Raloxifene affects fatty acid oxidation in livers from ovariectomized rats by acting as a pro-oxidant agent

Estrogen deficiency accelerates the development of several disorders including visceral obesity and hepatic steatosis. The predisposing factors can be exacerbated by drugs that affect hepatic lipid metabolism. The aim of the present work was to determine if raloxifene, a selective estrogen receptor modulator (SERM) used extensively by postmenopausal women, affects hepatic fatty acid oxidation pathways. Fatty acids oxidation was measured in the livers, mitochondria and peroxisomes of ovariectomized (OVX) rats. Mitochondrial and peroxisomal β-oxidation was inhibited by raloxifene at a concentration range of 2.5-25 μM. In perfused livers, raloxifene reduced the ketogenesis from endogenous and exogenous fatty acids and increased the β-hydroxybutyrate/acetoacetate ratio. An increase in 14CO2 production without a parallel increase in the oxygen consumption indicated that raloxifene caused a diversion of NADH from the mitochondrial respiratory chain to another oxidative reaction. It was found that raloxifene has a strong ability to react with H2O2 in the presence of peroxidase. It is likely that the generation of phenoxyl radical derivatives of raloxifene in intact livers led to the co-oxidation of NADH and a shift of the cellular redox state to an oxidised condition. This change can perturb other important liver metabolic processes dependent on cellular NADH/NAD+ ratio.

► The effects of raloxifene on fatty acid oxidation were examined in ovariectomized rats. ► Ketogenesis was reduced and 14CO2 production from fatty acids was stimulated. ► Mitochondrial and peroxisomal β-oxidation of fatty acids were inhibited. ► The peroxidase-catalized reaction of raloxifene with H2O2 led to NADH oxidation. ► The pro-oxidant effect of raloxifene can perturb important liver metabolic processes.