Impact of maternal BMI and sampling strategy on the concentration of leptin, insulin, ghrelin and resistin in breast milk across a single feed: a longitudinal cohort study

Abstract

ObjectivesWe tested the hypothesis that there is a positive association between maternal body mass index (BMI) and the concentration of appetite-regulating hormones leptin, insulin, ghrelin and resistin in breast milk. We also aimed to describe the change in breast milk hormone concentration within each feed, and over time.SettingMothers were recruited from the postpartum ward at a university hospital in London. Breast milk samples were collected at the participants’ homes.ParticipantsWe recruited 120 healthy, primiparous, breastfeeding mothers, aged over 18 years. Mothers who smoked, had multiple births or had diabetes were excluded. Foremilk and hindmilk samples were collected from 105 women at 1 week postpartum and 92 women at 3 months postpartum.Primary and secondary outcome measuresWe recorded maternal and infant anthropometric measurements at each sample collection and measured hormone concentrations using a multiplex assay.ResultsThe concentration of leptin in foremilk correlated with maternal BMI at the time of sample collection, at 7 days (r=0.31, p=0.02) and 3 months postpartum (r=0.30, p=<0.00). Foremilk insulin correlated with maternal BMI at 3 months postpartum (r=0.22, p=0.04). Breast milk ghrelin and resistin were not correlated with maternal BMI. Ghrelin concentrations at 3 months postpartum were increased in foremilk compared with hindmilk (p=0.01). Concentrations of ghrelin were increased in hindmilk collected at 1 week postpartum compared with samples collected at 3 months postpartum (p=0.03). A trend towards decreased insulin concentrations in hindmilk was noted. Concentrations of leptin and resistin were not seen to alter over a feed.ConclusionsA positive correlation between maternal BMI and foremilk leptin concentration at both time points studied, and foremilk insulin at 3 months postpartum was observed. This may have implications for infant appetite regulation and obesity risk.

Associations between Maternal Body Composition and Appetite Hormones and Macronutrients in Human Milk

“…The temporary drop in protein concentration was consistent with differences described by Nommsen et al [42]. Whereas some studies have reported a decrease in concentrations of leptin [75] and adiponectin [30,33,36,66] (measured predominantly in skim HM), others found the opposite trend for adiponectin [11,35], no change [76] or significant fluctuations [11,21] for leptin. More research is required to clarify these relationships.…”

Relationship of Maternal Weight Status Before, During, and After Pregnancy with Breast Milk Hormone Concentrations

“…In line with this hypothesis, we and others have demonstrated positive associations between milk leptin levels and maternal BMI (11)(12)(13), but findings on the relationship of maternal BMI to milk insulin (11,12,14,15) and adiponectin (13,14,(16)(17)(18)(19) have been less consistent. One factor that may explain disparate findings is that while milk composition is known to change over the course of lactation, with a general finding of declines in milk peptides over lactation (20,21), the current literature is characterized by within-and between-study heterogeneity in the timing of milk sample collection for analysis (16,19,22).…”

“…Leptin is an appetite-regulating hormone produced in the adipose tissue (27) as well as epithelial cells of the mammary gland (28), and it has been found in much higher concentrations in human serum compared with breast milk (20) and in serum of women with obesity than those with normal weight (29). Milk leptin's positive association with maternal BMI (with a small number of exceptions) (19,30) has been well established (11,13,16,31). Our results confirmed this association in exclusively breastfeeding women and extended it by documenting that milk leptin concentration is responsive to dynamic aspects of weight change in pregnancy and lactation.…”

Associations of Maternal Weight Status Before, During, and After Pregnancy with Inflammatory Markers in Breast Milk

“…We did not examine CRP and IL‐6 concentrations separately in breast foremilk and hindmilk. A study examining breast milk appetite‐regulating hormones found differences in hormone concentrations and associations with maternal BMI depending on whether the measure was derived from foremilk or hindmilk ; therefore, it is possible that observed differences in breast milk inflammatory markers would depend on the stage of nursing. While the multiple measures of maternal weight status are a notable strength of this paper, they are not true measures of adiposity, but rather surrogate markers.…”