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

Vitamin K content of Australian-grown horticultural commodities

Vitamin K is a multi-function vitamin that has emerging roles in bone, brain and vascular health. Vitamin K composition data remain limited globally and Australia has lacked nationally representative data for vitamin K1 (phylloquinone) in horticultural commodities. Primary samples (n = 927) of 90 Australian-grown fruit, vegetable and nut commodities were purchased in three Australian cities. We measured vitamin K1/phylloquinone in duplicate in 95 composite samples using liquid chromatography with electrospray ionisation-tandem mass spectrometry. The greatest mean concentrations of vitamin K1/phylloquinone were found in kale (565 μg/100 g), baby spinach (255 μg/100 g) and Brussels sprouts (195 μg/100 g). The data contribute to the global collection of vitamin K food composition data. They add to the evidence that vitamin K1/phylloquinone concentrations vary markedly between geographic regions, supporting development of region-specific datasets for national food composition databases that do not yet contain data for vitamin K. Such data are needed globally.

Vitamin K: a potential missing link in critical illness-a scoping review

BACKGROUND

Vitamin K is essential for numerous physiological processes, including coagulation, bone metabolism, tissue calcification, and antioxidant activity. Deficiency, prevalent in critically ill ICU patients, impacts coagulation and increases the risk of bleeding and other complications. This review aims to elucidate the metabolism of vitamin K in the context of critical illness and identify a potential therapeutic approach.

METHODS

In December 2023, a scoping review was conducted using the PRISMA Extension for Scoping Reviews. Literature was searched in PubMed, Embase, and Cochrane databases without restrictions. Inclusion criteria were studies on adult ICU patients discussing vitamin K deficiency and/or supplementation.

RESULTS

A total of 1712 articles were screened, and 13 met the inclusion criteria. Vitamin K deficiency in ICU patients is linked to malnutrition, impaired absorption, antibiotic use, increased turnover, and genetic factors. Observational studies show higher PIVKA-II levels in ICU patients, indicating reduced vitamin K status. Risk factors include inadequate intake, disrupted absorption, and increased physiological demands. Supplementation studies suggest vitamin K can improve status but not normalize it completely. Vitamin K deficiency may correlate with prolonged ICU stays, mechanical ventilation, and increased mortality. Factors such as genetic polymorphisms and disrupted microbiomes also contribute to deficiency, underscoring the need for individualized nutritional strategies and further research on optimal supplementation dosages and administration routes.

CONCLUSIONS

Addressing vitamin K deficiency in ICU patients is crucial for mitigating risks associated with critical illness, yet optimal management strategies require further investigation.

IMPACT RESEARCH

To the best of our knowledge, this review is the first to address the prevalence and progression of vitamin K deficiency in critically ill patients. It guides clinicians in diagnosing and managing vitamin K deficiency in intensive care and suggests practical strategies for supplementing vitamin K in critically ill patients. This review provides a comprehensive overview of the existing literature, and serves as a valuable resource for clinicians, researchers, and policymakers in critical care medicine.

Vitamin K for Vascular Calcification in Kidney Patients: Still Alive and Kicking, but Still a Lot to Learn

Patients with chronic kidney disease (CKD) suffer disproportionately from a high burden of cardiovascular disease, which, despite recent scientific advances, remains partly understood. Vascular calcification (VC) is the result of an ongoing process of misplaced calcium in the inner and medial layers of the arteries, which has emerged as a critical contributor to cardiovascular events in CKD. Beyond its established role in blood clotting and bone health, vitamin K appears crucial in regulating VC via vitamin K-dependent proteins (VKDPs). Among these, the matrix Gla protein (MGP) serves as both a potent inhibitor of VC and a valuable biomarker (in its inactive form) for reflecting circulating vitamin K levels. CKD patients, especially in advanced stages, often present with vitamin K deficiency due to dietary restrictions, medications, and impaired intestinal absorption in the uremic environment. Epidemiological studies confirm a strong association between vitamin K levels, inactive MGP, and increased CVD risk across CKD stages. Based on the promising results of pre-clinical data, an increasing number of clinical trials have investigated the potential benefits of vitamin K supplementation to prevent, delay, or even reverse VC, but the results have remained inconsistent.

Vitamin K Status Based on K1, MK-4, MK-7, and Undercarboxylated Prothrombin Levels in Adolescent and Adult Patients with Cystic Fibrosis: A Cross-Sectional Study

The available evidence on vitamin K status in cystic fibrosis (CF) is scarce, lacking data on vitamin K2 (menaquinones-MK). Therefore, we assessed vitamin K1, MK-4 and MK-7 concentrations (LC-MS/MS) in 63 pancreatic insufficient and modulator naïve CF patients, and compared to 61 healthy subjects (HS). Vitamin K1 levels did not differ between studied groups. MK-4 concentrations were higher (median <1st-3rd quartile>: 0.778 <0.589-1.086> vs. 0.349 <0.256-0.469>, p < 0.0001) and MK-7 levels lower (0.150 <0.094-0.259> vs. 0.231 <0.191-0.315>, p = 0.0007) in CF patients than in HS. MK-7 concentrations were higher in CF patients receiving K1 and MK-7 supplementation than in those receiving vitamin K1 alone or no supplementation. Moreover, vitamin K1 concentrations depended on the supplementation regime. Based on multivariate logistic regression analysis, we have found that MK-7 supplementation dose has been the only predictive factor for MK-7 levels. In conclusion, vitamin K1 levels in CF are low if not currently supplemented. MK-4 concentrations in CF patients supplemented with large doses of vitamin K1 are higher than in HS. MK-7 levels in CF subjects not receiving MK-7 supplementation, with no regard to vitamin K1 supplementation, are low. There do not seem to be any good clinical predictive factors for vitamin K status.

Role of vitamin K2 in bone-vascular crosstalk

Vitamin K (VK) is a fat-soluble vitamin that is indispensable for the activation of vitamin K-dependent proteins (VKDPs). It has been shown to play an important role in the proper calcium deposit at the bone level, hindering that on the vascular walls. The deficiency of this vitamin in European populations is frequent and unknown. It is related to several factors, poor dietary intake, altered intestinal absorption or altered production by bacteria, indicating possible dysbiosis. For Vitamin K2 (VK2), there is currently no official reference daily intake (RDI). However, the effects of VK2 on the improvement of health in cardiovascular diseases, on bone metabolism, on chronic kidney diseases have been the subject of research in recent decades. The microbiota in the gastrointestinal tract plays an important role: Bacteroides are primarily capable of synthetizing very long chain forms of menaquinones and, in addition to the bacteria present in the intestinal flora, VK2 is also produced by bacteria used in food fermentation processes. This review provides an update on the current literature regarding the origin of VK2 and its implications in what is called the "calcium paradox", namely the lack of calcium in the bone and its storage in the wall of the vessel.

Exploring the complex relationship between vitamin K, gut microbiota, and warfarin variability in cardiac surgery patients

BACKGROUND AND OBJECTIVES

Due to the high individual variability of anticoagulant warfarin, this study aimed to investigate the effects of vitamin K concentration and gut microbiota on individual variability of warfarin in 246 cardiac surgery patients.

METHODS

The pharmacokinetics and pharmacodynamics (PKPD) model predicted international normalized ratio (INR) and warfarin concentration. Serum and fecal samples were collected to detect warfarin and vitamin K [VK1 and menaquinone-4 (MK4)] concentrations and gut microbiota diversity, respectively. In addition, the patient's medical records were reviewed for demographic characteristics, drug history, and CYP2C9, VKORC1, and CYP4F2 genotypes.

RESULTS

The PKPD model predicted ideal values of 62.7% for S-warfarin, 70.4% for R-warfarin, and 76.4% for INR. The normal VK1 level was 1.34±1.12 nmol/ml (95% CI: 0.33-4.08 nmol/ml), and the normal MK4 level was 0.22±0.18 nmol/ml (95% CI: 0.07-0.63 nmol/ml). The MK4 to total vitamin K ratio was 16.5±9.8% (95% CI: 4.3-41.5%). The S-warfarin concentration of producing 50% of maximum anticoagulation and the half-life of prothrombin complex activity tended to increase with vitamin K. Further, Prevotella and Eubacterium of gut microbiota identified as the main bacteria associated with individual variability of warfarin. The results suggest that an increase in vitamin K concentration can decrease anticoagulation, and gut microbiota may influence warfarin anticoagulation through vitamin K2 synthesis.

CONCLUSION

This study highlights the importance of considering vitamin K concentration and gut microbiota when prescribing warfarin. The findings may have significant implications for the personalized use of warfarin. Further research is needed to understand better the role of vitamin K and gut microbiota in warfarin anticoagulation.

The effect of vitamin K4 supplementation on insulin resistance in individuals with type 2 diabetes: a double-blind randomised placebo-controlled clinical trial

PURPOSE

The purpose of this study was to assess the possible clinical effects of vitamin K4 supplementation in individuals with type 2 diabetes namely insulin resistance, glycaemic control, and lipid profile.

