Dietary energy source and physical conditioning affect insulin sensitivity and skeletal muscle glucose metabolism in horses.

The research explores how different dietary energy sources and physical conditioning affect insulin sensitivity and glucose metabolism in horses’ skeletal muscles. The study found that while high-starch feeds reduced insulin sensitivity in untrained horses compared to high-fat feeds, exercise training mitigated this effect.

Objective of the Study

The study aimed to explore how high-starch and high-fat diets impact training-related changes in horses’ insulin sensitivity, skeletal muscle GLUT4 protein, and activities of hexokinase and glycogen synthase enzymes.

Research Methodology

• The research involved tri-phasic testing on horses.
• In the first phase, horses were given an all-forage diet, establishing a baseline.
• In the second phase, horses were divided into two groups. One group was given high-starch food while the other group received high-fat food for six weeks.
• The third phase included a seven-week exercise training period for both groups while continuing the assigned diets.
• Tests were conducted at the end of each phase to measure insulin sensitivity using a frequently-sampled intravenous glucose tolerance test.
• Muscle biopsies were also performed to determine the GLUT-4 protein content and the activity of hexokinase and glycogen synthase in the middle gluteal muscle.

Results and Observations

• In the high-starch group, insulin sensitivity was 36% lower after phase 2 compared to phase 1 but remained unchanged in the high-fat group.
• Following the exercise regimen in phase 3, insulin sensitivity increased in both diets compared to phase 2.
• The research also observed an increased GLUT-4 protein content and hexokinase activity in the high-starch group after phase 3.
• Glycogen synthase activities remained identical in both high-starch and high-fat groups across all the phases.

Conclusions Drawn

• The experiment concluded that while the high-starch diet decreased insulin sensitivity, moderate physical training mitigated this effect.
• Additionally, the increase in GLUT-4 protein content and hexokinase activity was concluded to potentially be a contributing factor towards increased insulin sensitivity post-training.