Vitamin K converting enzyme UBIAD1 plays an important role in osteogenesis and chondrogenesis in mice.

Dietary vitamin K1 (phylloquinone: PK) and menaquinone (MK-n) are converted to menadione (MD) in the small intestine and then translocated to various tissues where they are converted to vitamin K2 (menaquinone-4: MK-4) by UbiA prenyltransferase domain containing protein 1 (UBIAD1). MK-4 is effective in bone formation and is used to treat osteoporosis in Japan. UBIAD1 is expressed in bone and osteoblasts and shows conversion to MK-4, but the role of UBIAD1 in osteogenesis is unknown. In this study, we investigated the function of UBIAD1 in osteogenesis using a tamoxifen-dependent UBIAD1-deficient mouse model. When UBIAD1 deficiency was induced from the first week of life, the femur was significantly shortened, and bone mineral density (BMD) was reduced. In addition, the expression of bone and chondrocyte matrix proteins and chondrocyte differentiation factors was significantly decreased. In primary cultured chondrocytes, chondrocyte differentiation was significantly reduced by UBIAD1 deficiency. These results suggest that UBIAD1 is an important factor for the regulation of chondrocyte proliferation and differentiation during osteogenesis.

Phylloquinone is preferable over menadione as a growth factor for Porphyromonas gingivalis.

OBJECTIVES: Porphyromonas gingivalis is the etiological agent of chronic periodontitis. Menadione (vitamin K3) and phylloquinone (vitamin K1) are well-known growth factors for P. gingivalis, while menadione is widely used in growth experiments. Here we attempted to determine the differences in phylloquinone and menadione in P. gingivalis growth experiments, which have not been well studied to date. METHODS: We investigated the effects of menadione and phylloquinone on the growth of two W83 strains and seven ATCC 33277 strains of P. gingivalis. RESULTS: The ATCC 33277 strains grew well with phylloquinone at 2.9 µM in a complex medium (nutrient medium) and at 29 µM in two minimal media. In contrast, the W83 strains grew well without menadione or phylloquinone in three different culture media. Menadione at 2.9 µM, the conventionally used concentration for culturing P. gingivalis, supported the growth of most ATCC 33277 strains but inhibited the growth of some W83 and ATCC 33277 strains. Furthermore, menadione at 14.5 µM frequently inhibited cell growth, while phylloquinone at 145 µM promoted cell growth. CONCLUSIONS: These results indicate that menadione and phylloquinone act as growth factors for ATCC 33277 but that menadione also can inhibit P. gingivalis growth. Thus, we propose that phylloquinone be used instead of menadione in P. gingivalis growth experiments requiring vitamin K.

The additive effect of vitamin K supplementation and bisphosphonate on fracture risk in post-menopausal osteoporosis: a randomised placebo controlled trial.

This study assessed whether vitamin K, given with oral bisphosphonate, calcium and/or vitamin D has an additive effect on fracture risk in post-menopausal women with osteoporosis. No difference in bone density or bone turnover was observed although vitamin K1 supplementation led to a modest effect on parameters of hip geometry. PURPOSE: Some clinical studies have suggested that vitamin K prevents bone loss and may improve fracture risk. The aim was to assess whether vitamin K supplementation has an additive effect on bone mineral density (BMD), hip geometry and bone turnover markers (BTMs) in post-menopausal women with osteoporosis (PMO) and sub-optimum vitamin K status receiving bisphosphonate, calcium and/or vitamin D treatment. METHODS: We conducted a trial in 105 women aged 68.7[12.3] years with PMO and serum vitamin K1 ≤ 0.4 µg/L. They were randomised to 3 treatment arms; vitamin K1 (1 mg/day) arm, vitamin K2 arm (MK-4; 45 mg/day) or placebo for 18 months. They were on oral bisphosphonate and calcium and/or vitamin D. We measured BMD by DXA, hip geometry parameters using hip structural analysis (HSA) software and BTMs. Vitamin K1 or MK-4 supplementation was each compared to placebo. Intention to treat (ITT) and per protocol (PP) analyses were performed. RESULTS: Changes in BMD at the total hip, femoral neck and lumbar spine and BTMs; CTX and P1NP did not differ significantly following either K1 or MK-4 supplementation compared to placebo. Following PP analysis and correction for covariates, there were significant differences in some of the HSA parameters at the intertrochanter (IT) and femoral shaft (FS): IT endocortical diameter (ED) (% change placebo:1.5 [4.1], K1 arm: -1.02 [5.07], p = 0.04), FS subperiosteal/outer diameter (OD) (placebo: 1.78 [5.3], K1 arm: 0.46 [2.23] p = 0.04), FS cross sectional area (CSA) (placebo:1.47 [4.09],K1 arm: -1.02[5.07], p = 0.03). CONCLUSION: The addition of vitamin K1 to oral bisphosphonate with calcium and/or vitamin D treatment in PMO has a modest effect on parameters of hip geometry. Further confirmatory studies are needed. TRIAL REGISTRATION: The study was registered at Clinicaltrial.gov:NCT01232647.

