The 24-h kinetics of leucine oxidation in healthy adults receiving a generous leucine intake via three discrete meals

• Published in: The American journal of clinical nutrition Vol. 62; no. 3; pp. 579 - 590
• Main Authors: el-Khoury, AE, Sánchez, M, Fukagawa, NK, Gleason, RE, Tsay, RH, Young, VR
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.1995; American Society for Clinical Nutrition, Inc
• Subjects: Adult; Carbon Dioxide - metabolism; Circadian Rhythm; Diet; Eating; Feeding Behavior; Humans; Kinetics; Leucine - administration & dosage; Leucine - blood; Leucine - metabolism; Nitrogen - metabolism; Nitrogen - urine; Osmolar Concentration; Oxidation-Reduction; Oxygen Consumption; Proteins - metabolism; Reference Values
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/62.3.579

The significance of meal size and frequency for the 24-h leucine tracer-balance technique was examined. Continuous measurements of leucine oxidation throughout a 24-h d were performed in six healthy, young adults who were given a weight-maintaining diet (188 kJ.kg-1.d-1; 1 g protein.kg-1.d-1) for 6 d followed by primed, continuous intravenous infusions of L-[1-13C]leucine and [15N-15N]urea. The 24-h study was started at 1800 on day 6 and three equal discrete meals were given at 2000, 0600, and 1200. Leucine oxidation was assessed from plasma [13C]alpha-ketoisocaproate enrichment and 13CO2 excretion. The mean (+/- SD) leucine oxidation after each meal (over 6 h) was not significantly different (P < 0.5) among the three discrete meals: 20.0 +/- 3.9, 20.2 +/- 1.9, and 20.3 +/- 2.4 mg.kg-1.d-1 for the meals given at 2000, 0600, and 1200, respectively. Twenty-four-hour leucine oxidation was 75.0 +/- 7.8 mg.kg-1.d-1 for a leucine dietary intake of 80 mg.kg-1.d-1 (and approximately 9.7 mg tracer.kg-1.d-1). The 24-h pattern in leucine oxidation was paralleled by plasma leucine concentrations. Further, leucine oxidation and urea excretion predicted relatively similar values for 24-h protein oxidation. These data are compared with results from our similar previous studies using a multiple-small-meal feeding protocol.