Glucose infusion attenuates endogenous glucose production and enhances glucose use of horses during exercise.

This research investigates the impact of increased glucose availability on glucose kinetics and the use of glucose in horses during exercise. It was found that infusing glucose reduced the body’s glucose production and increased its use during low-intensity workouts, but it did not influence muscle glycogen usage.

Research Objective and Methodology

• The primary aim of this research was to analyze the effects of increased glucose availability on glucose kinetics (the way glucose moves and changes within the body) and substrate utilization (the use of basic molecules to provide energy).
• Field: Six conditioned horses were selected to participate in the study.
• Procedure: The horses ran on a treadmill for 90 minutes at a level that equated to approximately 34% +/- 1% of their maximum oxygen uptake. This process was repeated in two trials – in one, glucose was infused into the horses, and in the other, an equivalent volume of isotonic saline (which does not contain glucose was infused.

Key Findings

• During the glucose trial, blood sugar increased during exercise, whereas it remained largely the same in the control trial.
• The horse’s own glucose production (HGP) rose during exercise in the control test, peaking after 90 minutes. Conversely, glucose infusion partially suppressed this increase in HGP, with the peak value being significantly lower than in the control.
• The infusion led to twofold higher glucose utilization (rate of disappearance) than the control trial between 30 and 90 minutes of exercise.
• Despite higher glucose utilization in the glucose trial, muscle glycogen usage remained similar between both trials, suggesting that added glucose does not affect how the horse’s muscles utilize their glycogen stores during low-intensity exercise.

Conclusions

• The research concluded that introducing additional glucose during low-intensity exercise marginally suppresses the horse’s own glucose production.
• This glucose infusion helps to slow down the decline in carbohydrate burning during such workouts.
• The study, however, found that this increased glucose availability didn’t affect how horse muscle uses glycogen – a primary fuel source during exercise.