PPARalpha is involved in photoentrainment of the circadian clock.

We found that bezafibrate, a ligand of peroxisome proliferator-activated receptor alpha (PPARalpha), advances the active phase of mice under light-dark (LD) conditions in a photoperiod-dependent manner. Bezafibrate gradually advanced the activity onset that consequently almost completely reversed the active phase from the dark to the light period under a long photoperiod (18 h of light and 6 h of darkness: LD 18 : 6). The activity onset was not changed under a short photoperiod (LD 8 : 16) or under constant illumination. These observations suggest that PPARalpha is involved in entrainment of the circadian clock to environmental LD conditions.