Evaluation of Response to High-Dose Intravenous Vitamin K Administration.

BACKGROUND: Essential to the coagulation pathway, vitamin K (phytonadione) is used to correct clotting factor deficiencies and for reversal of warfarin-induced bleeding. In practice, high-dose intravenous (IV) vitamin K is often used, despite limited evidence supporting repeated dosing. OBJECTIVE: This study sought to characterize differences in responders and nonresponders to high-dose vitamin K to guide dosing strategies. METHODS: This was a case-control study of hospitalized adults who received vitamin K 10 mg IV daily for 3 days. Cases were represented by patients who responded to the first dose of IV vitamin K and controls were nonresponders. The primary outcome was change in international normalized ratio (INR) over time with subsequent vitamin K doses. Secondary outcomes included factors associated with response to vitamin K and incidence of safety events. The Cleveland Clinic Institutional Review Board approved this study. RESULTS: There were 497 patients included, and 182 were responders. Most patients had underlying cirrhosis (91.5%). In responders, the INR decreased from 1.89 at baseline (95% CI = [1.74-2.04]) to 1.40 on day 3 (95% CI = [1.30-1.50]). In nonresponders, the INR decreased from 1.97 (95% CI = [1.83-2.13]) to 1.85 ([1.72-1.99]). Factors associated with response included lower body weight, absence of cirrhosis, and lower bilirubin. There was a low incidence of safety events observed. CONCLUSIONS: In this study of mainly patients with cirrhosis, the overall adjusted decrease in INR over 3 days was 0.3, which may have minimal clinical impact. Additional studies are needed to identify populations who may benefit from repeated daily doses of high-dose IV vitamin K.

Role of Vitamin K in Selected Malignant Neoplasms in Women.

The main function of vitamin K in the human organism is its activity in the blood clotting cascade. Epidemiological studies suggest that reduced intake of vitamin K may contribute to an increased risk of geriatric diseases such as atherosclerosis, dementia, osteoporosis, and osteoarthritis. A growing number of studies also indicate that vitamin K may be involved not only in preventing the development of certain cancers but it may also support classical cancer chemotherapy. This review article summarizes the results of studies on the anticancer effects of vitamin K on selected female malignancies, i.e., breast, cervical, and ovarian cancer, published over the past 20 years. The promising effects of vitamin K on cancer cells observed so far indicate its great potential, but also the need for expansion of our knowledge in this area by conducting extensive research, including clinical trials.

Presence of Phylloquinone in the Intraerythrocytic Stages of Plasmodium falciparum.

