title: Biomagnification of cyanobacterial neurotoxins and neurodegenerative disease among the Chamorro people of Guam.
abstract: We here report biomagnification (the increasing accumulation of bioactive, often deleterious molecules through higher trophic levels of a food chain) of the neurotoxic nonprotein amino acid beta-methylamino-l-alanine (BMAA) in the Guam ecosystem. Free-living cyanobacteria produce 0.3 microg/g BMAA, but produce 2-37 microg/g as symbionts in the coralloid roots of cycad trees. BMAA is concentrated in the developing reproductive tissues of the cycad Cycas micronesica, averaging 9 microg/g in the fleshy seed sarcotesta and a mean of 1,161 microg/g BMAA in the outermost seed layer. Flying foxes (Pteropus mariannus), which forage on the seeds, accumulate a mean of 3,556 microg/g BMAA. Flying foxes are a prized food item of the indigenous Chamorro people who boil them in coconut cream and eat them whole. Chamorros who die of amyotrophic lateral sclerosis/parkinsonism-dementia complex (AL-SPDC), a neurodegenerative disease with symptoms similar to amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease, have an average of 6.6 microg/g BMAA in their brain tissues. The biomagnification of BMAA through the Guam ecosystem fits a classic triangle of increasing concentrations of toxic compounds up the food chain. This may explain why the incidence of ALS-PDC among the Chamorro was 50-100 times the incidence of amyotrophic lateral sclerosis elsewhere. Biomagnification of cyanobacterial BMAA may not be unique to Guam; our discovery of BMAA in the brain tissue from Alzheimer's patients from Canada suggests alternative ecological pathways for the bioaccumulation of BMAA in aquatic or terrestrial ecosystems.
authors: Institute for Ethnobotany, National Tropical Botanical Garden, Kalaheo, HI 96741, USA. paulcox@ntbg.org
authors: Paul Alan
authors: PA
authors: Cox
authors: Sandra Anne
authors: SA
authors: Banack
authors: Susan J
authors: SJ
authors: Murch
mesh_terms: D000599:Amino Acids, Diamino / Q000378:metabolism*; D000690:Amyotrophic Lateral Sclerosis / Q000473:pathology; D000818:Animals; D001921:Brain / Q000378:metabolism; D002685:Chiroptera; D000458:Cyanobacteria / Q000378:metabolism*; D000087522:Cyanobacteria Toxins; D029784:Cycas / Q000378:metabolism; D003704:Dementia / Q000473:pathology; D017753:Ecosystem; D020387:Food Chain; D006141:Guam; D006801:Humans; D019636:Neurodegenerative Diseases / Q000378:metabolism*; D009498:Neurotoxins / Q000378:metabolism*; D010300:Parkinson Disease / Q000473:pathology; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D010945:Plants, Edible / Q000382:microbiology
chemical_list: D000599:Amino Acids, Diamino; D000087522:Cyanobacteria Toxins; D009498:Neurotoxins; C001824:beta-N-methylamino-L-alanine