Night-time feeding of Bmal1-/- mice restores SCFA rhythms and their effect on ghrelin.
The known crosstalk between short-chain fatty acids (SCFAs) and the circadian clock is tightly intertwined with feeding time. We aimed to investigate the role of the core clock gene Bmal1 and feeding time in the diurnal rhythms in plasma and caecal SCFA levels and in their effect on the release of the hunger hormone ghrelin in the stomach and colon. WT, Bmal1-/- (ad libitum fed) and night-time-restricted-fed (RF)-Bmal1-/- littermates were killed at zeitgeber time (ZT) 4 and 16. SCFA concentrations were measured by gas chromatography. To investigate the effect of SCFAs on ghrelin release, stomach and colonic full-thickness strips were incubated with Krebs or a SCFA mix mimicking plasma or caecal concentrations, after which octanoyl ghrelin release was measured by RIA. Diurnal rhythms in caecal and plasma SCFAs oscillated in phase but rhythmic changes were abolished in Bmal1-/- mice. RF of Bmal1-/- mice restored fluctuations in caecal SCFAs. Plasma SCFA concentrations failed to affect gastric ghrelin release. The effect of caecal SCFA concentrations on colonic ghrelin release was rhythmic (inhibition at ZT 4, no effect at ZT 16). In Bmal1-/- mice, the inhibitory effect of SCFAs at ZT 4 was abolished. RF Bmal1-/- mice restored the inhibitory effect and increased colonic Clock expression. To conclude, diurnal fluctuations in caecal SCFAs and the effect of SCFAs on colonic ghrelin release are regulated by feeding time, independent of the core clock gene Bmal1. However, local entrainment of other clock genes might contribute to the observed effects.
['Segers|Anneleen|A|', 'Desmet|Louis|L|', 'Sun|Shu|S|', 'Verbeke|Kristin|K|', 'Tack|Jan|J|', 'Depoortere|Inge|I|']
D056930:ARNTL Transcription Factors D000818:Animals D002432:Cecum D045744:Cell Line, Tumor D057906:Circadian Clocks D002940:Circadian Rhythm D003106:Colon D005232:Fatty Acids, Volatile D005247:Feeding Behavior D054439:Ghrelin D008297:Male D008810:Mice, Inbred C57BL D018345:Mice, Knockout D013270:Stomach D013997:Time Factors
ghrelin short-chain fatty acids circadian clock night-time restricted feeding