Vitamin K2 supplementation and arterial stiffness among renal transplant recipients—a single-arm, single-center clinical trial

Subclinical vitamin K deficiency is prevalent among renal transplant recipients and is associated with an increased risk of

cardiovascular disease. However, the association between vitamin K supplementation and improvement of arterial stiffness

has not been explored in the renal transplant population. The KING trial (vitamin K2 In reNal Graft) is a single-arm study

that evaluated the association between the change in vitamin K status and indices of arterial stiffness following 8 weeks of

menaquinone-7 (vitamin K2) supplementation (360 mg once daily) among renal transplant recipients (n . 60). Arterial stiffness

was measured using carotid-femoral pulse wave velocity (cfPWV). Subclinical vitamin K deficiency was defined as plasma

concentration of dephosphorylated-uncarboxylated matrix Gla protein (dp-ucMGP) >500 pmol/L.At baseline, 53.3% of the study

subjects had subclinical vitamin K deficiency. Supplementation was associated with a 14.2% reduction in mean cfPWVat 8 weeks

(cfPWV pre-vitamin K2 . 9.8 2.2 m/s vs. cfPWV post-vitamin K2 . 8.4 1.5 m/s; P < .001). Mean dp-ucMGP concentrations

were also significantly reduced by 55.1% following menaquinone-7 supplementation with a reduction in the prevalence

of subclinical deficiency by 40% (P . .001). When controlled for age, durations of hemodialysis and transplantation, and the

change in 24-hour mean arterial pressure, the improvement in arterial stiffness was independently associated with the reduction

in dp-ucMGP concentration (P . .014).Among renal transplant recipients with stable graft function, vitamin K2 supplementation

was associated with improvement in subclinical vitamin K deficiency and arterial stiffness. (Clinicaltrials.gov: NCT02517580). J