Vitamin K plasma levels determination in human health

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.

In Search of Normality for Vitamin K1: Establishing Age-Dependent Reference Intervals in the Danish Population

BACKGROUND

A growing body of evidence suggests that vitamin K has beneficial effects on human health, especially cardiovascular and bone health. Vitamin K1 (phylloquinone), the predominant form of vitamin K in blood, is regarded as an indicator of vitamin K status, but to our knowledge no reference intervals (RIs) have been established for vitamin K1.

METHODS

In this population-based study, vitamin K1 was measured in serum from 3808 Caucasian individuals without diabetes from 26 to 78 years of age. The need for gender- and age-partitioned vitamin K1 reference intervals was evaluated using Lahti's method, and exclusion criteria were defined to obtain as healthy a study group as possible. The excluded subgroups were tested for differences in mean serum vitamin K1 levels. Serum vitamin K1 levels were quantified using an in-house newly developed, validated, and highly sensitive online SPE-LC-MS/MS method with a limit of quantitation of (LOQ) 0.05 nmol/L.

RESULTS

The reference interval for serum vitamin K1 was 0.22 to 3.95 nmol/L for individuals aged 26 to 44 years and 0.35 to 3.70 nmol/L for individuals aged 45 to 78. Similar age-specific reference intervals were established for vitamin K1-triglyceride ratio being 0.20 to 3.16 and 0.31 to 3.44, respectively. No significant difference was found between genders. Serum vitamin K1 was detectable in all serum samples. Individuals with known comorbidity were found to have significantly lower serum vitamin K1 compared to those without comorbidity. Current smokers had lower serum vitamin K1 compared to nonsmokers.

CONCLUSION

Age-dependent reference intervals were established for serum vitamin K1 and vitamin K1-triglyceride ratio in a well-defined, healthy Caucasian population. Lower serum vitamin K1 levels were found in individuals with known comorbidity, suggesting an association between serum vitamin K1 and disease status. Further studies are needed to determine an optimal serum vitamin K1 level.

Prevalence of vitamin K deficiency in older people with hip fracture

Introduction: Vitamin K plays an important role in blood coagulation. Diet is the main source of vitamin K and body stores are depleted in days, hence deficiency is common in malnourished older people. A high proportion of people who sustain a hip fracture are already malnourished, compounded by fasting for surgery which might further increase deficiency. We wanted to explore the prevalence of vitamin K deficiency in hip fracture patients and the impact of a short period of fasting.Methods: In consecutive patients hospitalised with a hip fracture, we measured vitamin K and PIVKA-II (undercarboxylated factor II - a marker of subclinical vitamin K status) on admission and on first post-operative day. We excluded those on anticoagulants.Results: N = 62 participated; 4 had missing pre-op vitamin K samples and n = 3 had no surgery leaving n = 55 with paired samples. Mean age was 80.0 ± 9.6 years, 33% males. Prevalence of subclinical vitamin K deficiency on admission was 36% (20/55) based on reference range of > 0.15µg/L. The proportion with subclinical K deficiency after surgery rose to 64% (35/55), p < 0.05. 13% had detectable PIVKA-II concentrations pre-operatively, 15% did post-operatively. None had abnormal prothrombin time. Vitamin K status was not associated with post-operative haemoglobin drop or transfusion requirements.Conclusion: Prevalence of vitamin K deficiency in hip fracture patients is high and increases further following a short period of fasting. Though no significant impact was noted on peri-operative blood loss, larger studies are warranted to explore this, and the potential role of vitamin K supplements peri-operatively.

Concentrations of Circulating Phylloquinone, but Not Cerebral Menaquinone-4, Are Positively Correlated with a Wide Range of Cognitive Measures: Exploratory Findings in Centenarians

BACKGROUND

Vitamin K (VK) exists in the form of phylloquinone (PK) and menaquinones (MKs). Roles of VK on cognitive health in the elderly are emerging, but there is limited evidence on VK uptake and metabolism in human brain.

OBJECTIVES

The primary objective of this study was to characterize VK distribution in brains of an elderly population with varied cognitive function. In addition, associations among circulating (a biomarker of VK intake) and cerebral VK concentrations and cognition were investigated.

