Vitamin K Nutrition and Bone Health

Pregnane X Receptor Signaling Pathway and Vitamin K: Molecular Mechanisms and Clinical Relevance in Human Health

This review explores the likely clinical impact of Pregnane X Receptor (PXR) activation by vitamin K on human health. PXR, initially recognized as a master regulator of xenobiotic metabolism in liver, emerges as a key regulator influencing intestinal homeostasis, inflammation, oxidative stress, and autophagy. The activation of PXR by vitamin K highlights its role as a potent endogenous and local agonist with diverse clinical implications. Recent research suggests that the vitamin K-mediated activation of PXR highlights this vitamin's potential in addressing pathophysiological conditions by promoting hepatic detoxification, fortifying gut barrier integrity, and controlling pro-inflammatory and apoptotic pathways. PXR activation by vitamin K provides an intricate association with cancer cell survival, particularly in colorectal and liver cancers, to provide new insights into potential novel therapeutic strategies. Understanding the clinical implications of PXR activation by vitamin K bridges molecular mechanisms with health outcomes, further offering personalized therapeutic approaches for complex diseases.

Vitamin K insufficiency and the prophylaxis strategy in term healthy infants: A multicentre study

BACKGROUND/AIM

Late vitamin K deficiency bleeding (VKDB) during early infancy is a serious problem worldwide. Vitamin K (VK) deficiency commonly occurs in newborns who are exclusively breastfed. Protein Induced by VK Absence (PIVKA-II) has been identified as an early indicator of subclinical VK deficiency in neonates, surpassing prothrombin time. To assess PIVKA-II levels at 48 h, 1 and 3 months of age in full-term newborns who were exclusively breastfed and received varying VKDB prophylaxis regimens.

METHODS

A prospective observational study was conducted in four hospitals, enrolling 105 newborns. PIVKA-II levels were measured using a sandwich-type enzyme-linked immunosorbent assay.

RESULTS

At 48 h of age, there was no significant difference in PIVKA-II concentrations between newborns who received intramuscular administration of 1 mg of phylloquinone (VK1) and those who received oral administration of 2 mg of VK1 at birth. At 1 and 3 months of life, infants who received any supplementation regimen between 2 and 14 weeks exhibited significantly lower PIVKA-II concentrations compared to infants who received only 1 mg of intramuscular VK1 at birth. The prophylaxis involving a dose of 1 mg of intramuscular VK1 at birth followed by oral administration of 150 μg/day of VK1 from the 2nd to the 14th week of life showed the lowest PIVKA-II blood concentrations.

CONCLUSIONS

Oral supplementation of VK1 after discharge significantly reduced PIVKA-II concentrations in exclusively breastfed term infants. These findings suggest the importance of oral VK1 supplementation in exclusively breastfed infants during their first 3 months of life to avoid the risk of VK insufficiency.

Vitamin K: Infection, Inflammation, and Auto-Immunity

Vitamin K (VK) comprises a group of substances with chlorophyll quinone bioactivity and exists in nature in the form of VK1 and VK2. As its initial recognition originated from the ability to promote blood coagulation, it is known as the coagulation vitamin. However, based on extensive research, VK has shown potential for the prevention and treatment of various diseases. Studies demonstrating the beneficial effects of VK on immunity, antioxidant capacity, intestinal microbiota regulation, epithelial development, and bone protection have drawn growing interest in recent years. This review article focuses on the mechanism of action of VK and its potential preventive and therapeutic effects on infections (eg, asthma, COVID-19), inflammation (eg, in type 2 diabetes mellitus, Alzheimer's disease, Parkinson's disease, cancer, aging, atherosclerosis) and autoimmune disorders (eg, inflammatory bowel disease, type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis). In addition, VK-dependent proteins (VKDPs) are another crucial mechanism by which VK exerts anti-inflammatory and immunomodulatory effects. This review explores the potential role of VK in preventing aging, combating neurological abnormalities, and treating diseases such as cancer and diabetes. Although current research appoints VK as a therapeutic tool for practical clinical applications in infections, inflammation, and autoimmune diseases, future research is necessary to elucidate the mechanism of action in more detail and overcome current limitations.

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.

Effects of vitamin K supplementation on reproductive performance and bone metabolism-related biochemical markers in lactation sows

OBJECTIVE

This study was conducted to evaluate the effects of vitamin K (VK) supplementation on reproductive performance and bone metabolism-related biochemical markers in sows.

METHODS

Twenty-four Large White×Landrace sows (mean parity 4.04) were randomly assigned to two dietary treatments (NC diet, a basal diet with 0.5 mg/kg of VK3; VK diet, a basal diet with 5 mg/kg of VK3) with twelve replicates per treatment and one sow per replicate according to parity. The experiment started on day 107 of gestation and lasted until day 21 of lactation (weaning).