METHODS

This was a prospective randomised double-blind placebo-controlled clinical trial. A total of 106 patients were randomised to receive either 1 mg of vitamin K4 (menadiol diacetate) or placebo for 24 weeks.

RESULTS

Ninety patients (n = 45 in each study group) were included in the final analysis. After 24 weeks, homeostatic model assessment of insulin resistance (HOMA-IR) (16.54 ± 7.81 vs. 29.09 ± 36.56, P = 0.027) and fasting serum insulin (FSI) (6.86 ± 3.45 vs. 11.13 ± 12.66 µU/ml, P = 0.032) were significantly lower in the vitamin K group compared to placebo. Additionally, triglycerides (TG) (144.94 ± 50.7 vs. 172.8 ± 101.5 mg/dl, P = 0.031) and very low-density lipoproteins (VLDL) levels (28.9 ± 9.88 vs. 34.6 ± 20.30 mg/dl, P = 0.027) decreased significantly in the vitamin K group after 24 weeks compared to baseline. Moreover, more patients in the vitamin K group (35.6%) had their antidiabetic medication doses reduced after 24 weeks compared to placebo (13.3%, P = 0.029).

CONCLUSION

Vitamin K4 supplementation for 24 weeks is capable of improving insulin resistance and TG levels in individuals with type 2 diabetes. In addition, the improvement in insulin resistance was reflected in the decrease in antidiabetic medication doses. However, it did not affect fasting plasma glucose (FPG) or glycated haemoglobin (HbA1c).

TRIAL REGISTRATION

The study was registered on clinicaltrials.gov with ID: NCT04285450.

Protein induced by vitamin K absence or antagonist II: Experience to date and future directions

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer with high mortality. The realization of precision medicine in HCC relies upon efficient biomarkers. Protein induced by vitamin K absence or antagonist II (PIVKA-II) is an immature prothrombin with insufficient coagulation activity, overexpressing in HCC cells. Previous evidence confirmed the role of PIVKA-II in screening and diagnosing HCC. However, the increased PIVKA-II was observed not only in HCC, but also in non-HCC individuals such as vitamin K deficiency. The joint detection of PIVKA-II and other biomarkers could significantly improve diagnostic accuracy in HCC. Furthermore, PIVKA-II serves as a valuable prognostic predictor, transplantation eligibility, resectability, tumor recurrence, therapeutic efficacy, and malignant tumor behaviors. Additionally, PIVKA-II represents a potential target for agent development to establish new therapeutic strategies. Besides HCC, PIVKA-II also serves as a biomarker of vitamin K status. In this review, we assess the role of PIVKA-II in diagnosis, prediction, and treatment. Over the past decades, substantial progress has been achieved in the application of PIVKA-II. Exploration and innovation are required for further advances in the field of PIVKA-II investigation.

The Effect of Vitamin K2 Supplementation on PIVKA-II Levels in Patients with Severe Motor and Intellectual Disabilities Undergoing Long-Term Tube Feeding

Nutritional support is essential for patients with severe motor and intellectual disabilities (SMID) to ensure the smooth provision of medical care. These patients often require long-term tube feeding with enteral formulas, potentially leading to deficiencies in vitamins and trace elements. Additionally, frequent antibiotic use for infections often disrupts gut microbiota, inhibiting vitamin K2 production by intestinal bacteria. We assessed the serum protein induced by vitamin K absence or antagonists-II (PIVKA-II) and undercarboxylated osteocalcin (ucOC) levels to assess the vitamin K status in 20 patients with SMID (median age: 44.1 years, 11 men and 9 women) undergoing long-term tube feeding for durations ranging from 3 to 31 years. Thirteen (65%) and nine (45%) patients had elevated PIVKA-II (<40 mAU/mL) and serum ucOC levels (reference value < 4.50 ng/mL), respectively. Dietary vitamin K1 intake did not differ between patients with and without elevated PIVKA-II levels. Vitamin K2 supplementation for 3 months decreased serum PIVKA-II levels near those within the reference range. Approximately half of the patients with SMID on tube feeding had subclinical vitamin K deficiency. Further studies are needed to ascertain if long-term vitamin K2 supplementation effectively prevents vitamin K deficiency-induced hypercoagulation, osteoporosis, and vascular calcification in patients with SMID.

Vitamin K - a scoping review for Nordic Nutrition Recommendations 2023

Vitamin K occurs in dietary supply in two major forms: phylloquinone (vitamin K1) and menaquinones (collectively referred as vitamin K2). Phylloquinone is derived from plants. There are at least 10 forms of menaquinones varying in chain length and they are produced by bacteria except menaquinone-4. Menaquinone-4 is formed from phylloquinone or other menaquinone forms. Phylloquinone is considered to be the major contributor and menaquinones are thought to contribute less to vitamin K intake in Western diets. However, less is known about the content of menaquinones than phylloquinones in foods. Vitamin K is known to function as an enzymatic cofactor in the gamma-carboxylation of vitamin K dependent proteins (VKDPs). Hepatic VKDPs are involved in coagulation. Extrahepatic VKDPs have a role e.g. in bone health and vascular calcification. However, the amount of vitamin K needed for optimal functioning of the different VKDPs is not known.

Vitamin K1 Intake and Incident Diabetes in the Danish Diet, Cancer, and Health Study

CONTEXT

Observational studies have reported lower risks of type 2 diabetes with higher vitamin K1 intake, but these studies overlook effect modification due to known diabetes risk factors.

OBJECTIVE

To identify subgroups that might benefit from vitamin K1 intake, we examined associations between vitamin K1 intake and incident diabetes overall and in subpopulations at risk of diabetes.

METHODS

Participants from the prospective cohort, the Danish Diet, Cancer, and Health Study, with no history of diabetes were followed up for diabetes incidence. The association between intake of vitamin K1, estimated from a food frequency questionnaire completed at baseline, and incident diabetes was determined using multivariable-adjusted Cox proportional-hazards models.

RESULTS

In 54 787 Danish residents with a median (interquartile range) age of 56 (52-60) years at baseline, 6700 individuals were diagnosed with diabetes during 20.8 (17.3-21.6) years of follow-up. Vitamin K1 intake was inversely and linearly associated with incident diabetes (P < .0001). Compared to participants with the lowest vitamin K1 intake (median:57 µg/d), participants with the highest intakes (median:191 µg/d) had a 31% lower risk of diabetes (HR; 95% CI, 0.69; 0.64-0.74) after multivariable adjustments. The inverse association between vitamin K1 intake and incident diabetes was present in all subgroups (namely, men and women, ever and never smokers, low and high physical activity groups, and in participants who were normal to overweight and obese), with differences in absolute risk between subgroups.

CONCLUSION

Higher intake of foods rich in vitamin K1 was associated with a lower risk of diabetes. If the associations observed are causal, our results indicate that more cases of diabetes would be prevented in subgroups at higher risk (men, smokers, participants with obesity, and those with low physical activity).

The association of vitamin K status with lung function and disease in a general population

Introduction

Matrix Gla protein (MGP) is an inhibitor of lung tissue calcification. The plasma level of dephosphorylated-uncarboxylated MGP (dp-ucMGP) is a biomarker of vitamin K status. The present study assessed whether lower vitamin K status (reflected by higher dp-ucMGP) was associated with lung function and lung disease/symptoms.

Methods

A general population sample of 4092 individuals, aged 24 to 77 years, underwent a health examination including questionnaires, spirometry and measurements of plasma dp-ucMGP. Associations of dp-ucMGP with lung function and self-reported disease/symptoms were estimated using regression models adjusted for age, sex and height. Associations were expressed as β-estimates or odds ratios (ORs) per doubling in dp-ucMGP.

Results

Lower vitamin K status (higher dp-ucMGP) was associated with lower forced expiratory volume in 1 s (FEV1) (98 mL; 95% CI: 54-141 mL) and lower forced vital capacity (FVC) (136 mL; 95% CI: 85-187 mL). Dp-ucMGP was not associated with the FEV1/FVC ratio (0.0 percentage points higher than the expected value; 95% CI: -1.0-1.0). Furthermore, lower vitamin K status was associated with COPD (OR 2.24, 95% CI: 1.53-3.27), wheezing (OR 1.81, 95% CI: 1.44-2.28) and asthma (OR 1.44, 95% CI: 1.12-1.83).

Conclusion

Lower vitamin K status was associated with lower ventilatory capacity (lower FEV1 and FVC), and with higher risk of self-reported asthma, COPD and wheezing. Vitamin K status was not associated with airflow obstruction (FEV1/FVC ratio).

The Association Between Lipid Profile and Subfoveal Choroidal Thickness in Chinese Patients with Proliferative Diabetic Retinopathy Secondary to Type 2 Diabetes

Introduction

Extensive studies have studied the factors associated with subfoveal choroidal thickness (SFCT). However, studies of the association between lipid profile and SFCT in patients with proliferative diabetic retinopathy (PDR) in type 2 diabetes remain limited. Thus, we aimed to investigate the relationship between lipid profile and SFCT in patients with PDR.

