Effects of short-term training on insulin sensitivity and skeletal muscle glucose metabolism in standardbred horses.

The research article discusses the effects of short-term endurance training and inactivity on insulin sensitivity and glucose metabolism in Standardbred horses.

Objective and Hypothesis

• The objective of the study was to examine the effects of a week-long endurance training and five days of following inactivity on the insulin sensitivity and muscle glucose metabolism in horses.
• The researchers hypothesized that such short-term training would improve insulin sensitivity along with increased GLUT-4 protein and the activities of glycogen synthase (GS) and hexokinase (HK), enzymes involved in glucose metabolism. However, these changes were expected to be short-lived, reverting to their original state after a five-day period of inactivity.

Methods

• Seven Standardbred horses were subjected to a seven-day training regimen, with each day comprising 45 minutes of treadmill exercise.
• The exercise intensity was set to elicit 55% of the horses’ pretraining maximal aerobic capacity, also known as VO2peak. This is a measure of the body’s ability to use oxygen during intense exercise.
• To assess insulin sensitivity, the researchers used the euglycaemic-hyperinsulinaemic clamp (EHC) method before, at 1 day and 6 days post-training. It is a technique to measure insulin-controlled glucose metabolism.
• VO2peak was evaluated before and after the training and inactivity phases.

Results

• The study found that the horses’ VO2peak increased by 9% after the training phase, and this increase was maintained even after 5 days of inactivity.
• Insulin sensitivity (Indicated by M values) was more than twice as high post-training compared to before the training. This increase persisted after the inactivity phase.
• GLUT-4 protein substantially increased after the training and remained high after inactivity.
• Glycogen synthase activity (which helps convert glucose into glycogen for storage) and hexokinase activity (which plays a key role in glucose metabolism) were also positively affected by the training phase.
• However, there was a significant decrease in muscle glycogen after the training period- indicating a greater utilization of glycogen for energy during this phase.

Conclusions

• The study concluded that short-term training had a positive impact on insulin sensitivity and glucose metabolism in horses. These benefits remained even after a few days of inactivity.
• As insulin resistance in horses is linked to obesity and risk of laminitis (a painful foot condition), the researchers suggested that regular physical activity could help in mitigating these health risks by enhancing insulin sensitivity.