The Cyanotoxin and Non-protein Amino Acid β-Methylamino-L-Alanine (L-BMAA) in the Food Chain: Incorporation into Proteins and Its Impact on Human Health.

The size and frequency of cyanobacterial blooms are increasing concomitantly with rising global temperatures and increased eutrophication, and this has implications for human health. Cyanotoxins, including L-BMAA, have been implicated in triggering neurodegenerative diseases such as ALS/PDC and Alzheimer's disease. L-BMAA is a water-soluble non-protein amino acid that can bioaccumulate up the food chain, in a free- and protein-bound form. While some data exists on the degree of environmental enrichment of L-BMAA in water bodies, cyanobacteria-derived supplements, fruit bats, and seafood, virtually nothing is known about the presence of L-BMAA in other foodstuffs. It has now been shown several times in laboratory settings that plants can absorb L-BMAA into their leaves and stems, but data from wild-grown plants is nascent. One of the mechanisms implicated in L-BMAA bioaccumulation is misincorporation into proteins in the place of the canonical amino acid L-serine. We first identified this as a mechanism of action of L-BMAA in 2013, and since then, several groups have replicated these findings, but others have not. Here, we discuss in detail the experimental approaches, why they may have produced negative findings and propose several ways forward for developing consistency within the field. We emphasize the need to standardize cell culture methods, using L-serine-free medium to study misincorporation of BMAA, and urge accurate reporting of the components present in cell culture media.