Ghrelin and cholecystokinin in term and preterm human breast milk

Aim: To determine whether ghrelin and cholecystokinin (CCK) are present in significant quantities in term and preterm human breast milk, and to identify their source. Methods: Samples were collected from 10 mothers who delivered term infants and 10 mothers who delivered preterm infants. Estimated fat content was measured. Ghrelin and CCK levels were measured in whole and skim breast milk samples using radioimmunoassays (RIA). Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed using RNA from human mammary epithelial cells (hMECs) and mammary gland with primers specific to ghrelin. Results: The median ghrelin level in whole breast milk was 2125 pg/ml, which is significantly higher than normal plasma levels. There was a direct correlation between whole milk ghrelin levels and estimated milk fat content (r = 0.84, p < 0.001). Both the mammary gland and hMECs produced ghrelin. While CCK was detected in some samples, levels were insignificant. Infant gestational age, birthweight, maternal age, and maternal pre-pregnancy body mass index did not significantly affect the results. Conclusion: Ghrelin, but not CCK, is present in breast milk. Since the mammary gland produces ghrelin message, and ghrelin levels in breast milk are higher than those found in plasma, we conclude that ghrelin is produced and secreted by the breast.