A gene linked to Alzheimer’s may confer surprising benefits on fertility

In European populations, the apolipoprotein-ε4 (APOE-ε4) allele is associated with an increased risk of developing Alzheimer’s disease or cardiovascular disease. However, the allele of this ancestral gene is present in 5 to 45% of the world’s population. Why haven’t an allele that has a negative effect on an individual’s lifespan as it ages has already been eliminated by natural selection? It is an emerging puzzle that an interdisciplinary team has attempted to solve.

Special Fertility of the Tsimane Indigenous Peoples

The authors of the study published science progress Worked with a population with “natural” fertility: the indigenous Tsimane people of the Bolivian Amazon. Its hunter-gatherer lifestyle is closer to that of pre-Industrial Revolution humans than to modern Westerners, which provides insight into health and aging without modern influences.

This approach from the perspective of evolutionary anthropology is detailed in the study “”. Apolipoprotein-ε4 is associated with higher fertility in populations with natural fertility. “. The researchers collected data from 795 women aged 13 to 90 of the Simane people, 20% of whom are carriers of apoE-ε4. Anthropologist Benjamin Trumbull said: We found in this population that if women had the APOE-ε4 allele and had a shorter birth interval, they started to reproduce about a year earlier. These two factors combined allow them to have about half as many extra children if they have one copy of the allele or two extra children if they have two copies. ,

The advantage of this allele on fertility—early or in the middle of life—may explain why it is still transmitted to offspring today. , Genes associated with diseases that occur after reproductive age are in the “shadow of selection”. Several arguments have been made regarding the APOE-ε4 allele that it may be an example of shadow selection, that someone develops Alzheimer’s disease only after having all of their children. The professor specified.

Gene expression is controlled by lifestyle

However, the negative effect of this allele on Alzheimer’s is observed mainly in Western countries. According to research conducted last year, the Simaane have one of the lowest rates of dementia in the world, despite the 20% prevalence of the APOE-ε4 allele in their population. Among 623 adults over the age of 60, the prevalence of Alzheimer’s disease in Simane was approximately 1.2%, compared to 8–11% in the United States.

This means that gene expression depends on environment and lifestyle. , Our results add to a growing body of literature suggesting the need to study populations living in ancestrally relevant environments, in order to assess whether sedentary urban environments were harmed by selection in the evolutionary history of the human race. How alleles can be maintained. ”, the researchers concluded.