Peptidomics Analysis of Milk Protein-Derived Peptides Released over Time in the Preterm Infant Stomach

Over the course of milk digestion,
native milk proteases and infant digestive proteases fragment intact
proteins into peptides with potential bioactivity. This study investigated
the release of peptides over 3 h of gastric digestion in 14 preterm
infant sample sets. The peptide content was extracted and analyzed
from milk and gastric samples via Orbitrap tandem mass spectrometry.
The relative ion intensity (abundance) and count of peptides in each
sample were compared over time and between infants fed milk fortified
with bovine milk fortifier and infants fed unfortified milk. Bioactivity
of the identified peptides was predicted by sequence homology to known
bioactive milk peptides. Both total and bioactive peptide abundance
and count continuously increased over 3 h of gastric digestion. After
accounting for infant weight, length, and postconceptual age, fortification
of milk limited the release of peptides from human milk proteins.
Peptides that survived further gastric digestion after their initial
release were structurally more similar to bioactive peptides than
nonsurviving peptides. This work is the first to provide a comprehensive
profile of milk peptides released during gastric digestion over time,
which is an essential step in determining which peptides are most
likely to be biologically relevant in the infant. Data are available
via ProteomeXchange with identifier PXD012192.