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.

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.

Dietary vitamin K is remodeled by gut microbiota and influences community composition.

Vitamins have well-established roles in bacterial metabolism. Menaquinones (MKn, n = prenyl units in sidechain) are bacterially produced forms of vitamin K produced by the gut microbiota and consumed in the diet. Little is known about the influence of dietary vitamin K quinones on gut microbial composition and MKn production. Here, male and female C57BL6 mice were fed a vitamin K deficient diet or vitamin K sufficient diets containing phylloquinone (PK, plant-based vitamin K form), MK4, and/or MK9. DNA was extracted from cecal contents and 16S sequencing conducted to assess microbial composition. Cecal microbial community composition was significantly different in vitamin K deficient female mice compared to females on vitamin K sufficient diets (all p < .007). Parallel trends were seen in male mice, but were not statistically significant (all p > .05 but <0.1). Next, stable isotope-labeled vitamin K quinones were supplemented to male and female C57BL6 mice (2H7PK, 13C11MK4, 2H7MK7, 2H7MK9) and to an in vitro fermentation model inoculated with human stool (2H7PK, 2H7MK4, 2H7MK9, or vitamin K precursor 2H8-menadione). Vitamin K quinones in feces and culture aliquots were measured using LC-MS. In vivo, supplemented vitamin K quinones were remodeled to other MKn (2H7- or 13C6-labeled MK4, MK10, MK11, and MK12), but in vitro only the precursor 2H8-menadione was remodeled to 2H7MK4, 2H7MK9, 2H7MK10, and 2H7MK11. These results suggest that dietary vitamin K deficiency alters the gut microbial community composition. Further studies are needed to determine if menadione generated by host metabolism may serve as an intermediate in dietary vitamin K remodeling in vivo.

Epigenome-wide association study reveals a molecular signature of response to phylloquinone (vitamin K1) supplementation.

Evidence suggests there are roles for vitamin K in various chronic disease outcomes, but population-level diet and supplement recommendations are difficult to determine due to high levels of variability in measures of status and response to intake compared to other nutrients. In this preliminary investigation, a blood-based epigenome-wide association study (EWAS) comparing responders and non-responders to phylloquinone (vitamin K1) supplementation (NCT00183001) was undertaken in order to better understand the molecular underpinnings of this observed variability. Responders (n = 24) and non-responders (n = 24) were identified in a prior 3-year phylloquinone supplementation trial based on their changes in plasma phylloquinone concentrations. Differential DNA methylation was identified in multiple regions with previously unknown relationships to phylloquinone absorption and metabolism, such as at the TMEM263 locus. A hypothesis-driven analysis of lipid-related genes highlighted a site in the NPC1L1 gene, supplementing existing evidence for its role in phylloquinone absorption. Furthermore, an EWAS for baseline plasma phylloquinone concentrations revealed a strong correlation between the epigenomic signatures of phylloquinone baseline status and response to supplementation. This work can guide future epigenomic research on vitamin K and contributes to the development of more personalized dietary recommendations for vitamin K.

Helicobacter pylori antibiotic eradication coupled with a chemically defined diet in INS-GAS mice triggers dysbiosis and vitamin K deficiency resulting in gastric hemorrhage.

Infection with Helicobacter pylori causes chronic inflammation and is a risk factor for gastric cancer. Antibiotic treatment or increased dietary folate prevents gastric carcinogenesis in male INS-GAS mice. To determine potential synergistic effects, H. pylori-infected male INS-GAS mice were fed an amino acid defined (AAD) diet with increased folate and were treated with antibiotics after 18 weeks of H. pylori infection. Antibiotic therapy decreased gastric pathology, but dietary folate had no effect. However, the combination of antibiotics and the AAD diet induced anemia, gastric hemorrhage, and mortality. Clinical presentation suggested hypovitaminosis K potentially caused by dietary deficiency and dysbiosis. Based on current dietary guidelines, the AAD diet was deficient in vitamin K. Phylloquinone administered subcutaneously and via a reformulated diet led to clinical improvement with no subsequent mortalities and increased hepatic vitamin K levels. We characterized the microbiome and menaquinone profiles of antibiotic-treated and antibiotic-free mice. Antibiotic treatment decreased the abundance of menaquinone producers within orders Bacteroidales and Verrucomicrobiales. PICRUSt predicted decreases in canonical menaquinone biosynthesis genes, menA and menD. Reduction of menA from Akkermansia muciniphila, Bacteroides uniformis, and Muribaculum intestinale were confirmed in antibiotic-treated mice. The fecal menaquinone profile of antibiotic-treated mice had reduced MK5 and MK6 and increased MK7 and MK11 compared to antibiotic-free mice. Loss of menaquinone-producing microbes due to antibiotics altered the enteric production of vitamin K. This study highlights the role of diet and the microbiome in maintaining vitamin K homeostasis.

