A deficiency disease in chicks resembling scurvy

Vitamin K: New insights related to senescence and cancer metastasis

Several clinical trials and experimental studies have recently shown that vitamin K (VK) supplementation benefits the human body. Specifically, VK participates in coagulation and is associated with cellular senescence and cancer. VK has a potential anticancer effect in various cancers, such as pancreatic and prostate cancers. Through anti-inflammatory and antioxidant effects, VK can prevent senescence and inhibit cancer metastasis. Therefore, cancer prognosis can be improved by preventing cellular senescence. In addition, VK can inhibit the proliferation, growth, and differentiation of cancer cells through various mechanisms, including induction of c-myc and c-fos genes, regulation of B-cell lymphoma-2 (Bcl-2) and p21 genes, and angiogenesis inhibition. This review aims to discuss the relationship among VK, cellular senescence, and cancer metastasis and thus may improve comprehension of the specific functions of VK in human health. The potential application of VK as an adjuvant therapy for cancer (or in combination with traditional chemotherapy drugs or other vitamins) has also been highlighted.

Dietary Vitamin K Intake and HPV-Infection Status Among American Women: A Secondary Analysis From National Health and Nutrition Examination Survey Data From 2003 to 2016

Objective: Cervical cancer is a serious potential risk to women’s health, and is closely related to persistent HPV infection. Vitamin K mainly existed in green vegetables, fruit, and dairy products. This research aims to observe the association between vitamin K and HPV-infection.

Methods: 13,447 participants from the NHANES were selected. Dietary vitamin K intake was used as the objective independent variable and continuous variable, HPV-infection status was used as the outcome variable, and characteristics of selected participants were used as the covariates.

Results: There was a nonlinearity between vitamin K intake and HPV-infection, and the inflection point is 3.81 of log2 vitamin K intake. In a range of 0–3.81, Each one-unit increase in log2 vitamin K intake was associated with a 43% reduction in the risk of HPV infection. When log2 vitamin K intake excess of 3.81, the risk of HPV infection did not continue to decline. The HPV-subtype was not associated with vitamin K intake.

Conclusion: There is a nonlinearity between vitamin K intake and HPV-infection status. But HPV-subtype was not associated with vitamin K intake.

Potential Beneficial Effects of Vitamin K in SARS-CoV-2 Induced Vascular Disease?

Prevalent coagulopathy and thromboembolism are observed in severe COVID-19 patients with 40% of COVID-19 mortality being associated with cardiovascular complications. Abnormal coagulation parameters are related to poor prognosis in COVID-19 patients. Victims also displayed presence of extensive thrombosis in infected lungs. Vitamin K is well-known to play an essential role in the coagulation system. Latest study revealed an existing correlation between vitamin K deficiency and COVID-19 severity, highlighting a role of vitamin K, probably via coagulation modulation. In agreement, other recent studies also indicated that anti-coagulant treatments can reduce mortality in severe cases. Altogether, potential mechanisms linking COVID-19 with coagulopathy in which vitamin K may exert its modulating role in coagulation related with disease pathogenesis are established. In this review, we discuss the recent evidence supporting COVID-19 as a vascular disease and explore the potential benefits of using vitamin K against COVID-19 to improve disease outcomes.

Vitamin K: Redox-modulation, prevention of mitochondrial dysfunction and anticancer effect

This review is directed to the redox-modulating properties and anticancer effect of vitamin K. The concept is focused on two aspects: (i) redox-cycle of vitamin K and its effect on the calcium homeostasis, “oncogenic” and “onco-suppressive” reactive oxygen species and the specific induction of oxidative stress in cancer; (ii) vitamin K plus C as a powerful redox-system, which forms a bypass between mitochondrial complexes II and III and thus prevents mitochondrial dysfunction, restores oxidative phosphorylation and aerobic glycolysis, modulates the redox-state of endogenous redox-pairs, eliminates the hypoxic environment of cancer cells and induces cell death. The analyzed data suggest that vitamin C&K can sensitize cancer cells to conventional chemotherapy, which allows achievement of a lower effective dose of the drug and minimizing the harmful side-effects. The review is intended for a wide audience of readers - from students to specialists in the field.

Vitamin K2 inhibits rat vascular smooth muscle cell calcification by restoring the Gas6/Axl/Akt anti-apoptotic pathway

