Dystrophin is a structural protein that is part of a large membrane-spanning complex called the dystrophin-glycoprotien-complex or DGC, which is found in muscle cells.
Dystrophin impacts the strength, stability and function of the muscles attached to your skeleton, muscles that move air in and out of your lungs and the muscles in your heart.
One way to understand how dystrophin functions is to imagine it is like the springs on a trampoline that coil and expand in response to the force of someone bouncing. When a muscle is used, the cells in that muscle contract. If we stick with our trampoline analogy, dystrophin is like the coil, which some have referred to is as a “molecular shock absorber”. The purpose of this protein is to make sure the muscles can move and withstand the forces applied to them.
Without dystrophin, the muscle cells lose their coil and no longer have the same strength and stability during muscle contraction. As a result, they become damaged as they are used. Muscles try to compensate for this damage by growing new cells. Still, over time, the production of these new cells stops. The damaged muscle cells are replaced with scar tissue and fat in a process called fibrosis.
What happens to the muscle when it gets damaged?
Many issues arise from the damage of muscle tissue. When tissue is constantly breaking down, the immune system is activated and tries to prevent the damage. This causes the release of different cells and chemicals that, under normal circumstances, would help repair tissue, as the chemicals and cells the immune system uses are very effective in solving short-term problems. But, when tissue is constantly being broken down, this immune response, which we call inflammation, can cause more issues.
For example, inflammation promotes the growth of scar tissue. While this is great after you have surgery and need your wounds to heal, in Duchenne muscular dystrophy, there is a buildup of scar tissue within the muscles. This is referred to as fibrosis, and it interferes with the structure and strength of your muscles. One way to lessen the effects of Duchenne muscular dystrophy is to reduce chronic inflammation which is the treatment strategy used with corticosteroids.
Other ways lack of dystrophin impact muscle:
Consistent muscle damage also wears down the outer protective layer of the muscle. The outer layer is important for controlling what comes into and goes out of the muscle. One of the most important roles of this layer is to ensure different minerals remain in the right proportions on either side of this muscle layer. These minerals, which include sodium, potassium and calcium, are necessary for powering the contractions of the muscular layers. However, when the outer layer of the muscle is damaged, these minerals leak into the cells and build up in unequal proportions, affecting the muscle’s ability to generate power and contract.
The mitochondria, known as the “powerhouse of the cell,” are also very important in generating power for cellular activities like repairing muscle cells. They also rely on minerals to create energy to drive these activities. This is why the mitochondria in individuals with Duchenne are inefficient at powering their cells, which further compromises the ability of the muscles to work and repair themselves when damaged.
Another avenue for treating the symptoms of Duchenne is to find ways to help regulate the balance of minerals in the cell, strengthen the outer layer of the muscle and enhance the performance of the mitochondria.
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