Light-influenced biorhythms say a lot about health

For a few days after the full moon in November each year, Australia’s Great Barrier Reef is an amazing spectacle. Corals release billions of eggs and sperm into the water, which combine to form planktonic larvae. These eventually settle and form new coral colonies.

Corals aren’t the only creatures whose reproduction is synchronized by moonlight. Such rhythms are usually governed by a circular lunar clock, a type of biological clock controlled by proteins that synchronize with her 29.5-day cycle between new moons.

Synchronization

Most multicellular organisms have, or are thought to have, some sort of internal clock, and many important processes, including feeding and reproduction, rely on precise timing. Being able to stay “in sync” is the key to survival.

Professor Christine Tesmer-Rybl, a neurobiologist at the University of Vienna, Austria, said: “Understanding how the time-related interconnections of individuals within and across species operate is important for ecological research. important for a stable system,” he said.

Another perhaps more familiar body clock, the circadian clock, regulates the daily 24-hour sleep-wake cycle in response to environmental signals such as light and temperature. The watch’s name comes from the Latin words “circa” meaning “around” and “dies” meaning “day”.

This complex system regulates everything from sleep and digestion to metabolism and mood. Researchers are shedding light on environmental factors that can desynchronize these biological rhythms.

However, many unclear points remain about “chronobiology”, including the mechanisms involved at the genetic and molecular levels.

moonlight signal

To dig deeper, Tesmar Leible has been studying the circadian rhythms of marine animals as part of an EU-funded study. big time The project will run for five years until 2024.

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Many hormones in the C. elegans species we study are closely related to human hormones.

One of her focus is a marine caterpillar called Platynereis dumerilii, which lives in coastal waters from temperate to tropical seas.

“Our greatest achievement so far has been the discovery of photoreceptors, or light-sensing cells, that provide organisms with information about the type of light and the duration of moonlight in the sky,” said Tesmar Leible. .

The L-Cry protein identified by the researchers belongs to a group of light-sensing molecules called cryptochromes. This protein is important because it helps explain how organisms can synchronize to specific moon phases.

This study suggests that L-Cry acts as a gatekeeper, allowing only the ‘appropriate’ light to affect the worms. It can also distinguish between light levels for different moon phases and between sunlight and moonlight.

“This could explain how individual nematodes are able to synchronize their lunar clocks to the same lunar phase,” said Tesmar-Rybl. “We believe that not only does moonlight play a role in monthly timing, but we also schedule the exact time that night flocks begin during the darkest hours of the night, presumably to optimize survival and reproduction. I discovered that

It is hoped that Mari.Time will provide new clues about how human impacts such as artificial light and climate change affect ecosystem stability, and suggest ways to mitigate their impacts. increase.

Given the growing evidence that the moon influences things like sleep and depression, the project may also help research human health.

“Many of the C. elegans species we study have hormones that are closely related to human hormones,” said Tesmar Leibl.

He said studying the mechanics of lunar cycles in marine life could lead to a better understanding of other lunar patterns. These include menstrual cycles and mood patterns in certain psychiatric disorders.

night and day

Professor Johanna Meyer, who studies biological clocks at the University of Leiden in the Netherlands, has been studying the circadian rhythms of animals for over 30 years.

She says there are still many unknowns about the circadian clock, such as how it works in diurnal or diurnal species like humans.

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Avoiding blue light isn’t enough if you don’t want your watch to get in the way.

Meyer said more is known about nocturnal animals because, like mice, which are commonly used in the laboratory, they are easier to test at the molecular level.

funded by the EU health during the day The project she leads is investigating the differences between diurnal and nocturnal animals.

Circadian rhythms are controlled by a group of neurons in the hypothalamus known as the suprachiasmatic nucleus (SCN), which acts as the body’s master clock.

Because the SCN is light sensitive, it helps regulate the sleep-wake cycle by entraining with the natural light and darkness of the environment.

There is evidence that when the SCN is impaired, such as during long-distance travel or shift work, it can lead to a variety of health problems, such as sleep disturbances, depression, diabetes, and even cancer.

Meyer’s pioneering work on SCNs in diurnal rodents, such as the Sudanese rice mouse and a species of diurnal ground squirrel, provides new information about how circadian rhythms are generated and synchronized. providing.

The study also provides insight into how environmental signals such as light, temperature and physical activity are used to fine-tune the body clock.

“SCNs can recognize behavioral input as well as light input, and this behavioral input may enhance the clock,” Meyer said. “Isn’t that great?” So our own actions are actually part of the feedback loop. “

This means that it may be possible to correct disturbances in internal rhythms using external cues. Light is a prime candidate, but other factors such as exercise, temperature, and meal times also play a role.

light level, color

A breakthrough in imaging technology utilized by the research team allowed the SCN to be viewed in unprecedented detail.

The results of this study suggest that diurnal rodent cells are less sensitive to light than nocturnal rodent cells.

“This shows that diurnal animals and humans need more than nocturnal animals to get the light they need for their clocks,” Meyer said.

In another study, light levels appear to affect serotonin synthesis in diurnal rats more strongly than in nocturnal rats. Since serotonin influences mood, emotions and appetite, such findings could have implications for human diseases such as depression.

The researchers also provided a more direct indication that the circadian clock is affected by different colors of light, not just the blue part of the visible spectrum, which is responsible for the negative effects of artificial night lights and electronic screens. I also found evidence.

Blue light is known to disrupt circadian rhythms and make people feel alert instead of tired. But among the colors the team tested, green and orange light also affected the circadian clock, and only violet showed little effect.

“It’s a little warning that if you don’t want to mess with your clock, don’t just stay away from blue light,” Meyer said.

global impact

Emerging from both projects is a more detailed understanding of the precise mechanisms of biological clocks and their importance in the functioning of humans and other animals.

This finding could lead to new and effective recommendations for improving lifestyle patterns and protecting the natural environment.

Meyer emphasized the importance of how these things affect all ecosystems, not just people.

“After billions of years of evolution, the light-dark cycle has become a favorite for animals,” she says. “Now we shine a light on the Earth as if it were harmless, but it really isn’t.”

The research in this article was funded through the European Research Council (ERC) in the EU. If you liked this article, please consider sharing it on social media.