Role of PPAR in the control of torpor through FGF21-NPY pathway: From circadian clock to seasonal change in mammals

Abstract

In nature, hibernating animals encounter fasting, cold temperature and short day seasonally. Torpor is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism to adapt such a severe environment. Ablation of the central clock synchronizer, the suprachiasmatic nucleus in brain, abolishes torpor, a hibernation-like state, implicating the circadian clock involved in this seasonal change. Biologists knows well the energy source of daily heterotherms/hibernators changed from glucose to lipids in winter. Here we review several lines of evidence of a master transcriptional regulator in lipid catabolism, PPAR, in the control of torpor through FGF21-NPY pathway. This indicate the importance of circadianand photoperiodregulation of PPAR to tell seasons in our body. © 2009 Norio Ishida.