Vitamin K, bone fractures, and vascular calcifications in chronic kidney disease: an important but poorly studied relationship

Angelicin: A leading culprit involved in fructus Psoraleae liver injury via inhibition of VKORC1

ETHNOPHARMACOLOGICAL RELEVANCE

The adverse effects of Fructus Psoraleae (FP), especially liver injury, have attracted wide attention in recent years.

AIM OF THE STUDY

To establish a system to explore potential hepatotoxic targets and the chief culprit of liver injury based on clinical experience, network pharmacological method, molecular docking, and in vitro and in vivo experiments.

MATERIALS AND METHODS

Clinical applications and adverse reactions to FP were obtained from public literatures. Components absorbed in the blood were selected as candidates to search for potential active targets (PATs) of FP. Subsequently, potential pharmacological core targets (PPCTs) were screened through the "drug targets-disease targets" network. Non-drug active targets (NPATs) were obtained by subtracting the PPCTs from the PATs. The potential hepatotoxic targets (PHTs) of FP were the intersection targets obtained from Venn analysis using NPATs, hepatotoxic targets, and adverse drug reaction (ADR) targets provided by the databases. Then, potential hepatotoxic components and targets were obtained using the "NPATS-component" network relationship. Molecular docking and in vitro and in vivo hepatotoxicity experiments were performed to verify the targets and related components.

RESULTS

Overall, 234 NPATs were acquired from our analysis, and 6 targets were identified as PHTs. Results from molecular docking and in vitro and in vivo experiments showed that angelicin is the leading cause of liver injury in FP, and VKORC1 plays an important role.

CONCLUSION

The results indicate that six targets, especially VKORC1, are associated with the PHTs of FP, and angelicin is the leading culprit involved in FP liver injury via inhibition of VKORC1.

The association of osteoporosis and cardiovascular disease risk score based on the Framingham and ACC/AHA risk prediction models: a cross-sectional analysis of Bushehr Elderly Health Program

Background

The association between osteoporosis and cardiovascular disease, two major health problems, has been reported in some studies. In this study was aimed to investigate the relationship between osteoporosis and the CVD risk score based on Framingham and American College of Cardiology and the American Heart Association (ACC/AHA) prediction models in the population over 60 years old.

Methods

A cross-sectional analysis was conducted on data from 2389 men and women participating in the Bushehr Elderly Health (BEH) program. Osteoporosis was defended as T-score ≤  - 2.5 at any site (total hip, femoral neck and lumbar spine (L1-L4). Based on Framingham and ACC/AHA risk scores, participants were categorized as non-high risk (< 20%) or high-risk (≥ 20%). Logistic regression model, was applied to investigate the relationship between osteoporosis and cardiovascular disease risk scores. All comparisons were stratified by sex.

Results

Considering the cut point of ≥ 20% for CVD risk, 36.7% of women and 66.2% of men were categorized as having high risk of CVD in ACC/AHA model. These values in women and men based on the Framingham model were 30% and 35.7%, respectively. In general, there was a negative significant correlation between BMD in the femoral neck, total hip and TBS except for the spine with the CVD risk score in both models. After adjusting for confounding variables, a significant positive association was observed between osteoporosis only at femoral neck with CVD risk score ≥ 20% based on ACC/AHA in both genders.

Conclusion

The ACC/AHA model is effective in identifying the CVD risk difference between individuals with and without osteoporosis.

Association of cardiovascular disease prevalence with BMD and fracture in men with T2DM

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) are predisposed to cardiovascular disease (CVD). Bone mineral density (BMD) is linked to CVD, but most studies focused on women. Our analysis aims to explore the association of BMD and fracture with the prevalence of CVD in men with T2DM.

METHODS

In this retrospective cross-sectional study, 856 men with T2DM were enrolled. BMDs at the lumbar spine (L2-4), femoral neck (FN), and total hip (TH) were measured by dual-energy X-ray absorptiometry (DXA). The CVD outcome was determined as the sum of the following conditions: congestive heart failure, coronary heart disease, angina pectoris, myocardial infarction, the requirement for coronary artery revascularization, and stroke. The relationship between BMDs and CVD was investigated by restricted cubic spline curves and logistic regression models.

RESULTS

A total of 163 (19.0%) patients developed CVD. The restricted cubic spline curve revealed a linear and negative association between FN-BMD, TH-BMD, and CVD. After full adjustments for confounding covariates, the odds ratios were 1.34 (95% confidence interval [CI] [1.11-1.61], p < .05), 1.3 (95% CI [1.05-1.60], p < .05), and 1.26 (95% CI [1.02-1.55], p < .05) for each 1-SD decrease in BMDs of L2-4, FN and TH, respectively. T-scores of < -1 for BMD of L2-4 and FN were independently associated with CVD (p < .05). Subgroup analyses further supported our findings.

CONCLUSIONS

The prevalence of CVD was inversely correlated with BMD levels in men with T2DM, particularly at the FN. We hypothesized that monitoring FN-BMD and early intervention would help reduce CVD risk in men with T2DM, especially those with hypertension.

Treatment of Vitamin K Deficiency in Hemodialysis Patients - A Pilot Study Comparing Menaquinone-7 Tablets and a Vitamin K Rich Diet

Purpose

Vitamin K deficiency and hence a high level of plasma dephosphorylated undercarboxylated matrix Gla protein (dp-ucMGP) is frequent in patients on hemodialysis. This group is recommended to restrict their potassium intake which often leads to restriction of vitamin K rich foods. A menaquinone-7 (MK-7) supplement has been shown to decrease dp-ucMGP, but it has yet to be examined if a vitamin K rich diet could be equally effective.

Patients and Methods

A prospective randomized crossover intervention trial with two arms; 6 weeks of 360 μg MK-7 tablet/day and 6 weeks of a vitamin K rich diet with a 3-week washout period in between. Participants were 10 patients in hemodialysis and the primary outcome measures were changes in dp-ucMGP, total MGP (tMGP), and undercarboxylated osteocalcin (ucOC). Furthermore, the level of potassium and phylloquinone in broccoli was determined after different durations of boiling.

Results

During the MK-7 intervention the dp-ucMGP and ucOC decreased significantly compared to baseline (−0.42 [−0.93; −0.22] nmol/L (p=<0.01) and −1.85 [−2.91; −1.30] nmol/L (p<0.01)), while these were unchanged during the dietary intervention (0.03 [−0.64; 0.37] nmol/L (p=1.00) and 0.30 [−1.71; 1.41] nmol/L (p=0.77)). Between the two interventions there was a greater decrease in ucOC (p=0.02) during the MK-7 compared to the dietary period. No significant changes in the total MGP levels were found in any of the periods. The retention of potassium following boiling for 2 minutes and 8 minutes was 76% and 49%, respectively, while for phylloquinone the retention was 92%, and independent of duration of boiling.

Conclusion

A daily MK-7 supplement for 6 weeks lowered dp-ucMGP and ucOC significantly, while a vitamin K rich diet was not able to induce any significant effect. Boiled broccoli maintains a reasonable content of phylloquinone while potassium is extracted and is a reasonable source of phylloquinone for patients on hemodialysis.

