The Effects of Leptin on Breastfeeding Behaviour

Is Maternal Body Weight or Composition Associated with Onset of Lactogenesis II, Human Milk Production, or Infant Consumption of Mother's Own Milk? A Systematic Review and Meta-Analysis

Maternal adiposity impacts lactation performance, but the pathways are unclear. We conducted a systematic review to understand whether maternal adiposity (body mass index [BMI] or percentage fat mass) is associated with onset of lactogenesis II (copious milk; hours), human milk production (expressed volume/24 h), and infant consumption of mother's own milk (volume/24 h). We used random-effects standard meta-analyses to compare the relative risk (RR) of delayed lactogenesis II (>72 h) between mothers classified as underweight (BMI <18.5 kg/m2), healthy weight (BMI, 18.5-24.9 kg/m2), and overweight/obese (BMI ≥25 kg/m2) and random-effects meta-regressions to examine associations with hours to lactogenesis II and infant milk consumption. The certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation approach. We included 122 articles. Mothers with underweight (RR: 0.64; 95% CI: 0.49, 0.83; I2 = 39.48%; 8 articles/data points) or healthy weight status (RR: 0.67; 95% CI: 0.57, 0.79; I2 = 70.91%; 15 articles/data points) were less likely to experience delayed lactogenesis II than mothers with overweight/obesity. We found no association between maternal BMI and time to onset of lactogenesis II (β: 1.45 h; 95% CI: -3.19, 6.09 h; P = 0.52, I2 = 0.00%; 8 articles, 17 data points). Due to limited data, we narratively reviewed articles examining BMI or percentage fat mass and milk production (n = 6); half reported an inverse association and half no association. We found no association between maternal BMI (β: 6.23 mL; 95% CI: -11.26, 23.72 mL; P = 0.48, I2 = 47.23%; 58 articles, 75 data points) or percentage fat mass (β: 7.82 mL; 95% CI: -1.66, 17.29 mL; P = 0.10, I2 = 28.55%; 30 articles, 41 data points) and infant milk consumption. The certainty of evidence for all outcomes was very low. In conclusion, mothers with overweight/obesity may be at risk of delayed lactogenesis II. The available data do not support an association with infant milk consumption, but the included studies do not adequately represent mothers with obesity. This study was registered in PROSPERO as 285344.

Human Milk Macronutrients and Child Growth and Body Composition in the First Two Years: A Systematic Review

Among exclusively breastfed infants, human milk (HM) provides complete nutrition in the first mo of life and remains an important energy source as long as breastfeeding continues. Consisting of digestible carbohydrates, proteins, and amino acids, as well as fats and fatty acids, macronutrients in human milk have been well studied; however, many aspects related to their relationship to growth in early life are still not well understood. We systematically searched Medline, EMBASE, the Cochrane Library, Scopus, and Web of Science to synthesize evidence published between 1980 and 2022 on HM components and anthropometry through 2 y of age among term-born healthy infants. From 9992 abstracts screened, 57 articles reporting observations from 5979 dyads were included and categorized based on their reporting of HM macronutrients and infant growth. There was substantial heterogeneity in anthropometric outcome measurement, milk collection timelines, and HM sampling strategies; thus, meta-analysis was not possible. In general, digestible carbohydrates were positively associated with infant weight outcomes. Protein was positively associated with infant length, but no associations were reported for infant weight. Finally, HM fat was not consistently associated with any infant growth metrics, though various associations were reported in single studies. Fatty acid intakes were generally positively associated with head circumference, except for docosahexaenoic acid. Our synthesis of the literature was limited by differences in milk collection strategies, heterogeneity in anthropometric outcomes and analytical methodologies, and by insufficient reporting of results. Moving forward, HM researchers should accurately record and account for breastfeeding exclusivity, use consistent sampling protocols that account for the temporal variation in HM macronutrients, and use reliable, sensitive, and accurate techniques for HM macronutrient analysis.

Human Milk Bioactive Components and Child Growth and Body Composition in the First 2 Years: A Systematic Review

