Published Research – Vitamin K and Cardiac

  • Cardiovascular disease is the leading cause of morbidity and mortality in the western world.
  • Research indicates that vascular calcification is a complex and actively regulated process involving tissue proteins that depend on the presence of vitamin K.
  • This means that it may be possible to modify or reverse the disease process by taking vitamin K.  Premature death is not inevitable.
  • There is a growing line of research highlighting the profound benefits of vitamin K for cardiac health, including protection from heart disease, decreasing calcification, inhibiting calcification from occurring, and reducing the risk of death from heart disease.
  • Subjects who take medications that interfere with vitamin K, can incur the side effect of inducing heart disease.
  • A substantial part of the population have been found to be deficient in vitamin K.
  • More vitamin K is absorbed from a nutritional supplement than from food.

On this page, we present an understanding of the research that has been done on vitamin K and cardiac health.  Cardiovascular disease affects millions of people a year, and either there has been little effective treatment available for it, or the medical treatments have been invasive and surgical in nature, or the treatments have involved prescription medications that often have toxic side effects.  The emerging research on vitamin K and heart health is tremendously exciting, and for once, it seems possible that a person can reverse heart disease.  We review the trends in the research, the emerging understanding of the biochemistry of vitamin K in the body, the understanding of how a lack of vitamin K contributes to the process of heart disease, and how supplementing with vitamin K can restore health to your heart arteries and to your cardiovascular system in general.  If you’d like to learn more, then read on.  If you’d like to make a purchase of Koncentrated K, then click on Buy Now.

Cardiovascular Disease

Cardiovascular disease is the leading cause of morbidity and mortality in the western world and atherosclerosis is the major common underlying disease.   Atherosclerosis is a disease in which plaque forms and builds up in the walls of the arteries.  The disease process of atherosclerosis begins with a vascular injury.  A vascular injury can be either a mechanical “insult”, a chemical “insult”, or a bacterial/viral insult which can take place at any age.  These “insults” or injuries then create a cascade of events which leads to subsequent inflammation (cells growing where they should not) in the arteries resulting in oxidative stress, and then plaque formation, and finally calcification at that site. 

Atherosclerosis is typical in children up to 5 years of age and then disappears.  Atherosclerosis can then reappear as early as the second decade of life and is near-ubiquitous in the population by about 65 years of age (Shanahan, et al.  1998).  The increase in extent and severity of calcification that occurs with increasing age is due to the patient’s harboring and surviving an active, spreading, inflammatory atherosclerosis for a long period of time.  Atherosclerosis can affect any artery in the body, including arteries in the heart, brain, arms, legs, pelvis, neck, and kidneys, and occurs in association with a diverse range of diseases, including diabetes and uremia,  Atherosclerosis is typically a chronic, slowly progressive and cumulative disease (Glass, 2001; Demer & Tintut, 2008). 

Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood.  Over time plaque builds up and narrows or blocks your arteries, which limits the flow of oxygen-rich blood to your organs and other parts of your body.  This is known as ischemia.  Some plaques remain clinically silent and are considered generally stable over the long term.  A stable plaque tends to be asymptomatic, and is rich in extracellular matrix and smooth muscle cells.  The other plaques are unstable, and research has shown them to be rich in macrophages and foam cells with the extracellular matrix being weak and prone to rupture (Davies, 1990; Davies, 1996; Huang et al, 2001; Finn et al.  2010), as it can become brittle and calcify (Aikawa, et al., 2007; Alexopolous & Raggi 2009).  The calcification decreases vessel elasticity and increases shear stress at the interface between calcified deposits and soft tissue (Wayhs et al, 2002; Spadaro et al., 2000; Keelan et al., 2001; Sangiori 1998; Vliegenthart et al, 2005), forming an aneurysm which can rupture (Derlin et al.  2011; Vengrenyuk et al., 2008; Rennenberg et al, 2009).  Ruptures expose blood clots to the circulation that will rapidly slow or stop blood flow, leading to death of the tissues fed by the artery in approximately five minutes.  This catastrophic event is called an infarction.  A common scenario is a clot in the coronary artery, causing a myocardial infarction or heart attack.  This same process in an artery to the brain is commonly called a stroke (Ehara et al., 2004). 
 

Cardiovascular Disease:  The Vascular-Bone Axis  

Vascular calcification was previously viewed as an inevitable, passive, and degenerative process leading to mineral deposits accumulating in the vasculature that occurred at the end stages of atherosclerosis and was regarded as a disease of the aged (Schinke and Karsenty, 2000; Demer and Tintut, 2008).  This opinion has changed and it is now understood that vascular calcification is a complex and actively regulated process involving vascular cells and a number of vitamin K dependent proteins, and sharing many features with osteogenesis or bone formation (Shanahan, et al. 2000; Bostrom, 2000; Campbell and Campbell, 2000; Canfield, et al.  2000; Mody et al. 2003; Doherty et al, 2003).  Research indicates that MGP and osteopontin, both bone associated proteins, are highly expressed in human atheromatous plaques (Shanahan, et al, 1994; O’Brien et al, 1995; Shanahan et al, 1998; Dhore et al, 2001; Viegas et al., 2009), with the highest levels of MGP being found in the lipid rich areas of the plaque. 

Research on vascular calcification has accelerated dramatically in the past decade, and diverse and highly regulated molecular signaling cascades controlling vascular calcification have been described.  Current research involves efforts to define the complex interactions between cellular and molecular mediators of arterial calcification and the role of endogenous calcification inhibitors.  (Belovici and Pandele, 2008).  The research has highlighted that Vitamin K dependent proteins play an essential role in vascular calcification (Zak-Golab, 2011).  Local and circulating molecules such as osteopontin, osteoprogerin, leptin and matrix Gla protein were identified as critical regulators of vascular calcification, and they all are dependent on vitamin K to be activated and utilized (Mazzini, et al, 2006).  
 

Cardiovascular Disease and Vitamin K Dependent Proteins

Several vitamin K dependent proteins (VKDP) have been identified as involved in the regulation of calcification and vascular calcium metabolism, including osteocalcin, gla rich protein and matrix Gla protein (Viegas et al, 2014; Willem et al. 2014).  Among these proteins, the vitamin K dependent matrix Gla-protein (MGP) plays a dominant role (Schurgers et al. 2008).  Matrix Gla protein is a small vitamin K-dependent protein containing five gamma-carboxyglutamic acid (Gla) residues that are believed to be important in binding Ca (2+) calcium crystals and bone morphogenetic protein (Srivatsa  et al 1997; Luo, et al, 1997; Shanahan, et al, 1998; Price, et al. 1985).  A bone morphogenetic protein refers to the proteins that generate the formation and structure of bone.  

Matrix Gla protein is expressed predominantly by vascular smooth muscle cells (VSMCs stands for vascular smooth muscle cells) and by chrondrocytes (cartilage cells), and is the most important inhibitor of arterial mineralization currently known.  MGP is synthesized in many soft tissues with the highest levels of expression in the heart, lung, kidney and cartilage (Fraser and Price, 1980).  Animal models showed that MGP is a strong inhibitor of calcification of arterial vessel wall and cartilage, whereas genetically engineered mice without MGP exhibited a severe and rapid calcification leading to premature death due to spontaneous aortic rupture (Luo et al., 1997; Murshed et al., 2004).  MGP species in both tissues and the circulation have been detected in the healthy population and significant differences were found in patients with cardiovascular disease (Cranenburg, et al, 2008;  Schurgers, et al., 2005; Jia et al, 2012).  In arteries, MGP acts as a local inhibitor of media calcification (Price, et al, 1998; Murshed et al, 2004; Schurgers et el, 2007; Yao et al, 2010). 

Advances in measurement have allowed the amount of circulating total uncarboxylated matrix Gla protein to be measured and it is associated with the extent of prevalent arterial calcification (Cranenburg et al, 2010; Theuweissen, et al, 2012; Rennenberger, et al, 2010).  High artery calcium scores are associated with increased cardiovascular events, and research shows that a high calcium score and a high osteocalcin ration (OCR)-reflecting low vitamin K status–is associated with ucMGP in the blood (Nasir et al., 2010).  In other words, people who have high calcium scores also tend to have uncarboxylated matrix Gla protein in their blood, meaning they are deficient in vitamin K.

The precise molecular mechanism underlying the function of MGP is not yet fully understood, but seems to involve the inhibition of bone morphogenetic protein 2 and 4 (BMP-2 and-4) (Zebboudj, et. al., 2002; Yao et. al., 2006;  Nakagawa, et. al., 2010; Ikeda, et. al., 2012; ), the suppression of osteochondrogenic transdifferentiation of vascular smooth muscle cells (Speer, et. al., 2009) so they don’t transform into cartilage in blood vessels (El Maadawy, et. al., 2003; Naik, 2012) and the direct inhibition of calcium-crystal growth (Schurgers et. al., 2007; O’Young et. al., 2011).  Bone morphogenetic protein-2 is a principal osteogenic growth factor.  Lack of vitamin K and hence carboxylated MGP leads those protein cells to transform into cartilage cells in the arteries and blood vessels (El-Maadawy et. al., 2003). 

As matrix Gla protein (MGP) is a vitamin K-dependent protein, it needs an adequate amount of vitamin K available in order to function effectively and inhibit calcium (Schurgers et al, 2008).  Gla containing proteins have glutamic acid residues that must be gamma-carboxylated by vitamin K-dependent gamma-carboxylase to enable them to bind calcium and function normally and effectively.  Specific glutamic acid residues in the protein are changed by an enzyme-mediated reaction to form a modified glutamic acid known as γ-carboxyglutamic acid.  This enzyme reaction, known as γ-carboxylation, or gamma-carboxylation, requires vitamin K for the carboxylation and transformation to take place.  This transformation is required for these proteins to function and bind calcium, which then permits abundant Gla-MGP to be found in the arterial wall, with a subsequent reduction in vascular calcification.   

Without adequate amounts of vitamin K, carboxylation cannot take place.  The proteins, such as MGP, remain uncarboxylated and are not able to inhibit vascular calcium properly.  Uncarboxylated matrix Gla-protein, formed as a result of vitamin K deficiency, is associated with the increased vascular calcification and cardiovascular disease (Hackeng et al 2001; Schurgers et al, 2013) as well as increased risk of arterial stiffness (Piven et al, 2017).

It is now understood that vitamin K dependent proteins play an essential role in vascular calcification (Rajamann, et al, 2003;  Zak-Golab, 2011) and they all are dependent on vitamin K to be activated and utilized (Mazzini & Schulze, 2006).   There is increasing experimental and clinical evidence linking vitamin K deficiency to valve and arteriole calcification via a functional impairment of vitamin K–dependent calcification modulators (Krueger,et al, 2009; El Asmar et al, 2014).  The amount of vitamin K in the diet has been correlated as a significant variable in death from cardiovascular disease in 168 countires (Cundiff & Aqutter, 2016).
 

Cardiovascular Disease and Vitamin K Antagonists

Many of the forces that induce arterial calcification may act by disrupting the essential post-translational modification of Matrix Gla Protein (MGP), allowing Bone Morphogenic Protein-2 (BMP-2) to induce mineralization.  Vitamin K deficiency, as well as drugs that act as vitamin K antagonists, and oxidant stress are forces that could prevent the formation of GLA residues on MGP.  Vitamin K antagonists (VKA), warfarin, are the most frequently prescribed drugs to control blood coagulation, and clotting of patients with thrombosis and patients at risk of thromboembolic events.  A widely prescribed vitamin K antagonist is coumadin.  Common inconvenient effects of VKA include unpredictable pharmacokinetics and pharmacodynamics, drug and food interactions, slow onset and offset of action, considerable inter-individual and intra-individual variability in dose response and a narrow therapeutic window.  In addition, frequent laboratory monitoring and dose adjustments are needed to keep patients within the INR (International Normalized Ratio) target range.  Furthermore, VIKA treatment inhibits the carboxylation of MGP, subsequently inhibiting its function and thereby accelerating vascular calcification (Chatrou et al, 2012). 

VKA therapy may have undesired side-effects in addition to the risk of bleeding because a number of proteins outside the coagulation system also require γ-glutamylcarboxylation to become biologically active (Chatrou, et al., 2011; Schurgers et al. 2012) meaning that the therapy aimed to prevent blood clots also disrupts the effectiveness of vitamin K on the proteins that inhibit calcification in the vasculature system and elsewhere in the human body.   Concordantly, clinical studies and case reports revealed that VKA treatment is associated with arterial calcification and upregulation of uncarboxylated MGP (ucMGP) (Price et al, 1994; Schurgers, et al, 2004; Koos et al, 2005; Weijs, et al, 2011; Rennenberg et al, 2010).  Other research showed that in animals, treatment with vitamin K antagonists (VKA) resulted in arterial calcification within two to four weeks.  The administration of high doses of the vitamin K antagonist, warfarin, has been shown to induce rapid calcification of the elastic lamellae in rat arteries and heart valves (Price et al, 1998).   Also, Price demonstrated that rats treated with warfarin doses that specifically inhibited MGP γ-carboxylation showed extensive vascular calcification and accumulation of ucMGP (Price et al 2000;  Kruger et al 2013).  Other animal studies suggest that VKA treatment causes medial calcification similar to Monckeberg’s sclerosis (Spronk etal 2003; Essalihi et al, 2003).  Whereas in humans it has been demonstrated that oral anticoagulant treatment (vitamin K antagonists) is associated with substantially increased heart valve calcification (Schurgers et al, 2004; Chatrou, 2011; Weijs, et al., 2011; Schurgers, et al., 2012; Demer & Bostrom, 2015).  Since administration of vitamin K restores MGP γ-carboxylation and enhances the reversal of warfarin-induced calcification in rats (Schurgers et al, 2007), providing a supplement of vitamin K may become a critical treatment adjunct for people on warfarin, or VKA treatment (Westenfeld, et al., 2008; Homes, et al., 2012; Theuwissen, et al., 2013).  