Vitamin E (Alpha-Tocopherol) Metabolism and Nutrition in Chronic Kidney Disease

Vitamin E (alpha-tocopherol) is an essential micronutrient and fat-soluble antioxidant with proposed role in protecting tissues from uncontrolled lipid peroxidation. This vitamin has also important protein function and gene modulation effects. The metabolism of vitamin E depends on hepatic binding proteins that selectively retain food alpha-tocopherol for incorporation into nascent VLDL and tissue distribution together with esterified cholesterol and triglycerides. Chronic kidney disease (CKD) is a condition of oxidative stress and increased lipid peroxidation, that are associated with alterations of alpha-tocopherol metabolism and function. Specific changes have been reported for the levels of its enzymatic metabolites, including both short-chain and long-chain metabolites, the latter being endowed with regulatory functions on enzymatic and gene expression processes important for the metabolism of lipids and xenobiotics detoxification, as well as for the control of immune and inflammatory processes. Vitamin E therapy has been investigated in CKD using both oral vitamin E protocols and vitamin E-coated hemodialyzers, showing promising results in the secondary prevention of cardiovascular disease, as well as of immune and hematological complications. These therapeutic approaches are reviewed in the present article, together with a narrative excursus on the main findings indicating CKD as a condition of relative deficiency and impaired metabolism of vitamin E.

The Role of Vitamin K in CKD-MBD

PURPOSE OF REVIEW

We describe the mechanism of action of vitamin K, and its implication in cardiovascular disease, bone fractures, and inflammation to underline its protective role, especially in chronic kidney disease (CKD).

RECENT FINDINGS

Vitamin K acts as a coenzyme of y-glutamyl carboxylase, transforming undercarboxylated in carboxylated vitamin K-dependent proteins. Furthermore, through the binding of the nuclear steroid and xenobiotic receptor, it activates the expression of genes that encode proteins involved in the maintenance of bone quality and bone remodeling. There are three main types of K vitamers: phylloquinone, menaquinones, and menadione. CKD patients, for several conditions typical of the disease, are characterized by lower levels of vitamin K than the general populations, with a resulting higher prevalence of bone fractures, vascular calcifications, and mortality. Therefore, the definition of vitamin K dosage is an important issue, potentially leading to reduced bone fractures and improved vascular calcifications in the general population and CKD patients.

The Vessels-Bone Axis: Iliac Artery Calcifications, Vertebral Fractures and Vitamin K from VIKI Study

Vascular calcification and fragility fractures are associated with high morbidity and mortality, especially in end-stage renal disease. We evaluated the relationship of iliac arteries calcifications (IACs) and abdominal aortic calcifications (AACs) with the risk for vertebral fractures (VFs) in hemodialysis patients. The VIKI study was a multicenter cross-sectional study involving 387 hemodialysis patients. The biochemical data included bone health markers, such as vitamin K levels, vitamin K-dependent proteins, vitamin 25(OH)D, alkaline phosphatase, parathormone, calcium, and phosphate. VF, IACs and AACs was determined through standardized spine radiograms. VF was defined as >20% reduction of vertebral body height, and VC were quantified by measuring the length of calcium deposits along the arteries. The prevalence of IACs and AACs were 56.1% and 80.6%, respectively. After adjusting for confounding variables, the presence of IACs was associated with 73% higher odds of VF (p = 0.028), whereas we found no association (p = 0.294) for AACs. IACs were associated with VF irrespective of calcification severity. Patients with IACs had lower levels of vitamin K2 and menaquinone 7 (0.99 vs. 1.15 ng/mL; p = 0.003), and this deficiency became greater with adjustment for triglycerides (0.57 vs. 0.87 ng/mL; p < 0.001). IACs, regardless of their extent, are a clinically relevant risk factor for VFs. The association is enhanced by adjusting for vitamin K, a main player in bone and vascular health. To our knowledge these results are the first in the literature. Prospective studies are needed to confirm these findings both in chronic kidney disease and in the general population.

Advances in Enhanced Menaquinone-7 Production From Bacillus subtilis

The production of nutraceutical compounds through biosynthetic approaches has received considerable attention in recent years. For example, Menaquinone-7 (MK-7), a sub-type of Vitamin K2, biosynthesized from Bacillus subtilis (B. subtilis), proved to be more efficiently produced than the conventional chemical synthesis techniques. This is possible due to the development of B. subtilis as a chassis cell during the biosynthesis stages. Hence, it is imperative to provide insights on the B. subtilis membrane permeability modifications, biofilm reactors, and fermentation optimization as advanced techniques relevant to MK-7 production. Although the traditional gene-editing method of homologous recombination improves the biosynthetic pathway, CRISPR-Cas9 could potentially resolve the drawbacks of traditional genome editing techniques. For these reasons, future studies should explore the applications of CRISPRi (CRISPR interference) and CRISPRa (CRISPR activation) system gene-editing tools in the MK-7 anabolism pathway.

Gut microbiome responses in the metabolism of human dietary components: Implications in health and homeostasis

The gut microbiome and its link with human health and disease have gained a lot of attention recently. The microbiome executes its functions in the host by carrying out the transformation of dietary components and/or de novo synthesis of various essential nutrients. The presence of complex microbial communities makes it difficult to understand the host-microbiome interplay in the metabolism of dietary components. This review attempts to uncover the incredible role of the gut microbiome in the metabolism of dietary components, diet-microbiome interplay, and restoration of the microbiome. The in silico analysis performed in this study elucidates the functional description of essential/hub genes involved in the amino acid degradation pathway, which are mutually present in the host and its gut microbiome. Hence, the computational model helps comprehend the inter-and intracellular molecular networks between humans and their microbial partners.

Vitamin K in CKD Bone Disorders

Vitamin K is principally known because it is involved in blood coagulation. Furthermore, epidemiological studies showed that its deficit was associated with increased fragility fractures, vascular calcification and mortality. There are two main types of vitamin K vitamers: Phylloquinone (or PK) and Menaquinones (MKn). Vitamin K acts both as coenzyme of y-glutamyl carboxylase (GGCX) transforming undercarboxylated in carboxylated vitamin K-dependent proteins (e.g., Osteocalcin and Matrix Gla Protein) and as a ligand of the nuclear steroid and xenobiotic receptor (SXR) (in murine species Pregnane X Receptor: PXR), expressed in osteoblasts. It has been highlighted that the uremic state is a condition of greater vitamin K deficiency than the general population with resulting higher prevalence of bone fractures, vascular calcifications and mortality. The purpose of this literature review is to evaluate the protective role of Vitamin K in bone health in CKD patients.

