Restricted feeding entrains liver clock without participation of the suprachiasmatic nucleus.
BACKGROUND
There are two main stimuli that entrain the circadian rhythm, the light-dark cycle (LD) and restricted feeding (RF). Light-induced entrainment requires induction of the Per1 and Per2 genes in the suprachiasmatic nucleus (SCN), the locus of a main oscillator. In this experiment, we determined whether RF resets the expression of circadian clock genes in the mouse liver with or without participation of the SCN.


RESULTS
Mice were allowed access to food for 4 h during the daytime (7 h advance of feeding time) under LD or constant darkness (DD). The peaks of mPer1, mPer2, D-site-binding protein (Dbp) and cholesterol 7alpha-hydroxylase (Cyp7A) mRNA in the liver were advanced 6-12 h after 6 days of RF, whereas those in SCN were unaffected. The advance of mPer expression in the liver by RF was still observed in SCN-lesioned mice. A 7 h advance in the LD cycle advanced the peaks of clock gene expression in both the liver and SCN, whereas, a shift in the LD did not move the phase of the liver clock when the shift was carried out under a fixed RF schedule during the night-time.


CONCLUSIONS
These results suggest that restricted feeding strongly entrained the expression of circadian clock genes in the liver without the participation of an SCN clock function.
Department of Pharmacology and Brain Science, School of Human Sciences and Advanced Research Center for Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192, Japan.
R
R
Hara
K
K
Wan
H
H
Wakamatsu
R
R
Aida
T
T
Moriya
M
M
Akiyama
S
S
Shibata
D000818:Animals; D001683:Biological Clocks / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins; D005248:Feeding Methods; D005786:Gene Expression Regulation / Q000235:genetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D009687:Nuclear Proteins / Q000096:biosynthesis; D056950:Period Circadian Proteins; D013493:Suprachiasmatic Nucleus / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539022:PER1 protein, human; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D014157:Transcription Factors