Slow-acting brain
toxin triggered by
eating bats, study findsIsle experts continue their brain
research among Guam nativesNerve diseases ravage millions
A Kauai-based research team hopes it can help find the cause of an incurable group of neurological diseases that affect millions of people.
Though the symptoms are different, Parkinson's, Lou Gehrig's and Alzheimer's disease are related.
They are the kind of debilitating diseases that ethnobotanist Paul Cox has studied since 1985, hoping to find cures or treatments through the use of plants or plant-based medicines.
In April, Cox and his team on Kauai made a breakthrough he felt was so important that he will take a 17-month sabbatical from his job as director of the National Tropical Botanical Garden to concentrate on the research.
A little more than a year ago, Cox and neurologist Dr. Oliver Sacks, of New York, proposed that the Chamorro people of Guam's practice of eating flying foxes, also known as fruit bats, may be directly linked to their high incidence of amyotrophic lateral sclerosis, or Lou Gehrig's disease, and the Parkinsonism-dementia complex, which includes symptoms of Alzheimer's and Parkinson's.
The complex of diseases, referred to as ALS-PDC by doctors and commonly called lytico-bodig in Guam, at its height was up to 100 times more likely to afflict Chamorros than the rest of the world's population.
Cox's team has been working for a year to show that the same toxic molecules in the seed of Guam's native cycad tree are concentrated in the flying foxes. The team believes it proved that in April.
Now the team will try to prove that humans consuming the flying foxes get a high enough dose of the nerve poison to trigger lytico-bodig, though the disease may not manifest for years. The concept is analogous to people getting mercury poisoning through eating contaminated fish, Cox said.
"Suggesting that a molecule in the diet causes a progressive neurological disease is fairly radical and has properly caused more than a few raised eyebrows, particularly since our suggestion is deeply rooted in ethnobotanical studies rather than neurolopathology," Cox said. "So the burden is on us to come up with the evidence for this. Extraordinary claims require extraordinary evidence."
Assisting Cox in the research are flying-fox expert Sandra Banack, of California State University at Fullerton, and plant chemistry specialist Susan Murch, of the University of Guelph, in Ontario, Canada.
Murch said: "I think in all human disease scenarios, the first step to finding a cure for a disease is to find the cause. Once you find out a cause, you have another piece in a puzzle that eventually could lead to a cure."
Since the 1950s, researchers have tested and rejected theories as to why Chamorros had such high rates of neuro-degenerative disease. Genetics, aluminum in the water, nutritional deficiencies and a virus have been ruled out, Cox said.
Another premise was that the Chamorro could be affected by eating tortillas made from cycad seed flour, since the plant was known to contain a neurotoxin. But in the 1980s it was determined that a person would have to eat humanly impossible quantities to get a significant dose, Cox said.
But a flying fox is known to eat more than twice its 1-pound weight in a single night of feeding, Cox said, and if the toxin is held in its body, the person eating it gets a much stronger dose.
"The hypothesis we're talking about now is that if a person is exposed to a toxin, it doesn't cause any immediate symptoms, but gets incorporated into the body's protein so that many years later chronic toxicity causes nerve cells to fail," said Dr. John Steele, a neurologist on Guam who is collaborating on the research.
Another link in the scientific chain, said Steele, is the recent discovery that laboratory monkeys given a single dose of a neurotoxin 20 years ago only recently developed Parkinson's-like symptoms.
"This is so important a hypothesis and new thought, so 'thinking outside the box,' that if it's proven, it wins a Nobel Prize for Paul," Steele said.
There is an urgency to the work. The endangered flying foxes of Guam have dwindled to a few hundred individuals, and it is illegal to kill them. And fewer Chamorros are being diagnosed with lytico-bodig.
"I'm sure in 10 years there will be no more of this disease on the island," Steele said. "No one born after 1951 has proven to have ALS. ... Many of the patients are in their 70s and 80s."
Once that population of Chamorros dies, there will be no way to see if the theory is correct.
Steele hopes to get permission from a few elderly patients to take samples from their body tissues after death. Cox's lab could test them to see if they contain the toxic molecules that may have originated in a cycad seed decades before.
Banack said, "If we can do something that could help sick people or prevent them from getting it in the future ... that would be the most rewarding thing we can do."
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Nerve diseases
ravage millions
In the United States, 4.5 million people are affected by the nerve-degenerating Alzheimer's, Parkinson's and Lou Gehrig's diseases. The diseases are caused by degeneration of neurons in different parts of the brain, which results in their differing symptoms. All are progressive diseases that get worse over time. None has a known cause or cure. Most of those afflicted are older than 60.
Alzheimer's Disease
More than 4 million Americans have Alzheimer's disease, which seriously affects the parts of the brain that control thought, memory and language. Former President Ronald Reagan is perhaps the best-known American with Alzheimer's.
Parkinson's Disease
About 500,000 Americans have Parkinson's disease, which is characterized by shaking limbs and a decreasing ability to control muscles. A patient's tremor often begins on one side of the body, frequently in one hand. Other common symptoms include slow movement, rigid limbs, a shuffling gait and a stooped posture. Actor Michael J. Fox and the pope have the disease.
Lou Gehrig's Disease
Lou Gehrig's disease, also known as amyotrophic lateral sclerosis, causes a person to lose the ability to move his or her arms, legs and body and, finally, to breathe. Most patients die within five years of diagnosis, although a minority live for 10 or more years. About 20,000 Americans are living with it. Baseball player Lou Gehrig, who shocked the public with his swift deterioration from top athlete to invalid, remains its most well-known victim.
Source: National Institutes of Health Web site, health.nih.gov