Cardiovascular Calcification and Bone: A Comparison of the Effects of Dietary and Serum Vitamin K and its Dependent Proteins

Abstract

This review compares the effect of vitamin K on cardiovascular (CV) calcification and bone health and shows that, in principal, the γ-carboxylation of the vitamin K-dependent proteins matrix Gla protein (MGP) and its bone equivalent osteocalcin (OC), generally ensures that hydroxyapatite is kept out of the CV system and is deposited in bone. This is an important finding, since there is currently no reliable treatment for CV calcification.Vitamin K2 (menaquinone) may be more effective in the arteries, while vitamin K1 (phylloquinone) is more active in bone. Nevertheless, there remains considerable uncertainty over the precise scope of the functions of MGP and OC, and their carboxylated and under-carboxylated forms, as well as the newly discovered vitamin K-dependent proteins. Although a diet high in vegetables could deliver adequate phylloquinone, supplementation of menaquinone may be necessary for those at risk of CV calcification. Several animal studies and one human study have demonstrated that arterial calcification could be reduced with vitamin K supplementation and there are further trials in progress. Patients on warfarin are particularly prone to CV calcification but there has been concern that supplementation would either counter warfarin treatment or destabilise INR. In fact, studies suggest that low dose phylloquinone did not increase coagulation and may improve the stability of anticoagulant therapy. Furthermore, use of oral anticoagulants which do not affect vitamin K metabolism, such as ximelagatran, could be used when there is a need for vitamin K supplementation for artery or bone health.