METHODS

Serum or plasma (n = 27) and brain samples from the frontal cortex (FC; n = 46) and the temporal cortex (TC; n = 33) were acquired from 48 decedents (aged 98-107 y; 25 demented and 23 nondemented) enrolled in the Georgia Centenarian Study. Both circulating and brain VK concentrations were measured using HPLC with fluorescence detection. Cognitive assessment was performed within 1 y prior to mortality. Partial correlations between serum/plasma or cerebral VK concentrations and cognitive function were performed, adjusting for covariates and separating by dementia and antithrombotic use.

RESULTS

MK-4 was the predominant vitamer in both FC (mean ± SD = 4.92 ± 2.31 pmol/g, ≥89.15% ± 5.09% of total VK) and TC (4.60 ± 2.11 pmol/g, ≥89.71% ± 4.43% of total VK) regardless of cognitive status. Antithrombotic users had 34.0% and 53.9% lower MK-4 concentrations in FC (P < 0.05) and TC (P < 0.001), respectively. Circulating PK was not correlated with cerebral MK-4 or total VK concentrations. Circulating PK concentrations were significantly associated with a wide range of cognitive measures in nondemented centenarians (P < 0.05). In contrast, cerebral MK-4 concentrations were not associated with cognitive performance, either before or after exclusion of antithrombotic users.

CONCLUSIONS

Circulating VK concentrations are not related to cerebral MK-4 concentrations in centenarians. Cerebral MK-4 concentrations are tightly regulated over a range of VK intakes and cognitive function. Circulating PK may reflect intake of VK-rich foods containing other dietary components beneficial to cognitive health. Further investigation of VK uptake and metabolism in the brain is warranted.

Vitamin K role in mineral and bone disorder of chronic kidney disease

Vitamin K is a key cofactor for the activation of proteins involved in blood coagulation, apoptosis, bone mineralization regulation, and vessel health. Scientific evidence shows an important role of activated osteocalcin and matrix-Gla protein in bone and vessels, markedly affected along the course of chronic kidney disease (CKD). In fact, CKD corresponds to an unique condition of vitamin K deficiency caused by dietary restriction, intestinal dysfunction, and impaired vitamin K recycling. Clinical data suggest that vitamin K status can be modulated and this prompts us to speculate whether patients with CKD might benefit from vitamin K supplementation. However, as important as whether the improvement in vitamin K status would be able to result in better bone quality, less vascular calcification, and lower mortality rates, several issues need to be clarified. These include better standardized methods for measuring vitamin K levels, and definition of the optimal concentration range for supplementation in different subgroups. Here, we review the literature data concerning the impact of vitamin K deficiency and supplementation on CKD-associated mineral and bone disorders (CKD-MBD). We present and discuss the available evidence from basic science and clinical studies, and highlight perspectives for further research.

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.

LC-MS/MS quantitative analysis of phylloquinone, menaquinone-4 and menaquinone-7 in the human serum of a healthy population

A novel application of the liquid chromatography method combined with the triple quadrupole tandem mass spectrometry method was developed for the quantification of vitamin K1 and two forms of vitamin K2 (menaquinone-4, menaquinone-7) in human serum. Total chromatography time for each run was 9 min. Time required for the sample pretreatment procedures was approximately 4 h. The coefficients of variation (CVs) of intra-assay were 10.4%, 3.2 % and 2.3% for vitamin K1 in three levels of quality control samples; were 14.3%, 3.2% and 6.7% for menaquinone-4; and were 11.1%, 6.0% and 7.0% for menaquinone-7. The inter-assay CVs were 12.8%, 11.3% and 7.4% for vitamin K1; were 15.2%, 9.2% and 8.7% for menaquinone-4; and were 13.2%,11.1% and 7.2% for menaquinone-7. No interference was found between K1, menaquinone-4 and menaquinone-7, nor any deuterated internal standards. This method was then used to determine reference values for Caucasian populations of central European origin. Samples were measured from 191 healthy volunteers (51.2 ± 16.2 years (mean ± SD)) and the values concerning K1 were 0.044-1.357 ng/mL for women and 0.030-1.214 ng/mL for men. The values for menaquinone-4 and menaquinone-7 did not exhibit any differences between women and men, and were 0.050-1.598 and 0.074-0.759 ng/mL, respectively.

