Abstract / Summary
Background: Osteocalcin (OC) is a protein synthesized by osteoblasts and is involved in bone formation. OC also participates in the regulation of metabolic processes. Serum OC concentrations rise with kidney function decrease. The aim of this study was to evaluate the associations between serum OC concentrations and laboratory parameters reflecting metabolic, nutritional and hormonal status, as well as anthropometric and body composition measurements in patients with eGFR (estimated Glomerular Filtration Rate) < 60 mL/min/1.73 m2. Methods: The study sample consisted of 144 men: 98 patients with eGFR < 60 mL/min/1.73 m2 (the study group) and 46 individuals with eGFR ≥ 60 mL/min/1.73 m2 (the control group). Body composition parameters were estimated with the use of bioimpedance spectroscopy (BIS). Laboratory measurements, including serum OC were performed. Results: In univariable regression analysis we observed a negative association between OC and parameters related to adipose tissue and a positive relationship with variables reflecting fluid overload in the study group. Serum laboratory measurements showed that plasma OC was positively associated with serum creatinine and parathyroid hormone (PTH) and negatively with plasma hemoglobin, insulin, vitamin D and HOMA-IR (Homeostatic Model Assessment of Insulin Resistance). Multivariable backward regression analysis showed a negative association between OC and fat tissue index (FTI) and a positive relationship between OC and relative overhydration (Rel OH) and PTH in men with eGFR < 60 mL/min/1.73 m2. Conclusions: Our results suggest that in men with CKD (Chronic Kidney Disease) and eGFR < 60 mL/min/1.73 m2 not receiving dialysis, serum OC may be associated with metabolic, nutritional, and hormonal disturbances. The observed association between OC and parameters indicative of fluid overload also suggests a potential role of serum OC as a marker of overhydration in this population.