Whole-body leucine and energy metabolism in adult women.
Whole-body leucine and energy metabolism were studied in seven women, in order to examine the relationship between changes in energy expenditure and rates of protein synthesis when moving from the fasted to the fed state. The diets provided 1.1 g protein/kg/d and calories (joules) to maintain body weight. Each subject received primed, continuous intravenous infusions of L-[1-13C]-leucine for a total of 9 h, and were studied fasted for the first 4 h. Small isotopically neutral meals were fed every half hour for the last 5 h. Energy expenditure by indirect calorimetry was simultaneously measured. Leucine flux, oxidation, utilization of leucine for protein synthesis, and energy expenditure increased with feeding. There were no statistically significant correlations between rates of protein synthesis calculated from leucine flux and energy expenditure in the fasted or the fed state. Significant correlations were mainly due to sex and feeding differences. These results agree with earlier published results. A maximal cost of protein synthesis, of 5.08 kcal (21.15 kJ)/g, was determined from changes in protein synthetic rates and energy expenditure in response to feeding.
Conway
J M
JM
Energy and Protein Nutrition Laboratory, Beltsville Human Nutrition Research Center, MD 20705.
Marable
N L
NL
Bodwell
C E
CE
D000328:Adult; D001835:Body Weight; D002153:Calorimetry, Indirect; D004435:Eating; D004734:Energy Metabolism; D005215:Fasting; D005260:Female; D006801:Humans; D007930:Leucine / Q000378:metabolism*; D008875:Middle Aged; D014176:Protein Biosynthesis
D007930:Leucine