APOE Genotype Influences Postprandial Blood Pressure after High Fat Feeding in Older Adults

Acute cerebral blood flow response to heavy cream ingestion in older adults: A non-randomized pilot study

BackgroundHypertension and the APOE4 allele are known risk factors for Alzheimer's disease (AD) and E4 carriers show different blood pressure (BP) and cognitive responses to high fat feeding.ObjectiveWe investigated the influence of these factors on global cerebral blood flow (CBF) and four regions of interest (ROIs) (angular gyrus, hippocampus, posterior cingulate, temporal lobe) using arterial spin labeling (ASL) MRI in fasting state and after ingestion of heavy cream in older adults.Methods29 adults (age in years 66.8 ± 4.1) underwent baseline and 1, 2, 3-h ASL MRI after ingestion of 100 mL heavy cream. We used pCASL MRI with background suppression to measure CBF in ml/100 g/min. Statistical analyses included mixed-effects modeling and Pearson correlation to ascertain whether CBF changed over time and how variables influenced results.ResultsGlobal CBF decreased at 1-, 2-, and 3-h post-heavy cream, compared to time 0 (overall change 7.11%, p < 0.01); recapitulated in 3 of 4 ROIs. Mean arterial pressure emerged as a predictive variable for both baseline and post-heavy cream CBF (β = -0.25, 95% CI = -0.39, -0.10, p = 0.002). Individuals with higher BP demonstrated reduced CBF, particularly in posterior cingulate and temporal lobe (β = -5.50, 95% CI = -9.9, -1.09; β = -6.28, 95% CI = -12.35, -0.21, respectively, both p < 0.05). Examination of correlations with BP and change scores revealed that this relationship was driven largely by E4 carriers.ConclusionsCBF decreased after ingestion of heavy cream, globally and in regions known to be important in AD, and this finding was driven by E4 carriers with higher BP.

Effects of APOE2 and APOE4 on brain microstructure in older adults: modification by age, sex, and cognitive status

BACKGROUND

APOE4 is the strongest genetic risk factor for sporadic Alzheimer's disease (AD), whereas APOE2 confers protection. However, effects of APOE on neurodegeneration in cognitively intact individuals, and how these associations evolve with cognitive decline, are unclear. Furthermore, few studies have evaluated whether effects of APOE on neurodegenerative changes are modified by other AD key risk factors including age and sex.

METHODS

Participants included older adults (57% women; 77 ± 7 years) from the Rancho Bernardo Study of Health Aging and the University of California San Diego Alzheimer's Disease Research Center, including 192 cognitively normal (CN) individuals and 33 with mild cognitive impairment. Participants underwent diffusion MRI, and multicompartment restriction spectrum imaging (RSI) metrics were computed in white matter, gray matter, and subcortical regions of interest. Participants were classified as APOE4 carriers, APOE2 carriers, and APOE3 homozygotes. Analysis of covariance among CN (adjusting for age, sex, and scanner) assessed differences in brain microstructure by APOE, as well as interactions between APOE and sex. Analyses across all participants examined interactions between APOE4 and cognitive status. Linear regressions assessed APOE by age interactions.

RESULTS

Among CN, APOE4 carriers showed lower entorhinal cortex neurite density than non-carriers, whereas APOE2 carriers showed lower cingulum neurite density than non-carriers. Differences in entorhinal microstructure by APOE4 and in entorhinal and cingulum microstructure by APOE2 were present for women only. Age correlated with lower entorhinal restricted isotropic diffusion among APOE4 non-carriers, whereas age correlated with lower putamen restricted isotropic diffusion among APOE4 carriers. Differences in microstructure between cognitively normal and impaired participants were stronger for APOE4-carriers in medial temporal regions, thalamus, and global gray matter, but stronger for non-carriers in caudate.

CONCLUSIONS

The entorhinal cortex may be an early target of neurodegenerative changes associated with APOE4 in presymptomatic individuals, whereas APOE2 may support beneficial white matter and entorhinal microstructure, with potential sex differences that warrant further investigation. APOE modifies microstructural patterns associated with aging and cognitive impairment, which may advance the development of biomarkers to distinguish microstructural changes characteristic of normal brain aging, APOE-dependent pathways, and non-AD etiologies.