Parkinson’s disease is the second most common neurodegenerative disease after Alzheimer’s effecting about 3 in 1000 people in industrialized nations. It seems that although it is very common people take it a little less seriously than Alzheimer’s or some other less common neurodegenerative disorders. I believe the general perception is that while people might have some motor neuron issues it is only a tremor, not severe memory loss, or complete loss of motor control like ALS. It is important to remember that anytime there are problems in the brain there are widespread systemic consequences.
Recently it has been determined that the effects of Parkinson’s disease go further than just a tremor and balance issues. Individuals suffering for Parkinson’s not only slowly develop a tremor that get progressively worse they can also experience the following non-motor symptoms:
- Depression
- Sleep Disturbance
- Sensory Abnormalities
- Autonomic Dysfunction
- Cognitive Decline
While people begin to suffer from motor symptoms which most likely are embarrassing but overtime may become debilitating, they also can become depressed and lose control of their sleep cycle. You can easily see how as these things pile up it can be more and more difficult for individuals to handle all of these symptoms along with the general decline of aging. It would be a lot, and the worst part would be that people only see the tremors. Your loved ones don’t know why you are tired all the time, or why you just aren’t quite yourself anymore.
Parkinson’s disease is not just a tremor. The brain is so delicate and even small disturbances can cause major problems. In Parkinson’s a whole section of the brain, the substantia nigra pars compacta essentially stops functioning because the neurons get choked up with non-functioning proteins. This could be the result of a few different problems and it seems that there isn’t one clear pathway that leads to the motor symptoms. One fairly common (30% of cases) cause is mitochondrial failure due to complex I defects. I will give a brief description of what this means just so we can see how these small issues can snowball and to demonstrate how complicated this disease really is.
So if cell biology and biochemistry aren’t your thing here is a brief recap. You probably remember that the mitochondria are the “power plant of the cell” or something like this. This is because a ton of ATP is made there. ATP is used to supply energy for cell function. You can probably see that if that isn’t happening we will have problems. So complex I is a giant protein that is the first step in a pathway that generates a lot of ATP.
A bout 1one in three Parkinson’s patients has a genetic predisposition that leads to complex I failure which then leads to mitochondrial failure which contributes to the neuronal death that then leads to the symptoms we see. You might be wondering, what about the other two out of those three? That is a good question and the answer is complicated. So many things could go wrong and lead to neuronal death. It isn’t as simple as a single receptor being bad or a single misfolded protein. There are a multitude of small things that can pile up and lead to neuronal degradation.
