Associations between human breast milk hormones and adipocytokines and infant growth and body composition in the first 6months of life

BackgroundMuch is to be learnt about human breast milk (HBM). ObjectivesThe purpose of this study is to extend our knowledge of HBM by investigating the role of maternal body mass index (BMI), sex and stage of lactation (month 1 vs. 6) on HBM insulin, glucose, leptin, IL-6 and TNF- and their associations with infant body composition. MethodsThirty-seven exclusively breastfeeding infants (n=37; 16f, 21o), and their mothers (19-47kgm(-2)) were studied at 1 and 6months of lactation. Infants had body composition measured (using dual-energy X-ray absorptiometry) and HBM collected. ResultsA significant interaction between maternal BMI and infant sex on insulin levels (p=0.0322) was observed such that insulin was 229% higher in obese mothers nursing female infants than in normal weight mothers nursing female infants and 179% higher than obese mothers nursing male infants. For leptin, a significant association with BMI category was observed (p<0.0001) such that overweight and obese mothers had 96.5% and 315.1% higher leptin levels than normal weight mothers, respectively. Leptin was also found to have a significant (p=0.0004) 33.7% decrease from months 1 to 6, controlling for BMI category and sex. A significant inverse relationship between month 1 leptin levels and infant length (p=0.0257), percent fat (p=0.0223), total fat mass (p=0.0226) and trunk fat mass (p=0.0111) at month 6 was also found. No associations or interactions were observed for glucose, TNF- or IL-6. ConclusionsThese data demonstrate that maternal BMI, infant sex and stage of lactation affect the compositional make-up of insulin and leptin.