Gut bacteria tell the brain what animals should eat

April 25, 2017, Public Library of Science
Gut bacteria tell the brain what animals should eat. Credit: Gil Costa

Neuroscientists have, for the first time, shown that gut bacteria "speak" to the brain to control food choices in animals. In a study publishing April 25 in the Open Access journal PLOS Biology, researchers identified two species of bacteria that have an impact on animal dietary decisions. The investigation was led by Carlos Ribeiro, and colleagues from the Champalimaud Centre for the Unknown in Lisbon, Portugal and Monash University, Australia.

There's no question that nutrients and the microbiome, the community of bacteria that resides in the gut, impact health. For instance, diseases like obesity have been associated with the composition of the diet and the microbiome.

However, the notion that microbes might also be able to control behavior seems a big conceptual leap. Yet that's what the new study shows.

Experiments conducted using the fruit fly Drosophila melanogaster, a model organism allowed the scientists to dissect the complex interaction of diet and microbes and its effect on food preference. The scientists initially showed that flies deprived of amino acids showed decreased fertility and increased preference for protein-rich food. Indeed, the team found that the removal of any single essential amino acid was sufficient to increase the flies' appetite for protein-rich food.

Furthermore, the scientists tested the impact on of five different species of bacteria that are naturally present in the guts of fruit flies in the wild. The results exceeded the scientists' expectations: two specific bacterial species could abolish the increased appetite for protein in flies that were fed lacking essential amino acids. "With the right microbiome, are able to face these unfavorable nutritional situations," says Santos.

"In the fruit fly, there are five main ; in humans there are hundreds," adds co-author Patrícia Francisco. This highlights the importance of using simple animal models to gain insights into factors that may be crucial for human health.

How could the bacteria act on the brain to alter appetite? "Our first hypothesis was that these bacteria might be providing the flies with the missing ," Santos explains. However, the experiments did not support this hypothesis.

Instead, the "seem to induce some metabolic change that acts directly on the brain and the body, which mimics a state of protein satiety," Santos says.

In sum, this study shows not only that gut act on the brain to alter what animals want to eat, but also that they might do so by using a new, unknown mechanism.

Explore further: Identifying the brain mechanisms behind changes in feeding habits

More information: Leitão-Gonçalves R, Carvalho-Santos Z, Francisco AP, Fioreze GT, Anjos M, Baltazar C, et al. (2017) Commensal bacteria and essential amino acids control food choice behavior and reproduction. PLoS Biol 15(4): e2000862. DOI: 10.1371/journal.pbio.2000862

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3 / 5 (2) Apr 25, 2017
Are separate species integrated with humans through hormone, neurotransmitter and other signaling pathways really "other"? Or are they part of the "individual"? Perhaps even the larger part, as their separate DNA operates thousands of times as many cells in our bodies as the homo sapiens DNA does.
5 / 5 (1) Apr 25, 2017
Are separate species integrated with humans through hormone, neurotransmitter and other signaling pathways really "other"? Or are they part of the "individual"? Perhaps even the larger part, as their separate DNA operates thousands of times as many cells in our bodies as the homo sapiens DNA does.

I agree in principle - I consider my microbiome to be an integral part of me.
But to get to anywhere close to 1000 times as many cells you would have to count all of the mitochondria as well at the gut biome... and even then, bacterial cells are so much smaller that it is still only a few percent of the molecule being controlled by the bacteria DNA.
not rated yet Apr 27, 2017
Could this brain/gut interaction be at the root of dietary cravings in pregnancy? Either as a result of signals from the child ot due to the mess pregnancy makes of blood chemistry.

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