Comparison of insulin sensitivity between healthy neonatal foals and horses using minimal model analysis.
Authors: Kinsella Hannah M, Hostnik Laura D, Snyder Hailey A, Mazur Sarah E, Kamr Ahmed M, Burns Teresa A, Mossbarger John C, Toribio Ramiro E
Journal: PloS one
Summary
# Editorial Summary Contrary to prevailing assumptions about glucose intolerance in newborn foals, recent research demonstrates that healthy neonates exhibit significantly greater insulin sensitivity than adult horses during the first 24–60 hours of life. Using the insulin-modified frequently sampled intravenous glucose tolerance test (I-FSIGTT) and minimal model analysis on 12 foals and 8 adult horses, investigators found that foals' insulin sensitivity values were approximately 20 times higher (median 18.3 L·min⁻¹·μIU⁻¹) compared to horses (0.9 L·min⁻¹·μIU⁻¹), with disposition index values similarly elevated in foals, suggesting superior pancreatic β-cell responsiveness relative to insulin action. Glucose effectiveness and acute insulin response to glucose showed no differences between groups, whilst fasting proxy measurements (modified insulin-to-glucose ratio and HOMA-BC%) indicated that foals mounted lower basal insulin secretion than adult horses, potentially reflecting efficient glucose handling rather than endocrine immaturity. These findings suggest neonatal insulin sensitivity may represent an evolutionary advantage for energy conservation during transition to extrauterine life, fundamentally challenging the clinical assumption of impaired glucose tolerance in newborn foals and warranting reconsideration of how we assess metabolic function and nutritional management in the immediate neonatal period.
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Practical Takeaways
- •Healthy newborn foals are insulin sensitive immediately after birth, contrary to traditional assumptions—monitor glucose/insulin carefully as foals age and sensitivity decreases, particularly during transition periods
- •The dramatic shift in insulin sensitivity between neonates and adult horses suggests metabolic maturation occurs over time; baseline expectations for glucose tolerance testing must account for age
- •Evolutionary conservation of energy in early neonatal life may explain the neonatal insulin sensitivity phenotype; this has implications for nutritional and metabolic management protocols in foals less than 60 hours old
Key Findings
- •Neonatal foals demonstrated significantly higher insulin sensitivity (SI: 18.3 vs 0.9 L·min⁻¹·μIU⁻¹; p<0.0001) compared to adult horses
- •Disposition index was 20-fold higher in foals (12×10³ vs 4×10²; p<0.0001), indicating superior beta cell function relative to insulin sensitivity
- •Modified insulin-to-glucose ratio was lower in foals (1.72 vs 3.91; p=0.009), suggesting improved glucose utilization efficiency
- •Acute insulin response to glucose and glucose effectiveness were not significantly different between age groups, suggesting intact pancreatic beta cell responsiveness in neonates