Dialysis patients given menaquinone-7 showed large reductions in calcium deposits in the blood vessels, a major mortality risk factor in advanced kidney disease.
The study also confirmed previously observed associations between vascular calcification and dephosphorylated uncarboxylated matrix Gla protein (dp-ucMGP), which is a measure of vitamin K2 status.
Norwegian manufacturer Nattopharma supplied MenaQ7 (vitamin K2 as Mk-7) to the fifty patients in the trial.
“Daily administration of 360 μg of vitamin K2 (MK-7) decreased dp-ucMGP by 86 percent after 4 weeks and it was well tolerated,” observed researchers from Saint Joseph University Beirut and Saint George Hospital Ajaltoun, Lebanon.
Although, similar research had been conducted in Western European adults, “This is the first study to show that haemodialysis patients in the Eastern Mediterranean region have very high levels of dp-ucMGP. It denotes profound vitamin K deficiency,” the researchers noted.
K2 deficiency
VC is prevalent in patients with chronic kidney disease (CKD) undergoing haemodialysis and is closely linked to higher mortality rates.
Dialysis patients have been identified as vitamin K2 deficient in earlier research, with observed intake levels up to 40% lower than those in healthy individuals. Deficiency may be further increased by the use of vitamin K antagonists to prevent stroke and atrial fibrillation.
Vitamin K2 deficiency is characterised by high plasma levels of the biomarker dp-ucMGP. The biomarker is a K2 dependent protein and inactive form of MGP, which is recognised as a powerful inhibitor of tissue calcification.
Calcification correlation
The study reconfirmed that dp-ucMGP is also associated with VC, measured by aortic calcification score (AC-24).
“Our study revealed that dp-ucMGP increases linearly with the increase of the calcification score assessed by a lateral abdominal X-ray (AC-24),” the researchers concluded.
They explained that the protein could thus be used as a non-invasive marker of VC and as a measure of how menaquinone-7 treatment reduces this calcification.
Although findings of this study were generally consistent with previous work, there were differences in the magnitude of VC reduction. Diabetic patients exhibited smaller reductions, while the effect of menaquinone-7 may vary among ethnicities and individuals.
The team also emphasised that longer-term efficacy of menaquinone-7 also needs to be established.
“Further studies should be conducted to assess the change in vascular calcifications after an extended duration of therapy.”
The study also cast further doubt over the use of vitamin K antagonists (VKAs) in dialysis patients.
“VKAs are increasingly incriminated in VC and even calciphylaxis. Thus, many experts agreed lately on avoiding VKA treatment in dialysis patients. In our study, after 2 weeks of VKA withdrawal, patients reached a stable level of dp-ucMGP,” the researchers commented.
Source: BMC Nephrology
Published online ahead of print, doi: 10.1186/s12882-017-0609-3
“High Dephosphorylated-Uncarboxylated MGP in Hemodialysis patients: risk factors and response to vitamin K2, a pre-post intervention clinical trial.”
Authors: Mabel Aoun, et al