RESULTS

We observed that there were no differences (p>0.05) in average daily feed intake, backfat loss of sows, live piglet number at birth and weaning, average birth weight, average weaning weight, and average daily gain of piglets between two treatments. The apparent total tract digestibility of phosphorus was increased (p<0.05) in VK sows compared with NC sows. The serum bone alkaline phosphatase, osteocalcin, type I procollagen aminoterminal peptide, and type I procollagen carboxyl-terminal peptide on day of farrowing were higher (p<0.05) in VK sows than in NC sows. The serum phosphorus, parathyroid hormone, tartrate-resistant acid phosphatase, and tumor necrosis factor-alpha on day of weaning were lower (p<0.05) in VK sows compared with NC sows.

CONCLUSION

Therefore, the overall results suggested that increasing dietary VK3 (0.5 to 5 mg/kg) during lactation improved the apparent total tract digestibility of phosphorus and serum bone metabolism biochemical markers in sows.

Study protocol of the InterVitaminK trial: a Danish population-based randomised double-blinded placebo-controlled trial of the effects of vitamin K (menaquinone-7) supplementation on cardiovascular, metabolic and bone health

INTRODUCTION

Vitamin K has been suggested to have protective effects against progression of vascular calcification and development of cardiovascular disease (CVD). However, few well-powered randomised controlled trials have examined whether vitamin K prevents progression of vascular calcification in individuals from the general population. The aim of the InterVitaminK trial is to investigate the effects of vitamin K supplementation (menaquinone-7, MK-7) on cardiovascular, metabolic, respiratory and bone health in a general ageing population with detectable vascular calcification.

METHODS AND ANALYSIS

The InterVitaminK trial is a randomised, double-blinded, placebo-controlled, trial. A total of 450 men and women aged 52-82 years with detectable coronary artery calcification (CAC), but without manifest CVD, will be randomised (1:1) to receive daily MK-7 (333 µg/day) or placebo tablets for 3 years. Health examinations are scheduled at baseline, and after 1, 2 and 3 years of intervention. Health examinations include cardiac CT scans, measurements of arterial stiffness, blood pressure, lung function, physical function, muscle strength, anthropometric measures, questionnaires on general health and dietary intake, and blood and urine sampling. The primary outcome is progression of CAC from baseline to 3-year follow-up. The trial has 89% power to detect a between-group difference of at least 15%. Secondary outcomes are bone mineral density, pulmonary function and biomarkers of insulin resistance.

ETHICS AND DISSEMINATION

Oral MK-7 supplementation is considered safe and has not been found to cause severe adverse events. The Ethical Committee of the Capital Region (H-21033114) approved the protocol. Written informed consent is obtained from all participants and the trial is conducted in accordance with the Declaration of Helsinki II. Both negative and positive findings will be reported.

TRIAL REGISTRATION NUMBER

NCT05259046.

Effects of mixed oil emulsion on short-term clinical outcomes in premature infants: A prospective, multicenter, randomized controlled trial

OBJECTIVE

This study compared the clinical effects of two different lipid emulsions in premature infants with gestational age < 32 weeks (VPI) or birth weight < 1500 g (VLBWI) to provide an evidence-based medicine basis for optimizing intravenous lipid emulsion.

METHODS

This was a prospective multicenter randomized controlled study. A total of 465 VPIs or VLBWIs, admitted to the neonatal intensive care unit of five tertiary hospitals in China from March 1, 2021 to December 31, 2021, were recruited. All subjects were randomly allocated into two groups, namely, medium-chain triglycerides/long-chain triglycerides (MCT/LCT) group (n = 231) and soybean oil, medium-chain triglycerides, olive oil, and fish oil (SMOF) group (n = 234). Clinical features, biochemical indexes, nutrition support therapy, and complications were analyzed and compared between the two groups.

