miRNAs are molecules that play a role in the post-transcriptional regulation of gene expression. They involved in almost all biological processes. However the role in the development of mineral-bone disorders in the population of dialysis patients is still poorly understood. There is no data on the comparison of miRNA and FGF-23 expression patterns, as well as the level of ionized calcium and inorganic phosphorus, as well as the effect of phosphate binders.
Objective: to evaluate associations between the levels of miRNA-21, miRNA-126 and miRNA-210 in serum with indicators of bone and mineral metabolism in hemo- and peritoneal dialysis patients.
Material and methods: The study included 55 patients, of which 33 received maintenance hemodialysis treatment (HD), and 22 – peritoneal dialysis (PD). The control group consisted of 28 healthy volunteers. In all patients, except for routine examination methods: determining the level of calcium, inorganic phosphorus, parathyroid hormone (PTH) level, the level of expression of microRNA-21, microRNA-126 and microRNA-210 was determined by real-time polymerase chain reaction. The serum level of FGF-23 was determined by ELISA (enzyme-linked immunosorbent assay).
Results. The concentration of serum levels of FGF-23 in HD patients exceeded that of those on PD. The increase in the concentration of FGF-23 in the blood serum in patients on maintenance HD correlated with the vintage of dialysis treatment (rs=0,587; p=0,002). The positive correlation was found between the serum concentrations of FGF-23 and inorganic phosphorus (rs =0,4; p=0,01). The positive correlation was found between the serum concentrations of microRNA-126 and phosphorus (rs=0,324; p=0,003). The direct relationship was found between the serum concentrations of microRNA-126 and the level of FGF-23 (rs=0,322; p=0,024). The serum level of FGF-23 positively correlated with the serum PTH level (rs= 0,5; p=0,01). The direct relationship was found between the serum concentrations of microRNA-126 and microRNA-210 and the serum FGF-23 concentration (rs=0,23; p=0,04, and rs=0,62; p=0,024, respectively). In the group of patients receiving sevelamer carbonate, lower levels of FGF-23 (12.4±5.9) were noted, in contrast to the group that did not receive this drug (23±7.3; p=0.003) and PTH (110±27 ng/mL, in the non-treated group 340±15; p=0.01). Patients receiving sevelamer carbonate have lower levels of miRNA-126 (p=0,002).
Conclusions. MicroRNA expression indices also reflect the state of mineral metabolism in dialysis patients. The positive correlation has been established between the level of miRNA-126 and miRNA-210 expression and the level of inorganic phosphorus in dialysis patients. The level of FGF-23 directly correlated with the serum level of parathyroid hormone, as well as "dialysis vintage". The use of phosphate binders, in particular sevelamer carbonate, can positively affect the expression of miRNAs involved in the pathogenesis of cardiovascular events.

Keywords: parathormone, miRNAs, dialysis, bone mineral metabolism, FGF-23, chronic kidney disease