Correlations of Plasma Desphosphorylated Uncarboxylated Matrix Gla Protein with Vascular Calcification and Vascular Stiffness in Chronic Kidney Disease

Abstract

Background: Matrix Gla protein (MGP) is a potent inhibitor of vascular calcification and needs vitamin K-dependent carboxylation for its activity. High levels of desphosphorylated uncarboxylated MGP (dp-ucMGP) were significantly associated with vitamin K deficiency and vascular calcification. This study was conducted to explore the correlations of plasma dp-ucMGP with vascular calcification and vascular stiffness in chronic kidney disease (CKD) patients.

Methods: This cross-sectional study enrolled 83 CKD stages 3-5 patients. Vascular calcification score was determined by calcific lesions in the abdominal aorta (AAC) shown by lateral lumbar film; vascular stiffness was assessed by cardio-ankle vascular index (CAVI) and pulse wave velocity, while plasma dp-ucMGP levels were measured using ELISA method. Multivariate regression analyses were used to select factors that were independently associated with vascular calcification and vascular stiffness.

Results: The mean age was 62.9 ± 13.9 years. CKD stages 3, 4, and 5 constituted 51.8, 13.3, and 34.9%, respectively. The median of plasma dp-ucMGP levels in CKD stages 3, 4, and 5 were 586 (452-888), 870 (594-1,591), and 1,050 (518-1,298) pmol/L, respectively. The prevalence of vascular calcification (AAC score ≥1) was 63.4% and that of vascular stiffness (CAVI ≥9) was 46.3%. Vascular calcification was correlated with vascular stiffness (r2 = 0.50, p < 0.001). Multivariate logistic regression analysis models to predict vascular calcification showed that age and plasma dp-ucMGP levels were significantly correlated with vascular calcification (OR 1.21; 95% CI 1.09-1.33; p < 0.001 and OR 1.002; 95% CI 1.001-1.004; p = 0.004, respectively). In contrast, there was no association between plasma dp-ucMGP levels and vascular stiffness.

Conclusions: Plasma dp-ucMGP levels increase according to the severity of CKD. Plasma dp-ucMGP was positively associated with vascular calcification and might be utilized as an early marker for vascular calcification in CKD patients.