UK researcher Allan Butterfield, based at the University of Kentucky in the US, studied amyloid beta peptide, a compound known to contribute to the senile plaques seen in the brains of Alzheimer's patients and thought by many to be responsible for the damage.
Writing in the October issue of the Journal of Alzheimer's Disease (vol 6, issue 5, pp515-25), Butterfield reports that in the animal form of the peptide, the introduction of the antioxidant vitamin E slowed the destruction of brain cells.
The research also demonstrates that both the amyloid beta peptide in the animal model and the same compound in humans both cause loss of connections between neurons and decreased cell viability as well as other damage associated with Alzheimer's.
"Beta(1-42) Rat [the animal form] was found to cause a significant increase in both protein oxidation and lipid peroxidation, similar to Abeta(1-42), both of which were inhibited by the lipid-soluble, chain breaking antioxidant vitamin E, suggesting that reactive oxygen species play a role in the Abeta-mediated toxicity," write the researchers.
Previous studies have shown that antioxidant vitamins may protect the brain against damage caused by free radicals and other reactive oxygen species produced during basic cellular metabolism. Neurons are especially sensitive to damage caused by free radicals, which is believed to be partially responsible for the development of Alzheimer's disease.
A study by John Hopkins researchers earlier this year found that people who took supplements of vitamin E in combination with vitamin C were less likely to develop the disease, however there was no evidence of benefit from multivitamins, or the vitamin alone.
There are nearly 18 million people with dementia in the world and the most common cause of this dementia is Alzheimer's disease. By 2025 this figure will rise to 34 million, with 71 per cent of these likely to live in developing countries.
The new study also proposes new mechanisms of action of the human amyloid beta peptide, as it identifies methionine in the peptide as a key contributor to Alzheimer's disease. A previous theory held that it was the copper binding sites in the human peptide that contributed to Alzheimer's.
The animal form of the peptide, which does not have the copper binding sites, still causes damage. Butterfield says this indicates the damage to neurons caused by the human peptide in an Alzheimer's disease patient is related to the peptide's methionine residue.