Performance & metabolism in mice: SRF knockout and wild-type mice similarly adapt to endurance exercise

Introduction: Physical exercise has important effects as second- ary prevention or intervention against several diseases. Endurance exercise induces local and global effects, resulting in skeletal muscle adaptations to aerobic activity and an ameliorated muscle performance, and prevents muscle loss. Serum response factor (Srf) is a transcription factor of pivotal importance for muscle tis- sues and animal models of Srf genetic deletion/over-expression are widely used to study Srf role in muscle homeostasis, physiol- ogy and pathology. A global characterisation of exercise adapta- tion in the absence of Srf has not been reported. Methods: We measured body composition, muscle force, running speed, energy expenditure and metabolism in WT and inducible skeletal muscle-specific Srf KO mice, follow- ing three weeks of voluntary exercise by wheel running. Results: We found a major improvement in the aerobic ca- pacity and muscle function in WT mice following exercise, as expected, and no major differences were observed in Srf KO mice as compared to WT mice, following exercise. Conclusion: Taken together, these observations suggest that Srf is not required for an early (within 3 weeks) adaptation to spontaneous exercise and that Srf KO mice behave similarly to the WT in terms of spontaneous physical activity and the resulting adaptive responses. Therefore, Srf KO mice can be used in functional muscle studies, without the results being biased by the lack of Srf.