Effect of moderate exercise immediately followed by induced hyperglycemia on gene expression and content of the glucose transporter-4 protein in skeletal muscles of horses.

This study researched the impact of moderate exercise and post-exercise increased sugar levels on the expression of the glucose transporter-4 (GLUT-4) protein in horse skeletal muscle. The results suggest that neither the exercise nor the combination of exercise and high sugar levels triggered changes in GLUT-4 protein production in horses.

Study Design

• The researchers conducted the study in a balanced, randomized, three-way crossover design.
• The subjects of the study were six healthy adult Thoroughbreds.
• The exercise regimen consisted of having the horses run at 45% of their maximum oxygen consumption rates for an hour.
• After the exercise, two trials were conducted: one group of horses received water, while the other received a 20% glucose solution, both administered via nasogastric intubation.
• An additional trial featured horses standing on a treadmill without any exercise – a sham exercise – followed by water administration

Assessments Carried Out

• The researchers measured muscle glycogen concentration and the content of muscle GLUT-4 protein and mRNA at multiple intervals: before exercise, and 5 minutes, 4 hours, 8 hours, and 24 hours after exercise.

Results

• The exercise regimen led to a 30% reduction in muscle glycogen concentration.
• However, there were no detectable changes in GLUT-4 protein or its mRNA content before and after exercise, indicating that exercise did not affect the production of GLUT-4 protein in horse muscle.
• The replenishment of muscle glycogen was found to be similar in both the exercised groups and remained incomplete 24 hours after the exercise.
• Horses consuming the glucose solution had substantially higher glucose and insulin concentrations in the blood for 3 hours following exercise. Despite this, the consumption of glucose didn’t show any marked impact on the GLUT-4 protein or its mRNA content in the skeletal muscle.

Conclusions

• Basing on the conducted study, the researchers concluded that neither moderate exercise nor the combination of moderate exercise followed by high sugar levels induced the transcription or translation of GLUT-4 protein in horses.