fragility fractures.

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.

Osteoporosis in East Asia: Current issues in assessment and management

The greatest burden of hip fractures around the world is expected to occur in East Asia, especially China. However, there is a relative paucity of information on the epidemiology and burden of fractures in East Asia. Osteoporosis is greatly under-diagnosed and under-treated, even among the highest-risk subjects who have already suffered fractures. The accessibility to bone densitometry, the awareness of the disease by professionals and the public, and the use and reimbursement of drugs are some of the areas which need improvement especially. Cost-effective analysis on screening strategy and intervention thresholds based on local epidemiology data and economic status are available only in Japan. In addition, clinical risk factor models for the assessment of fracture probability may be ethnic specific. Further research is needed to develop a cost-effective risk assessment strategy to identify high-risk individuals for screening and treatment based on local data. Moreover, inadequate calcium and vitamin D intake is still an issue faced by this region.

A combination of low serum concentrations of vitamins K1 and D is associated with increased risk of hip fractures in elderly Norwegians: a NOREPOS study

The present study investigated the risk of incident hip fractures according to serum concentrations of vitamin K1 and 25-hydroxyvitamin D in elderly Norwegians during long-term follow-up. The results showed that the combination of low concentrations of both vitamin D and K1 provides a significant risk factor for hip fractures.

INTRODUCTION

This case-cohort study aims to investigate the associations between serum vitamin K1 and hip fracture and the possible effect of 25-hydroxyvitamin D (25(OH)D) on this association.

METHODS

The source cohort was 21,774 men and women aged 65 to 79 years who attended Norwegian community-based health studies during 1994-2001. Hip fractures were identified through hospital registers during median follow-up of 8.2 years. Vitamins were determined in serum obtained at baseline in all hip fracture cases (n = 1090) and in a randomly selected subcohort (n = 1318). Cox proportional hazards regression with quartiles of serum vitamin K1 as explanatory variable was performed. Analyses were further performed with the following four groups as explanatory variable: I: vitamin K1 ≥ 0.76 and 25(OH)D ≥ 50 nmol/l, II: vitamin K1 ≥ 0.76 and 25(OH)D < 50 nmol/l, III: vitamin K1 < 0.76 and 25(OH)D ≥ 50 nmol/l, and IV: vitamin K1 < 0.76 and 25(OH)D < 50 nmol/l.

RESULTS

Age- and sex-adjusted analyses revealed an inverse association between quartiles of vitamin K1 and the risk of hip fracture. Further, a 50 % higher risk of hip fracture was observed in subjects with both low vitamin K1 and 25(OH)D compared with subjects with high vitamin K1 and 25(OH)D (HR 1.50, 95 % CI 1.18-1.90). The association remained statistically significant after adjusting for body mass index, smoking, triglycerides, and serum α-tocopherol. No increased risk was observed in the groups low in one vitamin only.

CONCLUSION

Combination of low concentrations of vitamin K1 and 25(OH)D is associated with increased risk of hip fractures.

Concepts and Controversies in Evaluating Vitamin K Status in Population-Based Studies

A better understanding of vitamin K's role in health and disease requires the assessment of vitamin K nutritional status in population and clinical studies. This is primarily accomplished using dietary questionnaires and/or biomarkers. Because food composition databases in the US are most complete for phylloquinone (vitamin K1, the primary form in Western diets), emphasis has been on phylloquinone intakes and associations with chronic diseases. There is growing interest in menaquinone (vitamin K2) intakes for which the food composition databases need to be expanded. Phylloquinone is commonly measured in circulation, has robust quality control schemes and changes in response to phylloquinone intake. Conversely, menaquinones are generally not detected in circulation unless large quantities are consumed. The undercarboxylated fractions of three vitamin K-dependent proteins are measurable in circulation, change in response to vitamin K supplementation and are modestly correlated. Since different vitamin K dependent proteins are implicated in different diseases the appropriate vitamin K-dependent protein biomarker depends on the outcome under study. In contrast to other nutrients, there is no single biomarker that is considered a gold-standard measure of vitamin K status. Most studies have limited volume of specimens. Strategic decisions, guided by the research question, need to be made when deciding on choice of biomarkers.

