Circulating Wnt/β-catenin signalling inhibitors and uraemic vascular calcifications

Background. The process of vascular calcification has been associated with the canonical Wnt/beta-catenin signalling pathway in cell cultures and animal studies. The relationship between circulating Wnt/beta-catenin inhibitors and vascular calcification in dialysis patients is unknown. The aim of this study was to investigate the associations between serumdickkopf-1 (Dkk-1) and sclerostin, two circulating inhibitors of the Wnt/beta-catenin signalling pathway, and the severity of aortic calcification (AoC) and cardiovascular outcomes in dialysis patients. Methods. Thiswas a prospective observational cohort study. One hundred and twenty-five patients onmaintenance haemodialysis participated in the study. Serum levels of Dkk-1 and sclerostin were measured. AoC scores were calculated from plain films of both posterior-anterior and lateral views. The patients were followed up for 2 years or until death or withdrawal. Results. The circulating sclerostin level was inversely associated with the severity of AoC (P = 0.035) and indicators of the bone turnover rate including serum alkaline phosphatase (ALP) (r = -0.235, P = 0.008) and intact parathyroid hormone (r = -0.523, P < 0.001). Furthermore, Cox regression analysis indicated that the patients with high circulating sclerostin levels were less likely to experience future cardiovascular events [1 pmol/L sclerostin increase, hazard ratio 0.982 (95% CI, 0.967-0.996), P = 0.015] after adjusting for a propensity score. In contrast, serum Dkk-1 was not associated with AoC and clinical outcomes. Conclusions. In long-term haemodialysis patients, circulating sclerostin but not Dkk-1 is inversely associated with AoCs and future cardiovascular events. Our findings suggest that sclerostin, as a bone-related protein, might act as a communicator between uraemic bone and vasculature.