RESULTS

No significant differences were found in perinatal data, hospitalization, parenteral and enteral nutrition support between the two groups (P > 0.05). Compared with the MCT/LCT group, the incidence of neonates with a peak value of total bilirubin (TB) > 5 mg/dL (84/231 [36.4% vs. 60/234 [25.6%]), a peak value of direct bilirubin (DB) ≥ 2 mg/dL (26/231 [11.3% vs. 14/234 [6.0%]), a peak value of alkaline phosphatase (ALP) > 900 IU/L (17/231 [7.4% vs. 7/234 [3.0%]), and a peak value of triglycerides (TG) > 3.4 mmol/L (13/231 [5.6% vs. 4/234[1.7%]]) were lower in the SMOF group (P < 0.05). Univariate analysis showed that in the subgroup analysis of < 28 weeks, the incidence of parenteral nutrition-associated cholestasis (PNAC) and metabolic bone disease of prematurity (MBDP) were lower in the SMOF group (P = 0.043 and 0.029, respectively), whereas no significant differences were present in the incidence of PNAC and MBDP between the two groups at > 28 weeks group (P = 0.177 and 0.991, respectively). Multivariate logistic regression analysis revealed that the incidence of PNAC (aRR: 0.38, 95% confidence interval [CI]: 0.20-0.70, P = 0.002) and MBDP (aRR: 0.12, 95% CI: 0.19-0.81, P = 0.029) in the SMOF group were lower than that in the MCT/LCT group. In addition, no significant differences were recorded in the incidence of patent ductus arteriosus, feeding intolerance, necrotizing enterocolitis (Bell's stage ≥ 2), late-onset sepsis, bronchopulmonary dysplasia, intraventricular hemorrhage, periventricular leukomalacia, retinopathy of prematurity and extrauterine growth retardation between the two groups (P > 0.05).

CONCLUSIONS

The application of mixed oil emulsion in VPI or VLBWI can reduce the risk of plasma TB > 5 mg/dL, DB ≥ 2 mg/dL, ALP > 900 IU/L, and TG > 3.4 mmol/L during hospitalization. SMOF has better lipid tolerance, reduces the incidence of PNAC and MBDP, and exerts more benefits in preterm infants with gestational age < 28 weeks.

Reference Range of Vitamin K Evaluating Indicators in Chinese Childbearing Women

BACKGROUND

Vitamin K is an essential fat-soluble vitamin for the human body and its functions, such as promoting blood coagulation, bone health and preventing atherosclerosis, have attracted increasing attention. However, there is no recognized indicator and corresponding reference range for evaluating vitamin K status of different populations at present. The aim of this study is to establish a reference range for vitamin K evaluating indicators in healthy women of childbearing age in China.

METHODS

The population sample in this study was from the Chinese Adult Chronic Disease and Nutrition Surveillance (CACDNS) 2015-2017. A total of 631 healthy women of childbearing age (18-49 years) were included using a series of strict inclusion and exclusion criteria. The concentrations of VK1, MK-4 and MK-7 in serum were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The other commonly-reported indicators evaluating vitamin K nutritional status, including undercarboxylated osteocalcin (ucOC), osteocalcin (OC), matrix Gla protein (MGP), desphosphorylated undercaboxylated MGP (dp-ucMGP) and protein induced by vitamin K absence II (PIVKA-II), were measured by enzyme-linked immunosorbent assay (ELISA). The reference range was obtained by calculating the 2.5% to 97.5% interval of the vitamin K evaluating indicators in the reference population.

RESULTS

The reference ranges of VK1, MK-4 and MK-7 in serum were 0.21-3.07 ng/mL, 0.02-0.24 ng/mL and 0.12-3.54 ng/mL, respectively. The reference ranges of ucOC, %ucOC, dp-ucMGP and PIVKA-II were 1.09-2.51 ng/mL, 5.80-22.78%, 2.69-5.88 ng/mL and 3.98-8.40 ng/mL, respectively. The cut-off values that can be used to evaluate subclinical vitamin K deficiency were as follows: VK1 < 0.21 ng/mL, MK-7 < 0.12 ng/mL, ucOC > 2.51 ng/mL, %ucOC > 22.78%, dp-ucMGP > 5.88 ng/mL and PIVKA-II > 8.40 ng/mL.

CONCLUSION

The reference range of VK1, MK-4, MK-7 and vitamin K-related indicators for healthy women of childbearing age established in this study could be used to assess the nutritional and health status of this population.

Low Vitamin K and Vitamin D Dietary Intake in Patients with Inflammatory Bowel Diseases

The inadequate dietary intake of Vitamin D and Vitamin K is an easily reversible factor favoring IBD-associated bone loss, but data on Vitamin K are lacking. A 28-item quantitative food frequency questionnaire was administered to 193 IBD patients (89 Crohn’s disease and 104 ulcerative colitis), and 199 controls. Patients’ demographics, clinical and laboratory findings were analyzed in relation to recommended daily allowances. VitD intake was inadequate both in the IBD and control patients (8.3 ± 4.5 µg/day in IBD, 53.1% RDA, and 9.7 ± 5.9 µg/day, 63.2% RDA, respectively). Conversely, the mean ViK intake was less than adequate in IBD, at 116.7 ± 116.3 µg/day (78.7% RDA), and high in controls, at 203.1 ± 166.9 µg/day (138.8% RDA). Nonetheless, due to marked inter-individual differences, diets were severely lacking VitK in 40% of UC and 49% of CD patients, more so in females and those with active disease. The intake of Vit D was non-significantly lower in colitis than that in Crohn’s disease (7.9 vs. 8.7 µg/day). The opposite was observed for VitK (123.5 vs. 107.0 µg/day). Thus, the diet lacks the micronutrients involved in bone wellbeing in a large proportion of IBD patients. While VitD supplementation is the rule, VitK shortages need proactive nutritional intervention.

