Preanalytical features of the determination of circulating microRNAs as new specific biomarkers of the body’s response to physical activity

MicroRNAs are small non-coding single-stranded RNAs, 18 to 25 nucleotides long, they regulate gene expression at the post-transcriptional level through specific binding to the target mRNA, leading to its degradation. In recent decades, the development of technologies for determining the expression profiles of miRNAs has become an important part of research projects, and the role of miRNAs as potential highly informative molecular biomarkers of various physiological and pathological processes in the body is actively explored by the scientific community. In particular, physical activity is an important modifying factor for circulating miRNAs. Unlike classical blood biochemical parameters, which can change over time depending on the temperature and storage conditions of the sample, microRNAs remain stable during storage and even after multiple freeze-thaw cycles, which makes them an attractive and easily accessible target for detection. However, the determination of the microRNA expression profile in clinical practice is still difficult due to the high heterogeneity of analytical procedures used for testing. In sports medicine, the preanalytical stage is especially important, since often the conditions for sampling are not standardized and can affect the analysis result. This review shows the role of miRNAs as new sensitive biomarkers of the effectiveness of the training process and regulators of the body’s response to physical activity, and also discusses some preanalytical aspects of the analysis of miRNA expression profiles.