Fatty acid metabolism in hepatocytes isolated from rats adapted to high-fat diets containing long- or medium-chain triacylglycerols.
Fatty acid oxidation and synthesis were studied in isolated hepatocytes from adult rats adapted for 44 days on low-fat, high-carbohydrate (LF), diet or high-fat diets, composed of long-chain (LCT) or medium-chain (MCT) triacylglycerols. The rates of [1-14C]octanoate oxidation were almost similar in each group studied, whereas the oxidation of [1-14C]oleate was 50% lower in the LF group than in animals adapted to high-fat diets. The rates of oleate oxidation are inversely correlated with the rates of lipogenesis. However, it seems unlikely that [malonyl-CoA] itself represents the sole mechanism involved in the regulation of oleate oxidation during long-term LCT or MCT feeding, since: (1) despite a 3-fold higher concentration of malonyl-CoA in MCT-fed rats than in LCT-fed ones, the rates of oleate oxidation are similar; (2) when malonyl-CoA concentration is increased after stimulation of lipogenesis (by adding lactate + pyruvate) in MCT-fed rats, to a level comparable with that of the LF group, the rate of oleate oxidation remains 55% higher than that measured under similar conditions in the LF-fed rats; (3) in the LF group, the 90% decrease in malonyl-CoA concentration [by 5-(tetradecyloxy)-2-furoic acid] is not associated with a stimulation of oleate oxidation. By contrast, the sensitivity of carnitine palmitoyltransferase I (CPT I) to malonyl-CoA is markedly decreased in the LCT- and MCT-fed rats, by 90% and 70% respectively. The relevance of this decrease in the sensitivity of CPT I is discussed.
Pégorier
J P
JP
Centre de Recherches sur la Nutrition du CNRS, Meudon-Bellevue, France.
Duée
P H
PH
Herbin
C
C
Laulan
P Y
PY
Bladé
C
C
Peret
J
J
Girard
J
J
D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000037:antagonists & inhibitors; D004041:Dietary Fats / Q000494:pharmacology*; D005227:Fatty Acids / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008316:Malonyl Coenzyme A / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000494:pharmacology*
D004041:Dietary Fats; D005227:Fatty Acids; D008055:Lipids; D009829:Oleic Acids; D014280:Triglycerides; D019301:Oleic Acid; D008316:Malonyl Coenzyme A; D002334:Carnitine O-Palmitoyltransferase