Female Alzheimer's Disease Patients Research Articles

Sex-Specific Effects of Anxiety on Cognition and Activity-Dependent Neural Networks: Insights from (Female) Mice and (Wo)Men

Neuropsychiatric symptoms (NPS), such as depression and anxiety, are observed in 90% of Alzheimer's disease (AD) patients, two-thirds of whom are women. NPS usually manifest long before AD onset creating a therapeutic opportunity. Here, we examined the impact of anxiety on AD progression and the underlying brain-wide neuronal mechanisms. To gain mechanistic insight into how anxiety impacts AD progression, we performed a cross-sectional analysis on mood, cognition, and neural activity utilizing the ArcCreERT2 x enhanced yellow fluorescent protein (eYFP) x APP/PS1 (AD) mice. The ADNI dataset was used to determine the impact of anxiety on AD progression in human subjects. Female APP/PS1 mice exhibited anxiety-like behavior and cognitive decline at an earlier age than control (Ctrl) mice and male mice. Brain-wide analysis of c-Fos+ revealed changes in regional correlations and overall network connectivity in APP/PS1 mice. Sex-specific eYFP+/c-Fos+ changes were observed; female APP/PS1 mice exhibited less eYFP+/c-Fos+ cells in dorsal CA3 (dCA3), while male APP/PS1 mice exhibited less eYFP+/c-Fos+ cells in the dorsal dentate gyrus (dDG). In the ADNI dataset, anxiety predicted transition to dementia. Female subjects positive for anxiety and amyloid transitioned more quickly to dementia than male subjects. While future studies are needed to understand whether anxiety is a predictor, a neuropsychiatric biomarker, or a comorbid symptom that occurs during disease onset, these results suggest that there are sex differences in AD network dysfunction, and that personalized medicine may benefit male and female AD patients rather than a one size fits all approach.

Ovariectomy exacerbates the disturbance of excitation- inhibition balance in the brain of APP/PS-1/tau mice.

The prevalence of Alzheimer's disease (AD) is significantly gender-differentiated, with the number of female AD patients far exceeding that of males, accounting for two-thirds of the total prevalence. Although postmenopausal AD mice have been shown to have more prominent pathologic features and memory impairments than normal AD mice, the relevant molecular mechanisms leading to these outcomes have not been well elucidated. In the present study, we used the disturbance of excitation-inhibition balance in the postmenopausal brain as an entry point to explore the link between estrogen deficiency, disorders of the glutamatergic-GABAergic nervous system, and memory impairment. Wild-type (WT) mice and APP/PS1/tau (3 × Tg-AD) mice (10 months old) were randomly divided into four groups: WT+Sham group, WT+OVX group, 3 × Tg-AD+Sham group and 3 × Tg-AD+OVX group. Ovariectomy (OVX) was performed in the WT+OVX group and the 3 × Tg-AD+OVX group, and sham surgery was performed in the WT+Sham group and the 3 × Tg-AD+Sham group. The learning and memory ability and the anxiety and depression-like behavior changes of mice were evaluated by behavioral experiments, and the association between estrogen-estrogen receptors pathway and glutamatergic/GABAergic nervous system and female AD was evaluated by neurochemical experiments. In WT and 3 × Tg-AD mice, OVX resulted in impaired learning and memory abilities and anxiety and depression-like behaviors; reduced estrogen levels and downregulated the expression of estrogen receptors; upregulated the expression of amyloid-β, amyloid precursor protein, presenilin 1, and p-tau; upregulated the expression of Bcl-2-associated X protein and downregulated the expression of B-cell lymphoma-2, promoting cell apoptosis; reduced the number of neuronal dendrites and downregulated the expression of postsynaptic density protein-95; more importantly, OVX increased brain glutamate levels but downregulated the expression of N-methyl-D-aspartate receptor-2B, excitatory amino acid transporter 1, excitatory amino acid transporter 2, γ-aminobutyric acid receptor-A and γ-aminobutyric acid receptor-B. Our results suggested that OVX-induced estrogen-estrogen receptors pathway disruption caused learning and memory impairment and anxiety and depression-like behaviors, upregulated the expression of AD pathological markers, promoted apoptosis, destroyed neuronal structure, and most importantly, caused glutamatergic/GABAergic nervous system disorders.

