Point prognostics: Bashkirs had higher risk of Alzheimer's disease
Several ethnic groups living in Russia turned out to be predisposed to the risk of Alzheimer's disease, geneticists reported after analyzing the genomes of more than 166 thousand people. Mutations in a number of genes indicate an increased risk of developing this disease. The probability of the disease is higher than among other ethnic groups, among Bashkirs, Mari, Chuvash, Yakuts and Buryats. Only about 25% of people in the world carry a gene at increased risk of developing Alzheimer's disease. About what preventive measures there are, see the Izvestia article.
Which people have a predisposition to Alzheimer's
Bashkirs occupy the first place in the number of people with a predisposition to a high risk of Alzheimer's disease, geneticists told Izvestia. The researchers studied mutations in the APOE gene, which plays an important role in fat metabolism and cholesterol transport in the body.
Alzheimer's disease is a neurodegenerative disease, one of the most common causes of dementia, said Ekaterina Demyanovskaya, an expert at the Hemotest laboratory and a neurologist. According to WHO, in 2021, 55 million people worldwide were diagnosed with dementia, in 60-70% of cases it was caused by Alzheimer's disease.
"In this disease, proteins gradually accumulate in the nerve cells of the brain, causing their damage and loss of cognitive functions," she said.
As Genotek specialists have pointed out, humans have several variants of this gene, each of which encodes different forms of the protein apolipoprotein E. The main mutation variants are E2, E3 and E4. For the analysis, scientists used 166 thousand genomes.
"The presence of the APOE E4 variation increases the risk of developing Alzheimer's disease and cardiovascular diseases and stroke," the experts emphasized.
The geneticists recalled that about 25% of people carry one copy of it, and 2-3% of the population carry two copies. According to them, the risk of Alzheimer's disease is three times higher in the former than in those who do not have it, and in carriers of two copies — up to 15 times.
"Bashkirs have the APOE E4 gene in almost 6% of cases. This gene variant is almost twice as rare among Mari and Chuvash people," the geneticists noted.
To a lesser extent, Yakuts, Buryats, Tatars and Ossetians are at risk of developing Alzheimer's disease, the experts added.
Mountain Jews and Armenians have the lowest risk of developing the disease — they have a variant of this gene found in only 0.45% of cases.
But the frequency of the APOE E4 gene in Bashkirs does not indicate that representatives of this people are more likely to suffer from Alzheimer's disease, said Mikhail Bolkov, a researcher at the Institute for the Study of Aging at the Russian State Scientific and Clinical Center of the Pirogov Russian National Research Medical University of the Russian Ministry of Health.
"People with a certain form of this protein have a higher risk of developing pathology," the expert explained. — But at the same time, numerous other factors continue to play a huge role, both other genetic and environmental and lifestyle factors. It's just a possibility. And if Bashkirs lead this rating, it does not mean that they are more likely to suffer from Alzheimer's disease. There is a risk of development, but there is no statistical data on how this actually happens.
The connection between genetics and Alzheimer's disease exists, confirmed by Ilya Kanivets, a geneticist at the European Medical Center.
"Recently, a relationship between certain genotypes and its development has been shown with a very high correlation," the expert explained. — In certain population groups, the frequency of genetic variants may vary for various reasons. If they analyzed 166 thousand genomes, then this is a large sample.
What are the causes of the disease
Carrying the APOE E4 gene really increases the risks of Alzheimer's disease, as well as cardiovascular diseases, especially in old age, a psychiatrist and an expert from the Dementia social project told Izvestia.net Maria Shtan.
"The data obtained is relevant and opens up new opportunities for personalized diagnosis and treatment of patients with cognitive disorders," she noted. — Carriage occurs in 12-13% of Russians.
There are also at least three other genes directly associated with early Alzheimer's disease — APP, PSEN1, PSEN2. According to her, they account for up to 93% of all hereditary cases.
Mutations in these genes most often lead to the development of Alzheimer's disease before the age of 60, said Alexander Reznik, a geneticist at the Hadassah Medical Moscow Clinic.
— In the case of other forms of dementia, for example, Pick's or Huntington's disease, "breakdowns" occur, for example, in the MAPT, GRN and HTT genes, — added Maria Shtan. — But more often, neurodegeneration is triggered not by genetics, but by "provocateurs": uncontrolled hypertension, diabetes, and brain injuries. And a mutation in the APOE gene is a risk factor, not a cause. Its carriers can avoid dementia by following prevention.
According to Alexander Reznik, effective and scientifically proven ways to prevent Alzheimer's disease include mental activity and consumption of green tea and coffee.
More than 400 genes have now been identified, mutations in which may somehow indicate the risk of Alzheimer's disease, Ekaterina Demyanovskaya added.
A lot of data has already been accumulated indicating the multifactorial nature of Alzheimer's disease, said Svetlana Ryazhskaya, a geneticist at the Genetico Medical and Genetic Center. According to her, in most cases, in the absence of a family history of cognitive disorders, doctors speak of an unspecified etiology of the disease — a combination of genetic factors predisposing to the development of the disease, vascular events, as well as infectious and toxic causes.
The genes of Alzheimer's disease were discovered in the 1990s by Russian geneticist Evgeny Rogaev together with Canadian colleagues, geneticist Svetlana Borinskaya reminded Izvestia.
— It's about the presenilin genes. Carriers of certain mutations in them develop early forms of Alzheimer's disease. Unlike the APOE gene, these are not risk genes, where the probability of developing a disease increases several times, but disease genes. If there is a mutation, there will be a disease. In such cases, they talk about a family form of the disease," she explained.
Also, according to her, there are other genes in which mutations lead to Alzheimer's disease. But they are quite rare. The prevalence of the APOE E4 gene is high in comparison with them, the expert added.
— The risk genotype is most often found in the northern peoples. There, its frequency reaches 15%. It occurs with approximately the same frequency among African hunter-gatherers. For example, Bushmen and groups close to them living south of the equator. But it's not risky for them," the geneticist said.
The risk of Alzheimer's disease depends not only on genes, but also on lifestyle, Svetlana Borinskaya emphasized.
— In most patients, no "risky" genes are found, their disease is largely related to life events. For example, concussion and head injuries," she explained.
The role of genetics in Alzheimer's disease has not been proven, Mikhail Bolkov said. At the same time, according to him, it is indisputable, for example, in the diagnosis of breast, ovarian or prostate cancer.
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