Kidney Function-Dependence of Vitamin K-Status Parameters: Results from the TransplantLines Biobank and Cohort Studies.

High circulating dephosphorylated (dp) uncarboxylated (uc) matrix Gla protein (MGP) and uc osteocalcin (OC) concentrations are regarded as markers of vitamin K-deficiency. However, because MGP and OC are small molecules, they may potentially pass the glomerulus, and their blood concentrations may strongly depend on kidney function. However, many studies with vitamin K-status parameters do not structurally adjust for baseline kidney function, and detailed studies on kidney function-dependence of vitamin K-status markers are lacking. We therefore measured plasma dp-ucMGP using a chemiluminescent assay in 578 kidney transplant recipients (41% females, age 56 ± 13y, 7.5 (3.2 to 13.7)y after transplantation, eGFR 49 ± 17 mL/min/1.73 m2) participating in the prospective TransplantLines Cohort Studies. Additionally, dp-carboxylated MGP, ucOC and carboxylated OC were measured using ELISA in plasma of a subgroup of 60 participants. Finally, dp-ucMGP was measured in a separate cohort of 124 kidney transplant recipients before and three months after kidney transplantation. Dp-ucMGP positively correlated with creatinine, cystatin C, and negatively with eGFR (Spearman's ρ 0.54, 0.60, and -0.54, respectively, p < 0.001 for all), and each 10 mL/min/1.73 m2 increase in eGFR was associated with a 14.0% lower dp-ucMGP. Additionally, dp-ucMGP strongly declined after kidney transplantation (pretransplantation: 1252 (868 to 1744) pmol/L to posttransplantation: 609 (451 to 914) pmol/L, p < 0.001). Proportions of dp-ucMGP over total MGP and ucOC over total OC were not associated with eGFR. This study highlights that dp-ucMGP is strongly associated with kidney function, and that levels strongly decrease after kidney transplantation. We therefore propose adequate adjustment for kidney function, or the use of kidney function-independent parameters such as proportion of uncarboxylated MGP or OC in the assessment of vitamin K-status in clinical practice and research.

The evaluation of vitamin K status in children with febrile seizure.

BACKGROUND: Febrile seizure is the most common neurological disorder in childhood. The exact pathophysiology of febrile seizures is unknown. Recent studies showed the role of vitamin K in nonhematological and inflammatory disorders. This study aimed to investigate the serum vitamin K levels in children with febrile seizures. AIMS: To evaluate vitamin K levels in children with febrile seizures. STUDY DESIGN: Prospective case-control study. METHODS: This multicenter study examined representative populations in 8 different cities in Turkey between April 1, 2018 and April 1, 2019. Blood samples were taken from all children at presentation. Vitamin K1, vitamin K2, tumor necrosis factor-alpha, interleukin 1 beta, and interleukin 6 levels were determined by enzyme-linked immunosorbent assay. RESULTS: A total of 155 children were included in the study-84 children with febrile seizures and 71 children in febrile control group. Serum vitamin K1 and vitamin K2 levels were also higher in children with febrile seizures than in the controls. The results of statistical analysis showed that vitamin K1 and vitamin K2 levels were correlated with tumor necrosis factor-alpha, interleukin 1 beta, and interleukin 6 levels. The median vitamin K1 and vitamin K2 levels of children experiencing their first febrile seizure were higher than those in children with recurrent febrile seizures. Type of febrile seizure has no effect on serum vitamin K1 and vitamin K2 levels. CONCLUSION: In children with febrile seizures, vitamin K levels are higher than those in the control group. These new findings may contribute to elucidating the etiopathogenesis of febrile seizures.

Vitamin K deficiency: an emerging player in the pathogenesis of vascular calcification and an iatrogenic consequence of therapies in advanced renal disease.

