It is thought that about 145,000 people in the UK are living with Parkinson’s disease, a neurological condition that can lead to mobility problems, including slowness and tremors, as well as other symptoms such as memory difficulties. There are treatments to help manage symptoms but as yet the disease cannot be slowed or cured.
The researchers, based at King’s College London, say the latest findings could eventually lead to new ways to identify people who might go on to develop Parkinson’s; the discoveries could also confirm diagnoses, monitor the disease progression, and aid the development and testing of drugs. Those developments could be some way off though, some scientists have said.
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| A patient with Parkinson’s disease is treated with thalamic stimulation, with electrodes inserted into the brain. Photograph: Alamy |
Most of the time Parkinson’s appears to have no known cause, so people affected by the disease are not studied before their symptoms appear.
But the King’s College studies concerned with genetic mutations making the development of Parkinson’s disease more likely, could point to the warning signs.
Marios Politis, a professor and lead author of the research, said: “If you carry the gene [SNCA] it means it is almost certain you are going to develop Parkinson’s in the course of your life.”
A genetic mutation involving the SNCA gene was thought to have arisen in villages in the Peloponnese, Greece. But Politis said that carriers were rare. “I don’t think there are more than 100 [people who are known to have it],” he said.
Writing in the journal Lancet Neurology, Politis and his colleagues described how they brought 10 individuals with this genetic mutation to the UK from Greece, as well as four people from Italy. The participants were given assessments and brain scans.
While half of these participants had physical symptoms of Parkinson’s disease, the other seven did not. The team also analysed assessments and scans from 65 people with Parkinson’s disease who did not have genetic mutations linked to the condition.
People with Parkinson’s disease show a deterioration of systems in the brain that involve a neurotransmitter called dopamine, thought to be behind certain symptoms such as slowness of movement. However there have also been signs of deterioration involving another brain chemical, serotonin.
The research revealed that, compared with scans from 25 healthy participants, scans from participants with physical symptoms of Parkinson’s disease showed deterioration to both dopamine and serotonin systems in the brain – whether or not the individuals had the genetic mutation.
A loss of serotonin neurons was also seen in many regions in the brains of people who had the genetic predisposition to Parkinson’s but who did not have physical symptoms. Politis noted that these individuals had up to a 34% decrease in serotonin neurons compared with the healthy participants.
The changes were seen about 15 to 20 years before these individuals would typically start to show physical symptoms. In addition, these genetically predisposed participants showed no sign of deterioration in their dopamine system. “That by itself is a major breakthrough on how you see Parkinson’s disease,” said Politis.
He said the findings were exciting and could pave the way for screening, or even offer ways to test new drugs to find out whether they worked. “It is a completely new window on the disorder,” said Politis.
Roger Barker, professor of clinical neuroscience at the University of Cambridge, said the findings supported suspicions that the first signs of Parkinson’s might not be found in the dopamine system. But he said questions remained, including whether early changes in the serotonin system were found in other groups at risk of Parkinson’s, and whether these changes progressed over time – and could reliably predict when physical symptoms might appear.
He noted that the scans used were expensive and not widely available, raising questions about how the findings might be applied to screen people.
Beckie Port, research communication manager at Parkinson’s UK, said further research was needed, but suggested the findings might raise new possibilities. “We can’t currently give someone a brain scan in order to treat them earlier, to slow or stop the condition and perhaps prevent them from ever being diagnosed with Parkinson’s. But with this discovery a future where that is possible seems just a little closer.
