Lonely flies, like many humans, eat more and sleep less

Date:
August 18, 2021
Source:
Rockefeller University
Summary:
Single fruit flies quarantined in test tubes sleep too little
and eat too much after only about one week of social isolation,
according to a new study.



FULL STORY ========================================================================== COVID-19 lockdowns scrambled sleep schedules and stretched waistlines. One culprit may be social isolation itself. Scientists have found that lone
fruit flies quarantined in test tubes sleep too little and eat too much
after only about one week of social isolation, according to a new study published in Nature. The findings, which describe how chronic separation
from the group leads to changes in gene expression, neural activity,
and behavior in flies, provide one of the first robust animal models
for studying the body's biological reaction to loneliness.


========================================================================== "Flies are wired to have a specific response to social isolation," says
Michael W. Young, the Richard and Jeanne Fisher Professor and head of
the Laboratory of Genetics at Rockefeller. "We found that loneliness
has pathological consequences, connected to changes in a small group of neurons, and we've begun to understand what those neurons are doing."
The science of loneliness Drosophila are social creatures. The fruit
flies forage and feed in groups, serenade one another through complex
mating rituals, tussle in miniature boxing matches. And then they conk
out: flies sleep 16 hours each day, split between a languorous midday
nap and a full night's rest.

So when Wanhe Li, a research associate in Young's lab, began investigating
the biological underpinnings of chronic social isolation, she turned
to the gregarious and well-studied fruit fly. "Over and over again,
Drosophila have put us on the right track," says Young. "Evolution
packed a great deal of complexity into these insects long ago and,
when we dig into their systems, we often find the rudiments of something
that is also manifest in mammals and humans." "When we have no roadmap,
the fruit fly becomes our roadmap," Li adds.



==========================================================================
For the study, Wanhe Li first compared how flies fare under various
lockdown conditions. After seven days, flies housed together in groups
of varying sizes produced no anomalous behaviors. Even two flies cut off
from the crowd were content with one another. But when a single fly was entirely isolated, the lonely insect began eating more and sleeping less.

Further investigation revealed that a group of genes linked to
starvation were expressed differently in the brains of lonely flies --
a tempting genetic basis for the observed connection between isolation
and overeating.

Li then found that a small group of brain cells known as P2 neurons were involved in the observed changes to sleep and feeding behavior. Shutting
down the P2 neurons of chronically-isolated flies suppressed overeating
and restored sleep; boosting P2 in flies isolated from the group for
only one day caused them to eat and sleep as if they had been alone for
a full week.

"We managed to trick the fly into thinking that it had been chronically isolated," says Wanhe Li. "The P2 neurons seem to be linked to the
perception of the duration of social isolation, or the intensiveness of loneliness, like a timer counting down how long the fly has been alone."
The Young lab painstakingly confirmed these observations. They engineered insomniac flies, to make sure that lack of sleep alone did not cause
overeating (it didn't). They tested group-reared flies to find out
whether manipulating P2 neurons would cause overeating and sleep loss
in socialized flies (it doesn't).

Ultimately, they concluded that only a perfect storm of both P2 neuron
activity and social isolation will cause flies to begin to losing sleep
and overeating.

Explaining the "Quarantine 15" Scientists have observed that many social animals -- from fruit flies to humans -- eat more and sleep less when
isolated. The reason for this is unclear. One possibility, Young says,
is that social isolation signals a degree of uncertainty about the
future. Preparation for tough times may include being alert and awake
as often as possible and eating whenever food is available.

This study can hardly confirm that humans in COVID-19 lockdowns ate
more and slept less due to the same biological mechanisms that keep
lonely flies hungry and sleep deprived. But now that Li and Young have identified the neurons and genes responding to chronic isolation in
fruit flies, future researchers can search for corresponding connections between loneliness, overeating, and insomnia in laboratory animals and, eventually, humans.

"Clinically-oriented studies suggest that a large number of adults in
the United States experienced significant weight gains and loss of sleep throughout the past year of isolation precautions due to COVID-19," Young
says. "It may well be that our little flies are mimicking the behaviors
of humans living under pandemic conditions for shared biological reasons." ========================================================================== Story Source: Materials provided by Rockefeller_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Wanhe Li, Zikun Wang, Sheyum Syed, Cheng Lyu, Samantha Lincoln,
Jenna
O'Neil, Andrew D. Nguyen, Irena Feng, Michael W. Young. Chronic
social isolation signals starvation and reduces sleep in
Drosophila. Nature, 2021; DOI: 10.1038/s41586-021-03837-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210818130604.htm

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