A new correction factor for use in tracer estimations of plasma
fatty acid oxidation.
Sidossis, L. S., A. R. Coggan, A. Gastaldelli, and R. R. Wolfe.
Metabolism Unit, Shriners Burns Institute, and Departments of
Anesthesiology, Surgery, and Biochemistry, University of Texas
Medical Branch, Galveston, TX 77550
APStracts 2:0102E, 1995.
The purpose of this study was to acquire a new correction factor for
use in tracer estimations of plasma fatty acid oxidation that would
fully account for label fixation during the infusion of fatty acid
tracers. Thus, volunteers were infused with [1-13C]-labeled fatty
acids and [1-14C] acetate in the basal state, during
hyperinsulinemia-hyperglycemia (clamp), and during one hour of
cycling exercise. The fractional recovery of acetate label (i.e., the
acetate correction factor) was 0.56+/-0.02, 0.50+/-0.03, and 0.80+/
-0.03, in the basal state, during the clamp, and exercise,
respectively. Isotopically determined plasma fatty acid oxidation
rates ([mu]mol. kg-1. min-1) were 1.7+/-0.2, 0.8+/-0.2, 6.4+/-0.5 (no
correction), 2.1+/-0.2, 1.0+/-0.2, 6.7+/-0.5 (bicarbonate
correction), and 3.1+/-0.2, 1.5+/-0.2, 8.2+/-0.4 (acetate
correction). We conclude that the use of the acetate correction
factor, in the place of the bicarbonate correction factor, should
improve the accuracy of isotopic measurements of plasma fatty acid
oxidation, because it accounts for label fixation that might occur at
any step between the entrance of labeled acetyl-CoA into the TCA
cycle until the recovery of label in breath CO2.
Received 23 February 1995; accepted in final form 28 April 1995.
APS Manuscript Number E89-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.