Cross-training in birds: cold and exercise training produce similar changes in maximal metabolic output, muscle masses and myostatin expression in house sparrows,Passer domesticus

Abstract

Maximal metabolic outputs for exercise and thermogenesis in birds presumably influence fitness through effects on flight and shivering performance. Because both summit (M sum , maximum thermoregulatory metabolic rate) and maximum (MMR, maximum exercise metabolic rate) metabolic rates are functions of skeletal muscle activity, correlations between these measurements and their mechanistic underpinnings might occur. To examine whether such correlations occur, we measured the effects of experimental cold and exercise training protocols for 3 weeks on body (M b ) and muscle (M pec ) masses, basal metabolic rate (BMR), M sum , MMR, pectoralis mRNA and protein expression for myostatin, and mRNA expression of TLL-1 and TLL-2 (metalloproteinase activators of myostatin) in house sparrows (Passer domesticus). Both training protocols increased M sum , MMR, M b and M pec , but BMR increased with cold training and decreased with exercise training. No significant differences occurred for pectoralis myostatin mRNA expression, but cold and exercise increased the expression of TLL-1 and TLL-2. Pectoralis myostatin protein levels were generally reduced for both training groups. These data clearly demonstrate cross-training effects of cold and exercise in birds, and are consistent with a role for myostatin in increasing pectoralis muscle mass and driving organismal increases in metabolic capacities.

Acute cold and exercise training upregulate similar aspects of fatty acid transport and catabolism in house sparrows, Passer domesticus

“…exercise-training effects on both exercise and thermogenic performance and cold-training effects on both thermogenic and exercise performance) have been observed in both birds (Petit and Vézina, 2014;Zhang et al, 2015b) and mammals (Schaeffer et al, 2001;Boström et al, 2012). For example, Zhang et al (Zhang et al, 2015a) documented that cold-and exercisetraining protocols increased maximal organismal metabolic capacities for both the trait of training (e.g.…”

“…CPT activities or levels were up-regulated during exercise training in skeletal muscle of both mammals (Starritt et al, 2000;Tunstall et al, 2002;Bruce et al, 2006) and birds (Price et al, 2010). Moreover, pectoralis CPT activities were also elevated during migration (Guglielmo et al, 2002;McFarlan et al, 2009), but not for winter acclimation (Zhang et al, 2015b) or for temperature and photoperiod manipulations in captive winteracclimatized birds (Swanson et al, 2014b).…”

“…The effects of exercise training on skeletal muscle FAT/ CD36 and FABP pm levels are incompletely resolved, with studies showing either elevated (Tunstall et al, 2002;Talanian et al, 2010) or stable Price et al, 2010) FAT/CD36 and FABP pm levels after training in both mammals and birds. Moreover, migration (McFarlan et al, 2009) and winter acclimatization (Zhang et al, 2015b) are both associated with higher FAT/CD36 and/or FABP pm levels in birds.…”

“…Consequently, capacities for nonesterified fatty acid (NEFA) uptake into the myocyte, their subsequent transport to and across mitochondrial membranes, and β-oxidation are potential regulatory steps for both shivering (Swanson, 2010;Zhang et al, 2015b) and exercise performance (Kiens, 2006;Guglielmo, 2010). Once circulating NEFA reach the myocyte, plasma membrane-bound fatty acid binding protein (FABP pm ) and fatty acid translocase (FAT/CD36) cooperate to transport NEFA across the endothelium, the interstitial space, and the sarcolemma to enter muscle cells (Kiens, 2006;Glatz et al, 2010).…”

“…Moreover, FABP c also acts as an intramyocyte fatty acid receptor and may potentially limit fatty acid uptake (Glatz et al, 2010). Most exercise training protocols have failed to change FABP c levels in both birds (Price et al, 2010) and mammals Lee et al, 2007), but studies of migration (Guglielmo et al, 2002;McFarlan et al, 2009) and winter acclimatization (Zhang et al, 2015b) showed that increases in pectoralis FABP c levels are consistent contributors to enhanced flight and shivering performance in birds. Because mobilization, transport and catabolism of exogenous fatty acids are more important for support of prolonged muscular activity in birds than in mammals (Jenni-Eiermann et al, 2002;Guglielmo, 2010;Swanson, 2010), examination of the effects of both cold and exercise training on FABP c levels in birds would be worthwhile.…”