Increased Risk of Alzheimer's in APOE4 Carriers

Article: The Eyes Offer a Window into Alzheimer’s Disease
Source: University of California, San Francisco, via ScienceDaily  and Technology Networks
Published: May 13, 2021
Article: Alzheimer’s Could Lie in the Eyes of the Holder
Source: Genetic Engineering & Biotechnology News
Published: May 14, 2021

Comparison of OCTA scans in a carrier versus noncarrier for APOE4

Scientists at UCSF conducted a study using optical coherence tomography angiography (OCTA) to detect early signs of Alzheimer's disease in the brain, as well as explored how the APOE4 gene contributes to the disease. The angiography function of OCT visualizes the blood flow in retinal vasculature. Although it is still unclear as to how the APOE4 gene (encoding apolipoprotein 4) increases risk for neurodegenerative diseases, prior research in mice indicates that it affects blood vessels, including the capillaries in the brain and, by extension, the retina. Since capillaries deliver nutrients and oxygen, carry away waste, and form the blood-brain barrier, the researchers wanted to explore how damage to blood vessels could contribute to protein buildup and cognitive decline seen in diseases such as Alzheimer's. OCTA scans showed reduced capillary density in APOE4 carriers, which increased with participant age. Furthermore, measurement of retinal blood flow via OCTA correlated with measurement of blood flow in the brain via MRI; people with higher retinal capillary density also had greater blood flow in the brain. There was no correlation, however, between retinal capillary density and beta-amyloid plaques as measured by PET scan, suggesting that capillary abnormalities are not likely (directly) driven by amyloid pathology. As the lead researcher states, “This is the first time that we have demonstrated in living, asymptomatic humans that the smallest blood vessels are affected in APOE4 gene carriers,” which suggests that the increased risk of neurodegeneration in APOE4 carriers may be through its effect on blood vessels.

My rating of this study: ⭐⭐⭐

Elahi FM, Ashimatey SB, Bennett DJ. "Retinal imaging demonstrates reduced capillary density in clinically unimpaired APOE ε4 gene carriers." Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring.  13(1). 11 May 2021. https://doi.org/10.1002/dad2.12181