Correlation between Dietary Intake of Vitamins and Oral Health Behaviors: A Cross-Sectional Study

This study aimed to investigate whether oral health behaviors were related to the dietary intake of vitamins. In this cross-sectional study, we included respondents of the 2016 national health and nutrition examination survey, and dental diseases from Hyogo Prefecture, Japan. Data on sociodemographic characteristics, findings of blood tests related to metabolic syndrome, dietary intake, oral health status, and behaviors were collected. Participants were divided into two groups based on their oral health behavior: the yes group (performed interdental cleaning or tongue brushing) and the no group (did not perform the behaviors). The study included 218 participants (male: 107, female: 111) aged 64.5 (range, 22-93) years. There were 133 (61.0%) and 85 (39.0%) participants in the yes and no groups, respectively. The daily intake of vitamins A, B₂, B₆, E, and K, folic acid, and niacin in the yes group was significantly higher than that in the no group. Oral health behavior correlated with the intake of vitamin B₂ (p = 0.029), folic acid (p = 0.006), and vitamin K (p = 0.043) after adjusting for possible confounders. Oral health behavior (interdental cleaning or tongue brushing) correlated with the daily intake of vitamins B₂, K, and folic acid.

Twelve Loci Associated With Bone Density in Middle-aged and Elderly Chinese: The Shanghai Changfeng Study

CONTEXT

Previous genome-wide association studies (GWASs) of bone mineral density (BMD) were mainly conducted in Europeans.

OBJECTIVE

To explore genetic variants that affect BMD and sex differences in a Chinese population.

METHODS

A total of 5428 middle-aged and elderly Chinese were included. Dual-energy X-ray absorptiometry was used to measure BMD at the lumbar spine, and total and specific sites of the hip. A mixed linear model was used to analyze the associations between BMD and autosomal genetic variants, adjusting for age, age squared, sex, and menopausal women (model 1); model 2 was further adjusted for height and weight. A GWAS of osteoporosis in the Biobank Japan (BBJ) project was used for replication. GWAMA software was used to detect the statistical significance of sex differences of estimated effects. Gene annotation and pathway enrichment analysis were performed.

RESULTS

Women lost BMD at earlier ages and faster than men. The 2 models identified a total of 12 loci that were associated with BMD at any site. Single nucleotide polymorphisms rs72354346, rs2024219, rs1463093, rs10037512, and rs5880932 were successfully replicated in the BBJ. Variations of rs79262027 G>A (VKORC1L1) and rs4795209 A>G (DDX52) were associated with BMD only in men, and rs1239055408 G>GA (KCNJ2) was associated with BMD only in women. Gene enrichment analysis showed that BMD in a Chinese elderly population was mainly related to ossification, bone resorption, sex hormones, and kidney physiology.

CONCLUSION

The present GWAS identified 12 loci that were significantly associated with BMD at any site in a Chinese population, and 3 of them showed sex differences in their effects.

E, K, B5, B6, and B9 vitamins and their specific immunological effects evaluated by flow cytometry

It has been proven that vitamins play an essential role in preventing certain diseases since ancient times. It is thus fruitless to approach the roles of vitamins without making reference to the techniques used in evaluating the effects of these micronutrients. Therefore, the aim of this paper was to summarize the immunological effects of E, K, B5, B6, and B9 vitamins evaluated by flow cytometry. Some of these significant effects were presented and discussed: (a) The role of vitamins E in the prevention and treatment of different types of cancer. (b) The properties of K vitamins in the development and maintenance of pheochromocytoma Cell Line 12 (PC12) cells in Parkinson's disease; (c) The improvement effect of vitamin B5 on the loss of bone mass in low estrogen conditions; (d) The anticancer role of vitamins B6. (e) The role of Vitamin B9 in the regulation of Treg cells. As such, the flow cytometry technique used to assess these properties is essential to evaluate the immunomodulatory effects of certain vitamins. The technique undergoes constant improvement which makes it possible to determine several parameters with a role in the modulation of the immune function and at the same time increase the accuracy of the methods that highlight them.

Functional tooth number in the posterior region associated serum ucOC levels

Purpose

The purpose of this study was to investigate serum undercarboxylated osteocalcin (ucOC) levels in partially edentulous patients scheduled to receive implant treatment and determine the association between ucOC levels, vegetable intake, vitamin K, dietary fiber intake, and functional tooth number in the posterior region (p-FTN).

