Jellyfish and fruit flies shed light on the origin of hunger regulation


Date:
April 11, 2023
Source:
Tohoku University
Summary:
To survive, all organisms must regulate their appetite. Hormones
and small proteins called neuropeptides perform this process,
stimulating feelings of hunger and fullness. When researchers noted
the similarities between GAWamide, a neuropeptide that regulates
feeding in the Cladonema jellyfish, and myoinhibitory peptide,
a neuropeptide that regulates feeding in fruit flies, they decided
to test whether they could exchange the two. Their success in doing
so highlights the deep evolutionary origins of feeding regulation.


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FULL STORY ========================================================================== Decades' worth of research has shown that the motivation to feed,
i.e., hunger and feelings of fullness, is controlled by hormones and
small proteins called neuropeptides. They are found in a wide array of organisms like humans, mice and fruit flies. Such a widespread occurrence suggests a common evolutionary origin. To explore this phenomenon,
a research group has turned to jellyfish and fruit flies, discovering
some surprising results.


========================================================================== Although jellyfish shared a common ancestor with mammals at least 600
million years ago, their bodies are simpler; they possess diffused
nervous systems called nerve nets, unlike mammals which have more
concrete structures such as a brain or ganglia. Still, jellyfish possess
a rich repertoire of behaviors, including elaborate foraging strategies,
mating rituals, sleep and even learning. Despite their important position
in the tree of life, these fascinating creatures remain understudied,
and almost nothing is known about how they control their food intake.

The group, which was led by Hiromu Tanimoto and Vladimiros Thoma
from Tohoku University's Graduate School of Life Sciences, focused on Cladonema, a small jellyfish with branched tentacles that can be raised
in a laboratory. These jellyfish regulate how much they eat based on
how hungry they are.

"First, to understand mechanisms underlying feeding regulation, we
compared the gene expression profiles in hungry and fed jellyfish,"
said Tanimoto. "The feeding state changed the expression levels of
many genes, including some that encode neuropeptides. By synthesizing
and testing these neuropeptides, we found five that reduced feeding
in hungry jellyfish." The researchers then honed in on how one such neuropeptide -GLWamide - - controls feeding. A detailed behavioral
analysis revealed that GLWamide inhibited tentacle shortening, a crucial
step for transferring captured prey to the mouth. When the researchers
labelled GLWamide, they found it was present in motor neurons located in
the tentacle bases, and feeding increased GLWamide levels. This led to
the conclusion that, in Cladonema, GLWamide acts as a satiety signal --
a signal sent to the nervous system indicating that the body has had
enough food.

Yet the researchers' quest to explore the evolutionary significance
of this finding did not stop there. Instead, they looked to other
species. Fruit flies' feeding patterns are regulated by the neuropeptide myoinhibitory peptide (MIP).

Fruit flies lacking MIP eat more food, eventually becoming obese.

Interestingly, MIP and GLWamide share similarities in their structures, suggesting they are related through evolution.

"Since the functions of GLWamide and MIP have been conserved despite
600 million years of divergence, this led us to ponder whether it was
possible to exchange the two," said Thoma. "And we did exactly that,
first giving MIP to jellyfish and then expressing GLWamide in flies
that had no MIP." Amazingly, MIP reduced Cladonema feeding, just
as GLWamide had. Furthermore, the GLWamide in flies eliminated their
abnormal over-eating, pointing to the functional conservation of the GLWamide/MIP system in jellyfish and insects.

Tanimoto notes that their research highlights the deep evolutionary
origins of a conserved satiety signal and the importance of harnessing a comparative approach. "We hope that our comparative approach will inspire focused investigation of the role of molecules, neurons and circuits in regulating behavior within a wider evolutionary context."
* RELATED_TOPICS
o Plants_&_Animals
# Marine_Biology # Animals # Sea_Life # Food #
Food_and_Agriculture # Evolutionary_Biology #
Pests_and_Parasites # Agriculture_and_Food
* RELATED_TERMS
o Breastfeeding o Anterior_pituitary o Anchovy o Hummingbird
o Hematophagy o Appetite o Toucan o Protein

========================================================================== Story Source: Materials provided by Tohoku_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Vladimiros Thoma, Shuhei Sakai, Koki Nagata, Yuu Ishii, Shinichiro
Maruyama, Ayako Abe, Shu Kondo, Masakado Kawata, Shun Hamada,
Ryusaku Deguchi, Hiromu Tanimoto. On the origin of appetite:
GLWamide in jellyfish represents an ancestral satiety
neuropeptide. Proceedings of the National Academy of Sciences,
2023; 120 (15) DOI: 10.1073/ pnas.2221493120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230411105906.htm

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