The Two Sides of Vitamin E Supplementation

Vitamin E is a lipid-soluble antioxidant that inhibits lipid peroxidation by scavenging reactive oxygen species, and it is thought to protect against the aging process. Indeed, it is one of the most popular supplements in the US. However, recent studies have revealed that vitamin E has dual effects on the aging process. We discovered that α-tocopherol, the major form of vitamin E in the body, stimulates osteoclast fusion and bone resorption as well as induces an osteoporosis-like phenotype in rodents. Clinical intervention trials have also demonstrated that supplementation with vitamin E is neutral or even harmful for preventing age-related diseases in humans. Therefore, the role of vitamin E as an 'anti-ager' has been called into question. This review outlines the present understanding of the role of vitamin E in age-related disease prevention.

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.

The effects of α-tocopherol on bone: a double-edged sword?

Recent studies have found conflicting evidence on the role of α-tocopherol (αTF) on bone health. This nonsystematic review aimed to summarize the current evidence on the effects of αTF on bone health from cell culture, animal, and human studies in order to clarify the role of αTF on bone health. Our review found that αTF exerted beneficial, harmful or null effects on bone formation cells. Animal studies generally showed positive effects of αTF supplementation on bone in various models of osteoporosis. However, high-dose αTF was possibly detrimental to bone in normal animals. Human studies mostly demonstrated a positive relationship between αTF, as assessed using high performance liquid chromatography and/or dietary questionnaire, and bone health, as assessed using bone mineral density and/or fracture incidence. Three possible reasons high dosage of αTF can be detrimental to bone include its interference with Vitamin K function on bone, the blocking of the entry of other Vitamin E isomers beneficial to bone, and the role of αTF as a prooxidant. However, these adverse effects have not been shown in human studies. In conclusion, αTF may have a dual role in bone health, whereby in the appropriate doses it is beneficial but in high doses it may be harmful to bone.

Low-dose vitamin K2 (MK-4) supplementation for 12 months improves bone metabolism and prevents forearm bone loss in postmenopausal Japanese women

Menaquinone-4 (MK-4) administered at a pharmacological dosage of 45 mg/day has been used for the treatment of osteoporosis in Japan. However, it is not known whether a lower dose of MK-4 supplementation is beneficial for bone health in healthy postmenopausal women. The aim of this study was to examine the long-term effects of 1.5-mg daily supplementation of MK-4 on the various markers of bone turnover and bone mineral density (BMD). The study was performed as a randomized, double-blind, placebo-controlled trial. The participants (aged 50-65 years) were randomly assigned to one of two groups according to the MK-4 dose received: the placebo-control group (n = 24) and the 1.5-mg MK-4 group (n = 24). The baseline concentrations of undercarboxylated osteocalcin (ucOC) were high in both groups (>5.1 ng/ml). After 6 and 12 months, the serum ucOC concentrations were significantly lower in the MK-4 group than in the control group. In the control group, there was no significant change in serum pentosidine concentrations. However, in the MK-4 group, the concentration of pentosidine at 6 and 12 months was significantly lower than that at baseline. The forearm BMD was significantly lower after 12 months than at 6 months in the control group. However, there was no significant decrease in BMD in the MK-4 group during the study period. These results suggest that low-dose MK-4 supplementation for 6-12 months improved bone quality in the postmenopausal Japanese women by decreasing the serum ucOC and pentosidine concentrations, without any substantial adverse effects.

Menaquinones, bacteria, and the food supply: the relevance of dairy and fermented food products to vitamin K requirements

Vitamin K exists in the food supply as phylloquinone, a plant-based form and as menaquinones (MKs), a collection of isoprenologues mostly originating from bacterial synthesis. Although multiple bacterial species used as starter cultures for food fermentations synthesize MK, relatively little is known about the presence and distribution of MK in the food supply and the relative contribution of MK to total dietary vitamin K intake. Dairy products may be a predominant source of dietary MK in many regions of the world, and there is recent interest in enhancing the MK content of dairy products through identification and selection of MK-producing bacteria in dairy fermentations. This interest is increased by emerging evidence that current dietary recommendations based on the classic role of vitamin K as an enzyme cofactor for coagulation proteins may not be optimal for supporting vitamin K requirements in extrahepatic tissues and that MK may have unique bioactivity beyond that as an enzyme cofactor. Observational studies have reported favorable associations between MK intake and bone and cardiovascular health. Although randomized trials have provided some evidence to support the beneficial effects of MK on bone, the evidence to date is not definitive, and randomized trials have not yet examined MK intake in relation to cardiovascular outcomes. Food production practices provide a means to enhance dietary MK availability and intake. However, parallel research is needed to optimize these production practices, develop comprehensive food MK content databases, and test hypotheses of unique beneficial physiological roles of MK beyond that achieved by phylloquinone.