Vascular calcification is associated with cardiovascular disease as a complication of hypertension, hyperlipidemia, diabetes mellitus, and chronic kidney disease. Vitamin K2 (VK2) delays vascular calcification by an unclear mechanism. Moreover, apoptosis modulates vascular smooth muscle cell (VSMC) calcification. This paper aimed to study VK2-modified VSMC calcification and survival cell signaling mediated by growth arrest-specific gene 6 (Gas6) and its tyrosine kinase receptor Axl. Primary-cultured VSMCs were dose-dependently treated with VK2 in the presence of calcification medium for 8 days, or pre-treated for 1 h with/without the Axl inhibitor R428 (2 μmol/L) or the caspase inhibitor Z-VAD-fmk (20 μmol/L) followed by treatment with VK2 (10 μmol/L) or rmGas6 (200 nmol/L) in calcification medium for 8 days. Calcium deposition was determined by the o-cresolphthalein complexone assay and Alizarin Red S staining. Apoptosis was determined by TUNEL and flow cytometry using Annexin V-FITC and propidium iodide staining. Western blotting detected the expressions of Axl, Gas6, p-Akt, Akt, and Bcl2. VK2 significantly inhibited CaCl₂- and β-sodium glycerophosphate (β-GP)-induced VSMC calcification and apoptosis, which was dependent on restored Gas6 expression and activated downstream signaling by Axl, p-Akt, and Bcl2. Z-VAD-fmk significantly inhibited CaCl₂- and β-GP-induced VSMC calcification and apoptosis. Augmented recombinant mouse Gas6 protein (rmGas6) expression significantly reduced VSMC calcification and apoptosis. Furthermore, the Gas6/Axl interaction was inhibited by R428, which abolished the preventive effect of VK2 on CaCl₂- and β-GP-induced apoptosis and calcification. These results suggest that Gas6 is critical in VK2-mediated functions that attenuate CaCl₂- and β-GP-induced VSMC calcification by blocking apoptosis.

Warfarin and vitamin K compete for binding to Phe55 in human VKOR

Vitamin K epoxide reductase (VKOR) catalyzes the reduction of vitamin K quinone and vitamin K 2,3-epoxide, a process essential to sustain γ-carboxylation of vitamin K-dependent proteins. VKOR is also a therapeutic target of warfarin, a treatment for thrombotic disorders. However, the structural and functional basis of vitamin K reduction and the antagonism of warfarin inhibition remain elusive. Here, we identified putative binding sites of both K vitamers and warfarin on human VKOR. The predicted warfarin-binding site was verified by shifted dose-response curves of specified mutated residues. We used CRISPR-Cas9-engineered HEK 293T cells to assess the vitamin K quinone and vitamin K 2,3-epoxide reductase activities of VKOR variants to characterize the vitamin K naphthoquinone head- and isoprenoid side chain-binding regions. Our results challenge the prevailing concept of noncompetitive warfarin inhibition because K vitamers and warfarin share binding sites on VKOR that include Phe55, a key residue binding either the substrate or inhibitor.

Some Important Milestones in the Field of Blood Clotting

Several different kinds of 'milestone' in the field of blood coagulation are described from the middle decades of the 20th century. Although viewed from the standpoint of clotting per se, attention is also given to implications for innate immunity. The first milestone considered is the protracted saga of clotting dependence on vitamin K, an adventure that spanned more than five decades beginning in the 1920s. The second has to do with the discovery of a half-dozen 'new' clotting factors during the period immediately following World War II. A third pursues a narrower focus and examines the once mysterious transformation of fibrinogen into fibrin. Finally, the clinical treatment of classical hemophilia had a remarkable turning point in the 1960s as the result of simple but sensible measures.

Vitamin k dependent proteins and the role of vitamin k2 in the modulation of vascular calcification: a review

Vascular calcification, a cause of cardiovascular morbidity and mortality, is an actively regulated process involving vitamin K dependent proteins (VKDPs) among others. Vitamin K is an essential micronutrient, present in plants and animal fermented products that plays an important role as a cofactor for the post-translational γ-carboxylation of glutamic acid residues in a number of proteins. These VKDPs require carboxylation to become biologically active, and they have been identified as having an active role in vascular cell migration, angiogenesis and vascular calcification. This paper will review the process of vascular calcification and delineate the role that vitamin K2 plays in the modulation of that process, through the activation of VKDPs. One such VKDP is Matrix Gla Protein (MGP), which when activated inhibits osteogenic factors, thereby inhibiting vascular and soft tissue calcification.

Relationship between acquired deficiency of vitamin K-dependent clotting factors and hemorrhage

This study examined the changes of activities of vitamin K-dependent clotting factors (VKDCF) under various pathological conditions and explored the relationship between acquired deficiency of VKDCFs and hemorrhage. Clinical data of 35 patients who were diagnosed as having acquired deficiency of VKDCF were retrospectively analyzed. Coagulation factors involved in the intrinsic and extrinsic pathways were detected in these patients and 41 control subjects. The results showed that the average activities of VKDCFs were decreased in the patients in comparison to the control subjects and significantly increased after treatment of these patients with vitamin K and blood products. Multivariate regression analysis indicated that decreased activity of VKDCF was not an independent risk factor for bleeding disorders owing to deficiency or metabolic disturbance of vitamin K. It was concluded that acquired deficiency of VKDCF occurs under a variety of pathologic conditions and is closely associated with hemorrhagic events. Administration of vitamin K and transfusion of blood products containing high concentrations of VKDCFs helps alleviate the hemorrhagic diseases.

