Metabolomics reveals changes in levels of fecal branched chain amino acids and organic acids in very preterm infants fed human milk fortified with bovine colostrum

Background & aims: Human milk is the optimal diet for very preterm infants (VPIs), but it requires nutrient fortification to support growth. Bovine colostrum (BC), rich in intact proteins and bioactive components, could serve as a novel fortifier with potential benefits to VPIs gut health. To evaluate a possible effect of feeding BC on intestinal metabolism, the gut microbiota, and their interaction, we studied the fecal metabolome of VPIs in the first month of life, as compared with a conventional fortifier (CF, based on infant formula ingredients). Methods: Fecal samples were collected from VPIs recruited to the FortiColos trial (NCT03537365, BC, n = 107; CF, n = 112) before (FT0) and one (FT1) or two (FT2) weeks after start of fortification and analyzed using ¹H NMR spectroscopy. Abundances of metabolites were compared between BC versus CF groups. Further, temporal changes in metabolite levels after start of fortification, as well as correlations with specific gut bacterial genera were explored. Results: Infants in the BC group had higher levels of fecal acetoacetate, choline, methanol, uracil, creatine, creatinine, lysine and a lower leucine at both FT1 and FT2, relative to the CF group. Asparagine, tryptophan and phenylalanine levels were higher, and butyrate was lower in the BC group at FT1. At FT2, higher fecal succinate and lower isoleucine were found in the BC group. In addition, eight metabolites (asparagine, phenylalanine, tryptophan, lysine, creatinine, acetoacetate, methanol and uracil) had fortification-specific changes over time. Positive correlations were found between succinate and unclassified Enterobacteriaceae, butyrate and Clostridium, uracil and Staphylococcus, while negative correlation were found between uracil and unclassified Enterobacteriaceae members. Conclusion: Our study shows distinct fecal metabolome profiles in VPIs in the first weeks after fortification with BC versus CF. The fortification- and time-specific gut metabolite changes suggest that fortifiers influence luminal nutrient metabolism and microbiota activity in VPIs. Fortifier type for human milk affected gut health of VPIs via altered gut metabolite levels, interacting with microbiota in VPIs.