Materials and Methods

This was a retrospective cross-sectional study. The included participants were inpatients who underwent vitrectomy for PDR with type 2 diabetes and contralateral eyes of PDR patients meeting the criteria. Multivariate linear regression analysis was used to determine the independent association between lipid profile and SFCT.

Results

A total of 131 participants with PDR were enrolled in the final analysis. The average age of the participants was 55.76 ± 9.88 years, and the average SFCT was 276.10 ± 92.92 μm. Multivariate linear regression model results showed that in the fully adjusted model, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) had a negative association with SFCT (β = -16.51, 95% CI: -29.57, -3.46; P = 0.0148; β = -42.65, 95% CI: -82.60, -2.70; P = 0.0390; β = -17.89, 95% CI: -33.24, -2.54; P = 0.0245, respectively), while triglyceride was not significantly associated with SFCT (β = 5.23, 95% CI: -18.57, 29.02; P = 0.6678). Furthermore, the results of stratified analysis showed that except for triglyceride, the trends of total cholesterol, HDL-C, LDL-C, and SFCT were consistent among different stratifications in participants.

Conclusion

The cholesterol profile had a significant negative association with SFCT in Chinese PDR patients, but triglyceride was not significantly associated with SFCT. This suggests that these systemic imbalances contribute to choroidal changes, and often coexist in diabetic patients.

Liquid chromatography-tandem mass spectrometry in fat-soluble vitamin deficiency

Fat-soluble vitamins, including vitamins A, D, E, and K, are essential for maintaining normal body function and metabolism. Fat-soluble vitamin deficiency may lead to bone diseases, anemia, bleeding, xerophthalmia, etc. Early detection and timely interventions are significant for preventing vitamin deficiency-related diseases. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is developing into a potent instrument for the precise detection of fat-soluble vitamins due to its high sensitivity, high specificity, and high resolution.

Effects of Menaquinone-7 on the Bone Health of Growing Rats under Calcium Restriction: New Insights from Microbiome-Metabolomics

Insufficient calcium intake during growth is a global public health concern. The aim of this study was to investigate the effects of dietary menaquinone-7 (MK-7) on bone accrual in growing Sprague-Dawley rats under calcium restriction. Following 13 weeks of treatment, various bone quality parameters, including microarchitecture, were measured. Fecal and cecal samples were subjected to microbiome (16S rRNA gene sequencing) analyses, while metabolomics analysis of the cecum and humerus samples was analyzed based on UHPLC-Q/TOF-MS. We found that calcium deficiency diminished the richness of the microbiome and disrupted microbiome composition, accompanied by an elevation in the relative abundance of Parasutterella. Furthermore, calcium insufficiency escalated the level of isovaleric acid and modified the metabolic profiles. MK-7 supplementation significantly increased the cortical thickness, cortical bone area, and the calcium content of the femur. Apart from improving bone calcium deposition and diminishing bone resorption, the mechanisms underlying the beneficial effects of MK on bone quality also involve the modulation of the host's metabolic pathways and the composition of gut microbiota. The gut-bone axis holds promise as an efficacious target for ameliorating calcium deficiency in children's bone quality, and MK-7 is a promising dietary supplement from this perspective.

Lack of Consensus Between Measurements of Plasma Phylloquinone by Enzyme-Linked Immunosorbent assays and a Well-Validated High-Performance Liquid Chromatographic Method

Enzyme-linked i2mmunosorbent assays (ELISAs) that measure circulating phylloquinone have become commercially available, but their validity is uncertain. The objective of this study was to compare plasma phylloquinone concentrations measured using two commercially available ELISAs with concentrations measured using a validated high-performance liquid chromatography (HPLC) assay in 108 samples obtained from participants in a depletion (∼10 mcg phylloquinone/d)-supplementation (∼500 mcg phylloquinone/d) study. The geometric mean of plasma phylloquinone measured with ELISA A was 0.70 nmol/L, 37% lower than that measured with HPLC. The mean of the ELISA B measures was 12.4 nmol/L, >700% higher than the HPLC measures. Plasma phylloquinone measured using HPLC was significantly lower during phylloquinone depletion than supplementation (0.4 ± 0.1 compared with 1.2 ± 0.2 nmol/L; P < 0.001). Neither of the two ELISAs detected any significant difference in plasma phylloquinone concentrations between depletion and supplementation (ELISA A, P = 0.76; ELISA B, P = 0.29). These findings reinforce the need to validate plasma phylloquinone assays as they become available. Curr Dev Nutr 2023;x:xx.

Effect of Menaquinone-7 Supplementation on Arterial Stiffness in Chronic Hemodialysis Patients: A Multicenter Randomized Controlled Trial

BACKGROUND

There is a very high prevalence of subclinical vitamin K deficiency in patients requiring hemodialysis (HD), and this problem is associated with vascular calcification and arterial stiffness. Vitamin K2 (MK-7) supplementation can improve vitamin K status in HD patients. However, the benefits of vitamin K supplementation on arterial stiffness have still not been established. The present study was conducted to evaluate the efficacy of menaquinone-7 (MK-7) supplementation on arterial stiffness in chronic HD patients.

METHODS

This open-label multicenter randomized clinical trial was conducted in 96 HD patients who had arterial stiffness, defined by high carotid femoral pulse wave velocity (cfPWV ≥ 10 m/s). The patients were randomly assigned to receive oral MK-7 (375 mcg once daily) for 24 weeks (n = 50) or standard care (control group; n = 46). The change in cfPWV was the primary outcome.

RESULTS

Baseline parameters were comparable between the two groups. There was no significant difference in the change in cPWV at 24 weeks between the MK-7 group and standard care [-6.0% (-20.2, 2.3) vs. -6.8% (-19.0, 7.3), p = 0.24]. However, we found that MK-7 significantly decreased cPWV in patients with diabetes [-10.0% (-15.9, -0.8) vs. 3.8% (-5.8, 11.6), p = 0.008]. In addition, the MK-7 group had a lower rate of arterial stiffness progression, compared to controls (30.2% vs. 39.5%, p = 0.37), especially in diabetes patients (21.4% vs. 72.7%, p = 0.01). No serious adverse events were observed during the 24 weeks.

CONCLUSION

Vitamin K supplements provided a beneficial impact in lowering the rate of arterial stiffness progression in chronic hemodialysis patients with diabetes. Possible benefits on cardiovascular outcomes require further investigation.

Vitamin K and the Visual System-A Narrative Review

Vitamin K occupies a unique and often obscured place among its fellow fat-soluble vitamins. Evidence is mounting, however, that vitamin K (VK) may play an important role in the visual system apart from the hepatic carboxylation of hemostatic-related proteins. However, to our knowledge, no review covering the topic has appeared in the medical literature. Recent studies have confirmed that matrix Gla protein (MGP), a vitamin K-dependent protein (VKDP), is essential for the regulation of intraocular pressure in mice. The PREDIMED (Prevención con Dieta Mediterránea) study, a randomized trial involving 5860 adults at risk for cardiovascular disease, demonstrated a 29% reduction in the risk of cataract surgery in participants with the highest tertile of dietary vitamin K1 (PK) intake compared with those with the lowest tertile. However, the specific requirements of the eye and visual system (EVS) for VK, and what might constitute an optimized VK status, is currently unknown and largely unexplored. It is, therefore, the intention of this narrative review to provide an introduction concerning VK and the visual system, review ocular VK biology, and provide some historical context for recent discoveries. Potential opportunities and gaps in current research efforts will be touched upon in the hope of raising awareness and encouraging continued VK-related investigations in this important and highly specialized sensory system.

The Pleiotropic Role of Vitamin K in Multimorbidity of Chronic Obstructive Pulmonary Disease

Although defined by the presence of airflow obstruction and respiratory symptoms, patients with chronic obstructive pulmonary disease (COPD) are characterized by multimorbidity. Numerous co-occurring conditions and systemic manifestations contribute to the clinical presentation and progression of COPD; however, underlying mechanisms for multimorbidity are currently not fully elucidated. Vitamin A and vitamin D have been related to COPD pathogenesis. Another fat-soluble vitamin, vitamin K, has been put forward to exert protective roles in COPD. Vitamin K is an unequivocal cofactor for the carboxylation of coagulation factors, but also for extra-hepatic proteins including the soft tissue calcification inhibitor matrix Gla-protein and the bone protein osteocalcin. Additionally, vitamin K has been shown to have anti-oxidant and anti-ferroptosis properties. In this review, we discuss the potential role of vitamin K in the systemic manifestations of COPD. We will elaborate on the effect of vitamin K on prevalent co-occurring chronic conditions in COPD including cardiovascular disorders, chronic kidney disease, osteoporosis, and sarcopenia. Finally, we link these conditions to COPD with vitamin K as a connecting factor and provide recommendations for future clinical studies.

