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Association between obesity and lack of sleep

Association between obesity and lack of sleep
According to the latest research on worms, saving energy may be the main function of sleep.





Will staying up late make you fat? More and more studies have shown that decreased sleep quality is associated with increased loss of appetite and increased risk of obesity, which in turn leads to more calorie consumption.

But a new study published this week in the journal PLOS Biology found that the direction of this response may actually be reversed. Researchers from the University of Pennsylvania Perelman School of Medicine and the University of Nevada-Reno said that they found in the study of C. elegans that it is not that lack of sleep leads to obesity, but obesity leads to lack of sleep .

David Raizen, MD, associate professor of neurology and member of the Pennsylvania Institute of Chronology Biology and Sleep, said, "We think sleep is a function of the body trying to save energy when energy levels drop. The results of the study show that if you want to fast for a day , We can predict that you will be sleepy because your energy storage will be exhausted. "

Raizen emphasized that although the findings of these worms may not directly translate into humans, C. elegans provides a surprisingly good model for studying mammalian sleep. Like all other animals with nervous systems, they need sleep. But unlike humans, humans have complex neural circuits that are difficult to study, and Caenorhabditis elegans has only 302 neurons, and scientists have determined that one of them is a sleep regulator.

Acute sleep disruption in humans can lead to increased appetite and insulin resistance, and people who sleep for less than six hours per night for a long time are more likely to be obese and have diabetes. In addition, in humans, rats, fruit flies, and worms, hunger has also been shown to affect sleep, suggesting that sleep is at least partially regulated by nutrient supply, but the mode of synergy between sleep and diet is still unclear.

Dr. Alexander van der Linden, co-author of the study and associate professor of biology at the University of Nevada Reno, said, "We want to know, what is the actual role of sleep? Lack of sleep is related to other chronic diseases such as diabetes, but this is only Correlation. It is unclear whether lack of sleep leads to obesity, perhaps obesity leads to lack of sleep. "

To study the relationship between metabolism and sleep, the researchers genetically modified C. elegans to "turn off" neurons that control sleep. These worms can still eat, breathe and reproduce, but they lose their ability to sleep. As the neuron was shut down, the researchers saw a serious drop in adenosine triphosphate (ATP) levels, which is the body's energy currency.

Raizen explained, "This shows that sleep is to save energy, and in fact does not cause energy loss."

In previous research, the Van der Linden laboratory studied a gene called KIN-29 in C. elegans. This gene is homologous to the human salt-inducible kinase (SIK-3) gene, which is known to emit sleep stress signals. Surprisingly, when the researchers knocked out the KIN-29 gene to create an insomnia worm, even if its ATP content is reduced, the mutant C. elegans will still accumulate too much fat, similar to human obesity.

The researchers hypothesized that the release of fat stores is a mechanism that promotes sleep , and the reason for the insomnia of KIN-29 mutants is that they cannot release fat. To test this hypothesis, the researchers again manipulated the KIN-29 mutant worm, this time expressing an enzyme capable of releasing its fat. Through this operation, the worms can fall asleep again.

Raizen said this may explain one of the reasons why obesity patients may experience sleep problems-there may be signal transmission problems between fat storage and brain cells that control sleep.

Although there are still many problems to be solved in sleep, this paper gives the industry a closer look at its core functions and how to treat common sleep disorders.

"There is a general view in the field of sleep that sleep is all about the brain or nerve cells, and our work shows that this is not necessarily correct," Raizen said. Interaction, which is related to sleep regulation. "

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