Vitamin K and thrombosis

Vitamin K was discovered in the 1930s during cholesterol metabolism experiments in chickens. It is a fat-soluble vitamin which occurs naturally in plants as phylloquinone (vitamin K1) and is produced by gram-negative bacteria in the human gastrointestinal tract as menaquinone (vitamin K2). This vitamin was found to be essential for normal functioning of hemostasis. In addition, a number of clinical conditions in which vitamin K deficiency was found to be the underlying pathophysiologic problem were discovered. These conditions include hemorrhagic disease of the newborn, obstructive jaundice, and malabsorption syndromes. The importance of this vitamin has become more apparent with the discovery of the anticoagulant warfarin which is a vitamin K antagonist. There are millions of patients on this therapy for a variety of thrombogenic conditions such as atrial fibrillation, deep vein thrombosis, pulmonary embolism, and prosthetic cardiac valves. The wide use of this narrow therapeutic index drug has resulted in significant risk for major bleeding. Vitamin K serves as one of the major reversing agent for patients over-anticoagulated with warfarin. In the past few years, research has focused on new areas of vitamin K metabolism, which include bone and endovascular metabolism; cell growth, regulation, migration, and proliferation; cell survival, apoptosis, phagocytosis, and adhesion. These new areas of research highlight the significance of vitamin K but raise new clinical questions for patients who must be maintained on long-term warfarin therapy.

Vitamin K epoxide reductase complex subunit 1 (VKORC1): the key protein of the vitamin K cycle

Vitamin K epoxide, a by-product of the carboxylation of blood coagulation factors, is reduced to vitamin K by an enzymatic system possessing vitamin K epoxide reductase (VKOR) activity. This system is the target of coumarin-derived drugs widely used in thrombosis therapy and prophylaxis. Recently, the key protein of the VKOR system has been identified. The human VKORC1 gene maps to chromosome 16 and consists of 3 exons encoding a 163-amino acid integral ER membrane protein with three or four predicted transmembrane alpha- helices. Expression of human VKORC1 in Spodoptera frugiperda (Sf9) cells and in Pichia pastoris results in enhanced VKOR activity over low endogenous constitutive levels. Sequence based search methods reveal that human VKORC1 belongs to a large family of homologous genes found in vertebrates, insects, plants, protists, archea, and bacteria. All orthologs share five completely conserved amino acids, including two cysteines found in a tetrapeptide motif presumably required for redox function. The recent discovery of the VKORC1 gene has initiated renewed interest in understanding VKOR activity. Analysis of VKORC1 protein structure and function will be crucial in understanding the VKOR catalytic mechanism, how anticoagulant drugs modulate VKOR activity, and the role of VKORC1 in downstream physiological and pathological pathways.

Vitamin K and energy transduction: a base strength amplification mechanism

Energy transfer provides an arrow in the metabolism of living systems. Direct energetic coupling of chemical transformations, such that the free energy generated in one reaction is channeled to another, is the essence of energy transfer, whereas the purpose is the production of high-energy chemical intermediates. Vitamin K provides a particularly instructive example of energy transfer. A key principle at work in the vitamin K system can be termed "base strength amplification." In the base strength amplification sequence, the free energy of oxygenation of vitamin K hydroquinone (vitamin KH2) is used to transform a weak base to a strong base in order to effect proton removal from selected glutamate (Glu) residues in the blood-clotting proteins.

Post-translational carboxylation of preprothrombin

In summary, in this review on the function of vitamin K in post-translational modification of precursor proteins by carboxylation of certain glutamyl residues, I have tried to cover in particular the recent work on the reaction, the enzymes involved and the mechanisms being considered. In doing this I have also considered vitamin K, its discovery, its functional form and the possible relation of its metabolism to the carboxylation reaction. Equally the various vitamin K-dependent gla-containing proteins currently known have been described. The carboxylation of synthetic small molecule exogenous substrates and the synthesis and metabolism of the products of carboxylation are of great help in studying the reaction. Structural specificity of vitamin K analogs in vivo and in vitro has been compared and the use of various antagonists in vivo and in vitro considered in attempts to gain an understanding of the overall reaction. The reactions subsequent to carboxylation, e.g., the activation of prothrombin to thrombin via serine proteases and the related activation of the other vitamin K-dependent proteins have not been considered in this review. The review has not covered prothrombin or other vitamin K-dependent protein isolation, nor the determination of these proteins. As the vitamin K-dependent protein carboxylation story has developed over the past six years, a number of reviews have been written which help in keeping up with the various aspects of the field as it has expanded. These reviews refer to many of the papers I have had to eliminate due to space limitations. They are referenced as 469-489. The review is in no sense comprehensive and many papers have been missed or only mentioned. I have tried to concentrate on the more recent work and, thus, much of the very fine work of the 1940's on vitamin K chemistry is hardly mentioned. Some redundancy has been built into the organization of the review so that a reader can obtain a reasonable view of any one section without having to search the whole review for all possible relevant information on any particular part of the field.

Hemorrhagic Diathesis Experimentally Induced by Deficiency in Vitamin K: A Histopathologic Study

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VITAMIN K

During the decade following Dam's first observations on the hemorrhagic syndrome the combined efforts of several groups of investigators have solved many of the important problems connected with the new vitamin. Sources of vitamin K were discovered, methods of extraction and purification devised, the isolation effected, the structure of K(1) worked out and then verified by synthesis, and a promising start made on the therapeutic applications. In addition, simple water soluble compounds with antihemorrhagic properties have been supplied for clinical work. Preliminary results with these compounds are encouraging.