Don't stay up late! The DNA in your body is constantly breaking down, and it can only be repaired if you get enough sleep!

Expert of this article: Zhao Wei, MD, associate chief physician, Tianjin University Teda Hospital

When it’s late at night and everything is quiet, when you “stay up late and apply the most expensive facial mask”, have you ever thought: Why do people need to sleep?

Not only you, scientists are also curious about why animals seem to need to sleep.

Recent studies have found that the reason we need sleep may be to repair DNA that is constantly breaking.

David Zada ​​et al. Parp1 promotes sleep, which enhances DNA repair in neurons.

DNA is the most important substance in our body, controlling birth, aging, illness and death.

When a child looks like his parents, we often say it is genetics, but it is actually because of DNA.

Such an important substance is actually breaking all the time? Sleeping can repair DNA, so if we stay up late...

Is the DNA in our bodies breaking all the time?

DNA, also known as deoxyribonucleic acid, is a biological genetic material composed of four chemical bases: adenine, guanine, cytosine, and thymine.

Human DNA is composed of about 3 billion bases, the order of which determines the body's unique genetic code, just like letters are arranged in a certain order to form different words and sentences.

An important property of DNA is its ability to replicate itself, and during this process, DNA breakage occurs all the time.

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The causes of DNA breakage can be roughly divided into two categories: exogenous and endogenous.

Exogenous factors include physical factors (such as ultraviolet rays and ionizing radiation), chemical factors (such as chemical raw materials, tobacco and other organic matter) and biological factors (such as viruses).

Endogenous factors are mainly harmful substances produced by normal cell metabolism, such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced by lipid peroxidation.

These two substances can cause oxidative stress and cell damage. DNA breaks can cause changes in genetic information and lead to many genetic diseases, tumors, etc.

Although DNA breakage occurs all the time, the body also has a powerful DNA repair mechanism, and DNA breakage and repair occur simultaneously during the DNA replication process.

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DNA repair depends on sleep?

Sleep plays an important role in DNA repair in brain cells.

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Although the body's DNA repair mechanism is always working, DNA damage occurs all the time. The longer you are awake, the more serious the DNA damage.

But DNA repair doesn't work as efficiently when you're awake, and it only kicks into high gear when you're asleep. Sleep activates our DNA repair system, so road maintenance workers can do a better job repairing roads at night when there's less traffic, for example.

Scientists have found that the chromosomes in the nerve cells of zebrafish move twice as fast when they are asleep than when they are awake. This movement allows damaged DNA to reorganize and repair itself. If zebrafish sleep for less than 6 hours, DNA damage is not fully reduced and they continue to sleep during the day.

The study found that a protein called PARP1 (poly ADP ribose polymerase 1) plays a key role in the DNA repair process. This protein can sense the increasing DNA damage during wakefulness, and if the damage reaches a certain threshold, it sends a signal to the brain to promote sleep and DNA repair, thereby reducing DNA breaks. Conversely, if PARP1 is inhibited, zebrafish will not go to sleep and DNA repair will not occur.

DNA repair methods include photorepair, excision repair, recombination repair and SOS repair. The most important and effective repair method is excision repair. Excision repair is the process of excision enzymes removing damaged DNA and then filling the gap with newly synthesized DNA.

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Studies have found that melatonin can increase the activity of genes related to the excision repair pathway, thereby repairing DNA breaks caused by oxygen free radicals. Staying up late will affect the secretion of melatonin, thereby affecting the ability to repair DNA. Over time, such DNA breaks will accumulate and the risk of diseases such as tumors, cardiovascular disease and dementia will also increase.

Why do humans sleep so long?

The larger the mammal, the less sleep it needs. Bats sleep 18 to 20 hours a day, and many large animals, such as giraffes, elephants, and horses, sometimes only sleep 3 to 4 hours. Generally speaking, adults need 7-9 hours of sleep a day. Why can't humans sleep only 4 hours like horses and use more time for work and play?

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There is no clear answer yet. Sleeping for 7-9 hours is mainly related to circadian rhythm and sleep homeostasis.

Circadian rhythm refers to the changes in life activities with a cycle of about 24 hours. During the evolution of humans, circadian rhythms were encoded into genes to form an endogenous timing system (biological clock). The biological clock controls the time of our sleep and wakefulness. At night, the brain releases melatonin, which makes people feel tired and fall asleep.

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The longer you are awake, the higher your body's need for sleep. This is sleep homeostasis. When we are awake, neurons in the brain produce adenosine. Adenosine is a byproduct of life. The accumulation of adenosine in the brain is an important factor in fatigue (caffeine blocks the activity of adenosine in the brain). When awake, the accumulation of adenosine promotes the drive to sleep. The longer you are awake, the higher the level of adenosine accumulation. During sleep, the body begins to clear adenosine.

Understand these theories

It allows us to sleep

Have a deeper understanding

so

Don't stay up late

Go to bed early.

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