A comparison of mass isotopomer dilution methods used to compute
production of vldl fatty acids in vivo in human subjects.
Chinkes;, David L., Asle Aarsland, Judah Rosenblatt, and Robert R.
Wolfe.
Metabolism Unit, Shriners Burns Institute; and Departments of
Surgery and Anesthesiology, The University of Texas Medical Branch,
Galveston, Texas 77555
APStracts 3:0076E, 1996.
The recent development of mass isotopomer distribution methods
represents an important new tool for quantifying synthetic rates.
These methods allow precursor enrichment to be determined indirectly
from the enrichment of the product, thus sidestepping the often
difficult problem of measuring the precursor enrichment. Two
different methods have been described to compute synthetic rates by
this general approach by Hellerstein's and Kelleher's labs and
variations of these basic approaches have also been presented by Lee
and by ourselves. A comparison between the different methods has
never been reported. In this paper we take a specific application,
calculation of the fractional rate of incorporation of acetylCoA into
VLDL bound palmitate, and compare the results obtained from all of
the mass isotopomer methods using the same data set obtained in vivo
in human subjects. We found that it is critical that the measured
background isotopomer distribution of palmitate is used rather than
the theoretical background isotopomer distribution. We also found
that the different methods give comparable precursor enrichments and
comparable fractional synthesis rates, provided that the enrichments
in Kelleher's method are properly weighted. Thus the choice of method
to use is a matter of personal preference.
Received 5 July 1994; accepted in final form 20 March 1996.
APS Manuscript Number E248-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 23 April 96