Protein and salt drive post-meal sleepiness

November 22, 2016
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

Image ordering often based on factors other than patient need: study

September 25, 2017
Do you really need that MRI?

Bone marrow concentrate improves joint transplants

September 25, 2017
Biologic joint restoration using donor tissue instead of traditional metal and plastic may be an option for active patients with joint defects. Although recovery from a biologic joint repair is typically longer than traditional ...

Researchers describe mechanism that underlies age-associated bone loss

September 22, 2017
A major health problem in older people is age-associated osteoporosis—the thinning of bone and the loss of bone density that increases the risk of fractures. Often this is accompanied by an increase in fat cells in the ...

Researchers develop treatment to reduce rate of cleft palate relapse complication

September 22, 2017
Young people with cleft palate may one day face fewer painful surgeries and spend less time undergoing uncomfortable orthodontic treatments thanks to a new therapy developed by researchers from the UCLA School of Dentistry. ...

Exosomes are the missing link to insulin resistance in diabetes

September 21, 2017
Chronic tissue inflammation resulting from obesity is an underlying cause of insulin resistance and type 2 diabetes. But the mechanism by which this occurs has remained cloaked, until now.

Thousands of new microbial communities identified in human body

September 20, 2017
A new study of the human microbiome—the trillions of microbial organisms that live on and within our bodies—has analyzed thousands of new measurements of microbial communities from the gut, skin, mouth, and vaginal microbiome, ...

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.