Causes of Alzheimer’s and the Role of Blueberries

Although the exact cause of Alzheimer’s is not completely understood, experts have recently identified one mechanism involving the insufficient breakdown and recycling of amyloid protein in the brain.

Agricultural Research Service neuroscientist James Joseph and colleagues published an Alzheimer’s disease model study in Nutritional Neuroscience.

They studied mice that carried a genetic mutation for promoting increased amounts of amyloid beta, a protein fragment found within the telltale neuritic plaque, or “hardening of the brain,” seen in Alzheimer’s disease.

James Joseph heads the Neuroscience Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University in Boston.

Experts have recently identified one mechanism involving the insufficient breakdown and recycling of amyloid protein in the brain. That mechanism is both genetic and physiological.

In those individuals, normally harmless amyloid protein turns into fragments of amyloid beta, which build up as plaque in the brain rather than being escorted into cellular recycling. That action leads to cell death and weakened neuronal communication.

In the mouse study, beginning at age 4 months - early adulthood - half the brain-plaqued group was fed a diet that included blueberry extract for 8 months. The other half was fed standard rat chow and so was a control group of mice that didn’t carry the amyloid-plaque mutation.

At 12 months - early middle age - all groups were tested for their performance in a maze.

The brain-plaqued mice that were fed the blueberry extract performed as well as the healthy control mice and performed much better than their brain-plaqued peers fed standard chow.

A look at the plaqued brains of both the blueberry-fed and chow-fed mice after death revealed no difference in the number of brain plaques in either group. “Amyloid-beta-induced plaques are only one aspect of Alzheimer’s disease,” said Agricultural Research Service neuroscientist James Joseph. “But the fact that we saw a diet-induced behavioral difference, despite a similarity in plaque density in both these animal groups, is significant.”

The team found increased activity of a family of enzymes called “kinases” in the brains of the amyloid-plaqued mice that were fed blueberry extract. Two kinases found in particular, ERK and PKC, are important in mediating cognitive function, such as converting short-term memory to long-term.

“These kinase molecules are involved in signaling pathways for learning and memory,” says Joseph. “It could be that the increased kinase activity within the plaque-ridden brains of the blueberry-fed mice enhanced the signaling in certain receptors.”

Reference:
USDA, Agricultural Research Service

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