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
SN - 1522-1555
VL - 273
SP - E394-E407
JO - A J P: Endocrinology and Metabolism (Online)
JF - A J P: Endocrinology and Metabolism (Online)
IS - 2
ER -