Methods

A total of 46 patients (20 male and 26 female, 61.9 ± 12.7 years old) were included. The association among serum ucOC levels, vegetable intake, vitamin K and dietary fiber intake was assessed using Spearman’s rank correlation coefficient and binary logistic regression analysis.

Results

In total, 35% of patients (16/46 subjects) showed an abnormally high ucOC level (≧ 4.5 ng/mL). p-FTN showed a weak positive correlation with vegetable intake, vitamin K and dietary fiber intake (r = 0.28, 0.21, and 0.14, respectively) and a significant negative correlation with ucOC levels (r = − 0.51). Multivariate analysis demonstrated that p-FTN as well as vitamin K intake showed a significant negative association with serum ucOC levels.

Conclusions

More than one-third of patients showed abnormally high ucOC levels. p-FTN showed a negative association with serum ucOC levels, which indicated the possibility that oral status affected bone quality.

New Insights into Vitamin K-From Its Natural Sources through Biological Properties and Chemical Methods of Quantitative Determination

Vitamin K is one of the many health-promoting substances whose impact on the human body has been underestimated until recently. However, recently published research results have changed this situation, prompting some researchers to consider it a new panacea for diseases of old age. The result is a significant increase in interest in the accurate analysis of vitamin K in various types of samples, ranging from food, through dietary supplements, to biological matrices and clinical trials, both observational and interventional. This review summarizes the current state of knowledge about the proven and speculated biological activity of vitamin K and its importance for the world's aging societies, including the methods used for its isolation and analysis in various matrices types. Of all the analytical methods, the currently preferred methods of choice for the direct analysis of vitamin K are chromatographic methods, in particular liquid chromatography-tandem mass spectrometry. This technique, despite its sensitivity and selectivity, requires an appropriate stage of sample preparation. As there is still room for improvement in the efficiency of these methods, especially at the sample preparation stage, this review shows the directions that need to be taken to make these methods faster, more efficient and more environmentally friendly.

Advances in Our Understanding of the Mechanism of Action of Drugs (including Traditional Chinese Medicines) for the Intervention and Treatment of Osteoporosis

Osteoporosis (OP) is known as a silent disease in which the loss of bone mass and bone density does not cause obvious symptoms, resulting in insufficient treatment and preventive measures. The losses of bone mass and bone density become more severe over time and an only small percentage of patients are diagnosed when OP-related fractures occur. The high disability and mortality rates of OP-related fractures cause great psychological and physical damage and impose a heavy economic burden on individuals and society. Therefore, early intervention and treatment must be emphasized to achieve the overall goal of reducing the fracture risk. Anti-OP drugs are currently divided into three classes: antiresorptive agents, anabolic agents, and drugs with other mechanisms. In this review, research progress related to common anti-OP drugs in these three classes as well as targeted therapies is summarized to help researchers and clinicians understand their mechanisms of action and to promote pharmacological research and novel drug development.

Nanocarriers for Drug Delivery: An Overview with Emphasis on Vitamin D and K Transportation

Mounting evidence shows that supplementation with vitamin D and K or their analogs induces beneficial effects in various diseases, e.g., osteoarticular, cardiovascular, or carcinogenesis. The use of drugs delivery systems via organic and inorganic nanocarriers increases the bioavailability of vitamins and analogs, enhancing their cellular delivery and effects. The nanotechnology-based dietary supplements and drugs produced by the food and pharmaceutical industries overcome the issues associated with vitamin administration, such as stability, absorption or low bioavailability. Consequently, there is a continuous interest in optimizing the carriers' systems in order to make them more efficient and specific for the targeted tissue. In this pioneer review, we try to circumscribe the most relevant aspects related to nanocarriers for drug delivery, compare different types of nanoparticles for vitamin D and K transportation, and critically address their benefits and disadvantages.

Role of Vitamin K in Intestinal Health

Intestinal diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancer (CRC) generally characterized by clinical symptoms, including malabsorption, intestinal dysfunction, injury, and microbiome imbalance, as well as certain secondary intestinal disease complications, continue to be serious public health problems worldwide. The role of vitamin K (VK) on intestinal health has drawn growing interest in recent years. In addition to its role in blood coagulation and bone health, several investigations continue to explore the role of VK as an emerging novel biological compound with the potential function of improving intestinal health. This study aims to present a thorough review on the bacterial sources, intestinal absorption, uptake of VK, and VK deficiency in patients with intestinal diseases, with emphasis on the effect of VK supplementation on immunity, anti-inflammation, intestinal microbes and its metabolites, antioxidation, and coagulation, and promoting epithelial development. Besides, VK-dependent proteins (VKDPs) are another crucial mechanism for VK to exert a gastroprotection role for their functions of anti-inflammation, immunomodulation, and anti-tumorigenesis. In summary, published studies preliminarily show that VK presents a beneficial effect on intestinal health and may be used as a therapeutic drug to prevent/treat intestinal diseases, but the specific mechanism of VK in intestinal health has yet to be elucidated.

