Tears could hold the biological markers of Parkinson’s disease, according to the findings of a preliminary USA study, revealed last night.
Researchers at the University of Southern California, Los Angeles, found that vital clues are held in specific proteins of a teardrop.
The results of the study, which examined tear samples from 55 people with Parkinson’s disease and compared them with samples from 27 controls, is due to be presented at the American Academy of Neurology’s 70th Annual Meeting in April.
Dr Mark Lew, of the Keck School of Medicine of the University of Southern California in Los Angeles and a Fellow of the American Academy of Neurology, described using a non-invasive method to ascertain if a person has the disease as exciting.
The research team investigated tears because they contain several proteins produced by the secretory cells of the tear gland and because Parkinson’s can affect nerve function outside of the brain, they believed that a change in nerve function could be seen in the protein levels in tears.
Protein levels of four proteins were analysed and the investigators found differences in the levels of alpha-synuclein in the tears of people with Parkinson’s compared to controls.
Levels of oligomeric alpha-synuclein, which is alpha-synuclein that has formed aggregates implicated in nerve damage in Parkinson’s, were also significantly different compared to controls.
Dr Lew’s preliminary study found that total levels of alpha-synuclein were decreased in people with Parkinson’s, with an average of 423 picograms of that protein per milligram (pg/mg) compared to 704 pg/mg in people without Parkinson’s.
Levels of oligomeric alpha-synuclein were increased in people with Parkinson’s, with an average of 1.45 nanograms per milligram of tear protein (ng/mg) compared to 0.27 ng/mg in people without the disease.
“Knowing that something as simple as tears could help neurologists differentiate between people who have Parkinson’s disease and those who don’t in a non-invasive manner is exciting,” said Dr Lew.
“And because the Parkinson’s disease process can begin years or decades before symptoms appear, a biological marker like this could be useful in diagnosing, or even treating, the disease earlier.”
The team says further research should be carried out to establish if the protein changes are detectable in tears in the earliest stages of the disease, before symptoms start.
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