TY - JOUR

T1 - Moderate exercise at energy balance does not affect 24-h leucine oxidation or nitrogen retention in healthy men

AU - El-Khoury, Antoine E

AU - Forslund, Anders

AU - Olsson, Roger

AU - Branth, Stefan

AU - Sjödin, Anders Mikael

AU - Andersson, Agneta

AU - Atkinson, Alan

AU - Selvaraj, Ambalini

AU - Hambraeus, Leif

AU - Young, Vernon R

PY - 1997

Y1 - 1997

N2 - Short-term metabolic experiments have revealed that physical exercise increases the oxidation of leucine, which has been interpreted to indicate an increased requirement for dietary protein in physically active subjects. Because it may be inaccurate to extrapolate measurements of amino acid oxidation made over a few hours to the entire day, we have carried out a continuous 24-h intraveneus [1-13C]leucine/[15N]urea tracer study in eight healthy adult men. Their diet supplied 1 g protein ·kg-1·day-1, and exercise (mean maximal O2 consumption 46%) was for 90 min during the 12- h fast and 12-h fed periods of the day. Subjects were adapted to the diet and exercise regimen for 6 days. Then, on day 7, they were dressed in the University of Uppsala energy metabolic unit's direct calorimeter suit, were connected to an open-hood indirect calorimeter, and received the tracers. Exercise increased leucine oxidation by ~50 and 30% over preexercise rates for fast and fed periods, respectively. This increase amounted to ~4-7% of daily leucine oxidation. Subjects remained in body leucine equilibrium (balance -4.6 ± 10.5 mg·kg-1· day-1; -3.6 ± 8.3% of intake; P = not significant from zero balance). Therefore, moderate exercise did not cause a significant deterioration in leucine homeostasis at a protein intake of 1 g·kg-1·day-1. These findings underscore the importance of carrying out precise, continuous, 24-h measurements of whole body leucine kinetics; this model should be of value in studies concerning the quantitative interactions among physical exercise, energy/protein metabolism, and diet in humans.

AB - Short-term metabolic experiments have revealed that physical exercise increases the oxidation of leucine, which has been interpreted to indicate an increased requirement for dietary protein in physically active subjects. Because it may be inaccurate to extrapolate measurements of amino acid oxidation made over a few hours to the entire day, we have carried out a continuous 24-h intraveneus [1-13C]leucine/[15N]urea tracer study in eight healthy adult men. Their diet supplied 1 g protein ·kg-1·day-1, and exercise (mean maximal O2 consumption 46%) was for 90 min during the 12- h fast and 12-h fed periods of the day. Subjects were adapted to the diet and exercise regimen for 6 days. Then, on day 7, they were dressed in the University of Uppsala energy metabolic unit's direct calorimeter suit, were connected to an open-hood indirect calorimeter, and received the tracers. Exercise increased leucine oxidation by ~50 and 30% over preexercise rates for fast and fed periods, respectively. This increase amounted to ~4-7% of daily leucine oxidation. Subjects remained in body leucine equilibrium (balance -4.6 ± 10.5 mg·kg-1· day-1; -3.6 ± 8.3% of intake; P = not significant from zero balance). Therefore, moderate exercise did not cause a significant deterioration in leucine homeostasis at a protein intake of 1 g·kg-1·day-1. These findings underscore the importance of carrying out precise, continuous, 24-h measurements of whole body leucine kinetics; this model should be of value in studies concerning the quantitative interactions among physical exercise, energy/protein metabolism, and diet in humans.

KW - Calorimetry

KW - Fasting and feeding

KW - Urea kinetics

U2 - 10.1152/ajpendo.1997.273.2.E394

DO - 10.1152/ajpendo.1997.273.2.E394

M3 - Journal article

C2 - 9277394

AN - SCOPUS:0030805243

VL - 273

SP - E394-E407

JO - A J P: Endocrinology and Metabolism (Online)

JF - A J P: Endocrinology and Metabolism (Online)

SN - 1522-1555

IS - 2

ER -