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Circadian mechanisms of food anticipatory rhythms in rats fed once or twice daily: clock gene and endocrine correlates.

Patton DF, Katsuyama AM, Pavlovski I, Michalik M, Patterson Z, Parfyonov M, Smit AN, Marchant EG, Chung SH, Chung J, Abizaid A, Storch KF, de la Iglesia H, Mistlberger RE - PLoS ONE (2014)

Bottom Line: Multiple clock genes from adrenals and stomachs were assayed by RT-PCR.Blood was assayed for corticosterone and ghrelin.Bmal1 expression was quantified in 14 brain regions by in situ hybridization.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Simon Fraser University, Burnaby, BC, Canada.

ABSTRACT
Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12∶12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times. After 30 days, brain, blood, adrenal and stomach tissue were collected at 6 time points. Multiple clock genes from adrenals and stomachs were assayed by RT-PCR. Blood was assayed for corticosterone and ghrelin. Bmal1 expression was quantified in 14 brain regions by in situ hybridization. Clock gene rhythms in adrenal and stomach from day-fed rats oscillated in antiphase with the rhythms in night-fed rats, and at an intermediate phase in rats fed twice daily. Corticosterone and ghrelin in 1-meal rats peaked at or prior to the expected mealtime. In 2-meal rats, corticosterone peaked only prior the nighttime meal, while ghrelin peaked prior to the daytime meal and then remained elevated. The olfactory bulb, nucleus accumbens, dorsal striatum, cerebellum and arcuate nucleus exhibited significant daily rhythms of Bmal1 in the night-fed groups that were approximately in antiphase in the day-fed groups, and at intermediate levels (arrhythmic) in rats anticipating 2 daily meals. The dissociations between anticipatory activity and the peripheral clocks and hormones in rats anticipating 2 daily meals argue against a role for these signals in the timing of behavioral rhythms. The absence of rhythmicity at the tissue level in brain regions from rats anticipating 2 daily meals support behavioral evidence that circadian clock cells in these tissues may reorganize into two populations coupled to different meals.

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Group mean (± SEM) optical densities representing Bmal1 and Per1 mRNA from the SCN (A–B) and dorsomedial hypothalamus (DMH, compact and ventral regions, C–F) in rats fed 2 h daily at ZT4 (red dashed curve) or ZT16 (blue solid curve), or for 1 h at both times (green dotted curve).
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pone-0112451-g004: Group mean (± SEM) optical densities representing Bmal1 and Per1 mRNA from the SCN (A–B) and dorsomedial hypothalamus (DMH, compact and ventral regions, C–F) in rats fed 2 h daily at ZT4 (red dashed curve) or ZT16 (blue solid curve), or for 1 h at both times (green dotted curve).

Mentions: Clock gene rhythms in the SCN, assessed by ISH, ICC or bioluminescent reporters, are generally assumed to be unperturbed by daytime restricted feeding schedules in rats and mice entrained to LD cycles, but shifts were reported in 1 of 3 studies that quantified Bmal1 expression [37], and in 4 of 10 studies that quantified Per1 mRNA or PER1 protein [9], [37], [38], [39]. Using ISH, we observed a significant rhythm of Bmal1 expression in the SCN of rats fed at ZT16 (Table 2), with peak expression at ZT16, but a marked attenuation of this rhythm in both the ZT4 and the 2-meal groups (Fig. 4A), primarily due to increased expression in the day relative to the night-fed group. Per1 also exhibited a significant rhythm in the ZT16 condition, with a peak identified at ZT6 by JTK-Cycle, in antiphase with Bmal1. In rats fed at ZT4, Per1 a significant 24 h rhythm was evident, although the amplitude was reduced the peak identified at ZT4 (Fig. 4B). The 2-meal group showed elevated Per1 expression at night, and a damped, non-significant 24 h rhythm. These results indicate that daytime and 2-meal schedules can alter clock gene expression in the SCN. The reduced expression of Per1 and increased expression of Bmal1 at mealtime in rats fed at ZT4 is consistent with other evidence that Per1, in nocturnal rodents, can be acutely suppressed by behavioral activation in the day [40].


