Infant Formula Based on Milk Fat Affects Immune Development in Both Normal Birthweight and Fetal Growth Restricted Neonatal Piglets

Abstract

Infant formulas offer an alternative to breast milk for both normal birth weight (NBW) and immunocompromised intrauterine growth restricted (IUGR) infants. Although the lipid fraction in formulas is often derived from vegetable oils, it is unclear if this alters immunological outcomes relative to milk fats or whether these effects differ between IUGR and NBW infants. We hypothesized that replacing vegetable oil with bovine milk fat in infant formula would improve immune development in IUGR and NBW neonates. Two-day old piglets were selected (NBW, n = 18, IUGR, n = 18) and each group of animals were fed formula based on either vegetable oil (VEG) or bovine milk fat (MILK). Animals were reared until day 23/24 and systemic immune parameters were evaluated. Milk-fat feeding decreased blood neutrophil counts and improved neutrophil function while transiently reducing leucocytes' expression of genes related to adaptive and innate immunity as well as energy metabolism, following in vitro stimulation by live Staphylococcus epidermidis (whole blood, 2 h). However, there were only a few interactions between milk-fat type and birthweight status. Thus, piglets fed milk-fat-based formula had improved neutrophil maturation and suppressed pro-inflammatory responses, compared to those fed vegetable-oil-based formula.

Keywords: immune development; infant; infant formula; intrauterine growth restriction; milk fat; neonate.

Figure 1

Development of neutrophil counts and function in animals fed either vegetable (VEG, n = 11–18) or milk fat (MILK, n = 11–18) further stratified into normal birthweight (NBW, n = 12–18) or intrauterine growth restricted (IUGR, n = 10–18) animals. (A) Neutrophil counts, (B) Neutrophil phagocytic rate, (C) Neutrophil phagocytic capacity, (D) Neutrophil phagocytic rate of farm raised 19-day-old piglets where plasma has been substituted with pooled plasma samples from either vegetable (VEG-PLASMA, n = 7) or milk-fed animals (MILK-PLASMA, n = 7). (E) Neutrophil phagocytic function in either VEG-PLASMA or MILK-PLASMA. All results presented as means with corresponding standard errors. *: p < 0.05, (*): p < 0.1.

Figure 2

Development of monocyte counts and gene expression of innate immune markers in animals fed either vegetable (VEG, n = 6–18) or milk fat (MILK, n = 7–18) further stratified into normal birthweight (NBW, n = 7–18) or intrauterine growth restricted (IUGR, n = 6–18) animals. (A) Monocyte counts; (B–D) Expression of CXCL10, TLR2, and TLR4 in whole blood stimulated with Staphylococcus epidermidis, shown as relative gene expression; (E) Level of CRP in plasma on day 23/24. (A,E) are presented as means with corresponding standard error, (B–D) are presented as range plots with corresponding medians. **: p < 0.01, *: p < 0.05, (*): p < 0.1.

Figure 3

Development of lymphocyte and T cell counts and gene expression of adaptive immune markers in animals fed either vegetable (VEG, n = 6–18) or milk fat (MILK, n = 7–18) further stratified into normal birthweight (NBW, n = 7–18) or intrauterine growth restricted (IUGR, n = 6–18) animals. (A) Lymphocyte counts; (B,C) Fraction of regulatory and helper T cells; (D–G,I) Expression of IL2, IL17, GATA3, TNFA, and TGFB1 in whole blood stimulated with Staphylococcus epidermidis, shown as relative gene expression; (H) Levels of tumor necrosis factor α in samples following stimulation with SE. (A–C,H) are presented as means with corresponding standard error. (D–G,I) are presented as range plots with corresponding medians. *: Effect of diet, ***: p < 0.001, **: p < 0.01, *: p < 0.05, (*): p < 0.1. Main effects of birthweight across diet groups are shown in the figures as P_IUGR.

Figure 4

Expression of genes related to cellular metabolism in animals fed either vegetable (VEG, n = 6–8) or milk fat (MILK, n = 7–9) further stratified into normal birthweight (NBW, n = 7–8) or intrauterine growth restricted (IUGR, n = 6–9) animals. (A–C) Expression of PPARG, PDHA1 and PKM in whole blood stimulated with Staphylococcus epidermidis, shown as relative gene expression. All results presented as range plots with corresponding medians. *: Effect of diet, ***: p < 0.001, **: p < 0.01, *: p < 0.05. Main effects of birthweight across diet groups are shown in the figures as P_IUGR.