Biology subjects

Brinton, R. D.

Publications and source records attributed to Brinton, R. D..

5 recordsLinked to original sources

bioRxiv2026

Addition of humanized APP to humanized APOE mouse model reduces brain size and increases the ratio of cortical representation

INTRODUCTION: Age, Apolipoprotein E4 (APOE4) genotype, and biological sex are major risk factors for late-onset Alzheimer's disease (LOAD), and preclinical mouse models enable controlled investigation of these factors. To date, humanized APOE4 has not recapitulated LOAD-relevant brain volume phenotypes. Given the central role of amyloid precursor protein (APP) in LOAD pathogenesis, incorporating humanized APP (hAPP) alongside humanized APOE (hAPOE) may therefore improve translational modeling of structural brain changes characterized by neuroimaging. METHODS: Aged mice (mean age = 23.25 months) carrying murine (m) or humanized (h) APP and either murine Apoe or hAPOE3/3 (hAPOE3-HOM), hAPOE3/4 (hAPOE4-HET), or hAPOE4/4 (hAPOE4-HOM) underwent in-skull ex vivo volumetric MRI. Regional volumes were quantified in absolute terms and relative to total brain volume (TBV). Linear models included APP type, APOE genotype, and sex, with FDR correction applied within contrasts. RESULTS: Brain volumes were primarily determined by APP background, with hAPP globally reducing total and regional volumes relative to mAPP mice. Across hAPP models, hAPOE4-HOM exhibited the greatest brain-wide reductions, which was mitigated by a single hAPOE3 allele. In contrast, mouse APP exerted modest effect in hAPOE, with hAPOE4 carriers exhibiting greater total volume without regional specificity. After TBV adjustment, hAPP mice exhibited subcortical vulnerability with relative cortical preservation. Females exhibited larger brain volumes than males, independent of APP or APOE genotype. DISCUSSION: hAPP induces distinctly smaller brain volumes in this humanized APOE knock-in model, and hAPOE4 homozygosity amplifies that effect, indicating genotype-dependent susceptibility. Because this study is cross-sectional and lacks histopathological confirmation, volume differences may reflect developmental or constitutive effects rather than neurodegeneration. Humanized APP and APOE are therefore necessary but not sufficient to recapitulate the complete volumetric signature of established LOAD. Longitudinal and histological studies are required to determine whether these differences reflect a prodromal trajectory or a developmental effect.

neuroscience↗

bioRxiv2026

APOE4 Accelerates Menopause-Associated Brain Metabolic Shift and Disrupts Bioenergetic Adaptation

IntroductionDisruption of brain glucose and lipid metabolism contributes to Alzheimers disease (AD) and often emerges before clinical symptoms. Women are at elevated AD risk due to menopause-associated estrogen decline, which impairs mitochondrial function and glucose metabolism. Womens risk of AD is further elevated by the APOE4 allele, the strongest genetic risk factor for late-onset AD. MethodsTo investigate the impact of APOE genotype on the menopausal metabolic transition, brain metabolomic and lipidomic profiling was conducted in humanized female APOE3/3, APOE3/4, and APOE4/4 mice across chronological and endocrinological stages of peri-to postmenopausal transition. ResultsAPOE3/3 mice exhibited dynamic regulation of brain metabolic systems that supported postmenopausal bioenergetic demand. In contrast, APOE3/4 and APOE4/4 mice displayed accelerated and altered metabolic shifts, resulting in postmenopausal amino acid depletion, reduced tricarboxylic acid (TCA) cycle intermediates, lipid accumulation, and alterations in brain lipid composition. A single APOE4 allele was sufficient to impair metabolic adaptation, while APOE4 homozygosity resulted in greater severity of deficits. DiscussionOutcomes of these analyses revealed that APOE4 accelerated menopause-related metabolic decline and compromised bioenergetic adaptation, providing a mechanistic basis for increased AD susceptibility and earlier onset in APOE4-positive women.

neuroscience↗

bioRxiv2025

Humanized APOE mouse brain volume increases over age irrespective of sex and APOE genotype: Implications for translational validity to the human

