Environmental regulation of metabolism through the circadian clock

The circadian clock, a highly complex network of hierarchical oscillators, integrates daily environmental signaling to organize temporal segregation of metabolic pathways in a tissue-specific manner. Hence, 24-h period oscillations are observed in many physiological functions. The mammalian molecular clock involves specialized transcription factors which intertwine to synchronize cyclic transcription of specific genes controlling metabolic homeostasis. Importantly, a circadian epigenome assists rhythmic transcription through coordinated interactions with the clock machinery. Mounting evidence shows that exposure to environmental challenges such as unbalanced diet, endocrine disruptors or artificial light modifies the molecular clock function and reprograms the circadian transcriptome in different tissues, leading to metabolic disorder. In this review, we discuss the molecular mechanisms connecting environmental signaling to the clock-controlled metabolism and the role of circadian transcription and epigenetic regulation in this crosstalk.