The role of myostatin and the calcineurin-signalling pathway in regulating muscle mass in response to exercise training in the rainbow troutOncorhynchus mykissWalbaum

Abstract

SUMMARY Rainbow trout Oncorhynchus mykiss Walbaum were exercised at 0.8 and 1.6 body lengths s-1 for 18 h a day over a 30 day period. Exercise resulted in a 24-30% increase in the average cross-sectional area of fast muscle fibres relative to tank-rested controls. The concentrations of growth factors and transcription factors hypothesised to play a role in regulating exercise-induced muscle fibre hypertrophy were measured. Exercise training resulted in a minor increase in calcineurin localisation in the nucleus. However, nuclear factor of T-cells 2 (NFAT2) nuclear localisation did not follow a pattern that was consistent with NFAT2-mediated transcriptional activity and changes in calcineurin signaling. The active peptide of myostatin, a negative regulator of muscle growth in mammals, was downregulated in exercise groups relative to tank-rested controls, but only by 6-7%. It was concluded that myostatin and calcineurin signaling do not play a major role in regulating exercise-induced muscle hypertrophy in trout.

Environment and plasticity of myogenesis in teleost fish

“…The latter event is thought to synergistically initiate a programme of gene expression leading to fibre hypertrophy (Musaro et al, 1999;Semsarian et al, 1999). However, exercise training leading to fast muscle hypertrophy in the rainbow trout only resulted in a minor increase in calcineurin localisation in the nucleus and total NFAT2 concentration decreased relative to tank-rested controls with no nuclear translocation (Martin and Johnston, 2005). These results indicate differences in the response of this signalling pathway to exercise stimuli between teleosts and mammals.…”

Migration- and exercise-induced changes to flight muscle size in migratory birds and association withIGF1andmyostatinmRNA expression

“…In other mammalian studies, muscle myostatin expression has paradoxically increased in response to training or overloading in skeletal or cardiac muscle (Sakuma et al, 2000;Willoughby, 2004;Matsakas et al, 2006;Jensky et al, 2007;Jensky et al, 2010). In rainbow trout (Oncorhynchus mykiss), Martin and Johnston found a significant decrease in myostatin protein in response to training, but the magnitude of the decrease was so small (6%) that they concluded myostatin played no more than a minor role in regulating muscle mass after exercise (Martin and Johnston, 2005). Our results from starlings exercising in a wind tunnel demonstrate traininginduced muscle hypertrophy, yet no decrease in myostatin mRNA expression in response to either acute exercise or 2 weeks of flight training; in fact, myostatin mRNA expression trended higher immediately after a long-duration flight compared with trained and untrained animals.…”

“…Resistance training and endurance exercise can result in increased muscle size as muscles acclimate to increased workload (Roth et al, 2003;Walker et al, 2004;Willoughby, 2004;Martin and Johnston, 2005). Exercise and training have also been associated with decreased expression of myostatin mRNA and protein in humans (Roth et al, 2003;Raue et al, 2006;Louis et al, 2007) and rats (Matsakas et al, 2005;Matsakas et al, 2006;Heinemeier et al, 2007), although this finding has not been consistent.…”

Effects of prolonged exercise training and exhaustive chasing training on the swimming performance of an endangered bream Megalobrama pellegrini

“…have been extensively studied (Johnston & Moon 1980, Martin & Johnston 2005, He et al 2013. Some studies have found that the im provement of U crit was accompanied by the enhancement of aerobic metabolic capacity in trained fish (Liu et al 2009, Li et al 2010b.…”