Expression of the clock gene Rev-erb in the brain controls the circadian organisation of food intake and locomotor activity, but not daily variations of energy metabolism

The nuclear receptor REV-ERB is part of the molecular clock mechanism and is considered to be involved in a variety of biological processes within metabolically active peripheral tissues as well. To investigate whether Rev-erb (also known as Nr1d1) in the brain plays a role in the daily variations of energy metabolism, feeding behaviour and the sleep-wake cycle, we studied mice with global (GKO) or brain (BKO) deletion of Rev-erb. Mice were studied both in a light/dark cycle and in constant darkness, and then 24-hour variations of Respiratory quotient (RQ) and energy expenditure, as well as the temporal patterns of rest-activity and feeding behaviour, were recorded. The RQ increase of GKO mice was not detected in BKO animals, indicating a peripheral origin for this metabolic alteration. Arrhythmic patterns of locomotor activity were only found in BKO mice. By contrast, the circadian rhythm of food intake was lost both in GKO and BKO mice, mostly by increasing the number of daytime meals. These changes in the circadian pattern of feeding behaviour were, to some extent, correlated with a loss of rhythmicity of hypothalamic Hcrt (also named Orx) mRNA levels. Taken together, these findings highlight that Rev-erb in the brain is involved in the temporal partitioning of feeding and sleep, whereas its effects on energy metabolism are mainly exerted through its peripheral expression.