Association of Vitamin K Status with Arterial Calcification and Stiffness in Chronic Kidney Disease: The Chronic Renal Insufficiency Cohort

Background

Arterial calcification and stiffness are common in people with chronic kidney disease (CKD). Higher vitamin K status has been associated with less arterial calcification and stiffness in CKD in cross-sectional studies.

Objectives

To determine the association of vitamin K status with coronary artery calcium (CAC) and arterial stiffness [pulse wave velocity (PWV)] at baseline and over 2-4 follow-up years in adults with mild-to-moderate CKD.

Methods

Participants (n = 2722) were drawn from the well-characterized Chronic Renal Insufficiency Cohort. Two vitamin K status biomarkers, plasma phylloquinone and plasma dephospho-uncarboxylated matrix gla protein [(dp)ucMGP], were measured at baseline. CAC and PWV were measured at baseline and over 2-4 y of follow-up. Differences across vitamin K status categories in CAC prevalence, incidence, and progression (defined as ≥100 Agatston units/y increase) and PWV at baseline and over follow-up were evaluated using multivariable-adjusted generalized linear models.

Results

CAC prevalence, incidence, and progression did not differ across plasma phylloquinone categories. Moreover, CAC prevalence and incidence did not differ according to plasma (dp)ucMGP concentration. Compared with participants with the highest (dp)ucMGP (≥450 pmol/L), those in the middle category (300-449 pmol/L) had a 49% lower rate of CAC progression (incidence rate ratio: 0.51; 95% CI: 0.33, 0.78). However, CAC progression did not differ between those with the lowest (<300 pmol/L) and those with the highest plasma (dp)ucMGP concentration (incidence rate ratio: 0.82; 95% CI: 0.56, 1.19). Neither vitamin K status biomarker was associated with PWV at baseline or longitudinally.

Conclusions

Vitamin K status was not consistently associated with CAC or PWV in adults with mild-to-moderate CKD.

Exclusively breastmilk-fed preterm infants are at high risk of developing subclinical vitamin K deficiency despite intramuscular prophylaxis at birth

BACKGROUND

There is near-global consensus that all newborns be given parenteral vitamin K1 (VK1 ) at birth as prophylaxis against VK deficiency bleeding (VKDB). Breastmilk has a low VK content and cases of late VKDB are reported in exclusively breastmilk-fed preterm infants despite VK prophylaxis at birth.

OBJECTIVES

To assess the prevalence of functional VK insufficiency in preterm infants based on elevated under-γ-carboxylated (Glu) species of Gla proteins, factor II (PIVKA-II), and osteocalcin (GluOC), synthesized by liver and bone, respectively.

PATIENTS/METHODS

Prospective, multicenter, observational study in preterm infants born <33 weeks' gestation. Blood samples and dietary history were collected before hospital discharge, and after discharge at 2-3 months' corrected age. Outcome measures were serum VK1 , PIVKA-II, and %GluOC (GluOC as a percentage of the sum of GluOC plus GlaOC) compared between exclusively breastmilk-fed and formula/mixed-fed infants after discharge.

RESULTS

After discharge, breastmilk-fed babies had significantly lower serum VK1 (0.15 vs. 1.81 μg/L), higher PIVKA-II (0.10 vs. 0.02 AU/ml) and higher %GluOC (63.6% vs. 8.1%) than those receiving a formula/mixed-feed diet. Pre-discharge (based on elevated PIVKA-II), only one (2%) of 45 breastmilk-fed infants was VK insufficient. After discharge, eight (67%) of 12 exclusively breastmilk-fed babies were VK insufficient versus only one (4%) of 25 formula/mixed-fed babies.

CONCLUSIONS

Preterm infants who remain exclusively or predominantly human breastmilk-fed after neonatal unit discharge are at high risk of developing subclinical VK deficiency in early infancy. Routine postdischarge VK1 supplementation of breastfed infants to provide intakes comparable to those from formula milks should prevent this deficiency.

Molecular mechanisms and therapeutic effects of different vitamins and minerals in COVID-19 patients

COVID-19 is a rapidly spreading disease, which has caught the world by surprise. Millions of people suffer from illness, and the mortality rates are dramatically high. Currently, there is no specific and immediate treatment for this disease. Remedies are limited to supportive regiments and few antiviral and anti-inflammatory drugs. The lack of a definite cure for COVID-19 is the reason behind its high mortality and global prevalence. COVID-19 can lead to a critical illness with severe respiratory distress and cytokine release. Increased oxidative stress and excessive production of inflammatory cytokines are vital components of severe COVID-19. Micronutrients, metalloids, and vitamins such as iron, manganese, selenium, Zinc, Copper, vitamin A, B family, and C are among the essential and trace elements that play a pivotal role in human nutrition and health. They participate in metabolic processes that lead to energy production. In addition, they support immune functions and act as antioxidants. Therefore, maintaining an optimal level of micronutrients intake, particularly those with antioxidant activities, is essential to fight against oxidative stress, modulate inflammation, and boost the immune system. Therefore, these factors could play a crucial role in COVID-19 prevention and treatment. In this review, we aimed to summarize antiviral properties of different vitamins and minerals. Moreover, we will investigate the correlation between them and their effects in COVID-19 patients.

Vitamin K content of cheese, yoghurt and meat products in Australia

Vitamin K is vital for normal blood coagulation, and may influence bone, neurological and vascular health. Data on the vitamin K content of Australian foods are limited, preventing estimation of vitamin K intakes in the Australian population. We measured phylloquinone (PK) and menaquinone (MK) -4 to -10 in cheese, yoghurt and meat products (48 composite samples from 288 primary samples) by liquid chromatography with electrospray ionisation-tandem mass spectrometry. At least one K vitamer was found in every sample. The greatest mean (± standard deviation for foods sampled in multiple cities) concentrations of PK (4.9 µg/100 g), MK-4 (58 ± 9 µg/100 g) and MK-9 (8 ± 2 µg/100 g) were found in lamb liver, chicken leg meat and Cheddar cheese, respectively. Cheddar cheese (1.1 ± 0.3 µg/100 g) and cream cheese (1.0 µg/100 g) contained MK-5. MK-8 was found in Cheddar cheese only (4 ± 2 µg/100 g). As the K vitamer profile and concentrations appear to vary considerably by geographical location, Australia needs a vitamin K food composition dataset that is representative of foods consumed in Australia.

Urinary matrix Gla protein is associated with mortality risk in Flemish population: A prospective study

Background

Vascular calcification is strongly related to the risk of mortality and cardiovascular (CV) diseases. In vascular calcification, matrix Gla protein (MGP), a small vitamin K-dependent protein, is an important mineralization inhibitor. Recent studies showed that circulating MGP is associated with mortality risk. However, the longitudinal association between urinary excretion of MGP and all-cause mortality was not established.

Materials and methods

Urinary MGP was measured in 776 randomly recruited Flemish population (mean age: 51.2 years; 50.9% women) at baseline (during 2005–2010) using capillary electrophoresis coupled with mass spectrometry. Plasma inactive MGP [desphospho-uncarboxylated MGP (dp-ucMGP)] levels were quantified in 646 individuals by ELISA kits. Mortality status was ascertained through the Belgian Population Registry until 2016. The longitudinal association with mortality was determined by the multivariate-adjusted Cox proportional hazards regression models. The multivariate linear regression models were used to identify determinants of urinary MGP level.

Results

Over the 9.2 years, 47 (6.06%) participants died, including 15 CV deaths. For a doubling of urinary MGP, the hazard ratios (HRs) were 1.31 (95% CI: 1.01–1.69, P = 0.040) for all-cause mortality and 2.05 (95% CI: 1.11–3.79, P = 0.023) for CV mortality with adjustment for covariates, including estimated glomerular filtration rate and urine microalbumin. The addition of urinary MGP to the basic models improved the reclassification as suggested by the increased net reclassification improvement [64.01% (95% CI: 32.64–98.63)] and integrated discrimination improvement [2.33% (95% CI: 0.24–4.71)]. Circulating inactive MGP, total cholesterol, urine microalbumin, and smoking were significantly associated with urinary MGP levels (P ≤ 0.041), independent of sex and age.

Conclusion

Elevated urinary MGP was associated with an increased risk of all-cause mortality and CV mortality and improved the risk reclassification for all-cause mortality. These findings suggested that urinary MGP might be useful in mortality risk assessment in the general population. However, these observations need to be replicated in larger studies with a longer follow-up time.

