Parkinson’s disease (PD) is a progressive condition that affects the brain, around 1 in 500 people are affected by PD in the UK. In PD, some of the cells in the brain die and this causes less of a chemical called dopamine. PD also causes the build-up of a protein called alpha-synuclein in the brain.
Parkinson’s disease affects different people in different ways, so the disease symptoms are different for everyone. However, Parkinson’s disease is often associated with symptoms that affect a person’s movement, including tremor, slowed movement and stiffness (rigidity). The motor symptoms of PD can often be very obvious, however, Parkinson’s disease also causes a range of non-motor symptoms including mental health problems such as depression, anxiety and hallucinations.
Drugs and therapies can be used to manage the symptoms of PD in order to improve quality of life for people who are affected. However, there is currently no cure for PD as therapies are limited to managing disease symptoms.
Scientists are working to better understand PD with the hope of ultimately treating the disease in patients. In order to do this, genetically modified mouse models of the disease were used to answer fundamental scientific questions. Researchers from the University of Wisconsin used genetically modified mice that were designed to have high levels of the protein alpha-synuclein which is thought to cause PD.
The researchers were specifically interested in bacteria in the stomachs of the animals and to see if this linked in any way to the symptoms of PD. The results showed that mice without bacteria in their stomachs, so called sterile mice, remained healthy. Whereas those with bacteria in their stomachs developed some of the symptoms of PD. Further studies showed that transplanting bacteria from people affected by PD into mice meant that the mice developed more symptoms than mice that had bacteria transplanted from people who were not affected by PD.
This research in genetically modified mice is really important for PD. Until now PD was thought to be predominantly a brain disease, but this new study suggests that stomach bacteria are also involved in developing the symptoms of PD. But how do bacteria in the stomach affect the brain? Scientists are still unsure, but they suggest that this might be due to bacteria in the stomach releasing chemicals that over activate the brain. It is thought that stomach bacteria cause the release of chemicals in the body which then trigger immune cells to cause damage to the brain.
At the moment this research is limited to pre-clinical studies in genetically modified mice, so it will be important to see in other studies if the similar results are observed in people with PD. However, this change in thinking, that PD might just not be a disease of the brain, is really important for future research. It might be that further research looking to find treatments for PD now focuses on stomach bacteria as well as the brain.
The results of this study must not be over interpreted, as the findings need to be confirmed in people. However, this is really exciting for the PD community and paves the way for further research to greater understand the condition in the hope that one day we will be able to find a cure for this disease.