Sevelamer Use, Vitamin K Levels, Vascular Calcifications, and Vertebral Fractures in Hemodialysis Patients: Results from the VIKI Study

Hyperphosphatemia is a risk factor for vascular calcifications (VCs), which are part of the chronic kidney disease-mineral and bone disorders (CKD-MBD). Vitamin K-dependent proteins such as matrix Gla protein (MGP) and bone Gla proteins (BGP, or osteocalcin) can inhibit VCs and regulate bone mineralization. In this analysis of the Vitamin K Italian (VIKI) study, the relationship between vitamin K status, vertebral fractures (VFs) and VCs in 387 hemodialysis (HD) patients with (N = 163; 42.1%) or without N = 224; 57.9%) sevelamer was evaluated. Levels of vitamin K vitamers K1 and K2 or menaquinones (MK; MK4-7), total and undercarboxylated (uc) forms for both BGP and MGP were determined. Although no differences in clinical characteristics were noted, lower levels of MK4 (0.45 versus 0.6 ng/mL, p = .01) and a greater MK4 deficiency was observed in sevelamer-treated patients (13.5% versus 5.4%, p = .005). Multivariate logistic regression revealed that MK4 deficiency was associated with sevelamer use (odds ratio [OR] = 2.64, 95% confidence interval [CI] 1.25-5.58, p = .011) and aortic calcification (OR = 8.04, 95% CI 1.07-60.26, p = .04). In the same logistic model, sevelamer amplified the effect of total BGP levels on the odds of VFs in patients with total BGP <150 μg/L compared with those with total BGP ≥150 μg/L (OR = 3.15, 95% CI 1.46-6.76, p = .003). In contrast, there was no such effect in those untreated (total BGP <150 μg/L versus total BGP ≥150 μg/L: OR = 1.21, 95% CI 0.66-2.23, p = .54]; p = .049 for effect modification by sevelamer). Sevelamer may interfere with MK4 levels in HD patients and interact with low BGP levels to increase bone fractures in CKD patients. © 2020 American Society for Bone and Mineral Research (ASBMR).

Are Nutraceuticals Beneficial in Chronic Kidney Disease?

Chronic kidney disease (CKD) is a worldwide health problem in which prevalence is constantly rising. The pathophysiology of CKD is complicated and has not been fully resolved. However, elevated oxidative stress is considered to play a vital role in the development of this disease. CKD is also thought to be an inflammatory disorder in which uremic toxins participate in the development of the inflammatory milieu. A healthy, balanced diet supports the maintenance of a good health status as it helps to reduce the risk of the development of chronic diseases, including chronic kidney disease, diabetes mellitus, and hypertension. Numerous studies have demonstrated that functional molecules and nutrients, including fatty acids and fiber as well as nutraceuticals such as curcumin, steviol glycosides, and resveratrol not only exert beneficial effects on pro-inflammatory and anti-inflammatory pathways but also on gut mucosa. Nutraceuticals have attracted great interest recently due to their potential favorable physiological effects on the human body and their safety. This review presents some nutraceuticals in which consumption could exert a beneficial impact on the development and progression of renal disease as well cardiovascular disease.

Vertebral fracture is associated with myocardial infarction in incident hemodialysis patients: a Korean nationwide population-based study

Chronic kidney disease (CKD)-mineral and bone disorder suggests that fragile bone and vascular disorder might be connected closely in CKD patients. In this study, fracture event was significantly associated with myocardial infarction (MI) in end-stage renal disease patients on hemodialysis (HD), especially for vertebral fractures.

INTRODUCTION

CKD-mineral and bone disorder is characterized by biochemical abnormalities, bone disorders, and vascular calcification. We aimed to verify the association between fracture and MI in CKD patients.

METHODS

Records for incident CKD stage 3 to 5 patients and patients who initiated HD between July 2014 and June 2018 were retrieved from the Korean Health Insurance Review & Assessment Service Database. Fractures were defined using diagnostic codes and were classified into vertebral, femoral, and other site fractures. MI was defined using a combination of MI diagnostic codes and related procedure codes. Multiple logistic regressions and 1:1 propensity score matching analysis were conducted.

RESULTS

A total of 38,935 patients (HD, 11,379; pre-dialysis CKD, 27,556) were included in this study. A total of 5,057 (13.0%) patients experienced fracture, and 1,431 (3.7%) patients had MI. Multiple logistic regression analysis showed that fracture was significantly associated with MI in the HD group (odds ratio (OR) 1.34, P = 0.024), but not in the pre-dialysis CKD group (OR 1.04, P = 0.701). After propensity score matching for age, gender, and diabetes mellitus between patients with and without fracture, fracture still significantly correlated with MI in HD patients (OR 1.47, P = 0.034) but not in patients with pre-dialysis CKD (OR 1.04, P = 0.751). Subgroup analysis by fracture site found that vertebral fracture was associated with MI in HD patients (OR 2.11, P = 0.024), but femoral or other site fractures were not.

CONCLUSION

In HD patients, fracture was significantly associated with MI, especially for vertebral fractures patients.

Metabolic and functional interplay between gut microbiota and fat-soluble vitamins

Gut microbiota is a complex ecosystem seen as an extension of human genome. It represents a major metabolic interface of interaction with food components and xenobiotics in the gastrointestinal (GI) environment. In this context, the advent of modern bacterial genome sequencing technology has enabled the identification of dietary nutrients as key determinants of gut microbial ecosystem able to modulate the host-microbiome symbiotic relationship and its effects on human health. This article provides a literature review on functional and molecular interactions between a specific group of lipids and essential nutrients, e.g., fat-soluble vitamins (FSVs), and the gut microbiota. A two-way relationship appears to emerge from the available literature with important effects on human metabolism, nutrition, GI physiology and immune function. First, FSV directly or indirectly modify the microbial composition involving for example immune system-mediated and/or metabolic mechanisms of bacterial growth or inhibition. Second, the gut microbiota influences at different levels the synthesis, metabolism and transport of FSV including their bioactive metabolites that are either introduced with the diet or released in the gut via entero-hepatic circulation. A better understanding of these interactions, and of their impact on intestinal and metabolic homeostasis, will be pivotal to design new and more efficient strategies of disease prevention and therapy, and personalized nutrition.

Current Therapy in CKD Patients Can Affect Vitamin K Status

Chronic kidney disease (CKD) patients have a higher risk of cardiovascular (CVD) morbidity and mortality compared to the general population. The links between CKD and CVD are not fully elucidated but encompass both traditional and uremic-related risk factors. The term CKD-mineral and bone disorder (CKD-MBD) indicates a systemic disorder characterized by abnormal levels of calcium, phosphate, PTH and FGF-23, along with vitamin D deficiency, decreased bone mineral density or altered bone turnover and vascular calcification. A growing body of evidence shows that CKD patients can be affected by subclinical vitamin K deficiency; this has led to identifying such a condition as a potential therapeutic target given the specific role of Vitamin K in metabolism of several proteins involved in bone and vascular health. In other words, we can hypothesize that vitamin K deficiency is the common pathogenetic link between impaired bone mineralization and vascular calcification. However, some of the most common approaches to CKD, such as (1) low vitamin K intake due to nutritional restrictions, (2) warfarin treatment, (3) VDRA and calcimimetics, and (4) phosphate binders, may instead have the opposite effects on vitamin K metabolism and storage in CKD patients.