And recent research found that people taking hypertensives, such as ACE inhibitors, or thiazide diuretics, were significantly more likely to have extreme coronary artery calcification progression, when they had low levels of vitamin K1, as measured in their blood (Shea, et al 2013).  One in five adults in the US are treated for hypertension and about half of adults in the US may have low vitamin K status, leading the researchers to call for additional studies to explore why medicine for high blood pressure is related to coronary artery calcification, when vitamin K intake is low.    

 

Cardiovascular Disease Helped by Vitamin K

The research clearly indicates that adequate amounts of vitamin K can improve cardiovascular disease.  There is a growing line of research highlighting the profound benefits of vitamin K for cardiac health.  In a study of a ten year follow up of 4,500 elderly subjects (the Rotterdam study cohort) Geleijnse demonstrated that vitamin K2 intake is inversely correlated with cardiovascular disease and mortality.  The more vitamin K in a person’s diet, the lower the rate of cardiovascular disease.  In the Rotterdam study, the highest quartile for K2 intake was 45 ug/day (Geleijnse, et al., 2004).  Gast later confirmed the findings from the Rotterdam study with over 16,000 participants in the Prospect study.  In that study, a high intake of vitamin K2, menaquinones, especially MK7, MK8 and MK9 protected against coronary heart disease, and of those, vitamin MK7 turned out to have the most beneficial effects on cardiovascular disease with a mortality risk reduction of 9% for each 10 ug/day of extra intake (Gast, et al., 2009.  Kapen (et al, 2015) showed that supplementing with 180 ug of MK7 over three years significantly improved arterial stiffness, and other vascular measures in healthy, postmenopausal women. Visser et al (2016) showed that high intake of menaquinones was associated with a reduced risk of peripheral artery disease (PAD).  

During the last two decades it has been clear that vitamin K is needed for other physiological processes than blood clotting, and that it plays an important role in inhibiting vascular calcification.  It seems however, that our dietary vitamin K intake is too low to support the carboxylation of at least some of the Gla Proteins.  Unfortunately for most of the western population, our vitamin K intake from our diet is too low and the vitamin K requirement of the vascular system is not met, meaning that vitamin K supplements are required for optimal vascular health. 

According to the triage theory, when diet is poor, vitamins are preferentially utilized for immediate survival.  In a healthy population, clotting factors are the first order of survival and vitamins are preferentially utilized for clotting first, with other bodily needs being deferred.  When vitamin K is amply available, either through diet or nutritional supplements, those other body and health needs can be met.  This means that long-term vitamin K inadequacy is a modifiable risk factor for the development of degenerative diseases including atheroslcerosis, osteoporosis, and cancer (Vermeer and Theuwissen, 2011; Vermeer, 2012). 

One can take vitamin K and reduce the chances of heart disease.  And one can take large amounts of vitamin K at a therapeutic dosage level and reduce the chances of heart disease without any identified health risk.  In other words, vitamin K is absorbed readily and easily by the body, without the risk from the medications often prescribed for heart disease, and without the risk of the surgeries often performed as an intervention for heart disease.  And at the same time, the vitamin K you take in the form of Koncentrated K can help ward off other disease processes that are linked to vitamin K deficiency.

The research cited below explores the link between forms of vitamin K and cardiovascular health.  The research presents some of the key discoveries over the past decades, the changing understanding of the process of heart disease, and the growing awareness of the vascular-bone axis and the role of vitamin K in managing calcium within the body (Brandenburg et al 2015).  It is exciting stuff and it is thrilling to consider how much vitamin K can change your life!


 

1930s

Dam, H. The antihaemorrhagic vitamin of the chick:  Occurrence and chemical nature.  Nature.  1935;135(3417):652-653.


1970s

Nelsestuen, GL, and Suttie, JW.  The purification and properties of an abnormal prothrombin protein produced by dicumarol-treated cows:  A comparison to normal prothrombin.  J. Biol. Chem.  1972; 247:8176-82.

Esmon, CT, Sadowski, JA, and Suttie, JW.  1975.  A new carboxylation reaction.  The vitamin K-dependent incorporation of H14Co3 into prothrombin.  J Biol. Chem.  1975;250:4744-48.  
Early on there was little information about the functional role of vitamin K or its mechanism of action.  This early research elucidated the role of vitamin K as a cofactor in glutamate carboxylation in prothrombin. 

Esmon, CT and Suttie, JW.  Vitamin K-dependent carboxylase.  Solubilization and properties.  J. Biol. Chem.  1976;251:6238-43.

 

1980s

Levy RJ, Lian JB, Gallop PM.  Ý-carboxyglutamic acid and atherosclerotic plaque.  In Suttie JW, editor.  Vitamin K Metabolism and Vitamin K-Dependent Proteins.  University Park Press; Baltimore, 1980.  p 269-73.
This research team demonstrated for the first time, the presence of a Gla containing protein, (influenced by vitamin K) in atherosclerotic plaque, which they named atherocalcin.  They believed that the functional significance of this finding was of great importance.  At that time, they wondered whether the circulating levels of the Gla protein might correlate with disease status, and function as a clinical parameter. 

Suttie JW.  Vitamin K metabolism and vitamin K-dependent proteins.  Baltimore:  University Park Press; 1980. 

Fraser JD, Price PA.  Lung, heart, and kidney express high levels of mRNA for the vitamin K-dependent matrix Gla protein.  Implications for the possible functions of matrix Gla protein and for the tissue distribution of the gamma-carboxylase.  J Biol Chem.  1988;263:11033-36. 

Van Haarlem LJM.  Biosynthesis, occurrence and characterization of Gla-containing proteins with a potential importance for cardiovascular diseases.  [Ph.D. thesis].   Netherlands:  University of Limburg Maastricht; 1989. 

 

1990s

Davies M.J.  A macro and microview of coronary vascular insult in ischemic heart disease.  Circulation.  1990;82(suppl II):II38-46.

Gijsbers BLMG, van Haarlem LJM, Soute, BAM, Ebberink RHM, Vermeer C.  Characterization of a GLA-containing protein from calcified human atherosclerotic plaques.  Arteriosclerosis.  1990;10:991. 

Schor AM, Allen TD, Canfield AE, Sloan P, Schor SL.  Pericytes derived from the retinal microvasculature undergo calcification in vitro.  J Cell Sci.  1990;97:449-61. 

Bolton-Smith C. Vitamin K.  In: James WPT and Garrow JS, Editors.  Human nutrition and dietetics.  Edinburgh:  Churchill Livingstone; 1993. P. 208-38.   

Bostrom K, Watson KE, Horn S, Wortham C, Herman IM, Demer LL.  Bone morphogenetic protein expression in human atherosclerotic lesions.  J Clin Invest.  1993;91:1800-9.

Shanahan CM, Cary NR, Metcalfe JC, Weissberg PL.  High expression of genes for calcification-regulating proteins in human atherosclerotic plaques.  J. Clin Invest.  1994 Jun;93(6):2393-402.
Calcification is common in atheromatous plaques and may contribute to plaque rupture and subsequent thrombosis.  Little is known about the mechanisms which regulate the calcification process.  The study shows that high levels of osteopontin and MGP were found in association with necrotic lipid cores and areas of calcification.  The predominant cell type was the macrophage-derived foam cell.  The postulated function of OP and MGP as regulators of calcification in bone and the high levels and co-localization of both in plaques, suggest they have an important role in plaque pathogenesis and stability

Jie KS, Bots ML, Vermeer C, Witteman JC, Grobbee DE.  Vitamin K intake and osteocalcin levels in women with and without aortic atherosclerosis:  A population based study.  Atherosclerosis.  1995;116(1):117-123.
A population-based study of postmenopausal women, aged 60-79 years, found that women aged 60-69 with aortic calcifications had lower vitamin K intakes than those without aortic calcifications.

Shearer, MJ.  Vitamin K.  Lancet.  1995;345(8944):229-34.

Davies M.J.  Stability and instability: two faces of coronary atherosclerosis.  Circulation.  1996;94:201320.

Sokoll LJ, Booth SL, O’Brien ME, Davidson KW, Tsaioun KI, Sadowski JA.  Changes in serum osteocalcin, plasma phylloquinone, and urinary carboxyglutamic acid in response to altered intakes of dietary phylloquinone in human subjects.  Am J Clin Nutr.  1997;65:779-84. 

Luo G, Ducy P, McKee MD, Pinero GJ, Loyer E, Behringer RR, Karsenty G.  Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein.  Nature.  1997 Mar 6;386(6620):78-81. 
Matrix GLA protein (MGP), is a mineral binding extracellular matrix (ECM) protein synthesized by vascular smooth-muscle cells and chondrocytes, two cell types that produce an uncalcified ECM.  Mice that lack MGP die as a result of arterial calcification which leads to blood vessel rupture.  Additionally they exhibit inappropriate calcification of various cartilages, include the growth plate.  This study demonstrates the importance of MGP for vascular health. Sufficient quantities of Vitamin K in the body are necessary for the activation of MGP in the body. 

Ferland G.  The vitamin K-dependent proteins:  An update.  Nutr. Review.  1998;56(8):223-30. 
Historically known for its role in blood coagulation, vitamin K also has been shown to be required for the activation of numerous proteins that are not involved in hemostasis.  Over the last 20 years, vitamin K–dependent proteins have been isolated in bone, cartilage, kidney, atheromatous plaque, and numerous soft issues.  Although the precise mechanism of action remains to be determined, the discovery of these proteins has proven important from a physiologic point of view.

Price P, Faus S, Williamson M.  Warfarin causes rapid calcification of the elastic lameliae in rat arteries and heart valves.  Arterioscler Thromb Vasc Biol.  1998;18:1400-07.
High doses of warfarin cause focal calcification of the elastic lamellae in the media of major arteries and in aortic heart valves in the rat.  Aortic calcification was first seen after 2 weeks of warfarin treatment and progressively increased in density at 3, 4, and 5 weeks of treatment.  By 5 weeks, the highly focal calcification of major arteries could be seen on radiographs and by visual inspection of the artery.  The calcification of arteries induced by warfarin is similar to that seen in the matrix Gla protein (MGP)–deficient mouse, which suggests that warfarin induces artery calcification by inhibiting gamma-carboxylation of MGP and thereby inactivating the putative calcification-inhibitory activity of the protein.  Warfarin treatment markedly increased the levels of MGP mRNA and protein in calcifying arteries and decreased the level of MGP in serum.

Proudfoot D, Skepper JN, Shanahan CM, Weissberg PL.  Calcification of human vascular cells in vitro is correlated with high levels of matrix Gla protein and low levels of osteopontin expression.  Arterioscler Thromb Vasc Biol.  1998;18:379-88. 
The cellular and molecular events leading to calcification in atherosclerotic lesions are unknown.  They and others have shown that bone-associated proteins, particularly matrix Gla protein (MGP) and osteopontin (OP), can be detected in atherosclerotic lesions, thus suggesting an active calcification process.  In the present study, they aimed to determine whether human vascular smooth muscle cells (VSMCs) could calcify in vitro and to determine whether MGP and OP have a role in vascular calcification.  We established that human aortic VSMCs and placental microvascular pericytes spontaneously form nodules in cell culture and induce calcification.  These studies reveal that human VSMCs are capable of inducing calcification and that MGP may have a role in human vascular calcification.

Sangiorgi G, Rumberger JA, Severson A, Edwards WD, Gregoire J, Fitzpatrick LA, Schwartz RS.  Arterial calcification and not lumen stenosis is highly correlated with atherosclerotic plaque burden in humans:  A histologic study of 723 coronary artery segments using nondecalcifying methodology.  J Am Coll Cardiol. 1998;31:126–133.

Shanahan CM, Proudfoot D, Farzaneh-Far A, Weissberg PL.  The role of Gla proteins in vascular calcification.  Crit Rev Eukaryot Gene Rxpr.  1998:8(304):357-75. 
Arterial calcification occurs with increasing age and in association with a diverse range of diseases, including atherosclerosis, diabetes, and uremia.  Evidence is accumulating that vascular calcification is an active process that has many similarities with ossification, including local expression of bone-associated collagenous and noncollagenous proteins.  Gla-containing proteins which respond to Vitamin K, which have the potential to regulate or contribute to vascular calcification are present in the human vasculature. 

Furie B, Bouchard BA, Furie BC.  Vitamin K-dependent biosynthesis of gamma-carboxyglutamic acid.  Blood.  1999:93(6):1798-08.
Vitamin K, an essential vitamin, is a cofactor for a single known enzymatic reaction: the conversion of glutamic acid to γ-carboxyglutamic acid in vitamin K-dependent proteins during their biosynthesis.  Since the discovery of vitamin K and its association with blood coagulation, many milestones have been passed on the road to understanding the biological role of vitamin K.  Important early landmarks include the discovery of vitamin K antagonists and their introduction as pharmacologic agents for anticoagulation; the discovery of γ-carboxyglutamic acid in blood clotting proteins; the detection of an enzymatic activity (ie, the vitamin K-dependent γ-glutamyl-carboxylase) that catalyzes the incorporation of CO2 into glutamic acid.  Because carboxylase activity is found in essentially all mammalian tissues and because γ-carboxyglutamic acid has been observed in both vertebrates and invertebrates, this amino acid must play an important biological role in protein function.  The biosynthesis of γ-carboxyglutamic acid is the topic of this review.

Seyama Y, et al, Comparative effects of vitamin K2 and vitamin E on experimental arteriosclerosis.  Int J Vitamin Nutr Res. 1999 Jan;69(1):23-6. 
Vitamin K deficiency appears to play a role in the development of osteoporosis and in the deposition of calcium into blood vessels. 

Shanahan CM, Cary NR, Salisbury JR, Proudfoot D, Weisserg PL, Edmonds ME.  Medial localization of mineralization-regulating proteins in association with Monckeberg’s sclerosis:  evidence for smooth muscle cell-mediated vascular calcification.  Circulation.  1999;100:2168-76. 
The study showed that matrix Gla protein (MGP) is highly upregulated in Vascular Smooth Muscle Cells adjacent to sites of calcification.  This finding led to the proposal of a feedback mechanism in which VSMCs sense neighboring calcification and upregulate MGP to attempt calcium clearance. 

