Glucose utilization in the horse.

This study investigates the effects of fasting on glucose management in Shetland ponies. The results show a reduction in glucose entry and irreversible loss rates following fasting, but no significant change in recycling rate or ketones concentration in plasma.

Research Purpose and Procedure

• The objective of the research was to study the changes in glucose regulation, including total entry, irreversible loss, and recycling rates, in non-pregnant female Shetland ponies before and after a 24-hour fast. This was done using continuous intravenous infusion of a mixture of specific glucose isotopes.
• The authors measured rates of glucose movement within four ponies’ bodies, first when they were in a fed state, and then repeated the measures after the ponies had fasted for 24 hours.

Key Findings

• The results indicated that after fasting, both the total entry rate and the irreversible loss rate of glucose in the ponies decreased. However, the recycling rate of glucose did not show any significant change.
• Despite the decrease in blood glucose levels after fasting, the rise in the concentration of ketones – substances produced when the body breaks down fat for energy – was not significant. This suggests that fasting did not lead to a significant shift in metabolic energy sources in these animals.
• Administration of glucose had varied effects on endogenous glucose production. While in one pony it had no significant impact, in another pony it decreased the total entry and irreversible loss by 43% and 54% respectively. This implies individual variation in glucose regulation in response to dietary changes.

Implication and Conclusion

• The study concludes that fasting leads to altered glucose regulation in Shetland ponies, marked by reduced glucose entry and usage.
• However, the fasting state does not significantly affect glucose recycling or the production of ketones, suggesting stable management of glucose and energy metabolism during short-term deprivation of feed.
• The irreversible loss of glucose in horses is similar to that in many other species, indicating shared physiological mechanisms for glucose regulation across different animals.