Presence of bovine leptin in edible commercial milk and infant formula

Leptin: Master Regulator of Biological Functions that Affects Breathing

Obesity is a global epidemic in developed countries accounting for many of the metabolic and cardiorespiratory morbidities that occur in adults. These morbidities include type 2 diabetes, sleep-disordered breathing (SDB), obstructive sleep apnea, chronic intermittent hypoxia, and hypertension. Leptin, produced by adipocytes, is a master regulator of metabolism and of many other biological functions including central and peripheral circuits that control breathing. By binding to receptors on cells and neurons in the brainstem, hypothalamus, and carotid body, leptin links energy and metabolism to breathing. In this comprehensive article, we review the central and peripheral locations of leptin's actions that affect cardiorespiratory responses during health and disease, with a particular focus on obesity, SDB, and its effects during early development. Obesity-induced hyperleptinemia is associated with centrally mediated hypoventilation with decrease CO₂ sensitivity. On the other hand, hyperleptinemia augments peripheral chemoreflexes to hypoxia and induces sympathoexcitation. Thus, "leptin resistance" in obesity is relative. We delineate the circuits responsible for these divergent effects, including signaling pathways. We review the unique effects of leptin during development on organogenesis, feeding behavior, and cardiorespiratory responses, and how undernutrition and overnutrition during critical periods of development can lead to cardiorespiratory comorbidities in adulthood. We conclude with suggestions for future directions to improve our understanding of leptin dysregulation and associated clinical diseases and possible therapeutic targets. Lastly, we briefly discuss the yin and the yang, specifically the contribution of relative adiponectin deficiency in adults with hyperleptinemia to the development of metabolic and cardiovascular disease. © 2020 American Physiological Society. Compr Physiol 10:1047-1083, 2020.

Mother and Infant Body Mass Index, Breast Milk Leptin and Their Serum Leptin Values

Purpose: This study investigates correlations between mother and infant Body Mass Index (BMI), their serum leptin values and breast milk leptin concentration in early infancy. Subjects and Methods: We determined serum leptin values in 58 healthy infants and leptin values in their mothers’ breast milk, using radioimmunoassay (RIA). Infant and maternal anthropometrics were measured. Results: Median leptin concentration was 3.9 ng/mL (interquartile range (IQR): 2.75) in infant serum, 4.27 ng/mL (IQR: 5.62) in maternal serum and 0.89 ng/mL (IQR: 1.32) in breast milk. Median maternal BMI and weight were 24 kg/m² (IQR: 4.41) and 64 kg (IQR: 15). Median infant BMI was 15.80 kg/cm² (IQR: 4.02), while average weight was 5.130 kg (IQR: 1.627). Infants serum leptin values positively correlated with infants’ BMI (p = 0.001; r = 0.213) and breast milk leptin (p = 0.03; r = 0.285). Maternal serum leptin values positively correlated with maternal BMI (p = 0.000, r = 0.449) and breast milk leptin ones (p = 0.026; r = 0.322). Conclusion: Breast milk leptin and maternal BMI could influence infant serum leptin values. Further studies are needed to better elucidate the role of genetics and environment on infant leptin production and risk of obesity later in life.

Effect of Technological Treatments on Human-Like Leptin Level in Bovine Milk for Human Consumption

In this experiment, raw milk and commercially available full-cream UHT milk, semi-skimmed UHT milk, skimmed UHT milk, full-cream pasteurized milk, semi-skimmed pasteurized milk and infant formulas for babies between 6 and 12 months of age were analyzed by RIA, with a method using an antibody directed against human leptin and human leptin as reference standard. Raw milk and full-cream UHT milk did not differ for human-like leptin. Leptin content of full-cream pasteurized milk was not different to that of full-cream UHT milk, but it was 14% lower (p < 0.05) than that observed in raw milk. Human-like leptin level of semi-skimmed UHT milk was not different to that of semi-skimmed pasteurized milk, but it was 30% lower (p < 0.0001) than those of full-cream UHT and full-cream pasteurized milks. In skimmed UHT milk, leptin was 40% lower (p < 0.0001) than in full-cream UHT milk. Leptin was correlated (p < 0.001) with lipid content. Leptin level of infant formulas was not different to that of skimmed milks. Results suggest that the heat treatment (pasteurization or UHT) is not a modifier of human-like leptin content of edible commercial bovine milks, whereas the skimming process significantly reduces milk leptin level.

Breastmilk ghrelin, leptin, and fat levels changing foremilk to hindmilk: is that important for self-control of feeding?

