Bone Abstracts

Poor vitamin K intake is associated with markedly increased cardiovascular risk and mortality. The molecular mechanism underlying this association is suggested to be the vitamin K-dependent carboxylation of vascular matrix Gla-protein (MGP), a potent calcification inhibitor. The carboxylation step is essential for its activation, and uncarboxylated MGP, produced during poor vitamin K status, is inactive.

The IDS-iSYS inaKtiv MGP assay is the automated version of a microtiter-plate sandwich ELISA for desphospho-uncarboxylated MGP (dp-ucMGP) developed and reported by VitaK. The inaKtiv MGP assay was demonstrated to respond to variations of vitamin K status, and the normal range in the healthy population is 200-800 pmol/l. During recent years we have analyzed dp-ucMGP levels in a number of cohorts at high-risk for cardiovascular mortality. It was found invariably that subjects with dp-ucMGP levels above the upper-normal range were at two to fivefold increased risk of all-cause mortality. This was especially so in patients with end-stage kidney disease and peripheral artery disease. Human intervention studies have demonstrated that high vitamin K intake both decreases dp-ucMGP to normal or sub-normal levels and also decreases arterial stiffening. We found a high correlation between the microtiter-plate assay and the IDS-iSYS inaKtiv MGP assay (R²=0.95) and the variation coefficient of the automated assay was <5%.

Therefore, we propose the inaKtiv MGP assay as the method of choice for quantifying circulating dp-ucMGP, an independent biomarker for vascular vitamin K status and cardiovascular risk. Poor vitamin K status is a modifiable risk factor for arterial calcification, and the IDS-iSYS inaKtiv MGP assay is the most direct way to quickly identify subjects at risk and to monitor the effect of vitamin K intervention.