Roles of vitamin K (phylloquinone and menaquinones) and related proteins (prothrombin, des-γ-carboxyprothrombin, and γ-glutamic acid) in healthy adults

The aim of the study was to evaluate the plasma levels of vitamin K (VK), prothrombin, des-γ-carboxyprothrombin (DCP) by ELISA with two types of monoclonal antibodies (MU-3 and 19B7), and urinary γ-carboxyglutamic acid (γ-Gla) in healthy adults (45 males and 45 females) and 11 patients with liver cirrhosis. VK and γ-Gla were analyzed by reverse-phase HPLC, prothrombin was determined using a method with a synthetic chromogenic substrate, and DCPs were analyzed by immunoaffinity chromatography and reverse-phase HPLC, and measured by ELISA. We were able to detect phylloquinone K (PK) and menaquinones MK-4, -5, -6, -7, -8 and -9, and we isolated several DCPs from plasma. Age had significant positive correlations with levels of urinary γ-Gla, plasma MK-7 and total VK, and VKDPs (prothrombin and DCP using MU-3 antibody) in the healthy adults. Significant positive correlations were also found between urinary γ-Gla and plasma levels of PK, MK-4, MK-7, and total VK and VKDPs (prothrombin and DCP using MU-3 antibody) in the healthy adults. γ-Gla and total VK levels were significantly higher in healthy adults than in patients with liver cirrhosis, and VK components, prothrombin, DCPs, and the MU-3/19B7 ratio showed a tendency to be higher in the healthy adults. We conclude that the status of VK and related proteins may reflect the latent increase in des-γ-carboxylation in healthy aging.