Multi-level analysis of aging myosin reveals decrease in muscle power without compromising overall contraction kinetics

We engineered transgenic Drosophila lines mimicking the effects of sarcopenia on myosin, which were recently elucidated by proteomic studies using elderly human skeletal muscle biopsies. We performed skinned fiber mechanics on flight muscles from young flies expressing myosin genetically modified to mimic the mutations found in humans. These experiments revealed power output decreased relative to wild-type. However, the frequency of fiber oscillation at which maximum power was generated did not differ. Muscle ultrastructure degradation did not occur until older flies engaged their flight muscles for extended periods of time. This indicates that alterations in mechanical performance precedes muscle degradation, suggesting the mutations directly and indirectly contribute to decreased muscle function with age.