Vascular calcification is a known complication of chronic kidney disease (CKD). The prevalence of vascular calcification in patients with non-dialysis-dependent CKD stages 3-5 has been shown to be as high as 79% (20). Vascular calcification has been associated with increased risk for mortality, hospital admissions, and cardiovascular disease (6, 20, 50, 55). Alterations in mineral and bone metabolism play a pivotal role in the pathogenesis of vascular calcification in CKD. As CKD progresses, levels of fibroblast growth factor-23, parathyroid hormone, and serum phosphorus increase and levels of 1,25-(OH)2 vitamin D decrease. These imbalances have been linked to the development of vascular calcification. More recently, additional factors have been found to play a role in vascular calcification. Matrix G1a protein (MGP) in its carboxylated form (cMGP) is a potent inhibitor of vascular calcification. Importantly, carboxylation of MGP is dependent on the cofactor vitamin K. In patients with CKD, vitamin K deficiency is prevalent and is exacerbated by warfarin, which is frequently used for anticoagulation. Insufficient bioavailability of vitamin K reduces the amount of cMGP available, and, therefore, it may lead to increased risk of vascular calcification. In vitro studies have shown that in the setting of a high-phosphate environment and vitamin K antagonism, human aortic valve interstitial cells become calcified. In this article, we discuss the pathophysiological consequence of vitamin K deficiency in the setting of altered mineral and bone metabolism, its prevalence, and clinical implications in patients with CKD.

Switching from Warfarin to rivaroxaban induces sufficiency of vitamin K and reduction of arterial stiffness in patients with atrial fibrillation.

Use of chronic vitamin K antagonist (VKA) induces a long-term deficiency of vitamin K, which may cause arterial stiffness and bone-related disease. Switching from VKA to rivaroxaban could induce rapid sufficiency of vitamin K and improvement of arterial stiffness. The K2 SUMMIT-3 study is a multicenter, open-label, prospective, and randomized design. Patients with atrial fibrillation who have been taking VKA for more than 6 months but less than 10 years were randomly assigned to two groups; those switching from VKA to rivaroxaban and those continuing with VKA medication. The primary endpoint was the percentage difference of brachial-ankle pulse wave velocity (baPWV) in 3 months. A total of 77 patients were randomly assigned to receive rivaroxaban (n = 38) or VKA (n = 39). The average age was 74 ± 9 years. The duration for which VKA was prescribed prior to randomization was 90 ± 87 months.Abnormally high levels of Des-gamma carboxyprothrombin (PIVKA-II) or uncarboxylated osteocalcin (ucOC) indicating vitamin K insufficiency were observed in 100% or 82% of the patients at baseline but it reduced to 2% (p < 0.0001) or 55% (p = 0.01) at 3 months in the rivaroxaban group. To the contrary, theses data had no changes in the VKA group. The percentage difference in baPWV was - 1.4 ± 10.0% vs. 3.5 ± 14.7% in the rivaroxaban and the VKA groups, respectively. (p = 0.02). Switching from VKA to rivaroxaban resulted in rapid sufficiency of vitamin K and reduction of arterial stiffness in 3 months.

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.

The Vitamin K Metabolome in Chronic Kidney Disease.

The purpose of this review is to summarize the research to date on the impact of chronic kidney disease (CKD) on the vitamin K metabolome. Vitamin K-dependent proteins contribute to cardiovascular disease (CVD) prevention via the prevention of ectopic mineralization. Sub-clinical vitamin K deficiency is common in CKD patients, and evidence suggests that it may contribute to the CVD burden in this population. Research from animal models suggests that CKD alters tissue measures of the two predominant forms of vitamin K: KI and MK-4. The expression and/or activity of enzymes that regulate the recycling of vitamin K and the carboxylation of vitamin K-dependent proteins also appear to be altered in CKD. Evidence suggests that statins, a common pharmaceutical prescribed to CKD patients to prevent cardiovascular events, may impact the metabolism of vitamin K and therefore contribute to its relative inefficiency at preventing CVD in this population as kidney disease progresses. Human research on the tissue vitamin K metabolome in CKD patients is lacking.