Optimisation of the fermentation media to enhance the production of the bioactive isomer of vitamin menaquinone-7

Menaquinone-7 (MK-7) offers significant health benefits; however, only the all-trans form is biologically active. MK-7 produced through fermentation can occur as all-trans and cis isomers, and the therapeutic value of the resulting MK-7 is exclusively determined by the quantity of the all-trans isomer. Therefore, this study aimed to investigate the effect of the media composition on the isomer profile obtained from fermentation and determine the optimum media combination to increase the concentration of the all-trans isomer and diminish the production of cis MK-7. For this purpose, design of experiments (DOE) was used to screen the most effective nutrients, and a central composite face-centred design (CCF) was employed to optimise the media components. The optimum media consisted of 1% (w/v) glucose, 2% (w/v) yeast extract, 2% (w/v) soy peptone, 2% (w/v) tryptone, and 0.1% (w/v) CaCl₂. This composition resulted in an average all-trans and cis isomer concentration of 36.366 mg/L and 1.225 mg/L, respectively. In addition, the optimised media enabled an all-trans isomer concentration 12.2-fold greater and a cis isomer concentration 2.9-fold less than the unoptimised media. This study was the first to consider the development of an optimised fermentation media to enhance the production of the bioactive isomer of MK-7 and minimise the concentration of the inactive isomer. Furthermore, this media is commercially promising, as it will improve the process productivity and reduce the costs associated with the industrial fermentation of the vitamin.

Molecular Pathways and Roles for Vitamin K2-7 as a Health-Beneficial Nutraceutical: Challenges and Opportunities

Vitamin K2-7, also known as menaquinone-7 (MK-7) is a form of vitamin K that has health-beneficial effects in osteoporosis, cardiovascular disease, inflammation, cancer, Alzheimer’s disease, diabetes and peripheral neuropathy. Compared to vitamin K1 (phylloquinone), K2-7 is absorbed more readily and is more bioavailable. Clinical studies have unequivocally demonstrated the utility of vitamin K2-7 supplementation in ameliorating peripheral neuropathy, reducing bone fracture risk and improving cardiovascular health. We examine how undercarboxylated osteocalcin (ucOC) and matrix Gla protein (ucMGP) are converted to carboxylated forms (cOC and cMGP respectively) by K2-7 acting as a cofactor, thus facilitating the deposition of calcium in bones and preventing vascular calcification. K2-7 is beneficial in managing bone loss because it upregulates osteoprotegerin which is a decoy receptor for RANK ligand (RANKL) thus inhibiting bone resorption. We also review the evidence for the health-beneficial outcomes of K2-7 in diabetes, peripheral neuropathy and Alzheimer’s disease. In addition, we discuss the K2-7-mediated suppression of growth in cancer cells via cell-cycle arrest, autophagy and apoptosis. The mechanistic basis for the disease-modulating effects of K2-7 is mediated through various signal transduction pathways such as PI3K/AKT, MAP Kinase, JAK/STAT, NF-κB, etc. Interestingly, K2-7 is also responsible for suppression of proinflammatory mediators such as IL-1α, IL-1β and TNF-α. We elucidate various genes modulated by K2-7 as well as the clinical pharmacometrics of vitamin K2-7 including K2-7-mediated pharmacokinetics/pharmacodynamics (PK/PD). Further, we discuss the current status of clinical trials on K2-7 that shed light on dosing strategies for maximum health benefits. Taken together, this is a synthetic review that delineates the health-beneficial effects of K2-7 in a clinical setting, highlights the molecular basis for these effects, elucidates the clinical pharmacokinetics of K2-7, and underscores the need for K2-7 supplementation in the global diet.

Vitamin K-Dependent Protein Activation: Normal Gamma-Glutamyl Carboxylation and Disruption in Disease

Vitamin K-dependent (VKD) proteins undergo an unusual post-translational modification, which is the conversion of specific Glu residues to carboxylated Glu (Gla). Gla generation is required for the activation of VKD proteins, and occurs in the endoplasmic reticulum during their secretion to either the cell surface or from the cell. The gamma-glutamyl carboxylase produces Gla using reduced vitamin K, which becomes oxygenated to vitamin K epoxide. Reduced vitamin K is then regenerated by a vitamin K oxidoreductase (VKORC1), and this interconversion of oxygenated and reduced vitamin K is referred to as the vitamin K cycle. Many of the VKD proteins support hemostasis, which is suppressed during therapy with warfarin that inhibits VKORC1 activity. VKD proteins also impact a broad range of physiologies beyond hemostasis, which includes regulation of calcification, apoptosis, complement, growth control, signal transduction and angiogenesis. The review covers the roles of VKD proteins, how they become activated, and how disruption of carboxylation can lead to disease. VKD proteins contain clusters of Gla residues that form a calcium-binding module important for activity, and carboxylase processivity allows the generation of multiple Glas. The review discusses how impaired carboxylase processivity results in the pseudoxanthoma elasticum-like disease.

A review of recent evidence of dietary protein intake and health

The Korea National Health and Nutrition Examination Survey of 2013 to 2017 reported that the average protein consumption of the Korean population is above the current recommended nutrient intake of protein proposed by the Dietary Reference Intakes for Koreans. Some health professionals and the media often advise consuming diets high in protein for promoting metabolic regulation, weight control, and muscle synthesis. However, due to lack of scientific evidence, the validity and safety of high protein consumption are yet to be fully ascertained. The present review assesses recent evidence published in 2014-2020 from human studies, focusing on adequate protein intake and protein sources for the prevention of chronic diseases, particularly metabolic disorders and sarcopenia.

The Relationship Among Intestinal Bacteria, Vitamin K and Response of Vitamin K Antagonist: A Review of Evidence and Potential Mechanism

The vitamin K antagonist is a commonly prescribed effective oral anticoagulant with a narrow therapeutic range, and the dose requirements for different patients varied greatly. In recent years, studies on human intestinal microbiome have provided many valuable insights into disease development and drug reactions. A lot of studies indicated the potential relationship between microbiome and the vitamin K antagonist. Vitamin K is absorbed by the gut, and the intestinal bacteria are a major source of vitamin K in human body. A combined use of the vitamin K antagonist and antibiotics may result in an increase in INR, thus elevating the risk of bleeding, while vitamin K supplementation can improve stability of anticoagulation for oral vitamin K antagonist treatment. Recently, how intestinal bacteria affect the response of the vitamin K antagonist remains unclear. In this review, we reviewed the research, focusing on the physiology of vitamin K in the anticoagulation treatment, and investigated the potential pathways of intestinal bacteria affecting the reaction of the vitamin K antagonist.

Inflammation-mediated vitamin K and vitamin D effects on vascular calcifications in people with HIV on active antiretroviral therapy

BACKGROUND

People with HIV (PWH) experience increased systemic inflammation and monocyte activation, leading to increased risk of cardiovascular events (death, stroke, and myocardial infarction) and higher coronary artery calcium scores (CACs). Vitamins D and K2 have significant anti-inflammatory effects; in addition, vitamin K2 is involved in preventing vascular calcifications in the general population. The roles of vitamins D and K in increased coronary calcifications in successfully treated PWH is less understood.

METHODS

We prospectively recruited 237 PWH on antiretroviral treatment (ART) and 67 healthy controls. CACs were derived from noncontrast chest computed tomography (CT) and levels of 25-hydroxyvitamin D (vitamin D) and inactive vitamin K-dependent dephosphorylated-uncarboxylated matrix Gla protein (dp-uc MGP, marker of vitamin K deficiency) were measured in plasma during a fasting state. The relationship between inflammation markers, dp-uc MGP, and vitamin D on CACs were estimated using zero-inflated negative binomial regression. Adjusted models included 25(OH)D, MGP, sex, race, age, and markers of inflammation or monocyte activation.

RESULTS

Overall, controls had lower median age (45.8 vs. 48.8; P = 0.03), a larger proportion of female individuals (55.2 vs. 23.6%; P < 0.0001), and nonwhite (33.8 vs. 70%; P < 0.0001). Among PWH, less than 1% had detectable viral load and the median CD4+ cell count was 682 (IQR: 473.00-899.00). 62.17% of the participants had zero CACs and 51.32% were vitamin D-deficient (<20 ng/ml). There was no difference in detectable CACs (P = 0.19) or dp-uc MGP (P = 0.42) between PWH and controls. In adjusted models, PWH with nonzero CACs have three times greater expected CAC burden compared with controls. Every 1% increase in MGP (worse K status) decreases the probability of having CACs equal to zero by 21.33% (P = 0.01). Evidence suggests that the effects of 25(OH)D and MGP are inflammation-mediated, specifically through sVCAM, TNF-αRI, and TNF-αRII.

CONCLUSION

Vitamin K deficiency is a modifiable preventive factor against coronary calcification in PWH. Further research should determine whether vitamin K supplementation would reduce systemic inflammation, vascular calcification, and risk of cardiovascular events in PWH.

Multiple Dietary Vitamin K Forms Are Converted to Tissue Menaquinone-4 in Mice

BACKGROUND

Vitamin K is a term that comprises a family of structurally related quinones, phylloquinone (PK) and the menaquinones (MKn), that share a common naphthoquinone ring but vary in sidechain length (n) and saturation. Dietary PK is a biosynthetic precursor to tissue menaquinone-4 (MK4), but little is known about the absorption and metabolism of dietary MKn.

