Epinephrine inhibits exogenous glucose utilization in exercising horses.

The study focuses on how pre-exercise glucose intake and the subsequent infusion of epinephrine can impact carbohydrate metabolism during exercise in horses.

Research Context

In an effort to understand the metabolism of carbohydrates in horses under physical exertion, the researchers tested the effects of administering glucose before any physical activity, with and without an additional epinephrine shot into the animals. The experiment set up involved exerting six horses for 60 minutes on a treadmill. This exertion occurred once after the horses were given oral glucose, once after oral glucose and epinephrine, and once after they received only water.

Research Outcomes

• Glucose intake, whether alone or alongside epinephrine, caused both hyperinsulinemia (excess levels of insulin in the blood) and hyperglycemia (elevated blood sugar levels) in the horses.
• Greater levels of epinephrine were observed in the trials when this hormone was directly administered.
• It was also reported that the oral glucose administration increased the glucose rate of appearance by approximately 50% during exercise compared to the trials with only water intake. However, this increase was lower (around 33%) when epinephrine was infused.
• The glucose rate of disappearance was two times higher in horses with an intake of glucose only than that in horses fed with only water. However, this increase in glucose uptake was entirely inhibited when the glucose intake was alongside an epinephrine infusion.
• The study also showed that muscle glycogen utilization was significantly higher when both glucose and epinephrine were administered together, in comparison to when only glucose or water was given.

Conclusion

In conclusion, the researchers stated that the administration of glucose before exercise intensifies the use of plasma glucose during moderate-intensity activity but does not alter the usage of muscle glycogen. They also concluded that heightened levels of epinephrine in the body can inhibit the increase in the rate of glucose disappearance connected to pre-exercise glucose intake and can result in greater reliance upon muscle glycogen for energy conversion.