The Role of Depletion of Gut Microbiota in Osteoporosis and Osteoarthritis: A Narrative Review

Osteoporosis and osteoarthritis are common diseases in an aging society, are considered metabolic diseases, and affect the quality of life of older adults. In addition, the gut microbiome is considered an additional organ to regulate bone metabolism. In the past decade, people have been studying the relationship between gut microbiota and bone metabolism. The role and mechanism of the gut microbiota in regulating bone metabolism is very important to improve the development of osteoporosis and osteoarthritis. Depletion of the gut microbiota as a method of studying the role of the gut microbiota was provided strategies to enhance the role of the gut microbiota in regulating osteoporosis and osteoarthritis. In this review, we discuss how depletion of the gut microbiota affects osteoporosis and osteoarthritis.

Oral Calcitriol Use, Vertebral Fractures, and Vitamin K in Hemodialysis Patients: A Cross-Sectional Study

Fractures and vascular calcifications (VCs) are common in patients with chronic kidney disease (CKD). They are related to abnormalities in vitamin D metabolism, calcium, phosphorus, parathyroid hormone, and fibroblast growth factor 23 (FGF23)/Klotho that occur with CKD. Impaired vitamin D metabolism and abnormal levels of calcium, phosphate, parathyroid hormone (PTH), and FGF23/Klotho drive bone and vascular changes in CKD. It is unclear if oral calcitriol safely mitigates fracture risk without increasing the burden of calcifications. Therefore, we investigated whether treatment with calcitriol affected the prevalence of fractures and VC progression in hemodialysis (HD) patients. This report is a secondary analysis of the Vitamin K Italian (VIKI) study, a cross-sectional study involving 387 HD patients. We assessed vitamin 25(OH)D, alkaline phosphatase, PTH, calcium, phosphate, osteocalcin or bone Gla protein, matrix Gla protein, and vitamin K levels. Vertebral fractures (VFs) and VCs were determined by spine radiograph. A reduction of >20% of vertebral body height was considered a VF. VCs were quantified by the length of calcific lesions along the arteries. The patients treated with oral calcitriol were 177 of 387 patients (45.7%). The prevalence of VF was lower in patients receiving oral calcitriol than in those untreated (48.6% versus 61.0%, p = 0.015), whereas the presence of aortic and iliac calcifications was similar (aortic: 81.9% versus 79.5%, respectively, p = 0.552; iliac: 52.0% and 59.5%, respectively, p = 0.167). In multivariable logistic regression analysis, oral calcitriol was associated with a 40.2% reduced odds of fracture (OR 0.598; 95% confidence interval [CI], 0.363-0.985; p = 0.043). In conclusion, we found a significant association between oral calcitriol and lower VF in HD patients without an increase in the burden of VC. Further prospective and interventional studies are needed to confirm these findings. © 2021 American Society for Bone and Mineral Research (ASBMR).

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.

Vitamins, the gut microbiome and gastrointestinal health in humans

The gut microbiome plays important roles in the maintenance of host health and the pathogenesis of many diseases. Diet is a key modulator of the gut microbiome. There is increasing evidence that nutrients other than fermentable fiber affect the gut microbial composition. In this review, we discuss the effects of vitamins on the gut microbiome, and related gastrointestinal health, based on in vitro, animal and human studies. Some vitamins, when provided in large doses or when delivered to the large intestine, have been shown to beneficially modulate the gut microbiome by increasing the abundance of presumed commensals (vitamins A, B₂, D, E, and beta-carotene), increasing or maintaining microbial diversity (vitamins A, B₂, B₃, C, K) and richness (vitamin D), increasing short chain fatty acid production (vitamin C), or increasing the abundance of short chain fatty acid producers (vitamins B₂, E). Others, such as vitamins A and D, modulate the gut immune response or barrier function, thus, indirectly influencing gastrointestinal health or the microbiome. Future research is needed to explore these potential effects and to elucidate the underlying mechanisms and host health benefits.

