(ORDO NEWS) — It turned out that the reason that some areas of the brain are more destroyed than others in Alzheimer’s disease lies in the APOE gene.
It is most strongly expressed in the temporal lobes of the brain, which is why they are the first to be damaged in this disease, and memory impairment becomes the earliest symptom.
However, the study may also help explain the rare symptoms seen in atypical Alzheimer’s disease.
Scientists from the Washington University School of Medicine in St. Louis (USA) have found out why certain areas of the brain are especially vulnerable to Alzheimer’s disease.
It turned out that the APOE gene – one of the genetic risk factors for this disease – is most active in the most damaged areas of the brain.
The results of the study, which is published in the journal Science Translational Medicine, also explain why the symptoms of Alzheimer’s disease sometimes vary greatly from patient to patient.
Memory loss is often the first sign of Alzheimer’s disease and is usually followed by confusion and cognitive impairment. These symptoms reflect a typical pattern of progressive brain tissue damage.
Toxic accumulations of proteins first concentrate in the temporal lobes – the area responsible for memory – and then spread to those parts of the brain that are important for thinking and planning.
The main culprit in Alzheimer’s disease is the beta-amyloid protein, which forms amyloid plaques in brain tissue.
Later, the formation of other accumulations of abnormal proteins begins – neurofibrillary tangles of tau protein. Shortly thereafter, the tissues in the affected areas die off.
There are also some rare, atypical forms of Alzheimer’s disease that cause problems with speech and vision first, rather than memory.
Patients with atypical Alzheimer’s disease are often excluded from studies because it is easier to study a group with the same set of symptoms.
However, this heterogeneity suggests that scientists still do not fully understand how and why Alzheimer’s develops.
The authors of the new work analyzed data from 350 people who volunteered to participate in memory and aging studies.
They underwent brain scans so that scientists could determine the number and location of amyloid plaques and tau tangles in the brain.
The researchers compared patterns of protein accumulation and tissue damage in volunteers with expression patterns of the APOE gene and other genes associated with Alzheimer’s disease.
It turned out that high expression of the APOE gene is associated with increased accumulation of tau tangles and tissue damage. Other genes associated with Alzheimer’s disease showed similar patterns.
All of them were expressed mainly in the temporal lobes.
So there is something fundamentally different about these areas that makes them vulnerable to brain damage. And this feature, according to scientists, probably depends on human genetics.
All people have the APOE gene, but those with one of its variants have a 12 times higher risk of developing Alzheimer’s disease than the average.
Now the researchers plan to study patients with atypical Alzheimer’s disease and see which parts of the brain they have increased expression of APOE and which variants of this gene they carry.
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