Small intestinal disaccharidase activities are upregulated, whereas peptidase activity is decreased by orally administered insulin-like growth factor-i in the neonatal piglet

We have shown that piglets fed formula containing 500 μg/L of IGF-I had 2- to 4-fold higher small intestinal lactase and sucrase specific activities (SA) than piglets fed formula alone, suggesting that milk-borne IGF-I plays a role in intestinal maturation. The goal herein was to further elucidate the regulation of the intestinal disaccharidases and leucine aminopeptidase (LAP) in response to oral IGF-I ranging from physiological to pharmacological doses. Cesarian-derived piglets (n=34) were fed formula containing 0, 100, 250, 500 or 1000 ng/L of IGF-I for 14 days. Daily body weight and formula intakes were recorded. At termination, serum was collected and organs were weighed. Small intestines were flushed with saline and samples were taken at 13 sites along its entire length. Body and organ weights, intestinal weight and length, and serum IGF-I. IGF-II or IGF binding protein profiles were comparable among the groups. However, jejunal sucrase SA was 3-fold higher in the 1000 μg/L group vs. control. Lactase was more responsive than sucrase to oral IGF-I, resulting in 1.5- to 3-fold higher lactase SA throughout the small intestine at all doses of IGF-I. In contrast, ileal leucine aminopeptidase SA was reduced in a dose-dependent manner in IGF-I treated piglets compared to control. In conclusion, oral IGF-I modulates small intestinal digestive enzymes; however, the differential responses of the disaccharidases vs. LAP suggest that IGF-I may selectively regulate the expression of digestive enzymes during neonatal development.