Sea snails secrete hormone-like toxins causing extended insulin shock in its prey, new research from the University of Copenhagen concludes. The toxin may be used to improve treatment for hormonal disorders.
Cobras bite, bats use echolocation and some sea snails kill their prey … by inducing insulin shock.
At the bottom of the sea, the cone snail Conus geographus lies in wait. When its favourite food, fish, approaches, it strikes. It releases a toxin resembling the hormone insulin, which the fish absorbs through its gills. This induces a state of hypoglycaemia, a form of insulin shock, and now the snail can feed.
A toxic sea snail
The white and brown sea snail Conus geographus lives in the shallow water of the Indo-Pacific Ocean and is about the size of the palm of a hand.
The sea snail stuns its prey by secreting its deadly venom: a mixture of toxins into the water near its fish prey. This enables the slow snail to catch and swallow the faster fish, sometimes as big as its own. One of the toxins is a fast-acting insulin mimetic that causes an insulin shock in its prey.
One of the most venomous creatures in the world, the venom from the cone snail is strong enough to kill a human.
Source: Ho Yan Yeung
New research from the University of Copenhagen shows that Conus geographus combines the insulin shock with another toxin resembling a hormone called somatostatin, which also plays an important role in blood glucose regulation.
"This is the first study to show that the sea snail affects blood glucose levels in its prey in more ways than one. It is a fascinating example of the sea snail's ability to use hormones as a weapon."
While insulin lowers blood glucose levels and the hormone glucagon helps increase them, somatostatin regulates both insulin and glucagon. But when the sea snail uses somatostatin in its venom, the consequences for the prey are fatal.
"This makes it easier for the snail to capture its prey. Our study, which was conducted on mice, shows that the somatostatin-like toxin activates a receptor that rather potently inhibits glucagon secretion. So the snail releases insulin-like toxin into the water to lower blood glucose levels in its prey, while also using somatostatin-like toxin to prevent glucagon secretion so the prey does not recover from the insulin shock," says Postdoc Ho Yan Yeung, who is first author of the new study and conducted part of the research at the Department of Biomedical Sciences at the University of Copenhagen.
May help reduce side effects in the future
Aside from playing an important role in the sea snail's hunting technique, somatostatin also affects a series of functions in the human body. Among other things, it regulates growth hormones.
The specific somatostatin-like toxin found in the sea snail is called Consomatin G1. Consomatin G1 turned out to be more selective than the somatostatin hormones used in existing treatment for i.e. hormonal disorders such as acromegaly, Ho Yan Yeung explains.
Because Consomatin G1 is more selective, the snail toxin may be used to design better somatostatin-based drugs in the future.
"The fact that the hormone-like toxin is so selective is amazing. It means that it may be able to eliminate adverse effects of existing drugs."
Aside from better treatment for growth hormone disorders, Ho Yan Yeung believes the sea snail venom may prove beneficial in a number of areas:
"Aside from the somatostatin-like toxin described in the study, the venom probably also contains other blood glucose- and metabolism-regulating hormones that may be used in the design of better drugs for diabetes or as a diagnostic tool in connection with e.g. various types of cancers. Naturally, it is something we want to explore further," she concludes.
Read the study "Fish-hunting cone snail disrupts prey's glucose homeostasis with weaponized mimetics of somatostatin and insulin" here.
