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 discovered hormones, 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 ghrelin values 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.

SummaryNutrition and growth during infancy are an emerging issue because of their potential link to metabolic health disorders in later life. Moreover, prolonged breast-feeding appears to be associated with a lower risk of obesity than formula feeding. Human milk is a source of various hormones and growth factors, namely adipokines (leptin and adiponectin), ghrelin, resistin and obestatin, which are involved in food intake regulation and energy balance. These compounds are either not found in commercial milk formulas or their presence is still controversial. Diet-related differences during infancy in serum levels of factors involved in energy metabolism might explain anthropometric differences and also differences in dietary habits between breastfed (BF) and formula-fed (FF) infants later in life, and may thus have long-term health consequences. In this context, the recent finding of higher leptin levels and lower ghrelin levels in BF than in FF infants suggests that differences in hormonal values together with different protein intake could account for the differences in growth between BF and FF infants both during infancy and later in life. In this review, we examine the data related to hormones contained in mothers' milk and their potential protective effect on subsequent obesity and metabolicrelated disorders.

Aim: To establish ghrelin, leptin and IGF‐I serum levels in breastfed (BF) and formula‐fed (FF) infants during the first period of life. Methods: A cross‐sectional study was conducted on fasting blood venous samples obtained from exclusively BF (n=106) and FF (n=100) infants to measure total ghrelin (RIA test), leptin (RIA test) and IGF‐I (chemiluminescence). Anthropometrical measurements of weight, length and cranial circumference were performed. Results: During the first 4 mo of life, FF infants compared to BF ones showed higher ghrelin levels (2654.86 vs 2132.96 pg/ml; p<0.032), higher IGF‐I levels (3.73 vs 3.15 ng/ml; p=0.00) and lower leptin levels (0.68 vs 1.16 ng/ml; p<0.04). Leptin values were higher in females than in males (0.80 vs 0.47 ng/ml; p<0.03), while no gender‐related difference was found for ghrelin and IGF‐I. No differences were found in anthropometrical measurements comparing the two groups of infants. A multiple regression analysis showed an inverse correlation between ghrelin and leptin values (p<0.04) and between IGF‐I and leptin levels (p=0.00). Conclusion: Our finding suggests that breastfeeding influences hormones such as ghrelin, leptin and IGF‐I in infancy, mainly during the first 4 mo of life. Further evidence is needed to confirm and clarify the role of a protective link from mother to infants as seen in our observations.

Our finding suggests that breastfeeding influences hormones such as ghrelin, leptin and IGF-I in infancy, mainly during the first 4 mo of life. Further evidence is needed to confirm and clarify the role of a protective link from mother to infants as seen in our observations.

Background/Objectives: Leptin is present in human milk, but it is not clear what the relationship between breast milk (BM) leptin levels and maternal and infant serum leptin concentrations is. The objective of this study was to evaluate the leptin concentration in BM and to investigate its relationship with infants' and mothers' anthropometric parameters and with serum leptin concentration in breast-fed (BF) infants and lactating mothers. Subjects/Methods: We enrolled 36 adequate for gestational age healthy, exclusively BF, term infants aged o6 months. Leptin concentration in serum and BM was determined by radioimmunoassay (RIA) test (human-leptin-RIA-sensitive, Mediagnost). Infants' and mothers' weights, lengths and body mass indexes (BMI) were measured. Results: The median leptin concentration was 3.42 ng/ml (interquartile range (IR): 2.65) in BF infants' serum, 3.02 ng/ml (IR: 2.85) in mothers' serum (n ¼ 17) and 0.51 ng/ml (IR: 0.34) in BM (n ¼ 24). BM leptin concentrations were significantly lower than serum BF infant (Po0.001) and maternal (Po0.001) leptin levels. Infant serum leptin concentration correlated positively with infant weight (r ¼ 0.437, P ¼ 0.008) and BMI (r ¼ 0.561, P ¼ 0.004). Mother serum leptin levels correlated positively with weight (r ¼ 0.755, Po0.001) and BMI (r ¼ 0.661, P ¼ 0.007). No correlations were found between BM leptin and serum leptin concentrations in BF infants and mothers. Conclusions: We confirmed the presence of leptin in BM at a lower concentration than that found in infant and lactating mother serum. We observed a positive correlation between serum leptin levels in BF infants and their growth parameters.

Growing evidence suggests that a complex relationship exists between the central nervous system and peripheral organs involved in energy homeostasis. It consists in the balance between food intake and energy expenditure and includes the regulation of nutrient levels in storage organs, as well as in blood, in particular blood glucose. Therefore, food intake, energy expenditure, and glucose homeostasis are strictly connected to each other. Several hormones, such as leptin, adiponectin, resistin, and ghrelin, are involved in this complex regulation. These hormones play a role in the regulation of glucose metabolism and are involved in the development of obesity, diabetes, and metabolic syndrome. Recently, their presence in breast milk has been detected, suggesting that they may be involved in the regulation of growth in early infancy and could influence the programming of energy balance later in life. This paper focuses on hormones present in breast milk and their role in glucose homeostasis.

Objectives: Ghrelin, a recently discovered hormone mainly secreted by the stomach, has several metabolic functions including regulation of food intake, energy homeostasis and body weight. There are few studies on this hormone in healthy infants during the first year of life. The aim of this study was to examine the correlations between ghrelin and weight gain in healthy term infants in the first year of life. Methods: 104 healthy term infants aged 0 to 12 months were included in a cross‐sectional study. Anthropometric measurements were assessed and mean weight gain was calculated. Serum ghrelin concentrations have been determined at least 3 hours after feeding by radioimmunoassay test. Results: Ghrelin concentrations were correlated negatively to weight gain (r = −0.302; P = 0.003) and positively to age (r = 0.412; P < 0.001), weight (r = 0.374; P < 0.001) and length (r = 0.387; P < 0.001). In breastfed infants a statistically significant negative correlation between ghrelin concentration and infant weight gain (r = −0.407; P = 0.001) was observed, whereas in formula‐fed infants this correlation was not statistically significant (r = −0.067; P = 0.719). Conclusions: The negative correlation observed between ghrelin concentration and infant weight gain suggests that ghrelin might also play a role in the regulation of body weight in healthy infants with a physiologic energy balance. Further studies are needed to clarify how ghrelin might be involved in both short‐term and long‐term energy balance.

We carried out a cross-sectional study of 115 healthy infants, younger than 6 months old, exclusively breast-fed or formula-fed, to investigate correlations between circulating leptin concentrations and body composition measurements. Serum leptin was evaluated with radioimmunoassay, and body composition with bioelectrical impedance analysis. Multiple regression analysis showed a relationship between serum leptin and body mass index in the entire study population (P = 0.042). There was a significant negative relationship between serum leptin and phase angle (P = 0.006) in formula-fed infants. Serum leptin was positively related to subscapular skinfold thickness (P = 0.055) and negatively to reactance (P = 0.057) only in formula-fed infants, although the differences were just below significance. Serum leptin concentration was higher in breast-fed infants (P = 0.002), and was not correlated with body composition parameters. This study indicates that there is a relation between leptin and infant body composition in the first months of life, although the link needs to be explored further.