Nav: Home

International research team finds brain changes linked to sleep need

June 14, 2018

DALLAS - June 13, 2018 - We've all experienced going to bed tired and waking up refreshed, yet how that happens at the molecular level remains a mystery. An international study published today in Nature sheds new light on the biochemistry of sleep need in the brain.

According to the American Sleep Association, 50 million to 70 million U.S. adults have a sleep disorder with almost 1 in 3 experiencing short-term insomnia and about 1 in 10 suffering from chronic insomnia. Sleep loss is known to compromise thinking and decision-making, which decreases work performance and productivity while increasing the risk of auto and industrial accidents. Understanding sleep regulators could benefit society by leading to the development of novel, more effective treatments for sleeplessness.

The new research reports the first whole-brain, quantitative study of a fundamental molecular process called phosphorylation in the context of sleep need. It features a clever comparison of two different groups of tired mice: sleep-deprived normal mice and Sleepy mutant mice, a variety with a genetic mutation that confers an unusually high sleep need despite increased sleep amount.

The Sleepy mouse was identified in a collaborative study between Dr. Masashi Yanagisawa and Dr. Joseph Takahashi initiated at UT Southwestern's Peter O'Donnell Jr. Brain Institute, where Dr. Takahashi is Chair of Neuroscience, a Howard Hughes Medical Institute Investigator, and holder of the Loyd B. Sands Distinguished Chair in Neuroscience. Dr. Yanagisawa, Director of the University of Tsukuba's International Institute for Integrative Sleep Medicine (WPI-IIIS) in Japan, is a Professor of Molecular Genetics at UT Southwestern. Dr. Yanagisawa and Dr. Qinghua Liu, an Associate Professor in UTSW's Center for the Genetics of Host Defense and of Neuroscience, are two of the study's three corresponding authors. Dr. Liu also has joint appointments at the WPI-IIIS and at the National Institute of Biological Sciences (NIBS) in Beijing.

"Although sleep exists in all animals, why sleep is needed and how sleep is regulated remain a mystery. We set out to investigate the molecules that govern sleep need (or sleep pressure)," said Dr. Liu, a W.A. "Tex" Moncrief Jr. Scholar in Medical Research. Sleep need is the feeling of tiredness that builds up during waking hours, he said.

Dr. Joseph Takahashi describes the 2016 study from the Peter O'Donnell Jr. Brain Institute that identified the Sleepy mouse.

"Each animal exhibits a set point of total sleep time. In adult humans, that usually means about 8 out of 24 hours. Everyone has experienced staying up too late and feeling a need to 'make up for lost sleep.' Even simple jellyfish need to rest longer after being forced to remain awake," he said, adding that it has been hypothesized that a substance accumulates in the brain during waking and dissipates during sleep.

"A long-term goal in sleep research is to identify the actual molecular factor or factors involved in sleep need," he said. Currently, the majority of sleep medicines are mimics of GABA, an inhibitory neurotransmitter that simply shuts off the brain, and they induce nonnatural sleep with many side effects. It would be nice to understand the natural molecules better in order to design improved treatments for sleep problems, he added.

To study the molecules involved in sleep need, researchers devised a novel strategy of comparing phosphorylation in the brains of the sleep-deprived normal mice and Sleepy mutant mice. Phosphorylation is a reversible process that modifies the functions of proteins by adding a phosphate group. The novel strategy comparing the two mice - one sleepy by circumstance, the other sleepy by nature - made it possible to exclude variables such as stress that could affect sleepiness, the researchers explained.

Using immunochemical assays and mass spectrometry, the researchers identified 80 proteins that were hyperphosphorylated in the brains of sleep-deprived and Sleepy mice, meaning that the proteins accumulated more phosphate groups the longer the mice stayed awake. They named these proteins Sleep-Need-Index-Phosphoproteins (SNIPPs). They found that the phosphorylation of SNIPPs increased with sleep need and dissipated, or dephosphorylated, throughout the brain during sleep.

"Previous studies suggested a close link between sleep need and synaptic plasticity (the strengthening and weakening of synaptic connections between neurons that is linked to thinking and learning). Intriguingly, the majority of SNIPPs are synaptic proteins, including many regulators of synaptic plasticity," Dr. Liu said.