Tsaioun KI.  Vitamin K-dependent proteins in the developing and aging nervous system.  Nutr. Rev.  1999;57(8):231-40. 
Although the warfarin embryopathy syndrome, with its neurologic and bone abnormalities, has been known for decades, the role of vitamin K in the brain has not been studied systematically.  Recently, it was demonstrated that vitamin K-dependent carboxylase expression is temporally regulated in a tissue-specific manner with high expression in the nervous system during the early embryonic stages and with liver expression after birth and in adult animals.  This finding, along with the discovery of wide distribution of the novel vitamin K-dependent growth factor, Gas6, in the central nervous system, provides compelling evidence of a biologic role of vitamin K during the development of the nervous system.  Hence, the knowledge of the biologic role of vitamin K in the brain may be important for unveiling the mechanisms of normal and pathologic development and aging of the nervous system. The role of the vitamin K-dependent protein Gas6 in activation of signal transduction events in the brain, in light of the age-related changes in the nervous system is also discussed.

 

2000s

Arad Y, Spadaro LA, Goodman K, Newstein D, Guerci AD.  Prediction of coronary events with electron beam computed tomography.  J Am Coll Cardiol.  2000;36:1253-60.  

Bostrom KI.  Cell differentiation in vascular calcification.  Z Kardiol.  2000;89:69-74. 
Ectopic tissue formation is commonly found in calcified atherosclerotic plaques.  This suggests that cell differentiation plays an important role in vascular calcification, even though the origin of the cells involved is unclear.  Calcifying vascular cells (CVCs), have many characteristics in common with bone cells, but there are also differences suggesting mechanisms applicable to the problem of osteoporosis may be active in the setting of vascular calcification.  Matrix GLA protein (MGP) deficient mice develop severe vascular calcification and die prematurely from heart failure and/or aortic rupture.  It has been hypothesized that MGP acts as a calcification inhibitor by binding calcium, preventing mineral deposition in extracellular fluids near the saturation point for calcium and phosphate.  Alternatively, MGP expression may be an attempt to regulate cell differentiation in the vascular wall, possibly by acting as an inhibitor to a factor able to induce cartilage and bone such as bone morphogenetic proteins (BMPs).

Campbell GR, Campbell J.  Vascular smooth muscle and arterial calcification.  Z Kardiol.  2000;89:54-62. 
Smooth muscle cultures can calcify under certain circumstances.  As a model system these cultures therefore provide information on why calcification occurs in atherosclerotic plaques.  Whether all smooth muscle cells (under certain conditions), or only specific populations, can produce this mineralization has not been resolved.  Demer's group has cloned calcifying vascular cells from subcultured bovine aorta and studied them in detail.  The article argues that while the normal process of smooth muscle phenotypic modulation seen in arterial repair could account for the observations, this view may be too simplistic considering the complex nature of the artery wall.  Certainly there is evidence for heterogeneity of smooth muscle cells in the artery wall and recent evidence suggests that stem cells can circulate in the blood and repopulate tissues.  Further studies are required to resolve the important question as to the origin of cells which produce mineralization in atheroma.

Canfield AE, Doherty MJ, Wood AC, Farrington C, Ashton B, Begum N, et al.  Role of pericytes in vascular calcification:  a review.  Z Kardiol.  2000;89 Suppl. 2):20-7.

Howe AM, Webster WS.  Warfarin exposure and calcification of the arterial system in the rat.  Int J Exp Pathol.  2000;81:51-56. 
There is evidence from knock-out mice that the extrahepatic vitamin K-dependent protein, matrix gla protein, is necessary to prevent arterial calcification. The aim of this study was to determine if a warfarin treatment regimen in rats, designed to cause extra-hepatic vitamin K deficiency, would also cause arterial calcification.  At the end of treatment the rats were killed and the vascular system was examined for evidence of calcification.  All treated animals showed extensive arterial calcification.  The cerebral arteries and the veins and capillaries did not appear to be affected.  It is likely that humans on long-term warfarin treatment have extrahepatic vitamin K deficiency and hence they are potentially at increased risk of developing arterial calcification.

Price PA, Faus SA, Williamson MK.  Warfarin-induced artery calcification is accelerated by growth and vitamin D.  Arterioscler Thromb Vasc Biol.  2000;20:317-27. 
The present studies demonstrate that growth and vitamin D treatment enhance and expand the artery calcification in rats given sufficient doses of Warfarin to inhibit gamma-carboxylation of matrix Gla protein, a calcification inhibitor.  Treatment for 2 weeks with Warfarin caused massive focal calcification of the artery media in 20-day-old rats and less extensive focal calcification in 42-day-old rats.  In contrast, no artery calcification could be detected in 10-month-old adult rats even after 4 weeks of Warfarin treatment.  This observation suggests that increased susceptibility to Warfarin-induced artery calcification could be related to higher serum phosphate levels.  The second set of experiments examined the possible synergy between vitamin D and Warfarin in artery calcification.  Because Warfarin treatment had no effect on the elevation in serum calcium produced by vitamin D, the synergy between Warfarin and vitamin D is probably best explained by the hypothesis that Warfarin inhibits the activity of matrix Gla protein as a calcification inhibitor

Schinke T, Karsenty G.  Vascular calcification – a passive process in need of inhibitors.  Nephrol Dial Transplant.  2000;15:1272-4. 
Mouse genetic studies have significantly improved our understanding of vascular calcification.  Important information comes mostly from the knockout of MgP (Matrix Gla Protein): vascular calcification is a passive process that requires active inhibition.  MgP is the molecule that is responsible for this inhibition in mice.  Although the importance of MgP to prevent arterial calcification in humans has not been clearly established yet, theoretically it seems that up-regulating MgP expression in human arteries could be beneficial to prevent atherosclerotic calcification.  MgP needs vitamin K to be fully effective in inhibiting calcification.

Schurgers LJ, Vermeer C.  Determination of phylloquinone and menaquinones in food.  Effect of food matrix on circulating vitamin K concentrations.  Haemostasis.  2000 Nov-Dec;30(6):298-7. 
To investigate the effect of the food matrix on vitamin K bioavailability, 6 healthy male volunteers consumed either a detergent-solubilized K(1) (3.5 micromol) or a meal consisting 400 g of spinach (3.5 micromol K(1)) and 200 g of natto (3.1 micromol K(2)).  The absorption of pure K(1) was faster than that of food-bound K vitamins (serum peak values at 4 h vs. 6 h after ingestion).  Moreover, circulating K(2) concentrations after the consumption of natto were about 10 times higher than those of K(1) after eating spinach.  It is concluded that the contribution of K(2) vitamins (menaquinones) to the human vitamin K status is presently underestimated, and that their potential interference with oral anticoagulant treatment needs to be investigated.

Shanahan CM, Proudfoot D, Tyson KL, Cary NR, Edmonds M, Weissberg PL.  Expression of mineralization-regulating proteins in association with human vascular calcification.  Z Kardiol.  2000;89:63-8. 
A number of studies have documented expression of mineralisation-regulating proteins in association with human atherosclerotic calcification leading to the suggestion that human vascular calcification may be a regulated process with similarities to developmental osteogenesis.  These studies imply that both medial and intimal vascular calcification are regulated processes; however the aetiology of each pathology differs.

Shearer MJ.  Role of vitamin K and Gla proteins in the pathophysiology of osteoporosis and vascular calcification.  Curr Opin Clin Nutr Metab Care.  2000;3:433-38. 
Among the proteins known or suspected to be involved in bone and vascular biology are several members of the vitamin K-dependent or Gla protein family. This review focuses on the role of two of these: osteocalcin and matrix Gla protein.  Osteocalcin metabolism has been implicated in the pathogenesis of osteoporosis through an unknown mechanism that may be linked to suboptimal vitamin K status resulting in its undercarboxylation and presumed dysfunction. It has been recently determined that matrix Gla protein functions as a powerful inhibitor of calcification of arteries and cartilage.

Vermeer C, Schurgers LJ.  A comprehensive review of vitamin K and vitamin K antagonists.  Hematol Oncol Clin North Am.  2000 Apr;14(2):339-53.
Vitamin K is involved in many physiologic processes and recommended daily allowances must be redefined.  According to a new consideration, a substantial part of the population is mildly deficient in vitamin K, and at later ages this deficiency may contribute to increased bone fracture risk, arterial calcification, and cardiovascular disease.

Booth SL, Lichtenstein AH, O’Brien-Morse M, et al.  Effects of a hydrogenated form of vitamin K on bone formation and resorption.  Am J Clin Nutr.  2001;74(6):783-90.  
Hydrogenation of vegetable oils affects blood lipid and lipoprotein concentrations.  However, little is known about the effects of hydrogenation on other components, such as vitamin K.  Low phylloquinone (vitamin K1) intake is a potential risk factor for bone fracture, although the mechanisms of this are unknown.  The objective was to compare the biological effects of phylloquinone and its hydrogenated form, dihydrophylloquinone, on vitamin K status and markers of bone formation and resorption.  In a randomized crossover study, 15 young adults were fed a phylloquinone-restricted diet (10 microg/d) for 15 days followed by 10 days of repletion (200 microg/d) with either phylloquinone or dihydrophylloquinone.  In comparison with phylloquinone, dihydrophylloquinone was less absorbed and had no measurable biological effect on measures of bone formation and resorption.  Hydrogenation of plant oils appears to decrease the absorption and biological effect of vitamin K in bone.

Dhore CR, Cleutjens JP, Lutgens E, Cleutjens KB, Geusens PP, Kitslaar PJ, et al.  Differential expression of bone matrix regulatory proteins in human atherosclerotic plaques.  Arterioscler Thromb Vasc Biol.  2001;21:1998-03. 
Analysis of normal vs. atherosclerotic human tissue shows constitutive expression of MGP in the vessel wall that is sustained during calcification. 

Glass CK, Witztum JL.  Atherosclerosis: The road ahead.  Cell.  2001;104:503-16. 
An article that reviews a narrow aspect of the research on atherosclerosis, and manages to never mention the burgeoning research on the vitamin K families and their relationship to calcification, coronary artery disease, and vitamin K dependent proteins.  A remarkably restricted ‘road’ they seek to travel within medicine…

Huang H, Virmani R, Younis H, Burke A, Kamm R, et al.  The impact of calcification on the biomechanical stability of atherosclerotic plaques.  Circulation.  2001;103:1051-56. 

Hendler SS, Rorvik DR, eds.  PDR for Nutritional Supplements.  Montvale:  Medical Economics Company, Inc; 2001. 

Kaneki M, Hodges, SJ, Hosoi T, Fukiwara S, Lyons A, Crean SJ, et al.  Japanese fermented soybean food as the major determinant of the large geographic difference in circulating levels of vitamin K2:  possible implications for hip-fracture risk.  Nutrition. 2001:17(4):315-21.
Increasing evidence indicates a significant role for vitamin K in bone metabolism and osteoporosis. In this study, we investigated the effect of Japanese fermented soybean food, natto, on serum vitamin K levels. We analyzed the relation between the regional difference in natto intake and fracture incidence. A statistically significant inverse correlation was found between incidence of hip fractures in women and natto consumption in each prefecture throughout Japan. These findings suggest the possibility that higher MK-7 levels resulting from natto consumption may contribute to the relatively lower fracture risk in Japanese women.

Keelan PC, Bielak LF, Ashai K, Jamjoum LS, Denktas AE, Rumberger JA, et al.  Long-term prognostic value of coronary calcification detected by electron-beam computed tomography in patients undergoing coronary angiography.  Circulation.  2001; 104:412-17.

Schurgers LJ, Dissel PE, Spronk HM, et al.  Role of vitamin K and vitamin K-dependent proteins in vascular calcification.  Z Kardiol.  2001;90 Suppl 3:57-61.  
Vitamin K has a key function in the synthesis of at least two proteins involved in calcium and bone metabolism, namely osteocalcin and matrix Gla-protein (MGP).  MGP was shown to be a strong inhibitor of vascular calcification.  Some hypothesized that insufficient dietary vitamin K nutritional status results in inadequate carboxylation and, presumably, inactive MGP.  Accumulating data suggest that extrahepatic tissues such as bone and vessel walls require higher dietary intakes and have a preference for menaquinone rather than for phylloquinone.  Thus, insufficient dietary vitamin K and undercarboxylation of MGP is a risk factor for vascular calcification and that the present recommended daily allowance values are too low to ensure full carboxylation of MGP.   

Spronk HM, Soute BA, Schurgers LJ, Cleutjens JP, Thijssen HH, De Mey JG, Vermeer C.  Matrix Gla protein accumulates at the border of regions of calcification and normal tissue in the media of the arterial vessel wall.  Biochem Biophys Res Commun.  2001 Nov 30;289(2):485-90.  
Vitamin K-dependent matrix Gla protein (MGP) has been suggested to play a role in the inhibition of soft-tissue calcification.  Their data demonstrate the close association between MGP and calcification.  It is suggested that undercarboxylated MGP is biologically inactive and that poor vascular vitamin K status that results, may form a risk factor for vascular calcification.

Tintut Y, Demers LL.  Recent advances in multifactorial vascular calcification. Current Opinion in Lipidology.  2001;12(5):555-60. 

Vermeer C, Braam L.  Role of K vitamins in the regulation of tissue calcification.  J Bone Miner Metab.  2001;19:201-6. 
Dietary menaquinones may be more efficiently absorbed than phylloquinone, leading to the proposal that even though phylloquinone comprises a large amount of vitamin K intake, phlloquinone and menaquinones may both contribute similarly to nutriture. 

Schurgers LJ, Vermeer C.  Differential lipoprotein transport pathways of K-vitamins in healthy subjects.  Biochim Biophys Acta. 2002 Feb 15;1570(1):27-32.
Following intestinal absorption of K1 and K2, the serum transport of these lipophilic compounds to their target tissues take place via lipoproteins.  During the first four hours after intake all K-vitamins were found to be associated with triacylglycerol-rich lipoprotein (TGLRP).  This suggests that initially most of the K-vitamins are transported to the liver.  However, both menaquinones were found in TGRLP and low-density lipoproteins, and MK4 was even present in high density lipoprotein.  It explains why menaquinones may have a relatively large impact on extra hepatic vitamin K status than generally assumed, and that MK7 may form a more constant source of vitamin K.

