Study shows how insulin-like molecules play critical role in learning and memory

February 26, 2013 by Peter Reuell
“People think of insulin and diabetes, but many metabolic syndromes are associated with some types of cognitive defects and behavioral disorders, like depression or dementia,” said Yun Zhang, whose new research demonstrates how the signaling pathway of insulin and insulinlike peptides plays a critical role in helping to regulate learning and memory. Credit: Rose Lincoln/Harvard Staff Photographer

Though it's most often associated with disorders like diabetes, Harvard researchers have shown how the signaling pathway of insulin and insulin-like peptides plays another critical role in the body – helping to regulate learning and memory.

In addition to showing that the insulin-like peptides play a critical role in regulating the activity of neurons involved in learning and memory, a team of researchers led by Yun Zhang, Associate Professor of Organismic and , show that the interaction between the molecules can fine-tune how, or even if, learning takes place. Their work is described in a February 6 paper in Neuron.

"People think of insulin and diabetes, but many metabolic syndromes are associated with some types of and behavioral disorders, like depression or ," Zhang said. "That suggests that insulin and insulin-like peptides may play an important role in , but it's been very difficult to nail down the underlying mechanism, because these peptides do not have to function through that connect different in the brain"

To get at that mechanism, Zhang and colleagues turned to an organism whose and nervous system are well described and highly accessible by genetics – C. elegans.

Using , researchers altered the small, transparent worms by removing their ability to create individual insulin-like compounds. These new "mutant" worms were then tested to see whether they would learn to avoid eating a particular type of bacteria that is known to infect the worms. Tests showed that while some worms did learn to steer clear of the bacteria, others didn't – suggesting that removing a specific insulin-like compound halted the worms' ability to learn.

Researchers were surprised to find, however, that it wasn't just removing the molecules that could make the animals lose the ability to learn – some peptide was found to inhibit learning.

"We hadn't predicted that we would find both positive and negative regulators from these peptides," Zhang said. "Why does the animal need this bidirectional regulation of learning? One possibility is that learning depends on context. There are certain things you want to learn – for example, the worms in these experiments wanted to learn that they shouldn't eat this type of infectious bacteria. That's a positive regulation of the learning. But if they needed to eat, even if it is a bad food, to survive, they would need a way to suppress this type of learning."

Even more surprising for Zhang and her colleagues was evidence that the various insulin-like molecules could regulate each other.

"Many animals, including the humans, have multiple insulin-like molecules and it appears that these molecules can act like a network," she said. "Each of them may play a slightly different role in the nervous system, and they function together to coordinate the signaling related to learning and memory. By changing the way the molecules interact, the brain can fine tune learning in a host of different ways."

Going forward, Zhang said she hopes to characterize more of the insulin-like peptides as a way of better understanding how the various molecules interact, and how they act on the neural circuits for .

Understanding how such pathways work could one day help in the development of treatment for a host of cognitive disorders, including dementia.

"The signaling pathways for insulin and insulin-like are highly conserved in mammals, including the humans," Zhang said. "There is even some preliminary evidence that insulin treatment, in some cases, can improve cognitive function. That's one reason we believe that if we understand this mechanism, it will help us better understand how pathways are working in the human brain."

Explore further: New evidence links Alzheimer's disease and diabetes

Related Stories

New evidence links Alzheimer's disease and diabetes

March 20, 2012
An emerging body of research suggests that Alzheimer's disease may be linked to insulin resistance, constituting a third type of diabetes. This model is based on several observations including an increased risk of developing ...

Nutritional supplement may help prevent Alzheimer's, research suggests

January 10, 2013
(Medical Xpress)—A nutritional supplement available over-the-counter may offer protection from Alzheimer's disease, a study by the University of Virginia and Northwestern University suggests.

Recommended for you

Cognitive cross-training enhances learning, study finds

July 25, 2017
Just as athletes cross-train to improve physical skills, those wanting to enhance cognitive skills can benefit from multiple ways of exercising the brain, according to a comprehensive new study from University of Illinois ...

Brain disease seen in most football players in large report

July 25, 2017
Research on 202 former football players found evidence of a brain disease linked to repeated head blows in nearly all of them, from athletes in the National Football League, college and even high school.

Zebrafish study reveals clues to healing spinal cord injuries

July 25, 2017
Fresh insights into how zebrafish repair their nerve connections could hold clues to new therapies for people with spinal cord injuries.

Lutein may counter cognitive aging, study finds

July 25, 2017
Spinach and kale are favorites of those looking to stay physically fit, but they also could keep consumers cognitively fit, according to a new study from University of Illinois researchers.

Brain stimulation may improve cognitive performance in people with schizophrenia

July 24, 2017
Brain stimulation could be used to treat cognitive deficits frequently associated with schizophrenia, according to a new study from King's College London.

New map may lead to drug development for complex brain disorders, researcher says

July 24, 2017
Just as parents are not the root of all their children's problems, a single gene mutation can't be blamed for complex brain disorders like autism, according to a Keck School of Medicine of USC neuroscientist.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.