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. 2012;7(10):e47991.
doi: 10.1371/journal.pone.0047991. Epub 2012 Oct 31.

Vitamin K Intake and Plasma Desphospho-Uncarboxylated Matrix Gla-protein Levels in Kidney Transplant Recipients

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Free PMC article

Vitamin K Intake and Plasma Desphospho-Uncarboxylated Matrix Gla-protein Levels in Kidney Transplant Recipients

Paul Y Boxma et al. PLoS One. .
Free PMC article

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.

Conflict of interest statement

Competing Interests: Cees Vermeer is CEO of Vitak B.V. The other authors have declared that no competing interests exist. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

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Grant support

Dr. de Borst is supported by personal development grants from the Dutch Kidney foundation (KJPB.08.07, www.nierstichting.nl) and the University Medical Center Groningen (Mandema stipend), and by the European Union (FP7, Systems Biology towards Novel Chronic Kidney Disease Diagnosis and Treatment Project consortium (SysKid, www.syskid.eu), project number 241544)). This work is supported by a consortium grant from the Dutch Kidney Foundation (NIGRAM consortium, grant no CP10.11). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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