Schurgers LJ, Shearer MJ, Soute BA, Elmadfa I, Harvey J, Wagner KH, et al.  Novel effects of diets enriched with corn oil or with an olive oil/sunflower oil mixture on vitamin K metabolism and vitamin K-dependent proteins in young men.  J Lipid Res.  2002 Jun;43(6):878-84. 
They concluded that both oils affected vitamin K absorption and/or metabolism which may increase the requirements for gamma-carboxylation. 

Shoji S.  Vitamin K and vascular calcification.  Clin Calcium.  2002 Aug;12(8):1123-8. 
The role of vitamin K in the synthesis of some coagulation factors is well known.  The implication of vitamin K in vascular health was demonstrated in many surveys and studies conducted over the past years on the vitamin K-dependent proteins non-involved in coagulation processes.  The vitamin K-dependent matrix Gla protein is a potent inhibitor of the arterial calcification, and may become a non-invasive biochemical marker for vascular calcification.  Vitamin K(2) is considered to be more important for vascular system, if compared to vitamin K(1).

Wayhs R, Zelinger A, Raggi P.  High coronary artery calcium scores pose an extremely elevated risk for hard events.  J Am Coll Cardiol.  2002;39:225-30.  
We sought to assess the natural history of a cohort of asymptomatic individuals with very high (> or = 1,000) calcium scores (CSs) on a screening electron beam tomography (EBT).  We also compared our prospective cohort with that of historical controls with severe abnormalities on myocardial perfusion imaging (MPI).  Coronary calcium detected on EBT imaging has been shown to correlate with the total plaque burden.  Ninety-eight asymptomatic subjects were followed for an average of 17 +/- 11 months for the occurrence of hard coronary events (HCEs), defined as myocardial infarction or coronary death.  All patients had an initial calcium score  > or = 1,000.  During the follow-up period, 35 patients (36%) suffered an HCE.  All events were recorded in the first 28 months of follow-up.  A high Calcium Score (> or = 1,000) on a screening EBT in an asymptomatic person portends a very high risk of an Hard Coronary Event in the short term.

Booth SL, Martini L, Peterson JW, Saltzman E, Dallal GE, Wood RJ.  Dietary phylloquinone depletion and repletion in older women.  J Nutr.  2003;133:2565-69.
Biological markers indicative of poor vitamin K status have been associated with a greater risk for hip fracture in older men and women.  However, the dietary phylloquinone intake required to achieve maximal carboxylation of hepatic and extrahepatic vitamin K–dependent proteins is not known.  In an 84 day study in a metabolic unit, 21 older (60–80 y) women were fed a phylloquinone-restricted diet (18 μg/d) for 28 days, followed by stepwise repletion of 86, 200 and 450 μg/d of phylloquinone.  The γ-carboxylation of prothrombin was restored to normal levels in response to phylloquinone supplementation at 200 μg/day.  In contrast, all other biochemical markers of vitamin K status remained below normal levels after short-term supplementation of up to 450 μg/day of phylloquinone.  These data support previous observations in rats that hepatic vitamin K–dependent proteins have preferential utilization of phylloquinone in response to phylloquinone dietary restriction.  Moreover, our findings suggest that the current recommended Adequate Intake levels of vitamin K (90 μg/d) in women do not support maximal osteocalcin γ-carboxylation in older women.

Doherty TM, Asota K, Fitzpatrick LA, Qiao J-H, Wilkin DJ, Detrano RC, et al.  Calcification in atherosclerosis:  Bone biology and chronic inflammation at the arterial crossroads.  Proc Natl Acad Sci.  2003;100:11201-206.

Essalihi R, Dao H, Yamaguchi N, Moreau P.  A new model of isolated systolic hypertension induced by chronic warfarin and vitamin K1 treatment.  Am J Hypertens.  2003;16:103-10. 

El-Maadawy A, Kaartinen MT, Schinke T, Murshed M, Karsenty G, McKee MD.  Cartilage formation and calcification in arteries of mice lacking matrix Gla protein.  Connect Tissue Res.  2003;44 Supple 1:272-9.
Matrix Gla protein (MGP) is a protein expressed predominantly by vascular smooth muscle cells and by chrondrocytes.  Mice lacking MGP die after 1-3 months due to calcification of elastic fibers and the rupture of large elastic arteries such as the aorta.  This study provides evidence that the absence of MGP triggers chondrocyte differentiation and cartilage formation in blood vessels. 

Mody N, Tintut Y, Radcliff K, Demer LL.  Vascular calcification and its relation to bone calcification:  possible underlying mechanisms.  J Nucl Cardiol.  2003;10:177-83. 
Vascular calcification occurs frequently in atheromas and carries significant risk for future cardiac events.  The constituents of bone matrix and mineralization are present in atherosclerotic lesions, and a population of cells that secrete these products in vitro has been identified.  The phenotype of these cells and their capacity to secrete osteoid are under the control of numerous inflammatory mediators and are thought to be regulated by similar molecular mechanisms as osteogenesis.

Spronk HM, Soute BA, Schurgers LJ, Thijssen HH, De Mey JG, Vermeer C.  Tissue-specific utilization of menaquinone-4 results in the prevention of arterial calcification in warfarin-treated rats.  J Vasc Res. 2003 Nov-Dec;40(6):531-7. 
MK4, not K1, inhibits warfarin-induced arterial calcification.  The observed differences between K1 and MK4 may be explained by differences in their tissue biovavailability and cofactor utilization in the carboxylase reaction. 

Sweatt A, Sane DC, Hutson SM, Wallin R.  Matrix Gla protein (MGP) and bone morphogenetic protein-2 in aortic calcified lesions of aging rats.  J Thromb Haemost.  2003;1:178-85. 

Allison MA, Criqui MH, Wright CM.  Patterns and risk factors for systemic calcified atherosclerosis. Arterioscler Thromb Vasc Biol. 2004; 24: 331-36. 
Whole-body electron beam computed tomography scans were performed on 650 asymptomatic subjects to assess the carotid, coronary, proximal, and distal aorta and iliac vessels for atherosclerotic calcification.  The mean age was 57.3 and 53% were male.  Correlation patterns were similar in both genders, with the largest interbed correlations between the distal aorta and iliac vessels (r=0.51 to 0.60).  The average man and woman had calcium earliest in the coronaries (younger than age 50 years) and the distal aorta (age 50 to 60), respectively.  The prevalence of calcium was greater than 80% for most beds in men older than age 70 and greater than 60% in all beds for women.  Approximately one third of subjects younger than 50 were free of calcified disease, whereas all subjects older than 70 were found to have some calcium.  Age and hypertension were the dominant risk factors for systemic calcified atherosclerosis.

Abedin M, Tintut Y, Demer LL.  Vascular calcification:  mechanisms and clinical ramifications.  Arterioscler Thromb Vasc Biol.  2004 Jul;24(7):1161-70. 
Vascular calcification, long thought to result from passive degeneration, involves a complex, regulated process of biomineralization resembling osteogenesis. Evidence indicates that proteins controlling bone mineralization are also involved in the regulation of vascular calcification.  Artery wall cells grown in culture are induced to become osteogenic by inflammatory and atherogenic stimuli.  Furthermore, osteoclast-like cells are found in calcified atherosclerotic plaques, and active resorption of ectopic vascular calcification has been demonstrated.  The relationship between calcification and clinical events likely relates to mechanical instability introduced by calcified plaque at its interface with softer, noncalcified plaque.  Vascular calcification is exacerbated in certain clinical entities, including diabetes, menopause, and osteoporosis.

Berkner, KL, Runge KW.  The physiology of vitamin K nutriture and vitamin K-dependent protein function in atherosclerosis.  J Thromb Haemost.  2004;2(12):2118-32.
Recent advances in the discovery of new functions for vitamin K-dependent (VKD) proteins have led to a substantial revision in our understanding of vitamin K physiology.  The only unequivocal function for vitamin K is as a cofactor for the carboxylation of VKD proteins which renders them active.  VKD proteins are now known to be present in virtually every tissue and to be important to bone mineralization, arterial calcification, apoptosis, phagocytosis, growth control, chemotaxis, and signal transduction.  The development of improved methods for analyzing vitamin K has shed considerable insight into the relative importance of different vitamin K forms in the diet and their contribution to hepatic vs. non-hepatic tissue.  New assays that measure the extent of carboxylation in VKD proteins have revealed that while the current recommended daily allowance for vitamin K is sufficient for maintaining functional hemostasis, the undercarboxylation of at least one non-hemostatic protein is frequently observed in the general population.

Braam L, McKeown J, Jacques P, Lichtenstein A, Vermeer C, Wilson P, et al.  Dietary phylloquinone intake as a potential marker for a heart-healthy dietary pattern in the Framingham Offspring cohort.  J Am Diet Assoc. 2004; 104:1410-14. 
Dietary phylloquinone intakes were assessed by a food frequency questionnaire in 1,338 men and 1,603 women (mean age, 54 years) participating in the Framingham Heart Study.  Cross-sectional associations with lifestyle characteristics and lipid profiles, including total cholesterol, low-density lipoprotein and high-density lipoprotein cholesterol, and triglyceride concentrations, were estimated across categories of phylloquinone intakes.  Participants in the highest quintile category of phylloquinone intake consumed more fruit, vegetables, fish, dietary fiber, and dietary supplements ( P <.001), and consumed less meat and less saturated fat ( P <.001).  Higher phylloquinone intakes were also associated with lower triglyceride concentrations ( P <.001).  In conclusion, a high phylloquinone intake may be a marker for an overall heart-healthy dietary pattern.

Doherty T, Fitzpatrick L, Inoue D, Qiao J, Fishbein M, et al.  Molecular, endocrine, and genetic mechanisms of arterial calcification.  Endrocr Rev.  2004;25:629-72. 

Ehara S, Kobayashi Y, Yoshiyama M, Shimada K, Shimada Y, et al.  Spotty calcification typifies the culprit plaque in patients with acute myocardial infarction:  an intravascular ultrasound study.  Circulation.  2004;110:3424-29. 

Geleijnse JM, Vermeer C, Grobbee DE, Schurgers LJ, Knapen MH, van der Meer IM, et al.  Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease:  The Rotterdam Study.  J. Nutr. 2004;134(11):3100-5.
Ten year follow up of 4,500 elderly subjects (the Rotterdam study cohort).  A population based study demonstrating that high dietary intake of vitamin k2 influences cardiovascular health and reduced cardiovascular mortality.  In this study dietary vitamin k2 appeared to be superior to vitamin K1.  Vitamin K2 intake is inversely correlated with cardiovascular disease and mortality.  This population based study, which took place over a ten year period, followed 4807 initially healthy men and women 55 years or more old.  Findings from the study indicate that eating foods rich in natural vitamin k2 (at least 32 mcg per day) results in 50% reduction in arterial calcification, 50% reduction of cardiovascular death, and 25% reduction of all cause mortality. 

Higdon J.  (May 2004). "Vitamin K" (http://lpi.oregonstate.edu/infocenter/vitamins/vitaminK/ ). Linus Pauling Institute, Oregon State University. Updated by Victoria J Drake, Ph.D., LPI.  Retrieved 2012-12-12.

Murshed M, Schinke, T, McKee MD, Karsenty G.  Extracellular matrix mineralization is regulated locally:  Different roles of two gla-containing proteins.  J Cell Biol.  2004;165(5):625-30. 
Extracellular matrix mineralization (ECMM) is a physiologic process in the skeleton and in teeth and a pathologic one in other organs.  The molecular mechanisms controlling ECMM are poorly understood.  Inactivation of Matrix gla protein (MGP) revealed that MGP is an inhibitor of ECMM.  The fact that MGP is present in the general circulation raises the question of whether ECMM is regulated locally and/or systemically.  Here, we show that restoration of MGP expression in arteries rescues the arterial mineralization phenotype of Mgp/− mice, whereas its expression in osteoblasts prevents bone mineralization.  In contrast, raising the serum level of MGP does not affect mineralization of any ECM.  In vivo mutagenesis experiments show that the anti-ECMM function of MGP requires four amino acids which are γ-carboxylated (gla residues), and which can be found in vitamin K.

Jono S, Ikari Y, Vermeer C, Dissel P, Hawegawsa K, Shioi A, et al.  Matrix Gla protein is associated with coronary artery calcification as assessed by electron-beam computed tomography.  Thromb Haemost.  2004;91:790-4. 
Matrix Gla protein (MGP) is an extracellular matrix protein with wide tissue distribution.  It has been demonstrated that the expression of MGP is detected not only in the normal blood vessels but also in calcified atherosclerotic plaques, and that MGP deficient mice develop extensive arterial calcification.  MGP is thought to be a regulator of vascular calcification.  We evaluated the severity of CAC, and measured serum MGP levels in 115 subjects with suspected coronary artery disease.  The serum MGP levels were lower in patients with CAC than in those without CAC (p<0.001).  As the severity of CAC increased, there was a significant decrease in serum MGP levels.  We found that serum MGP levels are inversely correlated with the severity of CAC.

Schurgers LJ, Aebert H, Vermeer C, Bultmann B, Janzen J.  Oral anticoagulant treatment:  Friend or foe in cardiovascular disease?  Blood.  2004;104:3231-32.
Calcification is a common complication in cardiovascular disease and may affect both arteries and heart valves.  Matrix gamma-carboxyglutamic acid (Gla) protein (MGP) is a potent inhibitor of vascular calcification, the activity of which is regulated by vitamin K.  In animal models, vitamin K antagonists (oral anticoagulants [OACs]) were shown to induce arterial calcification.  To investigate whether long-term OAC treatment may induce calcification in humans also, we have measured the grade of aortic valve calcification in patients with and without preoperative oral anti-coagulant treatment.  OAC-treated subjects were matched with nontreated ones for age, sex, and disease.  Calcifications in patients receiving preoperative OAC treatment were significantly (2-fold) larger than in nontreated patients.  These observations suggest that OACs, which are widely used for antithrombotic therapy, may induce cardiovascular calcifications as an adverse side effect.

