Influence of Vitamin K2 Administration on Vessel Calcification Markers in Patients With Chronic Kidney Disease

Vessel calcification is a recognised cardiovascular morbidity risk factor in patients with chronic kidney disease (CKD). Recent reports indicate a significant role of Matrix Gla-protein (MGP) in decreasing calcification processes. MGP is excretion protein whose mechanism of action is not yet fully explained and which to be activated requires phosphorylation and carboxylation where cofactor is vitamin K. Immunohistochemical tests showed a high level of un-carboxylated MGP in calcified vessels. These observations indicate that shortage of vitamin K is a significant risk factor for the development of vessel calcification. On the other hand CKD patients often display shortages of this vitamin. Another calcification risk factor in CKD patients are calcium-phosphate disturbances and insufficiency of vitamin D3 which in physiological concentration stimulates MGP transcription. Cranenburg et al. showed a decrease vessel calcification in dialysis patients treated with vitamin K2. Vitamin K2 exists in two forms K1 and K2, however only the K2 form displays calcification decreasing properties. There are currently no similar studies in patients with chronic kidney disease who do not require renal replacement therapy.

The aim of study. The aim of this study is estimation of influence of vitamin K2 administration over the period of 9 months on vessel calcification in 3.- 5. stage CKD patients.

Materials and methods. It is a prospective, randomised double-blind study carried out in parallel groups. 60 patients with CKD (GFR 15-60 ml/min) whose renal replacement therapy is to commence not earlier than in 9 months are planned to be qualified for the study. After familiarizing the patients with the aims of the study and obtaining their written consent, non-invasive tests will be carried out in order to estimate the presence and degree of vessel calcification: common carotid artery intima media thickness (CCA-IMT) by ultrasound examination, coronary artery calcium score (CACS) by multiscan CT as well as the presence of calcified heart valves by ultrasound examination. Patients with calcium score >10 (Agatston scoring system) will be qualified for the study. On the basis of randomised selection, patients will be divided into two groups: 30 patients will be given 90 μg vitamin K2+10 μg cholecalciferol (Vitamin D)and 30 patients will be given only 10 μg cholecalciferol. After a 9-month treatment the image diagnostic will be carried out in order to estimate the degree of vessel calcification. Patients and their basic laboratory test will be evaluated during the study period by a nephrologists on a monthly basis. First, at the commencement of the study, then after 3, 6 and finally after 9 months during the last visit, 10 ml of serum and plasma will be taken and frozen in order to conduct special marking tests: phosphorylated MGP (pMGP), uncarboxylated MGP (ucMGP), 25-OH cholecalciferol, hsCRP.

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