Synergistic effect of low K and D vitamin status on arterial stiffness in a general population.

Both vitamins K and D are nutrients with pleiotropic functions in human tissues. The metabolic role of these vitamins overlaps considerably in calcium homeostasis. We analyzed their potential synergetic effect on arterial stiffness. In a cross-sectional study, we analyzed aortic pulse wave velocity (aPWV) in 1023 subjects from the Czech post-MONICA study. Desphospho-uncarboxylated matrix γ-carboxyglutamate protein (dp-ucMGP), a biomarker of vitamin K status, was measured by sandwich ELISA and 25-hydroxyvitamin D3 (25-OH-D3) by a commercial immunochemical assay. In a subsample of 431 subjects without chronic disease or pharmacotherapy, we detected rs2228570 polymorphism for the vitamin D receptor. After adjustment for confounders, aPWV was independently associated with both factors: dp-ucMGP [ß-coefficient(S.E.M.)=13.91(4.87); P=.004] and 25-OH-D3 [0.624(0.28); P=.027]. In a further analysis, we divided subjects according to dp-ucMGP and 25-OH-D3 quartiles, resulting in 16 subgroups. The highest aPWV had subjects in the top quartile of dp-ucMGP plus bottom quartile of 25-OH-D3 (i.e., in those with insufficient status of both vitamin K and vitamin D), while the lowest aPVW had subjects in the bottom quartile of dp-ucMGP plus top quartile of 25-OH-D3 [9.8 (SD2.6) versus 6.6 (SD1.6) m/s; P<.0001]. When we compared these extreme groups of vitamin K and D status, the adjusted odds ratio for aPWV≥9.3 m/s was 6.83 (95% CI:1.95-20.9). The aPWV was also significantly higher among subjects bearing the GG genotype of rs2228570, but only in those with a concomitantly poor vitamin K status. In conclusion, we confirmed substantial interaction of insufficient K and D vitamin status in terms of increased aortic stiffness.

Vitamin K: from coagulation to calcification.

Vitamin K is not only essential for the synthesis of coagulation factors in the liver, but it also strengthens the bones and prevents calcification of the arteries. These effects are mediated through the same mechanism, i.e. carboxylation of Gla target proteins. The discovery of novel Gla proteins that are not associated with blood coagulation or calcium metabolism indicates that vitamin K has additional effects in the pancreas and the central nervous system, for example. As dietary supplements, vitamin K1 of plant origin and vitamins K2 of bacterial origin may exert different effects.

Vitamin K and musculoskeletal health in postmenopausal women.

Aside from its important role in blood clotting, vitamin K is an important dietary factor in regulating bone and cartilage mineralization. The vitamin K requirements to maintain musculoskeletal health may be more than the current recommendations and subclinical vitamin K deficiency may be involved in the pathogenesis of osteoporosis and osteoarthritis. Observational studies suggest that diets low in vitamin K are associated with increased risk of fractures and osteoarthritis in older adults. However, so far randomized controlled trials of vitamin K supplementation in Caucasian populations have not shown clinically significant improvements in bone mineral density at major skeletal sites. Supplementation with vitamin K may reduce the risk of fractures, but this conclusion comes from clinical trials with methodological limitations. At this time, only one randomized controlled trial has examined the effect of vitamin K supplementation on radiographic hand osteoarthritis and found no overall effect. Large well-designed randomized controlled trials are needed to compare the efficacies of vitamin K1 and K2 on fractures and osteoarthritis among older adults. In summary, currently there is not enough evidence to recommend the use of vitamin K supplements for the prevention of bone loss, fractures, or osteoarthritis in postmenopausal women.

Cardiovascular effects of cholecalciferol treatment in dialysis patients--a randomized controlled trial.