Vitamin K as a Powerful Micronutrient in Aging and Age-Related Diseases: Pros and Cons from Clinical Studies

Vitamin K is a multifunctional micronutrient implicated in age-related diseases such as cardiovascular diseases, osteoarthritis and osteoporosis. Although vitamin K-dependent proteins (VKDPs) are described to have a crucial role in the pathogenesis of these diseases, novel roles have emerged for vitamin K, independently of its role in VKDPs carboxylation. Vitamin K has been shown to act as an anti-inflammatory by suppressing nuclear factor κB (NF-κB) signal transduction and to exert a protective effect against oxidative stress by blocking the generation of reactive oxygen species. Available clinical evidences indicate that a high vitamin K status can exert a protective role in the inflammatory and mineralization processes associated with the onset and progression of age-related diseases. Also, vitamin K involvement as a protective super-micronutrient in aging and ‘inflammaging’ is arising, highlighting its future use in clinical practice. In this review we summarize current knowledge regarding clinical data on vitamin K in skeletal and cardiovascular health, and discuss the potential of vitamin K supplementation as a health benefit. We describe the clinical evidence and explore molecular aspects of vitamin K protective role in aging and age-related diseases, and its involvement as a modulator in the interplay between pathological calcification and inflammation processes.

Vitamin K and cystic fibrosis: A gordian knot that deserves our attention

Cystic fibrosis (CF) is an inherited genetic disorder with multiorgan involvement. Gastrointestinal tract dysfunction leads to fat and fat-soluble vitamins (A,D,E,K) malabsorption and deficiency of these vitamins. Subclinical vitamin K (VK) deficiency seems to be a common problem in CF patients. However, despite the rest of fat-soluble vitamins being routinely supplemented, this is not a universal clinical practice for VK. Inefficient levels of VK may have significant effects on blood coagulation and bone formation. There are also some data indicating that VK may play a key role on regulation of inflammation. Supplementing CF patients with VK seems rational, but the appropriate dosing regimens are still a matter of debate. This review will try to delineate the problem and communicate the latest opinions on this controversial issue.

Vitamin K Status in Women of Childbearing Years Before or After Bariatric Surgery

BACKGROUND

Vitamin K adequacy has not been widely studied before or after bariatric surgery. Reports of babies born with intracranial bleeds to women after bariatric surgery make this an important vitamin to study in women of childbearing years.

OBJECTIVES

The aim of this study was to assess the functional vitamin K status in 2 groups of women of childbearing age, 1 group seeking bariatric surgery and 1 group post Roux-en-Y gastric bypass (RYGB).

METHODS

In a cross-sectional design, 40 women [19 presurgical and 21 post-RYGB (6-18 mo following surgery)], aged 18-40 y, completed the study. Participants provided a 3-d food intake record and a list of dietary supplements routinely taken. Participants then underwent a commercially available test to measure des-γ-carboxyprothrombin (DCP) concentration as a measure of functional vitamin K status.

RESULTS

Independent-samples t tests (P < 0.05) indicated that there was no significant difference [Sig (2-tailed) 0.821] between the DCP concentrations of the presurgical group and those of the post-RYGB group (mean ± SD DCP: 0.3 ± 0.1 and 0.4 ± 0.2 ng/mL, respectively). Vitamin K intake from food (248 ± 227 and 210 ± 239 μg) and supplements (13 ± 31 and 750 ± 271 μg) showed no linear correlation to DCP (presurgical group: 0.25 and -0.15, respectively; post-RYGB group: 0.13 and 0.05, respectively). Vitamin K intakes for both groups were above the current Institute of Medicine's recommended 90 μg/d for women. Bivariate correlation was conducted on other independent variables with only current BMI for the post-RYGB group having a moderate negative correlation to DCP (-0.54, P < 0.05). No correlation with statistical significance was found between other variables and DCP.

