Alzheimer's disease is the most common type of dementia in the world. Due to the fact that it makes up 50-70% of all dementia cases, it is a much-studied illness but there are still many unknowns about treatment, causes and prevention.
Alzheimer's is a neurodegenerative disease which causes damage and death to neurons and their connections, leading to a progressive deterioration of the body's biological functions. There are two proteins involved: neurofibrillary tangles and beta-amyloid protein plaques, these proteins are deposited inside the neuron until they are damaged and die hence causing Alzheimer’s.
There are also genetic reasons (several genes have been identified, such as PSEN1 and PSEN2) that cause Alzheimer's. In these cases, we speak of familial or hereditary Alzheimer's. Most of these inherited genetic mutations show the first symptoms before the age of 60, and only explain 1 to 5 % of all cases.
There are many lines of research working to elucidate more clearly the causes of Alzheimer's. Specifically investigating how these harmful proteins develop and how they are deposited in neurons.
Aluminium and Alzheimer's
Recent research had already measured a high aluminium content in the brain tissue of patients with familial Alzheimer's disease. Now, a new study published in the Journal of Alzheimer's Disease has sought to investigate the role of this mineral in the production or deposit of these harmful proteins, which cause Alzheimer's.
The hypothesis that the study wanted to test was that human exposure to aluminium is related to the aetiology (the study of the cause) of Alzheimer's disease.
An important point: this study was carried out only on patients with familial or hereditary Alzheimer's (that is, those cases in which there is a gene involved). Therefore, we cannot say that the results are valid in cases of sporadic Alzheimer's, whose causes are unknown.
The researchers obtained brain tissue from a cohort of donors with hereditary Alzheimer's disease. They then measured the aluminium content of these tissues and compared the data with healthy brain tissue.
Deposition of aluminium in a senile plaque on the temporal cortex of a donor with hereditary Alzheimer's Disease.
The scientists did indeed find "significantly higher" levels, as cited in the study, of aluminium in the Alzheimer's brains than in the control tissues of donors without neurological impairment.
How is aluminium detected in a brain? The researchers used aluminium-specific fluorescence microscopy along with other images that, in turn, revealed the presence of beta-amyloid proteins.
"We have been able to demonstrate a very high degree of co-localization of these two risk factors (aluminium and beta-amyloid proteins) in brain tissue in familial or hereditary Alzheimer's disease," the researchers report in the publication.
Remember: Familial Alzheimer's represents only 1 to 5 % of the cases of this type of dementia.
Aluminium and beta-amyloid proteins were located together in the senile plaques of the neurons. Aluminium was also found separately from beta-amyloid proteins in intracellular compartments.
Research has identified a possibly unique association so far between the high aluminium content in the brain and beta-amyloid proteins, which allows us to postulate that the genetic predispositions that define familial Alzheimer's disease underlie this relationship.
This study brings us closer to a better approximation of the causes of hereditary Alzheimer's, which could allow us to work on lines of prevention and treatment.
The relationship of aluminium observed in this research, as we mentioned, is valid for cases of hereditary Alzheimer's, which occurs early (symptoms before the age of 60 or 65) and with two or more family histories of this disease.
There may also be genes involved in the origin of late or sporadic Alzheimer's, but its clear cause remains an unsolved puzzle.
Reference: Mold, Matthew. Aluminium and Amyloid-β in Familial Alzheimer's Disease. Journal of Alzheimer's Disease, vol. Pre-press, no. Pre-press, pp. 1-9, 2019. Doi: 10.3233/JAD-191140