• Ralf Westenfeld, Thilo Krueger, Georg Schlieper, Ellen C M Cranenburg, Elke J Magdeleyns, Stephan Heidenreich, Stefan Holzmann, Cees Vermeer, Willi Jahnen-Dechent, Markus Ketteler, Jürgen Floege, and Leon J Schurgers.
• Division of Cardiology, Pulmonary Diseases, Vascular Medicine, University Hospital Düsseldorf, Germany.
• Am. J. Kidney Dis. 2012 Feb 1; 59 (2): 186-95.

BackgroundVascular calcification is a predictor of cardiovascular morbidity and mortality. Hemodialysis patients experience severe vascular calcifications. Matrix Gla protein (MGP) is a central calcification inhibitor of the arterial wall; its activity depends on vitamin K-dependent γ-glutamate carboxylation. Uncarboxylated MGP, formed as a result of vitamin K deficiency, is associated with cardiovascular disease. Recent studies suggest poor vitamin K status in hemodialysis patients. We therefore aimed to investigate whether daily vitamin K supplementation improves the bioactivity of vitamin K-dependent proteins in hemodialysis patients, assessed by circulating dephosphorylated-uncarboxylated MGP, uncarboxylated osteocalcin, and uncarboxylated prothrombin (PIVKA-II [protein induced by vitamin K absence II]).Study DesignInterventional randomized non-placebo-controlled trial with 3 parallel groups.Setting & Participants53 long-term hemodialysis patients in stable conditions, 18 years or older. 50 healthy age-matched individuals served as controls.InterventionsMenaquinone-7 (vitamin K(2)) treatment at 45, 135, or 360 μg/d for 6 weeks.OutcomesPlasma levels of dephosphorylated-uncarboxylated MGP, uncarboxylated osteocalcin, and PIVKA-II.MeasurementsPlasma levels were assessed using enzyme-linked immunosorbent assays.ResultsAt baseline, hemodialysis patients had 4.5-fold higher dephosphorylated-uncarboxylated MGP and 8.4-fold higher uncarboxylated osteocalcin levels compared with controls. PIVKA-II levels were elevated in 49 hemodialysis patients. Vitamin K(2) supplementation induced a dose- and time-dependent decrease in circulating dephosphorylated-uncarboxylated MGP, uncarboxylated osteocalcin, and PIVKA-II levels. Response rates in the reduction in dephosphorylated-uncarboxylated MGP levels were 77% and 93% in the groups receiving 135 μg and 360 μg of menaquinone-7, respectively.LimitationsSmall sample size.ConclusionsThis study confirms that most hemodialysis patients have a functional vitamin K deficiency. More importantly, it is the first study showing that inactive MGP levels can be decreased markedly by daily vitamin K(2) supplementation. Our study provides the rationale for intervention trials aimed at decreasing vascular calcification in hemodialysis patients by vitamin K supplementation.Copyright © 2012 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

44 keywords...

hide…