The aim of this study was to evaluate the changes in the ghrelin, leptin, and fat levels in the foremilk and hindmilk and the possible relationship between these levels with the age and growth of term healthy infants. Sixty-two babies were subdivided (according to their nutrition) into breastfed (BF), formula-fed (FF), and BF plus FF (BF + FF) groups. The total and active ghrelin and tryglyceride levels and the total cholesterol levels in the foremilk and hindmilk were studied at the first and second visits (mean of the second and fifth months, respectively). At both visits, the total and active ghrelin and the total cholesterol levels were lower in the hindmilk than in the foremilk. However, the triglyceride levels were higher in the hindmilk than in the foremilk (p < 0.001). The leptin levels were also higher in the hindmilk, but this difference was not statistically significant. At the second visit, the mean total foremilk ghrelin (p < 0.01), leptin (p < 0.05), tryglyceride (p < 0.001), and cholesterol (p < 0.01) levels in the BF group were decreased compared with the levels at the first visit, whereas the active ghrelin levels increased (p < 0.001). At the second visit, we observed a 3.5% increase in the body mass index in BF infants, a 14.6% increase in FF infants, and an 11.8% increase in BF + FF infants (p < 0.01). The foremilk leptin levels were lower in the BF + FF group than in the BF group at both visits. In conclusion, at the first and second visits, the decreased ghrelin and increased tryglyceride and leptin levels in the hindmilk might be associated with the important role of self-control when feeding BF infants. The stable content of formulas might be associated with a lack of self-control during feeding and increased nutrition. Changing the breast milk ghrelin, leptin, and fat levels between the foremilk and hindmilk and between the first and second visits might explain the differences in the weight gain patterns of BF and FF infants.

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.

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.

Determinants of early life leptin levels and later life degenerative outcomes

The early (intrauterine and neonatal) life environment plays an important role in programming the susceptibility in later life to chronic degenerative diseases, such as obesity, cardiovascular diseases, diabetes mellitus, cancer and osteoporosis. Among other hormones, leptin plays a major role in the regulation of the overall metabolism and has multiple neuroendocrine (adeno- and neuro-hypophysis axes and the hypothalamus-pituitary-adrenal axis) and immune functions. The hormone exerts its actions beginning in the early life time period, regulating the intrauterine and early extrauterine life growth and development, as well as the adaptation to extrauterine life, neonatal thermogenesis and response to stress. Recent findings also support a role of leptin in the process of fetal bone remodeling and brain development. Therefore, it is of interest to explore the physiology of leptin in early life, as well as those factors that may perturb the balance of the hormone with pathological consequences in terms of confining an increased risk for disease in later life. This review aims to summarize reported findings concerning the role of leptin in early life, as well as the association of fetal, maternal and placental factors with leptin levels, while attempting to speculate mechanisms through which these factors may influence the risk for developing chronic diseases in later life.

Longitudinal investigation of the relationship between breast milk leptin levels and growth in breast-fed infants

BACKGROUND

It has been shown that leptin is present in breast milk and human mammary epithelial cells are able to synthesize leptin. It has been suggested that leptin in human milk might be involved in the regulation of postnatal nutrition and growth.

AIMS

To investigate whether there is a relationship between leptin levels in human milk and weight gain in the postnatal period and to compare variations of milk-borne maternal leptin concentrations for small for gestational age (SGA), large for gestational age (LGA) and appropriate for gestational age (AGA) infants.

INFANTS AND METHODS

Forty-seven healthy lactating women aged from 17-38 years and their infants were included in the study. The infants were separated into three groups according to birth weight as SGA (n = 11), LGA (n = 14) and AGA (n = 22). All infants were fed with breast milk during the study period. Anthropometric measurements were performed on the 15th day of life and at 1, 2, and 3 months of age, and the body mass index (BMI) of the infants' mothers was calculated. Breast milk leptin levels were analyzed by radioimmunoassay.

RESULTS

Breast milk leptin levels were found reduced in the SGA group and increased in the LGA group compared to the AGA group at 15 days of life (13.4 +/- 2.2, 28.5 +/- 4.4 and 18.4 +/- 2 ng/ml, respectively; p <0.05). At 1 month of age, leptin levels in breast milk were significantly lower in the LGA group than in the AGA group (15.5 +/- 4.9, 19.4 +/- 1.7 ng/ml, respectively; p<0.05). There was no difference among the three groups at 2 and 3 months of age (p>0.05). There was a positive correlation between birth Weight and breast milk leptin levels on the 15th day (r = 0.47, p = 0.001). A negative correlation was found between weight gain during the first 15 days and 1 month of life and breast milk leptin levels on the 15th day (r = -0.44, p = 0.002; r = -0.40, p = 0.005, respectively). No relationship could be determined between breast milk leptin levels and BMI of the mothers.

CONCLUSION

Maternal milk of SGA, LGA and AGA infants had different leptin levels, especially during the first month of life. More rapid growth was shown in the SGA infants during the first postnatal 15 days compared to AGA and LGA infants, and human milk leptin levels were significantly reduced in the SGA group. However, LGA infants gained more weight during the second 15 days of life and breast milk leptin levels were dramatically decreased in LGA and increased in SGA infants at the end of first month of life. These findings suggest that the presence of leptin in breast milk might have a significant role in growth, appetite and regulation of nutrition in infancy, especially during the early lactation period, and the production of leptin in breast tissue by human mammary epithelial cells might be regulated physiologically according to necessity and state of the infant.