The new studies show that some types of a sugar called cyclohexanehexol--also known as inositol--prevented the accumulation of amyloid deposits, a hallmark of Alzheimer's disease. Scyllo-inositol treatment also improved cognitive abilities in the mice and allowed them to live a normal lifetime. The study appeared in advance online publication of the journal Nature Medicine on June 11, 2006.
HHMI international research scholar and senior author Peter St George-Hyslop cautioned that the chemicals tested in these studies are not the type of inositol sold commercially as a nutritional supplement. That type--myo-inositol--has been shown previously to be ineffective at breaking up amyloid aggregates, he said.
In the brain of a person with Alzheimer's disease, small proteins called amyloid aggregate into plaques, and a protein called tau clumps into neurofibrillary tangles. The brain becomes inflamed and neurons atrophy and die. It's not completely clear what kind of amyloid peptide (monomers, oligomeric aggregates, or fibrillar aggregates) is responsible for the onset of disease, said St George-Hyslop of the University of Toronto. "Because we were able to show that scyllo-inositol specifically dispersed the high-molecular-weight oligomeric aggregates, this study confirms that the initiating event is the accumulation of oligomeric aggregates of amyloid peptide," he said.
Previous work by JoAnne McLaurin, also of the University of Toronto and lead author of the Nature Medicine paper, showed that several types of inositol could stop amyloid proteins from aggregating in test tubes. To see if these compounds could do the same in living animals, St George-Hyslop, M
Contact: Jennifer Donovan
Howard Hughes Medical Institute