Effects of metformin hydrochloride on blood glucose and insulin responses to oral dextrose in horses.

This research investigates the impacts of the drug metformin on plasma glucose concentration and insulin responses following consumption of dextrose in horses. The study found that metformin significantly reduced glycemic and insulinaemic responses, both in healthy horses and in horses with induced insulin resistance.

Research Methodology

• Seven healthy Standardbred and Thoroughbred geldings participated in this study. The researchers carried out an oral dextrose challenge test on each horse four times, under different circumstances: without any treatment, with metformin alone, after inducing insulin resistance with dexamethasone, and with metformin after inducing insulin resistance.
• The administration of metformin, at a dosage of 30 mg/kg body weight, was done via a nasogastric tube one hour prior to providing the dextrose to the horses.
• Glucose and insulin concentrations in the horses’ plasma/serum were measured at regular intervals during each test.
• For the statistical analysis, the researchers used linear mixed models for each predetermined outcome variable. In each model, the ‘treatment’ was included as a fixed effect with four categorical levels, namely none, metformin, dexamethasone, and dexamethasone with metformin. The horse variable was accounted for as a random effect.

Key Findings

• In healthy horses, the use of metformin led to a significant decrease in peak glucose concentration, area under the glucose curve, and insulin concentration 120 minutes post dextrose administration.
• Once insulin resistance was induced, using metformin resulted in significant differences in peak glucose concentration, the percentage increase in glucose concentration, the area under the glucose curve, and insulin concentration at 120 and 150 minutes after administering dextrose.

Implications and Future Directions

• Metformin appears to significantly reduce glycemic and insulinaemic responses, in both healthy horses and those with insulin resistance produced in a laboratory setting. Therefore, metformin might be beneficial for horses with naturally acquired insulin resistance, by minimizing glycemic and insulinaemic responses to nonstructural carbohydrates in their diet.
• The authors suggest that further research is necessary to understand the exact mechanisms by which metformin acts in horses, and recommend conducting controlled clinical trials.