Overweight-obesity is associated with decreased vitamin K2 levels in hemodialysis patients

OBJECTIVES

Obesity is an important risk factor for morbidity and mortality. Vitamin K2 is involved in the production of bone and matrix amino acid g-carboxy-glutamic acid (Gla) proteins (vitamin K-dependent proteins [VKDPs]), regulating bone and vascular calcification (VC). Bone Gla protein (BGP) is involved both in bone mineralization and VCs. We assessed the relationships between vitamin K levels and body mass index (BMI) according to the hypothesis that the impact of BMI on mortality is partly driven by low vitamin K levels.

METHODS

The Vitamin K Italian (VIKI) study included 387 hemodialysis patients from 18 dialysis centers in Italy. We determined plasma levels of bone markers: vitamin K levels, VKDPs, vitamin 25(OH)D, alkaline phosphatase (ALP), parathyroid hormone (PTH), calcium (Ca), phosphorus (P) and routine biochemistry. BMI was classified into the following categories: underweight (BMI < 18.5 kg/m²), normal weight (18.5 ≤ BMI < 25 kg/m²), overweight (25 ≤ BMI < 30 kg/m²) and obese (BMI ≥ 30 kg/m²).

RESULTS

45.2% of patients were overweight or obese. Stratification by BMI demonstrated lower median menaquinone-7 (MK7)/triglycerides levels in obese patients (0.42 ng/mg [0.19, 0.87], p = 0.005). BGP levels were lower in overweight and obese patients (152 mcg/L [83.2, 251] and 104 mcg/L [62.7, 230], p = <0.001). Furthermore, there was an inverse correlation between MK7/triglycerides levels and BMI (regression coefficient β = -0.159; p = 0.003). In multiple linear regression, there was an inverse relationship between BGP levels and BMI (β = - 0.119; p = 0.012).

CONCLUSIONS

These data are the first to report an inverse relationship between Vitamin K2 levels and BMI in hemodialysis patients. Further studies are needed to confirm these findings and to determine if lower levels of Vitamin K are related to greater morbidity and mortality in this at-risk population.

The effect of aeration and mixing in developing a dairy-based functional food rich in menaquinone-7

Vitamin menaquinone-7 (MK-7) supplementation improves bone health and reduces the incidence of osteoporosis. Despite the recent developments in MK-7 fermentation using Bacillus subtilis natto, low fermentation yields, as well as complicated downstream processing steps, are still the main reasons for the expensive final product. To overcome these issues, developing a fermented dairy-based product rich in MK-7 by avoiding costly downstream steps and optimising the fermentation operating conditions to enhance the MK-7 concentration would be an alternative approach. The present study, therefore, aims to evaluate the role of agitation and aeration as the key operating conditions on MK-7 production by Bacillus subtilis natto using a milk media. The agitation and aeration rates of 525 RPM and 5 VVM were found to be the optimum levels leading to the production of 3.54 mg/L of MK-7. Further, the sensory evaluation was performed to compare the sensory properties of the freeze-dried fermented samples with non-fermented milk samples. The results illustrated that the fermented samples had a significant saltiness with intense aroma resulting in the less acceptability of them by the panellists.

Vitamin K2 Status and Arterial Stiffness Among Untreated Migraine Patients: A Case-Control Study

OBJECTIVE

We aimed to examine arterial stiffness and vitamin K2 status in migraine subjects by comparison to controls.

BACKGROUND

Migraine is a primary headache disorder that has been associated with an increased risk of cardiovascular events. Mechanisms underlying this increased risk, however, remain unclear. Vitamin K2 deficiency emerged as a cardiovascular risk factor, but vitamin K2 status has never been explored in migraine subjects.

DESIGN AND METHODS

This is a case-control, single-center, observational study that includes a cohort of subjects with migraine and their age- and sex-matched controls. Arterial stiffness was measured using carotid-femoral pulse wave velocity (cfPWV). Dephosphorylated-uncarboxylated matrix-Gla-protein (dp-ucMGP) was used as a marker for vitamin K2 status. A propensity-matched scoring method was used.

RESULTS

A total of 146 patients (73 matched pairs) were included in this study, of whom 89% were women with a mean age of 31.9 ± 8.4 years. Compared with controls, migraine patients had statistically significantly higher mean cfPWV (7.2 ± 1.1 vs 6.4 ± 0.8 m/s, 95% confidence interval (CI) of mean difference [0.45, 1.08], P < .001), as well as higher dp-ucMGP (454.3 ± 116.7 pmol/L vs 379.8 ± 126.6 pmol/L, 95% CI of mean difference [34.63, 114.31], P < .001). Higher cfPWV was associated with higher dp-ucMGP concentrations only in the migraine with aura (MWA) group. Moreover, migraine subjects had a higher frequency of vitamin K2 deficiency (dp-ucMGP ≥ 500 pmol/L) compared to controls, but this association was not statistically significant (23/73 [31.5%] vs 16/73 [21.9%], P = .193).

CONCLUSIONS

Individuals with migraine have worse indices of arterial stiffness as compared with their age- and sex-matched control subjects. This increase in arterial stiffness is associated with an increase in markers of vitamin K2 deficiency in the MWA group.

The Role of Vitamin K in Vascular Calcification

Vascular calcification (VC) is common in advanced chronic kidney disease (CKD), contributes to cardiovascular disease (CVD), and associates with increased mortality. Major risk factors for VC in CKD are increasing age, dialysis vintage, and positive net calcium-phosphate balance. To date, no specific therapy that prevents progression or facilitates regression of VC beyond careful attention to calcium and phosphate balance exists. Accumulating evidence demonstrates that CKD patients may incur subclinical vitamin K deficiency. This deficiency may be induced by exhaustion of vitamin K due to its high requirement by vitamin K-dependent proteins to inhibit VC. This review analyzes the pathophysiological mechanisms and clinical consequences of vitamin K deficiency with emphasis on its involvement on vascular calcification in CKD and end-stage renal disease and its relationship to the bone-vascular axis.

Vitamin K in Chronic Kidney Disease

Vitamin K is a composite term referring to a group of fat-soluble vitamins that function as a cofactor for the enzyme γ-glutamyl carboxylase (GGCX), which activates a number of vitamin K-dependent proteins (VKDPs) involved in haemostasis and vascular and bone health. Accumulating evidence demonstrates that chronic kidney disease (CKD) patients suffer from subclinical vitamin K deficiency, suggesting that this represents a population at risk for the biological consequences of poor vitamin K status. This deficiency might be caused by exhaustion of vitamin K due to its high requirements by vitamin K-dependent proteins to inhibit calcification.