The Contribution of Lipids to the Interindividual Response of Vitamin K Biomarkers to Vitamin K Supplementation.

SCOPE: A better understanding of factors contributing to interindividual variability in biomarkers of vitamin K can enhance the understanding of the equivocal role of vitamin K in cardiovascular disease. Based on the known biology of phylloquinone, the major form of vitamin K, it is hypothesized that plasma lipids contribute to the variable response of biomarkers of vitamin K metabolism to phylloquinone supplementation. METHODS AND RESULTS: The association of plasma lipids and 27 lipid-related genetic variants with the response of biomarkers of vitamin K metabolism is examined in a secondary analysis of data from a 3-year phylloquinone supplementation trial in men (n = 66) and women (n = 85). Year 3 plasma triglycerides (TG), but not total cholesterol, LDL-cholesterol, or HDL-cholesterol, are associated with the plasma phylloquinone response (men: ß = 1.01, p < 0.001, R2  = 0.34; women: ß = 0.61, p = 0.008, R2  = 0.11; sex interaction p = 0.077). Four variants and the TG-weighted genetic risk score are associated with the plasma phylloquinone response in men only. Plasma lipids are not associated with changes in biomarkers of vitamin K function (undercarboxylated osteocalcin and matrix gla protein) in either sex. CONCLUSION: Plasma TG are an important determinant of the interindividual response of plasma phylloquinone to phylloquinone supplementation, but changes in biomarkers of vitamin K carboxylation are not influenced by lipids.

Association of Vitamin K Status Combined With Vitamin D Status and Lower-Extremity Function: A Prospective Analysis of Two Knee Osteoarthritis Cohorts.

OBJECTIVE: Vitamins K and D are important for the function of vitamin K-dependent proteins in joint tissues. It is unclear whether these nutrients are mutually important to functional outcomes related to knee osteoarthritis (OA). We evaluated the association of vitamin K and D sufficiency with lower-extremity function in the Health, Aging and Body Composition knee OA substudy (Health ABC) and conducted a replication analysis in an independent cohort, the Osteoarthritis Initiative (OAI). METHODS: In Health ABC (60% female, mean ± SD age 75 ± 3 years) baseline nutrient status was measured using circulating vitamin K and 25-hydroxyvitamin D (25[OH]D). Lower-extremity function was assessed using the Short Physical Performance Battery (SPPB) and usual 20-meter gait speed. In the OAI (58% female, mean ± SD age 61 ± 9 years), baseline nutrient intake was estimated by food frequency questionnaire. Lower-extremity function was assessed using usual 20-meter gait speed and chair stand completion time. Multivariate mixed models were used to evaluate the association of vitamin K and D status and intake with lower-extremity function over 4-5 years. RESULTS: Health ABC participants with sufficient plasma vitamin K (≥1.0 nmoles/liter) and serum 25(OH)D (≥50 nmoles/liter) generally had better SPPB scores and faster usual gait speed over followup (P ≤ 0.002). In the OAI, sufficient vitamin K and vitamin D intake combined was associated with overall faster usual gait speed and chair stand completion time over followup (P ≤ 0.029). CONCLUSION: Sufficient vitamin K status combined with sufficient vitamin D status was associated with better lower-extremity function in 2 knee OA cohorts. These findings merit confirmation in vitamin K and D co-supplementation trials.