Human milk (HM) contains macronutrients, micronutrients, and a multitude of other bioactive factors, which can have a long-term impact on infant growth and development. We systematically searched MEDLINE, EMBASE, Cochrane Library, Scopus, and Web of Science to synthesize evidence published between 1980 and 2022 on HM components and anthropometry through 2 y of age among term-born infants. From 9992 abstracts screened, 141 articles were included and categorized based on their reporting of HM micronutrients, macronutrients, or bioactive components. Bioactives including hormones, HM oligosaccharides (HMOs), and immunomodulatory components are reported here, based on 75 articles from 69 unique studies reporting observations from 9980 dyads. Research designs, milk collection strategies, sampling times, geographic and socioeconomic settings, reporting practices, and outcomes varied considerably. Meta-analyses were not possible because data collection times and reporting were inconsistent among the studies included. Few measured infant HM intake, adjusted for confounders, precisely captured breastfeeding exclusivity, or adequately described HM collection protocols. Only 5 studies (6%) had high overall quality scores. Hormones were the most extensively examined bioactive with 46 articles (n = 6773 dyads), compared with 13 (n = 2640 dyads) for HMOs and 12 (n = 1422 dyads) for immunomodulatory components. Two studies conducted untargeted metabolomics. Leptin and adiponectin demonstrated inverse associations with infant growth, although several studies found no associations. No consistent associations were found between individual HMOs and infant growth outcomes. Among immunomodulatory components in HM, IL-6 demonstrated inverse relationships with infant growth. Current research on HM bioactives is largely inconclusive and is insufficient to address the complex composition of HM. Future research should ideally capture HM intake, use biologically relevant anthropometrics, and integrate components across categories, embracing a systems biology approach to better understand how HM components work independently and synergistically to influence infant growth.

Circadian Variation in Human Milk Hormones and Macronutrients

There is an inadequate understanding of the daily variations in hormones and macronutrients in human milk (HM), and sample collection protocols vary considerably from study to study. To investigate changes in these milk components across 24 h, 22 lactating women collected small milk samples before and after each breastfeed or expression from each breast. Test weighing was used to determine the volume of HM consumed in each feed. The concentrations of leptin, adiponectin, insulin, fat, and glucose were measured, and the intakes were calculated. A linear mixed model was fitted to assess within-feed and circadian variation in HM feed volume and concentration, and intakes of several components. The average infant intake of HM was 879 g/24 h. Significantly higher pre-feed concentrations were found for adiponectin and glucose and lower post-feed concentrations were found for insulin and fat. Significant circadian rhythms were displayed for leptin, adiponectin, insulin, glucose (both concentration and intake), fat concentration, and milk volume. These findings demonstrate the necessity for setting up standardised and rigorous sampling procedures that consider both within-feed and circadian variations in HM components to gain a more precise understanding of the impacts of these components on infant health, growth and development.

Circle(s) of Life: The Circadian Clock from Birth to Death

Most lifeforms on earth use endogenous, so-called circadian clocks to adapt to 24-h cycles in environmental demands driven by the planet’s rotation around its axis. Interactions with the environment change over the course of a lifetime, and so does regulation of the circadian clock system. In this review, we summarize how circadian clocks develop in humans and experimental rodents during embryonic development, how they mature after birth and what changes occur during puberty, adolescence and with increasing age. Special emphasis is laid on the circadian regulation of reproductive systems as major organizers of life segments and life span. We discuss differences in sexes and outline potential areas for future research. Finally, potential options for medical applications of lifespan chronobiology are discussed.

Development of the circadian system in early life: maternal and environmental factors

In humans, an adaptable internal biological system generates circadian rhythms that maintain synchronicity of behavior and physiology with the changing demands of the 24-h environment. Development of the circadian system begins in utero and continues throughout the first few years of life. Maturation of the clock can be measured through sleep/wake patterns and hormone secretion. Circadian rhythms, by definition, can persist in the absence of environmental input; however, their ability to adjust to external time cues is vital for adaptation and entrainment to the environment. The significance of these external factors that influence the emergence of a stable circadian clock in the first years of life remain poorly understood. Infants raised in our post-modern world face adverse external circadian signals, such as artificial light and mistimed hormonal cues via breast milk, which may increase interference with the physiological mechanisms that promote circadian synchronization. This review describes the very early developmental stages of the clock and common circadian misalignment scenarios that make the developing circadian system more susceptible to conflicting time cues and temporal disorder between the maternal, fetal, infant, and peripheral clocks.

Breast Milk and the Importance of Chrononutrition

During pregnancy the human fetus receives timed cues from the circadian rhythms of temperature, metabolites, and hormones from the mother. This influence is interrupted after parturition, the infant does not secrete melatonin and their circadian rhythms are still immature. However, evolution provided the solution to this problem. The newborn can continue receiving the mother's timed cues through breastmilk. Colostrum, transitional, and mature human milk are extraordinary complex biofluids that besides nutrients, contain an array of other non-nutritive components. Upon birth the first milk, colostrum, is rich in bioactive, immunological factors, and in complex oligosaccharides which help the proper establishment of the microbiome in the gut, which is crucial for the infants' health. Hormones, such as glucocorticoids and melatonin, transfer from the mother's plasma to milk, and then the infant is exposed to circadian cues from their mother. Also, milk components of fat, proteins, amino acids, and endogenous cannabinoids, among others, have a markedly different concentration between day and night. In the present review, we give an overview of nutritive and non-nutritive components and their daily rhythms in human milk and explore their physiological importance for the infant. Finally, we highlight some interventions with a circadian approach that emphasize the importance of circadian rhythms in the newborn for their survival, proper growth, and development. It is estimated that ~600,000 deaths/year are due to suboptimal breastfeeding. It is advisable to increase the rate of exclusive breastfeeding, during the day and night, as was established by the evolution of our species.

