LEPTIN EXPRESSION IN HUMAN MAMMARY EPITHELIAL-CELLS AND BREAST-MILK

Leptin has recently been shown to be produced by the human placenta an d potentially plays a role in fetal and neonatal growth. Many function s of the placenta are replaced by the mammary gland in terms of provid ing critical growth factors for the newborn. In this study, we show th at leptin is produced by human mammary epithelial cells as revealed by RT/PCR analysis of total RNA from mammary gland and immunohistochemic al staining of breast tissue, cultured mammary epithelial cells, and s ecretory epithelial cells present in human milk. We also verify that i mmunoreactive leptin is present in whole milk at 30- to 150-fold highe r concentrations than skim milk. We propose that leptin is secreted by mammary epithelial cells in milk fat globules, which partition into t he lipid portion of breast milk.