Protein and salt drive post-meal sleepiness

November 22, 2016, eLife
Large, salty, or protein-rich meals induce post-meal sleep in fruit flies. Credit: Keith Murphy

Sleepiness after a large meal is something we all experience, and new research with fruit flies suggests higher protein and salt content in our food, as well as the volume consumed, can lead to longer naps.

Writing in the journal eLife, scientists from The Scripps Research Institute, US, have for the first time found a way to study 'food comas' in the fruit fly Drosophila melanogaster and explained some of the causes behind this phenomenon.

They created a system that can measure both the and feeding behaviors of individual fruit and discovered that, in much the same way as humans, the animals sleep for longer periods following larger meals. Further studies also revealed that certain types of food can promote post-meal sleep.

"In Drosophila, there is a well-documented interaction between sleep and metabolism, whereby flies suppress sleep or increase their activity when starved," says senior author William Ja, PhD, Associate Professor in the Department of Metabolism and Aging at Scripps Florida. "However, the acute effects of on sleep have not yet been tested, largely because there was no system available to do so."

To better understand this relationship, Ja and his team created the Activity Recording CAFE (ARC), the first system for flies that enables visual tracking of food consumption and animal motion. Recordings of ' behavior from this system reveal that, after eating a meal, the animals sleep more before returning to a normal state of wakefulness. The sleep period generally lasts around 20 to 40 minutes, with flies that eat larger portions generally sleeping more.

To determine if individual nutrients could modulate post-meal sleep, the team gave the flies food consisting of protein, salt or sugar. They found that only protein and salt were effectors of post-meal sleep, suggesting that this form of sleep can indeed be regulated by specific food types.

"We next sought to identify a neuronal mechanism by which feeding drives post-meal sleep," explains first author Keith Murphy. "By using genetic tools to turn neurons on and off in the fly brain, we were surprised to find a number of circuits that play a role in controlling this behavior."

A previous study has shown that leucokinin (Lk) neurons are involved in meal-size regulation, indicating that this system acts rapidly during feeding to signal a behavioral shift. Building on this work, the authors of the current study demonstrate that the Lk system plays a role in post-meal sleep.

"A subset of leucokinin receptor (Lkr) neurons was necessary to initiate post-meal sleep in the presence of protein specifically," Murphy says. "While we expected that flies defective in protein sensing would experience post-meal sleep in a similar way to those fed only sucrose, we found instead that they had a waking response. Our analysis suggests that ingested protein promotes both sleep and wakefulness, and that the wakefulness is counterbalanced by Lkr neuronal activity."

They also found that other brain circuits are sensitive to the fruit fly's internal clock, reducing post-meal sleepiness only around dusk. Taking these results together, the team concludes that post-meal sleepiness can be regulated in a number of different ways in flies and humans alike.

"The ARC provides a starting point for future studies aimed at uncovering the exact genes and circuits that enable meal size, protein and salt to drive sleep," Ja adds. "As sleep is a vulnerable state for animals in nature, it will be interesting to discover why post-meal naps are necessary."

Explore further: Sleep tight—gene responsible for sleep deprivation and metabolic disorders identified

More information: Keith R Murphy et al, Postprandial sleep mechanics in Drosophila, eLife (2016). DOI: 10.7554/eLife.19334

Related Stories

Sleep tight—gene responsible for sleep deprivation and metabolic disorders identified

March 24, 2016
The sleep habits of fruit flies are remarkably similar to humans. They get most of their sleep at night, certain drugs and stimulants like caffeine can negatively affect their sleep, and if they get a lousy night's sleep ...

Study unpeels one layer of the mystery of sleep as they develop understanding of the sleep homeostat

August 3, 2016
Oxford University researchers have discovered what causes a switch to flip in our brains and wake us up. The discovery, published in the journal Nature, brings us closer to understanding the mystery of sleep.

Drowsy Drosophila shed light on sleep and hunger

October 3, 2013
Why does hunger keep us awake and a full belly make us tired? Why do people with sleep disorders such as insomnia often binge eat late at night? What can sleep patterns tell us about obesity?

Recommended for you

Team develops new approach to study long non-coding RNAs

April 19, 2018
Until recently, scientific research concentrated almost exclusively on the 2 percent of the genome's protein coding regions, virtually ignoring the other 98 percent - a vast universe of non-coding genetic material previously ...

Molecule that dilates blood vessels hints at new way to treat heart disease

April 19, 2018
Americans die of heart or cardiovascular disease at an alarming rate. In fact, heart attacks, strokes and related diseases will kill an estimated 610,000 Americans this year alone. Some medications help, but to better tackle ...

Enduring cold temperatures alters fat cell epigenetics

April 19, 2018
A new study in fat cells has revealed a molecular mechanism that controls how lifestyle choices and the external environment affect gene expression. This mechanism includes potential targets for next-generation drug discovery ...

Leptin's neural circuit identified—Genome-editing study reveals how hormone helps prevent both obesity and diabetes

April 18, 2018
Revealing surprising answers to a long-standing enigma about the brain target of the anti-obesity hormone leptin, neuroscientists at Tufts University School of Medicine have used CRISPR genome editing to identify a neural ...

Characterizing 'keyhole' is first step to fighting obesity at cellular level

April 18, 2018
An international team has uncovered the potential to beat obesity at the cellular level, characterizing for the first time a complex, little-understood receptor type that, when activated, shuts off hunger.

Why is it harder for females to gain weight?

April 18, 2018
For years, scientists have observed that when male and female mice eat the same high-fat diet, the males gain significantly more weight than the females. The reasons for this difference between sexes are not completely understood, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.