Tryptophan metabolic profile in term and preterm breast milk: implications for health
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Published Version
Published Version
Date
2018
Authors
O'Rourke, Louise
Clarke, Gerard
Nolan, Aoife
Watkins, Claire
Dinan, Timothy G.
Stanton, Catherine
Ross, R. Paul
Ryan, Cornelius Anthony
Journal Title
Journal ISSN
Volume Title
Publisher
Cambridge University Press on behalf of the Nutrition Society
Published Version
Abstract
Breast milk is the only source of the essential amino acid tryptophan (TRP) in breast-fed infants. Low levels of TRP could have implications for infant neurodevelopment. The objectives of the present study were to compare the relationship of TRP and its neuroactive pathway metabolites kynurenine (Kyn) and kynurenic acid (KynA) in preterm and term expressed breast milk (EBM) in the first 14 d following birth, and the relationship of TRP metabolism to maternal stress and immune status. A total of twenty-four mothers were recruited from Cork University Maternity Hospital: twelve term (>38 weeks) and twelve preterm (<35 weeks). EBM samples were collected on days 7 and 14. Free TRP, Kyn and KynA were measured using HPLC, total TRP using MS, cytokines using the Meso Scale Discovery (MSD) assay system, and cortisol using a cortisol ELISA kit. Although total TRP was higher in preterm EBM in comparison with term EBM (P < 0·05), free TRP levels were lower (P < 0·05). Kyn, KynA and the Kyn:TRP ratio increased significantly in term EBM from day 7 to day 14 (P < 0·05), but not in preterm EBM. TNF-α, IL-6 and IL-8 were higher in day 7 preterm and term EBM in comparison with day 14. There were no significant differences between term and preterm EBM cortisol levels. Increased availability of total TRP, lower levels of free TRP and alterations in the temporal dynamics of TRP metabolism in preterm compared with term EBM, coupled with higher EBM inflammatory markers on day 7, may have implications for the neurological development of exclusively breast-fed preterm infants.
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Keywords
Human milk , Tryptophan , Kynurenine , Kynurenic acid , Cytokines , Cortisol
Citation
O'Rourke, L., Clarke, G., Nolan, A., Watkins, C., Dinan, T. G., Stanton, C., Ross, R. P. and Ryan, C. A. (2018) 'Tryptophan metabolic profile in term and preterm breast milk: implications for health', Journal of Nutritional Science, 7, e13 (9pp). doi: 10.1017/jns.2017.69