Recent advances in our understanding of protein and amino acid metabolism in the human fetus.
OBJECTIVE
Premature infants often suffer from suboptimal outcome, at least partially due to suboptimal nutrition. Gaining insight into human fetal amino acid metabolism might ultimately lead to an improved nutritional strategy for prematurely born infants. Our aim was, therefore, to discuss recent findings with regard to human fetal amino acid metabolism.


RESULTS
Human fetal protein and amino acid metabolism can be studied in vivo using stable isotope techniques. To date, however, only a few studies employing these techniques have been performed. For one, it was shown in vivo that essential amino acids are transported at different rates across the human placenta. In addition, tyrosine appears not to be a conditionally essential amino acid in the fetus at term, as phenylalanine is hydroxylated into tyrosine at considerable rates. Furthermore, albumin is synthesized at very high rates at two-thirds of gestation; higher than prematurely born infants do at a neonatal intensive care unit. This could indicate that postnatal nutrition of very immature infants can be improved.


CONCLUSIONS
Although technically challenging, more studies regarding human fetal amino acid metabolism should be performed. Premature infants could then benefit from this knowledge from new nutritional strategies.
Van den Akker
Chris Hp
CH
Erasmus MC - Sophia Children's Hospital, Division of Neonatology, Department of Pediatrics, Rotterdam, The Netherlands.
Van Goudoever
Johannes B
JB
D000418:Albumins / Q000096:biosynthesis; D000596:Amino Acids / Q000378:metabolism*; D001692:Biological Transport; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007234:Infant, Premature; D008431:Maternal-Fetal Exchange; D010649:Phenylalanine / Q000378:metabolism; D010920:Placenta; D011247:Pregnancy; D039401:Prenatal Nutritional Physiological Phenomena; D011506:Proteins / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
D000418:Albumins; D000596:Amino Acids; D011506:Proteins; D014443:Tyrosine; D010649:Phenylalanine