Two new studies suggest that substances usually associated with dulling the mind — marijuana and red wine — may help ward off Alzheimer's disease and other forms of age-related memory loss. Their addition comes as another study dethrones folk remedy ginkgo biloba as proof against the disease.
At this week's meeting of the Society of Neuroscience in Washington, D.C., researchers from Ohio State University reported that THC, the main psychoactive substance in the cannabis plant, may reduce inflammation in the brain and even stimulate the formation of new brain cells.
Meanwhile, in the Nov. 21 issue of the Journal of Biological Chemistry, neurologist David Teplow of the University of California, Los Angeles reported that polyphenols — naturally occurring components of red wine — block the formation of proteins that build the toxic plaques thought to destroy brain cells. In addition, these substances can reduce the toxicity of existing plaques, thus reducing cognitive deterioration.
Together, the studies suggest scientists are gaining a clearer understanding of the mechanics of memory deterioration and discovering some promising approaches to prevention.
Previous research has suggested that polyphenols — which are found in high concentrations in tea, nuts and berries, as well as cabernets and merlots — may inhibit or prevent the buildup of toxic fibers in the brain. These fibers, which are primarily composed of two specific proteins, form the plaques that have long been associated with Alzheimer's disease.
UCLA's Teplow and his colleagues monitored how these proteins folded up and stuck to each other to produce aggregates that killed nerve cells in mice. They then treated the proteins with a polyphenol compound extracted from grape seeds. They discovered the polyphenols blocked the formation of the toxic aggregates.
"What we found is pretty straightforward," Teplow declared. "If the amyloid beta proteins can't assemble, toxic aggregates can't form, and, thus, there is no toxicity." If this also proves true in human brains, it means administration of the compound to Alzheimer's patients could "prevent disease development and also ameliorate existing disease," he said. Human clinical trials are upcoming.
At Ohio State, researchers led by psychologist Gary Wenk are studying the protective effects of tetrahydrocannabinol, commonly known as THC. They found that administering a THC-like synthetic drug to older rats performed better at a memory test than a control group of non-medicated elderly rodents.
In some of the rats, the drug apparently lowered inflammation in the hippocampus — the region of the brain responsible for short-term memory. It also seems to have stimulated the generation of new brain cells.
"When we're young, we reproduce neurons and our memory works fine," said co-author Yannick Marchalant, another Ohio State psychologist. "When we age, the process slows down, so we have a decrease in new cell formation in normal aging. You need those cells to come back and help form new memories, and we found that this THC-like agent can influence creation of those cells."
Wenk added two cautionary notes to his report. First, to be effective, any such treatment along these lines would have to take place before memory loss is obvious. Second, the researchers still have much work to do.
"We need to find exactly which receptors are most crucial" to the generation of new brain cells, he said. This discovery would "ideally lead to the development of drugs that specifically activate those receptors."
In the meantime, should aging baby boomers who are worried about old-age mental impairment light up a joint? Wenk was cautious in his answer, no doubt because marijuana is suspected to be harmful to health in other ways.
"Could people smoke marijuana to prevent Alzheimer's disease if the disease is in the family? We're not saying that, but it might actually work," he said. "What we are saying is it appears that a safe, legal substance the mimics those important properties of marijuana can work on receptors in the brain to prevent memory impairments in aging. So that's really hopeful."
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