The selective mobilization of fatty acids : a general metabolic feature of adipose tissue not based on its composition or location . Raclot, Thierry, Eliane Mioskowsky, Andr[acute]e C. Bach, and Ren[acute]e Groscolas. Centre d'Ecologie et Physiologie Energ[acute]etiques, CNRS, associ[acute]e [grave]a l'Universit[acute]e Louis Pasteur, 23 rue Becquerel, 67087 Strasbourg, France
APStracts 2:0178R, 1995.
This study extends our earlier work (Raclot, T. and R. Groscolas, J. Lipid Res. 34: 1515-1526, 1993) which showed that, under norepinephrine-stimulated lipolysis, fatty acids of rat retroperitoneal fat cells are selectively mobilized. The present study examines whether this selective mobilization of fatty acids i) is based on their proportions in adipose tissue, ii) is a metabolic feature common to all adipose tissues, and/or iii) depends on the lipolysis-stimulating agent. Rat fat cells with two markedly different fatty acid compositions were isolated from four white adipose tissues and treated with three lipolytic agents. Fatty acid composition of in vitro released free fattyacids (FFA) was compared to that of fat cell triacylglycerols (TAG), the ratio % FFA / % TAG being defined as the relative mobilization rate (RMR). The RMR of individual fatty acids was related to their molecular structure. It increased exponentially with unsaturation for a given chain length, and decreased with increasing chain length for a given unsaturation. The selectivity of fatty acid mobilization was similar regardless the fatty acid composition of adipose tissue, the tissue location and the lipolytic agent used. Under conditions of stimulated lipolysis, the selectivity of fatty acid mobilization is therefore a general metabolic feature of adipose tissue. Fatty acids with 16-20 carbon atoms and 4-5 double bonds had the highest RMR (from 1.4 to more than 5) whereas fatty acids with 20-22 carbon atoms and 0-1 double bond had the lowest RMR (from 0.3 to 0.7). The other fatty acids had a RMR close to unity. Accordingly, they were schematically classified into highly, weakly, and moderately mobilizable fatty acids. 

Received 30 January 1995; accepted in final form 7 June 1995.
APS Manuscript Number R77-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.