Effects of metformin hydrochloride on blood glucose and insulin responses to oral dextrose in horses.
Authors: Rendle D I, Rutledge F, Hughes K J, Heller J, Durham A E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Metformin and Glucose Regulation in Horses Insulin resistance (IR) in horses poses significant management challenges, particularly regarding dietary control and metabolic stability. Rendle and colleagues investigated whether metformin hydrochloride—an oral medication that reduces intestinal glucose absorption in other species—could attenuate the glycaemic and insulinaemic spikes that occur following carbohydrate consumption in both healthy and insulin-resistant horses. Using a crossover design, seven horses underwent dextrose challenge testing under four conditions: baseline, with metformin pretreatment (30 mg/kg administered via nasogastric tube one hour prior), following dexamethasone-induced IR, and with metformin during induced IR. Metformin produced clinically meaningful reductions in peak glucose concentration, glucose area-under-the-curve, and circulating insulin at 120 minutes post-dextrose in healthy horses, with even more pronounced effects in insulin-resistant animals—suggesting the drug's benefits may be greatest in horses where dysregulation is most problematic. These findings indicate that metformin warrants further investigation as a therapeutic adjunct for managing naturally occurring IR, though practitioners should note that this was an experimental study in a small population, and clinical efficacy in field conditions remains to be established through prospective trials.
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Practical Takeaways
- •Metformin may be a useful therapeutic option for horses with insulin resistance by reducing post-meal blood glucose and insulin spikes, potentially reducing laminitis risk
- •A single oral dose of metformin (30 mg/kg) administered 1 hour before feeding appears sufficient to dampen glycaemic responses in both healthy and insulin-resistant horses
- •Further clinical trials in naturally occurring insulin-resistant horses are needed before making definitive feeding or treatment recommendations, but results are promising for metabolic disease management
Key Findings
- •Metformin administration reduced peak glucose concentration in healthy horses (P = 0.002) and in dexamethasone-induced insulin-resistant horses (P < 0.001)
- •Metformin significantly reduced area under the glucose curve in both healthy horses (P < 0.001) and insulin-resistant horses (P < 0.001)
- •Insulin concentration at 120 minutes post-dextrose was significantly lower with metformin in healthy horses (P = 0.011) and at 120 and 150 minutes in insulin-resistant horses (P = 0.034 and P = 0.014 respectively)
- •Metformin showed efficacy in reducing glycaemic and insulinaemic responses at both baseline and in experimentally induced insulin resistance states