Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells.
The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.
Christensen
E
E
Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway.
Hagve
T A
TA
Grønn
M
M
Christophersen
B O
BO
D000818:Animals; D002210:Caprylates / Q000378:metabolism; D002331:Carnitine / Q000031:analogs & derivatives / Q000494:pharmacology; D004951:Esterification; D005215:Fasting; D005227:Fatty Acids / Q000378:metabolism*; D005502:Food; D005632:Fructose / Q000494:pharmacology; D007850:Lauric Acids / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D010084:Oxidation-Reduction; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013229:Stearic Acids / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
D002210:Caprylates; D005227:Fatty Acids; D007850:Lauric Acids; D009227:Myristic Acids; D009829:Oleic Acids; D010169:Palmitic Acids; D013229:Stearic Acids; D014280:Triglycerides; D019814:Myristic Acid; C030358:lauric acid; C002893:decanoylcarnitine; D019301:Oleic Acid; D019308:Palmitic Acid; D005632:Fructose; C031183:stearic acid; C031492:octanoic acid; D002331:Carnitine