Circadian Metabolomics: Insights for Biology and Medicine

A biological "circadian" clock governs nearly all aspects of mammalian behavior and physiology. This control extends from activities of entire organ systems down to individual cells, all of which contain autonomous molecular clocks. Under this control, a significant fraction of the cellular metabolome-the collection of all small-molecule metabolites-varies in abundance according to time of day. Comparing the rhythmic expression of transcripts, proteins, and metabolites has yielded valuable insights into clock-controlled physiological mechanisms. In the future, their analysis could provide a glimpse of instantaneous clock phase, even providing notions of clock time based upon molecules within a single breath. Such knowledge could be important for disease diagnosis and for chronopharmacology.