Mitochondrial DNA lesions and copy number are strain dependent in endurance-trained mice.
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In this pilot work, we selected two inbred strains that respond well to endurance training (ET) (FVB/NJ, and SJL/J strains), and two strains that respond poorly (BALB/cByJ and NZW/LacJ), to determine the effect of a standardized ET treadmill program on mitochondrial and nuclear DNA (nucDNA) integrity, and mitochondrial DNA (mtDNA) copy number. DNA was isolated from plantaris muscles (n=37) and a gene-specific quantitative PCR-based assay was used to measure DNA lesions and mtDNA copy number. Mean mtDNA lesions were not different within strains in the sedentary or exercise-trained states. However, mtDNA lesions were significantly higher in trained low-responding NZW/LacJ mice (0.240.06 mtDNA lesions/10Kb) compared to high-responding strains (mtDNA lesions/10Kb: FVB/NJ=0.110.01, p=.049; SJL/J=0.040.02; p=.003). ET did not alter mean mtDNA copy numbers for any strain, although both sedentary and trained FVB/NJ mice had significantly higher mtDNA copies (99,8904,884 mtDNA copies) compared to low-responding strains (mtDNA copies: BALB/cByJ=69,7444,675; NZW/LacJ=65,6875,180; p<.001). ET did not change nucDNA lesions for any strain, however, SJL/J had the lowest mean nucDNA lesions (3.50.14 nucDNA lesions/6.5Kb) compared to all other strains (nucDNA lesions/6.5Kb: FVB/NJ=4.40.11; BALB/cByJ=4.70.09; NZW/LacJ=4.40.11; p<.0001). Our results demonstrate strain differences in plantaris muscle mtDNA lesions in ET mice and, independent of condition, differences in mean mtDNA copy and nucDNA lesions between strains.