Osteocalcin: skeletal and extra-skeletal effects

Osteocalcin (OC) is a non-collagenous, vitamin K-dependent protein secreted in the late stage of osteoblasts differentiation. The presence of the three residues of γ-carbossiglutamatic acid, specific of the active form of OC protein, allows the protein to bind calcium and consequently hydroxyapatite. The osteoblastic OC protein is encoded by the bone γ-carbossiglutamate gene whose transcription is principally regulated by the Runx2/Cbfa1 regulatory element and stimulated by vitamin D(3) through a steroid-responsive enhancer sequence. Even if data obtained in literature are controversial, the dual role of OC in bone can be presumed as follows: firstly, OC acts as a regulator of bone mineralization; secondly, OC regulates osteoblast and osteoclast activity. Recently the metabolic activity of OC, restricted to the un-carboxylated form has been demonstrated in osteoblast-specific knockout mice. This effect is mediated by the regulation of pancreatic β-cell proliferation and insulin secretion and adiponectin production by adipose tissue and leads to the regulation of glucose metabolism and fat mass. Nevertheless, clinical human studies only demonstrated the correlation between OC levels and factors related to energy metabolism. Thus further investigations in humans are required to demonstrate the role of OC in the regulation of human energy metabolism. Moreover, it is presumable that OC also acts on blood vessels by inducing angiogenesis and pathological mineralization. This review highlights the recent studies concerning skeletal and extra-skeletal effects of OC.

The role of menaquinones (vitamin K₂) in human health

Recent reports have attributed the potential health benefits of vitamin K beyond its function to activate hepatic coagulation factors. Moreover, several studies have suggested that menaquinones, also known as vitamin K2, may be more effective in activating extra-hepatic vitamin K-dependent proteins than phylloquinone, also known as vitamin K1. Nevertheless, present dietary reference values (DRV) for vitamin K are exclusively based on phylloquinone, and its function in coagulation. The present review describes the current knowledge on menaquinones based on the following criteria for setting DRV: optimal dietary intake; nutrient amount required to prevent deficiency, maintain optimal body stores and/or prevent chronic disease; factors influencing requirements such as absorption, metabolism, age and sex. Dietary intake of menaquinones accounts for up to 25% of total vitamin K intake and contributes to the biological functions of vitamin K. However, menaquinones are different from phylloquinone with respect to their chemical structure and pharmacokinetics, which affects bioavailability, metabolism and perhaps impact on health outcomes. There are significant gaps in the current knowledge on menaquinones based on the criteria for setting DRV. Therefore, we conclude that further investigations are needed to establish how differences among the vitamin K forms may influence tissue specificities and their role in human health. However, there is merit for considering both menaquinones and phylloquinone when developing future recommendations for vitamin K intake.

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.

A single measurement of serum phylloquinone is an adequate indicator of long-term phylloquinone exposure in healthy older adults

Assessment of long-term phylloquinone exposure is challenging in studies investigating vitamin K in health. Data are equivocal as to whether a single measurement of circulating phylloquinone would be adequate. The primary purpose of the present study was to validate the use of a single measurement of serum phylloquinone as a surrogate for long-term phylloquinone exposure in healthy older adults. Using data from the Québec Longitudinal Study on Nutrition and Successful Aging, the objectives were to: 1) determine the reproducibility of circulating phylloquinone over 2 y (n = 234); 2) calculate how a single measurement would rank or classify individuals and attenuate the regression coefficient between circulating phylloquinone and a health outcome; and 3) investigate the association of a single measurement of serum phylloquinone with long-term phylloquinone intakes assessed over the year prior to the blood draw (n = 228). The variance analysis based on 2 blood samples showed a fair to good reproducibility for serum phylloquinone (intra-class correlation = 0.49). The correlation coefficient between the ranking of individuals based on a single measurement of circulating phylloquinone and the "true" ranking would be 0.70. The multiple regression analysis showed that long-term phylloquinone intake was the strongest predictor of serum phylloquinone (t = 4.94; P < 0.001). The partial correlation coefficient (r = 0.32) was comparable with those reported in studies where blood sampling and diet recording were juxtaposed and/or multiple blood samples were used. The present study provides evidence that the use of a single measurement of circulating phylloquinone is adequate for assessing long-term phylloquinone exposure in healthy older adults.

