Undercarboxylated osteocalcin as a biomarker of subclinical atherosclerosis in non-dialysis patients with chronic kidney disease

Background: Studies in recent years have shown that undercarboxylated osteocalcin (uOC) not only maintains bone mineralization, but is also involved in the regulation of atherosclerosis. However, a correlation between uOC and carotid atherosclerosis in non-dialysis patients with chronic kidney disease (CKD) has not been investigated. A total of 240 non-dialysis patients with CKD were included in the study. For these patients, the median estimated glomerular filtration rate (eGFR) was 20.05 (12.43-49.32) ml/min/1.73m(2). Serum uOC levels were measured using enzyme-linked immunosorbent assay (ELISA). Carotid ultrasonography was performed to assess carotid atherosclerotic plaques and intima-media thickness (IMT) in an attempt to analyze the relationship between uOC level and carotid atherosclerosis. Results: The uOC levels of non-dialysis patients with CKD were significantly lower than those of healthy controls [28.16 (21.40-45.85) ng/mL vs. 36.42 (28.05-49.28) ng/mL, P < 0.01]. The uOC levels gradually decreased as CKD progressed (P < 0.01). The uOC levels were significantly lower in patients with carotid plaques than in patients without carotid plaques [25.98 (20.14-31.35) ng/mL vs. 31.02 (25.86-36.40) ng/mL, P < 0.01]. uOC level showed significant negative correlation with IMT (r = -0.33, P < 0.01). Logistic regression analysis revealed that after adjustment for various confounding factors, decreased uOC levels were shown to indicate increased possibility of carotid atherosclerotic plaque development in non-dialysis patients with CKD (on every 1 SD decrease in the uOC level, odds ratio 1.70, 95 % confidence interval 1.24-2.98, P < 0.01). Multivariate stepwise regression analysis demonstrated that decreased uOC level (beta = -0.163, P < 0.05) was an independent risk factor for increased carotid IMT in non-dialysis patients with CKD. Conclusion: Serum uOC levels in non-dialysis patients with CKD are significantly lower than those in healthy individuals, and uOC is closely associated with subclinical atherosclerosis in CKD patients.