Effect of short-term dopamine reduction on insulin sensitivity and post-prandial insulin and glucose responses in Standardbred horses.

The research article is about the effect of dopamine reduction on insulin sensitivity in horses, specifically Standardbred horses, and their post-meal insulin responses.

Objective of the Study

• The primary aim of this study was to understand and explore the role dopamine plays in the regulation of insulin secretion in horses. The researchers used a dopamine reducer to measure changes in insulin sensitivity and post-meal insulin responses in the study subjects, six healthy Standardbred horses.

Methodology of the Study

• The researchers used alpha-methyl-para-tyrosine (AMPT), a tyrosine hydroxylase inhibitor that reduces dopamine production, to study its impacts on insulin sensitivity and post-prandial (after meal) insulin response to a glucose-containing meal.
• They conducted a placebo-controlled randomised crossover study, in which each horse was administered either one dose of AMPT (40 mg/kg) or a placebo orally. The horses were then subjected to an oral glucose test (OGT) and a frequently sampled intravenous glucose tolerance test (FSIGTT).
• The reduction of dopamine through AMPT was confirmed by measuring an increase in plasma prolactin concentration and the absence of a post-meal increase in plasma dopamine concentration compared to the placebos.

Findings of the Study

• The post-meal insulin responses, including both peak and AUCi (area under the insulin curve), were found to increase after the administration of AMPT when compared to the placebo. However, it did not affect the blood glucose concentrations in horses.
• It was found that one dose of AMPT did not impact tissue sensitivity as evaluated through the FSIGTT.
• The study discovered that dopamine plays a role in regulating insulin secretion in horses, establishing that a post-meal release of dopamine into the bloodstream may inhibit pancreatic insulin secretion.

Future Directions

• The research calls for further studies to conduct an extensive evaluation of different dosing protocols for AMPT. It also encourages additional research to explore the correlation between PPID, ID and the risk of laminitis in horses in order to deepen understanding on the subject.