Schori TR, Stungis GE.  Long-term warfarin treatment may induce arterial calcification in humans:  case report.  Clin Invest Med.  2004;27:107-9. 

Vermeer C, Shearer MJ, Zittermann A, Bolton-Smith C, Szulc P, Hodges S, Walter P, Rambeck W, Stöcklin E, Weber P. Beyond deficiency: potential benefits of increased intakes of vitamin K for bone and vascular health. Eur J Nutr. 2004 Dec;43(6):325-35.
From the available dietary data, it would appear that daily intakes of between 200 and 500μg/day of dietary vitamin K may be required for optimal gamma-carboxylation of OC, which may in turn benefit bone health. There is growing evidence to suggest that vitamin K may be acting synergistically with vitamin D, calcium and possible other micronutrients to maximally influence bone mineral accretion and potentially inhibit vascular calcification.  As such, health benefits may accrue from supplemental vitamin K being combined with vitamin D and minerals.  Considerably more work is required in the area of vitamin K including understanding relative bioavailability, optimal tissue-specific status indicators, and the relative importance of gamma-carboxylation status to the growing number of health outcomes that may be influenced by vitamin K inadequacy.

Adams, J, Pepping J (2005).  Vitamin K in the treatment and prevention of osteoporosis and arterial calcification.  Am J Health Syst Pharm 62(15):1574-81. 
Current dosage recommendations for vitamin K may be too low.

Bernker KL.  The vitamin K-dependent carboxylase.  Annu Rev Nutr.  2005;25:127-49. 

Csiszar A, Smith KE, Koller A, Kaley G, Edwards JG, et al.  Regulation of bone morphogenetic protein-2 expression in endothelial cells:  Role of nuclear factor-kappa B activation by tumor necrosis factoro-alpha, H202, and high intravascular pressure.  Circulation.  2005;111:2364-72.

Erkkila AT, Booth SL, Hu FB, Jacques PF, Manson JE, Rexrode KM, et al.  Phylloquinone intake as a marker for coronary heart disease risk but not stroke in women.  Eur J Clin Nutr 2005;59:196-04. 

Fujii K, Carlier SG, Mintz GS, Takebayashi H, Yasuda T, et al.  Intravascular ultrasound study of patterns of calcium in ruptured coronary plaques.  The Am J of Cardio.  2005;96:352-57. 

Hruska Ka, Mathew S, Saab G.  Bone morphogenetic proteins in vascular calcification.  Circulation.  2005;97:105-14.
Vascular calcification is a common problem among the elderly and those with chronic kidney disease (CKD) and diabetes.  The process of vascular calcification in CKD appears to involve a change in the vascular smooth muscle cell (VSMC) resulting in mineralization of the extracellular matrix.  The bone morphogenetic proteins (BMPs) are important regulators in orthotopic bone formation, and their localization at sites of vascular calcification raises the question of their role.  In this review, we will discuss the actions of the BMPs in vascular calcification.

Koos R, Mahnken A, Muhlenbruch G, Brandenburg V, Pfleuger B, et al.  Relation of oral anticoagulation to cardiac vascular and coronary calcium assessed by multislice spiral computed tomography.  Am J Cardiol.  2005;96:747-49.

Nadra I, Mason J, Philippidis P, Florey O, Smythe C, et al.  Proinflammatory activation of macrophages by basic calcium phosphate crystals via protein Kinase C and MAP Kinase Pathways:  A vicious cycle of inflammation and arterial calcification?  Circ Res.  2005;96:1248-56.

Sato Y, Nakamura R, Satoh M, Fujishita K, Mori S, Ishida S, et al.  Thyroid hormone targets matrix Gla protein gene associated with vascular smooth muscle calcification.  Circ Res.  2005 Sep 16;97(6):550-7.
The study suggest that thyroid hormone directly facilitates MGP gene expression in smooth muscle cells via thyroid hormone nuclear receptors, leading to the prevention of vascular calcification in vivo. 

Schurgers, LJ, Teunissen KJ, Knapen MH, et al.  Novel conformation-specific antibodies against matrix gamma-carboxyglutamic acid (GLA) protein:  undercarboxylated matrix GLA protein as marker for vascular calcification.  Arterioscler Thromb Vas Biol.  2005;25(8):1629-33. 
A small human study that employed conformation-specific antibodies against MGP to examine whether impaired carboxylation of this protein possibly contributes to arterial calcification.  In healthy subjects, undercarboxylated MGP (ucMGP) was not detected in the innermost lining of the carotid artery; in contrast, the majority of MGP in the carotid arterial lining of patients with atherosclerosis was undercarboxylated.  

Vengrenyuk Y, Cardoso L, Weinbaum S.  Micro-CT based analysis of a new paradigm for vulnerable plaque rupture:  Cellular microcalcifications in fibrous caps.  Mol Cell Biomech.  2008;5:37-47. 

Villines TC, Hatzigeorgiou C, Feuerstein IM, O’Malley PG, Taylor AJ.  Vitamin K1 intake and coronary calcification.  Coron Artery Dis. 2005;16(3):199-03.
A prospective cohort study in 807 men and women, aged 39 to 45 years, did not find a correlation between dietary vitamin K1 intake and coronary artery calcification, as measured by electron-beam computed tomography (EBT).

Vliegenthart R, Oudkerk M, Hofman A, Oei HH, van Dijck W, van Rooij FJ, Witteman JC.  Coronary calcification improves cardiovascular risk prediction in the elderly.  Circulation.  2005; 112: 572-77.

Clarke M, Figg N, Maguire J, Davenport A, Goddard M, et al.  Apoptosis of vascular smooth muscle cells induces features of plaque vulnerability in atherosclerosis.  Nat Med.  2006;12:1075-80. 

Johnson RC, Leopold JA, Loscalzo J.  Vascular calcification:  Patho-biological mechanisms and clinical implications.  Circ Res.  2006;99:1044-59. 

Mazzini MJ, Schulze PC.  Proatherogenic pathways leading to vascular calcification.  Eur J Radio. 2006 Mar;57(3):384-92. 
Cardiovascular disease is the leading cause of morbidity and mortality in the western world and atherosclerosis is the major common underlying disease.  The pathogenesis of atherosclerosis involves local vascular injury, inflammation and oxidative stress as well as vascular calcification.  Recent studies identified vascular calcification in early stages of atherosclerosis and its occurrence has been linked to clinical events in patients with cardiovascular disease.  They review the current knowledge on molecular pathways of vascular calcification and their relevance for the progression of cardiovascular disease.

Proudfoot D, Shanahan CM.  Molecular mechanisms mediating vascular calcification: Role of matrix Gla protein.  Nephrology (carlton).  2006 Oct;11(5):455-61.
Patients with chronic kidney disease (CKD) have a higher incidence of vascular calcification and a greatly increased risk of cardiovascular death.  MGP inhibits calcium deposits.  MGP is a vitamin K-dependent protein that is also highly expressed by vascular smooth muscle cells.  It potentially acts in several ways to regulate calcium deposits including (i) binding calcium ions and crystals (ii) antagonizing bone morphogenetic protein and altering cell differentiation (iii) binding to extracellular matrix components (iv) regulating apoptosis.  Strategies that increase MGP expression may inhibit calcification in kidney disease.

Suttie, JW.  Vitamin K.  In: Shils ME, Shilke M, Ross Ac, Caballero B, Cousins RJ, Editors.  Modern nutrition in health and disease.  10th ed.  Baltimore:  Lippincott Williams & Wilkins; 2006.  p. 412-25

Aikawa E, Nahrendorf M, Figueiredo J, et al.  Osteogenesis associates with inflammation in early-stage atherosclerosis evaluated by molecular imaging in vivo.  Circulation.  2007;116:2841-50. 

Maas HA, van der Schouw YT, Beijerinck D, Deurenberg JJ, Mali WP, Grobbee DE, et al.  Vitamin K intake and calcifications in breast arteries.  Maturitas.  2007;56(30:273-79.
The study did not find vitamin K1 intake to be associated with calcification of breast arteries ina cross-sectional study of 1,689 women, aged 49 to 70 years

Maree AO, Jneid H, Palacios IF, Rosenfield K, MacRae CA, Fitzgerald DJ.  Growth arrest specific gene (GAS) 6 modulates platelet thrombus formation and vascular wall homeostasis and represents an attractive drug target.  Curr Pharm Des.  2007; 13(26):2656-61.

Motoyama S, Kondo T, Sarai M, Sugiura A, Harigaya H, et al.  Multislice computed tomographic characteristics of coronary lesions in acute coronary syndromes.  J of the Am College of Cardio.  2007;50:319-26. 

Schurgers, LJ, Spronk HM, Soute BA, Schiffers PM, DeMey JGR, et al.  Regression of warfarin-induced medial elastocalcinosis by high intake of K vitamins in rats.  Blood.  2007 Nov 30;109:2823-31.  
An adequate intake of vitamin K2 has been shown to positively influence the cardiovascular system.  Vitamin K2 activates matrix Gla Protein (MGP) which inhibits calcium from depositing in the vessel walls.  Calcium will be removed in a coordinated system of activated MGP, soluble factors, cells and tissues, keeping the arteries healthy and flexible. 

Schurgers LJ, Spronk HM, Skepper JN, Hackeng TM, Shanahan CM, Vermeer C, et al.  Post-translational modifications regulate matrix Gla protein function:  Importance for inhibition of vascular smooth muscle cell calcification.  J Thromb Haemost.  2007 Dec;5(12):2503-11.
Matrix Gla protein (MGP) is a small vitamin K-dependent protein containing five gamma-carboxyglutamic acid (Gla) residues that are believed to be important in binding Ca (2+) calcium crystals and bone morphogenetic protein.  The study investigated the effects of MGP in human vascular smooth muscle cell monolayers that undergo calcification after exposure to an increase in Ca(2+) concentration.  The data demonstrated that both gamma-glutamyl carboxylation and serine phosphorylation of matrix gla protein contribute to its function as a calcification inhibitor via binding to the cell surface and to vesicle like structures.

Schurgers LJ, Teunissen KJF, Hamulyak K, Knapen MHJ, Vik H, Vermeer C.  Vitamin K-containing dietary supplements:  Comparison of synthetic vitamin K1 and natto-derived menaquinone-7.  Blood. 2007;109:3279-83. 

Belovici MI, Pandele, GI.  Arterial media calcification in patients with type 2 diabetes mellitus.  Rev Med Chir Soc Med Nat Lasi. 2008 Jan-Mar;112(1):21-34.
Arterial calcification was previously viewed as an inevitable, passive, and degenerative process that occurred at the end stages of atherosclerosis.  Recent studies, however, have demonstrated that calcification of arteries is a complex and regulated process.  It may occur in conjunction with atherosclerosis or in an isolated form that is commonly associated with diabetes and renal failure.  Higher artery calcium scores are associated with increased cardiovascular events, and some aspects of arterial calcification are similar to the biology of forming bone.  Arterial calcification can thus be viewed as a distinct inflammatory arteriopathy, much like atherosclerosis and aneurysms, with its own contribution to cardiovascular morbidity and mortality.

Clarke M, LittlewoodT, Figg N, Maguire J, Davenport A, et al.  Chronic apoptosis of vascular smooth muscle cells accelerates atherosclerosis and promotes calcificationand medial degeneration.  Circ Res.  2008;102:1529-38. 

Cranenburg EC, Vermeer C Koos R, Boumans MLHackeng TMBouwman FG, et al.  The circulating inactive form of matrix Gla protein (ucMGP) as a biomarker for cardiovascular calcification.  J Vasc Res.  2008;45(5):427-36. 
Matrix gamma-carboxyglutamate (Gla) protein (MGP) is a vitamin K-dependent protein and a strong inhibitor of vascular calcification.  Vitamin K deficiency leads to inactive uncarboxylated MGP (ucMGP), which accumulates at sites of arterial calcification.  We hypothesized that as a result of ucMGP deposition around arterial calcification, the circulating fraction of ucMGP is decreased.  All four patient populations had significantly lower ucMGP levels.  In angioplasty patients and in those with aortic stenosis, some overlap was observed with the control population.  However, in the hemodialysis and calciphylaxis populations, virtually all subjects had ucMGP levels below the normal adult range.  Serum ucMGP may be used as a biomarker to identify those at risk for developing vascular calcification. This assay may become an important tool in the diagnosis of cardiovascular calcification.

Demer L, Tintut Y.  Vascular calcification:  Pathobiology of a multifaceted disease.  Circulation. 2008;117:2938-48.
Clinically, vascular calcification is now accepted as a valuable predictor of coronary heart disease.  Achieving control over this process requires understanding mechanisms in the context of a tightly controlled regulatory network, with multiple, nested feedback loops and cross talk between organ systems, in the realm of control theory.  Thus, treatments for osteoporosis such as calcitriol, estradiol, bisphosphonates, calcium supplements, and intermittent PTH are likely to affect vascular calcification, and, conversely, many treatments for cardiovascular disease such as statins, antioxidants, hormone replacement therapy, angiotensin-converting enzyme inhibitors, fish oils, and calcium channel blockers may affect bone health. As we develop and use treatments for cardiovascular and skeletal diseases, we must give serious consideration to the implications for the organ at the other end of the bone-vascular axis.

Ewence AE, Bootman M, Roderick HL, Skepper JN, McCarthyG, et al.  Calcium phosphate crystals induce cell death in human vascular smooth muscle cells:  A potential mechanism in atherosclerotic plaque destabilization.  Circulation Res.  2008;103:328-34.

Schurgers LJ, Cranenburg ECM, Vermeer C.  Matrix Gla-protein: the calcification inhibitor in need of vitamin K.  Thromb Haemost.  2008;100:593-603.   
Among the proteins involved in vascular calcium metabolism, the vitamin K-dependent matrix Gla-protein (MGP) plays a dominant role.  Its pivotal importance for vascular health is demonstrated by the fact that there seems to be no effective alternative mechanism for calcification inhibition in the vasculature.  An optimal vitamin K intake is therefore important to maintain the risk and rate of calcification as low as possible.  Significant differences were found in patients with cardiovascular disease (CVD).  Using ELISA-based assays, uncarboxylated MGP (ucMGP) was demonstrated to be a promising biomarker for cardiovascular calcification detection. These assays may have potential value for identifying patients as well as apparently healthy subjects at high risk for CVD and/or cardiovascular calcification and for monitoring the treatment of CVD and vascular calcification.

