Genetic synchronization of the brain and liver molecular clocks defend against chrono-metabolic disease

Abstract

Nearly every cell of the body contains a circadian clock mechanism that is synchronized with the light-entrained clock in the suprachiasmatic nucleus (SCN). Desynchrony between the SCN and the external environment leads to metabolic dysfunction in shift workers. Similarly, mice with markedly shortened endogenous period due to the deletion of circadian REV-ERBα/β nuclear receptors in the SCN (SCN DKO) exhibit increased sensitivity to diet-induced obesity (DIO) on a 24 h light:dark cycle while mice with REV-ERBs deleted in hepatocytes (HepDKO) display exacerbated hepatosteatosis in response to a high-fat diet. Here, we show that inducing deletion of hepatocyte REV-ERBs in SCN DKO mice (Hep-SCN DDKO) rescued the exacerbated DIO and hepatic triglyceride accumulation, without affecting the shortened behavioral period. These findings suggest that metabolic disturbances due to environmental desynchrony with the central clock are due to effects on peripheral clocks which can be mitigated by matching peripheral and central clock periods even in a desynchronous environment. Thus, maintaining synchrony within an organism, rather than between endogenous and exogenous clocks, may be a viable target for the treatment of metabolic disorders associated with circadian disruption.

Keywords: REV-ERB; circadian rhythms; metabolism; obesity; suprachiasmatic Nucleus.

Fig. 1.

REV-ERBα/β double knockout in the liver and SCN. (A) Experimental scheme. (B and C) RT-qPCR for Nr1d1 and Nr1d2 in the SCN at ZT10 (n = 5 to 8, mean ± SEM). (D and E) RT-qPCR for Nr1d1 and Nr1d2 in the liver at ZT10 (n = 5 to 7, mean ± SEM). (F and G) RT-qPCR for Arntl and Npas2 in the SCN at ZT10 (n = 5 to 8, mean ± SEM). (H and I) RT-qPCR for Arntl and Npas2 in the liver at ZT10 (n = 5 to 7, mean ± SEM). Results were compared by one-way ANOVA with Tukey’s post hoc test. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Fig. 2.

Loss of REV-ERBs in the SCN is sufficient to shorten the circadian period of locomotor activity. (A–D) Representative actograms in LD and DD for Control, HepDKO, SCN DKO, and Hep-SCN DDKO. (E) Lomb–Scargle periodogram analysis for LD and DD actograms (n = 3, mean ± SEM). Results were compared by two-way ANOVA with Šidák’s post hoc test. ****P < 0.0001.

Fig. 3.

Loss of REV-ERBs in the SCN is sufficient to shorten the circadian period of metabolism. (A and B) LD and DD measurements for VO₂ (n = 3, mean ± SEM). (C) Lomb–Scargle periodogram analysis for VO₂ in LD and DD (n = 3, mean ± SEM). (D and E) LD and DD measurements for RER (n = 3, mean ± SEM). (F) Lomb–Scargle periodogram analysis for RER in LD and DD (n = 3, mean ± SEM). Periodogram results were compared using a two-way ANOVA with Šidák’s post hoc test. *P < 0.05, **P < 0.01.

Fig. 4.

Matching hepatocyte and SCN clocks rescues SCN DKO mice from exacerbation of DIO. (A) Running body weight gain over 12 wk of 60% HFD feeding (n = 4 to 5, mean ± SEM). (B) kcal of food consumed over 24 h (n = 4 to 5, mean ± SEM). (C) Serum triglyceride content (n = 4 to 6, mean ± SEM). (D) Liver triglyceride content (n = 6 to 9, mean ± SEM). Body weight gain results were compared by repeated measures ANOVA with Tukey’s post hoc test. Food intake, serum triglycerides, and liver triglycerides were compared by one-way ANOVA with Tukey’s post hoc test. *P < 0.05, **P < 0.01, ***P < 0.001.