An integrated approach to identifying sex-specific genes, transcription factors, and pathways relevant to Alzheimer's disease

BackgroundAge represents a significant risk factor for the development of Alzheimer's disease (AD); however, recent research has documented an influencing role of sex in several features of AD. Understanding the impact of sex on specific molecular mechanisms associated with AD remains a critical challenge to creating tailored therapeutic interventions. MethodsThe exploration of the sex-based differential impact on disease (SDID) in AD used a systematic review to first select transcriptomic studies of AD with data regarding sex in the period covering 2002 to 2021 with a focus on the primary brain regions affected by AD - the cortex (CT) and the hippocampus (HP). A differential expression analysis for each study and two tissue-specific meta-analyses were then performed. Focusing on the CT due to the presence of significant SDID-related alterations, a comprehensive functional characterization was conducted: protein-protein network interaction and over-representation analyses to explore biological processes and pathways and a VIPER analysis to estimate transcription factor activity. ResultsWe selected 8 CT and 5 HP studies from the Gene Expression Omnibus (GEO) repository for tissue-specific meta-analyses. We detected 389 significantly altered genes in the SDID comparison in the CT. Generally, female AD patients displayed more affected genes than males; we grouped said genes into six subsets according to their expression profile in female and male AD patients. Only subset I (repressed genes in female AD patients) displayed significant results during functional profiling. Female AD patients demonstrated more significant impairments in biological processes related to the regulation and organization of synapsis and pathways linked to neurotransmitters (glutamate and GABA) and protein folding, Aβ aggregation, and accumulation compared to male AD patients. These findings could partly explain why we observe more pronounced cognitive decline in female AD patients. Finally, we detected 23 transcription factors with different activation patterns according to sex, with some associated with AD for the first time. All results generated during this study are readily available through an open web resource Metafun-AD (https://bioinfo.cipf.es/metafun-ad/). ConclusionOur meta-analyses indicate the existence of differences in AD-related mechanisms in female and male patients. These sex-based differences will represent the basis for new hypotheses and could significantly impact precision medicine and improve diagnosis and clinical outcomes in AD patients.

Sex differences in luteinizing hormone aggravates Aβ deposition in APP/PS1 and Aβ1-42-induced mouse models of Alzheimer's disease

Alzheimer's disease (AD) exhibits a higher incidence rate among older women, and dysregulation of the hypothalamic-pituitary-gonadal (HPG) axis during aging is associated with cognitive impairments and the development of dementia. luteinizing hormone (LH) has an important role in CNS function, such as mediating neuronal pregnenolone production, and modulating neuronal plasticity and cognition. The sex differences in LH and its impact on Aβ deposition in AD individuals remain unclear, with no reported specific mechanisms. Here, we show through data mining that LH-related pathways are significantly enriched in female AD patients. Additionally, LH levels are elevated in female AD patients and exhibit a negative correlation with cognitive levels but a positive correlation with AD pathology levels, and females exhibit a greater extent of AD pathology, such as Aβ deposition. In vivo, we observed that the exogenous injection of LH exacerbated behavioral impairments induced by Aβ1-42 in mice. LH injection resulted in worsened neuronal damage and increased Aβ deposition. In SH-SY5Y cells, co-administration of LH with Aβ further exacerbated Aβ-induced neuronal damage. Furthermore, LH can dose-dependently decrease the levels of NEP and LHR proteins while increasing the expression of GFAP and IBA1 in vivo and in vitro. Taken together, these results indicate that LH can exacerbate cognitive impairment and neuronal damage in mice by increasing Aβ deposition. The potential mechanism may involve the reduction of NEP and LHR expression, along with the exacerbation of Aβ-induced inflammation.

