title: Dephosphorylated-uncarboxylated Matrix Gla protein concentration is predictive of vitamin K status and is correlated with vascular calcification in a cohort of hemodialysis patients.
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.
  
  
  CONCLUSIONS
  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.
  
  
  BACKGROUND
  B707201215885.
authors.affiliation: Nephrology-Dialysis-Transplantation, University of Liège, CHU Sart Tilman, Liège, Belgium. pierre_delanaye@yahoo.fr.
authors.forename: Pierre
authors.initials: P
authors.lastname: Delanaye
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Krzesinski
authors.forename: Xavier
authors.initials: X
authors.lastname: Warling
authors.forename: Martial
authors.initials: M
authors.lastname: Moonen
authors.forename: Nicole
authors.initials: N
authors.lastname: Smelten
authors.forename: Laurent
authors.initials: L
authors.lastname: Médart
authors.forename: Hans
authors.initials: H
authors.lastname: Pottel
authors.forename: Etienne
authors.initials: E
authors.lastname: Cavalier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002135:Calcium-Binding Proteins / Q000097:blood*; D015331:Cohort Studies; D016326:Extracellular Matrix Proteins / Q000097:blood*; D005260:Female; D000089703:Fibroblast Growth Factor-23; D006801:Humans; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation / Q000502:physiology; D011237:Predictive Value of Tests; D006435:Renal Dialysis / Q000009:adverse effects; D061205:Vascular Calcification / Q000097:blood* / Q000175:diagnosis*; D014812:Vitamin K / Q000037:antagonists & inhibitors / Q000097:blood*; D000097568:Matrix Gla Protein
chemical_list: D015415:Biomarkers; D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D000089703:Fibroblast Growth Factor-23; D014812:Vitamin K; D000097568:Matrix Gla Protein; C000717427:FGF23 protein, human