Increased rat neonatal activity influences adult cytokine levels and relative muscle mass.

Abstract

Little is known about the effect of physical activity in early life on subsequent growth and regulation of inflammation. We previously reported that exposure of muscles in growing rats to IL-6 results in decreased muscle growth apparently due to a state of resistance to growth factors such IGF-I and that running exercise could ameliorate this growth defect. Herein we hypothesized that increased activity, for a brief period during neonatal life, would pattern the adult rat towards a less inflammatory phenotype. Neonatal rats were induced to move about their cage for brief periods from day 5 to day 15 postpartum. Additional groups were undisturbed controls (CON) and handled (HAND). Sub-groups of rats were sampled at 30 and 65 days of age. Relative to CON and HAND, neonatal exercise (EX) results in decreased circulating levels of TNFα, IL-6 and IL-1β in adulthood, primarily in male rats. In addition, adult male EX rats had lower body mass and increased skeletal muscle mass suggesting a leaner phenotype. The results of this study suggest that moderate increases in activity early in life can influence the adult toward a more healthy phenotype with regard to inflammatory mediators and relative muscle mass.

Growth inhibition and compensation in response to neonatal hypoxia in rats

“…Finally, our studies suggest that the impact of moderate hypoxia early in life may alter growth to a greater extent through secondary mediators, such as inflammatory cytokines, than through direct effects of hypoxia on known regulatory genes such as HYOU1, HIF1α, and VEGF. These results are encouraging as we have previously found evidence that such secondary effects (such as inflammation) can be attenuated by physical activity (13, 18). …”

Early life mammalian biology and later life physical performance: maximising physiological adaptation

“…But influential circumstances during critical periods of early development are not limited to the cognitive milieu. The nascent notion that potent pre- and postnatal stimuli contribute to prolonged functional metabolic changes that can lead to physiological programming of the offspring has received substantial attention 2 3. Living organisms have an immense capability of adapting to the environment in which they find themselves.…”

“…This concept of different developmental trajectories in response to the environment is well characterised in many insect and vertebrate species 11. It is, therefore, no surprise that early physical activity levels are associated with healthier later life phenotype 2. For example, postweaning access to a running wheel prevents the development of obesity in rats prone to develop diet-induced adiposity 12.…”

“…For example, postweaning access to a running wheel prevents the development of obesity in rats prone to develop diet-induced adiposity 12. Moreover, adult rats that were physically active early in life also show lower circulating levels of inflammatory cytokines and a leaner phenotype, characterised by lower body mass, and increased lean mass 2. Horses also harness structural adaptations dictated by physical loading during early life that, in turn, translate into improved later life functional joint capacity 13.…”

“…Increasing lines of evidence support that exposure to altitude and early metabolic adjustments during critical periods of early development exert a strong influence in later life physical performance 2 3. Indeed, these factors are common features of the East Africans currently dominating marathon running – the prime archetype of a human physical endeavour.…”