Vitamin K-Dependent Carboxylation of Matrix Gla Protein Influences the Risk of Calciphylaxis.

Matrix Gla protein (MGP) is a potent inhibitor of vascular calcification. The ability of MGP to inhibit calcification requires the activity of a vitamin K-dependent enzyme, which mediates MGP carboxylation. We investigated how MGP carboxylation influences the risk of calciphylaxis in adult patients receiving dialysis and examined the effects of vitamin K deficiency on MGP carboxylation. Our study included 20 patients receiving hemodialysis with calciphylaxis (cases) and 20 patients receiving hemodialysis without calciphylaxis (controls) matched for age, sex, race, and warfarin use. Cases had higher plasma levels of uncarboxylated MGP (ucMGP) and carboxylated MGP (cMGP) than controls. However, the fraction of total MGP that was carboxylated (relative cMGP concentration = cMGP/[cMGP + uncarboxylated MGP]) was lower in cases than in controls (0.58±0.02 versus 0.69±0.03, respectively; P=0.003). In patients not taking warfarin, cases had a similarly lower relative cMGP concentration. Each 0.1 unit reduction in relative cMGP concentration associated with a more than two-fold increase in calciphylaxis risk. Vitamin K deficiency associated with lower relative cMGP concentration in multivariable adjusted analyses (ß=-8.99; P=0.04). In conclusion, vitamin K deficiency-mediated reduction in relative cMGP concentration may have a role in the pathogenesis of calciphylaxis. Whether vitamin K supplementation can prevent and/or treat calciphylaxis requires further study.

The Decline in Vitamin Research Funding: A Missed Opportunity?

Background: The National Nutrition Research Roadmap has called for support of greater collaborative, interdisciplinary research for multiple areas of nutrition research. However, a substantial reduction in federal funding makes responding to these calls challenging. Objectives: The objectives of this study were to examine temporal trends in research funding and to discuss the potential consequences of these trends. Methods: We searched the NIH RePORTER database to identify NIH research grants and USASpending to identify National Science Foundation and USDA research grants awarded from 1992 to 2015. We focused on those that pertained to vitamin research. For the years 2000 to 2015, we examined funding trends for different vitamins, including vitamins A, B (one-carbon B-vitamins were considered separately from other B-vitamins), C, D, E, and K. Results: From 1992 to 2015, total federal research spending increased from ∼$14 to $45 billion (2016 US dollars). Although vitamin research spending increased from ∼$89 to $95 million, the proportion of grants awarded for vitamin research declined by more than two-thirds, from 0.65% in 1992 to 0.2% in 2015. Federal agencies awarded 6035 vitamin research grants over the time period, with vitamin A associated with the most research projects per year on average (n = 115) and vitamin K the fewest (n = 8). Vitamin D research projects were associated with the greatest average yearly project value ($34.8 million). Conclusions: Vitamin research has faced a disproportionate decline in research funding from 1992 to 2015. Insufficient federal research funding streams risk stalling progress in vitamin research and leaving important advancements unrealized.

Reducing Undercarboxylated Osteocalcin With Vitamin K Supplementation Does Not Promote Lean Tissue Loss or Fat Gain Over 3 Years in Older Women and Men: A Randomized Controlled Trial.

Osteocalcin (OC) is a vitamin K-dependent protein synthesized during bone formation. Mice injected with the undercarboxylated form of OC (ucOC) had more skeletal muscle mass and less fat mass than sham-treated controls, suggesting a unique metabolic role for ucOC. UcOC decreases in response to vitamin K supplementation. Our objective was to determine the effect of reducing ucOC on change in lean tissue and fat mass in older community-dwelling adults (n = 401, mean ± SD 69 ± 6 years) using data from a randomized controlled trial of vitamin K supplementation. Over 3 years, serum ucOC was reduced by 58% in women and by 61% in men randomized to vitamin K, whereas in the control group, ucOC decreased by 1% in women and 4% in men (supplementation*time p < 0.001 in men and women). However, there were no differences in the change in appendicular lean mass (calculated as arm lean mass + leg lean mass) or total body fat mass between women randomized to vitamin K and control over 3 years (supplementation*time p values all ≥ 0.18) or between men randomized to vitamin K and control (supplementation*time p values all ≥ 0.54). Consistent with these findings, ucOC was not associated cross-sectionally with appendicular lean mass or fat mass in men or women after adjustment for total OC at baseline (all p ≥ 0.12). These findings indicate the undercarboxylated form of OC is not implicated in age-related changes in skeletal muscle or adipose tissue mass in older community-dwelling adults. © 2016 American Society for Bone and Mineral Research.

