Glial cells may play key role in managing sleep and metabolism, fruit fly study suggests

Homeostasis is the ability of living organisms to maintain stable internal conditions, such as temperature, hydration and blood sugar levels, irrespective of any changes in their surroundings. Homeostatic mechanisms also regulate behaviors that are central to the survival of animal species, such as sleep, rest and eating.

Researchers at the Max Planck Institute for Neurobiology of Behavior–Caesar (MPINB) in Germany recently carried out a study aimed at better understanding the neural underpinnings of rest, sleep and feeding behavior in fruit flies (Drosophila melanogaster).

Their findings, published in Nature Neuroscience, highlight the key role of glia (non-neuronal cells in the brain and nervous system with different specialized functions) in regulating these vital mechanisms in fruit flies, suggesting that they serve as metabolic homeostats.

“Humans spend about a third of their lives sleeping, yet we still don’t fully understand why sleep is necessary,” Andres Flores-Valle, first author of the paper, told Medical Xpress “Our research aims to answer this question by studying fruit flies, which despite having much simpler brains, also sleep. Their simplicity and the powerful genetic tools available make them ideal for understanding the basic functions of sleep.”

As part of their recent study, Flores-Valle and his colleagues specifically set out to uncover a brain signal that tracks the need for sleep (i.e., sleep homeostasis) in fruit flies. This signal should increase as a fly becomes more tired and reset after a period of restful sleep.

“Understanding the mechanisms behind sleep homeostasis can potentially provide answers for why sleep is necessary,” explained Flores-Valle. “We used in vivo imaging to record glial and neural activity in awake and sleeping flies under a microscope,” explained Flores-Valle.

“To do this, we kept flies comfortable and fed them every few hours using a robot. We did this over several days, allowing them to sleep naturally under the microscope.”

In their experiments, the researchers examined two distinct types of glia cells, known as astrocyte-like glia and ensheathing glia. The first are known to serve similar functions to astrocytes, thus helping to maintain a stable chemical environment in the brain. The second are cells that wrap around axons, contributing to their regeneration and to the removal of axon residues or damaged cells.

Notably, Flores-Valle and his colleagues were the first to record the brain activity of flies for extended periods, while also ensuring their comfort during rest. The experimental methods they employed ultimately allowed them to intermittently observe the insects while they were asleep and awake.

“We found that glial cells track sleep need through calcium signals that rise during wakefulness and reset with sleep,” said Flores-Valle. “Surprisingly, we discovered that neurons thought to trigger sleep instead tracked feeding need, with activity rising until the fly eats.

“We also found that glial calcium activity is linked to metabolism—helping clear CO₂ and regulate pH- suggesting sleep may be needed to restore metabolic balance.”

The findings gathered by the researchers show that glial cells respond to metabolic signals and these responses influence their calcium activity. Overall, these results link the activity of glial cells to metabolic states and the regulation of sleep. In the future, they could inspire further research focusing on the contribution of glia to sleep, which could also improve the understanding of sleep and metabolic disorders.

“Our next studies will try to uncover how glial cells trigger the transition from wakefulness to sleep, a key question that remains unanswered,” added Flores-Valle. “We suspect that elevated calcium activity in glia after prolonged wakefulness helps initiate sleep, but how the signal acts across the brain is still unknown.”

© 2025 Science X Network

Homeostasis is the ability of living organisms to maintain stable internal conditions, such as temperature, hydration and blood sugar levels, irrespective of any changes in their surroundings. Homeostatic mechanisms also regulate behaviors that are central to the survival of animal species, such as sleep, rest and eating.

Researchers at the Max Planck Institute for Neurobiology of Behavior–Caesar (MPINB) in Germany recently carried out a study aimed at better understanding the neural underpinnings of rest, sleep and feeding behavior in fruit flies (Drosophila melanogaster).

Their findings, published in Nature Neuroscience, highlight the key role of glia (non-neuronal cells in the brain and nervous system with different specialized functions) in regulating these vital mechanisms in fruit flies, suggesting that they serve as metabolic homeostats.

“Humans spend about a third of their lives sleeping, yet we still don’t fully understand why sleep is necessary,” Andres Flores-Valle, first author of the paper, told Medical Xpress “Our research aims to answer this question by studying fruit flies, which despite having much simpler brains, also sleep. Their simplicity and the powerful genetic tools available make them ideal for understanding the basic functions of sleep.”

As part of their recent study, Flores-Valle and his colleagues specifically set out to uncover a brain signal that tracks the need for sleep (i.e., sleep homeostasis) in fruit flies. This signal should increase as a fly becomes more tired and reset after a period of restful sleep.

“Understanding the mechanisms behind sleep homeostasis can potentially provide answers for why sleep is necessary,” explained Flores-Valle. “We used in vivo imaging to record glial and neural activity in awake and sleeping flies under a microscope,” explained Flores-Valle.

“To do this, we kept flies comfortable and fed them every few hours using a robot. We did this over several days, allowing them to sleep naturally under the microscope.”

In their experiments, the researchers examined two distinct types of glia cells, known as astrocyte-like glia and ensheathing glia. The first are known to serve similar functions to astrocytes, thus helping to maintain a stable chemical environment in the brain. The second are cells that wrap around axons, contributing to their regeneration and to the removal of axon residues or damaged cells.

Notably, Flores-Valle and his colleagues were the first to record the brain activity of flies for extended periods, while also ensuring their comfort during rest. The experimental methods they employed ultimately allowed them to intermittently observe the insects while they were asleep and awake.

“We found that glial cells track sleep need through calcium signals that rise during wakefulness and reset with sleep,” said Flores-Valle. “Surprisingly, we discovered that neurons thought to trigger sleep instead tracked feeding need, with activity rising until the fly eats.

“We also found that glial calcium activity is linked to metabolism—helping clear CO₂ and regulate pH- suggesting sleep may be needed to restore metabolic balance.”

The findings gathered by the researchers show that glial cells respond to metabolic signals and these responses influence their calcium activity. Overall, these results link the activity of glial cells to metabolic states and the regulation of sleep. In the future, they could inspire further research focusing on the contribution of glia to sleep, which could also improve the understanding of sleep and metabolic disorders.

“Our next studies will try to uncover how glial cells trigger the transition from wakefulness to sleep, a key question that remains unanswered,” added Flores-Valle. “We suspect that elevated calcium activity in glia after prolonged wakefulness helps initiate sleep, but how the signal acts across the brain is still unknown.”

© 2025 Science X Network