Evaluation of bone, nutrition, and physical function in Shorinji Kempo athletes

The objectives of this study were to reveal the proportion of Shorinji Kempo athletes who had suffered fractures related to sports activities, and to evaluate bone mass, bone turnover, nutritional status, and physical function in these athletes. A medical examination was carried out for 16 Shorinji Kempo collegiate athletes. Seven athletes (43.8%) had experienced a sports-related traumatic fracture during Shorinji Kempo practice. Four athletes (25.0%) had a lower speed of sound (% young adult mean < 100%), and five athletes (31.3%) had higher levels of urinary cross-linked N-terminal telopeptides of type 1 collagen (a bone turnover marker) than the age-adjusted standard values. All the athletes had a lower daily calcium intake than the adequate intake, 12 (75.0%) had a lower daily vitamin D intake, and 15 (93.8%) had a lower daily vitamin K intake. Significant positive correlations were found between the vertical jump height, and the daily energy, and protein intakes. Results suggest that fractures are a common injury in Shorinji Kempo athletes, and that some Shorinji Kempo athletes need to improve their bone mass, bone metabolism, and nutritional status in order to strengthen bone and improve physical function.

No association between dietary vitamin K intake and fracture risk in chinese community-dwelling older men and women: a prospective study

Data on the association between dietary vitamin K intake and fracture risk are limited among Chinese. This study examined such an association in community-dwelling elderly in Hong Kong. We present data from 2,944 subjects (1,605 men, 1,339 women) who participated in a prospective cohort study. Baseline dietary intakes of energy, protein, calcium, vitamin D, and vitamin K were assessed using a food-frequency questionnaire. Data on incident hip fracture and nonvertebral fracture during a median of 6.9 follow-up years were collected from a hospital database. Cox regression analyses were performed with adjustments for age, education attainment, smoking status, alcohol use, body mass index, hip bone mineral density, physical activity, use of calcium supplement, and energy-adjusted nutrient intakes. There were 29 (1.8 %) men and 19 (1.4 %) women with incident hip fractures and 97 (6.0 %) men and 88 (6.6 %) women with nonvertebral fractures. The median (interquartile range) of dietary vitamin K intake was 241.8 (157.5-360.8) and 238.9 (162.4-343.6) μg/day in men and women, respectively. Similar dietary vitamin K intakes were observed between subjects with hip or nonvertebral fractures and subjects without hip or nonvertebral fractures. In both men and women, dietary vitamin K intake was not associated with fracture risks at all measured sites in either crude or adjusted models. In Chinese community-dwelling elderly, hip or nonvertebral fracture risk was not associated with dietary vitamin K intake. The high dietary vitamin K intake of the studied group may have limited the ability to detect the association between vitamin K intake and fracture risk.

Effects of vitamin K on the morphometric and material properties of bone in the tibiae of growing rats

Suboptimal vitamin K nutriture is evident during rapid growth. We aimed to determine whether vitamin K(2) (menaquinone-4 [MK-4]) supplementation is beneficial to bone structure and intrinsic bone tissue properties in growing rats. Male Wistar rats (5 weeks old) were assigned to either a control diet (n = 8) or an MK-4-supplemented diet (22 mg d(-1) kg(-1) body weight, n = 8). After a 9-week feeding period, we determined the serum concentration ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin and the urinary deoxypyridinoline level. All rats were then euthanized, and their tibiae were analyzed by micro-computed tomography for trabecular architecture and synchrotron radiation micro-computed tomography for cortical pore structure and mineralization. Fourier transform infrared microspectroscopy and a nanoindentation test were performed on the cortical midlayers of the anterior and posterior cortices to assess bone tissue properties. Neither body weight nor tibia length differed significantly between the 2 groups. Dietary MK-4 supplementation decreased the ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin but did not affect deoxypyridinoline, indicating a positive effect on bone formation but not bone resorption. Trabecular volume fraction and thickness were increased by MK-4 (P < .05). Neither the cortical pore structure nor mineralization was affected by MK-4. On the other hand, MK-4 increased mineral crystallinity, collagen maturity, and hardness in both the anterior and posterior cortices (P < .05). These data indicate the potential benefit of MK-4 supplementation during growth in terms of enhancing bone quality.

