Highlights d Aging leads to the most profound changes in brain gene expression networks d Immune module led by Alzheimer's risk genes Trem2/Tyrobp is upregulated with aging d Alzheimer's risk allele APOE4 increases the expression of Serpina3 family genes d Alzheimer's protective allele APOE2 drives unique serum metabolome profiles

Investigations of apolipoprotein E (APOE) gene, the major genetic risk modifier for Alzheimer’s disease (AD), have yielded significant insights into the pathogenic mechanism. Among the three common coding variants, APOE*ε4 increases, whereas APOE*ε2 decreases the risk of late-onset AD compared with APOE*ε3. Despite increased understanding of the detrimental effect of APOE*ε4, it remains unclear how APOE*ε2 confers protection against AD. Accumulating evidence suggests that APOE*ε2 protects against AD through both amyloid-β (Aβ)-dependent and independent mechanisms. In addition, APOE*ε2 has been identified as a longevity gene, suggesting a systemic effect of APOE*ε2 on the aging process. However, APOE*ε2 is not entirely benign; APOE*ε2 carriers exhibit increased risk of certain cerebrovascular diseases and neurological disorders. Here, we review evidence from both human and animal studies demonstrating the protective effect of APOE*ε2 against AD and propose a working model depicting potential underlying mechanisms. Finally, we discuss potential therapeutic strategies designed to leverage the protective effect of APOE2 to treat AD.

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Approximately half of Alzheimer’s disease (AD) brains have concomitant Lewy pathology at autopsy, suggesting that α-synuclein (α-SYN) aggregation is a regulated event in the pathogenesis of AD. Genome-wide association studies revealed that the ε4 allele of the apolipoprotein E (APOE4) gene, the strongest genetic risk factor for AD, is also the most replicated genetic risk factor for Lewy body dementia (LBD), signifying an important role of APOE4 in both amyloid-β (Aβ) and α-SYN pathogenesis. How APOE4 modulates α-SYN aggregation in AD is unclear. In this study, we aimed to determine how α-SYN is associated with AD-related pathology and how APOE4 impacts α-SYN seeding and toxicity. We measured α-SYN levels and their association with other established AD-related markers in brain samples from autopsy-confirmed AD patients (N = 469), where 54% had concomitant LB pathology (AD + LB). We found significant correlations between the levels of α-SYN and those of Aβ40, Aβ42, tau and APOE, particularly in insoluble fractions of AD + LB. Using a real-time quaking-induced conversion (RT-QuIC) assay, we measured the seeding activity of soluble α-SYN and found that α-SYN seeding was exacerbated by APOE4 in the AD cohort, as well as a small cohort of autopsy-confirmed LBD brains with minimal Alzheimer type pathology. We further fractionated the soluble AD brain lysates by size exclusion chromatography (SEC) ran on fast protein liquid chromatography (FPLC) and identified the α-SYN species (~ 96 kDa) that showed the strongest seeding activity. Finally, using human induced pluripotent stem cell (iPSC)-derived neurons, we showed that amplified α-SYN aggregates from AD + LB brain of patients with APOE4 were highly toxic to neurons, whereas the same amount of α-SYN monomer was not toxic. Our findings suggest that the presence of LB pathology correlates with AD-related pathologies and that APOE4 exacerbates α-SYN seeding activity and neurotoxicity, providing mechanistic insight into how APOE4 affects α-SYN pathogenesis in AD.

BackgroundHearing impairment negatively impacts students' development of academic, language and social skills. Even minimal unilateral hearing loss can hinder educational performance. We investigated the prevalence of ear diseases among secondary school students in the city of Xi'an, China in order to provide a foundation for evidence-based hearing healthcare.MethodsA stratified random sampling survey was conducted in 29 secondary schools. Demographics and medical histories were collected, and otologic examinations were performed. Questionnaires were administered to assess insomnia, academic stress and use of portable audio devices. Logistic regression analysis was used to identify factors associated with hearing impairment, and the association of sensorineural hearing loss with insomnia, academic stress and the use of portable audio devices was analyzed with the chi-square test.ResultsThe percentage of students with some form of ear disease was 3.32%. External ear disease, middle ear disease and sensorineural hearing loss occurred in 1.21%, 0.64% and 1.47% of the students, respectively. Boys had a relatively higher prevalence of ear disease than girls. According to our survey, the prevalence of sensorineural hearing loss increased significantly among the students with insomnia and extended use of portable audio devices, but not among those with elevated levels of academic stress. Hearing aids and surgical treatment were needed in 1.47% and 0.89% of the students, respectively.ConclusionsThere is a high prevalence of ear disease among secondary school students, and this should be given more attention. Insomnia and the excessive use of portable audio devices may be related to adolescent sensorineural hearing loss. It is important to establish and comply with an evidence-based preventive strategy.