CONCLUSIONS

Although the American Society for Metabolic and Bariatric Surgery recommends DCP as a test to determine vitamin K adequacy, no published studies in pre- or post-RYGB patients have been performed with the current commercially available test, which is not FDA approved as a vitamin K biomarker. Previous studies reporting vitamin K inadequacies based on DCP utilized a different assay than the one currently available. Due to the importance of ensuring adequate maternal concentrations of vitamin K after bariatric surgery in order to prevent intracranial bleeding in babies, more research is needed to determine suitable vitamin K measures.

New Aspects of Vitamin K Research with Synthetic Ligands: Transcriptional Activity via SXR and Neural Differentiation Activity

Vitamin K is classified into three homologs depending on the side-chain structure, with 2-methyl-1,4-naphthoqumone as the basic skeleton. These homologs are vitamin K₁ (phylloquinone: PK), derived from plants with a phythyl side chain; vitamin K₂ (menaquinone-n: MK-n), derived from intestinal bacteria with an isoprene side chain; and vitamin K₃ (menadione: MD), a synthetic product without a side chain. Vitamin K homologs have physiological effects, including in blood coagulation and in osteogenic activity via γ-glutamyl carboxylase and are used clinically. Recent studies have revealed that vitamin K homologs are converted to MK-4 by the UbiA prenyltransferase domain-containing protein 1 (UBIAD1) in vivo and accumulate in all tissues. Although vitamin K is considered to have important physiological effects, its precise activities and mechanisms largely remain unclear. Recent research on vitamin K has suggested various new roles, such as transcriptional activity as an agonist of steroid and xenobiotic nuclear receptor and differentiation-inducing activity in neural stem cells. In this review, we describe synthetic ligands based on vitamin K and exhibit that the strength of biological activity can be controlled by modification of the side chain part.

Vitamin K-what is known regarding bariatric surgery patients: a systematic review

Vitamin K, a fat-soluble vitamin, is involved in blood coagulation, bone mineralization, inhibition of vascular calcification, and regulation of numerous enzyme systems. Patients who undergo bariatric surgery (BS), especially procedures that involve a malabsorptive component, are prone to develop vitamin K deficiency (VKD). The causes of VKD include decreased absorptive surface areas, steatorrhea, bacterial overgrowth, marked reduction of carriers of vitamin K, decrease in vitamin K intake, and modifications of gut microbiota. Data on vitamin K status among BS patients are scarce and the strength of evidence supporting vitamin K supplementation is weak. Thus, this systematic review summarized the scientific literature on vitamin K and examined the status among patients before and after BS, as well as among pregnant women with a history of BS. A MEDLINE/Pubmed and Embase electronic search was performed. After a thorough screening of 204 titles, 19 articles were selected by 2 independent reviewers. Five studies on BS candidates (n = 750), 12 studies after BS (n = 1442), and 4 studies on pregnant woman after BS (n = 83, of them n = 7 from case reports) were included. Results of the current review suggest that patients who undergo major malabsorptive surgeries are at a higher risk of developing VKD and should be better monitored. At this point, it is still unclear whether supplementation of vitamin K is required, and what oral dose or vitamer type should be used to normalize serum levels after different types of bariatric procedures. It should be noted that the current protocols for VKD treatment are still experiential in these patients. It is also unknown at what intervals screening tests for vitamin K should be performed and what assay is most appropriate for screening purposes. Future studies are needed to answer these unresolved issues.