Effect of vitamin K on bone mineral density: a meta-analysis of randomized controlled trials

A number of randomized controlled trials (RCTs) examining the role of vitamin K on bone mineral density (BMD) have yielded inconsistent results. We performed a meta-analysis of these trials to assess the effect of vitamin K on BMD. We searched MEDLINE, EMBASE and CENTRAL for relevant studies of RCTs examining the role of vitamin K on BMD. Data on participants, interventions, and outcomes were extracted and the quality of all included trials assessed. Primary outcomes for analysis were absolute changes in BMD (mg/cm(2)) at the lumbar spine and femoral neck. Relative changes (percentage change) in BMD at the lumbar spine were also assessed. Vitamin K supplementation was shown to be efficacious in increasing BMD at the lumbar spine but not the femoral neck. The weighted mean difference (WMD) in BMD absolute change was 21.60 mg/cm(2) [95% confidence interval (CI) 3.63, 39.56] at the lumbar spine and 0.25 mg/cm(2) (95% CI -2.64, 3.14) at the femoral neck. The WMD in BMD relative change was 1.27% (95% CI 0.47, 2.06) at the lumbar spine and 0.17 (95% CI -0.21, 0.54) at the femoral neck. Subgroup analysis revealed that ethnic difference, gender, and vitamin K type were associated with variable effects on BMD at the lumbar spine. The modest overall treatment effects for vitamin K on BMD observed in this review may be biased and should be interpreted with caution. Further studies are required to address factors relating to the observed effects of vitamin K on BMD.

Vitamin K, osteoporosis and degenerative diseases of ageing

The function of vitamin K is to serve as a co-factor during the post-translational carboxylation of glutamate (Glu) residues into γ-carboxyglutamate (Gla) residues. The vital importance of the Gla-proteins essential for normal haemostasis is well recognized. During recent years, new Gla-containing proteins have been discovered and the vitamin K-dependent carboxylation is also essential for their function. It seems, however, that our dietary vitamin K intake is too low to support the carboxylation of at least some of these Gla-proteins. According to the triage theory, long-term vitamin K inadequacy is an independent, but modifiable risk factor for the development of degenerative diseases of ageing including osteoporosis and atherosclerosis.

Vitamin K supplement along with vitamin D and calcium reduced serum concentration of undercarboxylated osteocalcin while increasing bone mineral density in Korean postmenopausal women over sixty-years-old

There are inconsistent findings on the effects of vitamin K on bone mineral density (BMD) and undercarboxylated osteocalcin (UcOC). The present intervention study evaluated the effect in subjects over 60-yr-old. The vitamin K group (vitamin K + vitamin D + calcium supplement; 15 mg of vitamin K2 [menatetrenone] three times daily, 400 IU of vitamin D once a day, and 315 mg of calcium twice daily) and the control group (vitamin D + calcium supplement) were randomly assigned. During the six months of treatment, seventy eight women participated (38 in the vitamin K group and 40 in the control group) and 45 women completed the study. The baseline characteristics of study participants did not differ between the vitamin K and the control groups. In a per protocol analysis after 6 months, L3 bone mineral density has increased statistically significantly in the vitamin K group compared to the control group (0.01 ± 0.03 g/cm(2) vs -0.008 ± 0.04 g/cm(2), P = 0.049). UcOC concentration was also significantly decreased in the vitamin K group (-1.6 ± 1.6 ng/dL vs -0.4 ± 1.1 ng/dL, P = 0.008). In conclusion, addition of vitamin K to vitamin D and calcium supplements in the postmenopausal Korean women increase the L3 BMD and reduce the UcOC concentration.

Serum 25-hydroxyvitamin D status in hip and spine-fracture patients in Japan

BACKGROUND

Serum 25-hydroxyvitamin D (25(OH)D) is used as an index that reflects the level of vitamin D. We have previously reported, on the basis of a study in Sado in Niigata, that patients with hip fracture have lower serum 25(OH)D levels than non-hip-fracture cases. In this study, the serum 25(OH)D status in hip-fracture cases was examined in four regions in Japan. Although most hip-fracture patients have experienced past spine-compression fractures, the relationship of these fractures and 25(OH)D is unknown. Therefore, we also examined the 25(OH)D level in spine-compression fracture patients in the same locations and time periods.

METHODS

The levels of 25(OH)D, intact parathyroid hormone (intact PTH), undercarboxylated osteocalcin (ucOC), urine N-terminal crosslinking telopeptide of type I collagen (NTX), and bone mineral density were examined in patients with hip and spine fracture due to osteoporosis in several regions in Japan.

RESULTS

There were no significant differences in age, BMI, serum 25(OH)D, serum intact PTH, and serum ucOC among the regions. Levels of serum 25(OH)D were low in patients with hip fracture and spine fracture. The average serum 25(OH)D level was significantly lower in hip-fracture patients than in spine-fracture patients (16.3 vs. 18.1 ng/mL, P < 0.05). High serum ucOC was found in 37% of hip-fracture patients and 44% of spine-fracture patients.

CONCLUSIONS

Both hip and spine-fracture patients have vitamin D insufficiency, with similar results found in elderly patients in four areas of Japan. The severity of this condition tends to be more serious in hip-fracture patients than in spine-fracture patients.