Human Milk Glucose, Leptin, and Insulin Predict Cessation of Full Breastfeeding and Initiation of Formula Use

Objective: We aimed to investigate prospective associations between milk bioactives related to metabolic health (glucose, insulin, leptin, C reactive protein [CRP], and interleukin 6 [IL-6]) and incident formula initiation at 3 and 6 months postpartum. Design: This study included 363 mother-infant dyads who were fully breastfed at 1 month and participated in the prospective Mothers and Infants Linked for Healthy Growth study from pregnancy to 6 months postpartum. Associations between milk glucose, leptin, insulin, CRP, and IL-6 at 1 and 3 months and incident formula feeding (FF) at 3 and 6 months, respectively, were tested using multiple logistic regression, adjusting for numerous potential confounders such as maternal age and prepregnancy body mass index. Results: At 3 months postpartum, 1-month glucose (odds ratio [OR] 0.45 [95% confidence interval (CI): 0.27-0.75], p ≤ 0.01) and smaller decreases in glucose from 1 to 3 months (OR 0.51 [95% CI: 0.28-0.92], p = 0.03) were associated with lower odds of FF, whereas 1-month leptin (OR 2.30 [95% CI: 1.30-4.07], p < 0.01) and larger increase in insulin (OR 1.86 [95% CI: 1.23-2.81], p < 0.01) and leptin (OR 2.17 [95% CI: 1.29-3.68], p < 0.01) from 1 to 3 months were associated with increased odds of FF. At 6 months, insulin increases (OR 2.08 [95% CI: 1.03-4.17], p = 0.04) were associated with higher odds of FF. Conclusions: In a cohort of women with established lactation, 1-month milk glucose, insulin, and leptin predicted initiation of FF at 3 months. Early milk composition may provide a window into mammary gland function, allowing identification of women at risk of not meeting their breastfeeding goals.

Chrononutrition and Breast Milk: A Review of the Circadian Variation of Hormones Present in Human Milk

Introduction

Breast milk contains a wide range of hormones, nutrients, and bioactive compounds. Chrononutrition looks at the interaction between food, both meal timing and meal composition, and circadian rhythms.

Method

This review is a continuation on series on chrononutrition and breast milk. All human studies published in English were included regardless of location or year of publication.

Results

This review identifies the hormonal circadian variation researched in breast milk to date for melatonin, cortisol, cortisone, leptin, and insulin.

Conclusion

The circadian variation observed in some hormones reinforces the superiority of breast milk over formula milk. Melatonin has been the most studied, but more research for all the hormones is needed due to various gaps in the literature and varying levels of study quality. There is insufficient evidence to make recommendations specifically targeting the lactating mother, but we identify and recommend several ideas for future research.

Human Milk Metabolic Hormones: Analytical Methods and Current Understanding

Human milk (HM) contains a wide array of peptide hormones including leptin and adiponectin, which are involved in the regulation of infant growth and development. These essential hormones might play an important role in the regulation of metabolic reprogramming of the new-born infant. However, HM hormone studies are sparse and heterogeneous in regard to the study design, sample collection, preparation and analysis methods. This review discussed the limitations of HM hormone analysis highlighting the gaps in pre-analytical and analytical stages. The methods used to quantify HM metabolic hormones (leptin, adiponectin, ghrelin, insulin, obestatin, resistin and apelin) can be classified as immunoassay, immunosensor and chromatography. Immunoassay methods (ELISA and RIA) have been predominantly used in the measurement of these HM hormones. The relative validity parameters of HM hormones analysis are often overlooked in publications, despite the complexity and differences of HM matrix when compared to that of plasma and urine. Therefore, appropriate reports of validation parameters of methodology and instrumentation are crucial for accurate measurements and therefore better understanding of the HM metabolic hormones and their influences on infant outcomes.

