Oral insulin-like growth factor-i (igf-i) does not alter organ growth or tissue igf binding protein (igfbp) expression in the neonate piglet

IGF-I contributes to the growth promoting actions of colostrum and milk, however, artificially fed infants or piglets receive diets which are devoid of IGF-I since it is either removed or destroyed during formula processing. Our goal was to determine whether oral IGF-I affects the molecular ontogeny of the IGF/IGFBP axis in the neonate. Cesarianderived piglets were fed sow milk replacer ±500 ng/L IGF-I. Blood and tissue samples were collected from the treatment groups and from sowreared piglets on d 7 and 14 postpartum. Serum IGF-I, IGF-II and IGFBP profiles were determined. Total cellular RNA was isolated from liver, muscle and kidney and IGFBP rnRNA expression was assessed by Northern blotting. No significant differences between the treatment groups were noted for body weight, organ weights (g/kg BW), serum IGF-I, IGFII, or IGFBP. Liver and kidney IGFBP-4 expression and hepatic IGFBP-1 expression did not differ between the treatment groups at either time point, indicating that oral IGF-I alone does not alter the expression of IGFBP within tissues. However, liver IGFBP-I was lower in sow-reared piglets than artificially fed piglets on d 7, suggesting that differences may occur between suckling and formula fed piglets. In addition, a decrease in hepatic IGFBP-1 mRNA between d 7 and 14 was observed within each of the formula-fed groups, which is consistent with normal ontogenic changes in IGFBP-1 expression. Our data suggest that oral IGF-I does not exert systemic growth effects or alter the normal molecular ontogeny of IGFBP expression in the neonatal piglet. (Supported by NIH grant HD-292M).