Jan. 31, 2000 (Tuscaloosa, Ala.) -- For the first time, scientists have shown that the male hormone testosterone interferes, at least in brain cells from rodents, with the production of beta-amyloid plaque, a sticky protein substance believed to be a prime contributor to Alzheimer's disease. The results raise the possibility that testosterone supplements may offer protection against Alzheimer's.
In 1906, German psychiatrist Alois Alzheimer first described the debilitating disease that bears his name. It was rare when he first identified the disease, but as life expectancy has lengthened, the incidence of the disease has increased substantially. Some 4 million Americans -- one in five of those between ages 75 and 84 and nearly half of those 85 and older -- are now afflicted. That number is expected to soar as the large population of baby boomers enters their senior years.
The most recent testosterone study is by a group of researchers led by Paul Greengard, PhD, director of the Laboratory of Molecular and Cellular Neuroscience at New York's Rockefeller University. He and his colleagues at the Fisher Center for Research on Alzheimer's Disease and the Laboratory of Mass Spectrometry, were looking for a way of slowing the secretion of a substance known as beta-amyloid plaque. In the brains of some people, it forms plaque that chokes off and inflames the nerve cells of the brain -- the very foundation of our thinking abilities.
Several studies have shown that estrogen replacement therapy appears to protect women against the development of Alzheimer's. Researchers at Rockefeller University had previously shown in lab experiments that treating nerve cells with a form of the female sex hormone estrogen reduces the secretion of amyloid. Since testosterone is the male hormone, the researchers wondered if it would have a similar effect on brain cells.
It does, according to study co-investigator Gunnar K. Gouras, MD. He tells WebMD, "Our group is the first to show that testosterone can be used to retard the production of beta-amyloid in brain cells."
What the researchers did was treat the two types of cells from the brains of rodents with testosterone for 10 days and compare the production of amyloid by those cells to the amount of amyloid produced by untreated rodent cells. The results revealed that the testosterone-treated cells produced 30-45% less amyloid protein than the untreated cells. The implication, according to Gouras, an assistant professor of neurology at Weill Medical College of Cornell University, "is that testosterone may be protective against Alzheimer's disease and someday it may be used to treat or prevent that disease."
"It's an excellent piece of basic science research that helps us understand the mechanisms involved in Alzheimer's disease and points to ways we might intervene," Monique Cherrier, PhD, tells WebMD. "It provides us with the scientific foundation and rationale we need to go to funding authorities for additional funds to further study testosterone in humans." Cherrier is a neuropsychologist at the University of Washington School of Medicine in Seattle.
Cherrier's own groundbreaking work showed improvement in both spatial and verbal memory, first in healthy elderly men treated with testosterone, and then in elderly male patients with Alzheimer's.
"It's very encouraging to see research attention being given to aging men at both the clinical and basic research level," Sam E. Gandy, MD, tells WebMD. "It's gratifying that there is evidence indicating that testosterone replacement therapy may be as helpful to men as estrogen replacement therapy is for women." Gandy is professor of psychiatry and cell biology at the Nathan Kline Institute and New York University in New York City.