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

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

Vitamin K Status and Lower Extremity Function in Older Adults: The Health Aging and Body Composition Study.

BACKGROUND: While low vitamin K status has been associated with several chronic diseases that can lead to lower extremity disability, it is not known if low vitamin K status is associated with worse lower extremity function. METHODS: Vitamin K status was measured according to plasma phylloquinone (vitamin K1) and dephosphorylated-uncarboxylated MGP (dp-ucMGP) in 1,089 community-dwelling older adults (mean ± SD age =74±3 years; 67% female). Lower extremity function was assessed using the short physical performance battery (SPPB), gait speed, and isokinetic leg strength. Linear regression and mixed models were used to determine the cross-sectional and longitudinal associations between vitamin K status and functional outcome measures. RESULTS: Cross-sectionally, higher plasma phylloquinone was associated with better SPPB scores and 20-m gait speed (p ≤ .05). After 4-5 years, those with ≥1.0nM plasma phylloquinone (the concentration achieved when recommended intakes are met) had better SPPB scores (p = .03) and 20-m gait speed (p < .05). Lower plasma dp-ucMGP (reflective of better vitamin K status) was associated with better SPPB scores and leg strength cross-sectionally (p ≤ .04), but not longitudinally. Neither measure of vitamin K status was associated with walking endurance or with the rate of decline in function. CONCLUSION: Older adults with higher vitamin K status had better physical performance scores at baseline, but data are less consistent longitudinally. Since lower extremity disability is a common consequence of multiple chronic diseases for which a role of vitamin K has been suggested, future studies are needed to determine if vitamin K supplementation could improve function in those with vitamin K insufficiency and clarify underlying mechanism(s).

Inhibiting the progression of arterial calcification with vitamin K in HemoDialysis patients (iPACK-HD) trial: rationale and study design for a randomized trial of vitamin K in patients with end stage kidney disease.

BACKGROUND: Cardiovascular disease, which is due in part to progressive vascular calcification, is the leading cause of death among patients with end stage kidney disease (ESKD) on dialysis. A role for vitamin K in the prevention of vascular calcification is plausible based on the presence of vitamin K dependent proteins in vascular tissue, including matrix gla protein (MGP). Evidence from animal models and observational studies support a role for vitamin K in the prevention of vascular calcification. A large-scale study is needed to investigate the effect of vitamin K supplementation on the progression of vascular calcification in patients with ESKD, a group at risk for sub-clinical vitamin K deficiency. METHODS/DESIGN: We plan a prospective, randomized, double-blind, multicenter controlled trial of incident ESKD patients on hemodialysis in centers within North America. Eligible subjects with a baseline coronary artery calcium score of greater than or equal to 30 Agatston Units, will be randomly assigned to either the treatment group (10 mg of phylloquinone three times per week) or to the control group (placebo administration three times per week). The primary endpoint is the progression of coronary artery calcification defined as a greater than 15% increase in CAC score over baseline after 12 months. DISCUSSION: Vitamin K supplementation is a simple, safe and cost-effective nutritional strategy that can easily be integrated into patient care. If vitamin K reduces the progression of coronary artery calcification it may lead to decreased morbidity and mortality in men and women with ESKD. TRIAL REGISTRATION: NCT 01528800.