Vitamin K‑dependent proteins involved in bone and cardiovascular health (Review)

In postmenopausal women and elderly men, bone density decreases with age and vascular calcification is aggravated. This condition is closely associated with vitamin K2 deficiency. A total of 17 different vitamin K-dependent proteins have been identified to date. Vitamin K-dependent proteins are located within the bone, heart and blood vessels. For instance, carboxylated osteocalcin is beneficial for bone and aids the deposition of calcium into the bone matrix. Carboxylated matrix Gla protein effectively protects blood vessels and may prevent calcification within the vascular wall. Furthermore, carboxylated Gla-rich protein has been reported to act as an inhibitor in the calcification of the cardiovascular system, while growth arrest-specific protein-6 protects endothelial cells and vascular smooth muscle cells, resists apoptosis and inhibits the calcification of blood vessels by inhibiting the apoptosis of vascular smooth muscle cells. In addition, periostin may promote the differentiation, aggregation, adhesion and proliferation of osteoblasts. Periostin also occurs in the heart and may be associated with the reconstruction of heart function. These vitamin K-dependent proteins may exert their functions following γ-carboxylation with vitamin K, and different vitamin K-dependent proteins may exhibit synergistic effects or antagonistic effects on each other. In the cardiovascular system with vitamin K antagonist supplement or vitamin K deficiency, calcification occurs in the endothelium of blood vessels and vascular smooth muscle cells are transformed into osteoblast-like cells, a phenomenon that resembles bone growth. Both the bone and cardiovascular system are closely associated during embryonic development. Thus, the present study hypothesized that embryonic developmental position and tissue calcification may have a certain association for the bone and the cardiovascular system. This review describes and briefly discusses several important vitamin K-dependent proteins that serve an important role in bone and the cardiovascular system. The results of the review suggest that the vascular calcification and osteogenic differentiation of vascular smooth muscle cells may be associated with the location of the bone and cardiovascular system during embryonic development.

Vitamin K plasma levels determination in human health

Vitamin K (phylloquinone or vitamin K1 and menaquinones or vitamin K2) plays an important role as a cofactor in the synthesis of hepatic blood coagulation proteins, but recently has also aroused an increasing interest for its action in extra-hepatic tissues, in particular in the regulation of bone and vascular metabolism. The accurate measurement of vitamin K status in humans is still a critical issue. Along with indirect assays, such as the undercarboxylated fractions of vitamin K-dependent proteins [prothrombin, osteocalcin (OC), and matrix gla protein], the direct analysis of blood levels of phylloquinone and menaquinones forms might be considered a more informative and direct method for assessing vitamin K status. Different methods for direct quantification of vitamin K serum levels are available. High-performance liquid chromatography (HPLC) methods coupled with post-column reduction procedures and fluorimetric or electrochemical detection are commonly used for food and blood analysis of phylloquinone, but they show some limitations when applied to the analysis of serum menaquinones because of interferences from triglycerides. Recent advancements include liquid chromatography tandem mass spectrometry (LCMS/MS) detection, which assures higher specificity. The optimization and standardization of these methods requires specialized laboratories. The variability of results observed in the available studies suggests the need for further investigations to obtain more accurate analytical results.

Relationship Between Low Bone Mineral Density and Fractures With Incident Cardiovascular Disease: A Systematic Review and Meta-Analysis

An increasing evidence base suggests that low bone mineral density (BMD) and fractures are associated with cardiovascular disease (CVD). We conducted a systematic review and meta-analysis summarizing the evidence of low BMD and fractures as risk factors for future CVD. Two independent authors searched major databases from inception to August 1, 2016, for longitudinal studies reporting data on CVD incidence (overall and specific CVD) and BMD status and fractures. The association between low BMD, fractures, and CVD across longitudinal studies was explored by calculating pooled adjusted hazard ratios (HRs) ±95% confidence intervals (CIs) with a random-effects meta-analysis. Twenty-eight studies (18 regarding BMD and 10 fractures) followed a total of 1,107,885 participants for a median of 5 years. Taking those with higher BMD as the reference, people with low BMD were at increased risk of developing CVD during follow-up (11 studies; HR = 1.33; 95%CI, 1.27 to 1.38; I2  = 53%), after adjusting for a median of eight confounders. This finding was confirmed using a decrease in one standard deviation of baseline BMD (9 studies; HR = 1.16; 95% CI, 1.09 to 1.24; I2  = 69%). The presence of fractures at baseline was associated with an increased risk of developing CVD (HR = 1.20; 95% CI, 1.06 to 1.37; I2  = 91%). Regarding specific CVDs, low BMD was associated with an increased risk of developing coronary artery disease, cerebrovascular conditions, and CVD-associated death. Fractures at baseline was associated with an increased risk of cerebrovascular conditions and death due to CVD. In conclusion, low BMD and fractures are associated with a small, but significant increased risk of CVD risk and possibly death. © 2017 American Society for Bone and Mineral Research.

Vitamin K and bone

Vitamin K is mainly known as an agent involved in blood coagulation, maintaining the activity of coagulation factors in the liver. In addition, epidemiological studies suggested that a lack of vitamin K is associated with several diseases, including osteoporosis and vascular calcification. There are two main kinds of vitamin K: Phylloquinone (or PK) and Menaquinones (MKn), both act as co-enzyme of y-glutamyl carboxylase (GGCX) transforming under-carboxylated in carboxylated vitamin K dependent proteins, such as Bone Gla Protein (or Osteocalcin) and Matrix Gla Protein. Recently, Vitamin K was also identified as a ligand of the nuclear steroid and xenobiotic receptor (SXR) (in murine species Pregnane X Receptor: PXR), expressed in osteoblasts. The purpose of this literature review is to evaluate the protective role of Vitamin K in bone and vascular health.

Non-Traditional Aspects of Renal Diets: Focus on Fiber, Alkali and Vitamin K1 Intake

Renal diets for advanced chronic kidney disease (CKD) are structured to achieve a lower protein, phosphate and sodium intake, while supplying adequate energy. The aim of this nutritional intervention is to prevent or correct signs, symptoms and complications of renal insufficiency, delaying the start of dialysis and preserving nutritional status. This paper focuses on three additional aspects of renal diets that can play an important role in the management of CKD patients: the vitamin K1 and fiber content, and the alkalizing potential. We examined the energy and nutrients composition of four types of renal diets according to their protein content: normal diet (ND, 0.8 g protein/kg body weight (bw)), low protein diet (LPD, 0.6 g protein/kg bw), vegan diet (VD, 0.7 g protein/kg bw), very low protein diet (VLPD, 0.3 g protein/kg bw). Fiber content is much higher in the VD and in the VLPD than in the ND or LPD. Vitamin K1 content seems to follow the same trend, but vitamin K2 content, which could not be investigated, might have a different pattern. The net endogenous acid production (NEAP) value decreases from the ND and LPD to the vegetarian diets, namely VD and VLPD; the same finding occurred for the potential renal acid load (PRAL). In conclusion, renal diets may provide additional benefits, and this is the case of vegetarian diets. Namely, VD and VLPD also provide high amounts of fibers and Vitamin K1, with a very low acid load. These features may have favorable effects on Vitamin K1 status, intestinal microbiota and acid-base balance. Hence, we can speculate as to the potential beneficial effects on vascular calcification and bone disease, on protein metabolism, on colonic environment and circulating levels of microbial-derived uremic toxins. In the case of vegetarian diets, attention must be paid to serum potassium levels.

Measurement of plasma vitamin K1 (phylloquinone) and K2 (menaquinones-4 and -7) using HPLC-tandem mass spectrometry

BACKGROUND

Given the growing interest in the health benefits of vitamin K, there is great need for development of new high-throughput methods for quantitative determination of vitamin K in plasma. We describe a simple and rapid method for measurement of plasma vitamin K1 (phylloquinone [PK]) and K2 (menaquinones [MK]-4 and -7). Furthermore, we investigated the association of fasting plasma vitamin K with functional vitamin K insufficiency in renal transplant recipients (RTR).

