Gut microbiome can reveal risk of Parkinson’s, scientists say | Parkinson’s disease

Changes to the microbes that live in the gut may identify people at highest risk of Parkinson’s disease long before symptoms appear, according to work that also raises hopes for new therapies.

Researchers have discovered characteristic changes in the gut microbiome that are more pronounced in people at genetic risk for Parkinson’s disease and even more pronounced in those diagnosed with the disease.

This signature could help doctors spot patients at risk for Parkinson’s years before they show obvious symptoms and suggests that healthier diets and treatments that reshape the microbiome could prevent or delay the disease.

Professor Anthony Schapira, head of clinical and movement neuroscience at University College London and principal investigator of the study, said it was the first time a microbial signature in Parkinson’s patients had been observed in people who had a genetic susceptibility but had not yet developed symptoms. The signature appears to strengthen as the disease progresses.

“These same changes may be seen in a small proportion of the general population, which may put them at increased risk,” Schapira said.

Cases of Parkinson’s disease have doubled over the past 25 years, with more than 8.5 million people worldwide now living with the disease. The disease causes progressive brain damage, leading to tremors, slow movements, and stiff, inflexible muscles. Patients often experience depression, anxiety, sleep and memory problems, and balance difficulties.

Parkinson’s disease is caused by the death of neurons in a part of the brain called the substantia nigra. The loss of nerve cells leads to a drop in dopamine in the brain, which is responsible for many of the disease’s symptoms. There is no cure, but medications that boost dopamine can help, along with physiotherapy and surgery.

The UCL team analyzed clinical and faecal data from 271 patients with Parkinson’s disease, 43 people with a risk gene for the disease but without clinical symptoms and 150 healthy people.

The abundance of more than a quarter of gut microbes, or 176 species, differed in people with Parkinson’s disease compared to the healthy group. The changes were not due to medications. A similar trend was observed in people who were genetically predisposed to Parkinson’s disease but had no symptoms.

The scientists corroborated the findings with other medical data from 638 people with Parkinson’s disease and 319 healthy controls from the United Kingdom, South Korea and Turkey. According to Nature Medicine, a small proportion of healthy people had the microbiome signature, suggesting they were potentially at risk for the disease.

It’s not clear whether the microbial signature causes Parkinson’s disease or vice versa, or both, but Schapira said changes in the microbiome could alter the production of a protein called alpha-synuclein, which plays an important role in neuron damage in the disease.

“Certain bacteria cause inflammation in the gut wall that increases alpha-synuclein, which is then transported along the vagus nerve from the gut to the brain and then into brain cells affected by Parkinson’s disease,” he said. The vagus nerve carries information between the brain and major organs.

More work and clinical trials are needed to understand how gut microbes are linked to Parkinson’s and whether reshaping the microbiome could protect against the disease, but dietary changes could help. In the study, people with an abnormal microbiological signature ate more processed foods and saturated fats than fruits, vegetables, fiber, fish and lentils.

Claire Bale, associate director of research at Parkinson’s UK, said the study added to growing evidence that the gut microbiome was important in Parkinson’s disease. “The results indicate that changes in the microbiome can occur in the early stages of the disease and that the magnitude of these changes can be correlated with disease progression,” she said.

“Over the past decade, we have seen the impact of physical activity on managing symptoms and potentially slowing the progression of the disease. Our growing understanding of the gut microbiome offers similar hope that dietary modification could benefit people with Parkinson’s disease.”