Shearer MJ, Newman P.  Metabolism and cell biology of vitamin K.  Thromb Haemost.  2008;100:530-47.
Structural differences in vitamin K compounds govern many facets of the metabolism of K vitamins, including the way they are transported, taken up by target tissues, and subsequently excreted.  In the post-prandial state, phylloquinone is transported mainly by TRL, and long-chain menaquinones mainly by LDL.  One K2 form, MK4, has a highly specific tissue distribution suggestive of local synthesis.  MK4 specifically upregulates two genes suggesting a novel MK4 signalling pathway.  Many studies have shown clinical benefits of MK4 at pharmacologic doses for osteoporosis and cancer.  Vitamin K also functions to suppress inflammation, prevention of brain oxidative damage, and a role in sphingolipid synthesis.  Anticoagulant drugs block vitamin K recycling and reduce the availability.  A daily supplement of K2 shows potential to improve coagulation control.

Westenfeld R, Kruger T, Schlieper G, et al.  Vitamin K2 supplementation reduces the elevated inactive form of the calcification inhibitor matrix gla protein in hemodialysis patients.  Am Soc Nephrol.  2008;TH-FC044.

Demer LL, Tintut Y.  Vascular calcification:  Pathobiology of a multifaceted disease.  Circulation.  2008;117:2938-48. 

Erkkila AT, Booth SL.  Vitamin K intake and atherosclerosis.  Curr Opin Lipidol.  2008;19(1): 39-42. 
Found menaquinone (vitamin K2) but not K1 intake to be associated with reduced risk of CHD mortality, all cause mortality and severe aortic calcification. 

Schurgers LJ, Cranenburg EC, Vermeer C.  Matrix Gla-protein: the calcification inhibitor in need of vitamin K.  Thromb Haemost.  2008 Oct:100(4):593-03.
Among the proteins involved in vascular calcium metabolism, the vitamin K-dependent matrix Gla-protein (MGP) plays a dominant role.  Although on a molecular level its mechanism of action is not completely understood, it is generally accepted that MGP is a potent inhibitor of arterial calcification.  An optimal vitamin K intake is therefore important to maintain the risk and rate of calcification as low as possible.  Using ELISA-based assays, uncarboxylated MGP (ucMGP) was demonstrated to be a promising biomarker for cardiovascular calcification detection.

Wallin R, Schurgers L, Wajih N.   Effects of the blood coagulation vitamin K as an inhibitor of arterial calcification.  Thromb Res.  2008;122(3):411. 
Our findings suggest that MK4 could inhibit vessel wall calcification.  Our data from the MK4 gene expression studies are supportive of the current use of MK4 in medicine.  MK4 has been shown conclusively to reduce osteoporosis and has been used for this purpose in Japan for several years.  MK4 intake has also been reported reduce aortic calcification.

Alexopolous N, Raggi P.  Calcification in atherosclerosis.  Nat Rev Cardiol.  2009;6:681-88. 

Beulens JW, Bots ML, Atsma F, Bartelink ML, Prokop M,  Geleijnse JM, et al.  High dietary menaquinone intake is associated with reduced coronary calcification.  Atherosclerosis.  2009 Apr;203(2):489-93.
A high dietary intake of menaquinone, vitamin K2, was found to be associated with decreased coronary calcification in 564 post menopausal women.  Researched the association between the intake of both phylloquinone and menaquinone, including its subtypes (MK4-MK10) with coronary calcification in a cross-sectional study among 564 post-menopausal women.  Intake was estimated using a food frequency questionnaire.  Menaquinone intake was associated with decreased coronary calcification.  They concluded that adequate menaquinone intakes could therefore be important to prevent cardiovascular disease

Danziger J.  Vitamin K-dependent proteins, warfarin, and vascular calcification.  Clin J Am Soc Nephrol.  2009 Sep;3(5):1504-10.
Vitamin K dependent proteins (VKDP) require carboxylation to be come biologically active.  Matrix Gla Protein (MGP) and Growth Arrest Specific Gene 6 (Gas-6) are two important VKDPs and their roles in vascular biology are just beginning to be understood.  Both function to protect the vasculature.  MGP prevents vascular calcification and Gas-6 affects vascular smooth muscle cell aptosis and movements.  Warfarin prevents the activation of these proteins and in animals, induces vascular calcification.  Given the high risk of vascular calcification in patients with kidney disease, it will be important to research warfarin’s effect on VKDPs. 

Gast GCM, de Roos NM,, Sluijs I, Bots ML, Beulens JWJ, Geleijnse JM, et al.  A high menaquinone intake reduces the incidence of coronary heart disease.  Nutri, Metab & Cardiov Diseases.  2009;19(7):504-10.
Vitamin K dependent proteins inhibit vascular calcification.  However there is limited data on the effect of vitamin K intake on coronary heart disease (CHD) risk.  This study looked at the relationship between dietary vitamins K1 and K2 intake and the incidence of CHD, using data from the Prospect-EPIC cohort consisting of 16,057 women, aged 49-70 years who were free of CHD at baseline.  The results indicated an association between vitamin K2 subtypes MK7, MK8 and MK9.  Vitamin K1 intake was not significantly related to CHD.  The results from this study how that high intake of natural vitamin K2, menaquinones, over an 8 year period protected from cardiovascular events and CHD, with more research necessary to define optimal intake levels.  The researchers found that for every 10 mcg vitamin k2 consumed, the risk of coronary heart disease was reduced by 9%.  This supported the Rotterdam Study findings. 

Krueger T, Westenfield R, Schurgers L, Brandenburg V.  Coagulation meets calcification:  The vitamin K system.  Int J Artif Organs.  2009;32:67-74. 
Morbidity and mortality are massively increased in patients with chronic kidney disease (CKD) and patients with end-stage renale disease (ESRD).  Bone disease (renal osteodystrophy) and vascular disease (accelerated arteriosclerosis) are two typical entities contributing to this excess morbidity and mortality. Vitamin K and vitamin K-dependent-proteins play pivotal roles in the physiology of mineralization and in preventing ectopic calcification.  Vitamin K deficiency impairs the physiological function of osteocalcin and MGP and, therefore, presumably contributes to bone demineralisation and vascular calcification (the so-called calcification paradox).  We present a summary of data describing the potential role of vitamin K deficiency and supplementation in bone and vascular disease in patients with CKD or ESRD.

Rennenberg RJMW, Kells AGH, Schurgers LJ, van Engelshoven JMA, de Leeuw PW, et al.  Vascular calcifications as a marker of increased cardiovascular risk:  A meta-analysis.  Vasc Health and Risk Managemt.  2009;5:185-97. 

Shea MK, O’Donnell CJ, Hoffman U, Dallal GE, Dawson-Hughes B, Ordovas JM, et al.  Vitamin K supplementation and progression of coronary artery calcium in older men and women.  Am J Clin Nutr.  2009 June;89(6):1799-07. 
Coronary artery calcification (CAC) is an independent predictor of cardiovascular disease.  A preventive role for vitamin K in CAC progression has been proposed on the basis of the properties of matrix Gla protein (MGP) as a vitamin K–dependent calcification inhibitor.  The objective was to determine the effect of phylloquinone (vitamin K1) supplementation on CAC progression in older men and women.  CAC was measured at baseline and after 3 years of follow-up in 388 healthy men and postmenopausal women; 200 received a multivitamin with 500 μg phylloquinone per day (treatment), and 188 received a multivitamin alone (control).  Phylloquinone-associated decreases in CAC progression were independent of changes in serum MGP. MGP carboxylation status was not determined.  Phylloquinone supplementation slows the progression of CAC in healthy older adults with preexisting CAC, independent of its effect on total MGP concentrations.

Speer MY, Yang H-Y, Brabb T, Leaf E, Look A, et al.  Smooth muscle cells give rise to osteochondrogenic precursors and chondrocytes in calcifying arteries.  Circ Res.  2009;104:733-41.

Suttie, John W.  Vitamin K in health and disease. CRC Press. 2009.

Viegas C, Cavaco S, Neves P, et al.  Gla-rich protein is a novel vitamin K-dependent protein present in serum that accumulates at sites of pathological calcifications.  Am J Pathol.  2009;175:2288-98. 
We have recently identified in sturgeon a new VKD protein, Gla-rich protein (GRP), which contains the highest ratio between number of Gla residues and size of the mature protein so far identified.  We show that GRP is a circulating protein that is also expressed and accumulated in soft tissues of rats and humans, including the skin and vascular system, when affected by pathological calcifications.  The high number of Gla residues and consequent mineral binding affinity properties strongly suggest that GRP may directly influence mineral formation, thereby playing a role in processes involving connective tissue mineralization.

2010s

Cranenburg ECM, Koos R, Schurgers LJ, et al.  Characterisation and potential diagnostic value of circulating matrix Gla protein (MGP) species.  Thromb Haemost 2010;104:811-22. 
Matrix γ-carboxyglutamate (Gla) protein (MGP) is an important local inhibitor of vascular calcification, which can undergo two post-translational modifications: vitamin K-dependent γ-glutamate carboxylation and serine phosphorylation.  While carboxylation is thought to have effects upon binding of calcium ions, phosphorylation is supposed to affect the cellular release of MGP.  Since both modifications can be exerted incompletely, various MGP species can be detected in the circulation.  MGP levels were measured in patients with rheumatic disease, aortic valve disease, and end-stage renal disease, as well as in volunteers after vitamin K supplementation (VKS) and treatment with vitamin K antagonists (VKA).  Major differences were found between the MGP assays, including significantly different behaviour with regard to vascular disease and the response to VKA and VKS.  The dual-antibody assay measuring non-phosphorylated, non-carboxylated MGP (dp-ucMGP) was particularly sensitive for these changes and would be suited to assess the vascular vitamin K status.

Finn AV, Nakano M, Narula J, Kolodgie FD, Virmani R.  Concept of vulnerable/unstable plaque.  Arterioscler Thromb VascBiol.  2010 July;30(7): 1282–92.

Nakagawa Y, Ikeda K, Akakabe Y, Koide M, Uraoka M, et al.  Paracrine osteogenic signals via bone morphogenetic protein-2 accelerate the atherosclerotic intimal calcification in vivo.  Arterioscler Thromb Vasc Biol.  2010;30:1908-15.
We generated BMP-2-transgenic mice and crossed them with apoE-deficient mice (BMP-2-transgenic/apoE-knockout).  Significantly accelerated atherosclerotic intimal calcification was detected in BMP-2-transgenic/apoE-knockout mice, although serum lipid concentration and atherosclerotic plaque size were not different from those in apoE-knockout mice.  Enhanced calcification appeared to be associated with the frequent emergence of osteoblast-like cells in atherosclerotic intima in BMP-2-transgenic/apoE-knockout mice.  The findings collectively demonstrate an important role of dedifferentiated VSMCs in the pathophysiology of atherosclerotic calcification through activating paracrine BMP-2 osteogenic signals.

Nasir K, Rivera JJ, Yoon YE, Chang SA, Choi SI, Chun EJ, et al.  Variation in atherosclerotic plaque composition according to increasing coronary artery calcium scores on computed tomography angiography.  Int J Cardiovasc Imaging.  2010;26:923-32. 
Absence of CAC (Coronary Artery Calcium) is associated with a negligible presence of any atherosclerotic disease as detected by Coronary Computed Tomagraphy Angiography in 1043 asymptomatic South Korean population.  A higher CACS is more likely to be associated with heterogeneous coronary plaque (combination of calcified, non-calcified, and mixed plaques), and appears to be more strongly associated with a higher burden of mixed plaque.

Reed K, Guraew al S, Wong YL, Majanbu DL, Mavrodaris A, Stranges S, et al.  Is vitamin K consumption associated with cardio-metabolic disorders?  A systematic review.  Maturitas.  2010 Oct;67(2):121-28.
The study examined the association between vitamin K intake and cardio-metabolic outcomes including cardiovascular disease, type 2 diabetes and metabolic syndrome.  A systematic review of the literature produced five studies.  Due to the heterogeneity of designs, the exposures/interventions and outcomes, it was not possible to do a meta-analysis.  In these studies, no associations were found between vitamin K2 intake and coronary heart disease (CHD) or stroke, or prevalence of diabetes.  Two cohorts found significant associations where higher vitamin K2 intake was associated with fewer CHD events. 

Rennenberg RJMW, van Varik BJ, Schurgers LJ, Hamulyak K, Ten Cate H, et al.  Chronic coumarin treatment is associated with increased extracoronary arterial calcification in humans.  Blood.  2010;115:5121-123.
Because MGP activation is vitamin K dependent, we performed a cross-sectional study investigating the relationship between the use of vitamin K antagonists and extracoronary vascular calcification.  From the Dutch thrombosis services we selected 19 patients younger than 55 years who had no other cardiovascular risk factors and who had used coumarins for more than 10 years, and compared these to 18 matched healthy controls.  MGP was measured, and a plain x-ray of the thighs was taken to assess femoral arterial calcifications.  The odds ratio for calcification in patients versus controls was 8.5 (95% confidence interval [CI] 2.01-35.95).  Coumarin use and MGP were associated with calcification, even after adjusting for other risk factors.  We conclude that long-term use of coumarins is associated with enhanced extracoronary vascular calcification.

Rennenberg RJ, de Leeuw PW, Kessels AG, Schurgers LJ, Vermeer C, van Engelshoven JM, et al.  Calcium scores and matrix Gla protein levels: Association with vitamin K status.  Eur J Clin Invest.  2010 Apr;40(4):344-9.
Carboxylated matrix Gla protein (cMGP) inhibits vascular calcification.  Vitamin K is an essential cofactor to activate the matrix Gla protein so that it prevents calcification.  They hypothesized that arterial calcification and a low vitamin K status, measured by the osteocalcin ratio, would be associated with ucMGP.  The study found a positive association between the total arterial calcium score and a high osteocalcin ratio (OCR) (which reflects low vitamin K status) with ucMGP levels in the blood. 

