Investigators have found a possible link between an ALS-like disease and a toxic substance produced by cyanobacteria, microscopic organisms once called blue-green algae.
The research, funded by The ALS Association and published in the Proceedings of the National Academy of Sciences, raises the question of whether environmental neurotoxins in the diet may play a role in the development of some forms of neurodegenerative diseases.
In the study, the investigators found that the diet of the indigenous Chamorro people may account for the high incidence of a neurological disease called amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS-PDC), which has symptoms of ALS, Parkinson's, or Alzheimer's Disease. In the mid 20th century, the disease affected about 400 per 100,000 Chamorro, but now the rate of ALS-PDC is down about 22 per 100,000.
"This research adds to the inventory of suspicion that the environment may play a role in the development of ALS/PDC," said Dr. Lucie Bruijn, science director and vice president of The ALS Association. "This study provides interesting data that should be further investigated."
In Guam, investigators found that a high incidence of ALS-PDC in the native Chamorro people may be linked to their feasting on flying fox bats. The bats forage on seeds from cycad trees, which contain cyanobacteria in their roots that produce the neurotoxin b-methylamino-L-alanine (BMAA). BMMA is an excitotoxin, causing a persistent excitation of neurons that ultimately exhausts the cells until they can no longer function.
Ethnobotanist Paul Alan Cox, Ph.D., ecologist Sandra Banack, Ph.D., and biochemist Susan Murch, Ph.D. reported that the neurotoxin is biomagnified 100,000 times in concentration as it travels up the Guam food chain to flying foxes. Chamorro people who died of ALS-PDC have high levels of BMAA in their brain, while healthy brain tissue does not have the toxin, according to Cox's findings.
In examining the biomagnification process in the food chain in other cultures, the research also found similar concentrations of BMAA in the brain tissues of two patients from Canada who died from Alzheimer's disease. "We cannot say much from a finding of BMAA in only two AD patients," said Dr. Cox, "so further studies are needed to determine if there may be an association between BMAA and AD or ALS and other neurodegenerative diseases outside of Guam. At this point, we simply don't know."
"This is certainly intriguing," remarks Dr. Bruijn. "Further studies in a larger population of ALS and Alzheimer's disease patients are needed to confirm these findings."