OBJECTIVE

To characterize the absorption and metabolism of dietary MKn relative to PK.

METHODS

In the 4-week diet study, 10-week-old male and female C57BL/6 mice were pair-fed a vitamin K deficient diet (control) or a diet supplemented with 5.0 μmol/kg total PK, MK4, and/or MK9 (separately and in combination). In the 1-week stable isotope study, 12-week-old mice were pair-fed diets containing 2.2 μmol/kg PK (unlabeled control), 2H7PK, 13C11MK4, 2H7MK7, or 2H7MK9. Vitamin K tissue content was quantified by HPLC and/or LC-MS, and concentrations were compared by sex and diet group using 2-factor ANOVA.

RESULTS

Regardless of the form(s) of vitamin K provided in the diet, tissue MK4 concentrations did not differ across equimolar supplemented groups in the kidney, adipose, reproductive organ, bone, or pancreas in either males or females in the diet study (all P values > 0.05). Isotopic labeling confirmed the naphthoquinone ring of MK4 in tissues originated from the administered dietary PK or MKn. Despite equimolar supplementation, accumulation of the administered dietary form differed across diet groups in small intestinal segments (all P values < 0.002) and the liver (P < 0.001). Female mice had greater total vitamin K than males in every tissue examined (P < 0.05).

CONCLUSIONS

Dietary PK, MK4, MK7, and MK9 all served as precursors to tissue MK4 in mice. This study expands our understanding of vitamin K metabolism and supports a common conversion mechanism of all dietary vitamin K forms to MK4. Further investigation of the metabolism and physiological roles of MK4 that may be independent of classical vitamin K function is warranted.

The effect of menaquinone-7 supplementation on dp-ucMGP, PIVKAII, inflammatory markers, and body composition in type 2 diabetes patients: a randomized clinical trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a common disorder that is characterized by chronic hyperglycemia and chronic inflammation, which also have a reinforcing effect on each other. The present research studied the effects of menaquinone (MK-7) supplementation on serum dp-ucMGP (dephospho uncarboxylated Matrix Gla Protein), PIVKAII (Prothrombin Induced by Vitamin K Absence), inflammatory markers and body composition indices in type 2 diabetes mellitus (T2DM) patients.

METHODS

This 12-week double-blind placebo-controlled randomized clinical trial allocated 60 T2DM patients equally into a MK-7 (200 mcg/day) group or a placebo group. All patients also received dietary advice at the beginning of study and their dietary intakes were checked using a 3-day food record. The body composition of each patient was also measured and their vitamin K status was assessed using the ELISA method to measure serum dp-ucMGP and PIVKAII. In addition, inflammatory status indices were also measured, including hsCRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6) and TNF-α (tumor necrosis factor alpha). All measurements were made both before and after the intervention period.

RESULTS

In total 45 patients completed the trial (MK-7 group = 23 and placebo group = 22). The calorie and macronutrient intake of the two groups were similar pre and post intervention. There were statistically significant increases in dietary vitamin K intake for both groups over the course of the study (p < 0.05), but the intergroup differences were not significant. The body composition indices (i.e., body fat percentage, fat mass, fat free mass, muscle mass, bone mass and total body water) were not significantly different between groups or across the trial. The serum levels of the vitamin K markers, PIVKAII and dp-ucMGP, decreased significantly in the MK-7 group over the course of the study (p < 0.05), but there was no decrease in the placebo group. However, after adjusting for the baseline levels and changes in vitamin K intake, the between group differences were only significant for PIVKAII (p < 0.05). Following the intervention, the serum levels of the inflammatory markers (hsCRP, IL-6, and TNF-α) were significantly lower in the MK-7 group (p < 0.05), but not in the placebo group. However, the between group differences in the inflammatory markers were not statistically significant.

CONCLUSIONS

Although further studies are needed, it appears that MK-7 supplementation can be effective in improving PIVKAII levels, but not for improving dp-ucMGP, inflammatory status or the body composition indices of T2DM patients.

TRIAL REGISTRATION NUMBER

This study was prospectively registered at the Iranian Registry of Clinical Trials on the 20th of May 2019 (ID: IRCT20100123003140N22).

Reply to Janssen et al. Comment on "Sobczyk, M.K.; Gaunt, T.R. The Effect of Circulating Zinc, Selenium, Copper and Vitamin K1 on COVID-19 Outcomes: A Mendelian Randomization Study. Nutrients 2022, 14, 233"

In their correspondence arising from our recent manuscript [...].

Comment on Sobczyk, M.K.; Gaunt, T.R. The Effect of Circulating Zinc, Selenium, Copper and Vitamin K1 on COVID-19 Outcomes: A Mendelian Randomization Study. Nutrients 2022, 14, 233

Sobczyk and Gaunt genetically predicted circulating zinc, selenium, copper, and vitamin K1 levels-instead of directly measuring nutrients in blood-and hypothesized that these levels would associate with SARS-CoV-2 infection and COVID-19 severity [...].

Vitamin K status, all-cause mortality, and cardiovascular disease in adults with chronic kidney disease: the Chronic Renal Insufficiency Cohort

BACKGROUND

Vascular calcification contributes to cardiovascular disease (CVD) and mortality in individuals with chronic kidney disease (CKD). Vitamin K-dependent proteins function as calcification inhibitors in vascular tissue.

OBJECTIVES

We sought to determine the association of vitamin K status with mortality and CVD events in adults with CKD.

METHODS

Plasma dephospho-uncarboxylated matrix gla protein ((dp)ucMGP), which increases when vitamin K status is low, and plasma phylloquinone (vitamin K1), which decreases when vitamin K status is low, were measured in 3066 Chronic Renal Insufficiency Cohort participants (median age = 61 y, 45% female, 41% non-Hispanic black, median estimated glomerular filtration rate [eGFR] = 41 mL/min/1.73m2). The association of vitamin K status biomarkers with all-cause mortality and atherosclerotic-related CVD was determined using multivariable Cox proportional hazards regression.

RESULTS

There were 1122 deaths and 599 atherosclerotic CVD events over the median 12.8 follow-up years. All-cause mortality risk was 21-29% lower among participants with plasma (dp)ucMGP <450 pmol/L (n = 2361) compared with those with plasma (dp)ucMGP ≥450 pmol/L (adjusted HRs [95% CIs]: <300 pmol/L = 0.71 [0.61, 0.83], 300-449 pmol/L = 0.77 [0.66, 0.90]) and 16-19% lower among participants with plasma phylloquinone ≥0.50 nmol/L (n = 2421) compared to those with plasma phylloquinone <0.50 nmol/L (adjusted HRs: 0.50, 0.99 nmol/L = 0.84 [0.72, 0.99], ≥1.00 nmol/L = 0.81 [0.70, 0.95]). The risk of atherosclerotic CVD events did not significantly differ across plasma (dp)ucMGP or phylloquinone categories.

CONCLUSIONS

Two biomarkers of vitamin K status were associated with a lower all-cause mortality risk but not atherosclerotic CVD events. Additional studies are needed to clarify the mechanism underlying this association and evaluate the impact of improving vitamin K status in people with CKD.

Feeding Practice and Delivery Mode Are Determinants of Vitamin K in the Infant Gut: An Exploratory Analysis

Background

Infants have low stores of vitamin K at birth. Dietary intake of phylloquinone (PK) differs dramatically by infant feeding practice, but the contribution of microbially produced vitamin K (menaquinones) to infant vitamin K status is not well understood.

Objectives

The objective of this study was to investigate determinants of infant fecal vitamin K profiles in mother-infant dyads at 6 wk postpartum.

Methods

Fecal and breast milk samples were collected from a subsample of breastfeeding (n = 23) or formula-feeding (n = 23) mother and infant dyads, delivered vaginally (n = 26) or by cesarean section (CS) (n = 20) in the Synergistic Theory and Research on Nutrition and Growth (STRONG) Kids 2 cohort. Vitamin K concentrations in breast milk and feces were analyzed by LC/MS and/or HPLC. Fecal bacterial metagenomes were analyzed to derive taxonomy and vitamin K biosynthetic genes. Multivariate linear modeling was used to assess effects of delivery and feeding modes on infant fecal vitamin K.

Results

Breast milk contained 1.3 ± 0.2 ng/mL PK, and formula was reported to contain 52 ng/mL PK. Fecal PK was 38-times higher (P < 0.001) in formula-fed than breastfed infants. Infant fecal menaquinones (MKn) MK6, MK7, MK12, and MK13 were higher (P < 0.001) in formula-fed than breastfed infants, whereas MK8 predominated in breastfed and was 5-times higher than formula-fed infants. Total MKn were greater (P < 0.001) in vaginally delivered than CS infants. Relative abundances of 33 bacterial species were affected by feeding mode, 2 by delivery mode, and 4 by both (P < 0.05). Bacterial gene content of 5/12 vitamin K biosynthetic genes were greater (P < 0.05) in breastfed compared with formula-fed infants, and 1 differed by delivery mode.