Translational validity of mouse models of human aging and late-onset Alzheimers disease (LOAD) risk are essential for both fundamental mechanistic science and therapeutic development. Given that the strongest risk factors for LOAD are age, female sex, and APOE-{varepsilon}4 carriership, models must reflect these biological variables and disease phenotypes. The use of mouse models with humanized APOE (hAPOE) is a key strategy to advance translational validity. To initially address translational validity of the hAPOE mouse model, we conducted ex-vivo magnetic resonance imaging analysis of brain volumes in male and female mice across APOE genotypes ({varepsilon}3/{varepsilon}3, {varepsilon}3/{varepsilon}4, {varepsilon}4/{varepsilon}4) and ages corresponding to a human lifespan of approximately 30-70 years (6-25 months in mice). The primary outcomes indicated that total MRI brain volume increased with age (an average of 2.12mm3 per month), irrespective of sex or APOE genotype. Additionally, APOE-{varepsilon}4 carriers had greater total brain volumes than non-carriers. No sex differences were observed in total brain volume. Voxelwise analyses revealed a pattern of localized morphometric changes independent of differences in total brain volume. Age-related volumetric increases were distributed across subcortical regions (e.g., thalami, hippocampi), while age-related decreases were evident across cortical regions, notably the bilateral parieto-temporal and frontal lobes. Additionally, sex differences were evident after controlling for total brain volume, with females showing greater cortex-dominant volumes while males showed a pattern of greater volumes in regions including cerebellar cortices, olfactory bulbs, and striata. No genotypic effects were observed in the voxelwise analysis after correcting for multiple comparisons, suggesting that APOE genotype does not drive localized volume differences independent of total brain volume. These findings indicate that, at the MRI level of analysis, this humanized APOE mouse model does not recapitulate the volumetric atrophy typically seen in human brain aging and Alzheimers disease. The results suggest that humanized APOE alone is insufficient to induce the LOAD atrophy phenotype. This model may better serve as a platform for studying vulnerable aging rather than a primary model for progressive neurodegenerative atrophy.

neuroscience↗

bioRxiv2025

White matter micro- and macrostructural properties in midlife individuals at risk for Alzheimer's disease: Associations with sex and menopausal status

Women are at greater lifetime risk for Alzheimers disease (AD), potentially due to midlife fractional anisotropy (FA) and lower mean diffusivity in fornix and corpus callosum, indicating more densely organized white matter. Perimenopausal women were the exception, with white matter profiles closely resembling those of men. Perimenopausal women exhibited minimal or absent fiber cross-section and FDC sex differences and a reversal of the fornix FA advantage observed in pre- and postmenopausal women. These cross-sectional results are consistent with sex differences in white matter organization. Importantly, the perimenopause emerges as a critical window of neural reorganization in the female midlife aging brain characterized by temporary convergence toward male-like white matter organization. Longitudinal analyses are key to identifying women who do or do not revert to a premenopausal profile, which may inform AD risk.

neuroscience↗

bioRxiv2019

The Alzheimer’s Disease Metabolome: Effects of Sex and APOE ε4 genotype

Recent studies have provided evidence that late-onset Alzheimers disease (AD) can in part be considered a metabolic disease. Besides age, female sex and APOE {varepsilon}4 genotype represent strong risk factors for AD. They also both give rise to large metabolic differences, suggesting that metabolic aspects of AD pathogenesis may differ between males and females and between APOE {varepsilon}4 carriers and non-carriers. We systematically investigated group-specific metabolic alterations by conducting stratified association analyses of 140 metabolites measured in serum samples of 1,517 AD neuroimaging initiative subjects, with AD biomarkers for A{beta} and tau pathology and neurodegeneration. We observed substantial sex differences in effects of 15 metabolites on AD biomarkers with partially overlapping differences for APOE {varepsilon}4 status groups. These metabolites highlighted several group-specific alterations not observed in unstratified analyses using sex and APOE {varepsilon}4 as covariates. Combined stratification by both variables uncovered further subgroup-specific metabolic effects limited to the group with presumably the highest AD risk: APOE {varepsilon}4+ females. Pathways linked to the observed metabolic alterations suggest that females experience more expressed impairment of mitochondrial energy production in AD than males. These findings indicate that dissecting metabolic heterogeneity in AD pathogenesis may enable grading of the biomedical relevance of specific pathways for specific subgroups. Extending our approach beyond simple one- or two-fold stratification may thus guide the way to personalized medicine.\n\nSignificance statementResearch provides substantial evidence that late-onset Alzheimers disease (AD) is a metabolic disease. Besides age, female sex and APOE{varepsilon}4 genotype represent strong risk factors for AD, and at the same time give rise to large metabolic differences. Our systematic investigation of sex and APOE {varepsilon}4 genotype differences in the link between metabolism and measures of pre-symptomatic AD using stratified analysis revealed several group-specific metabolic alterations that were not observed without sex and genotype stratification of the same cohort. Pathways linked to the observed metabolic alterations suggest females are more affected by impairment of mitochondrial energy production in AD than males, highlighting the importance of tailored treatment approaches towards a precision medicine approach.

bioinformatics↗