Quantitation of vitamin K1 in serum using online SPE-LC-MS/MS and the challenges of working with vitamin K

Vitamin K1 (phylloquinone) is one of the vitamin Ks. Several studies have previously investigated the role of vitamin K1 status in respect to disease, but without consistent results. Since vitamin K deficiency has been associated with different disease states it is important to develop a biochemical analysis with sufficient sensitivity and a low limit of quantitation (LOQ). The vitamin Ks are very fat-soluble. This non-polar nature has given rise to several challenges during the method development, because vitamin K1 sticks to materials used during the process and is lost during evaporation. We found that reducing the sample preparation as much as possible offline, instead using online SPE-LC-MS/MS improves recovery and gives satisfactory chromatograms. An Protein BEH C4 column, 300 Å (50 × 2.1 mm, 1.7 μm particle size) was used as trap column and a Phenyl-Hexyl-LC-column, 100 Å (100 × 2.1 mm, 2.6 μm particle size) was used as analytical column. The mobile phases consisted of 30 μmol/L NH₄F in water and 30 μmol/L NH₄F in MeOH. A triple quadrupole tandem mass spectrometer with atmospheric pressure chemical ionization (APCI) ion source, positive ion mode, was used to perform the mass spectrometric measurements. The method is simple, highly sensitive and fast. The method was validated for vitamin K1 with good analytical performance. With a LOQ of 0.05 nmol/L it is to our knowledge the vitamin K1 method with lowest LOQ reported to date in the literature. It can easily be automated and applied in a routine diagnostic laboratory. Blood collection tubes with different additives were tested and showed no difference. Stability of vitamin K1 in serum was tested at different temperatures (-20 °C, 4 °C and in light and dark at 20 °C over a period of 30 days) and showed that vitamin K1 is light sensitive in serum even after only one day.

A concise review of quantification methods for determination of vitamin K in various biological matrices

Vitamin K is an essential nutrient in the body and involved in numerous physiological and pathophysiological functions. Both the lack and surplus of vitamin K can put human health at risk. Therefore, it becomes necessary to monitor vitamin K concentrations in different biomatrices through establishing sensitive and specific analytical methods. This review collectively describes an updated overview of the sample pretreatment methodologies and methods for quantitative determination of vitamin K that have been used in last two decades. High Performance Liquid Chromatography (HPLC) is commonly utilized as a standard for separation of vitamin K in combination with different detection including spectroscopic, spectrometric, fluorometric and mass spectroscopy. Recent progress in sample pretreatment technologies and quantitation methodologies have enhanced the ability to identify and quantitate vitamin K in biomatrices to further advance our understanding of the role of this vitamin in human health and disease.

Vitamin K: a nutrient which plays a little-known role in glucose metabolism

PURPOSE OF REVIEW

Type 2 diabetes is one of the most important public health diseases. Type 2 diabetes pathophysiology involves multiple pathways, in which micronutrients could play a role. Among them, interest has grown concerning vitamin K. The purpose of this review is to expose the latest studies on the role of vitamin K in glucose metabolism, a poorly known function of this vitamin.

RECENT FINDINGS

Animal experimentations and human observational and interventional studies were analyzed to evaluate the role of this vitamin in glucose metabolism. Daily intake of vitamin K seems to improve glucose metabolism and low intakes could be involved in type 2 diabetes pathophysiology. Recent data show that vitamin K could act on glucose metabolism via downstream targets such as osteocalcin, growth arrest-specific 6 protein, and matrix Gla protein.

SUMMARY

This review depicts new insights into the role of vitamin K in glucose metabolism regulation and depicts also the probable mechanisms underlying this association. Further studies will be needed to determine the dose and the duration of vitamin K treatment to achieve the strongest metabolic effect. Maybe the best strategy to improve glucose metabolism would be 'cocktails' of micronutrients associating vitamin K.

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.

A Case Report of Intraoperative Coagulopathy Secondary to Chronic Vitamin K Deficiency

Dietary Vitamin K is a well-known anti-hemorrhagic agent that plays an integral role in the coagulation pathway. Vitamin K is involved in synthesis of coagulation factors; II, VII, IX and factor X. Vitamin K deficiency leads to bleeding diathesis. Hemorrhages usually present in deep soft tissue, rather than mucosal or epithelial membranes, bleeding that is generally caused by disorders of platelets. Major causes of vitamin K deficiency include; medications and diseases involving fat metabolism with a resultant fat malabsorption. Warfarin and Cephalosporins are one of the commonly prescribed medications that lead to vitamin K deficiency. Disease affecting fat metabolism pathway, such as; diseases of the pancreas (cystic fibrosis), short gut syndrome and certain pathologies of the biliary tree. Vitamin K deficiency is more common in newborns. In adults it is uncommon because of its ubiquitous nature and the abundance of its sources. Hemorrhagic disorders in adults due to Vitamin K deficiency are not commonly encountered in practice. We are presenting a case of an adult who presented with a compartment syndrome secondary to a traumatic intramuscular bleeding. Our case highlights the importance of considering vitamin K deficiency in the differential diagnosis of unexplained hemorrhages resulting from a coagulopathy.

