Vitamin K: The New Faces of an Old Friend - a Role in Bone and Vascular Health

There is an exciting research expansion on the novel roles of vitamin K in the last decades. Subclinical deficiency in vitamin K is believed to be widely spread, possibly contributing to age-related diseases. The present review is focused on the effects of vitamin K on the skeleton and blood vessels, where it could be potentially useful in the prevention and treatment of osteoporosis and vascular calcification, both having a significant health impact in the society. The types (K1 and K2), nature and sources of vitamin K are reviewed as well as the mechanisms of action underlying their effects. Gamma-glutamic carboxylation of several vitamin K dependent proteins (VKDP), including clotting factors, is the primary mode of action of vitamin K, lead-ing to activation of proteins with specific functions. Priority was given to those VKDP that are involved in maintaining bone and vascular health. Other recently identified cellular transduction pathways through which vitamin K acts are also outlined. Experimental in vivo data confirming the expected beneficial effects of vitamin K on bones and blood vessels have paved the way for clinical studies. So far, the evidence from clinical experience with vitamin K supplementation is promising, but still insufficient to recommend routine use of vitamin K as a preventive agent. Several prospective randomized controlled clinical studies currently in progress are expected to give more clear-cut results allowing the routine use of vitamin K as a reliable, cheap and safe medication in the prevention of bone loss and vascular calcification. Biomed Rev 2017; 28: 70-90 Keywords: vitamin K, osteocalcin, matrix Gla-protein, osteoporosis, vascular calcification