Evaluation of Appetite-Regulating Hormones ın Young Children with Autism Spectrum Disorder

This study aimed to investigate the role of leptin, ghrelin, neuropeptide Y, and nesfatin-1 in young children with autism spectrum disorder (ASD). A total of 44 children with ASD and 44 healthy controls aged 18-60 months were included. Plasma levels of hormones were measured using commercial enzyme-linked immunosorbent assay kits. Plasma leptin and ghrelin levels were significantly higher in the ASD group than in the control group. However, no significant difference for plasma neuropeptide Y and nesfatin-1 levels was detected between the groups. No relation was found between the severity of ASD symptoms, severity of eating problems, and plasma levels of hormones. Leptin and ghrelin may play a potential role in the pathogenesis of ASD.

Maternal BMI is positively associated with human milk fat: a systematic review and meta-regression analysis

BACKGROUND

Lack of robust estimates of human-milk nutrient composition and influential maternal factors, such as body composition, are barriers to informing nutrition policies and programs.

OBJECTIVE

The objective was to understand the relation between maternal BMI and human-milk energy, fat, and/or total protein.

METHODS

Four electronic databases (MEDLINE, Embase, CINAHL, and Web of Science) were searched. Outcomes assessed were human-milk energy (kcal/L), fat (g/L), and total protein (g/L) from mothers 1 to 6 mo postpartum. Studies with data on maternal BMI or weight and height that quantified human-milk energy, fat, or protein between 1 and 6 mo postpartum were eligible. Random-effects meta-regression weighted by the inverse of the study-level SE was completed for each of the 3 outcomes. The certainty of evidence for each outcome was assessed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach.

RESULTS

A total of 11,373 titles and abstracts were identified, and after full-text screening, 69 articles of 66 studies were included. Meta-regression results showed a positive association between maternal BMI and human-milk fat (β: 0.56 g/L; 95% CI: 0.034, 1.1; P = 0.04; I2 = 93.7%, n = 63 datapoints). There was no significant association between maternal BMI and human-milk energy (β: 3.9 kcal/L; 95% CI: -1.6, 9.5; P = 0.16, I2 = 93.3%, n = 40 datapoints) or total protein (β: 0.13 g/L; 95% CI: -0.16, 0.41; P = 0.37, I2 = 99.1%, n = 40 datapoints). The certainty of evidence for human-milk energy was low and the certainty of evidence for fat and total protein was very low.

CONCLUSIONS

Meta-regression analysis of available literature suggested an association between maternal BMI and human-milk fat between 1 and 6 mo postpartum. Future studies are needed to confirm the relation between maternal BMI; variation in human-milk energy, fat, and protein content; and the implications for child growth and development. This review is registered with International Prospective Register of Systematic Reviews (PROSPERO 2018 CRD42018098808) at https://www.crd.york.ac.uk/prospero/.

Effects of Holder Pasteurization on Immune Composition of Human Milk

Background: Human milk (HM) is the ideal food for newborn (NB) nutrition, it provides all macro and micronutrients for human growth and development and also contains bioactive compounds, which influence the development of the neonatal digestive and immune systems. The holder pasteurization process is essential to prevent NB infection from donated milk. Therefore, the aim of this study was to check whether or not holder pasteurization could impact the concentration of immune components in HM and the capacity to induce epithelial cell growth. Materials and Methods: The study was performed on raw and holder pasteurized (62.5°C/30 minutes) paired milk samples after submission to the freezing process in both phases. For cytokine and adipokine measurements, ELISA was performed on 40 individual samples of HM from single donors. For analyzes of epithelial cell growth, HuTu-80 cells were cultivated in Minimum Essential Eagle medium with 15% of raw or pasteurized milk, eight pairs of milk were used. Results: The results showed that no alteration was observed in the concentration of cytokine after milk holder pasteurization, and leptin concentration was reduced in holder pasteurized milk. The heat treatment also did not impact the capacity of breast milk to promote intestinal epithelial cell growth. Conclusions: The results showed that donated breast milk pasteurization has a small impact on the HM bioactive concentration compounds. This technique is important to avoid NB infection.

Circadian Variation in Human Milk Composition, a Systematic Review

Background: Breastfeeding is considered the most optimal mode of feeding for neonates and mothers. Human milk changes over the course of lactation in order to perfectly suit the infant’s nutritional and immunological needs. Its composition also varies throughout the day. Circadian fluctuations in some bioactive components are suggested to transfer chronobiological information from mother to child to assist the development of the biological clock. This review aims to give a complete overview of studies examining human milk components found to exhibit circadian variation in their concentration. Methods: We included studies assessing the concentration of a specific human milk component more than once in 24 h. Study characteristics, including gestational age, lactational stage, sampling strategy, analytical method, and outcome were extracted. Methodological quality was graded using a modified Newcastle-Ottawa Scale (NOS). Results: A total of 83 reports assessing the circadian variation in the concentration of 71 human milk components were included. Heterogeneity among studies was high. The methodological quality varied widely. Significant circadian variation is found in tryptophan, fats, triacylglycerol, cholesterol, iron, melatonin, cortisol, and cortisone. This may play a role in the child’s growth and development in terms of the biological clock.

