Amino Acids

, Volume 45, Issue 6, pp 1365–1372

Human baby hair amino acid natural abundance 15N-isotope values are not related to the 15N-isotope values of amino acids in mother’s breast milk protein

  • Katarzyna M. Romek
  • Maxime Julien
  • Marine Frasquet-Darrieux
  • Illa Tea
  • Ingrid Antheaume
  • Régis Hankard
  • Richard J. Robins
Original Article

DOI: 10.1007/s00726-013-1597-7

Cite this article as:
Romek, K.M., Julien, M., Frasquet-Darrieux, M. et al. Amino Acids (2013) 45: 1365. doi:10.1007/s00726-013-1597-7

Abstract

Since exclusively breast-suckled infants obtain their nutrient only from their mother’s milk, it might be anticipated that a correlation will exist between the 15N/14N isotope ratios of amino acids of protein of young infants and those supplied by their mother. The work presented here aimed to determine whether amino nitrogen transfer from human milk to infant hair protein synthesized within the first month of life conserves the maternal isotopic signature or whether post-ingestion fractionation dominates the nitrogen isotope spectrum. The study was conducted at 1 month post-birth on 100 mother–infant pairs. Isotope ratios 15N/14N and 13C/12C were measured using isotope ratio measurement by Mass Spectrometry (irm-MS) for whole maternal milk, and infant hair and 15N/14N ratios were also measured by GC-irm-MS for the N-pivaloyl-O-isopropyl esters of amino acids obtained from the hydrolysis of milk and hair proteins. The δ15N and δ13C (‰) were found to be significantly higher in infant hair than in breast milk (δ15N, P < 0.001; δ13C, P < 0.001). Furthermore, the δ15N (‰) of individual amino acids in infant hair was also significantly higher than that in maternal milk (P < 0.001). By calculation, the observed shift in isotope ratio was shown not to be accounted for by the amino acid composition of hair and milk proteins, indicating that it is not simply due to differences in the composition in the proteins present. Rather, it would appear that each pool—mother and infant—turns over independently, and that fractionation in infant N-metabolism even in the first month of life dominates over the nutrient N-content.

Keywords

Natural abundance 15N/14N ratio Milk protein Hair protein Isotope ratio measurement by mass spectrometry Isotope fractionation 

Abbreviations

EA

Elemental analyser

GA

Gestational age

irm

Isotope ratio measurement

MS

Mass spectrometry

Nleu

Norleucine

Vs

‘Area All’ output of the mass spectrometer

Xle

Mixture of leucine and isoleucine

Supplementary material

726_2013_1597_MOESM1_ESM.docx (94 kb)
Supplementary material 1 (DOCX 94 kb)

Copyright information

© Springer-Verlag Wien 2013

Authors and Affiliations

  • Katarzyna M. Romek
    • 1
    • 3
  • Maxime Julien
    • 1
  • Marine Frasquet-Darrieux
    • 2
  • Illa Tea
    • 1
  • Ingrid Antheaume
    • 1
  • Régis Hankard
    • 2
  • Richard J. Robins
    • 1
  1. 1.Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAMUniversity of Nantes-CNRS UMR6230NantesFrance
  2. 2.Pédiatrie Multidisciplinaire Nutrition de l’EnfantCentre Hospitalier Universitaire de PoitiersPoitiersFrance
  3. 3.Laboratory for Isotope Effects Studies, Department of Chemistry, Institute of Applied Radiation ChemistryŁodź Technical UniversityLodzPoland

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