Fatty acid-dependent ethanol metabolism

Abstract

Rates of ethanol oxidation by perfused livers from fasted female rats were decreased from 82 ± 8 to 11 ± 7 μmol/g/hr by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase. The subsequent addition of fatty acids of various chain lengths in the presence of 4-methylpyrazole increased rates of ethanol uptake markedly. Palmitate (1 mM) increased rates of ethanol oxidation to 95 ± 8 μmol/g/hr, while octanoate and oleate increased rates to 58 ± 11 and 68 ± 15 μmol/g/hr, respectively. Hexanoate, a short-chain fatty acid oxidized predominantly in the mitochondria, had no effect. Addition of oleate also increased the steady-state level of catalase-H 2O 2. Pretreatment of rats for 1.5 hours with 3-amino-1,2,4-triazole (1.0 g/kg), an inhibitor of catalase, prevented the ethanol-dependent decrease in the steady-state level of catalase-H 2O 2 completely. Under these conditions, aminotriazole decreased rates of ethanol oxidation by about 50% and blocked the stimulation of ethanol oxidation by fatty acids. Oleate decreased rates of aniline hydroxylation by about 50%, indicating that cytochrome P 450 is not involved in the stimulation of ethanol uptake by fatty acids. Furthermore, oleate stimulated ethanol uptake in livers from ADH-negative deermice indicating that fatty acids do not simply displace 4-methylpyrazole from alcohol dehydrogenase. It is concluded that the stimulation of ethanol oxidation by fatty acids is due to increased H 2O 2 supplied by the peroxisomal β-oxidation of fatty acids for the catalase-H 2O 2 peroxidation pathway.