Effect of bezafibrate on hepatic oxidative stress: comparison between conventional experimental doses and clinically-relevant doses in mice.

Several rodent studies have demonstrated that fibrate drugs can activate peroxisome proliferator-activated receptor alpha (PPARalpha) and increase reactive oxygen species (ROS) production. The persistence of strong PPARalpha activation is considered to be a possible mechanism related to the adverse effects of these agents in humans. We recently found that bezafibrate-treated mice at clinically-relevant doses (10 mg/kg/day) exhibited similar pharmacokinetics to humans, but were different from previous rodent data (> 50 mg/kg/day). To examine whether clinical doses of bezafibrate do in fact activate PPARalpha and increase hepatic oxidative stress in mice, we administered bezafibrate to wild-type and Ppara-null mice at high (100 mg/kg/day) or low (10 mg/kg/day) doses and assessed ROS-related pathways in the liver. High-dose bezafibrate increased hepatic lipid peroxides in a PPARalpha-dependent manner, likely from discordant induction of PPARalpha-regulated ROS-generating enzymes (acyl-CoA oxidase, cytochrome P450 4A, and NADPH oxidase) and enhancement of mitochondrial beta-oxidation. The treatment also activated protein kinase C and phosphatidylinositol-3-kinase in wild-type mice only, suggesting an association between strong PPARalpha activation and an altered cell signaling cascade. Meanwhile, low-dose bezafibrate reduced serum/liver triglycerides in both genotypes without activating PPARalpha or enhancing hepatic oxidative stress. These results may support the safety of bezafibrate treatment at clinically-relevant doses.