Leucine metabolism during fasting and exercise.

Journal Article (Journal Article)

Whole body leucine kinetics were examined in seven healthy young men while in a 14-h postabsorptive state (PAS) and after a 3.5-day fast (FS). Subjects received a primed constant intravenous infusion of L-[1-13C]leucine while resting for 3 h and then while exercising on a cycle ergometer at 45% maximal O2 uptake to exhaustion. Blood samples drawn during isotopic steady state were analyzed for 13C enrichment of leucine and alpha-ketoisocaproic acid, and expired gas samples were analyzed for 13CO2. Resting leucine flux was higher in the FS, and there was a slight increase in leucine oxidation. During exercise, leucine flux did not differ between PAS and FS but leucine oxidation rose markedly. In the FS, leucine oxidation was 25 +/- 7 (SD) mumol.kg-1.h-1 at rest and rose to 75 +/- 21 mumol.kg-1.h-1 during exercise; in the PAS, oxidation was 20 +/- 5 mumol.kg-1.h-1 at rest and 52 +/- 17 mumol.kg-1.h-1 during exercise. These data indicate that the high rate of leucine oxidation previously found during exercise was increased further by a 3.5-day fast.

Full Text

Duke Authors

Cited Authors

  • Knapik, J; Meredith, C; Jones, B; Fielding, R; Young, V; Evans, W

Published Date

  • January 1, 1991

Published In

Volume / Issue

  • 70 / 1

Start / End Page

  • 43 - 47

PubMed ID

  • 2010401

International Standard Serial Number (ISSN)

  • 8750-7587

Digital Object Identifier (DOI)

  • 10.1152/jappl.1991.70.1.43


  • eng

Conference Location

  • United States