Mitochondria isolated from male skeletal muscle contain a small and distinct population of microRNA that are differentially expressed following acute endurance exercise

Initially thought to localise at the cytosol and nucleus only, emerging evidence indicates that miRNAs also localise within the mitochondria where they could regulate diverse pathological and physiological processes. Therefore, the aim of the current study was to use small RNA sequencing to profile the entire population of miRNAs in human skeletal muscle of healthy males in isolated mitochondria and whole-tissue in response to acute endurance exercise. Twelve healthy males (age 26 ± 4 years, mean ± SD) cycled for 60 min at 70% VO2peak and muscle biopsies were collected at rest, immediately after and 3 h after exercise. The mitochondria were isolated by immunoprecipitation, further purified, then the resident RNA was sequenced to assess the mitochondrial transcriptome. Small RNA sequencing revealed that mitochondria isolated from male skeletal muscle tissue contain a small and distinct population of miRNAs. Of the approximately 110 mature miRNAs detected in skeletal muscle mitochondria at each time-point, the canonical myo-miRs miR-1, miR-133 and miR-206 families constituted on average 45% of total mitochondria miRNA reads. However, none of the canonical myo-miRs were differentially expressed in mitochondria following endurance exercise. Future research is now required to investigate miRNA-mRNA interactions in the mitochondria of skeletal muscle tissue.