Abstract
Human fetal metabolism is largely unexplored. Understanding how a healthy fetus achieves its fast growth rates could eventually play a pivotal role in improving future nutritional strategies for premature infants. To quantify specific fetal amino acid kinetics, eight healthy pregnant women received before elective cesarean section at term, continuous stable isotope infusions of the essential amino acids [1-13C,15N]leucine, [U-13C5]valine, and [1-13C]methionine. Umbilical blood was collected after birth and analyzed for enrichments and concentrations using mass spectrometry techniques. Fetuses showed considerable leucine, valine, and methionine uptake and high turnover rates. α-Ketoisocaproate, but not α-ketoisovalerate (the leucine and valine ketoacids, respectively), was transported at net rate from the fetus to the placenta. Especially, leucine and valine data suggested high oxidation rates, up to half of net uptake. This was supported by relatively low α-ketoisocaproate reamination rates to leucine. Our data suggest high protein breakdown and synthesis rates, comparable with, or even slightly higher than in premature infants. The relatively large uptakes of total leucine and valine carbon also suggest high fetal oxidation rates of these essential branched chain amino acids.
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Abbreviations
- αKIC:
-
α-ketoisocaproate
- αKIV:
-
α-ketoisovalerate
- GCMS:
-
gas chromatography mass spectrometer
- MPE:
-
mole percent excess
- MTBSTFA:
-
N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide
- PCF:
-
propylchloroformate
- Q C :
-
carbon leucine flux
- Q N :
-
nitrogen leucine flux
- TLC:
-
total leucine carbon
- TVC:
-
total valine carbon.
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Acknowledgements
We thank all the participating women. We also thank Willemijn Corpeleijn, Frans te Braake, and all the personnel from the Obstetrics and Anesthesiological departments who were very helpful in the collection of material and provision of facilities.
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Supported by the Sophia Children's Hospital Fund (SSWO, institutional grant no. 459) and the Nutricia Research Foundation (independent charity, grant no. 2006-10).
The authors report no conflicts of interest.
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van den Akker, C., Schierbeek, H., Minderman, G. et al. Amino Acid Metabolism in the Human Fetus at Term: Leucine, Valine, and Methionine Kinetics. Pediatr Res 70, 566–571 (2011). https://doi.org/10.1203/PDR.0b013e31823214d1
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DOI: https://doi.org/10.1203/PDR.0b013e31823214d1
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