Train Your Brain: Exploring The Science Of The Exercise Induced Hormone

Irisin might aid the treatment of many neurological conditions

Table of Contents

How does exercise affect your brain?

It’s easy to imagine what exercise can do for the body, but did you know it can change your brain, too? Moving the body kickstarts a chain reaction. Muscles move, using up energy that is stored in cells of the body. Breathing speeds up, allowing carbon dioxide to be released and fresh oxygen to be brought in. The heart pumps faster, moving blood more and more quickly. All these processes contribute to building muscle and making the heart stronger… but what about the brain.

Exercise can have a powerful effect on mood, as well as longer-term processes like behavior and memory. If you are a runner, or good friends with one, you might have heard of the “runner’s high.” Runners, and other people who engage in intense cardiovascular exercise, describe an immediate boost in mood after exercising. It can be so powerful that the good mood motivates you to do the same exercise day after day! It’s caused by a release of happy hormones.

Exercise-induced joy
Exercise-induced joy. Credit: DepositPhotos/Daxiao_Productions

The longer-term changes are caused by neurons. Neurons are a group of many kinds of cells that make up the brain, spine, and nervous system. They’re responsible for thoughts, feelings, and even twitching your finger. Exercise changes the way neurons act, making them more efficient. They can respond to changes and stimuli more rapidly. Exercise can even help build more neurons. The increased number of neurons and their higher efficiency improves mood. It can even boost spatial and working memory, so the more you run, the more you remember!

What is Irisin?

Irisin is a hormone that begins circulating in the body when you exercise. Hormones are one of the body’s modes of communication, taking the form of messenger molecules released into the blood. They can come from many glands and organs, including the liver, kidneys, and adrenal glands. The hypothalamus and the pituitary gland in the brain act as master regulators that tell the organs when to produce hormones and how much to produce. Cells also have specific receptors, to ensure that not every part of our body responds to every hormone. Each hormone–receptor pair is like a lock and key.

Lock_and_key_enzyme_mechanism
The red represents a receptor on the surface of the cell, and the blue represents a hormone that would be traveling through the bloodstream. Credit: Wikimedia/domdomegg

Irisin is named after the Greek messenger goddess Iris, for its ability to communicate with many different systems. It was discovered in 2002, and quickly began to be researched in many fields of neuroscience and biomedicine. Irisin is produced by the cells of skeletal muscles. It’s also made by cells in the spine. This allows irisin to cross into the brain, unlike other hormones which remain in the blood.

 

Irisin is related to exercise, and is being explored for the treatment of multiple disorders like obesity, diabetes, and metabolic disorders, and even as an anti-ageing and anti-cancer treatment. As exercise can affect the brain, it is being investigated as a way to treat diseases of the nervous system.

How can Irisin be used to treat Alzheimer’s?

Alzheimer’s affects over 55 million people worldwide, and is the most common cause of dementia. As the world’s population ages, the number is expected to double every 20 years. Unfortunately, Alzheimer’s is irreversible and progressive. Once diagnosed, it only gets worse. Although there are many promising treatment options which can slow the symptoms, there is currently no cure.

Alzheimer’s disease is a brain disorder that can affect memory, behavior, and the brain’s ability to acquire new knowledge. Although younger individuals can get it, it tends to be more common in older adults. Alzheimer’s is caused by a loss in quality and quantity of neurons. There is also a loss of connections between neurons, which triggers a decline in brain function.

Imagine each neuron as a road that carries cars. Each car is a nerve impulse or signal, which are how neurons communicate information to each other about what is going on in the body. There is a massive network of roads, all sending information every which way! In order for the entire brain to function, all the cars need to flow quickly—there can’t be any traffic jams or delays. Alzheimer’s interrupts the flow of signals through an accumulation of proteins, which act as roadblocks. One kind of protein accumulates within the cells. Amyloid plaques are the other type of protein, and these accumulate at junctions between cells. When you have roadblocks within each road and at each junction, the brain finds it very difficult to function.

Histopathology_of_neurofibrillary_tangles_in_Alzheimer's_disease
Neurons affected by Alzheimer’s. Long purple streaks represent the protein pileups. Credit: Wikimedia/Mikael Häggström

Irisin has been found to be one of the hormones that can help boost the growth of neurons.   interacts with other hormones, encouraging neurons to multiply. In an experiment with mice, researchers found that irisin could not only improve brain function, but slowly reverse damage!

 

Exciting new research has revealed that boosting irisin production in mice produces hormones that break down the protein pileups, allowing communications to move again! Irisin, the messenger, activates a chain reaction. It triggers the release of another hormone. This hormone encourages the production of another chemical, a chemical that breaks down amyloid plaques! By eliminating the roadblocks at junctions, one part of the traffic flow is fixed. Although irisin can’t stop the roadblocks from building at all, it can help fix them when they do. Irisin might be a promising cure to treat one of the main underlying causes of Alzheimer’s.

Irisin’s action in breaking down amyloid plaques
Irisin’s action in breaking down amyloid plaques.

There is still much we don’t know about the human body, but neuroscience and biomedical research are uncovering mysteries incredibly quickly. In twenty years, we were able to not only discover a new protein, but begin to use it in animal studies. While medical researchers are careful about moving patiently, we may only be a few years away from promising treatments for humans.

Glossary

Amyloid plaque: An unusual buildup of amyloid proteins between neurons in the brain.

Cardiovascular exercise: Any vigorous activity that increases heart rate and respiration and raises oxygen and blood flow throughout the body

Dementia: A loss of memory, language, problem-solving, and other thinking abilities that is severe enough to interfere with daily life

Hormone: Chemicals released into the bloodstream to allow cells to communicate with one another

Neuron: A nerve cell in the brain or spinal cord

Flesch Kincaid Grade Level: 9

Flesch Kincaid Reading Ease: 55.5

Contributors

  • Yamini Srikanth
    : Author
    Yamini's (he/they) interests lie in environmental education, science communication and trying to build a better world. When not languishing in front of his laptop, they can be found outside, poking at any insect, bird or plant. They love making science accessible, especially to those who aren't encouraged to pursue it. Yamini hopes that the young women who read Smore love learning from their articles and get just a little bit more excited about science!

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