METHODS

We used HPLC-tandem mass spectrometry with atmospheric pressure chemical ionization for measurement of plasma PK, MK-4, and MK-7. Solid-phase extraction was used for sample clean-up. Mass spectrometric detection was performed in multiple reaction monitoring mode. Functional vitamin K insufficiency was defined as plasma desphospho-uncarboxylated matrix Gla protein (dp-ucMGP) >500 pmol/L.

RESULTS

Lower limits of quantitation were 0.14 nmol/L for PK and MK-4 and 4.40 nmol/L for MK-7. Linearity up to 15 nmol/L was excellent. Mean recoveries were >92%. Fasting plasma PK concentration was associated with recent PK intake (ρ=0.41, p=0.002) and with plasma MK-4 (ρ=0.49, p<0.001). Plasma PK (ρ=0.38, p=0.003) and MK-4 (ρ=0.46, p<0.001) were strongly correlated with plasma triglyceride concentrations. Furthermore, we found that MK-4-triglyceride ratio, but not PK-triglyceride ratio, was significantly associated with functional vitamin K insufficiency (OR 0.22 [0.07-0.70], p=0.01) in RTR.

CONCLUSIONS

The developed rapid and easy-to-use LC-MS/MS method for quantitative determination of PK, MK-4, and MK-7 in human plasma may be a good alternative for the labor-intensive and time-consuming LC-MS/MS methods and enables a higher sample throughput.

The role of vitamin K in vascular calcification of patients with chronic kidney disease

Patients with chronic kidney disease (CKD) are prone to vascular calcification. Pathogenetic mechanisms of vascular calcifications have been broadly studied and discussed such as the role of hyperphosphatemia, hypercalcemia, parathormone, and vitamin D. In recent years, new insights have been gained pointing to vitamin K as a main actor. It has been discovered that vitamin K is an essential cofactor for the activation of matrix Gla protein (MGP), a calcification inhibitor in the vessel wall. Patients with CKD often suffer from vitamin K deficiency, resulting in low active MGP and eventually a lack of inhibition of vascular calcification. Vitamin K supplementation and switching warfarin to new oral anticoagulants are potential treatments. In addition, MGP may have a role as a non-invasive biomarker for vascular calcification.

Optimization of Dialysis Catheter Function

Central venous catheters (CVCs) are essential in the management of hemodialysis patients, but they also carry unintended negative consequences and in particular thrombosis and infection, adversely affecting patient morbidity and mortality. This review will focus on the etiology, prevention, and management of CVC-related dysfunction, which is mainly associated with inadequate blood flow. CVC dysfunction is a major cause of inadequate depuration. Thrombus, intraluminal and extrinsic, as well as fibrous connective tissue sheath (traditionally indicated as fibrin sheath) formation play a central role in establishing CVC dysfunction. Thrombolysis with urokinase or recombinant tissue plasminogen activator (rTPA) can be undertaken in the dialysis unit, restoring adequate blood flow in most patients, preserving the existing catheter, and avoiding an interventional procedure. If thrombolytics fail, mainly because of the presence of fibrous connective tissue sheath, catheter exchange with fibrin sheath disruption may be successful and preserve the venous access site. Prevention of CVC dysfunction is important for containing costly pharmacologic and interventional treatments, which also affect patients’ quality of life. Prevention is based on the use of anticoagulant and/or thrombolytic CVC locks, which are only partially effective. Chronic oral anticoagulation with warfarin has also been proposed, but its use for this indication is controversial and its overall risk-benefit profile has not been clearly established.

Calcimimetic and vitamin D analog use in hemodialyzed patients is associated with increased levels of vitamin K dependent proteins

Matrix Gla protein (MGP) and bone Gla protein (BGP) are two vitamin K-dependent proteins (VKDPs) involved in the regulation of vascular calcification (VC). We carried out a secondary analysis of the VIKI study to evaluate associations between drug consumption and VKDP levels in 387 hemodialyzed patients. The VIKI study assessed the prevalence of vitamin K deficiency in hemodialysis patients. We evaluated drug consumption, determined BGP and MGP levels, and verified the presence of any vertebral fractures (VF) and VC by spine radiographs. Total BGP levels were twice as high with calcimimetics versus no calcimimetics (290 vs. 158.5 mcg/L, p < 0.0001) and 69 % higher with vitamin D analogs (268 vs. 159 mcg/L, p < 0.0001). Total MGP was 19 % higher with calcimimetics (21.5 vs. 18.1 mcg/L, p = 0.04) and 54 % higher with calcium acetate (27.9 vs. 18.1 mcg/L, p = 0.003); no difference was found with vitamin D analogs (21.1 vs. 18.3 mcg/L, p = 0.43). Median Total BGP level was 29 % lower in patients with ≥1 VF (151 vs. 213 mcg/L, p = 0.0091) and 36 % lower in patients with VC (164 vs. 262.1 mcg/L, p = 0.0003). In non-survivors, median BGP and MGP were lower, but only for MGP this difference reached the statistical significance (152 vs. 191 mcg/L, p = 0.20 and 15.0 vs. 19.7 mcg/L, p = 0.02, respectively). Pending studies on vitamin K supplementation, calcimimetics, and vitamin D analogs may play a role in preserving vitamin K-dependent protein activity, thus contributing to bone and vascular health in CKD patients.

Plausible ergogenic effects of vitamin D on athletic performance and recovery

The purpose of this review is to examine vitamin D in the context of sport nutrition and its potential role in optimizing athletic performance. Vitamin D receptors (VDR) and vitamin D response elements (VDREs) are located in almost every tissue within the human body including skeletal muscle. The hormonally-active form of vitamin D, 1,25-dihydroxyvitamin D, has been shown to play critical roles in the human body and regulates over 900 gene variants. Based on the literature presented, it is plausible that vitamin D levels above the normal reference range (up to 100 nmol/L) might increase skeletal muscle function, decrease recovery time from training, increase both force and power production, and increase testosterone production, each of which could potentiate athletic performance. Therefore, maintaining higher levels of vitamin D could prove beneficial for athletic performance. Despite this situation, large portions of athletic populations are vitamin D deficient. Currently, the research is inconclusive with regards to the optimal intake of vitamin D, the specific forms of vitamin D one should ingest, and the distinct nutrient-nutrient interactions of vitamin D with vitamin K that affect arterial calcification and hypervitaminosis. Furthermore, it is possible that dosages exceeding the recommendations for vitamin D (i.e. dosages up to 4000-5000 IU/day), in combination with 50 to 1000 mcg/day of vitamin K₁ and K₂ could aid athletic performance. This review will investigate these topics, and specifically their relevance to athletic performance.

