Inhibition of hepatic fatty acid oxidation by bezafibrate and bezafibroyl CoA.

The acute effect of the hypolipidemic agent bezafibrate on fatty acid oxidation was studied in rat hepatocytes and mitochondria. Bezafibrate caused a concentration-related inhibition of oleate oxidation in liver cells. In mitochondria bezafibrate inhibited the oxidation of palmitoyl CoA but had no effect on palmitoylcarnitine oxidation, suggesting the site of inhibition was the formation of the carnitine derivative. Bezafibrate and bezafibroyl CoA inhibited the overt carnitine palmitoyltransferase (I) in rat liver mitochondria with comparable potency but with distinct kinetics. The inhibition caused by bezafibrate was not prevented by omission of Mg++-ATP from the assay mixture, indicating activation of bezafibrate to bezafibroyl CoA was not required for inhibition. The data demonstrate that bezafibrate, like several other peroxisome proliferating agents, inhibits mitochondrial fatty acid oxidation in rat liver. The inhibition may be relevant to the mechanism of peroxisome proliferation.