Alzheimer’s protein can travel from the blood up to the brain.

Science News shares new research about how Alzheimer’s can happen – and, maybe, how we can prevent it. Those amyloid proteins that build up in the brain and cause all the cognitive and memory problems? They can lodge in the brain after being carried through the rest of the body’s blood supply:

The results, published online October 31 in Molecular Psychiatry, suggest that the protein amyloid-beta outside the brain may contribute to the Alzheimer’s disease inside it, says Mathias Jucker, a neurobiologist at the University of Tübingen in Germany. This more expansive view of the disease may lead scientists to develop treatments that target parts of the body that are easier than the brain to access.

Six pairs of mice — with one mouse engineered to produce gobs of human A-beta and one normal — were surgically joined for a year, causing blood mingling that’s far more extensive than that of a blood transfusion. After a year, the brains of the mice carrying the mutations were full of A-beta plaques, as expected. But these plaques were also inside the brains of the normal mice in the joined pairs.

The results don’t mean that Alzheimer’s is predominantly caused by factors in the blood. “We still think of Alzheimer’s as a brain disorder,” [study coauthor Weihan] Song [of the University of British Columbia in Vancouver] says. But factors in the blood, in some cases, might have the power to nudge the disease along, the results suggest.

A-beta is made by cells in the brain, but also by blood platelets, skin cells, muscles and other parts of the body. Normally, “there is a balance between A-beta inside and outside the brain,” Song says. But when this balance is thrown off, such as when the body is chock-full of the protein, or when the blood-brain barrier — the blockade that keeps potential dangers out of the brain — deteriorates with age, the brain may get an extra dose, Song proposes. By tweaking this balance, it’s possible that drugs or therapies that reduce A-beta in the body might help slow or prevent Alzheimer’s disease.