ROBERT SIEGEL, host:
From NPR News, this is All Things Considered. I'm Robert Siegel.
MICHELE NORRIS, host:
And I'm Michele Norris. The most common explanation for Alzheimer's disease is that it's caused by sticky clumps of something called amyloid. It gradually builds up in the brain and kills off brain cells. But two new studies suggest that a very different and far more familiar substance may be just as important, calcium. NPR's John Hamilton reports.
JOHN HAMILTON: While most researchers have concentrated on the role of amyloid plaques in Alzheimer's, a few have long suspected that the real culprit might be calcium. Kevin Foskett of the University of Pennsylvania is one of those researchers. He says there wasn't that much evidence the calcium hypothesis was right until today's publication of the two new studies.
Dr. KEVIN FOSKETT (School of Medicine, University of Pennsylvania): Taking these two papers together will force everyone in the Alzheimer's field to put the calcium hypothesis much more on the map than it has been.
HAMILTON: Foskett, who is an author of both papers, says the hypothesis goes like this. Calcium molecules pass in and out of individual brain cells.
Dr. FOSKETT: Cells can let calcium come in from the outside, or they also have stores of calcium that they keep inside them. And they can release that calcium from the inside of the cell into the cytoplasm.
HAMILTON: In order to stay healthy, brain cells need to maintain just the right amount of calcium at any given moment. That depends on cells responding to signals from elsewhere in the brain. Foskett and others think an abnormal response to these signals leads to abnormal calcium levels in brain cells, which ultimately lead to Alzheimer's.
One of the new studies appears to confirm the link between calcium and Alzheimer's. Philippe Marambaud of Albert Einstein Medical College says the study identifies a gene linked to both Alzheimer's and the calcium balance in brain cells. He says people who carry one copy of the gene are at least 44 percent more likely to develop the disease.
Dr. PHILIPPE MARAMBAUD (Assistant Professor of Pathology, Albert Einstein Medical College): So it's extremely significant, and it would potentially affect a lot of individuals.
HAMILTON: This is only the second gene that's been linked to the most common form of Alzheimer's, and Marambaud says scientists know a lot about the chemicals that it produces in the brain.
Dr. MARAMBAUD: So we have potentially not only identified a new risk factor, but also a gene product that could be targeted for drug discovery and therapy.
HAMILTON: Future drugs might be designed to correct abnormal calcium levels in brain cells. So far, efforts to treat Alzheimer's have focused on preventing or eliminating the buildup of amyloid.
The second new study suggests how an imbalance in calcium might actually cause Alzheimer's. Researchers looked at brain cells from people who have a rare inherited form of the disease that can strike a person before they reach 40. They found that these people carry genes that not only cause amyloid buildup but also problems with calcium regulation. And the study found that when calcium regulation went awry, brain cells produced more amyloid. Sam Gandy with the Alzheimer's Association says that suggests a brand new way of looking at an old disease.
Mr. SAM GANDY (Representative, Alzheimer's Association): It seems that calcium and amyloid have a sort of hand and glove or even vicious cycle sort of relationship. So one can cause the other, and they can begin a vicious cycle that we think can lead to the disease.
HAMILTON: All the scientists warned against trying to prevent Alzheimer's by changing the amount of calcium in your diet or by taking drugs that affect the way cells used calcium. The new studies appear in the journal "Cell and Neuron." John Hamilton, NPR News.
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