Canola and hydrogenated soybean oils accelerate ectopic bone formation induced by implantation of bone morphogenetic protein in mice

Canola oil (Can) and hydrogenated soybean oil (H2-Soy) are commonly used edible oils. However, in contrast to soybean oil (Soy), they shorten the survival of stroke-prone spontaneously hypertensive (SHRSP) rats. It has been proposed that the adverse effects of these oils on the kidney and testis are caused at least in part by dihydro-vitamin K (VK) 1 in H2-Soy and unidentified component(s) in Can. Increased intake of dihydro-VK1 is associated with decreased tissue VK2 levels and bone mineral density in rats and humans, respectively. The aim of the present study was to determine the effects of these oils on bone morphogenetic protein (BMP)-induced ectopic bone formation, which is promoted by VK2 deficiency, in relation to the role of VK in the γ-carboxylation of osteocalcin and matrix Gla protein. A crude extract of BMPs was implanted into a gap in the fascia of the femoral muscle in 5-week-old mice maintained on a Soy, Can, or H2-Soy diet. Newly formed bone volume, assessed by three-dimensional X-ray micro-computed tomography and three-dimensional reconstruction imaging for bone, was 4-fold greater in the Can and H2-Soy groups than in the Soy group. The plasma carboxylated osteocalcin (Gla-OC) and total OC (Gla-OC plus undercarboxylated osteocalcin [Glu-OC]) levels were significantly lower in the Can group than in the Soy group (p < 0.05). However, these levels did not significantly differ between the H2-Soy and Soy groups. The plasma Gla-OC/Glu-OC ratio in the Can and H2-Soy groups was significantly lower (in Can; p = 0.044) or was almost significantly lower (in H2-Soy; p = 0.053) than that in the Soy group. In conclusion, Can and H2-Soy accelerated BMP-induced bone formation in mice to a greater extent than Soy. Further research is required to evaluate whether the difference in accelerated ectopic bone formation is associated with altered levels of VK2 and VK-dependent protein(s) among the three dietary groups.

Alpha Klotho and phosphate homeostasis

The Klotho family consists of three single-pass transmembrane proteins—αKlotho, βKlotho and γKlotho. Each of them combines with fibroblast growth factor (FGF) receptors (FGFRs) to form receptor complexes for various FGF’s. αKlotho is a co-receptor for physiological FGF23 signaling and appears essential for FGF23-mediated regulation of mineral metabolism. αKlotho protein also plays a FGF23-independent role in phosphate homeostasis. Animal experimental studies and clinical observations have demonstrated that αKlotho deficiency leads to severe hyperphosphatemia; moderate elevation of αKlotho reduces serum phosphate and extremely high αKlotho induces hypophosphatemia and high-FGF23. αKlotho maintains circulating phosphate in a narrow range by modulating intestinal phosphate absorption, urinary phosphate excretion by the kidney, and phosphate distribution into bone rather than soft tissue in concerted interaction with other calciophosphotropic hormones such as PTH, FGF23, and 1,25-(OH)₂ vitamin D. The role of αKlotho in maintenance of phosphate homeostasis is mediated by direct suppression of Na-dependent phosphate cotransporters in target organs. Therefore, αKlotho manipulation may be a novel strategy for genetic and acquired phosphate disorders and for medical conditions with αKlotho deficiency such as chronic kidney disease in future.

The relationship between the Spine Deformity Index, biochemical parameters of bone metabolism and vascular calcifications: results from the Epidemiological VERtebral FRACtures iTalian Study (EVERFRACT) in dialysis patients

BACKGROUND

The Spine Deformity Index (SDI) is a measure of vertebral fractures (VFs), providing information on both their number and severity.

METHODS

We evaluated the relationships between SDI and clinical, biochemical and arterial calcification parameters in 387 hemodialysis (HD) patients. VFs, assessed by quantitative vertebral morphometry, and vascular calcifications were identified in the same lateral spinal X-ray. To improve the detection of fracture severity, we created a corrected SDI (c-SDI), by dividing SDI for the number of VFs. We assessed routine biochemistry, bone-Gla-protein (BGP), undercaboxylated BGP (ucBGP), and matrix-Gla-protein (MGP).

RESULTS

VFs prevalence was 55.3%. HD patients with a SDI >1 were more frequently males (p<0.05), and had lower BGP (p<0.01). Patients with a c-SDI >1 had higher LDL-cholesterol (p<0.05) and lower ucBGP (p<0.05) and MGP (p<0.05). Calcifications of the abdominal aorta (AAoC) were more frequent in patients with SDI >1 (p<0.05) and with c-SDI >1 (p<0.05). Multivariate logistic regression showed that male sex (OR 1.86, CI 1.20-2.91), age (OR 1.03, CI 1.01-1.05) and albumin ≥3.5 g/dL (OR 0.54, CI 0.31-0.93) were predictors of a SDI >1. Age (OR 1.05, CI 1.03-1.07), LDL-cholesterol (OR 1.74, CI 1.04-2.92) and ucBGP (OR 0.35, CI 0.18-0.70) were associated with c-SDI >1.

CONCLUSIONS

We conclude that the severity of VFs was associated with age, atherogenic factors and bone metabolism markers.

Vitamin K status in chronic kidney disease

The purpose of this review is to summarize the research to date on vitamin K status in chronic kidney disease (CKD). This review includes a summary of the data available on vitamin K status in patients across the spectrum of CKD as well as the link between vitamin K deficiency in CKD and bone dynamics, including mineralization and demineralization, as well as ectopic mineralization. It also describes two current clinical trials that are underway evaluating vitamin K treatment in CKD patients. These data may inform future clinical practice in this population.

Innovative technique for the direct determination of proteins in calcified aortic valves

Aortal valve mineralization very frequently causes a genesis of aortic stenosis, which is the most often surgically treated heart disease. Hydroxyapatite deposits have been identified as one of the causes leading to the loss of elasticity of the aortic valves. It is known that phosphates/calcium is accumulated in valve tissues during mineralization, but the mechanism of this process remains unclear. The work is focused mainly on the study of protein composition of mineralized aortic valves by nano-liquid chromatography electrospray ionization in a quadrupole orthogonal acceleration time-of-flight mass spectrometry. New methodological approach based on direct enzymatic digestion of proteins contained in hydroxyapatite deposits was developed for the study of pathological processes connected with osteogenesis. Our objectives were to simplify the traditional analytical protocols of sample preparation and to analyze the organic components of the explanted aortic valves for significant degenerative aortic stenosis. The study of aortic valve mineralization on the molecular level should contribute to understanding this process, which should consequently lead to effective prevention as well as to new ways of treatment of this grave disease.

Does menaquinone participate in brain astrocyte electron transport?

Quinone compounds act as membrane resident carriers of electrons between components of the electron transport chain in the periplasmic space of prokaryotes and in the mitochondria of eukaryotes. Vitamin K is a quinone compound in the human body in a storage form as menaquinone (MK); distribution includes regulated amounts in mitochondrial membranes. The human brain, which has low amounts of typical vitamin K dependent function (e.g., gamma carboxylase) has relatively high levels of MK, and different regions of brain have different amounts. Coenzyme Q (Q), is a quinone synthesized de novo, and the levels of synthesis decline with age. The levels of MK are dependent on dietary intake and generally increase with age. MK has a characterized role in the transfer of electrons to fumarate in prokaryotes. A newly recognized fumarate cycle has been identified in brain astrocytes. The MK precursor menadione has been shown to donate electrons directly to mitochondrial complex III.

