Biologists led by Queen Mary University of London have traced the origins of bombesin, an appetite-regulating neurohormone, back over half a billion years to starfish and their marine relatives, revealing surprising evolutionary connections.
A breakthrough discovery led by biologists at Queen Mary University of London has unveiled that a neurohormone, known for controlling appetite in humans, has origins tracing back over half a billion years.
This research, published in the Proceedings of the National Academy of Sciences USA, reveals that bombesin — a neurohormone significant for signaling satiety — exists in both humans and ancient marine creatures like starfish, sea urchins and sea cucumbers.
Bombesin, a small peptide, has been recognized for its crucial role in hunger regulation, indicating when we’ve had enough to eat.
However, its evolutionary timeline does not start with humans or even mammals. It dates back long before vertebrates appeared on Earth.
Named after the fire-bellied toad (Bombina bombina), from which it was initially isolated in 1971, bombesin was found to reduce meal size and increase the intervals between meals when injected into mammals.
Uncovering an Evolutionary Story
Maurice Elphick, a professor of animal physiology and neuroscience at Queen Mary University, and his research team, together with Olivier Mirabeau at the Institut Pasteur in Paris, embarked on tracing the evolutionary history of bombesin.
Through a meticulous analysis of the genomes of invertebrates, the researchers discovered genes encoding bombesin-like neurohormones in the common starfish (Asterias rubens) and its relatives.
“It was a bit like looking for a needle in a haystack, but eventually we discovered genes encoding a bombesin-like neurohormone in the genomes of starfish and their relatives,” Elphick said in a news release.
The neurohormone found in starfish was named ArBN. Using mass spectrometry, collaborators at the University of Warwick identified its molecular structure, enabling synthesis and testing.
Starfish and Modern Science
Lead author Weiling Huang, a former doctoral student in Elphick’s lab, explored how ArBN affects starfish feeding behavior.
Starfish have a unique way of eating by everting their stomachs out of their mouths to digest prey such as mussels and oysters.
“When I tested ArBN, I saw that it caused contraction of the starfish stomach,” Huang said in the news release. “This suggested that ArBN might be involved in stimulating stomach retraction when starfish stop feeding. And this is exactly what I found. When I injected ArBN into starfish with their stomachs everted, it triggered the stomach to retract back into the mouth. What’s more, ArBN also delayed the initiation of feeding, as starfish injected with ArBN took longer to enclose a mussel compared to those injected with water.”
Broader Implications
The discovery offers deep insights into the evolutionary origins of feeding behavior among animals, tracing back half a billion years.
“We can infer that this function extends back half-a-billion years to the common ancestor of starfish, humans and other vertebrates,” added Elphick.
The research opens new avenues not just for understanding our biological past but also for practical applications in tackling contemporary problems. For instance, compounds mimicking bombesin are under development for treating obesity, potentially forming a new class of weight-loss medications.
Moreover, the findings may aid in managing starfish invasions into cooler waters due to climate change, threatening shellfish farms.
“Discovering molecules that inhibit feeding in starfish could be useful in managing these invasions,” Elphick added.
This significant discovery, funded by BBSRC, China Scholarship Council and Leverhulme Trust, not only enhances our comprehension of neurohormonal evolution but also highlights the unexpected links between humans and the unique, stomach-everting realm of starfish.
Source: Queen Mary University of London