Tears as Biological Marker
A new study has discovered the potential for tears to be the best biological markers of Parkinson’s disease. Why? Because the test is noninvasive and inexpensive.
According to a study headed by author Mark Lew, MD, of the Keck School of Medicine of the University of Southern California in Los Angeles and a Fellow of the American Academy of Neurology, tears may hold clues to whether someone has Parkinson’s disease.
Lew said, “We believe our research is the first to show that tears may be a reliable, inexpensive and noninvasive biological marker of Parkinson’s disease.”
It’s not always easy to diagnose Parkinson’s disease because it can begin years or decades before symptoms. But the new discovery may be the best thing to happen in the field of neuroscience.
The preliminary study will be presented at the American Academy of Neurology’s 70th Annual Meeting in Los Angeles, April 21 to 27, 2018.
What’s In The Tears?
The researchers discovered that tears have various proteins produced by the secretory cells of the tear gland. The proteins levels may be seen according to any change in nerve function.
For the study, tear samples from 55 people with Parkinson’s were compared to tear samples from 27 people who did not have Parkinson’s but who were the same age and gender. Tears were analyzed for the levels of four proteins.
Researchers found differences in the levels of a particular protein, alpha-synuclein, in the tears of people with Parkinson’s compared to controls. Additionally, levels of another form of alpha-synuclein, oligomeric alpha-synuclein, which is alpha-synuclein that has formed aggregates that are implicated in nerve damage in Parkinson’s, were also significantly different compared to controls. It is also possible that the tear gland secretory cells themselves produce these different forms of alpha-synuclein that can be directly secreted into tears.
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. But 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. A picogram is 1,000 times smaller than a nanogram.
“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 noninvasive manner is exciting,” said Lew.
The researchers believe that more research now needs to be done in larger groups of people to investigate whether these protein changes can be detected in tears in the earliest stages of the disease, before symptoms start.
Parkinson’s disease is due to the loss of brain cells that produce dopamine. Early signs and symptoms of Parkinson’s disease include tremors or trembling, slow movement, body rigidity and stiffness, and problems walking.