Infant intakes of human milk branched chain amino acids are negatively associated with infant growth and influenced by maternal body mass index

Authors: SABEN, JESSICA - Arkansas Children'S Nutrition Research Center (ACNC); SIMS, CLARK - Arkansas Children'S Nutrition Research Center (ACNC); PACK, LINDSAY - University Arkansas For Medical Sciences (UAMS); LAN, RENNY - Arkansas Children'S Nutrition Research Center (ACNC); BORSHEIM, ELISABET - Arkansas Children'S Nutrition Research Center (ACNC); ANDRES, ALINE - Arkansas Children'S Nutrition Research Center (ACNC)

Submitted to: Pediatric Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2021
Publication Date: 12/16/2021
Citation: Saben, J.L., Sims, C.R., Pack, L., Lan, R., Borsheim, E., Andres, A. 2021. Infant intakes of human milk branched chain amino acids are negatively associated with infant growth and influenced by maternal body mass index. Pediatric Obesity. https://doi.org/10.1111/ijpo.12876.
DOI: https://doi.org/10.1111/ijpo.12876

Interpretive Summary: Amino acids are the building blocks for proteins and many are essential for the growth, development, and overall health of humans. Some essential amino acids that have branched (branched-chain amino acid: BCAA) or cyclic structures (aromatic amino acid (AAA)) are hypothesized to influence early-life obesity risk when they are consumed in excess. Importantly, there have been recent reports that these amino acids are increased in human milk from mothers with obesity, which may impact the risk of obesity for their infants. However, the relationship between increased consumption of human milk BCAAs and AAAs by infants born to women with normal weight verses those with obesity and infant growth has not been studied. The objective of this study was to assess the amounts of amino acids in human milk from women with normal weight verses those with obesity and determine the amount infants born to these women consume over the first 6 months of life. We predicted that infants fed by women with obesity would consume greater amounts of human milk BCAAs and AAAs, which would be positively associated with growth and obesity risk. Our data indicate that women with obesity produce human milk that has higher amounts of BCAAs and AAAs than women with normal weight and that increasing body mass index (measured at the beginning of pregnancy) predicts greater consumption of human milk BCAAs and AAAs in infants across the first 6 months of life. However, contrary to our hypothesis we found that increased consumption of human milk BCAAs predicted a decrease in infant growth, suggesting that elevated BCAAs in human milk produced by women with obesity does not result in an increased obesity risk for their infants.

Technical Abstract: Branched-chain amino acids (AA) (BCAAs: leucine, isoleucine, and valine) and aromatic AA (AAAs: phenylalanine and tyrosine) are hypothesized to influence early-life obesity risk and are increased in human milk (HM) from mothers with obesity (OB). A knowledge gap exists regarding how HM free AA concentrations impact child growth. To assess HM free AA concentrations and infant intakes of HM AAs from women with OB compared to those with normal weight (NW). We hypothesized that infants fed by women with OB would consume greater amounts of HM BCAAs and AAAs, which would be positively associated with growth. HM samples were collected at 0.5 (0.5M, n=151), 2 (2M, n=129), and 6 (6M, n=93) months postpartum from mothers with NW (body mass index (BMI) =18.5 – 24.9 kg/m2) and OB (BMI>30 kg/m2). HM free AA were quantified at each timepoint via mass spectrometry. Infant HM intake normalized by body weight, anthropometrics and body composition were assessed at each timepoint. Linear mixed-effect models (LMEM) examined the relationships between maternal BMI and HM AA composition, as well as HM AA intake and infant growth over the first 6Ms postpartum. Models were adjusted for maternal race, breastfeeding exclusivity, infant sex and infant age. Isoleucine, leucine, and AAA concentrations were higher (p<0.05) at all timepoints in HM from women with OB compared to those with NW. LMEM showed negative associations between maternal BMI and infant intakes of HM asparagine, cystine, and histidine and positive associations with isoleucine, leucine, and AAAs intakes across timepoints. Normalized infant intakes of HM isoleucine (B=-0.083), leucine (B=-0.045), and proline (B=-0.024) were negative predictors of infant weight-for-age z-scores over the first 6M (p<0.05). Maternal obesity is associated with increased BCAA and AAA infant intake over the first 6M of life. Consumption of BCAA and AAA negatively predicted infant growth.