A Systematic Review of Collection and Analysis of Human Milk for Macronutrient Composition

BACKGROUND

As human milk (HM) composition varies by time and across even a single feed, methods of sample collection can significantly affect the results of compositional analyses and complicate comparisons between studies.

OBJECTIVE

The aim was to compare the results obtained for HM macronutrient composition between studies utilizing different sampling methodologies. The results will be used as a basis to identify the most reliable HM sampling approach.

METHODS

EMBASE, MEDLINE/PubMed, Cochrane Library, Scopus, Web of Science, and ProQuest databases were searched for relevant articles. Observational and interventional studies were included, and at least 2 authors screened studies and undertook data extraction. Quality assessment was conducted using the Newcastle-Ottawa scale and previously published pragmatic score.

RESULTS

A total of 5301 publications were identified from our search, of which 101 studies were included (n = 5049 breastfeeding women). Methods used for HM collection were divided into 3 categories: collection of milk from all feeds over 24 h (32 studies, n = 1309 participants), collection at one time point (62 studies, n = 3432 participants), and "other methods" (7 studies, n = 308 participants). Fat and protein concentrations varied between collection methods within lactation stage, but there were no obvious differences in lactose concentrations. There was substantial variability between studies in other factors potentially impacting HM composition, including stage of lactation, gestational age, and analytical method, which complicated direct comparison of methods.

CONCLUSIONS

This review describes the first systematic evaluation of sampling methodologies used in studies reporting HM composition and highlights the wide range of collection methods applied in the field. This information provides an important basis for developing recommendations for best practices for HM collection for compositional analysis, which will ultimately allow combination of information from different studies and thus strengthen the body of evidence relating to contemporary HM composition. This trial was registered at PROSPERO as CRD42017072563, https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42017072563.

The impact of maternal obesity on human milk macronutrient composition: A systematic review and meta-analysis

Maternal obesity has been associated with changes in the macronutrient concentration of human milk (HM), which have the potential to promote weight gain and increase the long-term risk of obesity in the infant. This article aimed to provide a synthesis of studies evaluating the effects of maternal overweight and obesity on the concentrations of macronutrients in HM. EMBASE, MEDLINE/PubMed, Cochrane Library, Scopus, Web of Science, and ProQuest databases were searched for relevant articles. Two authors conducted screening, data extraction, and quality assessment independently. A total of 31 studies (5078 lactating women) were included in the qualitative synthesis and nine studies (872 lactating women) in the quantitative synthesis. Overall, maternal body mass index (BMI) and adiposity measurements were associated with higher HM fat and lactose concentrations at different stages of lactation, whereas protein concentration in HM did not appear to differ between overweight and/or obese and normal weight women. However, given the considerable variability in the results between studies and low quality of many of the included studies, further research is needed to establish the impact of maternal overweight and obesity on HM composition. This is particularly relevant considering potential implications of higher HM fat concentration on both growth and fat deposition during the first few months of infancy and long-term risk of obesity.

The short-term impact of dietary fat and sugar intake on breast milk composition: A clinical trial protocol

BACKGROUND

Breast milk is uniquely designed for the infant and contains the key nutrients and bioactive factors required to support optimal infant health and development. While previous studies have reported that maternal obesity can influence milk composition, whether this relationship is driven by maternal or dietary factors remains unclear.

AIM

The aim of this study is to assess the impact of test meals varying in fat and sugar content on post-prandial concentrations of macronutrients and metabolic hormones in the breast milk.

METHODS

This open label crossover study will include 25 lactating women. On the three days of the intervention, women will be randomized to receive a breakfast meal with a fat and sugar content consistent with the Australian Guide to Healthy Eating (9 g fat, 25 g of sugar) or a breakfast meal containing higher levels of fat (28 g fat, 18 g of sugar) or sugar (5 g fat, 56 g of sugar). All breakfast meals will be similar in composition (cereal, milk, yogurt, toast and spread) and matched for total energy content. This study will measure breast milk concentrations of metabolic hormones (leptin, insulin, adiponectin, ghrelin and glucagon-like peptide-1) and macronutrients in the following 12 hours.

