Effects of dexamethasone on glucose dynamics and insulin sensitivity in healthy horses.

The research article studied the effects of administering the steroid dexamethasone on glucose levels and insulin sensitivity in healthy horses, observing that it resulted in insulin resistance which could increase the risk of laminitis, a painful and serious disease in horses.

Objective of the Research

The research aimed at understanding the impact of dexamethasone, a type of steroid, on the glucose levels and insulin sensitivity in healthy horses. Six standard adult horses were involved in the study. The study was driven by the assumption that dexamethasone would impact the insulin levels in horses, leading to insulin resistance.

Methodology

• The researchers used a balanced crossover study wherein the horses were either administered dexamethasone or a saline solution (which acted as the control) over a period of 21 days.
• The dexamethasone dosage was 0.08 mg/kg (administered intravenously every 48 hours). A glucose tolerance test (FSIGT) was conducted 2 days after the treatment.
• The data of glucose and insulin from these tests were used to calculate insulin sensitivity (Si), glucose effectiveness (Sg), acute insulin response to glucose (AIRg), and disposition index.
• Proxies for insulin sensitivity (RISQI) and beta-cell responsiveness (MIRG) were also calculated using basal plasma glucose and serum insulin concentrations.

Results

• The results showed that the mean insulin concentration was higher in horses treated with dexamethasone than in control horses on days 7, 14, and 21.
• There was a significant rise in the plasma glucose concentration in dexamethasone-treated horses on days 7, 14, and 21. However, the difference was significant only on day 14.
• The data analysis from FSIGT showed a decrease in insulin sensitivity and an increase in AIRg after dexamethasone treatment.
• There was no noticeable change in glucose effectiveness or disposition index after the treatment.
• The mean RISQI was significantly lower while the MIRG was higher in dexamethasone-treated horses than control horses on days 7, 14, and 21.

Conclusions

The study concluded that the administration of dexamethasone over a period of 21 days resulted in a marked insulin resistance in healthy horses. This is concerning because insulin resistance has been associated with a predisposition to laminitis – a serious and painful hoof disease in horses. As such, the use of dexamethasone could potentially increase the risk of laminitis in horses and ponies.