The nuclear receptor Rev-erbα controls circadian thermogenic plasticity

Abstract

Circadian oscillation of body temperature is a basic, evolutionarily conserved feature of mammalian biology. In addition, homeostatic pathways allow organisms to protect their core temperatures in response to cold exposure. However, the mechanism responsible for coordinating daily body temperature rhythm and adaptability to environmental challenges is unknown. Here we show that the nuclear receptor Rev-erbα (also known as Nr1d1), a powerful transcriptional repressor, links circadian and thermogenic networks through the regulation of brown adipose tissue (BAT) function. Mice exposed to cold fare considerably better at 05:00 (Zeitgeber time 22) when Rev-erbα is barely expressed than at 17:00 (Zeitgeber time 10) when Rev-erbα is abundant. Deletion of Rev-erbα markedly improves cold tolerance at 17:00, indicating that overcoming Rev-erbα-dependent repression is a fundamental feature of the thermogenic response to cold. Physiological induction of uncoupling protein 1 (Ucp1) by cold temperatures is preceded by rapid downregulation of Rev-erbα in BAT. Rev-erbα represses Ucp1 in a brown-adipose-cell-autonomous manner and BAT Ucp1 levels are high in Rev-erbα-null mice, even at thermoneutrality. Genetic loss of Rev-erbα also abolishes normal rhythms of body temperature and BAT activity. Thus, Rev-erbα acts as a thermogenic focal point required for establishing and maintaining body temperature rhythm in a manner that is adaptable to environmental demands.

Figure 1. Rev-erbα mediates the circadian patterning of cold tolerance

a, Rev-erbα mRNA (n=3) in BAT of WT and Rev-erbα KO mice. b, Cold tolerance tests (CTT) and, c, survival curves for Rev-erbα KO mice and control littermates from ZT4-10 (11 AM-5 PM). d, CTTs and, e survival curves from ZT16-22 (11 PM-5 AM). The numbers of Rev-erbα KO and control mice in the CTT are indicated above or below the first data point, respectively; subsequent designations at data points are made if any animals were removed for having a temperature below 25°C. f, Oxygen consumption rate (n=10) and, g, electromyogram (EMG) (n=4) measurements of cold-challenged Rev-erbα KO mice and WT controls. h, Oxygen consumption rates of BAT isolated from animals exposed to cold for 1 h (n=3). ** p <0.01, *** p <0.001 as analyzed by two-tailed Student’s t-test, one-way ANOVA, or Gehan-Breslow-Wilcoxon and Log-rank (Mantel-Cox) tests for the survival curves. Data are expressed as mean ± s.d.

Figure 2. Cold stress rapidly down-regulates Rev-erbα

a, BAT mRNA (n=3) and, b, protein levels from WT mice following a cold exposure time course (n=2; each lane of the western blot represents pooled biological duplicates). c, BAT mRNA (n=3) following 3 h NE administration (1 mg/kg i.p.) or cold exposure (n=3). * p<0.05, ** p<0.01, *** p <0.001 as determined by one-way ANOVA with multiple comparisons and a Tukey post-test. Data are expressed as mean ± s.d.

Figure 3. Rev-erbα represses thermogenic programming

a, BAT mRNA (n=6) and, b, protein from WT and Rev-erbα KO mice acutely exposed to cold for 6 h from ZT4-10. c, BAT mRNA following 3 h of NE administration from ZT7-10 (1 mg/kg i.p.) (n=3). d, Ucp1 mRNA levels in preadipocytes isolated from Rev-erbα KO mice and WT littermates in which either Rev-erbα or vector control has been ectopically expressed (n=4). e, Rev-erbα occupancy at the Ucp1 proximal promoter. Rev-erbα-specific peaks are shaded. g, Ucp1 gene expression in BAT over a 24 h period (n=3). * p<0.05, ** p<0.01, *** p <0.001 as determined by two-tailed Student’s t-test or one-way ANOVA with multiple comparisons and a Tukey post-test. Data are expressed as mean ± s.d.

Figure 4. Rev-erbα orchestrates daily rhythms of body temperature and BAT activity

a, Core (n=6) and, b, BAT (n=10) temperatures measured from subcutaneously implanted thermometers. c, Quantified thermographic measurements of surface temperature (n=5) and, d, 18-fluorodeoxyglucose (¹⁸FDG) imaging (n=4) of Rev-erbα KO mice and WT littermates during the light and dark phases. Representative coronal planes are shown for each group. e, Percent injected dose of ¹⁸FDG in the BAT of animals from the study in 4d. * p<0.05, ** p<0.01, *** p <0.001 as determined by two-tailed Student’s t-test or one-way ANOVA with multiple comparisons and a Tukey post-test. Data in 4a are expressed as rolling averages (±2 time points) ± s.e.m.; data in 4b are expressed as mean ± s.e.m.; data in 4c are expressed as a max to min box-and-whiskers plot; data in 4e are expressed as a mean ± s.d.