Insight into the circadian clock within rat colonic epithelial cells.
OBJECTIVE
The gastrointestinal tract exhibits diurnal rhythms in many physiologic functions. These rhythms are driven by food intake but are also preserved during food deprivation, suggesting the presence of endogenous circadian rhythmicity. The aim of the study was to provide insight into the circadian core clock mechanism within the rat colon. Moreover, the potency of a restricted feeding regime to shift the circadian clock in the colon was tested. The question of whether the colonic clock drives circadian expression in NHE3, an electroneutral Na(+)/H(+) exchanger, was also addressed.


METHODS
Daily profiles in expression of clock genes Per1, Per2, Cry1, Bmal1, Clock, and Rev-erbalpha, and the NHE3 transporter were examined by reverse transcriptase-polymerase chain reaction and their mRNA levels, as well as PER1 and BMAL1 protein levels, were localized in the colonic epithelium by in situ hybridization and immunocytochemistry, respectively.


RESULTS
Expression of Per1, Per2, Cry1, Bmal1, Clock, Rev-erbalpha, and NHE3, as well as PER1 and BMAL1 protein levels, exhibited circadian rhythmicity in the colon. The rhythms were in phase with those in the liver but phase-delayed relative to the master clock in the suprachiasmatic nucleus. Restricted feeding entrained the clock in the colon, because rhythms in clock genes as well as in NHE3 expression were phase-advanced similarly to the clock in the liver.


CONCLUSIONS
The rat colon harbors a circadian clock. The colonic clock is likely to drive rhythmic NHE3 expression. Restricted feeding resets the colonic clock similarly to the clock in the liver.
Department of Neurohumoral Regulations, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Martin
M
Sládek
Markéta
M
Rybová
Zuzana
Z
Jindráková
Zdena
Z
Zemanová
Lenka
L
Polidarová
Libor
L
Mrnka
John
J
O'Neill
Jirí
J
Pácha
Alena
A
Sumová
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics*; D003106:Colon / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D056931:Cryptochromes; D004268:DNA-Binding Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism*; D005247:Feeding Behavior; D005420:Flavoproteins / Q000378:metabolism; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism; D056953:Nuclear Receptor Subfamily 1, Group D, Member 1; D056950:Period Circadian Proteins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000201:enzymology / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D056931:Cryptochromes; D004268:DNA-Binding Proteins; D005420:Flavoproteins; D009687:Nuclear Proteins; D056953:Nuclear Receptor Subfamily 1, Group D, Member 1; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D015534:Trans-Activators; C538965:Cry1 protein, rat; C498263:Nr1d1 protein, rat; C539024:Per1 protein, rat; C513311:Per2 protein, rat; C000613387:Slc9a3 protein, rat; C538945:Clock protein, rat