Medical research is always providing new insights into disease. Here’s a new surprise. A recent study suggests that individuals who have had their appendix removed may have a reduced risk for Parkinson’s disease. A two-year study of 1.6 million Swedish patients showed that those who had an appendectomy early in their life had a 19 percent reduction in their risk for Parkinson’s. Rural populations had an even bigger reduction in risk. This could show a significant connection between the gut and the brain.
Parkinson’s disease is a chronic and progressive neurological disease, probably caused by both genetic and environmental factors. Parkinson’s disease symptoms include trembling of the hands and face, poor balance, muscle stiffness and loss of coordination. The disease can last for years or even a lifetime, and almost a quarter of a million cases are reported in the U.S. every year. There are some treatments available, but no cures.
Current medical knowledge says that Parkinson’s disease begins with the injury and death of nerve cells in an area of the brain called the substantia nigra, which is deep in the center of the brain. A protein called alpha-synuclein becomes mis-folded and forms clumps, killing the nerve cells. These cells produce a chemical neurotransmitter called dopamine. When the nerve cells die, they cannot communicate with muscles like they’re supposed to, explaining the physical symptoms of trembling and muscle stiffness.
The appendix is a tube-like organ about three-inches long located along the gastrointestinal tract at the point where the small and large intestines join. Occasionally, it becomes infected or ruptures, and must be removed. Losing one’s appendix causes few effects on the body, so it has historically been considered an unnecessary organ. Today, we know that the appendix plays a significant role in immune function: it helps regulate our microbiome and provides protection from invading microbes.
So how could a gut organ like the appendix be involved in a brain disease? Here’s where it gets interesting. In this new study, researchers found clumps of alpha-synuclein in nerve cells in the appendix, just like in the brains of Parkinson’s patients. The gut has the second largest concentration of nerve cells in the body, after the brain. These clumped proteins can be observed in the appendix early in the development of Parkinson’s disease, well before motor symptoms are seen. Even normal appendix tissue have different forms of alpha-synuclein that can form clumps. We already know that these misfolded proteins use the vagal nerve to travel between the gut and the brain, so removing the appendix may remove the early source of the alpha-synuclein in the brain. In addition, cutting the vagal nerve also prevents alpha-synuclein accumulation in the brain. This all indicated that nerves can be a superhighway for disease-causing proteins.
Could it be that Parkinson’s starts with the production and distribution of alpha-synuclein from the gut that eventually makes it to the brain? This shows, again, that the human body is complex, and when things go awry, disease states can occur at many different locations.