Branched-chain amino acid interactions with reference to amino acid requirements in adult men: leucine metabolism at different valine and isoleucine intakes.
Recent estimates of the leucine requirement of adult men based on 13C-tracer studies are substantially higher than those proposed by FAO/WHO/UNU (1985). To explore whether leucine oxidation and requirements are affected by the dietary amount of valine. 11 healthy young adult men received, in random order, for 5 d, one of four L-amino acid diets providing 40 or 15 mg leucine.kg-1.d-1 together with variable amounts mg.kg-1.d-1 of valine and isoleucine in the following combinations (Val:Ile): 80:62 and 20:62 (six subjects; phase 1); 20:62 and 20:20 (five subjects, phase 2). On the morning of day 6, a continuous intravenous infusion of L-[1-13C]leucine was given for 7-8 h; the subject was in the fasting state for the initial 2.5 or 3 h and in the fed state for the remainder of the time. Also, [2H3]leucine was added to the diet. Leucine oxidation was similar for all diet groups in the fasted state. During the fed state, leucine oxidation was not affected by the Val:Ile pattern. Thus, changes in the pattern of branched-chain amino acid intake within a physiological range do not affect isotopically derived estimates of the leucine requirement.
Pelletier
V
V
Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge.
Marks
L
L
Wagner
D A
DA
Hoerr
R A
RA
Young
V R
VR
D000328:Adult; D002247:Carbon Isotopes; D006801:Humans; D007532:Isoleucine / Q000008:administration & dosage* / Q000097:blood; D007651:Keto Acids / Q000097:blood; D007700:Kinetics; D007930:Leucine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D008297:Male; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D014633:Valine / Q000008:administration & dosage* / Q000097:blood
D002247:Carbon Isotopes; D007651:Keto Acids; D007532:Isoleucine; C013082:alpha-ketoisocaproic acid; D007930:Leucine; D014633:Valine