QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal 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 Google Scholar Google Scholar Articles by Floc'h, N. L. Articles by Sève, B. Search for Related Content PubMed PubMed Citation Articles by Floc'h, N. L. Articles by Sève, B.

In Vivo Threonine Oxidation Rate Is Dependent on Threonine Dietary Supply in Growing Pigs Fed Low to Adequate Levels^1,2,

Nathalie Le Floc'h^*,3, Christiane Obled and Bernard Sève^*

^* Station de Recherches Porcines, INRA, 35590 Saint Gilles Laboratoire d'Etudes du Métabolisme Azoté, INRA Theix, 63122 Ceyrat, France

Threonine oxidation was examined in 12 growing pigs fed a well-balanced control diet or a threonine-deficient diet supplemented (Glu) or not (LT) with glutamic acid during constant infusion of L-[1-¹³C]-threonine, [1-¹⁴C]glycine and [1-¹⁴C]-ketobutyrate for 10 h. During these infusions, liver glycine enrichment was significantly lower than plasma enrichment. Moreover, the pancreas to plasma glycine enrichment ratio was higher than the liver to plasma ratio (70–89%), showing that an important part of glycine de novo synthesis in pancreas occurred through the threonine dehydrogenase (TDG) pathway. These results imply that calculation of threonine oxidation into glycine should be made with the assumption of both hepatic and extrahepatic oxidation. Plateau values of plasma threonine, glycine and -ketobutyrate enrichments and specific radio activities allowed estimations of threonine oxidation through the TDG and threonine dehydratase (TDH) pathways. Threonine oxidation into glycine was 12.16 ± 2.06, 2.89 ± 0.61 and 2.13 ± 0.44 µmol/(kg·h), respectively, in pigs fed the control, LT and Glu diets, and threonine oxidation into -ketobutyrate was 1.80 ± 0.31, 0.88 ± 0.02 and 0.55 ± 0.06 µmol/(kg·h) for the control, LT and Glu groups, respectively. Total threonine oxidation rates were 75 and 81% lower in the LT and Glu groups, respectively, than in the control group. Liver TDG and TDH activity measured in vitro were not affected by either the level of dietary threonine supply the addition of glutamic acid. On the basis of plasma data, it may be concluded that the addition of glutamic acid to a threonine-deficient diet had no significant effect on threonine oxidation but did reduce the rate of threonine release from protein breakdown. Oxidation appears to be related to plasma threonine concentration.

KEY WORDS: • pigs • threonine • oxidation • tracer • metabolism

¹ Presented in part in the second world conference on Stable Isotopes in Nutritional and Metabolic Research, July 8–9, 1994, Rotterdam, The Netherlands [Le Floc'h, N. & Sève, B. (1994) Quantification of threonine oxidation in growing pigs fed a threonine-deficient diet: effect of glutamic acid addition (abs.)].

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence should be addressed.

Manuscript received 21 November 1994. Revision accepted 20 April 1995.

This article has been cited by other articles:

				X. Wang, S. Qiao, Y. Yin, L. Yue, Z. Wang, and G. Wu A Deficiency or Excess of Dietary Threonine Reduces Protein Synthesis in Jejunum and Skeletal Muscle of Young Pigs J. Nutr., June 1, 2007; 137(6): 1442 - 1446. [Abstract] [Full Text] [PDF]