BACKGROUND: Patients on chronic dialysis are at increased risk of vitamin D deficiency. In observational studies plasma 25-hydroxyvitamin D (p-25(OH) D) levels are inversely correlated with plasma BNP and adverse cardiovascular outcomes. Whether a causal relation exists has yet to be established. The aim of this study was to test the hypothesis that cholecalciferol supplementation improves cardiac function and reduces blood pressure (BP) and pulse wave velocity (PWV) in patients on chronic dialysis. METHODS: In a randomized, placebo-controlled, double-blind study, we investigated the effect of 75 µg (3000 IU) cholecalciferol daily for 6 months, in patients on chronic dialysis. We performed two-dimensional echocardiography, with doppler and tissue-doppler imaging, 24-h ambulatory BP (24-h BP), PWV, augmentation index (AIx), central BP (cBP) and brain natriuretic peptide (BNP) measurements at baseline and after 6 months. RESULTS: Sixty-four patients were allocated to the study. Fifty dialysis patients with a mean age of 68 years (range: 46-88) and baseline p-25(OH) D of 28 (20;53) nmol/l completed the trial. Cholecalciferol increased left ventricular (LV) volume, but had no impact on other parameters regarding LV structure or left atrial structure. LV systolic function, LV diastolic function, PWV, cBP, AIx and BNP were not changed in placebo or cholecalciferol group at follow-up. 24-h BP decreased significantly in placebo group and tended to decrease in cholecalciferol group without any difference between treatments. CONCLUSION: Six months of cholecalciferol treatment in patients on chronic dialysis did not improve 24-h BP, arterial stiffness or cardiac function. TRIAL REGISTRATION: NCT01312714, Registration Date: March 9, 2011.

The realm of vitamin K dependent proteins: shifting from coagulation toward calcification.

In the past few decades vitamin K has emerged from a single-function "haemostasis vitamin" to a "multi-function vitamin." The use of vitamin K antagonists (VKA) inevitably showed that the inhibition was not restricted to vitamin K dependent coagulation factors but also synthesis of functional extrahepatic vitamin K dependent proteins (VKDPs), thereby eliciting undesired side effects. Vascular calcification is one of the recently revealed detrimental effects of VKA. The discovery that VKDPs are involved in vascular calcification has propelled our mechanistic understanding of this process and has opened novel avenues for diagnosis and treatment. This review addresses mechanisms of VKDPs and their significance for physiological and pathological calcification.

Vitamin K and bone health in older adults.

Vitamin K is one of several nutrients that have been linked with bone health. In particular, there is an emerging literature regarding the questionable efficacy of vitamin K supplementation in reducing age-related bone loss. This review aims to summarize the role of vitamin K in bone health in older adults and discuss the clinical implications from a select few human studies. The evidence for vitamin K supplementation in older adults is mixed. Although the observational studies have shown linkages between vitamin K intake and lower risk of fractures in this population, the current evidence from randomized controlled trials is not strongly supportive of vitamin K supplementation in older adults for the intent of improving bone health.

Osteoporosis in chronic liver disease.

Osteoporosis is a common skeletal complication seen in patients with chronic liver disease. Osteoporosis is usually asymptomatic and, if untreated, can result in fractures and impaired quality of life. For this review, we performed a systematic search of the PubMed database, and all recent peer-reviewed articles regarding the prevalence, pathophysiology, diagnosis, and management of osteoporosis in chronic liver disease were included. The prevalence of osteoporosis varies between 11% and 58% in patients with chronic liver disease and in transplant recipients. The etiology of osteoporosis is multifactorial and only partially understood. Various factors linked to the pathogenesis of bone loss are vitamin D, calcium, insulin growth factor-1, receptor activation of nuclear factor-κB ligand (RANKL), bilirubin, fibronectin, leptin, proinflammatory cytokines, and genetic polymorphisms. Management of osteoporosis involves early diagnosis, identifying and minimizing risk factors, general supportive care, nutrition therapy, and pharmacotherapy. Osteoporosis is diagnosed based on the bone mineral density (BMD) assessment using dual-energy X-ray absorptiometry scan. Measurement of BMD should be considered in all patients with advanced liver disease and in transplant recipients. Vitamin D and calcium supplementation is recommended for all patients with osteoporosis. Specific agents used for treatment of osteoporosis include bisphosphonates, calcitonin, hormonal therapy, and raloxifene. Bisphosphonates have become the mainstay of therapy for osteoporosis prevention and treatment. Prolonged suppression of bone remodeling resulting in atypical fractures has emerged as a significant complication with long-term use of bisphosphonates. Newer treatment agents and better fracture prevention strategies are necessary to prevent and treat osteoporosis.

