Exercise - Good for the Brain
There are plenty of good reasons to be physically active. Big ones include reducing the odds of developing heart disease, stroke, and diabetes. Maybe you want to lose weight, lower your blood pressure, prevent depression, or just look better. Here’s another one, which especially applies to those of us (including me) experiencing the middle age conversations “ oh you know …. What’s his name….. that comes with age: exercise changes the brain in ways that protect memory and thinking skills.
I have been studying again with The Kharrazian Institute most recently on Neuroinflammation (and will be back in California again in September to attend his advanced Gastrointestinal course). It’s a huge topic with so much science to get my head into, but I wanted to share a snippet of fascinating research on the benefits that exercise has on brain health.
Firstly, let me explain, as briefly as I can, about the cells that make up the brain (and spinal cord) in the central nervous system, namely Neurons and Glial cells.
A neuron (also known as nerve cell) is an electrically excitable cell that 1) takes up 2) processes and 3) transmits information through electrical and chemical signals. It is one of the basic elements of the nervous system. Neurons however only make up around 10% of the brain; the remaining 90% in the central nervous system (brain and spinal cord) and the peripheral nervous system are non neuronal cells called glial cells which are a key part of both brain function and integration.
Glia were discovered in 1856 by the pathologist Rudolf Virchow in his search for a "connective tissue" in the brain. The term derives from Greek γλία and γλοία "glue"(/ˈɡliːə/ or /ˈɡlaɪə/), and suggests the original impression that they were the glue of the nervous system. As such, they maintain homeostasis, form myelin, and provide support and protection for neurons. In the central nervous system, glial cells include oligodendrocytes, astrocytes, and microglia, and in the peripheral nervous system, glial cells include Schwann cells and satellite cells. They have four main functions: (1) to surround neurons and hold them in place; (2) to supply nutrients, trophicfactors (BDNF) and oxygen to neurons; (3) to insulate one neuron from another; (4) to destroy pathogens and remove dead neurons - sounds fairly key right!
The two I am going to focus on today are:
Astrocytes: star-shaped glial cells that have a number of functions, including support of the blood-brain barrier and provision of nutrients to neurons
Microglia cells mediate immune responses in the central nervous system by acting as macrophages (think a little pac-man), clearing cellular debris and dead neurons from nervous tissue. They support and nourish neurons by secreting neurotrophic factors and very importantly clean up tangles, plaques and “debris”.
They do this in what is termed a “ resting “ – M0 state, and in this “state” their structure is ramified - have branches, like the top part of this image.
However, under stress (we have to consider, that in biology stress is mental or emotional, poor sleep patterns, dysregulated blood sugar, anaemia in inflammation) or encountering a head trauma or infection microglial cells are induced away from this M0 resting state into an M1 type, releasing inflammatory factors and mediators and causing neuroinflammatory responses.
Ordinarily, after the inflammation fades away, microglia shift into the alternative activated M2 phenotypes that play a role in neuroprotection.
But if the “stressor “ is unrelenting the M1 state can remain and theses beautifully elegant branches type structure – lose their shape and become more amoeboid in shape (as in the bottom part of the diagram above). and we see an environment of chronic neuroinflammation and microglia release potent neurotoxins, which may cause neuronal damage and of course in an amoeboid form they lose the ability to clear up debris, plaques and tanges. Sustained overactivation of microglia has been observed in multiple neurodegenerative diseases as per this paper in nature.
This is only the tip of the iceberg and there is a great deal more to write about this area, but for now I wanted to share how exercise (and specifically high intensity – sharp bursts of exercise) have been shown to turn on M2 - anti-inflammatory expression and stimulates the production of BDNF (BRAIN DERIVED NEUROTROPHIC FACTOR). BDNF is a protein that promotes the survival of nerve cells.
Seven ten-minute high-intensity exercise once or twice a day is recommended. Now, the more intense it is, the greater the oxidative stress, but when finished, you get a rebound anti-inflammatory effect. So, the reason that exercise is so protective for us, once we do, let’s say, a twenty run where you are pushing yourself, but not to the extreme we hit a pro-inflammatory state, but for hours and hours and hours later, our antioxidant enzymes become up regulated and we are producing antioxidants the rest of the day. So, you get a short burst of oxidative stress with a long term up-regulation of antioxidant pathways.
Remember the 7-minute exercise regime I posted on Monday? Give it a go…. your neurons may depend on it!
In health, Tanya x