Brain Derived Neurotrophic Factor (BDNF) - What is it?

Brain-derived neurotrophic factor has been shown to be one of the most important neurotrophins in processes such as learning, memory and thinking.

Inappropriate levels of this substance have also been shown to cause disease, cognitive dysfunction, and mood problems.

Next we will go into more detail about what exactly this protein does, some of the disorders in which it has been related, its mechanism of action and the importance of carrying out physical activity to have good levels of the factor.

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What is brain derived neurotrophic factor?

The brain-derived neurotrophic factor, better known by its acronym BDNF (brain-derived neurotrophic factor), is a protein, whose gene is located on chromosome 11, which it turns out to be the neurotrophin with the highest expression in the mammalian brain, especially in the cerebral cortex and hippocampus.

These neurotrophins play a very important role during brain development, and continue to exert their action on the plasticity of the nervous system once it has reached maturity.

They have been seen to play an important role in processes such as neurogenesis, the maintenance and sanitation of neuronal function and their structural integrity. In fact, Mark Tuszynski of the University of California showed that this was one of the factors that, in animal models, prevented neuronal death when brain injury occurs.

Function of BDNF in the nervous system

The neurotrophic factor acts in certain neurons of the central nervous system and, also, in the peripheral, helping neurons in these places to survive. In addition, it facilitates their growth and differentiation.

This substance it is especially active in parts of the central nervous system, specifically the cerebral cortex, the hippocampus and the most basal part of the brain. These areas are involved in cognitive processes such as memory, learning, and thinking. It has also been seen that it can be found in places like the retina, kidneys, motor neurons, skeletal muscle, prostate, and even in saliva.

Brain-derived neurotrophic factor plays an important role in long-term memory. Although it is true that a large number of neurons in the mammalian brain are formed during the embryonic state, parts of the brain of the individual, when he is already an adult, they have the ability to generate new neurons from neural stem cells. This process is what is known as neurogenesis. Neurotrophs help stimulate and control this process, BDNF being the most important.

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Mechanism of action

BDNF binds to at least two receptors on the surface of cells, which are capable of responding to this growth factor: Track B (TrkB) and the low affinity receptor for nerve growth factor (LNGFR). Neurotrophic factor modulates the activity of several neurotransmitter receptors, including nicotinic receptors.

1. TrkB

TrkB is encoded by the NTRK2 gene. Activation of the BDNF-TrkB pathway is important for short-term memory development and neuronal growth.

2. LNGFR

The interaction between BDNF and the LNGFR receptor is not very clear. Research has indicated that this interaction is the one behind the inhibition of neuronal death.

Cognitive habilyties

Living in environments that have multiple cognitive stimuli, in addition to leading a physically active lifestyle, has been linked to having good cognitive function in general. Cognitive, physical and visual stimulation translates into greater neuronal functioning, increasing the synaptic communication between neurons, which involves changes in both structure and chemistry cerebral.

Sensory stimuli are first processed by the cortex before reaching the hippocampus. BDNF expression is enhanced in environments rich in cognitive stimuli, which has been attributed to be the cause of having a better memory and learning capacity. This factor would cause more synapses (synaptogenesis), dendrites (dendritogenesis) and, as we have already mentioned, greater neurogenesis to be generated.

Relationship with pathology

In the same way that brain-derived neurotrophic factor has been associated with better cognitive ability and being behind processes such as learning, memory and thinking, it was inevitable to observe to what extent this factor may be absent in neurodegenerative diseases and disorders psychiatric. Here we will see a few.

1. Schizophrenia

The fact that BDNF is a crucial substance for the survival of the central and peripheral nervous system, especially in relation to synaptogenesis during and after embryonic development, has made it related to schizophrenia.

It has been seen that people with the diagnosis have lower amounts of the factor in the dorsolateral prefrontal cortex, an area related to working memory.

2. Depression

Having high levels of corticosterone, a stress hormone, has been associated with a reduction in BDNF expression in animal models, implicating atrophy of the hippocampus.

A decrease in the activity of the hippocampus and other limbic structures has been linked to mood problems, especially with suffering from chronic depression.

On the other hand, it has been seen that the neurotransmitter glutamate, caloric deficit, intellectual stimulation and Voluntary, in addition to antidepressants, increase the expression of BDNF in the brain and reduce symptoms depressive

3. Aging

BDNF levels are highly regulated throughout people's lives, both early and late in life.

As we have already seen, brain-derived neurotrophic factor is shown to be a critical substance in brain development both before and after the prenatal period. As we age, BDNF levels decrease in brain tissues.

Hippocampal volume decreases as a result of this phenomenon, suggesting that this reduction in BDNF involves the cognitive problems so characteristic of the elderly.

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BDNF and physical exercise

In animal models, especially with rats, it has been observed that engaging in moderate physical activity, such as running one kilometer per day, increased BDNF levels in the hippocampus.

These changes in factor levels have been especially significant in neurons of the dentate gyrus, the hilus, and the CA3 region and appear after just a few days. Other regions where changes were found were in the cerebellum, cerebral cortex, and lumbar spinal cord.

Research carried out with humans has shown that physical activity helps maintain and even improve brain plasticity, a characteristic very typical of the hippocampus. Superior functions such as learning or memory are benefited by carrying out healthy habits such as walking thirty minutes a day, do any sport or, and especially, run. Exercise induces increased BDNF gene expression.

Bibliographic references:

• Maisonpierre PC, Le Beau MM, Espinosa R, et al. (1991). Human and rat brain-derived neurotrophic factor and neurotrophin-3: gene structures, distributions, and chromosomal localizations. Genomics 10 (3): 558-68.
• Soppet, D; Escandon, E; Maragos, J; et al. (1991). The neurotrophic factors brain-derived neurotrophic factor and neurotrophin-3 are ligands for the trkB tyrosine kinase receptor. Cell 65 (5): 895-903.