Plasma Biomarkers in Neurodegenerative Dementias: Unrevealing the Potential of Serum Oxytocin, BDNF, NPTX1, TREM2, TNF-alpha, IL-1 and Prolactin.

Dementia encompasses a range of neurodegenerative disorders characterized by cognitive decline and functional impairment. The identification of reliable biomarkers is essential for accurate diagnosis and gaining insights into the mechanisms underlying diseases. This study aimed to investigate the plasma biomarker profiles associated with Brain- Derived Neurotrophic Factor (BDNF), Oxytocin, Neuronal Pentraxin-1 (NPTX1), Triggering Receptor Expressed on Myeloid Cells 2 (TREM2), Tumor Necrosis Factor-alpha (TNF-alpha), Interleukin- 1 (IL-1) and Prolactin in Alzheimer's disease (AD), dementia with Lewy bodies (DLB), frontotemporal dementias (FTD) and healthy controls. Serum levels of the aforementioned biomarkers were analyzed in 23 AD, 28 DLB, 15 FTD patients recruited from outpatient units and 22 healthy controls. Diagnostic evaluations followed established criteria and standardized clinical tests were conducted. Blood samples were collected and analyzed using ELISA and electrochemiluminescence immunoassay methods. Serum BDNF and oxytocin levels did not significantly differ across groups. NPTX1, TREM2, TNF-alpha and IL-1 levels also did not show significant differences among dementia groups. However, prolactin levels exhibited distinct patterns, with lower levels in male DLB patients and higher levels in female AD patients compared to controls. The study findings suggest potential shared mechanisms in dementia pathophysiology and highlight the importance of exploring neuroendocrine responses, particularly in AD and DLB. However, further research is warranted to elucidate the role of these biomarkers in dementia diagnosis and disease progression.

The role of microRNAs in understanding sex-based differences in Alzheimer’s disease

BackgroundThe incidence of Alzheimer's disease (AD)—the most frequent cause of dementia—is expected to increase as life expectancies rise across the globe. While sex-based differences in AD have previously been described, there remain uncertainties regarding any association between sex and disease-associated molecular mechanisms. Studying sex-specific expression profiles of regulatory factors such as microRNAs (miRNAs) could contribute to more accurate disease diagnosis and treatment.MethodsA systematic review identified six studies of microRNA expression in AD patients that incorporated information regarding the biological sex of samples in the Gene Expression Omnibus repository. A differential microRNA expression analysis was performed, considering disease status and patient sex. Subsequently, results were integrated within a meta-analysis methodology, with a functional enrichment of meta-analysis results establishing an association between altered miRNA expression and relevant Gene Ontology terms.ResultsMeta-analyses of miRNA expression profiles in blood samples revealed the alteration of sixteen miRNAs in female and 22 miRNAs in male AD patients. We discovered nine miRNAs commonly overexpressed in both sexes, suggesting a shared miRNA dysregulation profile. Functional enrichment results based on miRNA profiles revealed sex-based differences in biological processes; most affected processes related to ubiquitination, regulation of different kinase activities, and apoptotic processes in males, but RNA splicing and translation in females. Meta-analyses of miRNA expression profiles in brain samples revealed the alteration of six miRNAs in female and four miRNAs in male AD patients. We observed a single underexpressed miRNA in female and male AD patients (hsa-miR-767-5p); however, the functional enrichment analysis for brain samples did not reveal any specifically affected biological process.ConclusionsSex-specific meta-analyses supported the detection of differentially expressed miRNAs in female and male AD patients, highlighting the relevance of sex-based information in biomedical data. Further studies on miRNA regulation in AD patients should meet the criteria for comparability and standardization of information.

