Effects of exercise intensity on copy number and mutations of mitochondrial DNA in gastrocnemus muscles in mice.

The present study aimed to investigate the effects of exercise intensity on mitochondrial DNA (mtDNA) alterations of copy numbers and mutations in the gastrocnemii of mice. A total of 50 male mice were randomly divided into 5 groups; control group (K) and groups A-D, which underwent 10,30,60 and 90 min of swimming per day, respectively. Samples were obtained after 20 weeks of exercise. Total DNA was collected to analyze mutations in the mtDNA displacement loop (D-loop) regions. mtDNA content was quantified by real‑time PCR. Point mutations, monobase insertions and deletions were observed in the mtDNA D-loop regions in the skeletal muscles of the mice. A deletion of 16,232 bp was found in certain groups. The mutation base of the control group was higher than that of the exercise groups. The exercise groups demonstrated significantly altered copy numbers; the 30 min exercise group had the highest copy number. These results suggest that moderate exercise intensity reduces mutations in the mtDNA D-loop regions, and enhances the copy number of mtDNA in the gastrocnemus muscles of mice.