Associations between homocysteine, tau, and neurodegenerative markers in apolipoprotein ε4 non‐carriers with clinical Alzheimer’s disease
Bibliographic record
Abstract
Abstract Background Homocysteine (Hcy) is an amino acid generated as a byproduct of methionine metabolism. It is a risk factor for vascular and neurodegenerative diseases. This study investigated relationships between plasma Hcy concentrations and neurodegenerative biomarkers in people clinically diagnosed with Alzheimer’s disease (AD) or mild cognitive impairment (MCI) due to AD. Method Participants were identified from the Ontario Neurodegenerative Disease Research Initiative. Brain parenchymal fraction (BPF) was quantified using T1‐ and T2‐weighted structural magnetic resonance imaging with an in‐house Semi‐Automated Brain Region Extraction and Lesion Explorer package. Plasma amyloid beta (Aβ) 42, Aβ40, phosphorylated tau 181 (p‐tau181), and neurofilament light chain (NfL) were measured with Single molecule array (Simoa) assays. Linear regression analyses were used to test associations between Hcy and neuroimaging or plasma biomarkers, controlling for age, sex, hypertension, hyperlipidemia, diabetes, cholesterol, and vitamin B12. Analyses were stratified by apolipoprotein E (APOE) ε4 carrier status (non‐carriers: n = 64, mean age = 70.9 years, 41% female; carriers: n = 62, mean age = 71.2 years, 50% female). Result In APOE ε4 non‐carriers, Hcy was associated negatively with BPF (β = ‐0.233, p = 0.047, 95% CI [‐0.460, ‐0.003]), notably in temporal lobe regions in exploratory regional analyses. Hcy was also associated positively with plasma concentrations of NfL (β = 0.403, p = 0.007, 95% CI [0.117, 0.688]) and p‐tau181 (β = 0.357, p = 0.023, 95% CI [0.051, 0.663]) in APOE ε4 non‐carriers. Also, in APOE ε4 non‐carriers, Hcy was associated positively with Aβ40 (β = 0.367, p = 0.015, 95% CI [0.074, 0.660]) and Aβ42 (β = 0.305, p = 0.041, 95% CI [0.012, 0.598]), but not with the Aβ42/40 ratio (β = 0.155, p = 0.339, 95% CI [‐0.166, 0.476]). None of these associations were seen in APOE ε4 carriers. Conclusion In non‐carriers of the APOE ε4 allele clinically diagnosed with AD or MCI, homocysteine was associated with Amyloid, tau and neurodegeneration. The specificity of these relationships to ε4 non‐carriers identifies a unique risk factor profile for AD that is independent of APOE ε4 status.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".