Plasma vitamin K levels are associated with coronary calcification in older adults.

Abstract

Vitamin K is involved in regulation of vascular calcification, as mediated by γ-carboxylation of matrix Gla protein (MGP), which inhibits calcification in vivo. Associations between MGP and calcification are equivocal in humans; less is known about interrelationships among vitamin K, MGP, and calcification. Vitamin K status, assessed by plasma levels and self-reported vitamin K1 intake, and serum MGP were measured in 452 older men and women free of symptomatic coronary artery disease (60–80y, mean 68y). Coronary artery calcification score (CAC) was determined by computed tomography. Analysis of variance was used to determine age- and gender-adjusted associations among vitamin K status, serum MGP, and CAC. Plasma K1, further adjusted for serum triglycerides, was inversely associated with CAC (p-trend= 0.009). Those in lowest quartile (Q1) of plasma K1 had 2.1 times more CAC than those in Q4 [plasma K1 (nmol/l): Q1= 0.08, Q4 = 2.92; adjusted mean CAC score: Q1= 57.4, Q4 = 122.3]. Dietary K1 was not associated with CAC. Serum MGP was not associated with either measure of vitamin K status or with CAC. Higher plasma K1 in older men and women were associated with lower CAC. Vitamin K status was not associated with serum MGP nor was serum MGP associated with CAC. Until assays are developed to differentiate the carboxylated from undercarboxylated MGP, the mechanism by which K1 has a protective role in CAC is uncertain.