Authors: (Francesco Savino, Stefania Alfonsina Liguori, Maria Maddalena Lupica Department of Paediatrics, University of Turin, Regina Margherita Children’s Hospital, Italy)
Abstract: Leptin, the product of the ob gene, is a 167 amino acid peptide hormone mainly synthesized by the white adipose tissue and released in circulation proportionally to the amount of body fat mass. It is involved in the regulation of energy balance, reducing appetite and increasing energy expenditure by acting on the arcuate nucleus in the hypothalamus. Leptin is also produced by human placenta and seems to play a role in foetal and neonatal growth. Recently it has been implicated in the neonatal development of hypothalamic pathways involved in the central regulation of energy balance and appetite. Moreover leptin is present in human milk, both produced by mammary epithelial cells and transferred by secretory epithelial cells from blood to milk. Leptin concentration is higher in whole than in skimmed samples of human milk, probably because a portion of leptin could be associated with the milk fat droplet or fat-associated proteins. Leptin is present also in preterm human breast milk with similar levels to those noted in term breast milk, even though also lower levels have been detected after preterm than after term delivery. Leptin receptors have been identified in gastric epithelial cells and in the absorptive cells of mouse and human small intestine, which suggests that leptin could pass from milk to infant blood.