RESUMEN
Background Lactoferrin (LF) is a highly represented, functional glycoprotein in human milk, exerting a wide range of anti-infective, immunomodulatory, and prebiotic actions in the neonate. Limited data are available assessing the concentrations and levels of LF in maternal milk over time during lactation in mothers who delivered infants at different GAs. Our aim with the present study was to determine the levels of LF in human milk from mothers of preterm and term infants and to evaluate the variations at a different time from delivery, in colostrum and mature milk. Methods Mothers of preterm and term infants from the Neonatology Unit in Foggia, Italy, were approached and enrolled in this study. From each mother, milk samples were collected within the first 3 days after birth (group A, 0-72 hours), between the 5th and 7th day after delivery (group B, 120-168 hours), and after the 10th day (group C, > 240 hours). All milk samples were divided into five groups, according to the GA of the infants: 24 to 27.6 weeks of GA (I), 28 to 31.6 weeks of GA (II), 32 to 34.6 weeks of GA (III), 35 to 37.6 weeks of GA (IV), and > 38 weeks of GA (V). Milk samples were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to determine the content of LF. Results A total of 84 milk samples were collected from 28 mothers. We found that infant's GA, as well as the time of sampling, affected the levels of LF in milk. On one hand, LF showed higher content in human milk from group I (GA: 24-27.6 weeks) compared with the other groups (p < 0.01), and the levels of LF in colostrum were significantly correlated with GA (r = -0.31; p < 0.05). On the other hand, the LF content of milk had a significant decreasing trend over time. Overall, the highest values of LF were detected in preterm infants' maternal milk with a baby birth weight, lower than 1,400 g. Approximately 350 µg/mL was identified as the mean, physiological LF content in human mature milk in our population. Conclusions Levels of LF in human milk vary significantly over time during lactation and according to GA. This variability in the LF content of human milk may reflect the different needs of different infants during the early days and weeks of life. These data might help to inform models to design tailored supplementation strategies of LF in the nurseries and after home discharge.