Vitamins D and K as Factors Associated with Osteopathy in Chronic Pancreatitis: A Prospective Multicentre Study (P-BONE Study)

Background

Osteopathy is common in patients with chronic pancreatitis (CP), but previous studies carry several limitations. Vitamin K is essential for bone metabolism, but its role in this setting has never been investigated. Our aim is to assess the prevalence of osteoporosis and osteopenia in CP patients, and to investigate the association between osteopathy and CP features and nutritional parameters, especially vitamin D and K levels.

Methods

Multicentre cross-sectional study on CP patients diagnosed according to M-ANNHEIM criteria. Bone density was evaluated by dual-energy X-ray absorptiometry and pancreatic function by faecal elastase. Nutritional evaluation included vitamin D and vitamin K. Differences between patients with or without osteopathy were evaluated. The association between investigated variables and bone density were analysed with logistic regression analysis.

Results

In total, 211 CP patients were enrolled at eight Centres (67% men; mean age 60). In total, 18% had advanced-marked CP, 56% suffered from pancreatic exocrine insufficiency and disease aetiology was alcoholic in 43%. Vitamin D and K were deficient in 56% and 32%, respectively. Osteopenia was diagnosed in 42% and osteoporosis in 22%. In the multivariate analysis, female sex (OR 2.78), age (OR 1.07 per year) and higher BMI (OR 0.84) were associated with the presence of osteoporosis. In male patients, the only factor associated with osteoporosis was vitamin K deficiency (OR 4.23).

Conclusion

The present data confirm a high rate of osteopathy in CP patients and highlight the relevance of vitamin K deficiency as only factor associated with osteoporosis in male patients for the first time.

Development of a gut microbe-targeted nonlethal therapeutic to inhibit thrombosis potential

Trimethylamine N-oxide (TMAO) is a gut microbiota-derived metabolite that enhances both platelet responsiveness and in vivo thrombosis potential in animal models, and TMAO plasma levels predict incident atherothrombotic event risks in human clinical studies. TMAO is formed by gut microbe-dependent metabolism of trimethylamine (TMA) moiety-containing nutrients, which are abundant in a Western diet. Here, using a mechanism-based inhibitor approach targeting a major microbial TMA-generating enzyme pair, CutC and CutD (CutC/D), we developed inhibitors that are potent, time-dependent, and irreversible and that do not affect commensal viability. In animal models, a single oral dose of a CutC/D inhibitor significantly reduced plasma TMAO levels for up to 3 d and rescued diet-induced enhanced platelet responsiveness and thrombus formation, without observable toxicity or increased bleeding risk. The inhibitor selectively accumulated within intestinal microbes to millimolar levels, a concentration over 1-million-fold higher than needed for a therapeutic effect. These studies reveal that mechanism-based inhibition of gut microbial TMA and TMAO production reduces thrombosis potential, a critical adverse complication in heart disease. They also offer a generalizable approach for the selective nonlethal targeting of gut microbial enzymes linked to host disease limiting systemic exposure of the inhibitor in the host.

Should vitamin K be supplemented instead of antagonised in patients with idiopathic pulmonary fibrosis?

