Acute physical stress increases serum levels of specific microRNAs

Introduction: MicroRNA (miR) is non-coding small RNA that regulate mRNA at the post-transcriptional level by degradation or inhibition. To find physical stress markers, we developed a rat model involving a simple and complicated stress and measured serum miR levels. Materials and Methods: To demonstrate changes in serum miR levels when physical stress is applied, we constructed three stress modalities using rats: alcohol intake, treadmill running and restraint. After alcohol administration, the rats were made to run on a treadmill and some of the rats were further stressed by restraining with a 2 kg water bag immediately after the treadmill run. The rats were grouped as follows: control, run for 20 min, run for 90 min, run and restrained for 20 min, run and restrained for 90 min. Using total RNA extracted from sera, expression levels of eight miRs were measured by real-time PCR. Results: The level of miR-199a was increased by 20 min stress procedures and the levels of miR-1, miR-24a and miR-133a/b were increased by 90 min stress procedures. No change in the levels of miR-208, miR-212 or miR-296-5p was seen under any stress conditions. There was no significant difference between a treadmill run only and a combination of treadmill run and being restrained by a 2 kg water bag. Discussion: We demonstrated that a combination of these serum miRs might indicate the intensity of stress experienced.