Low levels of copper in drinking water combined with a high-cholesterol diet somehow promotes an Alzheimer's-like pathology in rabbits, a new study finds. If the results hold up in humans, people may need to reduce not only their blood cholesterol levels but also their consumption of copper-containing drinking water.
The work is the outgrowth of a serendipitous finding reported last year. Pathologist Larry Sparks, then at the University of Kentucky Chandler Medical Center in Lexington, found that feeding high-cholesterol diets to rabbits stepped up the accumulation of b amyloid--the small protein widely blamed for the devastating brain degeneration of Alzheimer's disease. He also spotted structures resembling the senile plaques of Alzheimer's brains. But oddly, at Sparks's current institution, Sun Health Research Institute in Sun City, Arizona, the same diet didn't boost b amyloid as much--a discrepancy he eventually traced to the fact that animals at Sun Health drank distilled water, whereas they previously had been given ordinary tap water. Analysis of the labs' water samples pointed to copper ion content as the key factor.
In the current work, reported online this week in the Proceedings of the National Academy of Sciences, Sparks and behavioral scientist Bernard Schreurs of West Virginia University in Morgantown spiked distilled water with copper sulfate at a concentration that was one-tenth the maximum allowed in drinking water in the U.S. Rabbits who got both the copper-laced water and the high-cholesterol diet had a 50% greater increase in the number of b-amyloid-producing neurons in their brains than did rabbits fed the same diet but with plain distilled water. They also suffered from plaque-like structures that were rare in other animals and performed much more poorly on a complex learning task than the other rabbits did.
Still, other Alzheimer's researchers aren't so sure that the brain changes reflect the true pathology of the disease. For example, Ashley Bush of Harvard Medical School in Boston suggests that the rabbit neurons may have turned up their b amyloid production as part of a normal response aimed at detoxifying the copper ions. He notes that the plaque-like structures seen in the animals are not surrounded by deteriorating nerve endings, as is commonly observed in Alzheimer's plaques, although Sparks suggests that his experiments were just too short for that to have happened.
Researchers would like to see additional experiments to assess the effects of copper on widely used mouse models of Alzheimer's. Epidemiological studies might reveal whether there are any links between copper in the water and human Alzheimer's. Marcelle Morrison-Bogorad of the National Institute on Aging in Bethesda, Maryland, describes the work of Sparks and Schreurs as "fascinating." But she adds, "it's far too early to get anyone upset" about copper in tap water. In other words, don't tear out your copper plumbing yet.