Parkinson’s is a terrible disease that eats away at the control of one’s body movements. As the dopamine-generating cells in the midbrain die, sufferers may continue to lose more of themselves with cognitive and behavioral issues such as dementia setting in. No one knows what causes the death of these cells.
Public figures such as Michael J. Fox and Muhammad Ali have increased awareness of the disease, which was first described in 1817. But while it’s been almost 200 years since English scientist Dr. James Parkinson published An Essay in the Shaking Palsy, there is still no cure.
Enter Mannitol: a common sweetener that has potential as a new treatment for Parkinson’s disease.
At Israel’s Tel Aviv University researchers in Dr. Daniel Segal’s lab are watching fruit flies crawl up walls. These are not the ordinary fruit flies you may find in your house; they are mutant flies that serve as an animal model for movement disorders like that of Parkinson’s. Unlike normal flies that freely scamper up and down the wall of test tubes in which they are kept, these mutant flies keep to the bottom of the tube. Similar to the mutant flies that I happened to create by chance during my undergraduate honor’s thesis research, the movement disorder flies are unable to keep control of their muscles enough to effectively scale vertical glass walls.
What is wrong with these mutant flies? Inside the fly brain a sticky protein called α-synuclein clumps together forming what are called Lewy bodies. These protein masses take over the midbrain, which in humans could lead to Parkinson’s, dementia, and Alzheimer’s disease. If the aggregation of α-synuclein could be prevented, it may serve as a potential treatment for such diseases as Parkinson’s. Mannitol is a substance that does just that.
Mannitol is white, powdery and sweet like sugar, but is much more impressive than the sugar we use every day. Originally isolated from the secretions of the flowering ash, it has been called manna, after the Biblical reference to a white food given to the Israelites by God in the desert. Mannitol is commonly used as a sugar-free sweetener for people with diabetes as it doesn’t increase blood glucose. It’s good at keeping things dry and tastes good, making it a good coating for candies, dried fruits, and gum. In the brain, mannitol is one of the few compounds that are able to cross the blood brain barrier – a barrier that keeps most foreign substances out of the blood going into the brain. Mannitol has been used to help transport pharmaceuticals into the brain, but in this case, mannitol itself goes into the midbrain and prevents aggregation of α-synuclein.
Back in the lab, fruit fly larvae are fed mannitol to see if it improves their movements when they grow to be adult flies. If a fly is able to climb 1cm in 18 seconds then it counts as a successful climb. Without mannitol, only 38 percent of the mutant flies can climb up the walls. But when they are fed mannitol as larvae, 70 percent of the mutant flies were able climb; that’s almost the same level as normal flies, of which 72 percent were successful climbers!
While flies are a long way from humans, this success heralds a new potential approach to treating Parkinson’s disease. From here, the normal course of research, from mammalian animal models to clinical trials will continue if mannitol continues to be successful in breaking up the a-synuclein clumps. Who would have thought that a common sweetener could potentially be the answer for treating Parkinson’s disease?
Copyright, 2013, Samantha Zhang. All rights reserved.