Evidence for peroxisomal retroconversion of adrenic acid (22:4(n-6)) and docosahexaenoic acids (22:6(n-3)) in isolated liver cells.
The intracellular localization of the oxidation of [2-14C]adrenic acid (22:4(n-6)) and [1-14C]docosahexaenoic acid (22:6(n-3)) was studied in isolated liver cells. The oxidation of 22:4(n-6) was 2-3-times more rapid than the oxidation of 22:6(n-3), [1-14C]arachidonic acid (20:4(n-6)) or [1-14C]oleic acid (18:1). (+)-Decanoylcarnitine and lactate, both known to inhibit mitochondrial beta-oxidation, reduced the oxidation of 18:1 distinctly more efficiently than with 22:4(n-6) and 22:6(n-3). In liver cells from rats fed a diet containing partially hydrogenated fish oil, the oxidation of 22:6(n-6) and 22:6(n-3) was increased by 30-40% compared with cells from rats fed a standard pellet diet. With 18:1 as substrate, the amount of fatty acid oxidized was very similar in cells from animals fed standard pellets or partially hydrogenated fish oil. Shortened fatty acids were not produced from [5,6,8,9,11,12,14,15-3H]arachidonic acid. In hepatocytes from rats starved and refed 20% fructose, a large fraction of 14C from 22:4 was recovered in 14C-labelled C14-C18 fatty acids. Oxidation of 22:4 thus caused a high specific activity of the extramitochondrial pool of acetyl-CoA. The results suggest that 22:4(n-6) and to some extent 22:6(n-3) are oxidized by peroxisomal beta-oxidation and by this are retroconverted to arachidonic acid and eicosapentaenoic acid.
D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives / Q000494:pharmacology; D004041:Dietary Fats / Q000008:administration & dosage; D004281:Docosahexaenoic Acids; D004883:Erucic Acids / Q000378:metabolism*; D005215:Fasting; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007773:Lactates / Q000494:pharmacology; D019344:Lactic Acid; D008099:Liver / Q000166:cytology* / Q000378:metabolism; D008297:Male; D008830:Microbodies / Q000378:metabolism*; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D004041:Dietary Fats; D004883:Erucic Acids; D005231:Fatty Acids, Unsaturated; D007773:Lactates; D009829:Oleic Acids; C002893:decanoylcarnitine; C011395:adrenic acid; D004281:Docosahexaenoic Acids; D019301:Oleic Acid; D019344:Lactic Acid; D002331:Carnitine