INTRODUCTION

There is an ongoing need for additional interventions in idiopathic pulmonary fibrosis (IPF) as antifibrotic drugs currently available only inhibit and do not stall disease progression. Vitamin K is a co-factor for the activation of coagulation factors. However, it is also required to activate proteins with functions outside of the coagulation cascade, such as matrix Gla protein (MGP), a defender against soft tissue calcification. Vitamin K antagonists are anticoagulants that are, for unknown reasons, associated with increased mortality in IPF. Areas covered: We advance the hypothesis that modulation of vitamin K-dependent MGP activation in IPF patients by either vitamin K antagonism or administration may result in acceleration and deceleration of fibrosis progression, respectively. Furthermore, shortfall in vitamin K could be suspected in IPF based on the high prevalence of certain co-morbidities, such as vascular calcification and lung cancer. Expert commentary: We hypothesize that vitamin K status is reduced in IPF patients. This, in combination with studies suggesting that vitamin K may play a role in lung fibrosis pathogenesis, would provide a rationale for conducting a clinical trial assessing the potential mitigating effects of vitamin K administration on progression of lung fibrosis, prevention of co-morbidities and mortality in IPF.

Determination of vitamins K1 , MK-4, and MK-7 in human serum of postmenopausal women by HPLC with fluorescence detection

BACKGROUND

New high-performance liquid chromatography (HPLC) method was developed for the determination of vitamin K₁ and two forms of vitamin K₂ (MK-4 and MK-7) in human serum, and the levels of vitamin K were determined in 350 samples of postmenopausal women.

METHODS

Vitamin K was determined by HPLC with fluorescence detection after postcolumn zinc reduction. The detection was performed at 246 nm (excitation) and 430 nm (emission). The internal standard and 2 mL of ethanol were added to 500 μL of serum. The mixture was extracted with 4 mL of hexane, and solid phase extraction was then used.

RESULTS

The HLPC method was fully validated. The intra- and interday accuracy and precision were evaluated on two QC samples by multiple analysis, and CV were less than 10%. The limit of quantification for MK-4 was found at 0.04 ng/mL, for K₁ 0.03 ng/mL, and for MK-7 0.03 ng/mL. The mean recoveries of the corresponding compounds were 98%-110%. Serum levels of MK-4, K₁ , and MK-7 in postmenopausal women with osteoporosis were 0.890 ± 0.291 ng/mL, 0.433 ± 0.394 ng/mL, and 1.002 ± 1.020 ng/mL, respectively (mean ± SD). Serum levels of MK-4, K₁ , and MK-7 in postmenopausal women without osteoporosis were 0.825 ± 0.266 ng/mL, 0.493 ± 0.399 ng/mL, and 1.186 ± 1.076 ng/mL, respectively (mean ± SD).

CONCLUSION

New HPLC method for the determination of vitamins K₁ , MK-4, and MK-7 in serum was evaluated and validated. This method is highly specific and sensitive with the low limit of quantification.

Prevalence and Effects of Functional Vitamin K Insufficiency: The PREVEND Study

Matrix Gla Protein (MGP) is a strong vitamin K-dependent inhibitor of soft tissue calcification. We assessed the prevalence of functional vitamin K insufficiency, as derived from plasma desphospho-uncarboxylated MGP (dp-ucMGP), and investigated whether plasma dp-ucMGP is associated with all-cause and cardiovascular mortality in a large general population-based cohort. We included 4275 subjects (aged 53 ± 12 years, 46.0% male) participating in the prospective general population-based Prevention of Renal and Vascular End-Stage Disease (PREVEND) study. The prevalence of functional vitamin K insufficiency (i.e., dp-ucMGP > 500 pmol/L) was 31% in the total study population. This prevalence was significantly higher among elderly and subjects with comorbidities like hypertension, type 2 diabetes, chronic kidney disease, and cardiovascular disease (~50%). After 10 years of follow-up, 279 subjects had died, with 74 deaths attributable to cardiovascular causes. We found significant J-shaped associations of plasma dp-ucMGP with all-cause (linear term: hazard ratio (HR) (95% confidence interval (CI)) = 0.20 (0.12-0.33), p < 0.001; squared term: 1.14 (1.10-1.17), p < 0.001) and cardiovascular mortality (linear term: 0.12 (0.05-0.27), p < 0.001; squared term: 1.17 (1.11-1.23), p < 0.001). These associations remained significant after adjustment for potential confounders. Whether the correction of vitamin K insufficiency improves health outcomes needs to be addressed in future prospective intervention studies.

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.