Ueland T, Gullestad L, Dahl CP, Aukrust P, Aakhus S, Solberg OG, et al.  Undercarboxylated matrix Gla protein is associated with development of heart failure and mortality in symptomatic aortic stenosis.  J Int Med.  2010;268:483-92. 

Yao Y, Bennett BJ, Wang X, Rosenfeld ME, Giachelli C, et al.  Inhibition of bone morphogenetic proteins protects against atherosclerosis and vascular calcification.  Circ Res.  2010;107:485-94. 
The bone morphogenetic proteins (BMPs), a family of morphogens, have been implicated as mediators of calcification and inflammation in the vascular wall.  Their results indicate that BMP (Bone Morphogenic Protein) signaling is a key regulator of vascular disease, requiring careful control to maintain normal vascular homeostasis.

Chatrou ML, Reutelingsperger CP, Schurgers LJ.  Role of vitamin K-dependent proteins in the arterial vessel wall.  Hamostaseologie.  2011;31:251-57. 
Vitamin K-dependent proteins are involved in the regulation of vascular smooth muscle cell migration, apoptosis, and calcification.  Vascular calcification has become an important independent predictor of cardiovascular disease.  Vitamin K-antagonists induce inactivity of inhibitors of vascular calcification, leading to accelerated calcification.  The involvement of vitamin K-dependent proteins such as MGP in vascular calcification mean that calcification is amenable for intervention with high intake of vitamin K.

Derlin T, Wisotzki C, richter U, et al.  In vivo imaging of mineral deposition in carotid plaque using 184_sodium fluoride PET/CT:  Correlation with atherogenic risk factors.  J Nucl Med.  2001; 52:362-68. 

Hurtado B, Munoz X, Recarte-Pelz P, Garcia N, Luque A, Krupinski J, et al.  Expression of the vitamin K-dependent proteins GAS 6 and protein S and the TAM receptor tyrosine kinases in human atherosclerotic carotid plaques.  Thrombosis and Haemostasis.  2011 May;105(5):873-82.

O’Young J, Liao Y, Xiao Y, Jalkanen J, Lajoie G, et al.  Matrix gla Protein inhibits ectopic calcification by a direct interaction with hydroxyapatite crystals.  J Am Chem soc.  2011;133:18406-412.

Palaniswamy C, Sekhri A, Aronow WS, Kalra A, Peterson SJ.  Assocation of warfarin use with valvular and vascular calcification:  A review.  Clin Cardiol.  2011;34(2):74-81. 
Vitamin K is required for the activity of various biologically active proteins in our body.  Apart from clotting factors, vitamin K-dependent proteins include regulatory proteins like protein C, protein S, protein Z, osteocalcin, growth arrest-specific gene 6 protein, and matrix Gla protein.  Glutamic acid residues in matrix Gla protein are γ-carboxylated by vitamin K-dependent γ-carboxylase, which enables it to inhibit calcification. Warfarin, being a vitamin K antagonist, inhibits this process, and has been associated with calcification in various animal and human studies.  Drugs including statins, alendronate, osteoprotegerin, and vitamin K are currently under study as therapies to prevent or treat warfarin-associated calcification.

Roijers RB, Debernardi N, Cleutjens JP, Schurgers LJ, Mutsaers PH, et al.  Microcalcifications in early intimal lesions of atherosclerotic human coronary arteries.  The Am J of Path.  2011;178:2879-87. 

Schlieper G, Westenfeld R, Kruger T, Cranenburg EC, Magdeleyns EJ, Brandenburg VM, et al.  Circulating nonphosphorylated carboxylated matrix gla protein predicts survival in ESRD.  J Am Soc Nephrol.  2011 Feb;22(2):387-95.
Dialysis patients exhibit profound vitamin K deficiency which may impair carboxylation of the calcification inhibitor matrix gla protein (MGP).  The study tested whether distinct circulating inactive vitamin K-dependent proteins are associated with all-cause or just cardiovascular mortality.  They compared hemodialysis patients with subjects with normal renal function.  They found pronounced vitamin K deficiency in the dialysis patients, and a Kaplan-Meier analysis showed that these patients had an increased risk for both all-cause and for cardiovascular mortality. 

Weijs B, Blaauw Y, Rennenberg RJMW, Schurgers LJ, Timmermans CCMM, et al.  Patients using vitamin K antagonists show increased levels of coronary calcification:  An observational study in low-risk atrial fibrillation patients.  European Heart J.  2011;32:2555-62. 

Zak-Golab A, Okopien B, Chudek J.  Vitamin K, bone metabolism and vascular calcification in chronic kidney disease.  Przegl Lek.  2011;68(9):629-32. 
Atherosclerosis is the main cause of premature death in patients with chronic kidney disease, especially if on dialysis.  Vitamin K dependent proteins play an essential role in the pathogenesis of mineral and bone disorders related to kidney disease, including vascular calcification.  Vitamin K dependent proteins require carboxylation for biological activation.  The role of matrix Gla protein (MGP), Growth Arrest Specific Gene 6 (Gas-6) and osteocalcin has been recently discovered.  MGP prevents vascular calcification and Gas-6 affects vascular smooth muscle cell apoptosis and movement. Carboxylation of osteocalcin promotes bone formation.  The restrictive diet recommended for dialysis patients increases the chance for vitamin K deficiency.  More research needs to be done on the clinical consequences of vitamin K deficiency for the peripheral tissues. 

Chatrou ML, Winckers K, Hackeng TM, Reutelingsperger CP, Schurgers LJVascular calcification: the price to pay for anticoagulation therapy with vitamin K-antagonists.  Blood Rev. 2012 Jul;26(4):155-66.
Vitamin K-antagonists (VKA) are the most widely used anti-thrombotic drugs.  Several lines of evidence indicate, however, that vascular calcification is one of the side-effects of VKA.  Vascular calcification is an actively regulated process involving vascular cells and a number of vitamin K-dependent proteins.  This review addresses vitamin K-cycle and vitamin K-dependent processes of vascular calcification that are affected by VKA.  We conclude that there is a growing need for better understanding of the effects of anticoagulants on vascular calcification and atherosclerosis.

Dalmeijer GW, van der Schouw YT, Vermeer, C, Magdeleyns, EJ, Schurgers LJ, Beulens JWJ.  Circulating matrix Gla protein is associated with coronary artery calcification and vitamin K status in healthy women.  J of Nutri Biochem. July 2012. 
This cross-sectional study investigated the association of Matrix Gla Protein (MGP) with coronary artery calcification and vitamin K status among 200 healthy women.  The ratio of uncarboxylated to carboxylated osteocalcin was used a proxy of vitamin K status.  The results showed that circulating levels of uncarboxylated MGP may serve as a biomarker of vitamin K status, and may also be a reflection of coronary artery calcification status.


Holmes MV, Hunt BJ, Shearer MJ.  The role of dietary vitamin K in the management of oral vitamin K antagonists.  Blood Reviews.  2012 Jan;26(1):1-14
.  

Preliminary evidence suggests that the stability of anticoagulation therapy may be improved by daily vitamin K supplementation, but further studies are needed whether this, or other dietary interventions can improve anticoagulant control in routine clinical practice.

Jia G, Stormont RM, Gangahar DM, Agrawal DK.  Role of matrix Gla protein in angiotensin II-induced exacerbation of vascular calcification.  Am J Physiol Heart Circ Physiol.  2012;303(5):H523-H532.
Recently, angiotensin II (ANGII) was found to play a key role in vascular calcification with both growth-promoting and inflammatory effects.  This study investigated the effect of matrix Gla-protein in vascular calcification induced by ANG II in human vascular smooth muscle cells.  The results found three new functions for MGP:  inhibition of calcium deposition, suppression of inflammation, and increase in cell survival.

Naik V, Leaf EM, Hu JH, Yang H-Y, Nguyen NB, et al.  Sources of cells that contribute to atherosclerotic intimal calcification:  an in vivo genetic fate mapping study.  Cardiovascular Research.  2012;94:545-554. 

Schurgers LJ, Joosen IA, Laufer EM, Chatrou MLL, Herfs M, et al.  Vitamin K-antagonists accelerate atherosclerotic calcification and induce a vulnerable plaque phenotype.  PlosS ONE 7(8):e43229.  Available at www.plosone.org/article/info:doi/10.1371/journal.pone.0043229.
Studied groups of patients using vitamin K antagonists (VKA), such as Coumadin, and those who were not using VKA.  The results indicate that VKA use is associated with an increase of atherosclerotic plaque calcification.  The study demonstrated that VKA treatment is associated with accelerated calcification of atherosclerotic plaques in humans, and demonstrated in a mouse model that VKA affects plaque negatively by making plaques more unstable and vulnerable to rupture.        

Theuwissen E, Smit E, Vermeer C.  The role of vitamin K in soft-tissue calcification.  Adv Nutr March 2012;3:166-73. 
Seventeen vitamin K-dependent proteins have been identified to date of which several are involved in regulating soft-tissue calcification.  Osteocalcin, matrix Gla protein (MGP), and possibly Gla-rich protein are all inhibitors of soft-tissue calcification and need vitamin K-dependent carboxylation for activity.  MGP is synthesized by vascular smooth muscle cells and is the most important inhibitor of arterial mineralization currently known.  Remarkably, the extrahepatic Gla proteins mentioned are only partly carboxylated in the healthy adult population, suggesting vitamin K insufficiency.  Because carboxylation of the most essential Gla proteins is localized in the liver and that of the less essential Gla proteins in the extrahepatic tissues, a transport system has evolved ensuring preferential distribution of dietary vitamin K to the liver when vitamin K is limiting.  This is why the first signs of vitamin K insufficiency are seen as undercarboxylation of the extrahepatic Gla proteins.  Vitamin K intervention studies have shown that MGP carboxylation can be increased dose dependently, but thus far only 1 study with clinical endpoints has been completed.  This study showed maintenance of vascular elasticity during a 3-y supplementation period, with a parallel 12% loss of elasticity in the placebo group.  More studies, both in healthy subjects and in patients at risk of vascular calcification, are required before conclusions can be drawn.

Chatrou MLL, Winckers K, Hackeng TM, Reutlingsperger CP, Schurgers LJ. Vascular calcification: The price to pay for anticoagulation therapy with vitamin K-antagonists.  Blood Rev.  2012; Jul;26(4):155-66.
Vitamin K-antagonists (VKA) are the most widely used anti-thrombotic drugs with substantial efficacy in reducing risk of arterial and venous thrombosis.  Several lines of evidence indicate, however, that VKA inhibit not only post-translational activation of vitamin K-dependent coagulation factors but also prevent the synthesis of functional extra-hepatic vitamin K-dependent proteins thereby eliciting undesired side-effects.  Vascular calcification is one of the recently revealed side-effects of VKA.  Vascular calcification is an actively regulated process involving vascular cells and a number of vitamin K-dependent proteins.  This review addresses the vitamin K-cycle and vitamin K-dependent processes of vascular calcification that are affected by VKA.  We conclude that there is a growing need for better understanding of the effects of anticoagulants on vascular calcification and atherosclerosis.

Dalmeijer GW, van der Schouw YT, Magdeleyns E, Ahmed N, Vermeer C, Beulens JWJ.  The effect of menaquinone-7 supplementation on circulating species of matrix Gla protein.  Atherosclerosis.  2012 Dec;225(2):397-402.
A randomized, double-blind, placebo controlled trials was conducted to investigate whether MK7 supplementation increased the carboxylation of matrix Gla protein.  Participants were randomly allocated to receive a placebo, 180 ug, or 140 ug of MK7 for twelve weeks.  The results showed that those who received the MK7 increased the amount of carboxylated MGP circulating in their blood, by 31% and 46%.  These changes were evident within four weeks of beginning supplementation.    

Kruger T, Oelenberg S, Kaesler N, Schurgers LJ, van de Sandt AM, Boor P, et al.  Warfarin induces cardiovascular damage in mice.  Arerioscl, Thromb and Vasc Biol. 2013;33:2618-2624.
We know that vascular calcification is actively prevented by proteins acting systemically (fetuin-A) or locally (matrix Glal protein).  Warfarin is widely prescribed to reduce coagulation but it also interferes with vitamin K and its activation of proteins that prevent calcification, particularly matrix Gla protein.  In this study, warfarin was given to mice, and calcification was rapidly induced in the aorta and the heart.  At the same time, matrix Gla protein gene expression decreased and inactive matrix Gla protein expression increased. Administering vitamin K2 reduced the development of calcification, but did not change the gene expression that had been triggered.

Reid IR.  Cardiovascular effects of calcium supplements.  Nutrients.  2013;5(7):2522-2529.  
A meta-analysis of trials with calcium supplements was conducted to assess their safety.  This meta-analysis found a 27-31% increase in risk of myocardial infarction and a 12-20% increase in risk of stroke for folks taking calcium supplements.  Administering the calcium with vitamin D did not lessen the adverse effects.  They concluded from the data, that the risks of calcium supplements outweigh any skeletal benefits and that calcium supplements appear to be unnecessary for the efficacy of other osteoporosis treatments.  

Schurgers LJ, Uitto J, Reutelingsperger CP.  Vitamin K-dependent carboxylation of matrix Gla-protein:  a crucial switch to control ectopic mineralization.  Trends in MOl Med.  2013 Apr;19(4):217-226.
Vascular mineralization is currently recognized as an actively regulated process with cellular and humoral contributions.  It is also a risk factor for cardiovascular morbidity and mortality.  This review focuses on molecular mechanisms of vascular mineralization involving matrix Gla protein, which is a strong inhibitor of vascular calcification, and discusses the potential for treatments.  

