Appetite-Regulating Hormones In Human Milk: A Plausible Biological Factor For Obesity Risk Reduction?

Background Human milk contains appetite-regulating hormones that may influence infant growth and obesity risk. Research aims We evaluated whether leptin, peptide tyrosine-tyrosine (PYY), glucagon-like peptide-1 (GLP-1), and ghrelin concentrations in human milk (1) changed during feeding (from foremilk to hindmilk) and during the first 6 months of infancy; (2) were explained by maternal factors; and (3) were associated with infant anthropometrics and growth. Methods Mother-infant dyads (N= 22) participated. Samples of foremilk and hindmilk at 1 month postpartum were collected and analyzed for leptin, PYY, GLP-1, and ghrelin via radioimmunoassay and milkfat percentage estimated via creamatocrit. Samples were also collected in mothers (n= 15) who breastfed through 6 months. Anthropometrics were obtained on all mother-infant dyads at 1 month and all infants at 6 months and 12 months. Results At 1 month, milk GLP-1 and milkfat concentration increased from foremilk to hindmilk (p <= .05) while leptin and PYY concentrations remained stable during feeding. Milk hormone concentrations and milkfat tended to decline overtime, with lower leptin, PYY, and ghrelin at 6 months versus 1 month (p< .05). At 1 month, milk leptin and milkfat content were associated with maternal markers of adiposity (r= 0.49-0.78,p< .001); whereas, milk PYY was correlated with maternal serum PYY concentration (r= 0.672,p= .001). Average 1-month milk concentrations of GLP-1 and leptin were negatively associated with weight-for-agez-scores at 6 months (r= -0.46,p< .05) and 12 months (r= -0.49,p< .05), respectively. Conclusion The content of certain appetite-regulating hormones in human milk may be influenced by maternal factors and play a role in infant growth; much needs to be learned about their role in the obesity protection of breastfed infants.