The role of the daily feeding rhythm in the regulation of the day/night rhythm in triglyceride secretion in rats

Figures & data

Table 1. Information on gene primers.

Gene	Forward primer	Reverse primer
Scd1	CTACAAGCCTGGCCTCCTGC	GGCACCCAGGGAAACCAGGA
Lipin1	TCACTACCCAGTACCAGGGC	TGAGTCCAATCCTTTCCCAG
ApoB	CACCTAAGATCAACAGTCGCTTC	TCGAAAGCCAGACCCACTT
Mttp	GCGAGTCTAAAACCCGAGTG	CACTGTGATGTCGCTGGTTATT
Arf	TGGCGCCACTACTTCCAG	TCGTTCACACGCTCTCTGTC
Gapdh	TGAACGGGAAGCTCACTGG	TCCACCACCCTG TTG CTGTA
Tbp	TTCGTGCCAGAAATGCTGAA	TGCACACCATTTTCCCAGAAC

Abbreviations used: Scd1: stearoyl-Coenzyme A desaturase 1; Apob: Apolipoprotein B; Mttp: microsomal triglyceride transfer protein; Arf1: ADP-ribosylation factor 1; Gapdh: Glyceraldehyde 3-phosphate dehydrogenase; Tbp: TATA box binding protein.

Figure 1. The daily rhythm of plasma TG (a) and TG secretion (b). Data are presented as mean±SEM. Gray area represents the dark period.

Figure 2. Effects of a 6-meals-a-day feeding (6M) schedule on basal plasma TG levels (a) and the daily TG secretion rhythm (b). Data are presented as mean±SEM. White bars – Ad libitum (AL) animals, Black bars – 6M animals. * indicates a significant difference between ZT11 and ZT23 for the AL animals, p ≤ 0.05.

Figure 3. Effects of a 6-meals-a-day feeding schedule (6M) on the 24 h profile of body temperature and locomotor activity. (a) The 24 h profile of body temperature; (b) the day/night rhythm of body temperature; (c) the 24 h profile of locomotor activity (values are percentages of 24 h-mean); (d) the day/night rhythm of locomotor activity (values are percentages of 24h-mean) and (e) the day/night rhythm of food intake. Data are presented as mean±SEM. White bars and Grey line – AL animals, Black bars and Black line – 6M animals. * indicates a significant difference between night and day, p < 0.05. # indicates a significant difference between 6M and AL animals, p < 0.05.

Table 2. Effects of the 6-meals-a-day feeding schedule on daily gene expression rhythms in liver.

Gene	Time		Two-way ANOVA
	AL	6M	Time	Treatment	Interaction
Scd1	0.041	0.185	0.912	0.042	0.006
Lipin1	0.145	0.034	0.005	0.524	0.549
ApoB	0.066	0.166	0.011	0.720	0.779
Mttp	0.033	0.453	0.026	0.647	0.728
Arf	0.703	0.521	0.652	0.075	0.535

Significant differences are in bold.

Figure 4. Effects of a 6-meals-a-day (6M) feeding schedule on daily gene expression rhythms in liver. *p < 0.05. Open circles – data points of AL group. Solid line – Circwave calculated curve for AL group. Solid circles – data points of 6M group. Dashed line – circwave calculated curve for experimental 6M group.

Table 3. Circwave V1.4 analysis of effects of a 6-meals-a-day feeding schedule on daily TG secretion related gene expression rhythms in liver.

Gene	Acrophase in ZT		Amplitude (%)*
	AL	6M	AL	6M
Scd1	22.3	ns	37.6	—
Lipin1	ns	12.49	—	30.5
ApoB	2.32	ns	25.9	—
Mttp	21.21	ns	13.8	—
Arf	ns	ns	—	—

ns = non rhythmic according to Circwave.

*The mean 24h expression of each gene per feeding group was set to 100% and the relative expression of each gene at each measured time point was subsequently converted into a relative percentage value. Following conversion, we calculated the amplitude as (% peak value – % trough value)/2.