He added that a literature search found that mutations of multiple SNIPPs have been linked to changes in sleep need. "Thus, we propose that SNIPPs constitute the molecular link between synaptic plasticity and regulation of sleep need or, in lay terms, between thinking and sleepiness," he said.

"The purpose of sleep-wake balance appears to be to maximize the duration and quality of cognitive (thinking) functions of the brain. While prolonged wakefulness leads to cognitive impairment and sleepiness, sleep refreshes the brain through multiple restorative effects and optimizes cognitive functions for the next waking period," he said. Therefore, the phosphorylation/dephosphorylation cycle of SNIPPs may be an important way for the brain to reset itself every night, restoring both synaptic and sleep-wake balance to maximize clear thinking, he added.
-end-
The study received support from The Welch Foundation, the National Institutes of Health, and the World Premier International Research Center Initiative program from Japan's MEXT (Ministry of Education, Culture, Sports, Science and Technology).

The study's UTSW co-author is Dr. Yonghao Yu, Associate Professor of Biochemistry, a CPRIT scholar in Cancer Research, and a Virginia Murchison Linthicum Scholar in Medical Research. Researchers from St. Jude Children's Research Hospital, Memphis, Tennessee; the NIBS; Tsinghua University, Beijing; and Toho University, Tokyo, also participated in the study.

About UT Southwestern Medical Center

UT Southwestern, one of the premier academic medical centers in the nation, integrates pioneering biomedical research with exceptional clinical care and education. The institution's faculty has received six Nobel Prizes, and includes 22 members of the National Academy of Sciences, 16 members of the National Academy of Medicine, and 15 Howard Hughes Medical Institute Investigators. The faculty of more than 2,700 is responsible for groundbreaking medical advances and is committed to translating science-driven research quickly to new clinical treatments. UT Southwestern physicians provide care in about 80 specialties to more than 100,000 hospitalized patients, 600,000 emergency room cases, and oversee approximately 2.2 million outpatient visits a year.

UT Southwestern Medical Center

Related Sleep Articles:

To sleep deeply: The brainstem neurons that regulate non-REM sleep
University of Tsukuba researchers identified neurons that promote non-REM sleep in the brainstem in mice.
Chronic opioid therapy can disrupt sleep, increase risk of sleep disorders
Patients and medical providers should be aware that chronic opioid use can interfere with sleep by reducing sleep efficiency and increasing the risk of sleep-disordered breathing, according to a position statement from the American Academy of Sleep Medicine.
'Short sleep' gene prevents memory deficits associated with sleep deprivation
The UCSF scientists who identified the two known human genes that promote 'natural short sleep' -- nightly sleep that lasts just four to six hours but leaves people feeling well-rested -- have now discovered a third, and it's also the first gene that's ever been shown to prevent the memory deficits that normally accompany sleep deprivation.
Short sleep duration and sleep variability blunt weight loss
High sleep variability and short sleep duration are associated with difficulties in losing weight and body fat.
Nurses have an increased risk of sleep disorders and sleep deprivation
According to preliminary results of a new study, there is a high prevalence of insufficient sleep and symptoms of common sleep disorders among medical center nurses.
Opioids are not sleep aids, and can actually worsen sleep research finds
Evidence that taking opioids will help people with chronic pain to sleep better is limited and of poor quality, according to an interdisciplinary team of psychologists and medics from the University of Warwick in partnership with Lausanne University Hospital, Switzerland.
Common sleep myths compromise good sleep and health
People often say they can get by on five or fewer hours of sleep, that snoring is harmless, and that having a drink helps you to fall asleep.
Sleep tight! Researchers identify the beneficial role of sleep
Why do animals sleep? Why do humans 'waste' a third of their lives sleeping?
Does extra sleep on the weekends repay your sleep debt? No, researchers say
Insufficient sleep and untreated sleep disorders put people at increased risk for metabolic problems, including obesity and diabetes.
Kicking, yelling during sleep? Study finds risk factors for violent sleep disorder
Taking antidepressants for depression, having post-traumatic stress disorder or anxiety diagnosed by a doctor are risk factors for a disruptive and sometimes violent sleep disorder called rapid eye movement (REM) sleep behavior disorder, according to a study published in the Dec.
More Sleep News and Sleep Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Space
One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at Radiolab.org/donate.