The endogenous circadian clock programs animals to eat at certain times of the 24-hour day: What if we ignore the clock?

Abstract

The discovery of the molecular mechanisms underlying the circadian clock, which functions in virtually every cell throughout the body to coordinate biological processes to anticipate and better adapt to daily rhythmic changes in the environment, is one of the major biomedical breakthroughs in the 20th century. Twenty years after this breakthrough, the biomedical community is now at a new frontier to incorporate the circadian clock mechanisms into many areas of biomedical research, as studies continue to reveal an important role of the circadian clock in a wide range of biological functions and diseases. A forefront of this exciting area is the research of interactions between the clock and energy metabolism. In this review, we summarize animal and human studies linking disruptions of the circadian clock, either environmental or genetic, to metabolic dysfunctions associated with obesity, diabetes, and other metabolic disorders. We also discuss how these advances in circadian biology may pave the way to revolutionize clinical practice in the era of precision medicine.

Keywords: Circadian clock; Diabetes; Energy metabolism; Obesity.

Figure 1. Coordinated circadian timing in tissues across the human body

In humans, a master circadian clock located in the SCN of the brain synchronizes downstream clocks in cells throughout the body, regulating a wide range of tissue-specific functions. Health problems may occur when the synchronization and coordination of the circadian programs among tissues are disrupted.