“The idea that lithium deficiency could be a cause of Alzheimer’s disease is new and suggests a different therapeutic approach,” said senior author Bruce Yankner, professor of genetics and neurology in the Blavatnik Institute at HMS, who in the 1990s was the first to demonstrate that amyloid beta is toxic.
The study raises hopes that researchers could one day use lithium to treat the disease in its entirety rather than focusing on a single facet such as amyloid beta or tau, he said.
One of the main discoveries in the study is that as amyloid beta begins to form deposits in the early stages of dementia in both humans and mouse models, it binds to lithium, reducing lithium’s function in the brain. The lower lithium levels affect all major brain cell types and, in mice, give rise to changes recapitulating Alzheimer’s disease, including memory loss.
The authors identified a class of lithium compounds that can evade capture by amyloid beta. Treating mice with the most potent amyloid-evading compound, called lithium orotate, reversed Alzheimer’s disease pathology, prevented brain cell damage, and restored memory.
Although the findings need to be confirmed in humans through clinical trials, they suggest that measuring lithium levels could help screen for early Alzheimer’s. Moreover, the findings point to the importance of testing amyloid-evading lithium compounds for treatment or prevention.
Other lithium compounds are already used to treat bipolar disorder and major depressive disorder, but they are given at much higher concentrations that can be toxic, especially to older people. Yankner’s team found that lithium orotate is effective at one-thousandth that dose — enough to mimic the natural level of lithium in the brain. Mice treated for nearly their entire adult lives showed no evidence of toxicity.
“You have to be careful about extrapolating from mouse models, and you never know until you try it in a controlled human clinical trial,” Yankner said. “But so far the results are very encouraging.”
Lithium depletion is an early sign of Alzheimer’s
Yankner became interested in lithium while using it to study the neuroprotective protein REST. Finding out whether lithium is found in the human brain and whether its levels change as neurodegeneration develops and progresses, however, required access to brain tissue, which generally can’t be accessed in living people.
So the lab partnered with the Rush Memory and Aging Project in Chicago, which has a bank of postmortem brain tissue donated by thousands of study participants across the full spectrum of cognitive health and disease.
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