Receptor activator of nuclear factor κB ligand/osteoprotegerin axis and vascular calcifications in patients with chronic kidney disease

Elevated Circulating Osteoprotegerin Levels in the Plasma of Hemodialyzed Patients With Severe Artery Calcification

We studied the correlations between circulating osteoprotegerin (OPG) level and radial artery calcification (RAC) assessed histologically and carotid artery intima-media thickness (CCA-IMT). Moreover, we studied the relationship between OPG levels and all-cause and cardiovascular (CV) mortality during a 5-year observation period. The study comprised 59 CKD patients (36 hemodialyzed (HD), 23 predialysis). The biochemical parameters included: creatinine, calcium, phosphate, intact parathormone, C-reactive protein, interleukin-6, tumor necrosis factor receptor II (TNFRII), transforming growth factor-β, hepatocyte growth factor, fibroblast growth factor 23, osteonectin (ON), osteopontin, osteoprotegerin, and osteocalcin. CCA-IMT and the presence of atherosclerotic plaques was assessed by ultrasound. Fragments of radial artery obtained during creation of HD access were prepared for microscopy and stained for calcifications with alizarin red. RAC was detected in 34 patients (58%). In multiple regression adjusted for dialysis status, TNFRII, ON and Framingham risk score (FRS) were identified as the independent predictors of OPG. Serum OPG above the median value of 7.55 pmol/L significantly predicted the presence of RAC in simple logistic regression (OR 5.33; 95%CI 1.39-20.4; P = 0.012) and in multiple logistic regression adjusted for FRS, dialysis status and CCA-IMT values (OR 6.56; 95%CI 1.06-40.6; P = 0.036). OPG levels above the median were associated with higher CCA-IMT values (1.02 ± 0.10 vs. 0.86 ± 0.13; P < 0.001) and predicted the presence of atherosclerotic plaques in carotid artery (OR 14.4; 95%CI 2.84-72.9; P < 0.001), independently of FRS, dialysis status and RAC. In this study, elevated serum OPG levels correlated with higher CCA-IMT, the presence of atherosclerotic plaques and the severity of the RAC independently of each other. During follow-up, 25 patients (42%) died, including 21 due to CV causes. In multiple Cox regression, OPG above the median predicted overall survival independently of dialysis status, Framingham risk score, CCA-IMT above the median value, and the presence of atherosclerotic plaques in CCA, but not independently of RAC. We postulate that circulating OPG may play a dual role as a marker for both medial arterial calcification and atherosclerosis, hence it seems to be a valuable tool for assessing CV risk in patients with CKD. OPG might be an early indicator of all-cause mortality in CKD patients with advanced medial arterial calcification.

Serum Osteoprotegerin Is a Potential Biomarker of Insulin Resistance in Chinese Postmenopausal Women with Prediabetes and Type 2 Diabetes

The aim of this study is to investigate the circulating OPG levels in postmenopausal women with diabetes and prediabetes and explore the relationships between serum OPG and insulin resistance. A total of 271 unrelated Chinese postmenopausal women were recruited in this study. The subjects were divided into type 2 diabetes mellitus (T2DM) group (n = 93), impaired glucose regulation (IGR) (n = 90), and normal glucose regulation group (NGR) (n = 88), according to different glucose regulation categories. Serum OPG levels were measured by enzyme-linked immunosorbent assay. The serum OPG concentration in NGR group, 151.00 ± 45.72 pg/mL, was significantly lower than that in IGR group (169.28 ± 64.91 pg/mL) (p = 0.031) and T2DM group (183.20 ± 56.53 pg/mL) (p < 0.01), respectively. In multiple linear regression analysis, HOMA-IR, age, 2hPG, AST, ALP, and eGFR were found to be independent predictors of OPG. Increased serum OPG levels (OR = 1.009, p = 0.006) may be a risk factor for insulin resistance. The present study suggests that OPG might be implicated in the pathogenesis of diabetes and is a potential biomarker of insulin resistance in subjects with diabetes and prediabetes.