Effects of maternal dexamethasone treatment on pancreatic β cell function in the pregnant mare and post natal foal.

This research explored the metabolic effects of dexamethasone, a synthetic glucocorticoid, on pregnant horses and their foals post-birth, uncovering potential impacts on insulin-glucose dynamics in the mother and pancreatic cell function in the offspring.

Objective of the Study

• The main purpose of this study was to investigate how the administration of dexamethasone—a synthetic glucocorticoid commonly used to treat inflammatory breeds in horses—affects the metabolism in pregnant horses and their offspring post-birth. This inquiry was motivated by the understanding that glucocorticoids are used in pregnant animals to stimulate fetal maturation, which can have long-lasting metabolic effects on the offspring if given prematurely.

Methods Used

• In the experiment, six pony mares were given three doses of dexamethasone at 48-hour intervals when they were approximately 270 days pregnant. Five control mares were given saline injections using the same protocol.
• After fasting overnight, the mares’ pancreatic β cell responses to external glucose were checked before, during, and after the treatment. Post-birth, pancreatic β cell responses to exogenous glucose and arginine in the foals were measured at 2 and 12 weeks.

Findings of the Study

• The study found that a notable increase in basal insulin concentrations and the insulin responses to external glucose were observed in mares that were treated with dexamethasone. These variances were still significant 72 hours following the treatment.
• The dexamethasone treatment resulted in a significant decrease in the placental area, but did not noticeably affect the biometry of the foal at birth or afterward.
• The study also found that while the foal’s pancreatic β cell function was not affected at two weeks by the maternal treatment, a decrease in cell sensitivity to arginine (but not glucose) was noticed by twelve weeks in foals whose mothers were treated with dexamethasone, continuing post-birth.

Conclusions of the Study

• The study concluded that the dexamethasone treatment induced changes in maternal insulin-glucose dynamics, suggesting an insulin resistance, and had subtle long-term effects on postnatal pancreatic β cell function in foals. The findings suggested that the programming effects of dexamethasone in horses might be partially caused by changes in maternal metabolism and placental growth.