Vitamin K and cardiovascular complications in CKD patients

Vitamin K, well known for its role in coagulation, encompasses two major subgroups: Vitamin K1 is exclusively synthesized by plants, whereas vitamin K2 mostly originates from bacterial synthesis. Vitamin K serves as a cofactor for the enzyme γ-glutamyl carboxylase, which carboxylates and thereby activates various vitamin K dependent proteins. Several vitamin K-dependent proteins are synthesized in bone but the role of vitamin K for bone health in CKD patients, in particular the prevention of osteoporosis is still not firmly established. Here we focus on another prominent action of vitamin K, in particular vitamin K2, namely the activation of matrix Gla protein (MGP), the most potent inhibitor of cardiovascular calcifications. Multiple observational studies link relative vitamin K deficiency or low intake to cardiovascular calcification progress, morbidity and mortality. Patients with advanced chronic kidney disease (CKD) are particularly vitamin K deficient, in part because of dietary restrictions but possibly also due to impaired endogenous recycling of vitamin K. At the same time this population is characterized by markedly accelerated cardiovascular calcifications and mortality. High dose dietary supplementation with vitamin K2, in particular the most potent form menaquinone-7 (MK7), can potently reduce circulating levels of dephosphorylated uncarboxylated, i.e. inactive MGP in patients with end stage kidney disease. However, despite this compelling data basis, several randomized controlled trials with high dose MK7 supplements in patients with advanced CKD have failed to confirm cardiovascular benefits. Here we discuss potential reasons and solutions for this.

Vitamin K Vitamers Differently Affect Energy Metabolism in IPEC-J2 Cells

The fat-soluble vitamin K (VK) has long been known as a requirement for blood coagulation, but like other vitamins, has been recently recognized to play further physiological roles, particularly in cell development and homeostasis. Vertebrates cannot de novo synthesize VK, which is essential, and it can only be obtained from the diet or by the activity of the gut microbiota. The IPEC-J2 cell line, obtained from porcine small intestine, which shows strong similarities to the human one, represents an excellent functional model to in vitro study the effect of compounds at the intestinal level. The acute VK treatments on the bioenergetic features of IPEC-J2 cells were evaluated by Seahorse XP Agilent technology. VK exists in different structurally related forms (vitamers), all featured by a naphtoquinone moiety, but with distinct effects on IPEC-J2 energy metabolism. The VK1, which has a long hydrocarbon chain, at both concentrations (5 and 10 μM), increases the cellular ATP production due to oxidative phosphorylation (OXPHOS) by 5% and by 30% through glycolysis. The VK2 at 5 μM only stimulates ATP production by OXPHOS. Conversely, 10 μM VK3, which lacks the long side chain, inhibits OXPHOS by 30% and glycolysis by 45%. However, even if IPEC-J2 cells mainly prefer OXPHOS to glycolysis to produce ATP, the OXPHOS/glycolysis ratio significantly decreases in VK1-treated cells, is unaffected by VK2, and only significantly increased by 10 μM VK3. VK1, at the two concentrations tested, does not affect the mitochondrial bioenergetic parameters, while 5 μM VK2 increases and 5 μM VK3 reduces the mitochondrial respiration (i.e., maximal respiration and spare respiratory capacity). Moreover, 10 μM VK3 impairs OXPHOS, as shown by the increase in the proton leak, namely the proton backward entry to the matrix space, thus pointing out mitochondrial toxicity. Furthermore, in the presence of both VK1 and VK2 concentrations, the glycolytic parameters, namely the glycolytic capacity and the glycolytic reserve, are unaltered. In contrast, the inhibition of glycoATP production by VK3 is linked to the 80% inhibition of glycolysis, resulting in a reduced glycolytic capacity and reserve. These data, which demonstrate the VK ability to differently modulate IPEC-J2 cell energy metabolism according to the different structural features of the vitamers, can mirror VK modulatory effects on the cell membrane features and, as a cascade, on the epithelial cell properties and gut functions: balance of salt and water, macromolecule cleavage, detoxification of harmful compounds, and nitrogen recycling.

The Role of Vitamin K in Humans: Implication in Aging and Age-Associated Diseases

As human life expectancy is rising, the incidence of age-associated diseases will also increase. Scientific evidence has revealed that healthy diets, including good fats, vitamins, minerals, or polyphenolics, could have antioxidant and anti-inflammatory activities, with antiaging effects. Recent studies demonstrated that vitamin K is a vital cofactor in activating several proteins, which act against age-related syndromes. Thus, vitamin K can carboxylate osteocalcin (a protein capable of transporting and fixing calcium in bone), activate matrix Gla protein (an inhibitor of vascular calcification and cardiovascular events) and carboxylate Gas6 protein (involved in brain physiology and a cognitive decline and neurodegenerative disease inhibitor). By improving insulin sensitivity, vitamin K lowers diabetes risk. It also exerts antiproliferative, proapoptotic, autophagic effects and has been associated with a reduced risk of cancer. Recent research shows that protein S, another vitamin K-dependent protein, can prevent the cytokine storm observed in COVID-19 cases. The reduced activation of protein S due to the pneumonia-induced vitamin K depletion was correlated with higher thrombogenicity and possibly fatal outcomes in COVID-19 patients. Our review aimed to present the latest scientific evidence about vitamin K and its role in preventing age-associated diseases and/or improving the effectiveness of medical treatments in mature adults ˃50 years old.

