Effects of diet-induced weight gain on insulin sensitivity and plasma hormone and lipid concentrations in horses.

This study examines the impact of diet-induced weight gain on insulin sensitivity, and plasma hormone and lipid levels in horses, revealing that weight gain leads to decreased insulin sensitivity and increased insulin and leptin concentrations. However, there were no observed changes in lipid concentrations.

Methodology

• The researchers selected 13 adult gelding horses for the study.
• The horses were fed 200% of their digestible energy requirements for maintenance over a 16-week period to induce weight gain.
• To evaluate glucose and insulin dynamics, frequently sampled Intravenous (IV) Glucose Tolerance Tests were performed before and after the weight gain.
• The team measured the horses’ adiposity (fatness) through condition scoring, morphometric measurements, and assessment of subcutaneous fat depth.
• They also measured plasma concentrations of insulin, glucose, nonesterified fatty acids, triglycerides, and leptin on a weekly or biweekly basis.

Results

• The average body weight of the horses increased by 20% over the study period.
• The body condition score, indicating fatness, increased significantly suggesting the horses put on weight.
• The measurements revealed that plasma glucose, triglyceride, and nonesterified fatty acid concentrations remained similar before and after weight gain.
• However, the concentrations of leptin and insulin increased with weight gain suggesting a correlation.
• Insulin sensitivity decreased substantially (by 71%), but a 408% increase in acute insulin response to glucose made up for it, resulting in a similar disposition index.

Conclusions

• The results suggest that diet-induced weight gain in horses is associated with decreased insulin sensitivity.
• This reduced insulin sensitivity was effectively compensated by an increased insulin secretory response. This could be seen as the body’s way of balancing the reduced sensitivity.
• The weight gain also resulted in increased insulin and leptin concentrations compared to baseline values. This indicates a condition called hyperinsulinemia (high levels of insulin in the blood) and hyperleptinemia (excessively high levels of leptin).
• Contrary to expectation, there were no changes in lipid concentrations apparent from the weight gain.
• The researchers concluded that preventing obesity could be a strategy to avoid insulin resistance, hyperinsulinemia, and hyperleptinemia in horses.