Study Uncovers New Insight into Circadian Clocks

Researchers in Israel have come up with a groundbreaking approach to monitor the body’s circadian rhythms. A recent peer-reviewed study reveals that female sex hormones significantly influence the adjustment of these internal clocks.

Every human’s body contains a primary circadian clock located in the brain, which regulates daily cycles. Yet, there are also numerous circadian clocks present in nearly every cell, each maintaining its own rhythm.

The study’s authors utilized a technique called CircaSCOPE to examine the circadian rhythms across various cells. Their findings indicate that female sex hormones, especially progesterone, along with cortisol, a stress hormone, play a major role in calibrating these internal timekeepers.

When alignment falters, it can lead to severe health issues, such as sleep disorders, diabetes, and even cancer. “It’s crucial for the body to synchronize millions of these clocks found in each cell,” remarked a researcher from the Weizmann Institute of Science.

“The impact of sex hormones is particularly pronounced on these clocks,” they added, noting the less significant effects of male hormones. Interestingly, however, the researchers still lack clarity on how this mechanism affects men.

It’s important to mention that the experiments conducted were only in cell cultures, without testing on animals or humans yet. But there is hope; understanding how these clocks interact could lead to better explanations for various health issues and aid patients with disrupted internal timing.

This research may also illuminate shifts in circadian rhythms during menstruation, pregnancy, and menopause.

The study, led by a team of researchers, was published in Nature Communications.

Understanding Our Internal Clocks

Historically, scientists believed there was just one main clock in the brain responding to light and darkness to regulate physiology and behavior. However, about 25 years ago, it was discovered that multiple clocks exist in every tissue and cell throughout the body.

Circadian rhythms are influenced not only by external elements like sunlight but also by signals circulating in the bloodstream. When these internal and external times are out of sync, various health problems can arise. A common example is jet lag, where an individual’s internal clock doesn’t match the environment.

“Light is the principal signal to the brain,” the researcher explained. Yet, recent findings suggest illnesses may be linked to unsynchronized clocks among different organs, such as the liver and kidneys, which ideally should align.

The Role of Oxygen

In additional research, the lab demonstrated that oxygen levels influence these internal clocks as well. During a 2020 expedition to La Rinconada, Peru—an area with lower oxygen levels—the researchers observed changes in gene rhythms, which might be connected to various oxygen-related health issues.

Exploring New Signals

Asher’s team highlighted the need to identify blood-circulating signals that may also function as time indicators for these clocks. Previously, mapping such signals was a challenge due to a lack of effective methods for tracking responses over a full day.

The CircaSCOPE technique now allows rapid monitoring of cell clocks. Researchers can see how cells react to various signals, assessing if their clocks speed up, slow down, or remain unchanged. This method dramatically reduces the time needed for such analyses.

A Shift in Understanding Clock Mechanisms

Moreover, the study has revealed that the protein CRY2, not PER2 as once thought, is the primary component receiving signals from hormones in the blood. It appears that sex hormones and other influences interact with this protein to relay information to the cellular clocks.

A colleague pointed out that while simpler organisms use CRY2-based proteins to sense light, mammals now utilize them to synchronize their internal clocks with hormonal signals. This could help explain shifts in daily rhythms across different life stages.

Asher’s research indicates that monitoring hormones’ effects on circadian rhythms holds significant potential for future healthcare treatments. Identifying the right hormonal signals could lead to breakthroughs in addressing various health disorders associated with timing disruptions.