Having this gene mutation is like dealing with a game of chance. Scientists found that this particular allele or gene mutation can bring negative impact in this one environment but may bring positive one to this other environment.
Researchers at Arizona State University examined the apolipoprotein E (ApoE) gene and how they function and affect people living in a different environment conditions that humans have lived through our entire existence than in the urban industrialized conditions where ApoE has mostly been examined.
Tsimane family fishing in the Amazon in Bolivia
All ApoE proteins help facilitates cholesterol metabolism, and transportation of fatty acids to the brain. But in industrialized societies, ApoE4 variant carriers also face up to a four-fold higher risk for Alzheimer's disease and neurodegenerative conditions. That also includes cardiovascular diseases.
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The researchers pointed to the indigenous, people of Amazon in a subset group known as Tsimane. They are also specifically chosen for they are known to have high levels of inflammation and infection.
The health conditions of Tsimane would lead us to believe that they should fare far worse than those in industrialized societies on their mental and cognitive decline considering both genetic and environmental factors.
It didn't turn out to be that way for the Tsimane people. The Tsimane Health and Life History Project discovered the exact opposite.
The Tsimane who both carried ApoE4 and had high levels of parasitic infection showed steadier or even improved cognitive function in the examition compared to non-carriers with a similar level of parasitic exposure.
Such surprising turnout indicated that the allele helped maintain cognitive function even when one is exposed to environmental hazards.
But since Tsimane who carried ApoE4 but had lower levels of infection have the same cognitive decline with those in the industrialized group, this is also suggested that somehow the high rate of infection when matched with the allele provides a positive result.
"It seems that some of the very genetic mutations that help us succeed in more hazardous time periods and environments may actually become mismatched in our relatively safe and sterile post-industrial lifestyles," explained Ben Trumble, an assistant professor at ASU's School of Human Evolution and Social Change.
The researchers explained that this study can provide an insight on the persistence of bad genes and the mismatched environmental factors may shed light to genes' evolution.
The study is published
in The FASEB Journal.
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