Scientists at Washington University in St. Louis found that starvation allows the need for nourishment to push aside the need for sleep. Like humans and rats, fruit flies cannot survive without sleep. But in a line of flies engineered to be sensitive to sleep deprivation, starvation nearly tripled the amount of time they could survive without sleep.
Researchers showed that the ability to resist the effects of sleep loss was linked to a protein that helps the fruit fly brain manage its storage and use of lipids, a class of molecules that includes fats such as cholesterol and fat-soluble vitamins such as vitamins A and D.
"The major drugs we have to either put people to sleep or keep them awake are all targeted to a small number of pathways in the brain, all of them having to do with neurotransmission," says Paul Shaw, PhD, assistant professor of neurobiology and anatomy. "Modifying lipid processing with drugs may provide us with a new way of tackling sleep problems that is more effective or has fewer side effects."
The study appears online Aug. 31 in PLoS Biology.
The findings add a new wrinkle to the complex relationship between sleep and dietary metabolism. Scientists recognized about a decade ago that inadequate sleep results in obesity and contributes to the development of diabetes and coronary disease. Until now, no one had connected genes linked to lipids with regulation of the need for sleep.
Clay Semenkovich, MD, a Washington University lipid expert not directly involved in the study, says the results fit into a growing awareness that organisms use lipids for much more than energy storage.
"It's becoming apparent that fats serve as signaling molecules in a number of contexts," says Semenkovich, the Herbert S. Gasser Professor of Medicine. "If you identify the appropriate lipids involved in sleep regulation and figure out how to control them, you may be able to decrease suffering associated with loss of sleep or the need to stay awake."
Shaw uses fruit flies as models for sleep's effects in higher organisms. He was among the first to prove that flies enter a state comparable to sleep, showing that they have periods of inactivity where greater stimulation is required to rouse them. Like humans, flies deprived of sleep one day will try to make up for it by sleeping more the next day, a phenomenon referred to as sleep debt. Sleep-deprived flies also perform poorly on a simple test of learning ability.
Studies in other labs have shown that starvation or, in the case of human volunteers, fasting leads to less sleep. More recent research has also shown that starvation can change the activity levels of genes that manage storage and use of lipids.
Shaw's lab previously demonstrated that fruit flies with a mutation in a timekeeping gene accumulate sleep debt much more quickly and begin dying after being kept awake for as little as 10 hours. Matt Thimgan, PhD, a postdoctoral research associate, reports in the new paper that starving fruit flies spent more time awake, and starving fruit flies with the timekeeping gene mutation could survive up to 28 hours without sleep.
Scientists tested the starving, sleepless flies for two markers of sleep debt: an enzyme in saliva and the flies' ability to learn to associate a light with an unpleasant stimulus. Both tests showed that the starving flies were not getting sleepy.
"From an evolutionary perspective, this makes sense," Thimgan says. "If you're starving, you want to make sure you're on the top of your game cognitively, to improve your chances of finding food rather than becoming food for someone else."
Scientists found an effect similar to starvation in fruit flies where a gene called Lipid storage droplet 2 (LSD2) was disabled. After sleep deprivation, flies with the LSD2 mutation were less likely to sleep for longer periods of time and continued to score high on the learning test.
"LSD2 mutants seem to constantly rotate lipids through their storage depot in cells, putting them in and moving them out very quickly," Thimgan says. "Disabling LSD2 appears to make it hard for cells to hold on to lipids and use them properly, and we think this impairs brain cells' ability to respond to sleep deprivation."
Researchers are working to identify the specific lipids affected by loss of LSD2.
Thimgan MS, Suzuki Y, Seugnet L, Gottschalk L, Shaw PJ. The Perilipin homologue, Lipid storage droplet 2, regulates sleep homeostasis and prevents learning impairments following sleep loss. PLoS Biology, Aug. 31, 2010.
Funding from the National Institutes of Health and the WM Keck Foundation supported this research.
Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.
Michael C. Purdy | Newswise Science News
The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences
Transforming plant cells from generalists to specialists
07.12.2016 | Duke University
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
07.12.2016 | Health and Medicine
07.12.2016 | Life Sciences
07.12.2016 | Health and Medicine