Effect of intravenous amino acids on protein kinetics in preterm infants.
OBJECTIVE
To summarize recent findings of the effects of intravenous amino acids on protein kinetics in low-birth-weight infants and to describe the potential cellular mechanism for these observations.


RESULTS
Amino acids administered intravenously for 3-5 h in infants have been shown to suppress whole-body proteolysis. Recent data in low-birth-weight infants show that an increase in the dose of amino acid caused a suppression of proteolysis, and a decrease in the rate of glutamine and urea synthesis. These responses returned to basal state, however, when the amino acid infusion continued for 20-24 h. Supplementation with glutamine sustained the suppression of proteolysis after 3-5 days. Plasma insulin concentration did not change during the amino acid infusion. Data from studies in adults and from in vitro studies suggest that the amino acids impact protein breakdown and synthesis via the mammalian target of rapamycin pathway, stimulating initiation of translation and suppressing autophagic proteolysis.


CONCLUSIONS
Intravenous amino acids, by increasing extracellular amino acid concentration, transiently stimulate protein synthesis and suppress protein breakdown. These effects return to basal state when the amino acid infusions are prolonged. The mechanism of this adaptive response remains to be determined.
Kalhan
Satish C
SC
Department of Gastroenterology, Cleveland Clinic Foundation, Lerner Research Institute, Cleveland, Ohio 44195, USA. sck@case.edu
Edmison
John M
JM
D000596:Amino Acids / Q000494:pharmacology*; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D007227:Infant Nutritional Physiological Phenomena; D007230:Infant, Low Birth Weight / Q000254:growth & development / Q000378:metabolism*; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development / Q000378:metabolism*; D007262:Infusions, Intravenous; D010649:Phenylalanine / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects*; D011506:Proteins / Q000378:metabolism*
D000596:Amino Acids; D011506:Proteins; D005973:Glutamine; D010649:Phenylalanine