Malaria is one of the most widespread parasitic diseases, especially in Africa, Southeast Asia and South America. One of the greatest problems for control of the disease is the emergence of drug resistance, which leads to a need for the development of new antimalarial compounds. The biosynthesis of isoprenoids has been investigated as part of a strategy to identify new targets to obtain new antimalarial drugs. Several isoprenoid quinones, including menaquinone-4 (MK-4/vitamin K2), α- and γ-tocopherol and ubiquinone (UQ) homologs UQ-8 and UQ-9, were previously detected in in vitro cultures of Plasmodium falciparum in asexual stages. Herein, we described for the first time the presence of phylloquinone (PK/vitamin K1) in P. falciparum and discuss the possible origins of this prenylquinone. While our results in metabolic labeling experiments suggest a biosynthesis of PK prenylation via phytyl pyrophosphate (phytyl-PP) with phytol being phosphorylated, on the other hand, exogenous PK attenuated atovaquone effects on parasitic growth and respiration, showing that this metabolite can be transported from extracellular environment and that the mitochondrial electron transport system (ETS) of P. falciparum is capable to interact with PK. Although the natural role and origin of PK remains elusive, this work highlights the PK importance in plasmodial metabolism and future studies will be important to elucidate in seeking new targets for antimalarial drugs.

Carboxylative efficacy of trans and cis MK7 and comparison with other vitamin K isomers.

Carboxylative enzymes are involved in many pathways and their regulation plays a crucial role in many of these pathways. In particular, γ-glutamylcarboxylase (GGCX) converts glutamate residues (Glu) into γ-carboxyglutamate (Gla) of the vitamin K-dependent proteins (VKDPs) activating them. VKDPs include at least 17 proteins involved in processes such as blood coagulation, blood vessels calcification, and bone mineralization. VKDPs are activated by the reduced form of vitamin K, naturally occurring as vitamin K1 (phylloquinone) and K2 (menaquinones, MKs). Among these, MK7 is the most efficient in terms of bioavailability and biological effect. Similarly to other trans isomers, it is produced by natural fermentation or chemically in both trans and cis. However, the efficacy of the biological effect of the different isomers and the impact on humans are unknown. Our study assessed carboxylative efficacy of trans and cis MK7 and compared it with other vitamin K isomers, evaluating both the expression of residues of carboxylated Gla-protein by western blot analysis and using a cell-free system to determine the GGCX activity by HPLC. Trans MK7H2 showed a higher ability to carboxylate the 70 KDa GLA-protein, previously inhibited in vitro by warfarin treatment. However, cis MK7 also induced a carboxylation activity albeit of a small extent. The data were confirmed chromatographically, in which a slight carboxylative activity of cis MK7H2 was demonstrated, comparable with both K1H2 and oxidized trans MK7 but less than trans MK7H2 . For the first time, a difference of biological activity between cis and trans configuration of menaquinone-7 has been reported.

Vitamin K: A novel cancer chemosensitizer.

Cancer incidences are growing rapidly and causing millions of deaths globally. Cancer treatment is one of the most exigent challenges. Drug resistance is a natural phenomenon and is considered one of the major obstacles in the successful treatment of cancer by chemotherapy. Combination therapy by the amalgamation of various anticancer drugs has suggested modulating tumor response by targeting various signaling pathways in a synergistic or additive manner. Vitamin K is an essential nutrient and has recently been investigated as a potential anticancer agent. The combination of vitamin K analogs, such as vitamins K1, K2, K3, and K5, with other chemotherapeutic drugs have demonstrated a safe, cost-effective, and most efficient way to overcome drug resistance and improved the outcomes of prevailing chemotherapy. Published reports have shown that vitamin K in combination therapy improved the efficacy of clinical drugs by promoting apoptosis and cell cycle arrest and overcoming drug resistance by inhibiting P-glycoprotein. In this review, we discuss the mechanism, cellular targets, and possible ways to develop vitamin K subtypes into effective cancer chemosensitizers. Finally, this review will provide a scientific basis for exploiting vitamin K as a potential agent to improve the efficacy of chemotherapeutic drugs.

Vitamin K2 Holds Promise for Alzheimer's Prevention and Treatment.

