POSTPRANDIAL DECREASE IN PLASMA UNESTERIFIED FATTY-ACIDS DURING N-3 FATTY-ACID FEEDING IS NOT CAUSED BY ACCUMULATION OF FATTY-ACIDS IN ADIPOSE-TISSUE

Dietary supplementation of very long-chain n-3 fatty acids to rats red uces postprandial plasma concentrations of triacylglycerol, unesterifi ed fatty acids and glycerol after long-term feeding by unknown mechani sms [Rustan et al., J. Lipid Res. 34 (1993) 1299-1309]. In the present study we examine the role of adipose tissues in metabolism of fatty a cids. Postprandial plasma concentrations of triacylglycerol, unesterif ied fatty acids and glycerol were reduced by 75%, 50% and 30%, respect ively, during 49 days of feeding high-fat diets containing n - 3 fatty acids (6.5% n - 3 fatty acid concentrate, 13% lard) as compared to la rd (19.5% lard). These differences were observed already after two day s of feeding. Plasma concentration of unesterified very long-chain n - 3 fatty acids increased to 50 mu M in n - 3 fatty acid-supplemented r ats, whereas these fatty acids were undetectable in lard-fed animals. The n - 3 fatty acid-enriched diet limited cell volumes of perirenal a nd epididymal adipocytes by 40% and 30%, respectively, after 49 days, as compared to lard feeding. This reduction in cell volume was not due to reduced synthesis of glycerolipids in epididymal adipocytes. Acute incubation of perirenal and epididymal adipocytes with oleic acid or eicosapentaenoic acid, caused similar increase in synthesis of triacyl glycerol. Dietary supplementation with n - 3 fatty acids decreased bas al and total lipolysis (isoprenalin-stimulated) in perirenal adipocyte s. Basal lipolysis in epididymal adipocytes was reduced by n - 3 fatty acids only after 49 days. n - 3 fatty acids increased total lipolysis in mesenteric and subcutaneous fat cells compared to adipocytes deriv ed from lard-fed animals, whereas basal lipolysis was unchanged. These results suggest that the reduced postprandial plasma concentration of unesterified fatty acids after n - 3 fatty acid-supplementation is no t caused by accumulation of fatty acids in adipose tissue. The reduced trophic growth of adipocytes might be due to decreased supply of unes terified fatty acids for triacylglycerol storage. (C) 1998 Elsevier Sc ience B.V.