Conclusions

Feeding practice and delivery mode influence bacterial vitamin K production in the infant gut. High concentrations of unmetabolized PK in feces of formula-fed infants suggests formula PK content exceeds the absorptive capacity of the infant gut.

Association of vitamin K with cognitive decline and neuropathology in community‐dwelling older persons

Higher vitamin K intakes have been associated with better cognitive function, suggestive of a vitamin K mechanistic effect or simply reflective of a healthy diet. To test the hypothesis that brain vitamin K is linked to cognitive decline and dementia, vitamin K concentrations were measured in four brain regions, and their associations with cognitive and neuropathological outcomes were estimated in 325 decedents of the Rush Memory and Aging Project. Menaquinone‐4 (MK4) was the main vitamin K form in the brain regions evaluated. Higher brain MK4 concentrations were associated with a 17% to 20% lower odds of dementia or mild cognitive impairment (MCI) (P‐value < .014), with a 14% to 16% lower odds of Braak stage ≥IV (P‐value < 0.045), with lower Alzheimer's disease global pathology scores and fewer neuronal neurofibrillary tangles (P‐value < 0.012). These findings provide new and compelling evidence implicating vitamin K in neuropathology underlying cognitive decline and dementia.

Vitamin K Effects on Gas6 and Soluble Axl Receptors in Intensive Care Patients: An Observational Screening Study

Growth arrest-specific gene 6 protein (Gas6) is avitamin K-dependent tissue bound protein. Gas6 has been shown to promote growth and therapy resistance among different types of cancer as well as thromboembolism. The aim of this prospective screening study: ClinicalTrials.gov; Identifier: NTC3782025, was to evaluate the effects of intravenously administered vitamin K1 on Gas6 and its soluble (s)Axl receptor plasma levels in intensive care patients. Vitamin K1 was intravenously injected in non-warfarin treated patients with prolonged Owren prothrombin time international normalized ratio (PT-INR) > 1.2 and blood samples were retrieved before and 20-28 h after injection. Citrate plasma samples from 52 intensive care patients were analysed for different vitamin K dependent proteins. There was a significant, but small increase in median Gas6. Only one patient had a large increase in sAxl, but overall, no significant changes in sAxl Gas6 did not correlate to PT-INR, thrombin generation assay, coagulation factors II, VII, IX and X, but to protein S and decarboxylated matrix Gla protein (dp-ucMGP). In conclusion, there was a small increase in Gas6 over 20-28 h. The pathophysiology and clinical importance of this remains to be investigated. To verify a true vitamin K effect, improvement of Gas6 carboxylation defects needs to be studied.

Association between vitamin K1 intake and mortality in the Danish Diet, Cancer, and Health cohort

Reported associations between vitamin K₁ and both all-cause and cause-specific mortality are conflicting. The 56,048 participants from the Danish Diet, Cancer, and Health prospective cohort study, with a median [IQR] age of 56 [52–60] years at entry and of whom 47.6% male, were followed for 23 years, with 14,083 reported deaths. Of these, 5015 deaths were CVD-related, and 6342 deaths were cancer-related. Intake of vitamin K₁ (phylloquinone) was estimated from a food-frequency questionnaire (FFQ), and its relationship with mortality outcomes was investigated using Cox proportional hazards models. A moderate to high (87–192 µg/d) intake of vitamin K₁ was associated with a lower risk of all-cause [HR (95%CI) for quintile 5 vs quintile 1: 0.76 (0.72, 0.79)], cardiovascular disease (CVD)-related [quintile 5 vs quintile 1: 0.72 (0.66, 0.79)], and cancer-related mortality [quintile 5 vs quintile 1: 0.80 (0.75, 0.86)], after adjusting for demographic and lifestyle confounders. The association between vitamin K₁ intake and cardiovascular disease-related mortality was present in all subpopulations (categorised according to sex, smoking status, diabetes status, and hypertension status), while the association with cancer-related mortality was only present in current/former smokers (p for interaction = 0.002). These findings suggest that promoting adequate intakes of foods rich in vitamin K₁ may help to reduce all-cause, CVD-related, and cancer-related mortality at the population level.

Hepatic and Vascular Vitamin K Status in Patients with High Cardiovascular Risk

Vitamin K dependent proteins (VKDP), such as hepatic coagulation factors and vascular matrix Gla protein (MGP), play key roles in maintaining physiological functions. Vitamin K deficiency results in inactive VKDP and is strongly linked to vascular calcification (VC), one of the major risk factors for cardiovascular morbidity and mortality. In this study we investigated how two vitamin K surrogate markers, dephosphorylated-undercarboxylated MGP (dp-ucMGP) and protein induced by vitamin K absence II (PIVKA-II), reflect vitamin K status in patients on hemodialysis or with calcific uremic arteriolopathy (CUA) and patients with atrial fibrillation or aortic valve stenosis. Through inter- and intra-cohort comparisons, we assessed the influence of vitamin K antagonist (VKA) use, vitamin K supplementation and disease etiology on vitamin K status, as well as the correlation between both markers. Overall, VKA therapy was associated with 8.5-fold higher PIVKA-II (0.25 to 2.03 AU/mL) and 3-fold higher dp-ucMGP (843 to 2642 pM) levels. In the absence of VKA use, non-renal patients with established VC have dp-ucMGP levels similar to controls (460 vs. 380 pM), while in HD and CUA patients, levels were strongly elevated (977 pM). Vitamin K supplementation significantly reduced dp-ucMGP levels within 12 months (440 to 221 pM). Overall, PIVKA-II and dp-ucMGP showed only weak correlation (r2 ≤ 0.26) and distinct distribution pattern in renal and non-renal patients. In conclusion, VKA use exacerbated vitamin K deficiency across all etiologies, while vitamin K supplementation resulted in a vascular VKDP status better than that of the general population. Weak correlation of vitamin K biomarkers calls for thoughtful selection lead by the research question. Vitamin K status in non-renal deficient patients was not anomalous and may question the role of vitamin K deficiency in the pathogenesis of VC in these patients.

Vitamin K in COVID-19—Potential Anti-COVID-19 Properties of Fermented Milk Fortified with Bee Honey as a Natural Source of Vitamin K and Probiotics

Vitamin K deficiency is evident in severe and fatal COVID-19 patients. It is associated with the cytokine storm, thrombotic complications, multiple organ damage, and high mortality, suggesting a key role of vitamin K in the pathology of COVID-19. To support this view, we summarized findings reported from machine learning studies, molecular simulation, and human studies on the association between vitamin K and SARS-CoV-2. We also investigated the literature for the association between vitamin K antagonists (VKA) and the prognosis of COVID-19. In addition, we speculated that fermented milk fortified with bee honey as a natural source of vitamin K and probiotics may protect against COVID-19 and its severity. The results reported by several studies emphasize vitamin K deficiency in COVID-19 and related complications. However, the literature on the role of VKA and other oral anticoagulants in COVID-19 is controversial: some studies report reductions in (intensive care unit admission, mechanical ventilation, and mortality), others report no effect on mortality, while some studies report higher mortality among patients on chronic oral anticoagulants, including VKA. Supplementing fermented milk with honey increases milk peptides, bacterial vitamin K production, and compounds that act as potent antioxidants: phenols, sulforaphane, and metabolites of lactobacilli. Lactobacilli are probiotic bacteria that are suggested to interfere with various aspects of COVID-19 infection ranging from receptor binding to metabolic pathways involved in disease prognosis. Thus, fermented milk that contains natural honey may be a dietary manipulation capable of correcting nutritional and immune deficiencies that predispose to and aggravate COVID-19. Empirical studies are warranted to investigate the benefits of these compounds.

Vitamin K - sources, physiological role, kinetics, deficiency, detection, therapeutic use, and toxicity

Vitamin K is traditionally connected with blood coagulation, since it is needed for the posttranslational modification of 7 proteins involved in this cascade. However, it is also involved in the maturation of another 11 or 12 proteins that play different roles, encompassing in particular the modulation of the calcification of connective tissues. Since this process is physiologically needed in bones, but is pathological in arteries, a great deal of research has been devoted to finding a possible link between vitamin K and the prevention of osteoporosis and cardiovascular diseases. Unfortunately, the current knowledge does not allow us to make a decisive conclusion about such a link. One possible explanation for this is the diversity of the biological activity of vitamin K, which is not a single compound but a general term covering natural plant and animal forms of vitamin K (K₁ and K₂) as well as their synthetic congeners (K₃ and K₄). Vitamin K₁ (phylloquinone) is found in several vegetables. Menaquinones (MK₄–MK₁₃, a series of compounds known as vitamin K₂) are mostly of a bacterial origin and are introduced into the human diet mainly through fermented cheeses. Current knowledge about the kinetics of different forms of vitamin K, their detection, and their toxicity are discussed in this review.

