Calcium scores and matrix Gla protein levels: association with vitamin K status

Background Vascular calcification in humans is associated with an increased cardiovascular risk. Carboxylated matrix Gla protein (cMGP) inhibits vascular calcification. Vitamin K is an essential cofactor for the activation of uncarboxylated matrix Gla protein (ucMGP). It has been suggested that patients on long-term treatment with vitamin K antagonists develop aortic valve calcifications because of lower levels of circulating MGP. We therefore hypothesized that arterial calcification and a low vitamin K status are associated with ucMGP. To that aim, we measured arterial calcium scores, the osteocalcin ratio (OCR), as a proxy for vitamin K status, and ucMGP. Materials and methods In 36 hypertensive patients, we determined the Agatston score with computer tomography scans of the abdominal aorta, carotid and coronary arteries. The total calcium score was calculated as the sum of the separate Z-scores. Results The total calcium Z-score was significantly correlated to age (r = 0 center dot 683, P <0 center dot 001), smoking (r = 0 center dot 372, P = 0 center dot 026), total cholesterol (r = 0 center dot 353, P = 0 center dot 034), LDL cholesterol (r = 0 center dot 490, P = 0 center dot 003), triglycerides (r = 0 center dot 506, P = 0 center dot 002), fasting glucose (r = 0 center dot 454, P = 0 center dot 005), systolic blood pressure (r = 0 center dot 363, P = 0 center dot 029) and pulse pressure (r = 0 center dot 685, P <0 center dot 001). In multivariate regression analyses, OCR and total calcium score were significantly associated with ucMGP. Conclusions We found a positive association of total arterial calcium score and a high OCR (reflecting low vitamin K status) with ucMGP serum levels. This warrants further studies to explore the pathophysiological background of this phenomenon.