RESULTS AND CONCLUSION

The results of this study will provide novel direct evidence of the impact of variations in dietary fat and sugar content to alter the macronutrient and/or metabolic hormone concentrations in breast milk. Data on the effect of maternal diet on milk composition is critical given the established importance of nutritional exposures in early infancy for an individual's life-long health outcomes.

Eating Disorders During Gestation: Implications for Mother's Health, Fetal Outcomes, and Epigenetic Changes

Introduction: Eating disorders (EDs) have increased globally in women of childbearing age, related to the concern for body shape promoted in industrialized countries. Pregnancy may exacerbate a previous ED or conversely may be a chance for improving eating patterns due to the mother's concern for the unborn baby. EDs may impact pregnancy evolution and increase the risk of adverse outcomes such as miscarriage, preterm delivery, poor fetal growth, or malformations, but the knowledge on this topic is limited. Methods: We performed a systematic review of studies on humans in order to clarify the mechanisms underpinning the adverse pregnancy outcomes in patients with EDs. Results: Although unfavorable fetal development could be multifactorial, maternal malnutrition, altered hormonal pathways, low pre-pregnancy body mass index, and poor gestational weight gain, combined with maternal psychopathology and stress, may impair the evolution of pregnancy. Environmental factors such as malnutrition or substance of abuse may also induce epigenetic changes in the fetal epigenome, which mark lifelong health concerns in offspring. Conclusions: The precocious detection of dysfunctional eating behaviors in the pre-pregnancy period and an early multidisciplinary approach comprised of nutritional support, psychotherapeutic techniques, and the use of psychotropics if necessary, would prevent lifelong morbidity for both mother and fetus. Further prospective studies with large sample sizes are needed in order to design a structured intervention during every stage of pregnancy and in the postpartum period.

Human milk as "chrononutrition": implications for child health and development

Human biology follows recurring daily rhythms that are governed by circadian cues in the environment. Here we show that human milk is a powerful form of "chrononutrition," formulated to communicate time-of-day information to infants. However, 85% of breastfed infants in the US consume some milk that does not come directly from the breast but is pumped and stored in advance of feeding. Expressed milk is not necessarily circadian-matched (e.g., an infant might drink breastmilk pumped in the evening on the following morning). Ingesting mistimed milk may disrupt infants' developing circadian rhythms, potentially contributing to sleep problems and decreased physiological attunement with their mothers and environments. Dysregulated circadian biology may compromise infant health and development. Despite wide-ranging public health implications, the timing of milk delivery has received little empirical study, and no major pediatric or public health organization has issued recommendations regarding the circadian-matching of milk. However, potential adverse developmental and health consequences could be ameliorated by simple, low-cost interventions to label and circadian-match stored milk. The current paper reviews evidence for human milk as chrononutrition and makes recommendations for future research, practice, and policy.

Human Milk Adiponectin and Leptin and Infant Body Composition over the First 12 Months of Lactation

Human milk (HM) adipokines may influence infant feeding patterns, appetite regulation, and body composition (BC). The associations between concentrations/calculated daily intakes (CDI) of HM adipokines in the first 12 months postpartum and maternal/term infant BC, and infant breastfeeding parameters were investigated. BC of breastfeeding dyads (n = 20) was measured at 2, 5, 9, and/or 12 months postpartum with ultrasound skinfolds (infants) and bioimpedance spectroscopy (infants/mothers). 24-h milk intake and feeding frequency were measured along with whole milk adiponectin and skim and whole milk leptin (SML and WML) and CDI were calculated. Statistical analysis used linear regression/mixed effects models; results were adjusted for multiple comparisons. Adipokine concentrations did not associate with infant BC. Higher CDI of adiponectin were associated with lower infant fat-free mass (FFM; p = 0.005) and FFM index (FFMI; p = 0.009) and higher fat mass (FM; p < 0.001), FM index (FMI; p < 0.001), and %FM (p < 0.001). Higher CDI of SML were associated with higher infant FM (p < 0.001), FMI (p < 0.001), and %FM (p = 0.002). At 12 months, higher CDI of WML were associated with larger increases in infant adiposity (2–12 month: FM, p = 0.0006; %FM, p = 0.0004); higher CDI of SML were associated with a larger decrease in FFMI (5–12 months: p = 0.0004). Intakes of HM adipokines differentially influence development of infant BC in the first year of life, which is a critical window of infant programming and may potentially influence risk of later disease via modulation of BC.

Could a remarkable decrease in leptin and insulin levels from colostrum to mature milk contribute to early growth catch-up of SGA infants?

BACKGROUND

Breast milk is known to contain many bioactive hormones and peptides, which can influence infant growth and development. In this context, the purpose of this study was to evaluate the influence of different clinical pregnancy conditions on hormone concentrations in colostrum and mature breast milk.

