Drug Discovery News

The success of vaccines and cancer treatments varies depending on the time of day they are delivered. Researchers now look to exploit circadian rhythms to improve health outcomes.

On a warm Parisian evening around 1729, the Seine river snailed past the Institut de France, inside which polymath Jean-Jacques Dortous de Mairan fixated on the slow movements of a plant (1). The fern-like leaves of his Mimosa pudica spread wide toward the sun during the day. Yet at night, the leaves furled back inward as if to sleep.

Dortous de Mairan intervened. He stowed the plant in the dark, wondering whether the cycle would hold. It did (2). Even without absorbing sunlight, the mimosa carried out its daily rhythm. 200 years passed before biologists appreciated the discovery as an internal clock and coined the term “circadian rhythm.”

“For a few centuries, people interested in circadian rhythms were mainly botanists,” said Nicolas Cermakian, a chronobiologist at McGill University.

Today, scientists understand the importance of daily rhythms. The human circadian system regulates sleep and the function of every tissue in the body. All organs and cells throughout the body have their own internal clocks, which cycle between different functions such as assembling particular proteins and receiving molecular messages. Disruptions like sleep deprivation, shift work, and even jet lag can deteriorate health by increasing the risk of metabolic disorders, cardiovascular disease, and cancer, and scientists’ understanding of human rhythms is rapidly evolving (3).

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