Alzheimer's memory problems originate with protein clumps floating in the brain, not amyloid plaques

The study, which was supported by the Oligomer Research Consortium of the Cure Alzheimer Fund and a MERIT Award from the Veterans Administration, appears in the journal Annals of Neurology.

"The buildup of amyloid plaques was described over 100 years ago and has received the bulk of the attention in Alzheimer's pathology," said lead author Sam Gandy, MD, PhD, Professor of Neurology and Psychiatry, and Associate Director of the Alzheimer's Disease Research Center, Mount Sinai School of Medicine. "But there has been a longstanding debate over whether plaques are toxic, protective, or inert."

Several research groups had previously proposed that rather than plaques, floating clumps of amyloid (called oligomers) are the key components that impede brain cell function in Alzheimer's patients. To study this, the Mount Sinai team developed a mouse that forms only these oligomers, and never any plaques, throughout their lives.

The researchers found that the mice that never develop plaques were just as impaired by the disease as mice with both plaques and oligomers. Moreover, when a gene that converted oligomers into plaques was added to the mice, the mice were no more impaired than they had been before.

"These findings may enable the development of neuroimaging agents and drugs that visualize or detoxify oligomers," said Dr. Gandy. "New neuroimaging agents that could monitor changes in Abeta oligomer presence would be a major advance. Innovative neuroimaging agents that will allow visualization of brain oligomer accumulation, in tandem with careful clinical observations, could lead to breakthroughs in managing, slowing, stopping or even preventing Alzheimer's.

"This is especially important in light of research reported in March showing that 70 weeks of infusion of the Abeta immunotherapeutic Bapineuzumab® cleared away 25 percent of the Abeta plaque, yet no clinical benefit was evident."

The Mount Sinai team included Michelle Ehrlich, MD, Professor of Pediatrics, Neurology, and Genetics and Genomic Sciences, and John Steele, a Mount Sinai graduate student, who performed the key analyses of the behavioral data. Dr. Charles Glabe, an oligomer expert and a member of the Cure Alzheimer Fund research consortium, is also a co-author of the paper. Dr Gandy is also a neurologist at the James J Peters Veterans Affairs Medical Center, an affiliate of Mount Sinai School of Medicine.