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Dementia Gene May Guard Against Decline Associated With Parasitic Disease

Summary: A new study reports carriers of APOE4 could have reduced risk of cognitive decline associated with parasitic infection.

Source: FASEB.

New research in The FASEB Journal suggests that a gene associated with high risk for Alzheimer’s disease and cardiovascular disease may actually have conferred an evolutionary advantage for humans at high risk for parasitic infections.

New research published online in The FASEB Journal, suggests that carriers of the Apolipoprotein E4 allele, which is the single strongest genetic predictor of Alzheimer’s disease and is associated with cognitive decline and cardiovascular disease, may have a reduced risk of cognitive decline associated with parasitic diseases. This protective effect may help explain why this “disease” gene has persisted over the millennia, as well as offering insights into preventing and treating the cognitive problems caused by human parasites.

“While being an E4 carrier is the strongest risk factor to date of Alzheimer’s dementia and cognitive decline in industrial populations, it is associated with greater cognitive performance in individuals facing a high parasite and pathogen load, suggesting advantages to the E4 allele under certain environmental conditions,” said Benjamin C. Trumble, Ph.D., a researcher involved in the work at the School of Human Evolution and Social Change and the Center for Evolution and Medicine at Arizona State University in Tempe, Arizona. “The current mismatch between sedentary postindustrial lifestyles and active parasite-rich lifeways experienced throughout most of human history may be critical for understanding genetic risk for cognitive aging.”

Trumble and colleagues examined cognitive performance and parasite exposure data from a remote population of forager-horticulturalists in the Bolivian Amazon, called the Tsimane. The Tsimane experience high parasite loads, making them a suitable population for study for the role of the E4 allele in this circumstance. The researchers undertook a genetic analysis, measured immune markers of parasitic infection, and conducted cognitive tests on 372 Tsimane men and women aged 6 to 88 years. They found that for the Tsimane who did not carry the E4 allele, a larger parasite burden resulted in poorer cognitive performance. Those who carried the E4 allele, however, maintained cognitive performance even with very high parasite burdens.

The researchers undertook a genetic analysis, measured immune markers of parasitic infection, and conducted cognitive tests on 372 Tsimane men and women aged 6 to 88 years. They found that for the Tsimane who did not carry the E4 allele, a larger parasite burden resulted in poorer cognitive performance. Those who carried the E4 allele, however, maintained cognitive performance even with very high parasite burdens. NeuroscienceNews.com image is for illustrative purposes only.

“This is a wonderful, unanticipated case of a balanced polymorphism affecting a trait, dementia, with predictably major selection consequences” said Thoru Pederson, Ph.D., Editor-in-Chief of The FASEB Journal. “Evolution may not work in quite so mysterious ways as delightfully entertaining ways.”

About this neuroscience research article

Source: Cody Mooneyhan – FASEB
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden” by Benjamin C. Trumble, Jonathan Stieglitz, Aaron D. Blackwell, Hooman Allayee, Bret Beheim, Caleb E. Finch, Michael Gurven and Hillard Kaplan in FASEB Journal. Published online January 2017 doi:10.1096/fj.201601084R

Cite This NeuroscienceNews.com Article
FASEB “Dementia Gene May Guard Against Decline Associated With Parasitic Disease.” NeuroscienceNews. NeuroscienceNews, 10 January 2017.
<http://neurosciencenews.com/apoe4-parasitic-disease-5910/>.
FASEB (2017, January 10). Dementia Gene May Guard Against Decline Associated With Parasitic Disease. NeuroscienceNew. Retrieved January 10, 2017 from http://neurosciencenews.com/apoe4-parasitic-disease-5910/
FASEB “Dementia Gene May Guard Against Decline Associated With Parasitic Disease.” http://neurosciencenews.com/apoe4-parasitic-disease-5910/ (accessed January 10, 2017).

Abstract

Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden

The apolipoprotein E4 (E4) allele is present worldwide, despite its associations with higher risk of cardiovascular morbidity, accelerated cognitive decline during aging, and Alzheimer’s disease (AD). The E4 allele is especially prevalent in some tropical regions with a high parasite burden. Equatorial populations also face a potential dual burden of high E4 prevalence combined with parasitic infections that can also reduce cognitive performance. We examined the interactions of E4, parasite burden, and cognitive performance in a traditional, nonindustrialized population of Amazonian forager-horticulturalists (N = 372) to test whether E4 protects against cognitive decline in environments with a heavy pathogen burden. Contrary to observations in industrial populations, older adult E4 carriers with high parasite burdens either maintained or showed slight improvements in cognitive performance, whereas non-E4 carriers with a high parasite burden showed reduced cognitive performance. Being an E4 carrier is the strongest risk factor to date of AD and cognitive decline in industrial populations; it is associated with greater cognitive performance in individuals facing a high parasite and pathogen load, suggesting advantages to the E4 allele under certain environmental conditions. The current mismatch between postindustrial hygienic lifestyles and active parasite-rich environs may be critical for understanding genetic risk for cognitive aging

“Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden” by Benjamin C. Trumble, Jonathan Stieglitz, Aaron D. Blackwell, Hooman Allayee, Bret Beheim, Caleb E. Finch, Michael Gurven and Hillard Kaplan in FASEB Journal. Published online January 2017 doi:10.1096/fj.201601084R

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