In vivo study of the biosynthesis of long chain fatty acids (lcfa)
using deuterated water (d2o)1.
Ajie, Henry O., Michael J. Connor, W. N. Paul Lee, Sara Bassilian, E.
Anne Bergner, and Lauri O. Byerley.
Research and Education Institute, Harbor - UCLA Medical Center,
RB1, 1124 W. Carson St., Torrance, California 90502. Tel (310) 222
-1860, FAX (310) 533-0627, Division of Dermatology, UCLA School of
Medicine, Center for Health Sciences, Los Angeles, California 90024,
and Veterans Administration, West Los Angeles Medical Center
APStracts 2:0051E, 1995.
To determine the contributions of pre-existing fatty acid, de novo
synthesis and chain elongation in long chain fatty acids synthesis,
the synthesis of long chain fatty acids, palmitate (c16:0), stearate
(c18:0), arachidate (c20:0), behenate (c22:0) and lignocerate (c24:0)
in the epidermis, liver and spinal cord was determined using
deuterated water (D2O) and mass isotopomer distribution analysis
(MIDA) in two rodent species (hairless mice and Sprague Dawley rats).
Animals were given 4% D2O for either 5 days or 8 weeks in their
drinking water. Blood was withdrawn at the end of these times for the
determination of deuterium enrichment, and the animals killed to
isolate the various tissues for lipid extraction for the
determination of the mass isotopomer distributions. The mass
isotopomer distributions in LCFA were incompatible with synthesis
from a single pool of primer. The synthesis of palmitate, stearate,
arachidate, behenate and lignocerate followed the expected
biochemical pathways for the synthesis of LCFA. On average three
deuterium atoms were incorporated for every addition of an acetyl
unit. The isotopomer distribution resulting from both chain
elongation and de novo synthesis can be described by the linear
combination of two binomial distributions. The proportions of pre
-existing, chain elongation and de novo synthesized fatty acids as a
percentage of the total fatty acids were determined using multiple
linear regression analysis. Fractional synthesis was found to vary
depending on the tissue type and the fatty acid ranging from 47 to
87%. A substantial fraction (24 to 40%) of the newly synthesized
molecules were derived from chain elongation of unlabeled (recycled)
palmitate.
Received 26 July 1994; accepted in final form 7 March 1995.
APS Manuscript Number E291-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 March 1995.