Studies point to gut microbiome and hair changes as potential Parkinson’s disease signals

Changes to microbes that live in the gut can identify people at greater risk of Parkinson’s disease long before symptoms develop, according to work that found a microbial signature that was more pronounced in people with a genetic risk and even more stark in those diagnosed with the disease. Separate research in China found that hair samples from patients with Parkinson’s disease showed significantly lower levels of iron and copper, along with higher levels of manganese and arsenic.

Researchers discovered signature changes in the gut microbiome that are more pronounced in people with a genetic risk for Parkinson’s and even more stark in those diagnosed with the disease. The signature could help doctors spot patients at risk of Parkinson’s years before they display clear symptoms and suggests that healthier diets and treatments that reshape the microbiome might prevent or delay the disease.

The team analysed clinical and faecal data from 271 Parkinson’s patients, 43 people with a risk gene for the disease but no clinical symptoms, and 150 healthy people. The abundance of more than a quarter of the gut microbes, or 176 species, differed in those with Parkinson’s disease compared with the healthy group. The changes were not driven by medication. A similar pattern was seen in those genetically predisposed to Parkinson’s but who did not have symptoms.

The scientists corroborated the findings in further medical data from 638 people with Parkinson’s and 319 healthy controls from the UK, South Korea and Turkey. A small proportion of healthy people had the microbiome signature, suggesting they were potentially at risk of the disease, according to Nature Medicine.

It is unclear whether the microbial signature drives Parkinson’s or vice versa, or both, but changes in the microbiome could alter the production of a protein called alpha-synuclein, which plays an important role in damaging neurons in the disease. Certain bacteria cause inflammation in the gut wall that increases alpha-synuclein, which is then transported up the vagus nerve from the gut to the brain and then into the brain cells affected in Parkinson’s.

In the hair study, researchers analyzed the hair of 60 patients with Parkinson’s and compared the results with those of healthy, age-matched controls. According to a pre-proof paper, hair samples from patients with Parkinson’s disease showed significantly lower levels of iron and copper, along with higher levels of manganese and arsenic. The iron deficiency in the hair of human Parkinson’s patients and mouse models was the most consistent and noticeable change.

In further experiments involving mouse models, the researchers also found lower levels of iron in hair, and this change was closely connected to dysfunction in the gut. The intestinal barrier in the mice with a Parkinson’s-like disease appeared impaired. Their genes involved in iron absorption were downregulated, and they showed increased activity in genes involved in microbial iron acquisition, possibly leading to broad iron deficiency across the body.

In the microbiome study, people with the abnormal microbiome signature ate more processed foods and saturated fats rather than fruit, vegetables, fibre, fish and lentils. The hair study said elevated arsenic in the hair could be caused by environmental exposure, and those with Parkinson’s reported eating more animal offal and shellfish, which are more likely to contain arsenic.

Further work and clinical trials are needed to understand how gut microbes are linked to Parkinson’s and whether reshaping the microbiome could shield against the disease. Further research is now needed to verify the hair pattern among larger cohorts, and to test the mechanisms uniting iron deficiency and Parkinson’s disease.