OBJECTIVETo explore the effects of feeding mode on biological clock and circadian expression of lipids metabolism-related genes in mice.

METHODSNinety healthy male ICR mice were divided into 3 groups with 30 in each: ad libitum-feeding, daytime-feeding and nighttime-feeding groups, in a 12 h to 12 h light-dark cycle. After two weeks of feeding the animals was sacrificed in batches (5 in each batch) at 4, 8, 12, 16, 20 and 24 h, the circadian expression of lipids metabolism-related genes in the liver and brain was detected by real time quantitative RT PCR at 6 time points.

RESULTSThe circadian oscillator in the brain was more sensitive to alteration of feeding mode than that in the liver, nighttime feeding decreased peak mRNA levels of Cry2, Per1, and Per2 (5.5, 4.3 and 7.1 folds, respectively) in the brain. However, there was no difference in the expression rhythm of hepatic clock genes between nighttime-feeding and ad libitum group. In addition, changed feeding mode significantly decreased the peak value of Rev erbα (2 folds for daytime feeding, 3.4 folds for nighttime feeding) and Dbp (10.6 folds for daytime feeding, 2.8 folds for nighttime feeding), which two had opposite expression mode in different feeding modes. Different expression rhythm of lipid metabolism related genes SREBP1-c, PPARα, FAS, and CPT was shown with decreased mRNA expression levels of SREBP1-c and PPARα in daytime feeding (5.5 folds, 4 folds) and nighttime feeding (4.4 folds, 4.8 folds).

CONCLUSIONChanging the feeding mode could entrain circadian oscillators both in the brain and liver. What is more, hepatic circadian oscillators couple with the feeding time.