High-Fat Feeding Does Not Disrupt Daily Rhythms in Female Mice because of Protection by Ovarian Hormones

Abstract

Obesity in women is increased by the loss of circulating estrogen after menopause. Shift work, which disrupts circadian rhythms, also increases the risk for obesity. It is not known whether ovarian hormones interact with the circadian system to protect females from obesity. During high-fat feeding, male C57BL/6J mice develop profound obesity and disruption of daily rhythms. Since C57BL/6J female mice did not develop diet-induced obesity (during 8 weeks of high-fat feeding), we first determined if daily rhythms in female mice were resistant to disruption from high-fat diet. We fed female PERIOD2:LUCIFERASE mice 45% high-fat diet for 1 week and measured daily rhythms. Female mice retained robust rhythms of eating behavior and locomotor activity during high-fat feeding that were similar to chow-fed females. In addition, the phase of the liver molecular timekeeping (PER2:LUC) rhythm was not altered by high-fat feeding in females. To determine if ovarian hormones protected daily rhythms in female mice from high-fat feeding, we analyzed rhythms in ovariectomized mice. During high-fat feeding, the amplitudes of the eating behavior and locomotor activity rhythms were reduced in ovariectomized females. Liver PER2:LUC rhythms were also advanced by ~4 h by high-fat feeding, but not chow, in ovariectomized females. Together these data show circulating ovarian hormones protect the integrity of daily rhythms in female mice during high-fat feeding.

Keywords: C57BL/6J; bioluminescence; circadian; eating rhythm; female; high-fat diet; liver; obesity.

Figure 1

Female C57BL/6J mice are resistant to diet-induced obesity. Body masses (mean grams ± SD) of female C57BL/6J mice fed either chow (blue circles, n = 8) or 45% high-fat diet (red circles, n = 9) for 8 weeks. High-fat feeding began at 8 weeks old (at red arrow).

Figure 2

High-fat diet does not alter the phase of the liver circadian clock in female mice. (A) Female C57BL/6J PER2:LUC mice were fed chow (blue circles) or high-fat diet (red circles) for 1 week and liver explants were cultured. (B) The mean phases (±SD) of the peaks of the bioluminescence rhythms were plotted relative to last lights on (12L:12D cycle indicated by white and black bars, respectively). Number of livers/total number cultured: Chow 7/7; High-fat diet: 5/7 (p = 0.60).

Figure 3

The eating behavior rhythm is robust in females fed high-fat diet. Eating behavior was measured with infrared video cameras. (A) Representative actogram of eating behavior (1-min bins) of a female mouse fed chow (days 1–7, blue) and then switched to 45% high-fat diet (days 9–14, red, HFD added at red asterisk on day 8). Each vertical line is an eating event (1-min bins). Representative circular histograms show the distribution of eating behavior across the day (10-min bins) in an individual mouse during one day of chow [(B): day 7], during the first day of HFD [(C): day 9], and during the sixth day of HFD feeding [(D): day 14]. Scale: inner circle, 0; middle circle, 5; outer circle, 10. Grand mean vectors of eating behavior show the average eating behavior of female mice (n = 5) during chow [(E): day 7] and HFD [(F): day 9; (G): day 14] feeding. Scale: inner circle, 0; middle circle, 0.3; outer circle, 0.6. Lights were on from 0 to 12. Circular statistics are shown in Table S1 in Supplementary Material. Mean (±SD) amplitudes [(H), y-axis: length of grand mean vector] and phases [(I), y-axis: phase in ZT of grand mean vector] of male (n = 5) and female (n = 5) mice. Male data were taken from our previous study (26).

Figure 4

The amplitude of the locomotor activity rhythm in females is not affected by high-fat feeding. Locomotor activity was measured with passive infrared sensors. (A) Representative actogram of locomotor activity (6-min bins; scale: 5) of a female mouse fed chow (days 1–7) and then switched to 45% high-fat diet (days 9–14, high-fat diet added at red asterisk on day 8). (B) Group average activity profiles (y-axis: counts/6 min bin) of females fed chow (blue) for 1 week and then high-fat diet (red) for 1 week (n = 5 mice).

Figure 5

High-fat diet feeding advances the phase of the liver clock in ovariectomized females. (A) Representative traces of PER2:LUC bioluminescence recorded from ovariectomized mice fed chow (blue) or 45% high-fat diet (red) for 1 week (y-axis: counts per second). Phases were determined from the peaks of bioluminescence occurring between 12 and 36 h in culture (indicated by arrows). (B) Mean phases (±SD) of liver PER2:LUC rhythms from chow (n = 6)- and high-fat diet (n = 6)-fed ovariectomized mice (p < 0.001).

Figure 6

The eating behavior rhythm is compromised in ovariectomized females fed high-fat diet. Eating behavior was measured with infrared video cameras. (A) Representative actogram of eating behavior (1-min bins) of an ovariectomized female mouse fed chow (days 1–7, blue) and then switched to 45% high-fat diet (days 9–14, red, high-fat diet added at red asterisk on day 8). Each vertical line is an eating event. Representative circular histograms show the distribution of eating behavior across the day (10-min bins) in an individual ovariectomized female mouse during 1 day of chow [(B): day 7], during the first day of HFD [(C): day 9], and during the sixth day of HFD feeding [(D): day 14]. Scale: inner circle, 0; middle circle, 5; outer circle, 10. Grand mean vectors of eating behavior show the average eating behavior of ovariectomized female mice (n = 5) during chow [(E): day 7] and HFD [(F): day 9; (G): day 14] feeding. Scale: inner circle, 0; middle circle, 0.3; outer circle, 0.6. Lights were on from 0 to 12. Circular statistics are shown in Table S1 in Supplementary Material. Mean (±SD) amplitudes [(H), y-axis: length of grand mean vector] and phases [(I), y-axis: phase in ZT of grand mean vector] of intact (n = 5; data from Figure 3) and ovariectomized (n = 5) female mice.

Figure 7

The locomotor activity rhythm is reduced by high-fat feeding in ovariectomized female mice. Locomotor activity was measured with passive infrared sensors. (A) Representative actogram of locomotor activity (6-min bins; scale: 5) of an ovariectomized female mouse fed chow (days 1–7) and then switched to 45% high-fat diet (days 9–14, high-fat diet added at red asterisk on day 8). (B) Group average activity profiles (y-axis: counts/6-min bin) of ovariectomized females fed chow (blue) for 1 week and then high-fat diet (red) for 1 week (n = 5 mice).