Circadian Rhythm and Staying Healthy

Authors Summa and Turek in Atlas of Clinical Sleep Medicine, details the importance of a stable circadian rhythm, which maintains proper bodily functions. Animal subjects like mice are crucial in understanding the processes in humans. When there is disruption in out biological clocks, we becomes more susceptible to disorders and diseases including cardiomyopathy, diabetes, cancer, gastrointestinal diseases, and depression. A mismatch between the internal and external environments can lead to disease development.

At the Johns Hopkins University School of Medicine, research found a connection between disruptions in our natural circadian rhythms and the development of health issues. These rhythms determine our sleep-wake cycles and other biological processes and are regulated by the suprachiasmatic nucleus in the hippocampus area of the brain.

The research found a protein, Tenm3, in mice's visual systems that play a significant role in stabilizing the body's circadian rhythms. Circadian rhythms are controlled by the brain's response to light. Mice without Tenm3 could adjust their circadian rhythms a lot faster than mice with normal Tenm3. The mice experienced a standard 12-hour light/dark cycle then darkness again in  6 hours earlier than expected. If there were any fluctuations in light/dark, these mice with impaired Tenm3 were more sensitive and able to “reset” faster than normal mice. This study suggests that Tenm3 is extremely important for maintaining a stable circadian rhythm. Understanding the role of Tenm3 has significant implications for diagnosing and treating sleep disorders such as insomnia and jet lag in humans.

Light influences circadian rhythm, which then influences metabolism, allowing cells to function correctly in response to biological signaling. Studies included in the book chapter were done by controlling light and dark exposure in the environment, similar to what was done at JHU. Results from both studies indicate the important relationship between circadian rhythm and environment for a healthy life.

Summa, K.C., and Turek, F.W. Circadian Desynchrony and Health. Atlas of Clinical Sleep Medicine. Chapter 20 (168-174).

Hunyara, J. L., et al. (2023). Teneurin-3 regulates the generation of nonimage-forming visual circuitry and responsiveness to light in the suprachiasmatic nucleus. PLOS Biology. doi.org/10.1371/journal.pbio.3002412.