METHODS

An observational study was performed with mother-newborn pairs divided into five groups according to maternal clinical background: diabetes (12), hypertension (5), smoking (19), intrauterine growth restriction of unknown causes with small-for-gestational-age newborns at delivery (12), and controls (21). Socioeconomic data, anthropometric measurements and breast milk samples were collected between the first 24 and 48 h and 30 days postpartum. Leptin, adiponectin, and insulin levels in breast milk were measured by immunoassays.

RESULTS

A significant decrease in leptin (p = 0.050) and insulin (p = 0.012) levels from colostrum to mature breast milk in mothers of small-for-gestational-age infants was observed. Maternal body mass index was correlated with both leptin and insulin, but not with adiponectin. Insulin levels were negatively correlated to infant weight gain from birth to one month (p = 0.050). In addition, catch-up growth was verified for small-for-gestational-age infants throughout the first month of life.

CONCLUSIONS

This study suggests that a remarkable decrease in leptin and insulin levels in mature milk of mothers of small-for-gestational-age newborns may be involved in the rapid weight gain of these newborns. The physiological and external mechanisms by which these significant decreases and rapid weight gains occur in this group remain to be elucidated.

The relationship of human milk leptin and macronutrients with gastric emptying in term breastfed infants

BackgroundInfants breastfed on demand exhibit a variety of feeding patterns and self-regulate their nutrient intake, but factors influencing their gastric emptying (GE) are poorly understood. Despite research into appetite regulation properties of leptin, there is limited information about relationships between human milk leptin and infant GE.MethodsGastric volumes were calculated from ultrasound scans of infants' stomachs (n=20) taken before and after breastfeeding, and then every 12.5 min (median; range: 3-45 min) until the next feed. Skim milk leptin and macronutrient concentrations were measured and doses were calculated.ResultsThe leptin concentration was (mean±SD) 0.51±0.16 ng/ml; the leptin dose was 45.5±20.5 ng per feed. No relationships between both concentration and dose of leptin and time between the feeds (P=0.57; P=1, respectively) or residual stomach volumes before the subsequent feed (P=0.20; P=0.050) were found. Post-feed stomach volumes (GE rate) were not associated with leptin concentration (P=0.77) or dose (P=0.85).ConclusionGE in term breastfed infants was not associated with either skim milk leptin concentration or dose. Further investigation with inclusion of whole-milk leptin and other hormones that affect gastrointestinal activity is warranted.

Variation of Human Milk Glucocorticoids over 24 hour Period

Human milk (HM) contains a complex array of hormones, including members of the glucocorticoid family. The predominant glucocorticoids, cortisol and cortisone may influence the growth and behaviour of the breastfed infant. However, little is understood of the factors regulating the levels of these hormones within HM. The aim of the study was to examine HM cortisol and cortisone concentration, measured in samples collected at each feed during a 24 hour period. Twenty three exclusively breastfeeding mothers collected milk, prior to and after each breastfeeding session over 24 hour period at 3.2(1.60) months. HM cortisol and cortisone levels were measured using high pressure liquid chromatography mass spectroscopy. Cortisone was the predominant glucocorticoid (3.40 ng/ml), and cortisol was detected in all samples (1.62 ng/ml). A positive correlation was found between cortisone and cortisol (r = 0.61, y = 1.93 ± 0.24, p < 0.0001). Cortisol and cortisone concentrations were significantly higher in feeds in the morning (2.97 ng/ml and 4.88 ng/ml), compared to afternoon (1.20 ng/ml and 3.54 ng/ml), evening (0.69 ng/ml and 2.13 ng/ml) and night (1.59 and 3.27 ng/ml). No difference was found between glucocorticoids level of the milk expressed for collection either before or immediately after the breastfeed, or between milk collected from the left or right breast. This study shows that HM glucocorticoid concentrations exhibit a 24 hour pattern, with highest peak levels in the early morning, reflecting the circadian pattern as previously reported in plasma. Thus, HM glucocorticoid concentrations are likely to reflect those in the maternal circulation.

