Effect of growth on monocarboxylate transporters and indicators of energy metabolism in the gluteus medius muscle of Thoroughbreds.

This research focuses on evaluating the changes in monocarboxylate transporters and energy metabolism indicators in the gluteus medius muscle of Thoroughbreds with growth. The findings of the study suggest that the lactate usage capacity and oxidative capacity in Thoroughbreds increase with growth.

Objective and Methodology

The objective of this study was to investigate the alterations in monocarboxylate transporter (MCT) 1 and MCT4 content, and various markers of energy metabolism in the gluteus medius muscle of Thoroughbreds during their growth period. The study was conducted on a sample of six Thoroughbreds comprising three males and three females.

• Muscle samples from the gluteus medius were collected when the horses were 2, 6, 12, and 24 months old.
• The muscle proteins were then separated through a process known as SDS-PAGE.
• Level of MCT1 and MCT4, and the content of peroxisome proliferator-activated receptor-γ coactivator-1α (a crucial factor in mitochondrial biogenesis and energy metabolism) were then determined using a technique called western blotting.
• Parallelly, the muscle activities of phosphofructokinase (a glycolytic enzyme) and citrate synthase (a TCA cycle enzyme) were also measured biochemically.
• The different forms of lactate dehydrogenase, called isoenzymes, were separated by agarose gel electrophoresis and quantified.

Results

The findings from the analyses conducted can be summarized as follows:

• The MCT1 protein content in the muscle samples taken when the horses were 24 months old was found to be significantly higher than that when they were 2 months old. However, no such change in MCT4 protein content was detected during the study period.
• The content of peroxisome proliferator-activated receptor-γ coactivator-1α was also significantly increased at the 24-month marker.
• Interestingly, the activity of citrate synthase increased at 6 and 24 months of age as compared to the levels at 2 months of age.
• No change in phosphofructokinase activity was observed during the growth period.
• The relative contribution of lactate dehydrogenase 1 and 2 isoenzymes to the total amount of all its five types was found to be significantly higher at 12 and 24 months than that at two months.

Conclusion

The study concludes that the observed changes in protein contents of MCTs and the lactate dehydrogenase isoenzyme profile suggests that lactate usage capacity increases with growth. In addition, an increase in the oxidative capacity in Thoroughbreds was also seen. This understanding could be critical for developing training or dietary programs for racehorses.