Formula feeding alters hepatic gene expression signature, iron and cholesterol homeostasis in the neonatal pig.

In the U.S. formula feeding remains more popular than breast-feeding. In the current study, neonatal piglets were breast fed and compared with those fed commercially available milk-based formula (milk) or soy-based formula (soy) from postnatal day 2 (PND2) until death at PND21 (the usual age of weaning). Liver weights were greater in formula-fed piglets (P<0.05) than in breast-fed piglets (P<0.05). Affymetrix array analysis revealed significant differences in hepatic gene expression signatures between piglets fed breast milk or formula, as well as between piglets fed milk or soy. In males, expression of 346 hepatic genes differed between formula-fed and breast-fed piglets, and soy-fed differed from milk-fed piglets in 277 genes. Furthermore, gene expression profiles of males differed from females, even when the same diet was consumed. Serum cholesterol was lower in piglets fed formula relative to breast-fed piglets (P<0.05), and this was associated with elevations in mRNA encoding cholesterol 7α-hydroxylase (CYP7A1). Consistent with the human literature, breast-fed piglets had lower hepatic iron accumulation than formula-fed piglets. Hepcidin, a major regulator of hepatic iron trafficking, was elevated in piglets fed formula relative to breast-fed piglets (P<0.05). Female piglets fed soy formula had increased expression of CYP3A enzymes (P<0.05), and soy formula feeding decreased expression of several hepatic genes considered estrogen inducible. These data suggest that: 1) gene expression profiles in neonates differ significantly depending on the diet consumed, 2) hepatic iron storage and cholesterol metabolism clearly differ between breast and formula feeding in piglets, 3) there is no evidence that soy is estrogenic in neonatal pig liver.