Serum vitamins in adult patients with short bowel syndrome receiving intermittent parenteral nutrition

BACKGROUND

Short bowel syndrome (SBS) occurs after massive intestinal resection, and parenteral nutrition (PN) therapy may be necessary even after a period of adaptation. The purpose of this study was to determine the vitamin status in adults with SBS receiving intermittent PN.

METHODS

The study was conducted on hospitalized adults with SBS who were receiving intermittent PN therapy (n = 8). Nine healthy volunteers, paired by age and sex, served as controls. Food ingestion, anthropometry, plasma folic acid, and vitamins B(12), C, A, D, E, and K were evaluated.

RESULTS

The levels of vitamins A, D, and B(12) in both groups were similar. SBS patients presented higher values of folic acid (21.3 ± 4.4 vs 14.4 ± 5.2, P = .01) and lower values of vitamin C (0.9 ± 0.4 vs 1.2 ± 0.3 mg/dL, P = .03), α-tocopherol (16.3 ± 3.4 vs 24.1 ± 2.7 µmol/L, P < .001), and phylloquinone (0.6 ± 0.2 vs 1.0 ± 0.5 nmol/L, P < .03). Eight-seven percent of patients had vitamin D deficiency, and all patients presented with serum vitamin E levels below reference values.

CONCLUSIONS

Despite all efforts to offer all the nutrients mentioned above, SBS patients had lower serum levels of vitamins C, E, and K, similar to those observed in patients on home PN. These findings suggest that the administered vitamins were not sufficient for the intermittent PN scheme and that individual adjustments are needed depending on the patient's vitamin status.

Association of vitamin K deficiency with bone metabolism and clinical disease activity in inflammatory bowel disease

OBJECTIVE

Inflammatory bowel disease (IBD) is a chronic inflammatory process in the digestive tract and patients with IBD develop osteopenia. Although vitamins K and D are important for maintaining bone health and inhibiting inflammation, their roles in patients with IBD are not clear. We investigated the roles of vitamins K and D in the bone health and inflammation in patients with IBD.

METHODS

Bone mineral density (BMD) of patients with IBD (Crohn's disease [CD], n = 47, and ulcerative colitis [UC], n = 40) was measured with dual-energy X-ray absorptiometry. Vitamin K and D levels of patients with IBD and healthy volunteers (n = 41) were evaluated by measuring serum undercarboxylated osteocalcin and 1,25 dihydroxyvitamin D, respectively. Clinical activity index was evaluated in patients with CD and UC.

RESULTS

BMD was low in patients with CD and UC. Serum undercarboxylated osteocalcin levels were significantly higher in patients with CD, but not with UC, compared with healthy subjects, indicating that bone vitamin K is insufficient in patients with CD. The levels of undercarboxylated osteocalcin were significantly correlated with the clinical activity index of CD, although they were not correlated with BMD. The levels of 1,25 dihydroxyvitamin D were significantly lower in patients with CD and UC than in healthy subjects. The levels of 1,25 dihydroxyvitamin D were inversely correlated with BMD in patients with UC and were not correlated with the clinical activity index of CD.

CONCLUSION

Vitamins K and D are insufficient in patients with IBD. Insufficiency of vitamin K is suggested to be associated with inflammatory processes of CD.

Emerging Issues in Vitamin K Research

Vitamin K is traditionally recognized for its role in blood clotting. More recently, new roles for vitamin K have emerged. The current evidence for the role of vitamin K in bone, cardiovascular, and reproductive health will be discussed. There will be a particular focus on populations who could be at risk for vitamin K deficiency.

Bone physiology and therapeutics in chronic critical illness

Modern medical practices allow patients to survive acute insults and be sustained by machinery and medicines for extended periods of time. We define chronic critical illness as a later stage of prolonged critical illness that requires tracheotomy. These patients have persistent elevations of inflammatory cytokines, diminished hypothalamic-pituitary function, hypercatabolism, immobilization, and malnutrition. The measurement of bone turnover markers reveals markedly enhanced osteoclastic bone resorption that is uncoupled from osteoblastic bone formation. We review the mechanisms by which these factors contribute to the metabolic bone disease of chronic critical illness and suggest potential therapeutics.