Bleeding tendency in an adolescent with chronic small bowel obstruction.

We report a case of fat-soluble vitamin deficiency in a 14-year old boy who had chronic duodenal obstruction. He presented with periodic unexplained bleeding tendency. The laboratory results showed positive fat globules in stool and prolonged prothrombin time. His further investigation revealed low plasma vitamin A and undetectable plasma vitamin E. After parenteral vitamin K and oral vitamin A and E supplement, these abnormalities resolved although he still had absent knee jerk. We propose that fat malabsorption and fat-soluble vitamin deficiency can occur after prolonged duodenal obstruction that induce bacterial overgrowth following by bile acid deconjugation. Despite very few case reports, screening for fat malabsorption and fat-soluble vitamin deficiency might be warranted in patients with chronic small bowel obstruction.

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

BACKGROUND: Serum undercarboxylated osteocalcin (ucOC) is a biochemical bone marker of vitamin K insufficiency. It had been reported that bone resorption inhibitors tend to decrease the serum ucOC level in patients with primary osteoporosis. In rheumatoid arthritis (RA) patients, these results have never been reported. AIM: We investigated risk factors which could change serum ucOC level in post-menopausal women with RA (no.=100). SUBJECTS AND METHODS: Twenty patients received no bone resorption inhibitor (control), 30 received raloxifene (RLX), while 50 received alendronate (ALN). This cross-sectional study was limited to patients with low RA disease activity (Disease Activity Score-28 ≤3.2). We measured serum ucOC, and the data were analyzed by multivariable analysis, including ucOC and the other variables. RESULTS: Scheffe's F test demonstrated a significant difference in serum ucOC levels between controls and the RLX group (p<0.01), and between controls and the ALN group (p<0.01). Serum ucOC levels were low in both treated groups. An adjusted multivariate analysis was performed for the variables: bone resorption inhibitor use, serum alkaline phosphatase, glucocorticoid dose, age, estimated glomerular filtration rate and matrix metalloproteinase 3. As a result, serum ucOC inversely correlated with bone resorption inhibitor use (p<0.01) and oral glucocorticoid dose (p<0.01), which were independent risk factors of lowering ucOC. CONCLUSIONS: Bone resorption inhibitors and glucocorticoids were independent risk factors for lowering serum ucOC levels in post-menopausal RA patients.

Association of vitamin K status with adiponectin and body composition in healthy subjects: uncarboxylated osteocalcin is not associated with fat mass and body weight.

Osteocalcin (OC) is a vitamin K-dependent protein found in bone and in circulation. High serum γ-carboxylated OC reflects a high, and high uncarboxylated OC (ucOC) reflects a low vitamin K status. A revolutionary hypothesis is that ucOC acts as a hormone improving glucose handling and reducing fat mass. The objective was to test the logical extrapolation of the ucOC hormone hypothesis to humans that elevated ucOC is associated with higher body weight, BMI and fat mass. In a cross-sectional analysis, the associations of vitamin K status with circulating adiponectin and body composition were investigated in 244 postmenopausal women (study I). The effects of vitamin K treatment on adiponectin, body weight and BMI were investigated in archived samples from forty-two young men and women who received varying doses of menaquinone-7 during 12 weeks (study II) and from a cohort of 164 postmenopausal women who participated in a 3-year placebo-controlled trial on 45 mg menaquinone-4 (MK-4) (study III). No association was found between vitamin K status and circulating adiponectin before or after vitamin K supplementation. A higher carboxylation of OC was significantly correlated with lower body weight, BMI and fat mass of the trunk. Women taking MK-4 maintained their baseline body weight and BMI, whereas women taking placebo showed significant increases in both indices. These findings demonstrate that a high vitamin K status of bone has no effect on circulating adiponectin in healthy people and long-term vitamin K supplementation does not increase weight in healthy postmenopausal women.

