Investigating the Role of the Exposome on Neuropathology and Biochemical Phenotypes in Alzheimer’s Disease
Gabriela Garofalo1, Joseph S. Reddy1, Michael Heckman1, Stephanie R. Oatman1, Xue Wang1, Geovanna G. Yepez Sisalema1, Lindsey Kuchenbecker1, Thuy T. Nguyen1, Melissa E. Murray1, Dennis W. Dickson1, Takahisa Kanekiyo1, Minerva M. Carrasquillo1, Mariet A. Younkin1, Nilufer Taner1
1Mayo Clinic Jacksonville
Objective:
To assess the effects of exposome components in the severity of neuropathology and biochemical phenotypes of AD.

Background:

Individual environmental exposures, the exposome, can play an influential role in the development and progression of neurodegenerative diseases such as AD. We hypothesize that potentially modifiable risk factors of AD such as diabetes, hypertension, smoking, and alcohol consumption, in addition to the underexplored area deprivation index (ADI), could play a considerable role in severity of neuropathology and biochemical phenotypes of AD.

Design/Methods:

We evaluated 478 neuropathologically characterized AD donors, from the Mayo Clinic Brain Bank. 469 samples had available biochemical measures (APOE, Aβ40, Aβ42, tau, and phosphor-tau (Thr231)), collected across three isolated fractions (soluble (TBS), membrane-bound (TX), and insoluble (FA)) of the superior temporal gyrus. Exposome variables were extracted from the available records. Associations of ADI, diabetes, hypertension, smoking and alcohol with biochemical and neuropathology phenotypes were examined using linear regression, binary logistic regression and ordinal logistic regression models as appropriate given the nature of the outcome variable; all models were adjusted for age at death and sex.

Results:
Higher ADI levels representing neighborhoods with increased deprivation, were nominally associated with soluble levels of APOE (β=0.006, p=0.01), cerebral infarcts (β=0.02, p=0.04), and we identified a trend for vascular brain injury (β=0.02, p=0.06). Alcohol was associated with lower levels of membrane bound APOE (β=-0.23, p=0.04).  We also observed trends for increased insoluble tau (β=0.21, p=0.06) in patients with hypertension and higher membrane bound and lower insoluble APOE (β=0.27, p=0.06); (β=-0.28, p=0.06) in patients with diabetes.
Conclusions:

Different components of the exposome impact levels of core AD proteins. Additional analyses in expanded cohorts to further explore the associations with neuropathology are ongoing. We expect that understanding how exposome impacts specific aspects of neurodegenerative diseases will provide key insights into underlying, potentially modifiable, mechanisms of disease.

10.1212/WNL.0000000000216982
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