A Pilot Study Exploring the Relationship Between Milk Composition and Microbial Capacity in Breastfed Infants.

Abstract

Background: Maternal obesity may contribute to childhood obesity in a myriad of ways, including through alterations of the infant gut microbiome. For example, maternal obesity may contribute both directly by introducing a dysbiotic microbiome to the infant and indirectly through the altered composition of human milk that fuels the infant gut microbiome. In particular, indigestible human milk oligosaccharides (HMOs) are known to shape the composition of the infant gut microbiome. The goal of this study was to characterize the HMO profiles of normal-weight and overweight mothers and to quantitatively link HMO concentrations to the taxonomic composition and functional potential of the infant gut microbiome.

Methods: Normal-weight (BMI = 18.5-24.9; n = 9) and overweight/obese (OW/OB; BMI > 25; n = 11) breastfeeding mothers and their infants were enrolled in this single-center, cross-sectional pilot study. Human milk from the mothers and rectal stool swabs from the infants were collected 7-9 weeks postpartum. The HMO composition, microbiome composition, and microbial functions were assessed using HPLC, 16S rRNA gene sequencing, and metagenomic sequencing, respectively.

Results: Neither the HMO profiles nor the infant microbiome composition varied according to maternal BMI status. Taxonomically, the gut microbiota of infants were dominated by typical gut lineages including Bifidobacterium. Significant correlations between individual HMOs and bacterial genera were identified, including for Prevotella, a genus of the Bacteroidota phylum that was positively correlated with the concentrations of lacto-N-neotetraose (LNnT) and lacto-N-hexaose (LNH). Using metagenomic assembled genomes, we were also able to identify the broad HMO-degradative capacity across the Bifidobacterium and Prevotella genera.

Conclusions: These results suggest that the maternal BMI status does not impact the HMO profiles of human milk. However, select HMOs were correlated with specific bacterial taxa, suggesting that the milk composition influences both the taxonomic composition and the functional capacity of the infant gut microbiome.