Nav: Home

Sweet tooth? Flies have it too -- new study shows how they know what to eat and when to stop

March 31, 2016

All animals, including humans, love sweet food, particularly when we are hungry. But if you're someone who never turns down dessert under normal circumstances, try wolfing down six donuts as a scientific experiment. Even the moistest, most velvety piece of chocolate cake will seem a lot less appetizing--and you will likely eat less of it.

The brain processes many signals that help us regulate what we eat and how much. How do we know what tastes good and what doesn't? And how does our brain tell us how much to eat when we're not really hungry, versus when we're famished after a long workout?

Researchers at Rockefeller University working with Drosophila flies have brought us one step closer to understanding the biology of eating. In a study published in Cell, they've identified a set of neurons that are activated only when flies eat a very sweet solution--especially when the flies are hungry. If the food is less sweet, or when the flies are relatively full, these neurons become less active.

The researchers were surprised to discover that these brain cells connect to taste neurons in the pharynx, or throat, rather than in the fly's equivalent of the tongue--which means flies can directly taste and monitor food while swallowing it.

"These neurons in the fly brain are part of something akin to a 'food circuit,'" says Nilay Yapici, a postdoctoral fellow in the lab of lead author Leslie Vosshall, Robin Chemers Neustein Professor and head of the Laboratory of Neurogenetics and Behavior. Some aspects of this "food circuit" exist in many other animals, such as mice and humans, and one of the next steps in the research will be to examine whether other aspects, such as the specific neurons Yapici and Vosshall have identified in flies, exist in the mammalian brain. "We still don't know if that's the case," Yapici says, "but it would be very exciting, especially if it enables us to learn more about how we eat--and why we often eat too much."

Dinner time

Here's how the circuit appears to work: Taste neurons in the flies' pharynx (throat) connect to a group of 12 neurons, known as IN1 cells, which in turn transmit signals to the neural circuits that tell the brain whether to keep eating.

"These 12 interneurons help the brain identify what the flies are eating, and help regulate whether to continue or stop," says Yapici. "If we give the flies something sweet and they are hungry, they will eat continuously. If it's less sweet, they don't eat as much. The neurons are helping the brain evaluate what the animal's eating while it's eating it."

A new approach

It's hard to track how much flies eat every day. Each fly is tiny, and consumes roughly a microliter of food daily, making it very difficult to measure slight differences in food intake. For the current study, Yapici, Vosshall, and their colleagues pioneered a new technique they call Expresso, an exquisitely precise sensor that continuously records how much the flies are consuming in real time.

While the flies are eating, the researchers can observe their brains using a monitor that captures calcium levels in neurons, a proxy for neuronal activity. This part of the study was done in collaboration with Raphael Cohn, a graduate student in the laboratory of Vanessa Ruta, Gabrielle H. Reem and Herbert J. Kayden Assistant Professor and head of the Laboratory of Neurophysiology and Behavior.

To identify the specific neurons involved in eating behavior, the researchers inhibited different populations of neurons, and watched what changed as a result. They found when they inhibited the IN1 cells, the flies started to eat but would stop prematurely, even if they were still hungry. "Silencing the activity of these neurons appears to suppress food intake," says Yapici. What's more, when the researchers turned these neurons back on, satiated flies ate as if they were starving.

Next, the researchers observed how this specific group of neurons behaves under normal situations. They found that when hungry flies drink even a tiny amount of tasty, sweet food, the IN1 cells become activated and remain active for many minutes after the food has been swallowed. The researchers think that the activity of the IN1 cells drives these animals to ingest food. So it makes sense that when the flies aren't hungry and encounter sweet food, the neurons still become active, but quiet down relatively quickly. When the flies are hungry and only have the option of less tasty food, the neurons still exhibit a burst of activity, but it quickly quiets down, similarly to what happens when satiated flies are given tasty food. In each case, the activity of IN1 cells mirrored the eating behavior of the fly.

Hungry for help

The researchers believe these findings may have implications for diseases related to food intake such as obesity. "The goal of studying food intake behavior," says Yapici, "is to understand the biological signals that make us eat."

By working with flies, which have relatively small brains compared to mammals, the researchers can more easily identify and manipulate specific circuits that regulate food intake, then see if similar pathways are at play in animals with more complex neurocircuitry, such as mice and other mammals. "If you find a neural mechanisms in the fly, you can look for similar principles in a mouse model -- since you know what you are looking for, it may be easier to find," says Yapici.
-end-


Rockefeller University

Related Neurons Articles:

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.
Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.
How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.
A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.
Shaping the social networks of neurons
Identification of a protein complex that attracts or repels nerve cells during development.
With these neurons, extinguishing fear is its own reward
The same neurons responsible for encoding reward also form new memories to suppress fearful ones, according to new research by scientists at The Picower Institute for Learning and Memory at MIT.
How do we get so many different types of neurons in our brain?
SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.
These neurons affect how much you do, or don't, want to eat
University of Arizona researchers have identified a network of neurons that coordinate with other brain regions to influence eating behaviors.
Mood neurons mature during adolescence
Researchers have discovered a mysterious group of neurons in the amygdala -- a key center for emotional processing in the brain -- that stay in an immature, prenatal developmental state throughout childhood.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
More Neurons News and Neurons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.