Leptin levels in breast-fed infants

High serum leptin levels in infancy can potentially predict obesity in childhood, especially in formula-fed infants

AIM

To investigate serum leptin levels in breast-fed and formula-fed infants in infancy and their possible relationship to body mass index (BMI) in childhood.

METHODS

We enrolled 237 healthy term infants between September 2000 and April 2004 and tested their serum leptin levels, took anthropometric measurements and calculated BMI. A follow-up study was carried out to evaluate the BMI of 89 of these infants in childhood, in relation to their serum leptin levels in infancy, at a median (interquartile range) age of 8.8 years (7.8-10.2). The statistical significance of this multivariate analysis was set at p < 0.05.

RESULTS

Breast-fed infants had significantly higher serum leptin levels than formula-fed ones (p < 0.05). Children who were formula-fed in infancy had a significantly higher BMI, at follow-up, than those who were breast-fed (p < 0.001). Furthermore, we identified a leptin cut-off value of 2.7 ng/mL, below which infants had a higher BMI in childhood.

CONCLUSION

A higher leptin level in infancy may be inversely associated with BMI in childhood, suggesting that this hormone in infancy is a potential predictor of obesity in later life. Further investigation is required to be conclusive and to confirm our empirical evidence.

Adipokines in breast milk and preterm infants

Studies have shown that the early life environment affects feeding behaviour, food intake and energy balance in later life, suggesting there is a link between foetal and infant growth and the risk of metabolic disorders in adulthood. Although there is an evident epidemiological association between low birth weight and adult-onset diseases, the incidence of metabolic diseases in adulthood among people who were born prematurely is still unknown. Considerable advances have been made during the last years in the scientific knowledge of the benefits of early nutrition, such as breastfeeding, on health and well-being later in life. Nutritional researchers have focussed their attention on the biological characteristics of human breast milk, which represents the main source of nutrients in the first months of life for breastfed infants. Recently, leptin and ghrelin have been detected in the breast milk of mothers of term and preterm infants. Adiponectin and resistin, present in term human milk, have not been investigated in the breast milk of mothers of preterm infants. These hormones are involved in the regulation of energy balance and may have a role in the regulation of growth and development in the neonatal period and infancy, as well as long-term effects on metabolic programming. Leptin, adiponectin and resistin have been found at lower levels in pre-term infants compared with term newborns, whereas there seems to be no difference in ghrelin levels. Future research is necessary to clarify the role of hormones present in breast milk for identifying potential short- and long-term effects of breastfeeding on the health of children born prematurely.

Can hormones contained in mothers' milk account for the beneficial effect of breast-feeding on obesity in children?

Nutrition 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 breast-fed (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 metabolic-related disorders.

Breast milk hormones and their protective effect on obesity

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.

The relationship between breast milk leptin and neonatal weight gain

AIM

To investigate whether change in leptin content of breast milk during lactation acts on neonatal body weight gain.

METHODS

In total 15 lactating women and their 15 term infants were involved in the study. Breast milk and neonatal serum samples were obtained from the same women and their neonates on the 1st day and any day between the 21st and 30th days after birth. Breast milk and serum leptin concentrations were determined by radioimmunoassay. Anthropometric indexes of the infants were recorded.

RESULTS

The study was completed with 15 multiparious mothers aged 19-37 years and their infants. The mean collection time of the first samples after birth was 6.07 +/- 1.94 h. The leptin level in the mature milk was significantly higher than in the colostrum (p < 0.001). Neonatal weight and height were significantly increased on 21-30 lactation days compared to 1st day of lactation (p < 0.05 and p < 0.001, respectively). The leptin concentration in the mature milk was negatively correlated with delta BMI (r =-0.53; p < 0.05). The delta breast milk leptin concentration was also found to be inversely correlated with delta BMI (r =-0.529; p < 0.05).

CONCLUSION

The results of this study have suggested that change in the leptin content of breast milk during lactation might play a role in the regulation of weight gain in healthy neonates.

Looking for a relation between serum leptin concentration and body composition parameters in healthy term infants in the first 6 months of life

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.

Bile salt-stimulated lipase and pancreatic lipase-related protein 2 are the dominating lipases in neonatal fat digestion in mice and rats

During infancy, the basic conditions for digestion of dietary fat differ from later in life. The bile salt-stimulated lipase (BSSL) is an enzyme expressed in the exocrine pancreas and in some species (including human) also in the lactating mammary gland and secreted with the milk. The aim of this study was to compare the ontogeny of four pancreatic lipases [BSSL, pancreatic triglyceride lipase (PL), pancreatic lipase-related protein 2 (PLRP2), and phospholipase A2 (PLA2)] in one species that supplies BSSL with milk (the mouse) and one that does not (the rat). We followed expression of the four pancreatic lipases from postnatal d 1 until after weaning in both species. We found that BSSL and PLRP2, two lipases with broad substrate specificity, dominated. It was not until weaning that significant expression of PL and PLA2 were induced. Thus, BSSL and PLRP2 seem to be responsible for fat digestion as long as milk is the main food. Moreover, the early temporal pattern of BSSL expression differed between species. We speculate that the milk-borne BSSL is able to compensate for a slower ontogeny of pancreatic BSSL expression in the mouse.

Update on breast milk hormones: leptin, ghrelin and adiponectin

Recent evidences suggest that a number of chronic diseases seems to be associated with early prenatal and postnatal nutrition, even though the mechanisms underlying the link between early nutrition, health and well-being later in life have not been well understood. Considering that overweight and obesity derive from a condition of altered energy balance, one of the major interests of nutritional researchers is to provide breakthroughs in the understanding of hormonal patterns involved in energy balance regulation. Epidemiological surveys indicate that breastfeeding is protective against obesity in later life, even if the precise magnitude of this association remains not well defined. A lot of studies have shown the detection of hormones in breast milk, which have a role in energy balance regulation. In this review, we present a synopsis of previous and recent studies focusing on hormones in breast milk. It appears that promoting breastfeeding is an important factor in this process.

Serum ghrelin concentration, fasting time and feeding in infants

BACKGROUND

Data on hormonal feeding control in infants in the first months of life according to the kind of feeding are scanty.

AIM

To evaluate whether serum ghrelin could be involved in feeding behaviour control of breast-fed (BF) and formula fed (FF) infants.

METHODS

We studied 50 AGA healthy term infants aged 1-6 months of age. Serum ghrelin concentration was determined by RIA. Fasting time (measured as the difference between the time of the last meal and the time of blood collection) and number of meals were recorded.

RESULTS

A positive correlation between serum ghrelin levels and fasting time emerged in FF infants (r = 0.752; p <0.001) but not in BF infants (r = 0.345; p = 0.072).

CONCLUSIONS

Circulating ghrelin concentration correlates positively with fasting time in FF infants; these infants have higher serum ghrelin concentration, longer fasting time and fewer meals than BF infants. These observations suggest a possible influence of early feeding on mechanisms regulating satiety and feeding behaviour.