Dietary selenium and prolonged exercise alter gene expression and activity of antioxidant enzymes in equine skeletal muscle.

The study investigated the effect of dietary selenium on the gene expression and activity of antioxidant enzymes in untrained horses, suggesting that selenium may assist in reducing oxidative muscle damage and promote postexercise recovery.

Introduction

• This research aimed to understand the influence of different levels of dietary selenium intake on the antioxidant gene expression and enzyme activity in the blood and skeletal muscles of horses undergoing prolonged exercise.

Methods

• The study involved 12 untrained Thoroughbred horses who were administered selenium in doses of 0.1 mg/kg (lower dose) and 0.3 mg/kg (higher dose) dry material (DM) through their diet for 36 days.
• The experimental diet comprised coastal bermudagrass hay, whole oats, and a mineral/vitamin premix without selenium. The selenium was added separately to achieve the targeted dosage.
• On the 35th day, the horses performed two hours of submaximal exercise in a free-stall exerciser.
• The researchers collected blood samples before and after 34 days of selenium supplementation, post-exercise, and at subsequent 6 and 24-hour intervals.
• Skeletal muscle biopsies were also taken at corresponding intervals.

Findings

• The horses receiving the higher selenium dosage showed increased serum selenium and muscle thioredoxin reductase (an antioxidant enzyme) activity.
• The selenium dosage did not affect glutathione peroxidase (another antioxidant enzyme) activity in resting horses’ plasma, red blood cell, or muscles.
• Post-exercise, the selenium-fed horses displayed lesser serum lipid hydroperoxides (a measure of oxidative stress) compared to the control group, suggesting that selenium may decrease oxidative muscle damage.
• Despite the increase in muscle thioredoxin reductase activity with higher selenium intake, this did not cause a corresponding change in the gene expression of the enzyme, demonstrating a disconnect between selenium-influenced changes in gene expression and enzyme activity.
• Similarly, glutathione peroxidase activity increased in plasma and decreased in red blood cell lysate post-exercise but did not change in the muscles at any point.

Conclusion

• The research concludes that selenium supplementation can increase horses’ antioxidant status and may assist in lessening oxidative muscle damage and aiding post-exercise recovery. However, the actual alignment between gene expression changes and their corresponding enzyme activities remains unclear, necessitating further research.