Recent studies have highlighted the importance of vitamin K2 (VK2) in human health. However, there have been no clinical studies investigating the role of VK2 in the prevention or treatment of Alzheimer's disease (AD), a debilitating disease for which currently there is no cure. In reviewing basic science research and clinical studies that have connected VK2 to factors involved in AD pathogenesis, we have found a growing body of evidence demonstrating that VK2 has the potential to slow the progression of AD and contribute to its prevention. In our review, we consider the antiapoptotic and antioxidant effects of VK2 and its impact on neuroinflammation, mitochondrial dysfunction, cognition, cardiovascular health, and comorbidities in AD. We also examine the link between dysbiosis and VK2 in the context of the microbiome's role in AD pathogenesis. Our review is the first to consider the physiological roles of VK2 in the context of AD, and, given the recent shift in AD research toward nonpharmacological interventions, our findings emphasize the timeliness and need for clinical studies involving VK2.

Effect of Vitamin K-Mediated PXR Activation on Drug-Metabolizing Gene Expression in Human Intestinal Carcinoma LS180 Cell Line.

The pregnane X receptor (PXR) is the key regulator of our defense mechanism against foreign substances such as drugs, dietary nutrients, or environmental pollutants. Because of increased health consciousness, the use of dietary supplements has gradually increased, and most of them can activate PXR. Therefore, an analysis of the interaction between drugs and nutrients is important because altered levels of drug-metabolizing enzymes or transporters can remarkably affect the efficiency of a co-administered drug. In the present study, we analyzed the effect of vitamin K-mediated PXR activation on drug metabolism-related gene expression in intestine-derived LS180 cells via gene expression studies and western blotting analyses. We demonstrated that menaquinone 4 (MK-4), along with other vitamin Ks, including vitamin K1, has the potential to induce MDR1 and CYP3A4 gene expression. We showed that PXR knockdown reversed MK-4-mediated stimulation of these genes, indicating the involvement of PXR in this effect. In addition, we showed that the expression of MDR1 and CYP3A4 genes increased synergistically after 24 h of rifampicin and MK-4 co-treatment. Our study thus elucidates the importance of drug-nutrient interaction mediated via PXR.

Molecular mechanism of antimutagenicity by an ethoxy-substituted phylloquinone (vitamin K1 derivative) from spinach (Spinacea oleracea L.).

In our previous study, an antimutagenic compound from spinach (Spinacea oleracea L.), ethoxy-substituted phylloquinone (ESP) was isolated and characterized. The current study deals with elucidation of the possible mechanism of antimutagenicity of ESP against ethyl methanesulfonate (EMS) deploying model systems such as human lymphoblast (TK+/- or TK6) cell line (thymidine kinase gene mutation assay) and Escherichia coli MG1655 (rifampicin resistance assay). Findings of the study ruled out the possibility of direct inactivation of EMS by ESP. DAPI competitive binding assay indicated the DNA minor groove binding activity of ESP. Interestingly, ESP did not display major groove binding or intercalating abilities. Further, proteomics study using 2-D gel electrophoresis in E. coli and subsequent studies involving single gene knockout strains revealed the possible role of tnaA (tryptophanase) and dgcP (diguanylate cyclase) genes in observed antimutagenicity. These genes have been reported to be involved in indole and cyclic-di-GMP biosynthesis, respectively, which eventually lead to cell division inhibition. In case of TK+/- cell line system, ADCY genes (adenylate cyclase), a functional analogue of dgcP gene, were found to be transcriptionally up-regulated. The generation/doubling time were significantly higher in E. coli or TK+/- cells treated with ESP than control cells. The findings indicated inhibition of cell proliferation by ESP through gene regulation as a possible mechanism of antimutagenicity across the biological system. Cell division inhibition actually provides additional time for the repair of damaged DNA leading to antimutagenicity.

Vitamin K Analogs Influence the Growth and Virulence Potential of Enterohemorrhagic Escherichia coli.

