Neurodegenerative diseases such as Parkinson’s take years to develop before any noticeable symptoms emerge. Unfortunately, such conditions would be more effectively treatable before symptoms become apparent. Since there is no cure yet in sight, the best option is to prevent the disease from escalating. To do so, the disease has to be detected way before the person even notices that anything is off. Therein lies the biggest challenge for researchers – finding effective biomarkers that signal the disease in the earliest pre-clinical stage.
There have been a few promising diagnostic methods for Parkinson’s developed in recent years, like blood and eye tests, or even by detecting a specific smell secreted by the skin could signal the presence of the disease. All of these can help detect the disease early, but still not soon enough. There is however a new study from King’s College London that reveals distinct changes in the brain’s serotonin system can be identified up to 20 years before any Parkinson’s symptoms appear, suggesting a new biomarker to detect the disease at its earliest stages. The new research was published in the journal The Lancet Neurology.
Parkinson’s disease is typically associated with being a degenerative condition in the brain’s dopamine system. That’s why this new research is so interesting – it’s main focus is to examine how the disease also affects the brain’s serotonin systems. The researchers wanted to find out if the serotonergic system begins degenerating before symptoms appear.
To do so, they recruited subjects carrying a very rare genetic mutation that makes them almost certain to develop the disease at some point in their life. It took them two years to track down 14 people with the mutation because it is so rare that the researchers suspect only around 100 people in the world currently carry it. These participants served as perfect case studies for investigating neurological biomarkers that may precede the visible onset of the disease because it was almost certain they would develop it.
Next, they conducted comprehensive brain imaging to determine any neurological changes that preceded the onset of degenerative motor symptoms. “We found that serotonin function was an excellent marker for how advanced Parkinson’s disease has become,” said the first author on the study, Heather Wilson. “Crucially, we found detectable changes to the serotonin system among patients who were not yet diagnosed.”
What they discovered was that before there were even any changes to the brain’s dopamine system, there were already changes to the serotonin system. These changes to the serotonin system the study found may be the earliest sign of the disease ever identified.
Although, as exciting as this is, Derek Hill, an expert in medical imaging from University College London, says there are a couple of significant limitations to the research that will need to be overcome. “Firstly, they studied only 15 of the patients with a rare gene mutation. Their results may not scale up to larger studies,” explained Hill, who did not work on this new study. “Secondly, the imaging method they used is highly specialized and limited to a few research centers, so isn’t yet usable either to help diagnose patients or even to evaluate novel treatments in large clinical studies.”
Agreeing that the kind of PET scan used in the study is expensive and impossible to roll out as a broad clinical screening tool, the researchers’ next big goal is to develop and be able to deploy an affordable scanning technique. But before that, they will continue the study by verifying this serotonin system biomarker in larger cohorts.
No matter what, the study still offers substantial value to any researchers working on new Parkinson’s treatments. “Our results suggest that early detection of changes in the serotonin system could open doors to the development of new therapies to slow, and ultimately prevent, progression of Parkinson’s disease,” concluded chief investigator on the project, Marios Politis.
