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Hormones are molecules that act as messengers in the body, regulating various physiological processes, including appetite and digestion. Several hormones play a role in signaling hunger and satiety.
Evolutionary history. A new study has analyzed the evolutionary history of bombesin, a hormone that signals satiety to the brain. Researchers found this hormone in some vertebrate species and determined it performs the same function in humans. They also identified the genes encoding these hormones in evolutionarily distant species, such as starfish.
Bombesin. Scientists first discovered bombesin in 1971, not in humans but in an amphibian—the European fire-bellied toad (Bombina bombina). It’s a small peptide similar to those used by the human body to signal satiety, such as glucagon, gastric inhibitory peptide (GIP), and glucagon-like peptide-1 (GLP-1).
Researchers later found that injecting bombesin into mammals induced a feeling of fullness, causing subjects to reduce their food intake and spread it over longer periods.
“A needle in a haystack.” For the new study, researchers examined the genomes of various invertebrates, searching for genes encoding hormones similar to bombesin. They found them in several echinoderm species, including the common starfish (Asterias rubens), sea urchins, and sea cucumbers.
“It was a bit like looking for a needle in a haystack,” professor Maurice Elphick, co-author of the study, said. “But eventually we discovered genes encoding a bombesin-like neurohormone in the genomes of starfish and their relatives,” he added.
ArBN. The team then studied the function of this hormone, which they named ArBN. Using mass spectrometry, they determined its molecular structure, allowing them to synthesize and test it. The findings revealed that the hormone affected the starfish’s gastric processes.
“When I tested ArBN, I saw that it caused contraction of the starfish stomach,” Weiling Huang, co-author of the study, explained. “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.”
The study was published in Proceedings of the National Academy of Sciences.
Playing historian. The study provides new clues about how the digestive system and its regulatory mechanisms evolved, offering insight into a time 500 million years ago when the last common ancestor of humans and starfish lived.
The discovery also has implications for the pharmaceutical industry. In recent years, hormone-based treatments such as GLP-1 and GIP analogs have gained prominence. Drugs like semaglutide (marketed as Ozempic) and tripeptide were initially developed for diabetes treatment but have since gained traction as weight loss medications.
These compounds mimic hormones released after meals, signaling organs like the pancreas to activate digestion and the brain to suppress appetite. Bombesin, ArBN, and similar compounds could potentially be used in the same way.
Image | David Clode (Unsplash)
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