Circadian mechanisms of food anticipatory rhythms in rats fed once or twice daily: clock gene and endocrine correlates.

Patton DF, Katsuyama AM, Pavlovski I, Michalik M, Patterson Z, Parfyonov M, Smit AN, Marchant EG, Chung SH, Chung J, Abizaid A, Storch KF, de la Iglesia H, Mistlberger RE - PLoS ONE (2014)

Group mean (± SEM) optical densities representing Bmal1 and Per1 mRNA from the SCN (A–B) and dorsomedial hypothalamus (DMH, compact and ventral regions, C–F) in rats fed 2 h daily at ZT4 (red dashed curve) or ZT16 (blue solid curve), or for 1 h at both times (green dotted curve).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263600&req=5

pone-0112451-g004: Group mean (± SEM) optical densities representing Bmal1 and Per1 mRNA from the SCN (A–B) and dorsomedial hypothalamus (DMH, compact and ventral regions, C–F) in rats fed 2 h daily at ZT4 (red dashed curve) or ZT16 (blue solid curve), or for 1 h at both times (green dotted curve).
Mentions: Clock gene rhythms in the SCN, assessed by ISH, ICC or bioluminescent reporters, are generally assumed to be unperturbed by daytime restricted feeding schedules in rats and mice entrained to LD cycles, but shifts were reported in 1 of 3 studies that quantified Bmal1 expression [37], and in 4 of 10 studies that quantified Per1 mRNA or PER1 protein [9], [37], [38], [39]. Using ISH, we observed a significant rhythm of Bmal1 expression in the SCN of rats fed at ZT16 (Table 2), with peak expression at ZT16, but a marked attenuation of this rhythm in both the ZT4 and the 2-meal groups (Fig. 4A), primarily due to increased expression in the day relative to the night-fed group. Per1 also exhibited a significant rhythm in the ZT16 condition, with a peak identified at ZT6 by JTK-Cycle, in antiphase with Bmal1. In rats fed at ZT4, Per1 a significant 24 h rhythm was evident, although the amplitude was reduced the peak identified at ZT4 (Fig. 4B). The 2-meal group showed elevated Per1 expression at night, and a damped, non-significant 24 h rhythm. These results indicate that daytime and 2-meal schedules can alter clock gene expression in the SCN. The reduced expression of Per1 and increased expression of Bmal1 at mealtime in rats fed at ZT4 is consistent with other evidence that Per1, in nocturnal rodents, can be acutely suppressed by behavioral activation in the day [40].

Bottom Line: Multiple clock genes from adrenals and stomachs were assayed by RT-PCR.Blood was assayed for corticosterone and ghrelin.Bmal1 expression was quantified in 14 brain regions by in situ hybridization.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Simon Fraser University, Burnaby, BC, Canada.

ABSTRACT
Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12∶12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times. After 30 days, brain, blood, adrenal and stomach tissue were collected at 6 time points. Multiple clock genes from adrenals and stomachs were assayed by RT-PCR. Blood was assayed for corticosterone and ghrelin. Bmal1 expression was quantified in 14 brain regions by in situ hybridization. Clock gene rhythms in adrenal and stomach from day-fed rats oscillated in antiphase with the rhythms in night-fed rats, and at an intermediate phase in rats fed twice daily. Corticosterone and ghrelin in 1-meal rats peaked at or prior to the expected mealtime. In 2-meal rats, corticosterone peaked only prior the nighttime meal, while ghrelin peaked prior to the daytime meal and then remained elevated. The olfactory bulb, nucleus accumbens, dorsal striatum, cerebellum and arcuate nucleus exhibited significant daily rhythms of Bmal1 in the night-fed groups that were approximately in antiphase in the day-fed groups, and at intermediate levels (arrhythmic) in rats anticipating 2 daily meals. The dissociations between anticipatory activity and the peripheral clocks and hormones in rats anticipating 2 daily meals argue against a role for these signals in the timing of behavioral rhythms. The absence of rhythmicity at the tissue level in brain regions from rats anticipating 2 daily meals support behavioral evidence that circadian clock cells in these tissues may reorganize into two populations coupled to different meals.

Show MeSH
Related in: MedlinePlus