Osteoprotegerin as a marker of cardiovascular risk in patients on peritoneal dialysis

INTRODUCTION Arterial thickening contributes to elevated cardiovascular risk in patients on maintenance renal replacement therapy. The common carotid artery intima-media thickness (CCA-IMT) is an early atherosclerotic marker and may be used to assess the stratification of atherosclerotic advancement and resultant arterial calcification.
OBJECTIVES The aim of the study was to evaluate the associations between atherosclerotic changes in the common carotid arteries expressed as the CCA-IMT and the body mass index (BMI), serum lipid levels, C‑reactive protein (CRP), and selected bone metabolism parameters including phosphorus, calcium, intact parathormone (iPTH), alkaline phosphatase, osteopontin, osteoprotegerin, osteocalcin, fetuin A, and fibroblast growth factor‑23 (FGF‑23) in patients treated with peritoneal dialysis.
PATIENTS AND METHODS The study included 67 patients with chronic kidney disease (36 men and 31 women) aged 53 ±13 years (range, 19–75 years) treated with peritoneal dialysis for 30 ±24 months. The CCA‑IMT was assessed by ultrasonography using Acuson 128/10 XP. The BMI was calculated using the Quetelet formula. Serum lipid levels, phosphorus, calcium, iPTH, alkaline phosphatase, and CRP were measured using standard laboratory methods, while fetuin A, osteocalcin, osteoprotegerin, osteopontin, and FGF‑23 using commercial enzyme‑linked immunosorbent assay kits.
RESULTS Positive correlations were observed between CCA-IMT and age (r = 0.54, P <0.0001), BMI (r = 0.39, P = 0.003), and osteoprotegerin (r = 0.38, P = 0.004). In a multiple regression analysis, age (r = 0.41, P = 0.01), osteocalcin (r = 0.34, P = 0.04), and log‑transformed osteoprotegerin values (r = 0.38, P = 0.02) remained independently associated with the CCA-IMT. The highest CCA‑IMT values (0.85 ±0.21) were observed in patients with osteoprotegerin concentrations in the upper tertile. Osteoprotegerin concentrations strongly and positively correlated with the duration of dialysis treatment (r = 0.55, P <0.0001). 
CONCLUSIONS The CCA‑IMT has been shown to be a reliable noninvasive measure of subclinical atherosclerosis and, therefore, of associated increased vascular risk. Elevated serum osteoprotegerin levels may be useful as a prognostic marker of cardiovascular risk in dialyzed patients.