Copper appears to be one of the main environmental factors that trigger the onset and enhance the progression of Alzheimer's disease by preventing the clearance and accelerating the accumulation of toxic proteins in the brain.
That is the conclusion of a study appearing today in the journal Proceedings of the National Academy of Sciences.
"It is clear that, over time, copper's cumulative effect is to impair the systems by which amyloid beta is removed from the brain," said Rashid Deane, Ph.D., a research professor in the University of Rochester Medical Center (URMC) Department of Neurosurgery, member of the Center for Translational Neuromedicine, and lead author of the study. "This impairment is one of the key factors that cause the protein to accumulate in the brain and form the plaques that are the hallmark of Alzheimer's disease."
Copper's presence in the food supply is ubiquitous. It is found in drinking water carried by copper pipes, nutritional supplements, and in certain foods such as red meats, shellfish, nuts, and many fruits and vegetables. The mineral plays an important and beneficial role in nerve conduction, bone growth, the formation of connective tissue, and hormone secretion.
However, the new study shows that copper can also accumulate in the brain and cause the blood brain barrier – the system that controls what enters and exits the brain – to break down, resulting in the toxic accumulation of the protein amyloid beta, a by-product of cellular activity. Using both mice and human brain cells Deane and his colleagues conducted a series of experiments that have pinpointed the molecular mechanisms by which copper accelerates the pathology of Alzheimer's disease.
Under normal circumstances, amyloid beta is removed from the brain by a protein called lipoprotein receptor-related protein 1 (LRP1). These proteins – which line the capillaries that supply the brain with blood – bind with the amyloid beta found in the brain tissue and escort them into the blood vessels where they are removed from the brain.
The research team – "dosed" normal mice with copper over a three month period. The exposure consisted of trace amounts of the metal in drinking water and was one-tenth of the water quality standards for copper established by the Environmental Protection Agency.