Vitamin K in CKD Bone Disorders

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

Menaquinone-7 Supplementation Improves Osteogenesis in Pluripotent Stem Cell Derived Mesenchymal Stem Cells

Development of clinical stem cell interventions are hampered by immature cell progeny under current protocols. Human mesenchymal stem cells (hMSCs) are characterized by their ability to self-renew and differentiate into multiple lineages. Generating hMSCs from pluripotent stem cells (iPSCs) is an attractive avenue for cost-efficient and scalable production of cellular material. In this study we generate mature osteoblasts from iPSCs using a stable expandable MSC intermediate, refining established protocols. We investigated the timeframe and phenotype of cells under osteogenic conditions as well as the effect of menaquinone-7 (MK-7) on differentiation. From day 2 we noted a significant increase in RUNX2 expression under osteogenic conditions with MK-7, as well as decreases in ROS species production, increased cellular migration and changes to dynamics of collagen deposition when compared to differentiated cells that were not treated with MK-7. At day 21 OsteoMK-7 increased alkaline phosphatase activity and collagen deposition, as well as downregulated RUNX2 expression, suggesting to a mature cellular phenotype. Throughout we note no changes to expression of osteocalcin suggesting a non-canonical function of MK-7 in osteoblast differentiation. Together our data provide further mechanistic insight between basic and clinical studies on extrahepatic activity of MK-7. Our findings show that MK-7 promotes osteoblast maturation thereby increasing osteogenic differentiation.

Circulating Carboxylated Osteocalcin Correlates With Skeletal Muscle Mass and Risk of Fall in Postmenopausal Osteoporotic Women

BACKGROUND

Bone and skeletal muscle represent a single functional unit. We cross-sectionally investigated body composition, risk of fall and circulating osteocalcin (OC) isoforms in osteoporotic postmenopausal women to test the hypothesis of an involvement of OC in the bone-muscle crosstalk.

MATERIALS AND METHODS

Twenty-nine non-diabetic, non-obese, postmenopausal osteoporotic women (age 72.4 ± 6.8 years; BMI 23.0 ± 3.3 kg/m²) underwent to: 1) fasting blood sampling for biochemical and hormone assays, including carboxylated (cOC) and uncarboxylated (uOC) osteocalcin; 2) whole-body dual energy X-ray absorptiometry (DXA) to assess total and regional body composition; 3) magnetic resonance imaging to determine cross-sectional muscle area (CSA) and intermuscular adipose tissue (IMAT) of thigh muscles; 4) risk of fall assessment through the OAK system.

RESULTS

Appendicular skeletal muscle index (ASMMI) was low in 45% of patients. Forty percent got a low OAK score, consistent with moderate-severe risk of fall, which was predicted by low legs lean mass and increased total fat mass. Circulating cOC levels showed significantly correlated with βCTx-I, lean mass parameters including IMAT, and OAK score. Fractured and unfractured women did not differ for any of the analyzed parameters, though cOC and uOC positively correlated with legs lean mass, OAK score and bone markers only in fractured women.

CONCLUSIONS

Data supported the relationship between OC and skeletal muscle mass and function in postmenopausal osteoporotic women. Serum cOC, but not uOC, emerges as mediator in the bone-muscle crosstalk. Circulating cOC and uOC levels may be differentially regulated in fractured and unfractured osteoporotic women, suggesting underlying differences in bone metabolism.

Cheung A. Vitamin K and Osteoporosis

Vitamin K acts as a coenzyme of carboxylase, catalyzing the carboxylation of several vitamin K dependent proteins. Beyond its well-known effects on blood coagulation, it also exerts relevant effects on bone and the vascular system. In this review, we point out the relevance of an adequate vitamin K intake to obtain sufficient levels of carboxylated (active form) vitamin K dependent proteins (such as Osteocalcin and matrix Gla protein) to prevent bone health. Another bone-related action of Vitamin K is being a ligand of the nuclear steroid and xenobiotic receptor (SXR). We also discuss the recommended intake, deficiency, and assessment of vitamin K. Furthermore, we review the few available studies that have as pre-specified outcome bone fractures, indicating that we need more clinical studies to confirm that vitamin K is a potential therapeutic agent for bone fractures.