title: Vitamin k intake and plasma desphospho-uncarboxylated matrix Gla-protein levels in kidney transplant recipients.
abstract: Vitamin K is essential for activation of γ-carboxyglutamate (Gla)-proteins including the vascular calcification inhibitor matrix Gla-protein (MGP). Insufficient vitamin K intake leads to production of uncarboxylated, mostly inactive proteins and contributes to an increased cardiovascular risk. In kidney transplant recipients, cardiovascular risk is high but vitamin K intake and status have not been defined. We investigated dietary vitamin K intake, vascular vitamin K status and its determinants in kidney transplant recipients. We estimated vitamin K intake in a cohort of kidney transplant recipients (n = 60) with stable renal function (creatinine clearance 61 [42-77] (median [interquartile range]) ml/min), who were 75 [35-188] months after transplantation, using three-day food records and food frequency questionnaires. Vascular vitamin K status was assessed by measuring plasma desphospho-uncarboxylated MGP (dp-ucMGP). Total vitamin K intake was below the recommended level in 50% of patients. Lower vitamin K intake was associated with less consumption of green vegetables (33 vs 40 g/d, p = 0.06) and increased dp-ucMGP levels (621 vs 852 pmol/L, p<0.05). Accordingly, dp-ucMGP levels were elevated (>500 pmol/L) in 80% of patients. Multivariate regression identified creatinine clearance, coumarin use, body mass index, high sensitivity-CRP and sodium excretion as independent determinants of dp-ucMGP levels. In a considerable part of the kidney transplant population, vitamin K intake is too low for maximal carboxylation of vascular MGP. The high dp-ucMGP levels may result in an increased risk for arterial calcification. Whether increasing vitamin K intake may have health benefits for kidney transplant recipients should be addressed by future studies.
authors.affiliation: Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands.
authors.forename: Paul Y
authors.initials: PY
authors.lastname: Boxma
authors.forename: Else
authors.initials: E
authors.lastname: van den Berg
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Geleijnse
authors.forename: Gozewijn D
authors.initials: GD
authors.lastname: Laverman
authors.forename: Leon J
authors.initials: LJ
authors.lastname: Schurgers
authors.forename: Cees
authors.initials: C
authors.lastname: Vermeer
authors.forename: Ido P
authors.initials: IP
authors.lastname: Kema
authors.forename: Frits A
authors.initials: FA
authors.lastname: Muskiet
authors.forename: Gerjan
authors.initials: G
authors.lastname: Navis
authors.forename: Stephan J L
authors.initials: SJ
authors.lastname: Bakker
authors.forename: Martin H
authors.initials: MH
authors.lastname: de Borst
mesh_terms: D000368:Aged; D002135:Calcium-Binding Proteins / Q000097:blood*; D004032:Diet; D004034:Diet Surveys; D016326:Extracellular Matrix Proteins / Q000097:blood*; D005260:Female; D006801:Humans; D007668:Kidney / Q000503:physiopathology; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000601:surgery; D016030:Kidney Transplantation; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D014812:Vitamin K / Q000008:administration & dosage*; D014813:Vitamin K Deficiency / Q000097:blood; D014815:Vitamins / Q000008:administration & dosage*; D000097568:Matrix Gla Protein
chemical_list: D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D014812:Vitamin K; D014815:Vitamins; D000097568:Matrix Gla Protein