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Hindawi Publishing Corporation International Journal of Pediatric Endocrinology Volume 2009, Article ID 327505, 8 pages doi:10.1155/2009/327505

Review Article Breast Milk Hormones and Their Protective Effect on Obesity
Francesco Savino, Stefania A. Liguori, Maria F. Fissore, and Roberto Oggero
Department of Pediatrics, Regina Margherita Children’s Hospital, University of Turin, 10126 Turin,Italy Correspondence should be addressed to Francesco Savino, francesco.savino@unito.it Received 8 May 2009; Accepted 27 September 2009 Recommended by Jesus Argente Data accumulated over recent years have significantly advanced our understanding of growth factors, cytokines, and hormones in breast milk. Here we deal with leptin, adiponectin, IGF-I, ghrelin, and the more recently discoveredhormones, obestatin, and resistin, which are present in breast milk and involved in food intake regulation and energy balance. Little is known about these compounds in infant milk formulas. Nutrition in infancy has been implicated in the long-term tendency to obesity, and a longer duration of breastfeeding appears to protect against its development. Diet-related differences in serum leptin and ghrelinvalues in infancy might explain anthropometric differences and differences in dietary habits between breast-fed and formula-fed infants also later in life. However, there are still gaps in our understanding of how hormones present in breast milk affect children. Here we examine the data related to hormones contained in mother’s milk and their potential protective effect on subsequent obesity. Copyright ©2009 Francesco Savino et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction
Studies on the physiology of breastfeeding revealed the presence of the two adipokines, leptin [1] and adiponectin [2], hormones, suchas IGF-I [3], ghrelin [4], and more recently obestatin [5] and resistin [6] in mother’s milk (Table 1). Human milk is a complex biological fluid: leptin and ghrelin are synthesized and secreted into breast milk by the mammary gland and pass from serum into milk. The origin of adiponectin, obestatin, and resistin remains to be established. Leptin and ghrelin have a positive effect on the early controlof satiety in infants and could influence the programming of energy balance regulation in childhood and adulthood thereby protecting against later obesity [7]. It is noteworthy that childhood obesity is associated with an increased risk of adult metabolic syndrome [8]. Here, we review data related to hormones contained in mother’s milk and their potential protective effect on subsequent obesity.1.1. Leptin. Leptin is an adipocyte-derived hormone discovered in 1994 [9]. It reduces appetite and increases energy expenditure by acting on the arcuate nucleus in the hypothalamus through its receptor (Ob-R) [10]. Circulating leptin levels correlate with fat mass in adults and children [11].

Leptin is detectable in cord blood from the second trimester of intrauterine life and correlates withadiposity at birth [12]. Interestingly, serum leptin concentration correlates with body mass index (BMI) in infants [13]. In obese subjects, endogenous leptin, even at high circulating levels, fails to exert its normal effects, and administration of exogenous leptin does not significantly reduce adiposity. This condition, known as “leptin resistance”, could be due to reduced transport of leptin intothe brain and reduced expression of leptin receptor in the arcuate nucleus or an increased concentration of SOCS3, which suppresses leptin signaling by inhibiting leptin-induced STAT activation [14]. Leptin has been implicated in the neonatal development of the hypothalamic pathways involved in the central regulation of energy balance and appetite [15]. Studies conducted in mice have shown that...