Impaired aerobic capacity and premature fatigue preceding muscle weakness in the skeletal muscle Tfam KO mouse model

International audienceMitochondrial diseases are genetic disorders leading to an impaired mitochondrial function and resulting in exercise intolerance and muscle weakness. In patients, muscle fatigue due to defects in mitochondrial oxidative capacities commonly precedes muscle weakness. In mice, the fast-twitch skeletal muscle-specific Tfam deletion (Tfam KO) leads to deficit in the respiratory chain activity, severe muscle weakness and early death. Here, we performed a time-course study of mitochondrial and muscular dysfunctions in 11 and 14 weeks Tfam KO mice, i.e., before and when mice are about to enter the terminal stage, respectively. While force in the unfatigued state was reduced in Tfam KO mice as compared to control littermates (WT) only at 14 weeks, during repeated submaximal contractions fatigue was faster at both ages. During fatiguing stimulation, total phosphocreatine breakdown was larger in Tfam KO muscle than in WT muscle at both ages whereas phosphocreatine consumption was faster only at 14 weeks. In conclusion, the Tfam KO mouse model represents a reliable model of lethal mitochondrial myopathy where impaired mitochondrial energy production and premature fatigue occur before muscle weakness and early death