Is milk-borne insulin-like growth factor-I essential for neonatal development?
Insulin-like growth factor-I (IGF-I), a polypeptide growth factor found in milk, is hypothesized to play a functional role in the growth and development of neonates, particularly the gastrointestinal tract. Considerable evidence, based on direct tracer studies with 125I-labeled IGF-I and measurements of circulating IGF-I concentrations in neonatal animals fed a range of IGF-I doses, indicates that the intestinal absorption of IGF-I and the possible effect on metabolism and somatic growth are negligible. However, studies in neonatal animals indicate that oral administration of pharmacological doses of IGF-I increases small intestinal mucosal growth, whereas oral IGF-I provided within the physiological range may enhance the development of intestinal lactase. Therefore, clinical trials exploring the therapeutic use of oral IGF-I as an intervention for preterm neonates and those with compromised intestinal function seem warranted. However, milk-borne IGF-I may not be essential for normal healthy infants, perhaps because endogenous IGF-I provides a sufficient stimulus for maintenance of gastrointestinal structure and function. Future studies should explore the significance of endogenous IGF-I and whether milk-borne IGF-I may be important under pathological conditions in which the endogenous IGF-I production may be compromised.
Burrin
D G
DG
Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D004064:Digestive System / Q000254:growth & development; D006801:Humans; D007231:Infant, Newborn / Q000254:growth & development*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology*; D007408:Intestinal Absorption; D008895:Milk, Human / Q000737:chemistry*
D007334:Insulin-Like Growth Factor I