Alanine flux in obese and healthy humans as evaluated by 15N- and 2H3-labeled alanines.
Estimates of plasma alanine flux as measured in humans using L-[15N]-alanine or L-[3,3,3-2H3]alanine were compared by simultaneous intravenous infusion of both tracers. Plasma isotope enrichments were measured by chemical ionization gas chromatography-mass spectrometry. In 16 obese women before and during a hypocaloric diet and in 4 normal men in the postabsorptive and fed states, the fluxes were highly correlated (r2 = 0.93) although plasma alanine flux with the 2H tracer was two to three times greater than that obtained with [15N]alanine. The fluxes decreased with the hypocaloric diet in obese subjects and increased during the fed state in healthy adults. Thus, although the estimates of alanine flux differed according to the tracer used, both appear to give equivalent information about changes in alanine kinetics induced by the nutritional conditions examined.
Department of Applied Biological Sciences, Massachusetts Institute of Technology, Cambridge.
L J
LJ
Hoffer
R D
RD
Yang
D E
DE
Matthews
B R
BR
Bistrian
D M
DM
Bier
V R
VR
Young
D000328:Adult; D000409:Alanine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000596:Amino Acids / Q000097:blood; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007262:Infusions, Intravenous; D007408:Intestinal Absorption; D008297:Male; D009587:Nitrogen Isotopes; D009765:Obesity / Q000097:blood*; D014316:Tritium
D000596:Amino Acids; D009587:Nitrogen Isotopes; D014316:Tritium; D000409:Alanine