Venous thromboembolism in cystic fibrosis.

The incidence of venous thromboembolism (VTE) is increasing in the pediatric population. Individuals with cystic fibrosis (CF) have an increased risk of thrombosis due to central venous catheters (CVCs), as well as acquired thrombophilia secondary to inflammation, or deficiencies of anticoagulant proteins due to vitamin K deficiency and/or liver dysfunction. CVC-associated thrombosis commonly results in line occlusion, but may develop into serious life-threatening conditions such as deep venous thrombosis (DVT), superior vena cava syndrome or pulmonary embolism (PE). Post-thrombotic syndrome (PTS) may be a long complication. Local occlusion of the catheter tip may be managed with instillation of thrombolytics (such as tPA) within the lumen of the catheter; however, CVC-associated thrombosis involving the proximal veins is most often is treated with systemic anticoagulation. Initial treatment with heparin is a standard approach, but thrombolytic therapy, which may carry higher bleeding risks, should be considered for life and limb threatening episodes of VTE. Recommended duration of anticoagulation with low molecular weight heparin (LMWH) or warfarin ranges from 3 to 6 months for major removable thrombotic risks; longer anticoagulation is considered for recurrent thrombosis, major persistent thrombophilia, or the continued presence of a major risk factor such as a CVC. While CVCs are the most common risk for development of VTE in children, studies have not demonstrated a clear benefit with routine use of systemic thromboprophylaxis. The incidence and risk factors of VTE in CF patients will be reviewed and principles of diagnosis and management will be summarized.

Low serum vitamin K in PXE results in defective carboxylation of mineralization inhibitors similar to the GGCX mutations in the PXE-like syndrome.

Soft-tissue mineralization is a tightly regulated process relying on the activity of systemic and tissue-specific inhibitors and promoters of calcium precipitation. Many of these, such as matrix gla protein (MGP) and osteocalcin (OC), need to undergo carboxylation to become active. This post-translational modification is catalyzed by the gammaglutamyl carboxylase GGCX and requires vitamin K (VK) as an essential co-factor. Recently, we described a novel phenotype characterized by aberrant mineralization of the elastic fibers resulting from mutations in GGCX. Because of the resemblance with pseudoxanthoma elasticum (PXE), a prototype disorder of elastic fiber mineralization, it was coined the PXE-like syndrome. As mutations in GGCX negatively affect protein carboxylation, it is likely that inactive inhibitors of calcification contribute to ectopic mineralization in PXE-like syndrome. Because of the remarkable similarities with PXE, we performed a comparative study of various forms of VK-dependent proteins in serum, plasma (using ELISA), and dermal tissues (using immunohistochemistry) of PXE-like and PXE patients using innovative, conformation-specific antibodies. Furthermore, we measured VK serum concentrations (using HPLC) in PXE-like and PXE samples to evaluate the VK status. In PXE-like patients, we noted an accumulation of uncarboxylated Gla proteins, MGP, and OC in plasma, serum, and in the dermis. Serum levels of VK were normal in these patients. In PXE patients, we found similar, although not identical results for the Gla proteins in the circulation and dermal tissue. However, the VK serum concentration in PXE patients was significantly decreased compared with controls. Our findings allow us to conclude that ectopic mineralization in the PXE-like syndrome and in PXE results from a deficient protein carboxylation of VK-dependent inhibitors of calcification. Although in PXE-like patients this is due to mutations in the GGCX gene, a deficiency of the carboxylation co-factor VK is at the basis of the decreased activity of calcification inhibitors in PXE.