Human milk metals and metalloids shape infant microbiota

Area of Science:

• Human milk metallomics
• Infant gut microbiota development
• Maternal-infant health

Background:

• Metal(loid)s in human milk are vital for infant growth but their effect on the infant gut microbiota is not well understood.
• Essential elements like manganese, zinc, iron, and copper play critical roles in infant health.
• Investigating the link between human milk metal(loid) composition and the early-life infant gut microbiome is crucial.

Purpose of the Study:

• To determine the metal(loid) content in human milk.
• To assess the influence of these metal(loid)s on the infant gut microbiota composition within the first two months postpartum.
• To explore correlations between specific metal(loid)s and bacterial genera in the infant gut.

Main Methods:

• Collected human milk and infant stool samples from 77 mother-infant dyads at early transitional and mature lactation stages.
• Performed metallomic profiling of human milk using inductively coupled plasma-mass spectrometry (ICP-MS).
• Analyzed infant gut microbiota via 16S rRNA amplicon sequencing and used Spearman's rank correlation to identify metal(loid)-microbiota relationships.

Main Results:

• Observed significant variations in metal concentrations and microbial abundances/diversities between lactation stages.
• Found correlations between specific metals and gut bacteria, including positive correlation of infant gut Corynebacterium with milk nickel, and negative correlations of Veillonella with antimony and Enterobacter with copper during early lactation.
• Identified multiple significant correlations in mature lactation, with Klebsiella genus negatively correlated with iron, antimony, and vanadium; Simpson's diversity was negatively correlated with iron.

Conclusions:

• Highlights significant metal(loid)-microbiota interactions influencing early infant development.
• Suggests the infant gut Klebsiella genus is particularly sensitive to variations in human milk metal(loid) levels.
• Recommends future strain-level research to understand implications for infant health and development.