Exercise benefits muscles and immune system
The aim of the SWIMFIT (Zebrafish as novel model for exercise-enhanced skeletal and cardiac muscle growth and immune functioning) project was to demonstrate mechanisms behind beneficial effects of swimming. Experiments were conducted into exercise-enhanced skeletal muscle growth, cardiac muscle growth and immune functioning. Swimming experiments showed a significant increase in fibre cross-sectional and vascularisation in exercised compared to non-exercised fish. Furthermore, gene expression profiling by microarray analysis revealed complex transcriptional networks of extracellular and intracellular signalling molecules involved in the regulation of muscle mass and angiogenesis. Results demonstrated that exercise-induced contractile activity in zebrafish encourages a coordinated adaptive response in fast muscle leading to increased muscle mass and vascularisation. SWIMFIT posited that these phenotypic adaptations were the result of extensive transcriptional changes induced by exercise. Studies were also conducted into exercise enhanced cardiac muscle growth and transcriptomic response in zebrafish. They identified more than 700 differentially expressed genes, providing insights into the molecular adaptive mechanisms taking place in the zebrafish heart in response to swimming induced activity. An investigation into exercise-enhanced immune functioning showed that exercised fish are physiologically different in their molecular response to bacterial infection in the white muscle compared to non-exercised fish. This led to the conclusion that while resting fish switch off developmental processes in response to immune challenges exercised fish do not. in addition wild-type zebrafish subjected to exercise were shown to be heavier and had higher levels of cortisol compared to non-exercised controls. In mutants exercise resulted in larger growth enhancement than wild-type fish, suggesting that cortisol acts as a brake on exercised enhanced growth in wild-type fish. SWIMFIT provided new insights into effects of exercise on skeletal and cardiac muscle growth, immune functioning and cortisol stress response, benefiting both medical biology and sustainable aquaculture. Furthermore, SWIMFIT has created a new field of study by combining this new line of research into exercise physiology with high throughput genomic techniques.
