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We have previously hypothesized that increased muscle oxidation of leucine in starvation is an adaptive response to fuel deficiency in this tissue. To investigate this hypothesis further, we have measured the rates of oxidation, turnover, and plasma clearance of [1-14C]leucine in six obese subjects at rest and during 2 h of mild leg exercise. This experimental design was based on the fact that exercise has the greatest impact on energy expenditure in muscle, the principal site for leucine oxidation. Exercise produced a fourfold increase in oxygen consumption. The rate of alpha-decarboxylation of leucine was increased twofold by leg exercise, whereas there were modest decreases (13%) in the rates of turnover and plasma clearance of this amino acid. The plasma concentrations of lactate and alanine increased twofold during exercise, but plasma concentrations of leucine and other amino acids, glucose, beta-hydroxybutyrate, and insulin remained unaltered. Our data suggest that during exercise oxidation of leucine as an energy source increases, whereas the utilization of this amino acid as a substrate for protein synthesis decreases.
S A Hagg, and
E L Morse, and
S A Adibi
August 1985,
The American journal of physiology,
S A Hagg, and
E L Morse, and
S A Adibi
May 2000,
The Journal of physiology,
S A Hagg, and
E L Morse, and
S A Adibi
November 1993,
The American journal of physiology,
S A Hagg, and
E L Morse, and
S A Adibi
February 1985,
Biochemical medicine,
S A Hagg, and
E L Morse, and
S A Adibi
June 1982,
Metabolism: clinical and experimental,
S A Hagg, and
E L Morse, and
S A Adibi
December 1975,
FEBS letters,
S A Hagg, and
E L Morse, and
S A Adibi
October 1985,
Journal of applied physiology (Bethesda, Md. : 1985),
S A Hagg, and
E L Morse, and
S A Adibi
January 1992,
Acta diabetologica,
S A Hagg, and
E L Morse, and
S A Adibi
January 2009,
Archives of animal nutrition,
S A Hagg, and
E L Morse, and
S A Adibi
January 1974,
Pflugers Archiv : European journal of physiology,
