Effects of leucine or whey protein addition to an oral glucose solution on serum insulin, plasma glucose and plasma amino acid responses in horses at rest and following exercise.

The research study looks into how the addition of leucine or whey protein to a glucose solution can affect insulin responses and other factors in horses both at rest and after exercise. Notably, leucine, not whey protein, was found to increase the insulin response to an oral glucose load.

Research Objective and Methods

The goal of the research was to understand whether the addition of whey protein or leucine to a glucose solution impacts the insulin, glucose, and amino acid responses in horses post-exercise or at rest.

• The researchers studied six mature, conditioned Thoroughbreds. They administered a nasogastric gavage that contained either a glucose solution alone, or with the addition of whey protein or leucine.
• These administrations took place both after a round of exercise on a high-speed treadmill and during rest periods.
• Each horse received each of the six possible treatments, and the research team collected blood samples both before and after the procedure.

Results of the Study

The results suggested several notable differences in insulin responses and other factors based on the inclusion of leucine or whey protein, and whether the horses were at rest or had just exercised.

• Results showed a greater insulin response both at rest and after exercise in the treatment cases involving leucine, as compared to those with just glucose or glucose and whey protein.
• When compared to rest periods, after exercise, plasma glucose responses lowered in the cases of glucose alone and glucose with whey protein. This however remained the same with the inclusion of leucine.
• Following exercise, plasma alanine concentrations increased. Except for significantly raised plasma leucine concentrations after treatments involving leucine, the plasma concentrations of indispensable amino acids decreased after the procedure.

Conclusions

The research study concludes that, not whey protein, but the addition of Leucine to a glucose solution increased the serum insulin response. The study suggests that the role of leucine in boosting the rate of post-exercise muscle glycogen synthesis in horses should be investigated further.