Abstract
Background: A low vitamin K status is common in patients on haemodialysis, and this is considered one of the reasons for the accelerated atherosclerosis in these patients. The vitamin is essential in activation of the protein Matrix Gla Protein (MGP), and the inactive form, dp-ucMGP, is used to measure vitamin K status. The purpose of this study was to investigate possible underlying causes of low vitamin K status, which could potentially be low intake, washout during dialysis or inhibited absorption capacity. Moreover, the aim was to investigate whether the biomarker dp-ucMGP is affected in these patients. Method: Vitamin K intake was assessed by a Food Frequency Questionnaire (FFQ) and absorption capacity by means of D-xylose testing. dp-ucMGP was measured in plasma before and after dialysis, and phylloquinine (vitamin K1) and dp-ucMGP were measured in the dialysate. Changes in dp-ucMGP were measured after 14 days of protein supplementation. Results: All patients had plasma dp-ucMGP above 750 pmol/L, and a low intake of vitamin K. The absorption capacity was normal. The difference in dp-ucMGP before and after dialysis was −1022 pmol/L (p < 0.001). Vitamin K1 was not present in the dialysate but dp-ucMGP was at a high concentration. The change in dp-ucMGP before and after protein supplementation was −165 pmol/L (p = 0.06). Conclusion: All patients had vitamin K deficiency. The reason for the low vitamin K status is not due to removal of vitamin K during dialysis or decreased absorption but is plausibly due to a low intake of vitamin K in food. dp-ucMGP is washed out during dialysis, but not affected by protein intake to a clinically relevant degree.
Highlights
Vitamin K is a fat-soluble vitamin primarily present in green vegetables and dairy products.Vitamin K exists in three forms—phylloquinone (K1), menaquinones (K2) and menadione (K3) [1].Phylloquinone is mainly present in vegetables and herbs and is the main source of vitamin K in the diet
The intake of phylloquinone, menaquinone and total vitamin K was calculated based on the reported Food Frequency Questionnaire (FFQ)
Phylloquinone was the main source of vitamin K with a median intake of 54 μg/d
Summary
Vitamin K is a fat-soluble vitamin primarily present in green vegetables and dairy products.Vitamin K exists in three forms—phylloquinone (K1), menaquinones (K2) and menadione (K3) [1].Phylloquinone is mainly present in vegetables and herbs and is the main source of vitamin K in the diet. Vitamin K is a fat-soluble vitamin primarily present in green vegetables and dairy products. Vitamin K exists in three forms—phylloquinone (K1), menaquinones (K2) and menadione (K3) [1]. Phylloquinone is mainly present in vegetables and herbs and is the main source of vitamin K in the diet. Menaquinones are synthesized by bacteria and are present in fermented foods and are synthesized in the large intestine as well. The vitamin is essential in activation of the protein Matrix Gla Protein (MGP), and the inactive form, dp-ucMGP, is used to measure vitamin K status. The purpose of this study was to investigate possible underlying causes of low vitamin K status, which could potentially be low intake, washout during dialysis or inhibited absorption capacity. Method: Vitamin K intake was assessed by a Food Frequency. Changes in dp-ucMGP were measured after 14 days of protein supplementation
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