CONTEXTE: La maladie cardiovasculaire, qui est partiellement attribuable à la calcification vasculaire progressive, est la cause principale de décès chez les patients atteints d'insuffisance rénale terminale (IRT) en hémodialyse. La vitamine K pourrait jouer un rôle dans la prévention de la calcification vasculaire, en raison de la présence de protéines dépendantes à la vitamine K dans les tissus vasculaires, dont l'ostéocalcine. Le modèle animal, de même que des études d'observation, témoignent du rôle de la vitamine K dans la prévention de la calcification vasculaire. Une étude réalisée à grande échelle serait nécessaire afin d'étudier l'effet de la supplémentation de vitamine K sur la progression de la calcification vasculaire chez les patients atteints d'IRT, un groupe à risque pour les carences infracliniques en vitamine K. MÉTHODE/TYPE D'ÉTUDE: Nous prévoyons effectuer un essai clinique aléatoire, à double insu et multicentrique auprès de patients atteints d'IRT, traités en hémodialyse hospitalière en Amérique du Nord. On affectera au hasard les sujets admissibles qui présentent dans l'artère coronaire un taux de calcium supérieur ou égal à 30 unités d'Agatston, soit au groupe auquel on administre un traitement (10 mg de phylloquinone trois fois par semaine), soit au groupe témoin (administration du placebo trois fois par semaine). Le critère d'évaluation principal est la progression de la calcification de l'artère coronaire, définie comme une augmentation supérieure à 15% (résultat CAC) par rapport au point de référence, au bout de douze mois. DISCUSSION: La supplémentation de vitamine K est une stratégie nutritionnelle à la fois simple, sécuritaire et rentable, qui peut être aisément intégrée aux soins aux patients. S'il s'avère que la vitamine K réduit la progression de la calcification de l'artère coronaire, il pourrait y avoir une diminution de la morbidité et de la mortalité chez les hommes et les femmes atteints d'IRT.

Osteocalcin carboxylation is not associated with body weight or percent fat changes during weight loss in post-menopausal women.

Osteocalcin (OC) is a vitamin K-dependent bone protein used as a marker of bone formation. Mouse models have demonstrated a role for the uncarboxylated form of OC (ucOC) in energy metabolism, including energy expenditure and adiposity, but human data are equivocal. The purpose of this study was to determine the associations between changes in measures of OC and changes in body weight and percent body fat in obese, but otherwise healthy post-menopausal women undergoing a 20-week weight loss program. All participants received supplemental vitamins K and D and calcium. Body weight and body fat percentage (%BF) were assessed before and after the intervention. Serum OC [(total (tOC), ucOC, percent uncarboxylated (%ucOC)], and procollagen type 1N-terminal propeptide (P1NP; a measure of bone formation) were measured. Women lost an average of 10.9 ± 3.9 kg and 4 %BF. Serum concentrations of tOC, ucOC, %ucOC, and P1NP did not significantly change over the twenty-week intervention, nor were these measures associated with changes in weight (all p > 0.27) or %BF (all p > 0.54). Our data do not support an association between any serum measure of OC and weight or %BF loss in post-menopausal women supplemented with nutrients implicated in bone health.

Gamma-carboxylation and fragmentation of osteocalcin in human serum defined by mass spectrometry.

Serum osteocalcin (Oc) concentration is a highly specific measure of bone turnover, but its circulating proteoform(s) have not been well defined. Based on immunological methods, the major forms are thought to be the intact polypeptide and a large N-terminal-mid molecule fragment for which there is no consensus on the precise sequence. Vitamin K-dependent gamma (γ)-carboxylated variants of Oc are also found in circulation but there have been no methods that can define how many of the three potential γ-carboxyglutamic acid (Gla) residues are γ-carboxylated or provide their relative abundances. Recent reports that uncarboxylated and partially γ-carboxylated Oc forms have hormonal function underscore the need for precise evaluation of Oc at all three potential γ-carboxylation sites. Herein, mass spectrometric immunoassay (MSIA) was used to provide qualitative and semiquantitative (relative percent abundance) information on Oc molecular variants as they exist in individual plasma and serum samples. Following verification that observable Oc proteoforms were accurately assigned and not simply ex vivo artifacts, MALDI-MSIA and ESI-MSIA were used to assess the relative abundance of Oc truncation and γ-carboxylation, respectively, in plasma from 130 patients enrolled in vitamin K supplementation trials. Human Oc was found to circulate in over a dozen truncated forms with each of these displaying anywhere from 0-3 Gla residues. The relative abundance of truncated forms was consistent and unaffected by vitamin K supplementation. In contrast, when compared with placebo, vitamin K supplementation dramatically increased the fractional abundance of Oc with three Gla residues, corresponding to a decrease in the fractional abundance of Oc with zero Gla residues. These findings unequivocally document that increased vitamin K intake reduces the uncarboxylated form of Oc. Several reports of a positive effect of vitamin K intake on insulin sensitivity in humans have shown that un- or undercarboxylation of Oc, unlike in mice, is not associated with insulin resistance. Analyses similar to those described here will be useful to understand the functional significance of Oc γ-carboxylation in human health and disease.

