Breast milk leptin concentrations in initial and terminal milk samples: relationships to maternal and infant plasma leptin concentrations, adiposity, serum glucose, insulin, lipid and lipoprotein levels.

Leptin has recently been shown to be present in human milk and is produced by mammary epithelial cells. We studied leptin concentrations in human milk and its relationships with maternal and infant plasma leptin concentrations, adiposity, serum glucose, insulin, lipid and lipoprotein levels. We also compared the initial and terminal milk leptin concentrations to investigate whether leptin acts as a satiety factor. Venous blood samples were obtained from 18 healthy lactating women aged from 17-42 years and their 3-120 day-old infants. Breast milk samples were collected just before and immediately after suckling, when the infant had self-terminated sucking. Leptin mean values in breast milk were lower than in maternal plasma (p<0.001). Breast milk log leptin concentrations positively correlated with both maternal and infant plasma log leptin concentrations (p<0.001 and p=0.001, respectively) and negatively correlated with maternal serum total cholesterol and low-density lipoprotein cholesterol levels (p<0.001 and p<0.01, respectively), but did not correlate with maternal and infant adiposity, serum glucose and insulin levels, maternal serum HDL-C, triglyceride levels and infants' lipid and lipoprotein concentrations (p>0.05). Using stepwise multiple regression analysis, maternal plasma log leptin and serum HDL-C concentrations were related to breast milk log leptin concentration (R2=0.82; p<0.0001 and p<0.001, respectively). There was no significant difference between initial and terminal milk leptin levels (p>0.05). We concluded that maternal leptin may be transferred to the infant via milk and may exert biological effects; there may be factors other than adiposity affecting breast milk leptin levels, and that leptin might not contribute to the development of satiation at the end of suckling.