Voluntary wheel exercise alters the levels of miR-494 and miR-696 in the skeletal muscle of C57BL/6 mice

The discovery of miRNAs has brought the focus of physiologists to post-transcriptional regulation of the skeletal muscle. However, the field of how miRNAs are involved in regulating mitochondrial biogenesis and apoptosis of the skeletal muscle following endurance training is still in its infancy. Twelve male C57BL/6 mice were randomly assigned to either control group (Group C) or voluntary wheel running group (Group E). The Group C was housed in cages mounted with fixed wheels, while mice of Group E were allowed to run on wheels freely for 8 weeks. It was found that miR-494 and miR-696 were significantly decreased in the gastrocnemius muscle after 8 week voluntary wheel exercise, accompanied with an increase in the mRNA expression of NRF1, BIM and Bcl-XL, an increase in the protein content of PGC-1α, and a decrease in the protein content BIM. The lack of correlation between miR-494 and TFAM and BIM, as well as between miR-696 and PGC-1α suggests that even though miR-494 and miR-696 are sensitive miRNAs in response to exercise training, other factors or miRNAs might also be important during the regulation of mitochondrial biogenesis and apoptosis.