Shea MK, Booth SL, Miller ME, Burke GL, Chen H, Cushman M, et al. Association between circulating vitamin K1 and coronary calcium progression in community-dwelling adults:  the Multi-Ethnic Study of Atherosclerosis.  Am J Clin Nutr.  2013;98:197-208.  
This study tested the hypothesis that low vitamin K status is associated with greater coronary artery calcification over a 2.5 year follow up.  The 850 participants were part of the MESA cohort, which is an ongoing study of coronary vascular disease.  Low vitamin K status was associated with a 34% higher odds of extreme CAC progress.  The most notable finding was that folks taking antihypertensive medication were more than twice as likely to have extreme CAC progress if they had low serum vitamin K1.  The hypertensive meds involved were primarily ACE inhibitors and thiazide diuretics.  Given that one in five adults in the USA are treated for hypertension, and about half of all US adults may have low vitamin K status, the researchers called for intervention trials to determine whether improving vitamin K status reduces CAC progress for people being treated for hypertension.  

Theuwissen E, Badmaev V, Vermeer C.  Calcium intake and cardiovascular disease mortality:  Is there a critical role for vitamin K?  JAMA Internal Medicine.  2013;173:1841.
In a comment on other research published on calcium intake, these authors report that arterial calcification is an actively regulated process with a key function for vitamin K-dependent matrix Gla protein.  Mature MGP is a powerful inhibitor of soft-tissue calcification and is abundantly expressed by vascular smooth muscle cells.  Calcium supplements have been widely used for the prevention and treatment of osteoporosis.  However, when nutritional vitamin K intake is low, the vitamin K-dependent proteins involved in calcium homeostasis are only partly activated, resulting in suboptimal control of tissue mineralization: one of the consequences may be excessive mineralization of the arteries.  Recent studies demonstrate that MGP carboxylation can be improved significantly with supplemental vitamin K2 (menaquinone) thus eliminating uncarboxylated MGP.  They recommend that vitamin K intake or MGP carboxylation be included as a potential confounder when analyzing the association between calcium intake and cardiovascular disease.  The use of calcium with vitamin D supplements clearly increases the calcium load of the body and may need optimal control of calcium homeostasis.

Theuwissen E, Teunissen KJ, Srponk HMH, Hamulyak K, Ten Cate H, Shearer MJ, et al.  Effect of low-dose supplements of menaquinone-7 (vitamin K2) on the stability of oral anticoagulant treatment: dose-response relationship in healthy volunteers.  J of Thrombosis and Haemotosis.  2013 Jun;11(6):1085-1092.

Dalmeijer GW, van de Schouw YT, Booth SL, de Jong PA, Beulens JWJ.  Phylloquinone concentrations and the risk of vascular calcification in healthy women.  Arterioscler Thromb Vasc Biol.  2014;34:1587-90.
Observational studies consistently show that high intakes of menaquinone are associated with reduced arterial calcification and cardiovascular disease risk.  However, these studies do not show the association between phylloquinone intake and the incidence of cardiovascular disease.  This study attempts to elucidate the impact of phylloquinone intake on a cohort of 508 postmenopausal women, as to vascular calcification.  The results did not show reduced vascular calcification, but the dosages in the study were quite a bit lower, suggesting that the protective effect of K1 can only be reached by taking supplements and not only with dietary intake.


 El Asmar MS, Naoum JJ, Arbid EJ.  Vitamin K dependent proteins and the role of vitamin K2 in the modulation of vascular calcification:  a review.  Oman Med J.  2014 May;29(3):172-7.
Vascular calcification is an actively regulated process involving vitamin K dependent proteins (VKDPs).  The factors involved in the regulation of calcification are being studied, including matrix Gla protein (MGP) and vitamin K2 or menaquinones.  Vitamin K2 has been shown to exhibit profound effects on reducing vascular calcification and has promising potential to be used as a treatment prevention for vascular calcification.  Clinical trials studying the effect of VK2 on preventing calcification are underway.  In recognition of the promise of VK2 on reducing the risk of heart disease, the International Life Science Institute (ILSI Europe) recommends that the amount of VK2 be considered in addition to VK1, when calculating the daily recommended value of vitamin K.

Juanola-Falgarona M, Salas-Salvado J, Martinez-Gonzalez MA, Corella D, Estruch R, Ros E, Fito M, et al.  Dietary intake of vitamin K is inversely associated with mortality risk.  J Nutr.  2014.  jn.113.1877740; first published online March 29, 2014.
A controlled trial assessed the association between the dietary intake of different types of vitamin K and mortality in a Mediterranean population at high cardiovascular risk. They found that vitamin K (phylloquinone) intake was inversely associated with a significantly reduced risk of cancer and all-cause mortality.  People who increased their intake of vitamin K1 or K2 (menaquinone) during follow-up had a lower risk of cancer and all-cause mortality when compared to people who decreased or did not change their intake.  Also people who increased their intake of vitamin K1 had a lower risk of cardiovascular mortality.

Mayer O Jr.  Seidlerova J, Bruthans J, Filipovsky J, Timoracka K, Vanek J et al.  Dephospho-uncarboxylated matrix Gla-protein is associated with mortality risk in patients with chronic stable vascular disease.  Atherosclerosis.  2014 Jul;235(1):162-8.
Vitamin K is the essential co-factor for activation of matrix Gla protein, the natural inhibitor of tissue calcification.  Dephospho-uncarboxylated MGP (dp-ucMGP) is a marker of vascular vitamin K status and is described to predict mortality in patients with heart disease and aortic stenosis.  dp-ucMGP reflects low dietary intake of vitamin K resulting in less efficient inhibition of calcification.  This study followed 799 patients who suffered from heart events in a cohort study for more than five years.  They found that circulating dp-ucMGP and dp-cMGP were independently associated with all-cause and cardiovascular mortality.  Patients who had high levels of dp-ucMGP (meaning vitamin K intake was too low) had a 90% increase of death in five years.  They concluded that high levels of dp-ucMGP is a risk marker for cardiovascular disease.

van den Heuvel EGHM, van Schoor NM, Lips P, Magdeleyns EJP, Deeg DJH, Vermeer C, et al.  Circulating uncarboxylated matrix Gla protein, a marker of vitamin K status, as a risk factor of cardiovascular disease.  Maturitas.  2014 Feb;77(2):137-41.
Vitamin K plays a pivotal role in the synthesis of matrix Gla protein (MGP), a calcification inhibitor in vascular tissue.  Vascular calcification has become an important predictor of cardiovascular disease.  The aim of this current study was to examine the potential association of circulating dephosph-carboxylated and uncarboxylated MGP, reflecting vitamin K status, with the incidence of cardiovascular events and disease (CVD) in older individuals.  577 community dwelling older men and women of the Longitudinal Aging Study Amsterdam (LASA), aged >55 years, who were free of cardiovascular disease at baseline were followed for 5.6 years, and 40 incident cases of CVD were identified.  They concluded that vitamin K insufficiency, as assessed by high plasma dp-ucMGP concentration is associated with increased risk for cardiovascular disease, independent of classical risk factors and vitamin D status.  They recommended larger epidemiological studies followed by clinical trials to test whether vitamin K-rich diets will lead to a decreased risk for cardiovascular events.

Viegas CSB, Rafael MS, Enriquez JL, Teixeira A, Vitorino R, Luis IM, et al.  Gla-rich protein acts as a calcification inhibitor in the human cardiovascular system.  Arteriosclerosis, Thrombosis & Vascular Biology.  Published online before print, December 23, 2014.
Vascular calcifications are pathological processes regulated by a complex interplay between calcification promoters and inhibitors, resembling skeletal metabolism.  This study examined the role of vitamin K dependent Gla-rich proteins (GRP) in vascular and valvular calcification processes.  Using an ex vivo model of vascular calcification, carboxylated GRP, but not undercarboxylated GRP was shown to inhibit calcification and osteochondrogenic differentiation.  They concluded that GRP is an inhibitor of vascular and valvular calcification and is involved in calcium homeostasis, dependent on the availability of vitamin K for carboxylation.  

Willems BAG, Vermeer C, Reutelingsperger CPM, Schurgers LJ.  The realm of vitamin K dependent proteins:  shifting from coagulation toward calcification.  Molec Nutri & Food Research.  2014 Aug;58(8):1620-35.  
In the past few decades, vitamin K has emerged from a single-function "haemostasis vitamin " to a "multi-function vitamin".  More than 14 proteins have been identified that depend on vitamin K and they fall into two groups; hepatic, which are involved in blood coagulation, and extrahepatic, which are involved with other bodily tissues outside of the liver.  Proteins that depend on vitamin K are involved in pathological calcification.  A deficiency of vitamin K entails the risk of soft tissue calcification and vascular disease.  Research results suggest that the use of vitamin K is potentially beneficial in attenuating the progression of vascular calcification and several outcome trials are currently underway.  

Brandenburg VM, Schurgers LJ, Kaesler N, Pusche K, van Gorp RH, Leftheriotis G, Reinartz S, et al.  Prevention of vasculopathy by vitamin K supplementation:  can we turn fiction into fact?  Atherosclerosis.  May 2015;240(1):10-16.
Vitamin K is a key factor in the regulation of bone and soft tissue calcification (due to its ability to activate matrix Gla protein.  Data from experimental animal models reveal that high intake of vitamin K can prevent and even reverse vascular calcifications.  Clinical data indicate that taking vitamin K antagonists, such as warfarin can accelerate vascular calcification.  No negative events were recorded even when 45 mg vitamin K2 were taken daily for three years in 2185 postmenopausal osteoporotic women.

Demer LL, Bostrom KI.  Editorial: Conflicting forces of warfarin and matrix Gla protein in the artery wall.  Arteriosclerosis, Thrombosis and Vascular Biology.  2015;35:9-10.
14 years ago it was discovered that after only 2 weeks of warfarin treatment, rats presented with massive calcification of the artery wall.  The phenomenon was so robust that warfarin was often used to create calcification experimentally in the lab.  There continues to be ample evidence that vascular calcification is greater in women taking warfarin and that it only increases.  Over time, research has clarified the mechanisms by which warfarin interferes with vitamin K, which interferes with the function of matrix Gla protein, which is a key inhibitor of arterial mineralization or calcification.  Warfarin also increases the risk of developing arterial malformations (AVMs) in mice.  While there are some clinical benefits of warfarin in preventing blood clot events, there are now alternative anticoagulants that do not interfere with the benefits of vitamin K.  Further clinical research on those alternatives are now warranted.

Knapen MHJ, Braam LAJLM, Drummen NE, Bekers O, Hoeks APG, Vermeer C.  Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women:  double-blind randomised clinical trial.  Thromb Haemost.  2015 (Feb 19);113(5).  epub ahead of print.
This study investigated long-term effects of MK7 supplementation (180 ug/day) on arterial stiffness in a double-blind, placebo-controlled trial.  Stiffening of the arteries influences how hard the heart has to work to pump blood through the body.  Stiff artery walls means your blood is pumped under higher pressure and the heart has to work harder and often faster.  Healthy postmenopausal women received either placebo or MK7 for three years.  After three years of MK7 supplementation, carotid femoral pulse wave velocity (cfPWF) and arterial stiffness significantly decreased in the total group and other vessel measures improved significantly.  Long-term use of MK7 supplements improves arterial stiffness in healthy women.    

Tantisattamo E, Han KH, O'Neill C. Increased vascular calcification in patients receiving warfarin.  Arteriosclerosis, Thrombosis and Vascular Biology.  2015;35:237-42.
Mammograms from women with current, past or future warfarin use were examined for arterial calcification and compared with mammograms obtained in untreated women matched for age and diabetes mellitus.  In 451 women with mammograms performed after more than one month of warfarin therapy, the prevalence of arterial calcification was 50% greater than in 451 untreated women.  The findings indicate that the prevalence of breast arterial calcification is increased in women with current or past warfarin use.  This effect appears to be cumulative and may be irreversible.

Cundiff DK, Aqutter PS.  Cardiovascular disease death before age 65 in 168 countries correlated statistically with biometrics, socioeconomic status, tobacco, gender, exercise, macronutrients, and vitamin K.  Cureus.  2016 Aug 24;8(8):e748.

Ikari Y, Torii S, Shioi A, Okano T.  Impact of menaquinone-4 supplementation on coronary artery calcification and arterial stiffness:  an open label single arm study.

Piven E, Ponte B, Pruijm M, et al.  Inactive matrix Gla-protein is associated with arterial stiffness in an adult population-based study.  Hypertension.  2017;70(5):85-92.
Increased pulse wave velocity (PWV) is a marker of aortic stiffness and is also an independent predictor of mortality.  Matrix Glla-protein is a vascular calcification inhibitor that needs vitamin K to be activated.  This study looked at the relationship between high levels of dp-ucMGP and increased PWV.  1001 participants from Switzerland were tracked.  They found that high levels of dp-ucMGP are independently and positively associated with arterial stiffness, and if you have a deficiency of vitamin K in your system, your risk of having arterial stiffness is high.

Shea MK, Booth SL, Weiner DE, Brinkley TE, Kanaya AM, Murphy RA, et al.  Circulating vitamin K is inversely associated with incident cardiovascular disease risk among those treated for hypertension in the Health, Aging, and Body composition Study.  J Nutr.  2017 May;147(5):888-895.
There is a role for vitamin K in coronary artery calcification, a manifestation of cardiovascular disease, because vitamin K-dependent proteins are present in vascular tissue.  This study looked at phylloquinone (vitamin K1) and found that K1 status was not significantly associated with CVD risk overall, but that low levels of K1 was associated with a higher CVD risk in older adults treated for hypertension. (Typically MK7 is the vitamin associated with alleviating heart disease - not K1).

Vissers LE, Dalmeijer GW, Boer JM, Verschuren WM, Van der Schouw YT, Beulens JW.  The relationship between vitamin K and peripheral arterial disease.  Atherosclerosis.  2017 Sep;252:15-20.
The relationship between phylloquinone and menaquinone intake and the risk of peripheral artery disease (PAD) was explored.  They followed 36,629 participants for twelve years, with 489 cases of PAD being documented.  The results showed that a high intake of menaquinones was associated with a reduced risk of PAD.  A high intake of phylloquinone was not associated with a reduced risk of PAD.