Abundance of the skeletal muscle Glut-4 glucose transport protein in Standardbred foals during development and exercise

Abstract

The objective of this study was to investigate the changes in Glut-4 expression in gluteus muscle, and in the plasma concentrations of hormones and metabolites during the suckling period, after weaning, and after exercise training in foals. Our hypotheses were Glut-4 abundance will decrease following metabolite and hormonal concentration between neonatal period and late development but will increase with exercise training. Eight clinically normal Standardbred foals were used in this study, and they stayed with their mothers from birth until weaning at 6 months. After weaning, the foals were randomly divided in two groups: an exercise group (EX) (n=4; ~282 kg) which trained 3 d/wk for 12 wks and a control group (n=4; ~271 kg) without structured exercise. Venous blood samples were obtained immediately after birth (<30 min), at 24 h, at day 7 and day 14, and at 1, 3, 6, 9 and 12 months after parturition. Results were analysed using one-way ANOVA for repeated measures. Post-hoc differences were identified using the Tukey test and correlations were obtained using Pearson product moment analysis. The abundance of Glut-4 in skeletal muscle was highest immediately after birth and with growth and development (P<0.05). Exercise training did not change Glut-4 abundance (P>0.05). Plasma lactate, insulin and cortisol concentrations decreased during the first three months of lactation while glucose and leptin concentrations increased (P<0.05). There were no effects of exercise training on any of the above plasma parameters (P>0.05). In conclusion, Glut-4 abundance in gluteus muscle was highest at the birth and decreased during development and exercise training for 12 weeks did not change its’ abundance.