Credit: Thomas Perkins

Two separate groups of researchers are now pursuing edible options for the treatment or prevention of Alzheimer's disease. One study carried out by HyunSoon Kim (Korea Research Institute of Bioscience and Biotechnology) and colleagues showed that tomatoes may serve as effective carriers for an oral vaccine against β-amyloid in mice. Accumulation of β-amyloid protein in the brain leads to neuronal death, which is thought to underlie the neurodegeneration characteristic of Alzheimer's disease. The other group, led by Richard Wurtman at Massachusetts Institute of Technology (Cambridge, MA), found that dietary supplements of docosahexaenoic acid (DHA), uridine and choline improved learning and memory in gerbils.

Kim's group used bacteria-mediated transformation to generate tomato plants that expressed human β-amyloid protein. They then made a soluble extract and administered it orally to mice once a week for 3 weeks, with a booster 7 weeks after the initial administration. The mice had a strong immune response to the booster and produced antibodies to the foreign human β-amyloid protein (Biotechnol. Lett. doi:10.1007/s10529-008-9759-5; published online 5 July 2008).

Tomatoes were chosen for several reasons. β-amyloid is toxic to animal cells and is difficult to produce using E. coli or yeast cells, which are more commonly used in such applications. In addition, tomatoes can be consumed raw, which is an advantage because heat treatment may compromise the immunogenicity of the β-amyloid antigen. One disadvantage of the tomato-based system is that tomatoes contain relatively small amounts of native protein (0.7%) and can express even less foreign protein. Kim's group is currently investigating the possibility of increasing the expression level of foreign proteins in the tomatoes in order to increase the vaccine's strength. It is not yet known how or whether the vaccine will affect existing plaques of β-amyloid in brain tissue.

Wurtman's group used a different approach, targeting restoration of the synapses, which deteriorate in Alzheimer's disease. They had previously shown that when administered to gerbils via dietary supplements, the combination of DHA, choline and uridine resulted in increases in brain phosphatides and certain synaptic proteins. All three compounds are normally found in the bloodstream and are precursors to the fatty molecules that compose cell membranes. The new study found that performance in tests of cognitive function improved in gerbils given the dietary supplements (FASEB J. doi:10.1096/fj.08-112425; published online 7 July 2008), linking increases in synaptic membrane content with improvements in learning and memory.

The two ideas together put a whole new spin on the glass of tomato juice and vitamin pill you might have had with your breakfast!