Location: Arkansas Children's Nutrition CenterTitle: Effects of Dietary Protein Source on Neonatal Metabolism and Body Composition Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/7/2011
Publication Date: 5/25/2011
Citation: Ronis, M.J. 2011. Effects of Dietary Protein Source on Neonatal Metabolism and Body Composition. [abstract]. In: Proceedings of the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition. Symposium on The roll of soy protein in promoting growth and development in infants and young children, May 25-28, 2011, Sorrento, Italy. p. 58. Interpretive Summary: Although there are enormous differences in nutrient composition between breast milk and infant formulas, little work has examined the metabolic and physiological consequences of this on body composition or metabolism in breast-fed versus formula fed infants. Even less is known regarding differences between different infant formulas such as cow’s milk-based formulas and those made using soy protein. Preliminary data from a large longitudinal study of breast and formula-fed infants (The Beginnings Study at the ACNC) demonstrated that, as suggested by others, breast-fed infants have lower body weight gain during the first year of life and that soy-formula fed infants had a lower % fat mass than breast-fed infants during the neonatal period. In studies comparing breast and formula feeding using a neonatal piglet model we have shown increased bone mineral density in soy formula-fed pigs on postnatal day 21 associated with increased signaling through a molecular pathway involving bone morphogenic proteins (BMPs) in bone. In addition, we have observed increased iron storage and reduced serum cholesterol in formula-fed compared to breast-fed pigs. Effects on iron storage appear to be related to low iron content in breast milk compared to formulas which are iron supplemented and were accompanied by effects on expression of hepcidin and the transferrin receptor, genes known to regulate iron storage in the liver. Array analysis of gene expression patterns in the liver demonstrated additional effects of formula feeding on genes involved in cholesterol synthesis and degradation to bile acids. In particular formula feeding, especially soy-formula, increased expression of the liver enzyme CYP7A1, the rate limiting enzyme in bile acid synthesis. These data are consistent with clinical reports of increased bile acid excretion in formula-fed infants and the reported cholesterol lowering effects of soy feeding. In contrast, analysis of known hepatic estrogen-inducible genes suggested no estrogenic signature associated with soy-formula-feeding.
Technical Abstract: Although it is well established that breast-fed infants in general have lower body weight gain during the first year of life than infants fed formulas, little research has examined effects of different types of infant formula on metabolism and body composition in neonates. Preliminary data from a longitudinal study (The Beginnings Study) comparing breast-fed, dairy formula-fed and soy formula-fed infants at the ACNC has observed lower % fat mass compared with breast-fed infants during the neonatal period. Studies in a neonatal piglet model comparing breast-, dairy and soy-formula feeding have demonstrated increased bone mineral density in soy formula-fed piglets compared to breast-fed piglets associated with increased signaling through bone morphogenic protein (BMP)-signaling pathways. In addition, formula feeding in piglets was associated with increased hepatic iron storage and reduced serum total cholesterol concentrations at weaning compared to breast-feeding (P<0.05). Array analysis of hepatic gene expression signature was consistent with these physiological and biochemical consequences of formula feeding. Increased expression of hepcidin and reductions in expression of transferrin receptor mRNAs (P<0.05) reflected differences in iron content of breast-milk and formulas. In addition, formula feeding, in particular soy-formula, increased expression of hepatic CYP7A1, the rate limiting enzyme in bile acid synthesis. These data are consistent with clinical reports of increased bile acid excretion in formula-fed infants and the reported hypocholesterolemic effects of soy feeding. In contrast, analysis of known hepatic estrogen-inducible genes suggested no estrogenic signature associated with soy-formula-feeding.