Single-injection glucose kinetics with compartmental modelling during rest and low-intensity exercise in horses.

The research presents a method to understand glucose metabolism in horses during rest and endurance type exercise using a single injection technique and compartmental modeling. The findings demonstrate how exercise significantly increases the rate constants, transport flows and the plasma glucose clearance rate while reducing turnover times and mean residence times.

Investigating Glucose Kinetics in Horses

• The study was carried out to re-assess the models of glucose kinetics in horses not only at rest but also during endurance type exercises.
• 12 exercise-trained Arabian geldings were given a bolus of 100 µmol/kg bwt [6,6-(2) H]glucose intravenously during rest and while running at ∼ 4 m/s on a treadmill.
• The researchers used a single injection technique and compartmental modeling to assess glucose kinetics. This technique allows researchers to trace glucose availability to body tissues and its utilization, providing a detailed understanding of glucose metabolism.

Impact of Exercise on Glucose Transport

• The researchers found that exercise resulted in a boost in all rate constants and transport flows for glucose between compartments by a wide margin ranging between 110-145%. This increase was statistically significant with P values less than or equal to 0.004.
• The total glucose transport through the system experienced an elevation from 8.9 ± 0.6 µmol/min/kg/bwt at rest to 25.0 ± 1.1 µmol/min/kg bwt during exercise. This is a drastic change and is statistically significant (P < 0.001).

Exercise Alters Glucose Compartments and Clearance Rate

• Exercise displayed a negative effect on the volume of the primary glucose compartment by shrinking it by 8% (P = 0.006).
• Interestingly, the plasma glucose clearance rate saw a near 200% increase because of exercise (p-value < than 0.001). The clearance rate is the measure of the volume of plasma from which a substance is removed by the kidneys per unit time. This increase suggests that glucose elimination is more efficient during physical activity.

Turnover Times and Rates

• The duration of glucose presence within the body, reflected by turnover times and mean residence times, was reduced approx by 60% due to exercise (P < 0.001).
• On the other hand, turnover rates experienced an increased 125% (P < 0.001). Turnover rate refers to the speed at which a compound (in this case glucose) is renewed in a defined system.
• The results suggest exercise not only stimulates glucose utilisation but also promotes more rapid replenishment.

Conclusion and Future Implications

• A single injection technique coupled with compartmental modelling is seen as an effective way to quantify the availability and use of glucose by tissues.
• This method could be useful for future research looking at the role of glucose metabolism in equine exercise performance and metabolic disease.