• Mouse circadian plasma leptin and active ghrelin rhythms under ad libitum and scheduled feeding

      Wan, Haiting (2007-08)
      Light is the strongest timing cue for the circadian system, but non-photic cues can also entrain the master circadian clock, i.e., suprachiasmatic nuclei (SCN). In one of our mouse line (ENTR), all mice entrain to scheduled feeding, while in another (NON-ENTR) only 4 % entrain. In order to explore key physiological pathways involved in that process, I quantified the circadian rhythms of plasma leptin and active ghrelin of these two lines of mice under a 12:12 hour light-dark cycle with ad libitum feeding and six hours of food availability during the light period. Plasma active ghrelin induced opposite circadian rhythms compared to leptin, which were most pronounced under scheduled feeding when leptin was highest during and right after the food availability period; active ghrelin was highest at night when food was not available. Compared to ad libitum feeding, the overall concentration of leptin decreased and active ghrelin concentration increased significantly under scheduled feeding. The plasma active ghrelin circadian rhythms of ENTR mice were more robust with higher amplitude rhythms than the NON-ENTR mice under ad libitum feeding and scheduled feeding. I hypothesize that the high amplitude plasma active ghrelin circadian rhythm provides a signal for the ENTR mice to entrain to scheduled feeding