Effect of Human Milk Appetite Hormones, Macronutrients, and Infant Characteristics on Gastric Emptying and Breastfeeding Patterns of Term Fully Breastfed Infants

Human milk (HM) components influence infant feeding patterns and nutrient intake, yet it is unclear how they influence gastric emptying (GE), a key component of appetite regulation. This study analyzed GE of a single breastfeed, HM appetite hormones/macronutrients and demographics/anthropometrics/body composition of term fully breastfed infants (n = 41, 2 and/or 5 mo). Stomach volumes (SV) were calculated from pre-/post-feed ultrasound scans, then repeatedly until the next feed. Feed volume (FV) was measured by the test-weigh method. HM samples were analyzed for adiponectin, leptin, fat, lactose, total carbohydrate, lysozyme, and total/whey/casein protein. Linear regression/mixed effect models were used to determine associations between GE/feed variables and HM components/infant anthropometrics/adiposity. Higher FVs were associated with faster (−0.07 [−0.10, −0.03], p < 0.001) GE rate, higher post-feed SVs (0.82 [0.53, 1.12], p < 0.001), and longer GE times (0.24 [0.03, 0.46], p = 0.033). Higher whey protein concentration was associated with higher post-feed SVs (4.99 [0.84, 9.13], p = 0.023). Longer GE time was associated with higher adiponectin concentration (2.29 [0.92, 3.66], p = 0.002) and dose (0.02 [0.01, 0.03], p = 0.005), and lower casein:whey ratio (−65.89 [−107.13, −2.66], p = 0.003). FV and HM composition influence GE and breastfeeding patterns in term breastfed infants.

Leptin Levels Are Higher in Whole Compared to Skim Human Milk, Supporting a Cellular Contribution

Human milk (HM) contains a plethora of metabolic hormones, including leptin, which is thought to participate in the regulation of the appetite of the developing infant. Leptin in HM is derived from a combination of de novo mammary synthesis and transfer from the maternal serum. Moreover, leptin is partially lipophilic and is also present in HM cells. However, leptin has predominately been measured in skim HM, which contains neither fat nor cells. We optimised an enzyme-linked immunosorbent assay for leptin measurement in both whole and skim HM and compared leptin levels between both HM preparations collected from 61 lactating mothers. Whole HM leptin ranged from 0.2 to 1.47 ng/mL, whilst skim HM leptin ranged from 0.19 to 0.9 ng/mL. Whole HM contained, on average, 0.24 ± 0.01 ng/mL more leptin than skim HM (p < 0.0001, n = 287). No association was found between whole HM leptin and fat content (p = 0.17, n = 287), supporting a cellular contribution to HM leptin. No difference was found between pre- and post-feed samples (whole HM: p = 0.29, skim HM: p = 0.89). These findings highlight the importance of optimising HM leptin measurement and assaying it in whole HM to accurately examine the amount of leptin received by the infant during breastfeeding.

Alterations in human milk leptin and insulin are associated with early changes in the infant intestinal microbiome

BACKGROUND

Increased maternal body mass index (BMI) is a robust risk factor for later pediatric obesity. Accumulating evidence suggests that human milk (HM) may attenuate the transfer of obesity from mother to offspring, potentially through its effects on early development of the infant microbiome.

OBJECTIVES

Our objective was to identify early differences in intestinal microbiota in a cohort of breastfeeding infants born to obese compared with normal-weight (NW) mothers. We also investigated relations between HM hormones (leptin and insulin) and both the taxonomic and functional potentials of the infant microbiome.

DESIGN

Clinical data and infant stool and fasting HM samples were collected from 18 NW [prepregnancy BMI (in kg/m(2)) <24.0] and 12 obese (prepregnancy BMI >30.0) mothers and their exclusively breastfed infants at 2 wk postpartum. Infant body composition at 2 wk was determined by air-displacement plethysmography. Infant gastrointestinal microbes were estimated by using 16S amplicon and whole-genome sequencing. HM insulin and leptin were determined by ELISA; short-chain fatty acids (SCFAs) were measured in stool samples by using gas chromatography. Power was set at 80%.

RESULTS

Infants born to obese mothers were exposed to 2-fold higher HM insulin and leptin concentrations (P < 0.01) and showed a significant reduction in the early pioneering bacteria Gammaproteobacteria (P = 0.03) and exhibited a trend for elevated total SCFA content (P < 0.06). Independent of maternal prepregnancy BMI, HM insulin was positively associated with both microbial taxonomic diversity (P = 0.03) and Gammaproteobacteria (e.g., Enterobacteriaceae; P = 0.04) and was negatively associated with Lactobacillales (e.g., Streptococcaceae; P = 0.05). Metagenomic analysis showed that HM leptin and insulin were associated with decreased bacterial proteases, which are implicated in intestinal permeability, and reduced concentrations of pyruvate kinase, a biomarker of pediatric gastrointestinal inflammation.

CONCLUSION

Our results indicate that, although maternal obesity may adversely affect the early infant intestinal microbiome, HM insulin and leptin are independently associated with beneficial microbial metabolic pathways predicted to increase intestinal barrier function and reduce intestinal inflammation. This trial was registered at clinicaltrials.gov as NCT01693406.