New insights into the methodological issues of the indicator amino acid oxidation method in preterm neonates

F. de Groof, L.S. Huang, J.W.R. Twisk, G.J. Voortman, W. Joemai, C.H. Hau, H. Schierbeek, C. Chen, Y. Huang, J.B. van Goudoever

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Abstract

Background: We determined the effect of adaptation to the study diet on oxidation of the indicator amino acid and the required tracer washout time in preterms. Methods: Subjects received a study diet for 6 d that entailed a 50% reduction in leucine. Tracer studies using enterally infused [ 13 C]bicarbonate and [1-13 C]phenylalanine were performed on days 1, 2, 4, and 6. Breath samples containing 13 CO 2 were collected during steady state and measured by infrared spectrometric analysis, and the fraction of 13 CO 2 recovery from 13 C oxidation (F 13 CO 2) was calculated. Results: Preterm infants (n = 11, birth weight 1.9 ± 0.1 kg, gestational age 32.6 ± 1.5 wk) received 166 mg/kg/d of leucine. Baseline enrichment changed significantly at day 1 of the study diet. F 13 CO 2 did not change significantly between days 2 and 4 but was significantly lower at day 6. The tracer washout time was determined to be 7.5 h using a biphasic regression analysis. Conclusion: One day of adaptation to a new diet is necessary to adapt to the 13 C enrichment of the study formula before starting infant requirement studies. Adaptation for a period of 5 d results in a protein-sparing response. The minimal time between two studies within the same subject is 7.5 h. © 2013 International Pediatric Research Foundation, Inc.
Original languageEnglish
Pages (from-to)679-684
JournalPediatric Research
Volume73
Issue number5
DOIs
Publication statusPublished - 2013

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    de Groof, F., Huang, L. S., Twisk, J. W. R., Voortman, G. J., Joemai, W., Hau, C. H., Schierbeek, H., Chen, C., Huang, Y., & van Goudoever, J. B. (2013). New insights into the methodological issues of the indicator amino acid oxidation method in preterm neonates. Pediatric Research, 73(5), 679-684. https://doi.org/10.1038/pr.2013.31