Despite being the most frequently occurring neurodegenerative disease in the US, where it affects over 1 million people, Parkinsonâ€™s disease is difficult to diagnose: there are no standard clinical tests.
This means the disease is often diagnosed only when symptoms like tremors and rigidity emerge, which is well after many brain cells have been destroyed.
Researchers from Beth Israel Deaconess Medical Center (BIDMC), a teaching hospital of Harvard Medical School, found that elevated levels of a nervous system protein called alpha-synuclein can be detected in the skin of people with Parkinsonâ€™s disease.
They suggest the protein could serve as a biomarker of the disease, helping to spot it before symptoms emerge, when it is hard to detect with current methods.
â€œA reliable biomarker could help doctors in more accurately diagnosing Parkinsonâ€™s disease at an earlier stage and thereby offer patients therapies before the disease has progressed.â€
Main component of abnormal protein clumps in brain cells
Alpha-synuclein occurs throughout the nervous system, and although we do not know much about what it does, scientists have found it is the main component of the abnormal clumps of protein or Lewy bodies, that form inside the brain cells of people with Parkinsonâ€™s disease. There is also growing evidence to suggest the protein plays a key role in the development of the disease.
Prof. Freeman says:
â€œAlpha-synuclein deposition occurs early in the course of Parkinsonâ€™s disease and precedes the onset of clinical symptoms.â€
Signs of the protein accumulating around nerves in the skin
The researchers had a hunch that they might find earlier signs of Parkinsonâ€™s by looking at the autonomic nervous system in the skin, and at alpha-synuclein, in particular.
There is already a view that symptoms connected to the autonomic nervous system, such as changes in temperature and blood pressure regulation, and bowel function, may precede the motor system symptoms seen in people with Parkinsonâ€™s.
Autonomic nervous system changes also occur in the skin, such as excessive or diminished sweating, changes in skin color and temperature. These symptoms occur in nearly two-thirds of patients with Parkinsonâ€™s disease (PD), says Prof. Freeman.
â€œThe skin can provide an accessible window to the nervous system and based on these clinical observations, we decided to test whether examination of the nerves in a skin biopsy could be used to identify a PD biomarker,â€ he adds.
Higher levels of alpha-synuclein in skin structures of Parkinsonâ€™s patients
They took their ideas into a study of 20 patients with Parkinsonâ€™s disease and 14 controls matched for age and gender.
The participants underwent exams and tests of the autonomic nervous system. To measure alpha-synuclein levels, and density of nerve fibers, the participants had skin biopsies on the leg.
The researchers found their hunch was right: the Parkinsonâ€™s patients had higher levels of alpha-synuclein in the skin nerves supplying the sweat glands and the pilomotor muscles (the ones that produce goose bumps).
They found higher levels of alpha-synuclein in the autonomic nerves of the skin were linked to more advanced Parkinsonâ€™s symptoms and worse functioning of the autonomic nervous system.
Freeman says there is a strong and unmet need for a biomarker for Parkinsonâ€™s disease, and:
â€œAlpha-synuclein deposition within the skin has the potential to provide a safe, accessible and repeatable biomarker.â€
The researchers now plan to find out if the protein accumulates in the skin nerves of people at risk for Parkinsonâ€™s disease, and also if testing for it can distinguish Parkinsonâ€™s from other neurodegenerative diseases.
Earlier this year, researchers at the Mayo Clinic in the US proposed a saliva test for Parkinsonâ€™s disease.
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