Cyclic fatty acid monomers from heated oil modify the activities of lipid synthesizing and oxidizing enzymes in rat liver.

Cyclic fatty acid monomers purified from a heated linseed oil were given for 2 wk to adult rats as triacylglycerol at two dose levels, i.e., 0.1 and 1 g/100 g diet, to determine their effect on some aspects of lipid metabolism. Indirect evidence of a peroxisome proliferator-like effect was observed, as determined by an elevation of some characteristic enzyme activities, such as peroxisomal acyl-CoA oxidase, and the microsomal omega- but also (omega-1)-laurate hydroxylase (CYP4A1 and CYP2E1, respectively). The dietary cyclic fatty acids induced a coordinated regulation between the activities of the lipogenic enzymes studied (Delta9-desaturase, phosphatidate phosphohydrolase) and peroxisomal oxidation, but not with mitochondrial beta-oxidation. The dose-dependent decrease of Delta9-desaturase activity (P < 0.05) with cyclic fatty acid monomer intake was accompanied by a similar decrease of the monounsaturated fatty acid level in liver. The increase in the gamma-linolenic acid level also suggested an increase in Delta6-desaturase activity with cyclic fatty acid intake (P < 0.05). In addition, our results strongly suggested that the altered liver levels of eicosapentaenoic and arachidonic acids were due to the peroxisomal retroconversion process in rats fed cyclic acids. Finally, an effect of these cyclic compounds on the carbohydrate metabolism cannot be disregarded because they decreased liver glycogen concentration. We conclude that cyclic fatty acid monomers affect different aspects of lipid metabolism, including a phenotypic peroxisome proliferator response. This provides the ground for further studies investigating the biochemical pathways that underlie the nutritional effect of such molecules.