Enterohemorrhagic Escherichia coli (EHEC) causes serious foodborne disease worldwide. It produces the very potent Shiga toxin 2 (Stx2). The Stx2-encoding genes are located on a prophage, and production of the toxin is linked to the synthesis of Stx phages. There is, currently, no good treatment for EHEC infections, as antibiotics may trigger lytic cycle activation of the phages and increased Stx production. This study addresses how four analogs of vitamin K, phylloquinone (K1), menaquinone (K2), menadione (K3), and menadione sodium bisulfite (MSB), influence growth, Stx2-converting phage synthesis, and Stx2 production by the EHEC O157:H7 strain EDL933. Menadione and MSB conferred a concentration-dependent negative effect on bacterial growth, while phylloquinone or menaquinone had little and no effect on bacterial growth, respectively. All four vitamin K analogs affected Stx2 phage production negatively in uninduced cultures and in cultures induced with either hydrogen peroxide (H2O2), ciprofloxacin, or mitomycin C. Menadione and MSB reduced Stx2 production in cultures induced with either H2O2 or ciprofloxacin. MSB also had a negative effect on Stx2 production in two other EHEC isolates tested. Phylloquinone and menaquinone had, on the other hand, variable and concentration-dependent effects on Stx2 production. MSB, which conferred the strongest inhibitory effect on both Stx2 phage and Stx2 production, improved the growth of EHEC in the presence of H2O2 and ciprofloxacin, which could be explained by the reduced uptake of ciprofloxacin into the bacterial cell. Together, the data suggest that vitamin K analogs have a growth- and potential virulence-reducing effect on EHEC, which could be of therapeutic interest.IMPORTANCE Enterohemorrhagic E. coli (EHEC) can cause serious illness and deaths in humans by producing toxins that can severely damage our intestines and kidneys. There is currently no optimal treatment for EHEC infections, as antibiotics can worsen disease development. Consequently, the need for new treatment options is urgent. Environmental factors in our intestines can affect the virulence of EHEC and help our bodies fight EHEC infections. The ruminant intestine, the main reservoir for EHEC, contains high levels of vitamin K, but the levels are variable in humans. This study shows that vitamin K analogs can inhibit the growth of EHEC and/or production of its main virulence factor, the Shiga toxin. They may also inhibit the spreading of the Shiga toxin encoding bacteriophage. Our findings indicate that vitamin K analogs have the potential to suppress the development of serious disease caused by EHEC.

Experimental Model of Subclinical Vitamin K Deficiency.

INTRODUCTION: Vitamin K (VK) is a co-factor in the post-translational gamma glutamic carboxylation of Gla-proteins. VK-dependent coagulation factors are carboxylated in the liver by VK1. Osteocalcin and Matrix-Gla protein (MGP) are carboxylated in extrahepatic tissues by VK2. A model of VK deficiency would be suitable for studying extrahepatic Gla-proteins provided that severe bleeding is prevented. AIM: The aim of this work was to adapt an established protocol of vascular calcification by warfarin-induced inactivation of MGP as a calcification inhibitor, in an attempt to create a broader state of subclinical VK deficiency and to verify its safety. MATERIALS AND METHODS: Two consecutive experiments, each lasting 4 weeks, were required to modify the dosing schedule of warfa-rin and VK1 and to adapt it to the Wistar rats used. The original high doses of warfarin used initially had to be halved and the protective dose of VK1 to be doubled, in order to avoid treatment-induced hemorrhagic deaths. The second experiment aimed to confirm the efficacy and safety of the modified doses. To verify the VK deficiency, blood vessels were examined histologically for calcium deposits and serum osteocalcin levels were mea-sured. RESULTS: The original dosing schedule induced VK deficiency, manifested by arterial calcifications and dramatic changes in carboxyl-ated and uncarboxylated osteocalcin. The modified dosing regimen caused similar vascular calcification and no bleeding. CONCLUSION: The modified protocol of carefully balanced warfarin and VK1 doses is an effective and safe way to induce subclinical VK deficiency that can be implemented to investigate VK-dependent proteins like osteocalcin.

Cytotoxic effects of vitamins K1, K2, and K3 against human T lymphoblastoid leukemia cells through apoptosis induction and cell cycle arrest.

