TOMM40 genetic variants show sex-specific effects on brain cholesterol and Alzheimer's biomarkers in mice
A study using humanized mice found that the TOMM40 '523' Short/Short genotype increases brain cholesterol and triglyceride levels in males but not females, along with higher levels of amyloid-beta 42, a key Alzheimer's disease biomarker. TOMM40 variants at the APOE-TOMM40 locus have been associated with Alzheimer's disease risk, but the mechanisms were unclear. These findings suggest a potential pathway linking TOMM40 genetic variation to Alzheimer's disease pathogenesis through lipid metabolism.
Researchers used a mouse model containing the entire human APOE3-TOMM40 locus to investigate how different TOMM40 '523' poly-T variants affect lipid levels and Alzheimer's biomarkers. The study compared mice homozygous for the Short (S/S) or Very Long (VL/VL) variants, measuring cholesterol and triglyceride content in brain, liver, and white adipose tissue, as well as brain levels of amyloid-beta 42 and tau. Male mice with the S/S genotype showed significantly higher brain cholesterol and triglyceride levels than VL/VL carriers, along with greater brain amyloid-beta 42 content; females showed no such differences. White adipose tissue displayed similar lipid patterns to the brain, while liver lipid content was largely comparable between genotypes, though VL/VL mice showed a trend toward higher triglycerides in a sex- and age-dependent manner. These results demonstrate that TOMM40 '523' variants drive tissue-specific and sex-dependent lipid differences that may link this genetic locus to Alzheimer's disease risk.
What's missing
The study's limitations include reliance on a mouse model, which may not fully recapitulate human APOE-TOMM40 biology; the mechanisms by which TOMM40 variants regulate lipid metabolism remain to be elucidated; and the functional significance of the observed sex differences in lipid levels and amyloid-beta accumulation requires further investigation. The study does not address whether these lipid changes directly cause cognitive decline or whether they are sufficient to induce Alzheimer's pathology in vivo.
What different sources said
- bioRxivCenter
TOMM40 '523' genotype induces sex- and tissue- specific differences in cholesterol and triglyceride levels in an APOE-TOMM40 humanized mouse model
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