So what is a free radical?
We think of free radicals as the waste products from chemical reactions that take place in the body, when the body doesn’t possess the resources to deal with them they can build up in the body. They become a concern when there are too many as they can cause damage to lipid (fat) structures, protein structures and can also alter our DNA molecules.
How are they produced?
Now this is a bit sciencey… during our metabolism, electrons and hydrogens are transferred from coenzymes to oxygen within the electron transport chain. The end result of this is H2O, but along the way, free radicals are produced.
During this process, sometimes oxygen can gain an electron, this generates a free radical called a superoxide, which has an unpaired electron (electrons are unstable when they are unpaired- they don’t like it). The superoxide can gain another electron form the ETC- this will react with 2 hydrogen ions to form hydrogen peroxide- this can then react with an electron forming a hydroxyl radical (another unpaired electron).
How is damage caused?
Hydroxl radicals are very reactive! They do not like to be unpaired and so they scavenge, to find another electron. However, they are indiscriminate and can take electrons from healthy cells, such as lipids in cell membranes, this damages the cell and can lead to degeneration or disease. When a hydroxyl radical takes a hydrogen atom from a lipid, like a polyunsaturated fatty acids, it produces a lipid radical and water. This lipid radical is then free to react with oxygen to form another lipid radical, removing hydrogens from other lipids and forming free radicals- a chain reaction. This chain reaction and damage links to ageing disease, DOMS and influences recovery after exercise.
The immune system
When exercise is heavy, intense and overly stressful, the immune system is suppressed. Injury to muscle cells occurs from training and pro-inflammatory cytokines, anti-inflammatory cytokines and cortisol levels increase. (Cytokines are proteins produced by cells and interact with the immune system to regulate the body’s response to diseases/ infection by altering cellular behaviour).
Cytokines
Pro-inflammatory cytokines stimulate neutrophils and monocytes to the site of damaged tissue. They are often produced in response to local injury.
The production of IL6 levels in the blood increases in response to the perceived threat (injury) but is counterbalanced by the release of cytokine inhibitors (IL1ra and TNF-R) and the anti-inflammatory cytokine IL10. These inhibit the duration of the inflammatory response.
Antioxidants
The production of free radicals has already been briefly described, with the most common being; Superoxide radicals, Hydrogen Peroxide, Lipid radicals, Nitric oxide, Singlet oxygen (closely associated with the oxidation of LDL), Hydroxyl radicals (HO• – A superoxide combined with nitric oxide)
Free radicals may damage cell membranes through lipoperoxidation and damage DNA.
The body has a defence system to combat this, the antioxidant system, which naturally up-regulates in response to a stressor. The main ones are;
Enzymes- Catalase (CAT), Superoxide dismutase (SOD), Glutathione peroxidase (GPX) and Glutathione reductase.
Non-enzymatic- Vitamins A, E, and C, Glutathione, Ubiquinone and Flavonoids – quercetin, resveratrol
Trace elements- Selenium, Copper, Zinc, Manganese, Uric acid, Albumin, Ferritin and Bilirubin
An imbalance occurs when these defences is outweighed by the production of free radicals, the body is then undergoing “oxidative stress”. This can be due to an increase in free radical production, a decrease in antioxidant levels or a combination of both.
If you would like to know more about oxidative stress, then please contact me, there are some sneaky signs and symptoms that may give an indication to this.
