HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 289/6/E981    most recent 00132.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Parimi, P. S. Articles by Kalhan, S. C. Search for Related Content PubMed PubMed Citation Articles by Parimi, P. S. Articles by Kalhan, S. C.

Metabolism of threonine in newborn infants

Schwartz Center for Metabolism and Nutrition; and Department of Pediatrics, Case Western Reserve University School of Medicine at MetroHealth Medical Center, Cleveland, Ohio

Submitted 23 March 2005 ; accepted in final form 14 July 2005

Threonine kinetics, threonine oxidative pathway, and the relationship between threonine and whole body protein turnover were quantified in 10 healthy term infants during the first 48 h after birth. The kinetic data were obtained 6 h after the last feed (fasting) and in response to formula feeding, using [U-¹³C₄,¹⁵N]threonine, [²H₅]phenylalanine, and [¹⁵N]glycine tracers. The rate of carbon dioxide production (CO₂) and ¹³C enrichment of the expired CO₂ were measured to quantify the rate of oxidation of threonine. The rate of appearance (R_a) of threonine (136 ± 37 µmol·kg^–1·h^–1) was higher in newborn infants than that reported in adults. Formula feeding resulted in a significant decrease in threonine R_a (P < 0.05). A significant positive correlation was seen between phenylalanine R_a and threonine R_a, both during fasting and after formula feeding (r² = 0.65). In contrast to a 1:1 ratio of threonine and phenylalanine in mixed muscle protein, threonine R_a relative to phenylalanine R_a was 2.2 ± 0.4. The fractional rate of threonine flux oxidized was 20% during fasting and 26% (P < 0.05) in response to nutrient administration. There was a significant correlation between plasma threonine concentration and threonine oxidation (r² = 0.75). No measurable incorporation of threonine in plasma glycine was seen. These data suggest that threonine is exclusively degraded by the glycine-independent serine/threonine dehydratase pathway. A higher flux of threonine relative to phenylalanine indicates higher turnover of threonine enriched proteins.

glycine; phenylalanine; stable isotopes; threonine oxidation

This article has been cited by other articles:

				R. H. Clark, D. H. Chace, A. R. Spitzer, and for the Pediatrix Amino Acid Study Group Effects of Two Different Doses of Amino Acid Supplementation on Growth and Blood Amino Acid Levels in Premature Neonates Admitted to the Neonatal Intensive Care Unit: A Randomized, Controlled Trial Pediatrics, December 1, 2007; 120(6): 1286 - 1296. [Abstract] [Full Text] [PDF]

				S. R. van der Schoor, D. L Wattimena, J. Huijmans, A. Vermes, and J. B van Goudoever The gut takes nearly all: threonine kinetics in infants Am. J. Clinical Nutrition, October 1, 2007; 86(4): 1132 - 1138. [Abstract] [Full Text] [PDF]