Comparative Proteomics of Human and Macaque Milk Reveals Species-Specific Nutrition during Postnatal Development

Milk has been well established as
the optimal nutrition source
for infants, yet there is still much to be understood about its molecular
composition. Therefore, our objective was to develop and compare comprehensive
milk proteomes for human and rhesus macaques to highlight differences
in neonatal nutrition. We developed a milk proteomics technique that
overcomes previous technical barriers including pervasive post-translational
modifications and limited sample volume. We identified 1606 and 518
proteins in human and macaque milk, respectively. During analysis
of detected protein orthologs, we identified 88 differentially abundant
proteins. Of these, 93% exhibited increased abundance in human milk
relative to macaque and include lactoferrin, polymeric immunoglobulin
receptor, alpha-1 antichymotrypsin, vitamin D-binding protein, and
haptocorrin. Furthermore, proteins more abundant in human milk compared
with macaque are associated with development of the gastrointestinal
tract, the immune system, and the brain. Overall, our novel proteomics
method reveals the first comprehensive macaque milk proteome and 524
newly identified human milk proteins. The differentially abundant
proteins observed are consistent with the perspective that human infants,
compared with nonhuman primates, are born at a slightly earlier stage
of somatic development and require additional support through higher
quantities of specific proteins to nurture human infant maturation.