A peek at surgically removed appendix tissue shows this tiny organ, often considered useless, seems to be a storage depot for an abnormal protein — one that, if it somehow makes its way into the brain, becomes a hallmark of Parkinson’s.
In their study, people whose appendix had been removed were less likely to develop the neurodegenerative disease.
And the appendix, long thought of as pointless in the human body, contained the substance that kills brain cells.
The findings were the most compelling evidence yet that the disease’s origins lie outside the brain.
In Parkinson’s, toxic proteins build up in the brain to kill nerves, particularly those linked with movement.
The findings are the latest to implicate the gut and immune system in the genesis of the disease, in which the loss of neurons in a brain area that controls movement lead to a tremor and slurred speech.
Dr Viviane Labrie, an assistant professor at Van Andel Research Institute in Michigan, U.S.A, and senior author of the study, said, “Despite having a reputation as largely unnecessary, the appendix actually plays a major part in our immune systems, in regulating the makeup of our gut bacteria and now, as shown by our work, in Parkinson’s disease.”
It might feel counter-intuitive, but there is now growing evidence that the gut is involved.
Researchers at the Van Andel Research Institute, in Michigan, looked at data on 1.7 million people over half a century.
Analysing the content of people’s appendixes showed they contained the same toxic protein – called alpha synuclein – that is found in the brains of Parkinson’s patients.
The appendix is clearly not the whole of the story (otherwise removing it would prevent all cases).
But the researchers argue the guts are a breeding ground for the protein, which then travels up the vagus nerve and into the brain.
Dr Labrie said the fact that removal of the appendix was linked to a decreased risk and not complete protection suggested that there may be multiple sites of origin in the body for the disease.
Dr Labrie, said people should not rush to have their appendix removed.
“It would be much more wise to control or dampen excessive formation of alpha synuclein to tune down the overabundance or potentially to prevent its escape.”
The idea that the gut is involved in Parkinson’s is rapidly gaining attention.
Patients often report digestive disorders, cutting the vagus nerve is linked to a lower level of Parkinson’s and animal studies have suggested bacteria that live in the gut are key.
The study showed nearly everybody tested had alpha-synuclein protein in their the appendix.
And there were some differences in the structure of the protein between healthy people and Parkinson’s patients.
But the hunt for the origins of Parkinson’s still cannot explain why the disease develops in some people but not others.
Prof Tom Foltynie of the Institute of Neurology at UCL said, “The question that remains is why Parkinson’s develops in only some people with abnormal alpha synuclein aggregation in the gut, and why others are seemingly resistant. An answer to this will help us intervene to prevent those processes linking gut pathology to brain disease.”
Source: The Guardian