Effects of feeding high-fat diets to rats: metabolism of erucic acid (C 22:1 n-9) in the perfused liver and secretion of metabolites to the perfusate.

The liver metabolism of erucic acid, 22:1 n-9, was studied in rat livers perfused with 14-14C-labelled erucic acid for 15 and 60 min, determining the distribution of radioactivity in the perfusate and in the lipids of the liver cell organelles. The rats were adapted to a high-fat diet containing either partially hydrogenated marine oil (PHMO) or palm oil (PO), both adjusted to a 10% content of linoleic acid. The results showed an efficient uptake and metabolism of erucic acid with the secretion to the perfusate medium of labelled free fatty acids other than erucic acid, labelled phospholipids as well as water soluble oxidation products. Only minor amounts of secreted labelled triglycerides were found within 60 min of perfusion. In the liver, labelled lipids accumulated in the endoplasmic reticulum, after 15 min mainly as free fatty acids, after 60 min as triglycerides. The esterification pathway, including the erucic acid given as well as chain-shortened fatty acids, seemed to be preferred under the experimental conditions and with adequate linoleic acid in the diet. A chain shortening of erucic acid probably took place in both peroxisomes and mitochondria shown by the presence of labelled 18:1 and 20:1 in the organelle-bound phospholipids. A chain shortening was found in both dietary groups, and is assumed to be an affect of the adaptation to a high-fat diet rather than an effect of dietary very long chain monoenoic fatty acids. Somewhat higher levels were found in the PHMO group, but the difference in the dietary fat was not a major factor in the liver lipid adaptation.