Editor's Note
This article was compiled by the Time School Institute from Longevity Technology's report on Professor Lior Appelbaum.
Everyone knows that sleeping is important, but has anyone ever wondered why we should sleep? Professor Lior Appelbaum of Bayland University in Israel has made great achievements in sleep research and has participated in the publication of nearly 100 related papers. In this paper, Professor Appelbaum will answer how sleep affects DNA repair in individual neurons, how sleep deprivation and neurodegenerative diseases are associated, and point out the optimal sleep duration derived from animal models. After reading this article, you may have a new understanding of the opening question.
Original link:
https://www.longevity.technology/
does-dna-repair-explain-the-link-between-sleep-and-longevity/
Sleep, the fundamental of human existence, the habit of sharing all things. Birds and animals, fish and insects, as long as there is a nervous system in the body, they are indispensable to sleep. If you look closely, sleep is essentially counterintuitive, not conducive to survival and evolution. Because once the animals are asleep, they are more likely to fall into the mouth of the tiger and become the hunter's plate. If so, why do we sleep?
Understand sleep in a whole new light
Most people agree that sleeping is for the benefit of the brain or nervous system, and that "brain states" during sleep manifest themselves as interactions between networks of neurons. The importance of sleep for learning and memory is also a cliché, and lack of sleep can lead to poor performance and poor grades.
However, Professor Appelbaum and his team believe that the most direct benefit from sleep is the individual neurons, which can explain why jellyfish, worms and other very simple neural network organisms also sleep. Individual neurons are connected to each other into a network, and the entire network of neurons benefits from it.
"Jellyfish don't need to consolidate their memories and take exams, so why should they sleep?" That's where our research starts," says Professor Appelbaum.
With this question in mind, the Appelbaum team set out to find a suitable animal model. Studying individual neurons in living mammals is challenging because there is skull protection outside the brain, which is already complicated to reach. Eventually, the researchers selected zebrafish as their subjects. This vertebrate embryo is transparent, develops in vitro, and is easy to observe; its brain is relatively simple, and its structure and function are consistent with the human brain, so it is the best choice for studying the real-time changes of individual neurons.
Photo note: Zebrafish in an experimental environment
Source: Dr. Sarah De Val, University of Oxford
Sleep promotes DNA repair within neurons
With the help of a variety of tools, scientists have succeeded in noninvasive observation of individual cells in living animals. Applying this technique, the researchers made breakthroughs in observing the activity of individual neurons in zebrafish. The experimental results are as follows:
Discovery 1:
DNA damage in neurons increases when zebrafish are awake and decrease when they sleep
DNA damage occurs all the time in various cells of the organism, and there are many corresponding repair mechanisms. The peculiarity of DNA damage within neurons is that when the organism is awake, the repair rate < damage rate, so the damage will continue to increase, and the repair process can only prevail when it is asleep.
Sleep deprivation exacerbates DNA damage in neurons, and the only solution is to return to normal sleep patterns. It is worth noting that sleep is inextricably linked to repair only in neurons. So what's so special about neurons?
Neurons are non-dividing cells, and the traditional view of neurology is that neurons in the adult brain are difficult to regenerate, so they are needed and used and cherished. But in recent years, a number of experiments have proposed a basis for neuronal regeneration. Professor Appelbaum believes that this may explain why we have evolved the habit of sleeping, "sleeping creates a period of time for the brain to shut down, gives neurons a chance to overhaul and maintain, and these tasks seem to be forced to be done during shutdown." ”
Discovery 2:
The PARP1 gene is a "sleep switch"
PARP1 senses and marks DNA damage in neurons, and as DNA damage increases, PARP1 becomes more numerous, suggesting that it's time for the brain to go to sleep. In the experiment, zebrafish went to sleep when the researchers controlled PARP1 overexpression, and when they turned down PARP1 expression, zebrafish remained awake due to lack of prompts.
Sleep and neurodegenerative diseases
What does the experimental data from zebrafish inspire human longevity?
Studies have shown that long-term sleep deprivation and sleep disorders* can exacerbate DNA damage and increase the risk of neurodegenerative diseases. Sleep deprivation is divided into acute and chronic, acute complete sleep deprivation refers to not sleeping at all for 24 to 48 hours, and chronic incomplete sleep deprivation is a reduction in sleep time). Recent studies have also found that Alzheimer's disease, Parkinson's syndrome and amyotrophic lateral sclerosis (ASL) are all associated with sleep disorders.
"If you don't sleep well, the DNA damage in the neurons will increase," explains Professor Appelbaum, "if the long-term sleep condition is very bad, the damage is likely to lead to cell death, and eventually lead to various neurodegenerative diseases." ”
"Our experiments demonstrate a correlation between chronic sleep deprivation and DNA damage, which is one of the hallmarks of aging, in other words, poor sleep is closely related to accelerated aging." However, Professor Appelbaum also admitted, "After all, this experiment is aimed at zebrafish, and it is difficult for humans to regulate DNA damage to observe its impact on sleep." ”
How long does it take to sleep enough to repair DNA?
Over the years, there have been many opinions about optimal sleep duration. Although Professor Appelbaum can't give an answer to the optimal amount of sleep for humans, he's pretty sure how long zebrafish should sleep.
Zebrafish are very sensitive to light, so they can be controlled by adjusting the brightness to wake up or fall asleep. In the experiment, the Appelbaum team found that if zebrafish were allowed to sleep only for 2 to 4 hours, the level of DNA damage would be high. But after 6 hours of sleep, dna damage returns to normal levels. Therefore, for zebrafish, 6 hours is the best sleep time to meet DNA repair. Moreover, the length of sleep is not the more the merrier, and in the experiment, 8 to 10 hours of sleep did not further improve the repair effect of DNA.
The future direction of sleep research
There are still many questions left for Professor Appelbaum and his team to continue exploring. For example, how does the brain know that dna in a particular neuron needs to be repaired? Not every neuronal cell is directly linked to sleep, so Professor Appelbaum speculates that there is a threshold for cellular damage, and when enough neurons accumulate damage to reach this threshold, the brain receives a signal to go to sleep, creating conditions for repair work.
Another question about neurons that are still active while we are asleep, such as those that control dreaming, when do they rest? "Maybe when we're awake, these neurons are resting," Says Professor Appelbaum, "and the next step is for us to replicate the zebrafish experiment in other vertebrates and incorporate the questions we just mentioned into the next study." We will also try to cooperate with hospitals to conduct human experiments to see if the results can also be applied to humans. ”
Although Professor Appelbaum's research has only focused on the little zebrafish for the time being, we already know that when it comes to sleeping, everything is mysterious and beneficial. A good night's sleep for DNA automatic repair, lying down can move towards longevity, why not?
—— TIMEPIE ——
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