BACKGROUND Alzheimer's disease (AD) is a fatal neurodegenerative disease. APOE4 is the greatest genetic risk factor for AD, increasing risk up to 15-fold compared to the common APOE3. Importantly, female (♀) APOE4 carriers have a greater risk for developing AD and an increased rate of cognitive decline compared to male (♂) APOE4 carriers. While recent evidence demonstrates that AD, APOE genotype, and sex affect the gut microbiome (GM), how APOE genotype and sex interact to affect the GM in AD remains unknown. METHODS This study analyzes the GM of 4-month (4 M) ♂ and ♀ E3FAD and E4FAD mice, transgenic mice that overproduce amyloid-β 42 (Aβ42) and express human APOE3+/+ or APOE4+/+. Fecal microbiotas were analyzed using high-throughput sequencing of 16S ribosomal RNA gene amplicons and clustered into operational taxonomic units (OTU). Microbial diversity of the EFAD GM was compared across APOE, sex and stratified by APOE + sex, resulting in 4-cohorts (♂E3FAD, ♀E3FAD, ♂E4FAD and ♀E4FAD). Permutational multivariate analysis of variance (PERMANOVA) evaluated differences in bacterial communities between cohorts and the effects of APOE + sex. Mann-Whitney tests and machine-learning algorithms identified differentially abundant taxa associated with APOE + sex. RESULTS Significant differences in the EFAD GM were associated with APOE genotype and sex. Stratification by APOE + sex revealed that APOE-associated differences were exhibited in ♂EFAD and ♀EFAD mice, and sex-associated differences were exhibited in E3FAD and E4FAD mice. Specifically, the relative abundance of bacteria from the genera Prevotella and Ruminococcus was significantly higher in ♀E4FAD compared to ♀E3FAD, while the relative abundance of Sutterella was significantly higher in ♂E4FAD compared to ♂E3FAD. Based on 29 OTUs identified by the machine-learning algorithms, heatmap analysis revealed significant clustering of ♀E4FAD separate from other cohorts. CONCLUSIONS The results demonstrate that the 4 M EFAD GM is modulated by APOE + sex. Importantly, the effect of APOE4 on the EFAD GM is modulated by sex, a pattern similar to the greater AD pathology associated with ♀E4FAD. While this study demonstrates the importance of interactive effects of APOE + sex on the GM in young AD transgenic mice, changes associated with the development of pathology remain to be defined.

中文翻译：

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APOE 和性别对幼年 EFAD 转基因小鼠肠道微生物组的协同作用。

背景阿尔茨海默病(AD)是一种致命的神经变性疾病。APOE4 是 AD 的最大遗传风险因素，与常见的 APOE3 相比，风险增加了 15 倍。重要的是，与男性 (♂) APOE4 携带者相比，女性 (♀) APOE4 携带者患 AD 的风险更大，认知能力下降的速度也更快。虽然最近的证据表明 AD、APOE 基因型和性别会影响肠道微生物组 (GM)，但 APOE 基因型和性别如何相互作用以影响 AD 中的 GM 仍然未知。方法 本研究分析了 4 个月 (4 M) ♂ 和 ♀ E3FAD 和 E4FAD 小鼠的 GM，它们是过量产生淀粉样蛋白 42 (Aβ42) 并表达人类 APOE3+/+ 或 APOE4+/+ 的转基因小鼠。使用 16S 核糖体 RNA 基因扩增子的高通量测序分析粪便微生物群，并将其聚类为操作分类单元 (OTU)。EFAD GM 的微生物多样性在 APOE、性别之间进行比较，并按 APOE + 性别进行分层，产生 4 个队列（♂E3FAD、♀E3​​FAD、♂E4FAD 和 ♀E4FAD）。排列多变量方差分析 (PERMANOVA) 评估了群组之间细菌群落的差异以及 APOE + 性别的影响。Mann-Whitney 测试和机器学习算法确定了与 APOE + 性别相关的差异丰富的分类群。结果 EFAD GM 的显着差异与 APOE 基因型和性别有关。APOE+性别分层显示♂EFAD和♀EFAD小鼠表现出APOE相关差异，E3FAD和E4FAD小鼠表现出性别相关差异。具体而言，与♀E3FAD相比，♀E4FAD中普氏菌属和瘤胃球菌属细菌的相对丰度显着更高，而与♂E3FAD相比，♂E4FAD中Sutterella的相对丰度显着更高。基于机器学习算法识别的 29 个 OTU，热图分析揭示了 ♀E4FAD 与其他队列分离的显着聚类。结论 结果表明 4 M EFAD GM 受 APOE + 性别调节。重要的是，APOE4 对 EFAD GM 的影响受性别调节，这种模式类似于与 ♀E4FAD 相关的更严重的 AD 病理。虽然这项研究证明了 APOE + 性别对年轻 AD 转基因小鼠 GM 的交互作用的重要性，但与病理学发展相关的变化仍有待确定。热图分析显示 ♀E4FAD 的显着聚类与其他队列分开。结论 结果表明 4 M EFAD GM 受 APOE + 性别调节。重要的是，APOE4 对 EFAD GM 的影响受性别调节，这种模式类似于与 ♀E4FAD 相关的更严重的 AD 病理。虽然这项研究证明了 APOE + 性别对年轻 AD 转基因小鼠 GM 的交互作用的重要性，但与病理学发展相关的变化仍有待确定。热图分析显示 ♀E4FAD 的显着聚类与其他队列分开。结论 结果表明 4 M EFAD GM 受 APOE + 性别调节。重要的是，APOE4 对 EFAD GM 的影响受性别调节，这种模式类似于与 ♀E4FAD 相关的更严重的 AD 病理。虽然这项研究证明了 APOE + 性别对年轻 AD 转基因小鼠 GM 的交互作用的重要性，但与病理学发展相关的变化仍有待确定。