The genetic mechanism: how our internal clocks work

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

Everyone has heard about the internal clock, but few people know how they work. Two groups of scientists from the United States have carried out large-scale studies to understand how our clocks work and what is their effect on the body.

Throughout the day, we listen to the "ticking" of the clock inside our body. It is this that wakes us up in the morning and makes us feel sleepy at night. It is it that raises and lowers our body temperature at the right time, regulates the production of insulin and other hormones.

The internal clock of the body, the very ticking that we feel, is also called circadian rhythms.

These rhythms even affect our thoughts and feelings. Psychologists study their effects on the human brain by forcing volunteers to take cognitive tests at different times of the day.

It turned out that morning is the best time to perform tasks that require the brain to multitask. If you need to keep several layers of information in your head at once and process this data promptly, you should start working at the beginning of the day. But the second half of the day is well suited for processing simple and understandable tasks.

Circadian rhythms have a huge impact on those suffering from depression or bipolar disorder as well. People with these problems do not sleep well and feel the urge to drink throughout the day. Some dementia patients experience a special “sunset effect”: at the end of the day they become aggressive or lost in space and time.

“Sleep and activity cycles are a critical part of mental illness,” says Huda Akil, a neuroscientist at the University of Michigan. Therefore, neuroscientists are struggling to understand how our internal clocks work and what effect they have on our brain. But researchers can't just open the skull and watch cells work around the clock.

Several years ago, the University of California donated brains for research, which were carefully preserved after the death of donors. Some of them died in the early morning, others in the afternoon or at night. Dr. Akil and her colleagues decided to study whether one brain is different from another and whether the difference depends on the moment at which the donor died.

“Maybe our guess will seem simple to you, but for some reason no one thought about it before,” says Dr. Akil.

She and her colleagues selected brain specimens from 55 healthy people who died in a sudden accident, such as a car accident. From each brain, the researchers took tissue samples from those lobes that are responsible for learning, memory and emotion.

At the time of donor death, genes in brain cells actively encoded a protein. Thanks to the fact that the brain was quickly preserved, scientists are able to assess the activity of genes at the moment of death.

Most of the genes the researchers tested did not show any pattern in their performance throughout the day. However, more than 1,000 genes show a daily cycle of activity. The brains of those people who died at the same time of day showed the same genes at work.

The activity patterns were nearly identical, so much so that they could be used as a timestamp. It was almost unmistakable to determine at what moment a person died, thanks to the measurement of the activity of these genes.

Then the researchers tested the brains of those donors who suffered from clinical depression. Here the time stamp was not just knocked down: it seemed that these patients lived either in Germany or in Japan, but not in the United States.

The results of the work done were published in 2013. Researchers at the University of Pittsburgh were inspired by them and tried to reproduce the experiment.

“We couldn't have thought of a study like this before,” says neurologist Colleen McClung. Dr. McKlang and her colleagues were able to test 146 brain specimens from the university's donor program. The results of the experiment were published quite recently.

But Dr. McClang's team was able not only to repeat the results of the previous experiment, but also to obtain new data. They compared patterns of gene activity in the brains of young and old people and found an intriguing difference.

Scientists hoped to find an answer to the question: why do the circadian rhythms of humans change as they age? After all, as people get older, activity decreases and rhythms change. Dr. McClang found that some of the genes that were most active in daily cycles were no longer in use by age 60.

It is possible that some older people stop producing the protein needed to keep their internal clocks running.

Also, the researchers were surprised to find that some genes were included in active daily work only in old age. “It seems that the brain is trying to compensate for the shutdown of some genes by the work of others by activating the extra clock,” says Dr. McClang. Perhaps the brain's ability to create reserve circadian rhythms is a defense against neurodegenerative diseases.

Switching to a spare internal clock can be used by doctors to treat circadian rhythm disorders. Researchers are now experimenting with animal genes and trying to understand how the genes of the internal clock are activated and turned off.

In other words, scientists listen to the “ticking” and want to understand: what is the brain trying to tell us?