Vitamin K: dietary intake and requirements in different clinical conditions.

PURPOSE OF REVIEW: Vitamin K is an enzyme cofactor for the carboxylation of vitamin K-dependent proteins. Functions include coagulation and regulation of calcification. Different clinical conditions may alter vitamin K requirements by affecting vitamin K status and vitamin K-dependent proteins carboxylation that are reviewed here. RECENT FINDINGS: Vitamin K consumption greater than the current usual daily requirement to maintain health is indicated for prevention of vitamin K-deficient bleeding in infants and for rescue of over-anticoagulation in patients on vitamin K-dependent oral anticoagulants. Additional vitamin K intake may be required in malabsorptive conditions such as cystic fibrosis and following bariatric surgery. Carboxylation of vitamin K-dependent proteins occurs in multiple extrahepatic tissues and has been implicated in soft tissue calcification and insulin resistance, although the exact mechanisms have yet to be determined. Contribution of colonic flora to vitamin K requirements remains controversial. SUMMARY: With the increased incidence of vitamin K-deficient bleeding and weight-loss surgical procedures, healthcare professionals need to monitor vitamin K status in certain patient populations. Future research on the roles of vitamin K in extrahepatic tissues as they pertain to chronic disease will provide insight into the therapeutic potential of vitamin K and lead to the development of recommendations for specific clinical populations.

Increase in plasma phylloquinone concentrations following acupoint injection for the treatment of primary dysmenorrhea.

The therapeutic benefits of acupoint injection of vitamin K in spleen-6 (SP6) for the treatment of primary dysmenorrhea have been observed in limited clinical settings. However, menadione, the form of vitamin K most studied for treating dysmenorrhea, is not routinely used in clinical practice in North America. As part of a larger clinical trial among women aged 18-25 years with primary dysmenorrhea, we conducted a substudy to test the plasma concentration of phylloquinone (vitamin K1). We collected blood samples from four women before and 24-48 hours after an acupoint injection of phylloquinone in SP6. Despite the rapid turnover of phylloquinone observed in previous studies, we found that the plasma phylloquinone concentrations increased significantly from preinjection to 1-2 days after the injection. Interestingly, higher phylloquinone concentrations were correlated with less pain intensity among women with dysmenorrhea. Additional research is needed to understand the association between vitamin K and menstrual pain, including the role of vitamin K deficiency in inflammation and pain, and on the possible mechanisms of acupoint injection of vitamin K for the treatment of primary dysmenorrhea.

Association between circulating vitamin K1 and coronary calcium progression in community-dwelling adults: the Multi-Ethnic Study of Atherosclerosis.

