The Biology of Stress and Depression Pt. 7: What you can do to increase levels of Brain Derived Neurotrophic Factor (BDNF)

(These are all of the posts we have on this topic)

1st Post on Stress and Depression Why the Current Theory Fails So Often

2nd Post on Stress and Depression Cortisol

3rd Post on Stress and Depression Pregnenolone

4th Post on Stress and Depression DHEA

5th Post on Stress and Depression BDNF
6th Post on Stress and Depression: The Cholesterol/Dopamine Connection
7th Post on Stress and Depression: Increasing levels of Brain Derived Neurotrophic Factor (BDNF)

Hello again and welcome to our 7th post on the biology of stress and depression. In this post we will be discussing what types of exercise have been shown to increase levels of Brain Derived Neurotrophic Factor (BDNF). As stated in a previous post (click here to go to the post), BDNF is like fertilizer for your brain's neural circuits. If you want to learn something new, you need BDNF to help you pave those new neuro-pathways. These pathways can control something physical like how to throw a perfect spiral with a football, or something psychological like a new mindset or attitude. Either way you need to grow new circuits for your nerves in order to wire yourself for a new task. This process of creating these neurological structures or networks to adapt to new psychological, physiological, or emotional needs is called neuroplasticity.

In his book, Evolve Your Brain, Dr. Joe Dispenza eloquently described the neural network as, ".literally millions of neurons firing together in diverse compartments, modules, sections, and subregions throughout the entire brain. They team up to form communities of nerve cells that act in unison as a group, clustered together in relation to a particular concept, idea, memory, skill, or habit. Whole patterns of neurons throughout the brain become connected through the process of learning, to produce a unique level of mind."

So the term "neural network" describes a unique arrangement of connections of neurons that fire in a specified sequence. These networks allow you to perform tasks like tapping your feet, or recalling the lyrics to your favorite song as well as "learning" new tasks as required. Neuroplasticity is the ability of the brain to adapt and change. This flexibility in our nervous systems is based on the modification of existing neural networks and the creation of new ones. A key player in our ability to adapt to new nerve stimulus is a steady supply of BDNF.

If can keep optimal levels of BDNF ready to feed and develop new circuits in your brain the process of developing new skills, knowledge, and attitudes becomes much easier. So, BDNF helps you be the "you" that you want. You build yourself from the inside out firing and re-wiring new pathways based on what you choose to focus on. The implication here is that each of us an unexpected degree of control over who we are and how we feel.

The previous post on the stress hormone cortisol discussed the inverse relationship with cortisol has with cortisol production. If stress hormone and cortisol levels go up levels of BDNF go down. Cortisol also decreases the body's ability to deal with stress. It does this though damaging the hippocampus, a major contributor in the body[s ability to adapt to stress. As a result we feel stress more acutely even as the body has become even less able to cope!  It's a really strong feedback loop that encourages us all to be stressed. The good news is this nasty little equation can be reversed. By increasing BDNF we can decrease damaging levels of cortisol. This is how you re-wire to the new you that you want to be.

Our first look at increasing BDNF is exercise.

While our muscles pump iron, our cells pump out something else: particles that nourish a strong brain. For years scientists have struggled to explain the well-known mental benefits of exercise. These benefits include a variety of paybacks, including: offsetting depression and aging, to fighting Alzheimer's and Parkinson's disease. And, a team of researchers may have finally discovered a solid molecular link between how a good workout promotes a healthy brain.

Muscle cells increase the production of a protein called FNDC5 while you are exercising. A portion of this protein, called irisin, gets cut off and released into the bloodstream. Spiegelman and his colleagues at Harvard Medical School suspected that FNDC5, and the irisin created from it, are responsible for exercise-induced benefits to the brain. In particular they were interested, (as are we!), in increased levels of BDNF.

To sort out how exercise relates to BDNF, Spiegelman and his colleagues performed a series of experiments in living mice and cultured mouse brain cells. They put an experimental group of mice on a 30-day endurance training regimen. They didn't have to coerce their subjects, because running is part of a mouse's natural foraging behavior. The mice with access to a running wheel ran the equivalent of a 5K every night. Next, they compared them to a group of mice who lived like couch potatoes.

Aside from physical differences between wheel-trained mice and sedentary ones, (not surprisingly, the sedentary group had more body fat), the groups also showed significant neurological differences. The runners had more FNDC5 in their hippocampus, an area of the brain responsible for learning and memory. A happy hippocampus is also associated with better stress management and less depressed states.

Using mouse brain cells developing in a cell culture, the group next showed that increasing the levels of the co-activator PGC-1α boosts FNDC5 production, which in turn drives BDNF genes to produce more of the vital neuron-forming BDNF protein. They report these results in the journal Cell Metabolism. Spiegelman says it was surprising to find that the molecular process in neurons mirrors what happens in muscles as we exercise. The processes parallel each other! The mind and body are not separate after all.

How is the brain getting the signal to make BDNF? Some have theorized that neural activity during exercise (as we coordinate our body movements, for example) accounts for changes in the brain. But it's also possible that factors outside the brain, like those proteins secreted from muscle cells, are the driving force. To test whether irisin created elsewhere in the body can still drive BDNF production in the brain, the group injected a virus into the mouse's bloodstream that causes the liver to produce and secrete elevated levels of irisin. They saw the same effect as in exercise: increased BDNF levels in the hippocampus. This suggests that irisin could be capable of passing the blood-brain barrier, or that it regulates some other (unknown) molecule that crosses into the brain. This research finally sheds light on how exercise relates to BDNF and other so-called neurotrophins that keep the brain strong and healthy.

We have come a long way in the past twenty-five years in our understanding of the brain, from a generally accepted perception of the brain as being a hardwired, fixed and immutable organ to one that celebrates its dynamism. Now get out there and move it!