Study finds new mechanism for regulating sleep in fruit flies using an ingredient commonly found in energy drinks – ScienceDaily

There is growing evidence that glial cells (or glia), long thought to simply "support" neurons within the brain, are actually quite important for various aspects of sleep regulation. Thanks to the fruit fly (Drosophila melanogaster), research teams at Florida Atlantic University and McGill University in Quebec.

Fruit flies share 75 percent of the genes that cause diseases in humans and display all of the behavioral and physiological characteristics of sleep. For the study, published in the journal Current Biology, the researchers sought to identify new genes affecting sleep and wakefulness in fruit flies. With this approach, they uncovered a gene that encodes the membrane transport protein known as excitatory amino acid transporter 2 or Eaat2.

They found that Eaat2 promotes wakefulness in fruit by limiting the length and intensity of sleep periods. They also discovered that by controlling the movement of taurine – the ingredient found in many energy drinks – in glial cells of the fly brain. In humans, taurine is consistently elevated in blood and urine of sleep-deprived people, but it is unknown if taurine levels also change in the brain after sleep deprivation.

Like humans, fruit flies are highly active during the day and sleep throughout the night. The authors found that disruption of Eaat2 in fruit flies caused excessive daytime sleepiness.

"Daytime sleep is more fragmented than nighttime sleep, and disrupting sleep," said Bethany A. Stahl, Ph.D., lead author on the study and a post- Alex C. Keene, Ph.D., Associate Professor of Biological Sciences in FAU's Charles E. Schmidt College of Science and a member of the Jupiter Life Science Initiative (JSLI).

"About 70 million Americans suffer from sleep disorders, and we believe that this is an important issue globally," said Keene.

To determine the role of Eaat2 in metabolic regulation, the researchers simultaneously measured sleep and CO? output from single flies.

"We think of the identification of sleep cessation, sleep-dependent changes in metabolism, and the need for sleep disorders," said Keene. "It suggests sleep researchers need to look beyond the role of neurons to examine how glial cells control our sleep-wake regulation."

The team found that Eaat2 works in specific glial cells of the fly brain, rather than in neurons.

"" This research adds wakefulness to the growing list of important behaviors, which includes circadian rhythms, movement, courtship, learning and memory, "said Emilie Peco, Ph.D., who co-led the Dr. Don van Meyel, Ph.D., Professor of Neurology at the McGill Center for Research in Neuroscience, and the BRaIN Program of the Research Institute at the McGill University Health Center.

Eaat2 was previously shown to transport taurine. So to test if taurine could explain how Eaat2 affects sleep, Stahl fed taurine to some flies and found it more flies, but only if Eaat2 was present.

"The study led by Dr. Stahl and Dr. Peco focuses on fundamental mechanisms of sleep and glial cells in flies, but we expect in humans, "said van Meyel. "Even if you do not indulge in energy drinks, there is a lot of taurine in the human brain, and it is not all that well."

Study co-authors are Sejal Davla, PhD, McGill University; and Kazuma Murakami, Ph.D., and Nicholas A. Caicedo Moreno, Ph.D., both at FAU. The collaboration between the teams at FAU and McGill has been developed organically from the Keene lab's focus on sleep research and the van Meyel lab's expertise in glial cells and membrane transport proteins.

This work was supported by the National Institutes of Health (NIH), the Canadian Institutes of Health Research (CIHR), the Natural Sciences and Engineering Research Council of Canada, and the Canada Foundation for Innovation.

JLSI is a FAU's John D. MacArthur Campus in Jupiter, and is a collaborative effort between the Charles E. Schmidt College of Science and the Harriet L. Wilkes Honors College.