The study focused on the effect of pergolide, a dopaminergic agonist, on horses with a common endocrine disorder called Pituitary pars intermedia dysfunction (PPID), specifically looking at muscle mass and regulation of skeletal muscle proteolysis. Despite the hypothesis that pergolide treatment could improve muscle atrophy and proteolysis markers, the results suggest the treatment may contribute to weight loss and improved insulin regulation in horses with PPID, but does not affect muscle mass or proteolysis markers.

Introduction to the Research

• The research investigated the effects of an endocrine disorder in horses known as Pituitary pars intermedia dysfunction (PPID). This disorder frequently affects aged horses, with one of the symptoms being muscle atrophy, or the wasting away of muscle tissue.
• Specifically, the researchers wanted to examine the correlation between muscle mass and the regulation of skeletal muscle proteolysis (the breakdown of proteins) in horses with PPID and muscle atrophy.
• A significant part of the study involved analyzing the impact of a dopaminergic agonist known as pergolide on PPID horses. The initial hypothesis was that the muscle atrophy witnessed in PPID was a result of an increase in proteolysis, and that markers indicating this proteolysis and muscle atrophy would show improvement with pergolide treatment.

Methodology

• For accurate comparisons, the researchers studied different markers such as muscle atrophy, adiposity (obesity), insulin regulation, skeletal muscle composition, and proteolysis in two groups of horses — those with PPID and others without the disorder (control group).
• The PPID horses were then treated for 12 weeks either with pergolide or a placebo. The pergolide dose was adjusted based on monthly adenocorticotropin measurements. The same markers mentioned above were compared again after the 12 weeks of treatment.

Findings and Conclusion

• The results showed a higher transcript abundance of muscle RING finger 1 (MuRF1) in PPID horses compared to the control group. This suggests an increase in proteolysis in these horses.
• However, the pergolide treatment did not show any observable difference in transcript abundance of proteolysis markers, contradicting the original hypothesis.
• Interestingly, the pergolide treated horses exhibited weight loss and improved fasting insulin regulation, while those given the placebo gained weight and rump fat thickness.
• The major takeaway from this study is that despite the assumed impacts, pergolide treatment does not seem to affect muscle mass or markers of muscle proteolysis in horses with PPID. Instead, it may promote weight loss and improve insulin regulation.