Appendix Linked to Parkinson’s Disease

Appendix

People who have had their appendix removed have lower risk of developing Parkinson’s disease, according to a new study.

Accumulation of misfolded alpha-synuclein protein in the brain is a hallmark of Parkinson’s disease. The reason for this is believed to originate in the gut and changes in the gut microbiome are known to play a key role in the onset of Parkinson’s disease.

Now, a team of scientists at the Van Andel Research Institute (VARI) in the US have discovered that removal of the appendix reduces the risk of developing Parkinson’s disease.

The team analyzed data from more than 1.6 million individuals. They found that removal of the appendix decades before Parkinson’s disease onset was associated with a lower risk for Parkinson’s, particularly for individuals living in rural areas, and delayed the age of onset.

Furthermore, they found that the healthy human appendix contained a build-up of alpha-synuclein and Parkinson’s-associated toxic alpha-synuclein products that are known to accumulate in Lewy bodies (a characteristic of Parkinson’s disease).

Lewy bodies are present in the brains of everyone with Parkinson's but evidence suggests that they may originate in other areas of the body and travel to the brain. Lewy bodies have also been found in the gut and vagus nerve.

This is intriguing because the data suggest that removal of the appendix may interrupt the gut-vagus nerve connection, which is at the center of the gut-brain axis. Severing this nerve may prevent alpha-synuclein from spreading to the brain, reducing the risk of developing Parkinson's.

Although generally thought to be redundant, the appendix actually plays a significant role in our immune system and in regulating the makeup of our gut bacteria.

This study, therefore, provides the first biological link between the gut microbiome and Parkinson’s disease.

Now, the question that remains is why does Parkinson’s develop only in some people with abnormal alpha-synuclein aggregation in the gut, and why others are seemingly resistant?

Reference:

Killinger, et al. The vermiform appendix impacts the risk of developing Parkinson’s disease. Science translational medicine 10.465 (2018): eaar5280.