Developmental regulation of the activation of translation initiation factors of skeletal muscle in response to feeding in horses.

The research article investigates how the activation of certain translation initiation factors in horses’ skeletal muscles, in response to feeding, varies with the age of the horses. The factors studied are protein kinase B, S6K1, rpS6, and eukaryotic initiation factor 4E binding protein 1. The researchers showed that consuming food enhances the activation of these factors, especially among yearlings, suggesting that the muscle mass growth seen during growth phases may stem from heightened muscle protein synthesis rates in response to food.

Methodology

• The researchers studied 18 horses, divided into three age groups; 6 yearlings, six 2-year-old horses, and 6 mature horses.
• The horses underwent an 18-hour period of fasting. After this period, they were either given a high-protein meal (2g/kg of their body weight) or continued fasting.
• The researchers took blood samples throughout the experiment to measure plasma concentrations of glucose, insulin, and amino acids. They also collected biopsy specimens from a gluteal muscle at 90 minutes post-feeding to measure the phosphorylation state of the translation initiation factors.

Findings

• The postfeeding state resulted in elevated plasma concentrations of glucose, insulin, and amino acids, regardless of the horses’ age.
• Phosphorylation of protein kinase B, S6K1, rpS6, and the eukaryotic initiation factor 4E binding protein 1 was higher postfeeding.
• Age had an impact on the phosphorylation of S6K1 at Thr(389) and rpS6 at Ser(235/236). Increased phosphorylation was seen in the yearlings and mature horses compared to the 2-year-old horses.

Conclusions

• The researchers concluded that eating resulted in increased activation of the studied translation initiation factors. This activation was most noticeable in the yearlings.
• These findings suggest that the increased muscle mass observed during growth periods may result from heightened muscle protein synthesis rates in response to feeding. This can be used to understand physiological changes during growth and help optimize feeding practices for growing horses.