Open Access Research article

Dephosphorylated-uncarboxylated Matrix Gla protein concentration is predictive of vitamin K status and is correlated with vascular calcification in a cohort of hemodialysis patients

Pierre Delanaye1*, Jean-Marie Krzesinski1, Xavier Warling2, Martial Moonen2, Nicole Smelten3, Laurent Médart4, Hans Pottel5 and Etienne Cavalier6

Author Affiliations

1 Nephrology-Dialysis-Transplantation, University of Liège, CHU Sart Tilman, Liège, Belgium

2 Nephrology-Dialysis, Centre Hospitalier Régional "La Citadelle", Liège, Belgium

3 Nephrology-Dialysis, Centre Hospitalier "Bois de l’Abbaye", Seraing, Belgium

4 Radiology, Centre Hospitalier "La Citadelle", Liège, Belgium

5 Interdisciplinary Research Center, University of Leuven, Kulak, Kortrijk, Belgium

6 Clinical Chemistry, University of Liège, CHU Sart Tilman, Liège, Belgium

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BMC Nephrology 2014, 15:145  doi:10.1186/1471-2369-15-145

Published: 4 September 2014

Abstract

Background

Matrix Gla protein (MGP) is known to act as a potent local inhibitor of vascular calcifications. However, in order to be active, MGP must be phosphorylated and carboxylated, with this last process being dependent on vitamin K. The present study focused on the inactive form of MGP (dephosphorylated and uncarboxylated: dp-ucMGP) in a population of hemodialyzed (HD) patients. Results found in subjects being treated or not with vitamin K antagonist (VKA) were compared and the relationship between dp-ucMGP levels and the vascular calcification score were assessed.

Methods

One hundred sixty prevalent HD patients were enrolled into this observational cohort study, including 23 who were receiving VKA treatment. The calcification score was determined (using the Kauppila method) and dp-ucMGP levels were measured using the automated iSYS method.

Results

dp-ucMGP levels were much higher in patients being treated with VKA and little overlap was found with those not being treated (5604 [3758; 7836] vs. 1939 [1419; 2841] pmol/L, p <0.0001). In multivariate analysis, treatment with VKA was the most important variable explaining variation in dp-ucMGP levels even when adjusting for all other significant variables. In the 137 untreated patients, dp-ucMGP levels were significantly (p < 0.05) associated both in the uni- and multivariate analysis with age, body mass index, plasma levels of albumin, C-reactive protein, and FGF-23, and the vascular calcification score.

Conclusion

We confirmed that the concentration of dp-ucMGP was higher in HD patients being treated with VKA. We observed a significant correlation between dp-ucMGP concentration and the calcification score. Our data support the theoretical role of MGP in the development of vascular calcifications. We confirmed the potential role of the inactive form of MGP in assessing the vitamin K status of the HD patients.

Trial registration

B707201215885

Keywords:
Matrix Gla protein; Vascular calcification; Vitamin K