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

To evaluate the possible interaction of metabolic effects in the mevalonate pathway between amino-bisphosphonates (amino-BP) and vitamin K, the serum level of undercarboxylated osteocalcin (ucOC) was measured in amino-BP users in relationship to incident fracture occurrence. Osteoporotic patients (mean age, 70.7 +/- 9.1 years; n = 231) treated with alendronate or risedronate were followed for 3.4 +/- 2.1 years, and observations regarding the presence or absence of incident fractures in their vertebrae were made based on vertebral X-ray films every year. During the observation period, new fractures were found in a total of 71 patients (incident vertebral fracture, n = 61; the remaining 10 patients had long bone fractures). The baseline data of the patients with incident fractures indicated that incident fractures are more likely to occur in older patients who have a higher number of prevalent vertebral fractures and lower baseline lumbar bone mineral density (LBMD) as compared to patients without incident fractures. There was no significant difference in the changes of LBMD and urinary excretion of NTX after treatment. On the other hand, the serum level of ucOC in patients with incident fractures and with amino-BP treatment was significantly higher (2.75 +/- 0.19 ng/ml) than that in patients without incident fractures and with amino-BP treatment (2.28 +/- 0.13 ng/ml) (P = 0.038). These results indicate that older age, a greater number of prevalent fractures and higher ucOC levels, and lower LBMD are risks for incident fractures despite use of amino-BP. The time-dependent incident fracture rate was higher in accordance with an increase in the number of risk items (P < 0.001 in log-rank and Wilcoxon tests). In conclusion, measurement of undercarboxylated osteocalcin may be useful for assessing fracture risk in patients receiving amino-BP treatment.

Urinary levels of cross-linked N-terminal telopeptide of type I collagen and nutritional status in Japanese professional baseball players

The objective of the present study was to investigate the nutritional status from the aspect of bone metabolism in Japanese elite male athletes with increased bone resorption. Urinary levels of a bone resorption marker, cross-linked N-terminal telopeptide of type 1 collagen (NTX), were measured in 71 professional baseball players (age, 18-39 years); the mean urinary NTX level was 65.6 (range, 17.5-269.0) nM BCE/mM Cr. Of 71 athletes, 9 with high levels of urinary NTX (greater than mean + 1 SD) were examined by measuring serum biochemical markers and nutritional assessment (simple food frequency questionnaire). Serum biochemical marker analysis showed that 7 of these 9 athletes had vitamin D insufficiency, as indicated by low serum levels of 25-hydroxyvitamin D, and that all 9 athletes showed vitamin K insufficiency as indicated by low levels of vitamins K(1) and K(2). Nutritional assessment revealed high intakes of protein and low intakes of calcium and vitamin D based on adequate intake (AI). However, daily vitamin K intake achieved the AI. These results suggest that there exist elite male athletes who show increased bone resorption and calcium and vitamin D insufficiency. However, there was a discrepancy between vitamin K intake and serum levels of vitamins K(1) and K(2). The present study raised an issue regarding the nutritional status from the point of view of bone metabolism in elite male athletes such as professional baseball players.

Integrative physiology: defined novel metabolic roles of osteocalcin

The prevailing model of osteology is that bones constantly undergo a remodeling process, and that the differentiation and functions of osteoblasts are partially regulated by leptin through different central hypothalamic pathways. The finding that bone remodeling is regulated by leptin suggested possible endocrinal effects of bones on energy metabolism. Recently, a reciprocal relationship between bones and energy metabolism was determined whereby leptin influences osteoblast functions and, in turn, the osteoblast-derived protein osteocalcin influences energy metabolism. The metabolic effects of bones are caused by the release of osteocalcin into the circulation in an uncarboxylated form due to incomplete gamma-carboxylation. In this regard, the Esp gene encoding osteotesticular protein tyrosine phosphatase is particularly interesting because it may regulate gamma-carboxylation of osteocalcin. Novel metabolic roles of osteocalcin have been identified, including increased insulin secretion and sensitivity, increased energy expenditure, fat mass reduction, and mitochondrial proliferation and functional enhancement. To date, only a positive correlation between osteocalcin and energy metabolism in humans has been detected, leaving causal effects unresolved. Further research topics include: identification of the osteocalcin receptor; the nature of osteocalcin regulation in other pathways regulating metabolism; crosstalk between nutrition, osteocalcin, and energy metabolism; and potential applications in the treatment of metabolic diseases.

