Metabolism of trans fatty acids by hepatocytes

The present work was undertaken to study the metabolism of fatty acids with trans double bonds by rat hepatocytes. In liver mitochondria, elaidoyl‐CoA was a poorer substrate for carnitine palmitoyltransferase I (CPT‐I) than oleoyl‐CoA. Likewise, incubation, of hepatocytes with oleic acid produced a more pronounced stimulation of CPT‐I than incubation with trans fatty acids. This was not due to a differential effect of cis and trans fatty acids on acetyl‐CoA carboxylase (ACC) activity and malonyl‐CoA levels. Elaidic acid was metabolized by hepatocytes at a higher rate than oleic acid. Surprisingly, compared to oleic acid, elaidic acid was a better substrate for mitochondrial and, especially, peroxisomal oxidation, but a poorer substrate for cellular and very low density lipoprotein triacylglycerol synthesis. Results thus show that trans fatty acids are preferentially oxidized by hepatic peroxisomes, and that the ACC/malonyl‐CoA/CPT‐I system for coordinate control of fatty acid metabolism is not responsible for the distinct hepatic utilization of cis and trans fatty acids.