By Dr. Shawn Watson, Co-founder and CEO, Senescence Life SciencesAt the most basic level, the human brain is a network of cells (neurons) working together to process, learn, retain and recall information. When we experience an external stimulus such as a sight, sound or taste, an electrical signal travels to our brain passing from neuron to neuron. There are, however, small gaps between each neuron called synapses, where the electrical signal is converted into a chemical signal. These chemical signals are called neurotransmitters, and the neurotransmitters will travel across the synapse that separates one neuron from another. Once these neurotransmitters cross the synapse and reach the connecting neuron, the electrical signal will be restarted and the process repeats itself.
The Free Radical Theory of Aging (FRTA) is a theory widely accepted amongst the scientific community that explains why organisms and tissues, including the brain, age. The theory is based upon the fact that cellular metabolism (the process that gives our cells the energy to function) produces harmful by-products that damage the cell. These by-products take the form of free radicals, which are defined as any atoms or molecules that have a single unpaired electron within their outer shell, making them highly reactive. Our cells (particularly our neurons) have, however, developed a plethora of defenses against these free radicals, both to disengage them immediately and to repair the damage that they cause. Despite these considerable defences, as we age there is a shift in the balance between rates of damage and rates of repair, resulting in the build-up of harmful compounds (just like the sludge that builds within a car engine over time).
Our neurons are extremely unique cells, unlike anything else in our body in regards to their energetic demands. They operate in a finely-tuned metabolic environment and use an incredible amount of energy - with oxygen as their fuel. In terms of metabolism, our brain makes up only 2% of our body mass but consumes 20% of our oxygen. This equates to your brain generating between 10 and 25 watts of power - enough energy to power a light bulb. With such significant energetic demands, our neurons experience arguably the highest rates of free radical production in our body.
While other molecular components of neurons can be attacked by free radicals, lipids (fats) are particularly susceptible due to their sheer abundance in the brain (60% of the brain is fat!). Scientists call this process "lipid peroxidation" and recent lines of evidence, including studies by Senescence Life Sciences, have shown that this process is key to understanding why a neuron’s ability to conduct electrical signals changes with age. Luckily, neurons are extremely resilient and have natural repair mechanisms capable of combating the ongoing damage. These capabilities, however, begin to change with age, and we start to see a gradual buildup of lipid damage within the cell and a resulting reduction in the transmission abilities of our neurons. Ultimately, as previously mentioned, these changes are thought to be responsible for the natural decline in cognitive capabilities of the human brain.
The previous sections stress the importance of supporting and regulating neuronal repair mechanisms within the aging brain. It is important to remember that neurons do not replicate, divide or renew themselves. For all intents and purposes, with a few exceptions aside, the number of neurons you are born with is the number you die with… so take care of them!
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