The majority of dietary linoleate in growing rats is beta-oxidized or stored in visceral fat.
On a quantitative, whole-body basis, little is known about the amount of linoleate that is converted to arachidonate or the partitioning of linoleate and its longer-chain derivatives among lean and fat tissues. The aim of the present study was to examine linoleate balance and organ partitioning in rats consuming a low but adequate level of linoleate. Weanling male Sprague-Dawley rats were given free access to a semipurified diet containing 2.3% of energy as linoleate. Food intake, fecal output and body weight gain were measured for 26 d. Whole-body fatty acid balance analysis showed that 75.5% of the linoleate consumed disappeared (apparently by beta-oxidation), 18.7% was accumulated as linoleate, 3.0% was converted to (n-6) longer-chain polyunsaturated fatty acids, and 1.2% was excreted in the feces Visceral fat contained 64% of the accumulated linoleate, and 23% was in lean tissues. Comparable values for alpha-linolenate were as follows: disappearance (84.9%), accumulation (10.9%), excretion in the feces (2.2%), and conversion to (n-3) longer-chain polyunsaturated fatty acids (1.4%). Visceral fat contained 67% of the accumulated alpha-linolenate, and 23% was in lean tissues. Visceral fat also accumulated 26% of newly synthesized (n-6) longer-chain polyunsaturated fatty acids and 31% of the (n-3) longer-chain polyunsaturated fatty acids. Thus, only 6.5% of dietary linoleate consumed at a low but adequate level for rats appeared in lean tissues as linoleate or its fatty acid metabolites; the rest was beta-oxidized or stored in fat, mostly in visceral fat. These results lead us to speculate whether losses through beta-oxidation contribute to the recommended intake for linoleate in growing rats.
Cunnane
S C
SC
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada.
Anderson
M J
MJ
D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004032:Diet; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008041:Linoleic Acids / Q000378:metabolism* / Q000493:pharmacokinetics*; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids