title: Glutamine and leucine nitrogen kinetics and their relation to urea nitrogen in newborn infants.
abstract: Glutamine kinetics and its relation to transamination of leucine and urea synthesis were quantified in 16 appropriate-for-gestational-age infants, four small-for-gestational-age infants, and seven infants of diabetic mothers. Kinetics were measured between 4 and 5 h after the last feed (fasting) and in response to formula feeding using [5-(15)N]glutamine, [1-(13)C,(15)N]leucine, [(2)H(5)]phenylalanine, and [(15)N(2)]urea tracers. Leucine nitrogen and glutamine kinetics during fasting were significantly higher than those reported in adults. De novo synthesis accounted for approximately 85% of glutamine turnover. In response to formula feeding, a significant increase (P = 0.04) in leucine nitrogen turnover was observed, whereas a significant decrease (P = 0.002) in glutamine and urea rate of appearance was seen. The rate of appearance of leucine nitrogen was positively correlated (r(2) = 0.59, P = 0.001) with glutamine turnover. Glutamine flux was negatively correlated (r(2) = 0.39, P = 0.02) with the rate of urea synthesis. These data suggest that, in the human newborn, glutamine turnover is related to a high anaplerotic flux into the tricarboxylic acid cycle as a consequence of a high rate of protein turnover. The negative relationship between glutamine turnover and the irreversible oxidation of protein (urea synthesis) suggests an important role of glutamine as a nitrogen source for other synthetic processes and accretion of body proteins.
authors.affiliation: Department of Pediatrics, Robert Schwartz M.D. Center for Metabolism and Nutrition, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44109-1998, USA.
authors.forename: Prabhu S
authors.initials: PS
authors.lastname: Parimi
authors.forename: Srisatish
authors.initials: S
authors.lastname: Devapatla
authors.forename: Lourdes
authors.initials: L
authors.lastname: Gruca
authors.forename: Alicia M
authors.initials: AM
authors.lastname: O'Brien
authors.forename: Richard W
authors.initials: RW
authors.lastname: Hanson
authors.forename: Satish C
authors.initials: SC
authors.lastname: Kalhan
mesh_terms: D001806:Blood Urea Nitrogen; D002247:Carbon Isotopes; D003903:Deuterium; D005260:Female; D005973:Glutamine / Q000097:blood*; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D007700:Kinetics; D007930:Leucine / Q000097:blood*; D009584:Nitrogen / Q000097:blood*; D009587:Nitrogen Isotopes; D010649:Phenylalanine; D011247:Pregnancy; D011254:Pregnancy in Diabetics; D014508:Urea
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D005973:Glutamine; D010649:Phenylalanine; D014508:Urea; D003903:Deuterium; D007930:Leucine; D009584:Nitrogen