Impact of lipid composition of infant formulas on protein digestion, gut immunology and microbiota in neonatal piglets

Incorporation of milk fat and milk fat globule membrane fragments in infant formulas could be an interesting way to get closer to the composition and structure of human milk and its physiological impacts.Two adapted formulas were processed containing either vegetable fat (STD) or a combination of milk and vegetable fats stabilized by a mixture of proteins and milk fat globule membrane fragments (EXP). The formulas were distributed with an automatic milk feeder to piglets until slaughter at 28 days. Intestinal contents and tissues (proximal jejunum and ileum) as well as mesenteric lymph nodes (MLN) were collected. The residual immunoreactivity of β-lactoglobulin (β-lg) and caseins (Cns) present in the digestive compartments was determined by ELISA. Mononuclear cells isolated from MLN were cultured in vitro to evaluate their cytokine secretory profiles. Microbiota diversity and composition was assessed using DHPLC and metasequencing analysis. Finally the immunomodulatory capacity of peptide and lipid fractions extracted from the jejunal contents of STD and EXP piglets were tested in vitro on MLN cells from sow’s suckling piglets. The immunoreactivity of β-lg and Cns was higher in EXP than in STD intestinal contents. The secretory activity of MLN cells was modified by the formula composition, the highest IFNγ secretion was obtained in EXP piglets. A major immunosuppressor effect of lipid fractions was evidenced with both formulas. Microbiota clustering successfully discriminated infant formulas according to the presence of exclusive vegetable vs. a combination of milk and vegetable lipids. Differences in proteobacteria and firmicutes phyla were observed. In conclusion we evidenced that lipid composition of formulas had influence on gut physiology through the release of immunomodulatory lipids in contact with the mucosa, modulation of the dynamic of proteolysis and microbiota composition.