BACKGROUND: Animal studies have shown that vitamin K treatment reduced vascular calcification, but human data are limited. OBJECTIVE: We determined the association between vitamin K status and coronary artery calcium (CAC) progression in the Multi-Ethnic Study of Atherosclerosis by using a case-cohort design. DESIGN: Serum phylloquinone (vitamin K1) was measured in 296 participants with extreme CAC progression and 561 randomly selected participants without extreme CAC progression; all subjects had baseline and follow-up CAC measures (mean follow-up: 2.5 y). A serum vitamin K1 concentration was considered low at <1.0 nmol/L (the distribution median). Outcomes were replicated by using post hoc per-protocol analyses of a vitamin K1 supplementation trial. RESULTS: The OR (95% CI) for extreme CAC progression for subjects with low serum vitamin K1 compared with subjects without extreme CAC progression was 1.34 (0.94, 1.90; NS) when adjusted for demographics and confounders. A significant interaction between low vitamin K1 and antihypertension medication use was detected (P = 0.016). Hypertension medication users with low serum vitamin K1 were more likely to have extreme CAC progression than were medication users without extreme CAC progression [OR (95% CI): 2.37 (1.38, 4.09)]. In replication, baseline antihypertensive medication users in the supplementation group had less CAC progression than did those in the control group [adjusted mean ± SEM of the 3-y CAC change was +5 ± 20 Agatston units (AU) in the vitamin K1 group (n = 40) and +44 ± 13 AU in the placebo group (n = 49); P < 0.01]. CONCLUSIONS: Although the point estimate of our primary analysis suggests low serum vitamin K1 is associated with greater CAC progression, the difference was NS. Low serum vitamin K1 was significantly associated with CAC progression in antihypertension medication users, which, to our knowledge, is a novel finding conditionally replicated by using an independent sample. Intervention trials are needed to determine whether improving serum vitamin K1 reduces CAC progression, especially in hypertensive individuals. This trial was registered at clinicaltrials.gov as NCT00183001.

Dietary vitamin K and therapeutic warfarin alter the susceptibility to vascular calcification in experimental chronic kidney disease.

The leading cause of death in patients with chronic kidney disease (CKD) is cardiovascular disease, with vascular calcification being a key modifier of disease progression. A local regulator of vascular calcification is vitamin K. This γ-glutamyl carboxylase substrate is an essential cofactor in the activation of several extracellular matrix proteins that inhibit calcification. Warfarin, a common therapy in dialysis patients, inhibits the recycling of vitamin K and thereby decreases the inhibitory activity of these proteins. In this study, we sought to determine whether modifying vitamin K status, either by increasing dietary vitamin K intake or by antagonism with therapeutic doses of warfarin, could alter the development of vascular calcification in male Sprague-Dawley rats with adenine-induced CKD. Treatment of CKD rats with warfarin markedly increased pulse pressure and pulse wave velocity, as well as significantly increased calcium concentrations in the thoracic aorta (3-fold), abdominal aorta (8-fold), renal artery (4-fold), and carotid artery (20-fold). In contrast, treatment with high dietary vitamin K1 increased vitamin K tissue concentrations (10-300-fold) and blunted the development of vascular calcification. Thus, vitamin K has an important role in modifying mechanisms linked to the susceptibility of arteries to calcify in an experimental model of CKD.

Calcium intake is not associated with increased coronary artery calcification: the Framingham Study.

BACKGROUND: Adequate calcium intake is known to protect the skeleton. However, studies that have reported adverse effects of calcium supplementation on vascular events have raised widespread concern. OBJECTIVE: We assessed the association between calcium intake (from diet and supplements) and coronary artery calcification, which is a measure of atherosclerosis that predicts risk of ischemic heart disease independent of other risk factors. DESIGN: This was an observational, prospective cohort study. Participants included 690 women and 588 men in the Framingham Offspring Study (mean age: 60 y; range: 36-83 y) who attended clinic visits and completed food-frequency questionnaires in 1998-2001 and underwent computed tomography scans 4 y later in 2002-2005. RESULTS: The mean age-adjusted coronary artery-calcification Agatston score decreased with increasing total calcium intake, and the trend was not significant after adjustment for age, BMI, smoking, alcohol consumption, vitamin D-supplement use, energy intake, and, for women, menopause status and estrogen use. Multivariable-adjusted mean Agatston scores were 2.36, 2.52, 2.16, and 2.39 (P-trend = 0.74) with an increasing quartile of total calcium intake in women and 4.32, 4.39, 4.19, and 4.37 (P-trend = 0.94) in men, respectively. Results were similar for dietary calcium and calcium supplement use. CONCLUSIONS: Our study does not support the hypothesis that high calcium intake increases coronary artery calcification, which is an important measure of atherosclerosis burden. The evidence is not sufficient to modify current recommendations for calcium intake to protect skeletal health with respect to vascular calcification risk.