The present study was undertaken to evaluate cytotoxic effects of vitamin K1 (phylloquinone), vitamin K2 (menaquinones), and vitamin K3 (menadione) against human T lymphoblastoid leukemia cells, Jurkat T cells, MOLT-4 cells, and P-glycoprotein-expressing multidrug-resistant MOLT-4/DNR cells. Vitamins K2 and K3, but not vitamin K1, reduced viabilities of Jurkat, MOLT-4, and MOLT-4/DNR cells. The influence potency of vitamin K3 was larger than that of vitamin K2 in all of the three cell lines. MOLT-4/DNR cells seemed to be more sensitive toward the effects of vitamins K2 and K3. The cytotoxicity of vitamins K2 and K3 on these leukemia cells seems to be related to apoptosis induction and cell cycle arrest. Vitamin K2 and K3 treatment induced cleavage of PARP obviously. Moreover, vitamins K2 and K3 specifically down-regulated the expressions of cyclin A2 in all of the three cell lines. However, the effects of vitamins K2 and K3 on the cell cycle profiling in Jurkat, MOLT-4, and MOLT-4/DNR cells varied with the cell type. Vitamins K2 and K3 also decreased the viability of mitogen-activated human peripheral blood mononuclear cells. Our observations suggest that vitamins K2 and K3 have bilateral cytotoxic effects on activated human peripheral lymphocytes and the human leukemic T cells.

MK-7 and Its Effects on Bone Quality and Strength.

Vitamin K acts as a cofactor and is required for post-translational γ-carboxylation of vitamin K-dependent proteins (VKDP). The current recommended daily intake (RDI) of vitamin K in most countries has been established based on normal coagulation requirements. Vitamin K1 and menaquinone (MK)-4 has been shown to decrease osteocalcin (OC) γ-carboxylation at RDI levels. Among the several vitamin K homologs, only MK-7 (vitamin K2) can promote γ-carboxylation of extrahepatic VKDPs, OC, and the matrix Gla protein at a nutritional dose around RDI. MK-7 has higher efficacy due to its higher bioavailability and longer half-life than other vitamin K homologs. As vitamin K1, MK-4, and MK-7 have distinct bioactivities, their RDIs should be established based on their relative activities. MK-7 increases bone mineral density and promotes bone quality and strength. Collagen production, and thus, bone quality may be affected by MK-7 or MK-4 converted from MK-7. In this review, we comprehensively discuss the various properties of MK-7.

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.

Vitamin K1 As A Potential Molecule For Reducing Single-Walled Carbon Nanotubes-Stimulated α-Synuclein Structural Changes And Cytotoxicity.

AIMS: Different kinds of vitamins can be used as promising candidates to mitigate the structural changes of proteins and associated cytotoxicity stimulated by NPs. Therefore, the structural changes of α-syn molecules and their associated cytotoxicity in the presence of SWCNTs either alone or co-incubated with vitamin K1 were studied by spectroscopic, bioinformatical, and cellular assays. METHODS: Intrinsic and ThT fluorescence, CD, and Congo red absorption spectroscopic approaches as well as TEM investigation, molecular docking, and molecular dynamics were used to explore the protective effect of vitamin K1 on the structural changes of α-syn induced by SWCNTs. The cytotoxicity of α-syn/SWCNTs co-incubated with vitamin K1 against SH-SY5Y cells was also carried out by MTT, LDH, and caspase-3 assays. RESULTS: Fluorescence spectroscopy showed that vitamin K1 has a significant effect in reducing SWCNT-induced fluorescence quenching and aggregation of α- syn. CD, Congo red adsorption, and TEM investigations determined that co-incubation of α- syn with vitamin K1 inhibited the propensity of α-syn into the structural changes and amorphous aggregation in the presence of SWCNT. Docking studies determined the occupation of preferred docked site of SWCNT by vitamin K1 on α- syn conformation. A molecular dynamics study also showed that vitamin K1 reduced the structural changes of α- syn induced by SWCNT. Cellular data exhibited that the cytotoxicity of α- syn co-incubated with vitamin K1 in the presence of SWCNTs is less than the outcomes obtained in the absence of the vitamin K1. CONCLUSION: It may be concluded that vitamin K1 decreases the propensity of α- syn aggregation in the presence of SWCNTs and induction of cytotoxicity.