HYPOTHESIS

Vitamin K compounds function in the electron transport chain of human brain astrocytes.

High prevalence of vertebral fractures assessed by quantitative morphometry in hemodialysis patients, strongly associated with vascular calcifications

Few studies have provided information on the prevalence of vertebral fractures (VFs) and their risk factors in hemodialysis patients. A multicenter, cross-sectional, observational study was carried out to assess the prevalence of VFs and vascular calcifications (VCs) in 387 hemodialysis patients (mean age 64.2 ± 14.1 years, 63 % males) and in a control group of 51 osteoporotic subjects. Biochemical tests included 25(OH) vitamin D, bone Gla protein (total and undercarboxylated), and total matrix Gla protein. Vertebral quantitative morphometry was carried out centrally for the detection of VF, defined as reduction by ≥20 % of one of the vertebral body dimensions. In the same radiograph, aortic and iliac VC scores were calculated. Prevalence of VF was 55.3 % in hemodialysis patients and 51.0 % in the control group. Multivariate analysis disclosed that male gender (59.8 vs. 47.6 %, p = 0.02; OR = 1.78, 95 % CI 1.15-2.75) and age (mean ± SD 66.7 ± 13.1 vs. 61.0 ± 14.7 years, p < 0.001; OR = 1.03, 95 % CI 1.01-1.05) were significantly associated with VF. The prevalence of aortic VC was significantly higher in hemodialysis patients than in controls (80.6 vs. 68.4 %, p = 0.001). The factors with the strongest association with VC, apart from atrial fibrillation, were serum 25(OH)vitamin D levels below 29 ng/mL for aortic VC (OR = 1.85, 95 % CI 1.04-3.29) and VF both for aortic (OR = 1.77, 95 % CI 1.00-3.14) and iliac (OR = 1.96, 95 % CI 1.27-3.04) VC. In conclusion, the prevalence of VF, especially in males, and VC, in both genders, is high in hemodialysis patients. VF is associated with VC. Vitamin D deficiency is also associated with VC. Further longitudinal studies are warranted to investigate fractures in renal patients.

Massively Calcified Intravascular Cast after Removal of a Tunneled Central Vein Catheter for Hemodialysis

Vascular calcifications usually affect the arteries, while central vein calcifications are rare.

A 45-year-old hemodialysis patient underwent a chest CT scan before central vein catheterization required for arteriovenous

access thrombosis, in July 2011. He was on hemodialysis since 1995 and from 2005 on warfarin treatment because of repeated

thrombosis and dysfunction of arteriovenous fistula and central vein catheters (CVC). A previous tunneled CVC placed in the left external jugular vein was removed in December 2010.

Eight months later a chest CT scan showed a 79-mm irregular, linear, tubular radiopaque density in the superior vena cava and left brachiocephalic vein. The possibility of a retained catheter fragment was considered, but the final diagnosis was: calcified “cast” adherent to the vessel wall. This is the first report of an intravenous calcified “cast” (originating from peri-catheter calcification) retained after removal of a tunneled dialysis CVC.

This finding is significant because it mimics a retained catheter fragment possibly leading to misdiagnosis and exposing patients to additional risk for unnecessary retrieving interventions. Catheter removal or over the wire substitution in the presence of a calcified cast could also be considered a risky procedure. Retained calcified cast should be included among the long-term complications of hemodialysis CVCs. At the time of publication, the patient is alive without any complication related to the pathology reported.

Vitamin K, vertebral fractures, vascular calcifications, and mortality: VItamin K Italian (VIKI) dialysis study

Vitamin K (vitamin K1 or phylloquinone and vitamin K2, a series of menaquinones [MKs]) is involved in the production of bone and matrix amino acid γ-carboxy-glutamic acid (Gla) proteins, regulating bone and vascular calcification. Low vitamin K concentrations are associated with increased risks of fractures and vascular calcification, and frequent complications in hemodialysis patients. We carried out an observational study to establish the prevalence of vitamin K deficiency and to assess the relationship between vitamin K status, vertebral fractures, vascular calcification, and survival in 387 patients on hemodialysis for ≥1 year. We determined plasma levels of vitamin K compound, bone-Gla-protein, matrix-Gla-protein, and routine biochemistry. Vertebral fractures (reduction in vertebral body height by ≥20%) and aortic and iliac calcifications were also investigated in a spine (D(5) -L(4)) radiograph. Three-year patient survival was analyzed. Important proportions of patients had deficiency of MK7 (35.4%), vitamin K1 (23.5%), and MK4 (14.5%). A total of 55.3% of patients had vertebral fractures, 80.6% had abdominal aorta calcification, and 56.1% had iliac calcification. Vitamin K1 deficiency was the strongest predictor of vertebral fractures (odds ratio [OR], 2.94; 95% confidence interval [CI], 1.38-6.26). MK4 deficiency was a predictor of aortic calcification (OR, 2.82; 95% CI, 1.14-7.01), whereas MK5 deficiency actually protected against it (OR, 0.38; 95% CI, 0.15-0.95). MK7 deficiency was a predictor of iliac calcification (OR, 1.64; 95% CI, 1.03-2.60). The presence of vertebral fractures was also a predictor of vascular calcifications (OR, 1.76; 95% CI, 1.00-3.08). Increased alkaline phosphatase and C reactive protein (CRP), age, and cerebrovascular events were predictors of mortality. Our study suggests that the vitamin K system may be important for preserving bone mass and avoiding vascular calcification in hemodialysis patients, pointing out a possible role of vitamin K in bone and vascular health. Based on our results, we suggest that the general population should also be studied for vitamin K deficiency as a possible cause of both vertebral fractures and vascular calcification.

Vitamin K(2) improves renal function and increases femoral bone strength in rats with renal insufficiency

Renal insufficiency induces cortical bone loss in rats. The present study examined the influence of vitamin K(2) on renal function, cortical bone mass, and bone strength in rats with renal insufficiency. Thirty male Sprague-Dawley rats (8 weeks old) were randomized by the stratified weight method to the following three groups of 10 animals each: sham operation (control), 5/6 nephrectomy, and 5/6 nephrectomy + oral vitamin K(2) (menaquinone-4, menatetrenone, 30 mg/kg, 5 days/week). Treatment was initiated 10 days after surgery. After 6 weeks of treatment, samples of serum, urine, and bone (femur and tibia) were obtained. Renal function was evaluated, bone histomorphometric analysis was performed on the tibial diaphysis, and the bone mineral density (BMD) and mechanical strength of the femoral diaphysis were determined by peripheral quantitative computed tomography and a three-point bending test, respectively. Nephrectomy induced renal dysfunction, as indicated by increased levels of serum creatinine and urea nitrogen along with a decrease of creatinine clearance; and it also decreased BMD without significantly affecting bone strength at the femoral diaphysis. Vitamin K(2) improved renal function parameters but did not significantly influence BMD at the femoral diaphysis. However, vitamin K(2) decreased the bone marrow area of the tibial diaphysis and increased the stiffness of the femoral diaphysis. These findings suggest that administration of vitamin K(2) improves renal function and increases cortical bone strength without altering BMD in rats with renal insufficiency.