Research presented at the Genetics Society of America's ongoing annual Drosophila Conference in Washington, D.C., suggests that mannitol, a sugar substitute, could lead to a future treatment for Parkinson's disease
Researchers from Tel Aviv University describe experiments that could lead to a new approach for treating Parkinson's disease (PD) using a common sweetener, mannitol. This research is presented today at the Genetics Society of America's 54th Annual Drosophila Research Conference in Washington D.C., April 3-7, 2013.
Mannitol is a sugar alcohol familiar as a component of sugar-free gum and candies. Originally isolated from flowering ash, mannitol is believed to have been the "manna" that rained down from the heavens in biblical times. Fungi, bacteria, algae, and plants make mannitol, but the human body can't. For most commercial uses it is extracted from seaweed although chemists can synthesize it. And it can be used for more than just a sweetener.
The Food and Drug Administration approved mannitol as an intravenous diuretic to flush out excess fluid. It also enables drugs to cross the blood-brain barrier (BBB), the tightly linked cells that form the walls of capillaries in the brain. The tight junctions holding together the cells of these tiniest blood vessels come slightly apart five minutes after an infusion of mannitol into the carotid artery, and they stay open for about 30 minutes.
Mannitol has another, less-explored talent: preventing a sticky protein called α-synuclein from gumming up the substantia nigra part of the brains of people with PD and Lewy body dementia (LBD), which has similar symptoms to PD. In the disease state, the proteins first misfold, then form sheets that aggregate and then extend, forming gummy fibrils.
Certain biochemicals, called molecular chaperones, normally stabilize proteins and help them fold into their native three-dimensional forms, which are essential to their functions. Mannitol is a chemical chaperone. So like a delivery person who both opens the door and brings in the pizza, mannitol may be used to treat Parkinson's disease by getting into the brain and then restoring normal folding to α-synuclein.
Daniel Segal, PhD, and colleagues at Tel Aviv University investigated the effects of mannitol on the brain by feeding it to fruit flies with a form of PD that has highly aggregated α-synuclein.
The researchers used a "locomotion climbing assay" to study fly movement. Normal flies scamper right up the wall of a test tube, but flies whose brains are encumbered with α-synuclein aggregates stay at the bottom, presumably because they can't move normally. The percentage of flies that climb one centimeter in 18 seconds assesses the effect of mannitol.