Vitamin K intake and health, consideration from the epidemiological studies

The most fundamental function of vitamin K is to activate the blood coagulation factors in the liver. Despite the recent recognition of its extra-hepatic actions, the current Dietary Reference Intakes for vitamin K is based on the amount necessary for maintaining the normal blood coagulation in many countries. To define the Dietary Reference Intake for vitamin K, appropriate biomarkers well-reflecting the vitamin K status are essential. Unfortunately, however, no markers are currently available with properties enabling us to properly define the vitamin K status; i.g., no interference by other factors and the presence of widely approved cut-off values. Thus, Adequate Intake is determined, which is an index based on the representative dietary intake data from healthy individuals. Recently, epidemiological studies have been reported regarding the relationship between vitamin K and noncommunicable diseases including osteoporotic fracture. Furthermore, studies focusing on the relationship between vitamin K intake and metabolic syndrome, physical function, depression, cognition, and all-cause mortality have become available, although limited in number. This review summarizes the recent findings in favor of the novel functions of vitamin K. More epidemiological studies are needed to define the appropriate vitamin K intake value based on the prevention of various disorders.

Vitamin K metabolism as the potential missing link between lung damage and thromboembolism in Coronavirus disease 2019

Coronavirus disease 2019 (Covid-19), caused by severe acute respiratory syndrome coronavirus (SARS-CoV)-2, exerts far-reaching effects on public health and socio-economic welfare. The majority of infected individuals have mild to moderate symptoms, but a significant proportion develops respiratory failure due to pneumonia. Thrombosis is another frequent manifestation of Covid-19 that contributes to poor outcomes. Vitamin K plays a crucial role in the activation of both pro- and anticlotting factors in the liver and the activation of extrahepatically synthesised protein S which seems to be important in local thrombosis prevention. However, the role of vitamin K extends beyond coagulation. Matrix Gla protein (MGP) is a vitamin K-dependent inhibitor of soft tissue calcification and elastic fibre degradation. Severe extrahepatic vitamin K insufficiency was recently demonstrated in Covid-19 patients, with high inactive MGP levels correlating with elastic fibre degradation rates. This suggests that insufficient vitamin K-dependent MGP activation leaves elastic fibres unprotected against SARS-CoV-2-induced proteolysis. In contrast to MGP, Covid-19 patients have normal levels of activated factor II, in line with previous observations that vitamin K is preferentially transported to the liver for activation of procoagulant factors. We therefore expect that vitamin K-dependent endothelial protein S activation is also compromised, which would be compatible with enhanced thrombogenicity. Taking these data together, we propose a mechanism of pneumonia-induced vitamin K depletion, leading to a decrease in activated MGP and protein S, aggravating pulmonary damage and coagulopathy, respectively. Intervention trials should be conducted to assess whether vitamin K administration plays a role in the prevention and treatment of severe Covid-19.

Role of Vitamin K in CKD: Is Its Supplementation Advisable in CKD Patients?

BACKGROUND

Patients with CKD are at an increased risk of developing vascular calcification (VC) and bone complications which translate into a higher morbidity and mortality. The dephosphorylated and uncarboxylated matrix Gla protein (dp-ucMGP) is considered to be an indicator of vitamin K2 status and correlates with markers of VC. It is activated by γ-glutamyl carboxylase that converts inactive MGP into an active form, and vitamin K2 is a cofactor of this reaction. The active form of MGP is a known inhibitor of arterial wall calcification and plays an important role in bone turnover. Recent studies show poor vitamin K2 status in CKD patients. We aimed to review the literature for the association between vitamin K2 status and calcification and bone disease risk and the efficacy of vitamin K2 supplementation in CKD population.

SUMMARY

Most CKD patients, including those on renal replacement therapy, have vitamin K2 deficiency. The dp-ucMGP level, a marker of vitamin K2 status, is decreased by vitamin K2 supplementation in CKD patients, but there is no unequivocal proof that it influences arterial calcification progression and bone complications. Key Messages: CKD population are at risk of vitamin K deficiency. Supplementation of vitamin K2 is safe and improves the serum markers of its deficiency. There is lack of strong evidence that vitamin K2 supplementation slows progression of calcification or reduces the frequency of bone complications. More prospective studies are needed.

Statins, vascular calcification, and vitamin K-dependent proteins: Is there a relation?

The present cross-sectional clinical study aimed to examine the connection between statin exposure, coronary artery calcification (CAC), and vitamin K-dependent proteins (VKDPs) in patients with cardiovascular (CV) conditions. Two groups of patients were studied: patients with established CV disease (CVD) and healthy patients at moderate risk for CVD (a control group). The groups were also split into statin users and non-users. The following VKDPs were measured in plasma: uncarboxylated Matrix Gla-protein (ucMGP), undercarboxylated (ucOC), and carboxylated osteocalcin (cOC), Gla-rich protein (GRP). CAC score (CACS) was determined by multislice computed tomography. Among all the participants in the study, CACS was more pronounced in statin users compared to non-users; the same was found also among the CVD patients and among the controls. While the levels of ucMGP and GRP did not differ between statin users and non-users, ucOC and ucOC/cOC were significantly elevated in statin users, indicating vitamin K deficiency. There was a positive correlation between the levels of ucOC and CACS in the entire population and in the group of statin users, but not in statin non-users. No association was found between ucMGP or GRP and CACS. Statins had also an impact on the international normalized ratio and interacted with vitamin K antagonists (VKAs). Our results are in agreement with the existing evidence about positive association between statins and vascular calcification. They enlighten to a certain extent the possible mechanisms through which statins may enhance calcium accumulation in arterial wall, namely, by inhibition of vitamin K dependent proteins and functions involved in vascular protection.

Perspective: Evidence before Enthusiasm-A Critical Review of the Potential Cardiovascular Benefits of Vitamin K

A protective role for vitamin K in cardiovascular disease (CVD), a leading cause of morbidity and mortality, has been proposed because vitamin K-dependent proteins, such as matrix Gla (γ-carboxyglutamic acid) protein (MGP), are present in vascular tissue. MGP functions as a vascular calcification inhibitor-but only when it is carboxylated, which requires vitamin K. There is more than one naturally occurring form of vitamin K. Phylloquinone (vitamin K1) is found in plant-based foods, whereas menaquinones (vitamin K2) are a class of vitamin K compounds found in animal-based and fermented foods. Phylloquinone and menaquinones are capable of carboxylating MGP and other vitamin K-dependent proteins. In rodent models, high intakes of either phylloquinone or menaquinone reduced vascular calcification. Evidence of the relative importance of phylloquinone and menaquinone to CVD in humans is limited and controversial. In some observational studies, higher dietary menaquinone intake, but not phylloquinone intake, was associated with less coronary artery calcification (a subclinical manifestation of CVD) and a lower risk for clinical CVD events. These findings have led to claims that menaquinones have unique cardiovascular health benefits compared with phylloquinone. However, this claim is not supported by the results of the limited number of intervention trials conducted to date. The purpose of this review is to evaluate the strengths and limitations of the available evidence regarding the role of vitamin K in vascular calcification, CVD, and mortality.

Effects of bariatric surgery in different obesity phenotypes: Tehran Obesity Treatment Study (TOTS)

BACKGROUND

Not all morbid obese patients suffer from metabolic co-morbidities; thus, a sub-group of metabolically healthy morbid obese (MHMO) individuals are identified. However, the role of bariatric surgery is not well understood in this subgroup.

METHODS

A total of 2244 morbid obese individuals aged 18-65 years undergoing bariatric surgery were selected. Patients were considered MHMO according to the joint interim statement (JIS) definition, as having two or less abnormalities in these five parameters: waist circumference (WC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), systolic or diastolic blood pressure (SBP or DBP), and fasting plasma glucose (FPG). Otherwise, they were considered metabolically unhealthy morbid obese (MUMO). Follow-up data were collected at 6, 12, and 24 months post-surgery.

RESULTS

Prior to surgery, 36.2% of participants were MHMO and had significantly lower BMI, WC, TG, FPG, SBP, and DBP and higher HDL-C compared to MUMO. Both MHMO and MUMO participants showed a significant decrease in BMI, WC, TG, SBP, DBP, and FPG and increase in HDL-C and the percentage of excess weight loss (%EWL). Two-year post-operative changes (from baseline) of BMI, WC, and %EWL were greater in MHMO subjects and changes of TG, HDL-C, DBP, SBP, and FPG were greater in MUMO subjects. Further multivariate regression analysis for delta (∆) change in these characteristics revealed that only the delta (∆) changes of WC and %EWL were statistically different between the two phenotypes and were greater in MHMO subjects, 2 years after the surgery (- 3.077 cm decrease in WC and + 3.612% higher %EWL compared to MUMO subjects).

CONCLUSION

Bariatric surgery is an effective method for reduction of metabolic abnormalities and weight loss in both MUMO and MHMO phenotypes. Benefits of this intervention are comparable between patients with these two obesity phenotypes.