Glycine, leucine, and phenylalanine flux in low-birth-weight infants during parenteral and enteral feeding

• Published in: The American journal of clinical nutrition Vol. 55; no. 5; pp. 971 - 975
• Main Authors: Wykes, LJ, Ball, RO, Menendez, CE, Ginther, DM, Pencharz, PB
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.05.1992; American Society for Clinical Nutrition
• Subjects: ALIMENTACION; ALIMENTACION PARENTERAL; ALIMENTATION; ALIMENTATION ENTERALE; Amino Acids - administration & dosage; Amino Acids - metabolism; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; BEBES; Biological and medical sciences; Dietary Proteins - administration & dosage; Emergency and intensive care: neonates and children. Prematurity. Sudden death; Energy Intake; ENFANT EN BAS AGE; Enteral Nutrition; FENILALANINA; FISIOLOGIA DE LA NUTRICION; flux; GLICINA; glycine; GLYCINE (ACIDE AMINE); Glycine - administration & dosage; Glycine - metabolism; Humans; Infant, Low Birth Weight - metabolism; Infant, Newborn; Intensive care medicine; LEUCINA; LEUCINE; Leucine - administration & dosage; Leucine - metabolism; Low birth weight; Medical sciences; neonate; Parenteral Nutrition; PESO AL NACIMIENTO; PHENYLALANINE; Phenylalanine - administration & dosage; Phenylalanine - metabolism; PHYSIOLOGIE DE LA NUTRITION; POIDS A LA NAISSANCE; premature; protein metabolism; leucine; premature; phenylalanine; parenteral nutrition; glycine; protein metabolism; Low birth weight; flux; neonate; Human; Premature; Phenylalanine; Leucine; Glycine; Metabolism; Enteral administration; Parenteral administration; Feeding; Very low birthweight; Proteins; Newborn diseases; Newborn; Nitrogen balance; Aminoacid
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/55.5.971

Kinetics of three amino acids with different sites and characteristics of metabolic regulation were studied in low-birth-weight infants during enteral and parenteral feeding regimens typical of clinical practice. Primed constant infusions of [15N]glycine, L-[l-13C]leucine, and L-[l-13C]phenylalanine were administered simultaneously by the same route as the feeding, with isotope enrichment measured in urine over 12 h. The effect of feeding regimen was specific to each amino acid (x̄ ± SD): glycine flux was lower during parenteral feeding (470 ± 15 vs 561 ± 69 µmol · kg−1 · h−1, P < 0.05), leucine flux was unaffected (360 ± 77 vs 388 ± 78 µmol · kg−1 · h−1), and phenylalanine flux was higher (106 ± 29 vs 56 ± 6 µmol · kg−1 · h−1, P < 0.01). Kinetics were influenced by the interaction of several factors, including amino acid intake and routes of feeding and tracer administration. Glycine was most affected by route of feeding and phenylalanine was most affected by intake whereas leucine was little affected. Estimates of whole-body protein turnover calculated from leucine and phenylalanine were different; thus calculations of protein turnover from kinetics of a single amino acid should be interpreted with caution.