CSF APOE4 protein levels track tau pathology better than HDL measures in Alzheimer’s

Apolipoprotein E ε4 (APOE4) remains the strongest genetic risk factor for late-onset Alzheimer’s disease, but researchers have long debated whether its harmful effects stem from the lipidation state of HDL particles or from elevated APOE4 protein levels within the central nervous system. A new study using data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) now points firmly toward the latter, reporting that cerebrospinal fluid APOE4 protein burden, rather than HDL particle concentrations, is what aligns most closely with tau pathology and memory decline.

The research team, led by Hussein N. Yassine and colleagues, analyzed CSF and plasma samples from 144 participants carrying APOE ε3/ε3, ε3/ε4, or ε4/ε4 genotypes. Participants were grouped by cognitive state and by memory progression over four years, with memory loss defined as at least a 10 percent decline on the Rey Auditory Verbal Learning Test (RAVLT) delayed recall between baseline and 48-month follow-up. The investigators measured small and large HDL particle concentrations, total APOE levels, and isoform-specific APOE3 and APOE4 protein levels in both CSF and plasma.

Cross-sectional associations with the core Alzheimer’s biomarkers Aβ1-42, total tau, and p-tau181 were evaluated using covariate-adjusted linear regression, while longitudinal trajectories were examined with linear mixed-effects models over six years. The results showed that CSF small and large HDL levels were higher in cognitively normal individuals and in non-progressors, and that APOE4 carriers exhibited reduced CSF small HDL relative to ε3 homozygotes.

The pivotal finding, however, concerned APOE4 itself. Higher CSF APOE4 protein levels were associated with elevated tau and p-tau181 independently of small or large HDL particle concentrations. In contrast, plasma APOE measures showed minimal and often opposing associations with CSF biomarkers, underscoring that peripheral APOE readings may not reflect what is happening in the brain.

Longitudinally, higher baseline CSF APOE4 proportion relative to APOE3 was associated with greater memory decline over six years, but it did not predict biomarker change. The authors conclude that these findings support a CNS-compartment model in which APOE4 protein burden aligns more closely with tau pathology and cognitive decline than peripheral APOE or HDL particle measures in Alzheimer’s disease.

Subject of Research: The relationship between CSF APOE4 protein burden, HDL particle lipidation, tau pathology and cognitive decline in Alzheimer's disease

Article Title: Beyond lipidation: CSF APOE4 protein burden, not HDL subclass, drives tau associations in APOE4 Alzheimer’s disease

Article References: Tsokolas, Z. E., Asante, I., Tsiknia, A. A., Barbosa-Carvajal, J. P., Burka, L., Sagare, A., Cardona-Gómez, G. P., Mack, W. J., Braskie, M. N., Nedelkov, D., Krauss, R. M., Yassine, H. N., & for the Alzheimer’s Disease Neuroimaging Initiative (2026). Beyond lipidation: CSF APOE4 protein burden, not HDL subclass, drives tau associations in APOE4 Alzheimer’s disease. Alzheimer's Research & Therapy. https://doi.org/10.1186/s13195-026-02191-5

Image Credits: AI Generated

DOI: 10.1186/s13195-026-02191-5

Keywords: APOE4, Alzheimer's disease, cerebrospinal fluid, HDL particles, tau, p-tau181, amyloid beta, ADNI, memory decline, lipidation, biomarkers, central nervous system