There is not one, but two Parkinson's diseases, a study suggests. One would indeed take root in the intestines and the other in the brain. These results could help explain why patients sometimes present with very different symptoms and courses. This work could also help improve our ability to treat these diseases in the future.
Parkinson's disease is characterized by the destruction of "dopamine neurons", involved in controlling body movements. Some symptoms then develop, such as stiffness, slowness of movement and tremor at rest. The number of people affected by the disease worldwide is estimated at 6.3 million, including around200,000 in France .
While the mechanism of Parkinson's disease is known, the causes remain unknown. To understand its biological roots, researchers from Aarhus University and Aarhus University Hospital, Denmark, used PET and MRI imaging techniques to examine patients with different stages of disease progression.
The team also looked at several people who had not yet been diagnosed, but who suffered from REM sleep behavior disorder. The study indeed recalls that it is a precursor sign of the disease .
That said, this work revealed that some patients had their dopamine pathways affected before their heart or intestines were affected. For others, conversely, scans showed damage to the nervous systems of the intestines and heart before damage to the dopaminergic system of the brain was visible.
For the researchers, these results show that ourcurrent understanding of how the disease develops and progresses is flawed .
“Until now, many people have viewed the disease as relatively homogeneous and defined it based on the classic movement disorders. But at the same time, we wondered why there was such a big difference between patients' symptoms “, explains Professor Per Borghammer. “Using advanced scanning techniques, we have shown that Parkinson’s disease can actually be divided into two variants that start at different places in the body “.
The researchers named the two variants of the disease based on where they appeared:"body first for those born in the gut and "brain first for the one that first develops in the brain.
For the first, Per Borghammer suggests that the study of the intestinal microbiota could lead to a better understanding of the pathology. This could ultimately open the way to new therapeutic approaches s.
"Parkinson's patients have long been shown to have a different gut microbiome than healthy people, but we don't really understand the meaning “, emphasizes the researcher. "Now that we are able to identify both types of disease, we can look at the risk and possible genetic factors that may be different" .
Studying the "brain first" variant will be "more challenging “, he admits, insofar as his symptoms appear late . It therefore seems more difficult to be able to diagnose the patients concerned early enough to be able to slow down the disease .