Vitamin K1 prevents diabetic cataract by inhibiting lens aldose reductase 2 (ALR2) activity.

This study investigated the potential of vitamin K1 as a novel lens aldose reductase inhibitor in a streptozotocin-induced diabetic cataract model. A single, intraperitoneal injection of streptozotocin (STZ) (35 mg/kg) resulted in hyperglycemia, activation of lens aldose reductase 2 (ALR2) and accumulation of sorbitol in eye lens which could have contributed to diabetic cataract formation. However, when diabetic rats were treated with vitamin K1 (5 mg/kg, sc, twice a week) it resulted in lowering of blood glucose and inhibition of lens aldose reductase activity because of which there was a corresponding decrease in lens sorbitol accumulation. These results suggest that vitamin K1 is a potent inhibitor of lens aldose reductase enzyme and we made an attempt to understand the nature of this inhibition using crude lens homogenate as well as recombinant human aldose reductase enzyme. Our results from protein docking and spectrofluorimetric analyses clearly show that vitamin K1 is a potent inhibitor of ALR2 and this inhibition is primarily mediated by the blockage of DL-glyceraldehyde binding to ALR2. At the same time docking also suggests that vitamin K1 overlaps at the NADPH binding site of ALR2, which probably shows that vitamin K1 could possibly bind both these sites in the enzyme. Another deduction that we can derive from the experiments performed with pure protein is that ALR2 has three levels of affinity, first for NADPH, second for vitamin K1 and third for the substrate DL-glyceraldehyde. This was evident based on the dose-dependency experiments performed with both NADPH and DL-glyceraldehyde. Overall, our study shows the potential of vitamin K1 as an ALR2 inhibitor which primarily blocks enzyme activity by inhibiting substrate interaction of the enzyme. Further structural studies are needed to fully comprehend the exact nature of binding and inhibition of ALR2 by vitamin K1 that could open up possibilities of its therapeutic application.

Vitamin K1 Inhibition of Renal Crystal Formation through Matrix Gla Protein in the Kidney.

BACKGROUND AND OBJECTIVES: Vitamin K (VK) plays a major role in modifying the binding of calcium in bones and blood vessels. Understanding the effect of VK on crystal formation in the kidney would contribute to advancing the treatment and prevention of kidney stones. METHODS: Rats were treated with vitamin K1 (VK1) for 8 weeks. VK1 levels were detected and crystal formation were observed. HK2 cells were exposed to calcium oxalate monohydrate crystals. Apoptosis and cell viability were detected. Crystal deposition was analyzed using atomic absorption assay. The adenovirus vectors expressing matrix Gla protein (MGP) and siMGP were constructed to elucidate the effect and mechanism of VK1 on crystal formation. MGP expression in vivo and in vitro was analyzed by Western blot. The mRNA levels of monocyte chemoattractant protein-1 (MCP-1) and collagen I was measured by semiquantitative RT-PCR. RESULTS: The concentrations of VK1 in whole blood and kidney tissues rose under treatment with VK1. Crystal formation was inhibited from the second to the 6th week, the frequency and quality of crystal formation decreased significantly, and the location of crystal formation was limited to a greater extent in the rats treated by VK1 compared to the control group. Warfarin treatment in the crystals-exposed HK2 cells significantly increased the number of crystals adhering to cells and the number of apoptotic cells and reduced cell viability. VK1 treatment reversed warfarin's above influence. VK1 inhibited the upregulations of MCP-1 and collagen I in kidney tissues under crystal load. VK1 treatment increased MGP expression in vivo and in vitro, and MGP is necessary for VK1 to play a role in crystal deposition in cells. CONCLUSIONS: VK1 treatment can inhibit the formation of renal crystals in vivo. VK1 increases MGP expression and functions through MGP to reduce crystal deposition in cells and provide cell protection. Our findings suggest that VK1 treatment could be a potential strategy for the treatment and prevention of nephrolithiasis.

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.