Vitamin K epoxide reductase (VKORC1) gene mutations in osteoporosis: A pilot study

Susceptibility to osteoporosis seems to be influenced genetically. Previous studies on the effects of genetic polymorphisms on bone mineral density (BMD) showed controversial results. Vitamin K hydrochinon is an important cofactor for gamma carboxylation of osteocalcin. The reduction of vitamin K to vitamin K hydrochinon depends on the vitamin K epoxide reductase complex subunit 1 (VKORC1). We evaluated the impact of polymorphisms in VKORC1 on BMD and fractures. In this single-center study, 184 individuals (141 female subjects and 43 male subjects, mean age: 63.2 +/- 14.3 years) were recruited. In all, 149 of 184 could be genotyped by allele-specific polymerase chain reaction (PCR) for the VKORC1 variants 3673G>A or 9041G>A. The genotypes were correlated with clinical parameters. Vitamin K(1) concentrations were determined by high-performance liquid chromatography (HPLC); carboxylated (GlaOC) and undercarboxylated osteocalcin (GluOC) was determined by enzyme-linked immunosorbent assays (ELISAs). The 9041 GG and GA genotypes were significantly more frequent in patients with low BMD (P = 0.012). Thus, carriers of at least 1 G-allele seem to have a higher risk for low BMD. No statistically significant association was found for the 3673 G>A variant and BMD. GluOC concentrations were higher in patients who carried a 3673 GA and GG genotypes (P = 0.07). For both variants, no association with fractures could be observed. In our cohort, a genetic variation in the 3'-region of the VKORC1 gene (9041 AG and GG) was associated significantly with low BMD. This finding suggests that VKORC1 may play a role in osteoporosis. The results of our pilot study should be confirmed as our findings may be important for treatment decisions.

Hop rho iso-alpha acids, berberine, vitamin D3 and vitamin K1 favorably impact biomarkers of bone turnover in postmenopausal women in a 14-week trial

Osteoporosis is a major health issue facing postmenopausal women. Increased production of pro-inflammatory cytokines resulting from declining estrogen leads to increased bone resorption. Nutrition can have a positive impact on osteoporosis prevention and amelioration. The objective of this study was to investigate the impact of targeted phytochemicals and nutrients essential for bone health on bone turnover markers in healthy postmenopausal women. In this 14-week, single-blinded, 2-arm placebo-controlled pilot study, all women were instructed to consume a modified Mediterranean-style low-glycemic-load diet and to engage in limited aerobic exercise; 17 randomized to the placebo and 16 to the treatment arm (receiving 200 mg hop rho iso-alpha acids, 100 mg berberine sulfate trihydrate, 500 IU vitamin D(3) and 500 microg vitamin K(1), twice daily). Thirty-two women completed the study. Baseline nutrient intake did not differ between arms. At 14 weeks, the treatment arm exhibited an estimated 31% mean reduction (P = 0.02) in serum osteocalcin (a marker of bone turnover), whereas the placebo arm exhibited a 19% increase (P = 0.03) compared to baseline. Serum 25-hydroxyvitamin D (25(OH)D) increased by 13% (P = 0.24) in the treatment arm and decreased by 25% (P < 0.01) in the placebo arm. The between-arm differences for OC and 25(OH)D were statistically significant. Serum IGF-I was increased in both arms, but the increase was more significant in the treatment arm at 14 weeks (P < 0.01). Treatment with hop rho iso-alpha acids, berberine sulfate trihydrate, vitamin D(3) and vitamin K(1) produced a more favorable bone biomarker profile that supports a healthy bone metabolism.

Relationships between undercarboxylated osteocalcin and vitamin K intakes, bone turnover, and bone mineral density in healthy women

BACKGROUND & AIMS

Low vitamin K intakes and high levels of undercarboxylated osteocalcin (ucOC) are risk factors for hip fractures. However, the relationship between ucOC and vitamin K intakes, bone mineral density (BMD) and bone biochemical markers is not clarified.

METHODS

We enrolled 221 healthy women, and examined BMD, urinary type-I collagen cross-linked-N-telopeptide (uNTX), and nutrient intakes. BMD was measured at the lumbar spine and femoral neck.

RESULTS

Vitamin K intakes were significantly and negatively correlated with ucOC after adjustment for age, height, and body weight (r=-0.305, p<0.0001). ucOC was negatively associated with lumbar BMD (r=-0.147, p<0.05), but not femoral neck BMD (r=-0.099, p=0.095) after adjustment for age, height, and body weight. In multiple regression analysis, even after adjustment for age, height, body weight, and vitamin K intake, a significant and positive correlation remained between ucOC and urinary NTX (r=0.493, p<0.0001). Moreover, in postmenopausal women, ucOC levels were positively correlated with urinary NTX, but not BMD.

CONCLUSION

Dietary vitamin K intakes influence serum levels of ucOC in healthy women. Furthermore, ucOC may be linked to bone biochemical markers.