Sex‐specific neuropsychiatric burden distinguished by APOE4 status and cortical thickness

AbstractBackgroundThe APOE ε4 (APOE4) allele is a genetic risk factor for Alzheimer’s disease (AD). Prior work by our group found a significant association between the APOE4 allele and presence of psychosis as well as overall increased neuropsychiatric symptom (NPS) burden in female APOE4 homozygote AD patients, with no effect present in males. In this study, we sought to examine the relationship between APOE4 carrier status and sex on NPS burden from a neuroimaging perspective, with the aim to determine what brain regions may be driving this effect.MethodA cohort of 752 AD patients were selected from the National Alzheimer’s Coordinating Center (NACC) database: 104 APOE4 homozygotes (40F|64M), 304 APOE4 heterozygotes (160F|144M) and 310 APOE4 non‐carriers (131F|179M). Presence of NPS was identified using the Neuropsychiatric Inventory (NPI). Structural T1‐weighted images were downloaded from the NACC imaging dataset and cortical thickness measures corresponding to frontal, cingulate, temporal and parietal regions were assessed. Statistical analysis included a Bayesian multilevel regression where cortical thickness was modeled as an outcome variable against an interaction between sex and APOE4 homozygote status (0|1), while controlling for heterozygote status, APOE4 non‐carrier status, age, sex and MMSE as predictor variables. Within‐ and between‐groups mean differences in thickness were measured as a probability density estimate (Highest Density interval), and partial correlation was used to examine NPI correlates to thickness.ResultFemale APOE4 homozygotes displayed a high probability (>90%HDI) of greater cortical thickness in the posterior cingulate and isthmus cingulate regions bilaterally and reduced cortical thickness in temporal regions (Figure 1). Cortical thickness in the fusiform cortex was positively correlated to greater NPI burden (p<0.05) among female homozygotes, and negatively correlated to NPI burden among female heterozygotes. Cortical thickness in males, regardless of carrier status, did not correlate to NPI burden in any region.ConclusionThis study highlights an important relationship between the fusiform cortex and NPI burden in female APOE4 carriers, marking a female‐specific effect. Future work should further disentangle sex differences in APOE4 status and psychosis with a focus on the fusiform cortex as a potential region of interest.

Cell‐type deconvolution analysis of RNAseq data reveals cell‐specific glycosylation changes in the brains of Alzheimer’s Disease patients

AbstractBackgroundIntriguing evidence that glycosylation is disrupted in Alzheimer’s Disease (AD) has emerged. However, our knowledge of cell‐specific alterations in the expression of genes involved in glycosylation in the brains of AD patients is limited.MethodIn this study, we conducted cell type deconvolution analysis of whole‐tissue RNAseq data to characterize cell type compositional differences and alterations in the expression of glycosylation related genes in the brains of AD patients and those with no cognitive impairment (NCI). Single‐cell human brain RNA‐seq data were obtained from the Allen Brain Map Atlas, consisting of 76,533 total nuclei derived from the cortical tissue of 2 humans. The identified cell types included GABAergic neurons, glutamatergic neurons, astrocytes, oligodendrocytes, oligodendrocyte precursor cells (OPC), microglia, endothelial cells, and vascular leptomeningeal cell (VLMC). The cell‐type deconvolution package CIBERSORT was applied in relative mode with S‐mode (single‐cell mode) batch correction to impute cell fractions and cell‐type‐specific gene expression profiles for NCI and AD samples in the ROSMAP dataset. The differences between cell type fractions of NCI and AD were analyzed by linear mixed regression model and t‐test.ResultIn the dorsolateral prefrontal cortex, neuronal cells represented the highest proportion of cells (∼30‐33%), followed by astrocytes (∼30%), and oligodendrocytes (∼20%), endothelial cells (∼7%), microglia (∼7%), VLMC (∼2‐3%), and OPC (<1%). The overall cell type composition was not significantly different between NCI and AD patients, however, the proportion of microglia, VLMC, and OPC was significantly higher in AD patients (p<0.05). The proportion of glutamatergic neuronal cells was significantly lower in female AD patients (p<0.05) compared with NCI controls, but not in males after controlling for age. Microglia‐associated expression of the glycosyltransferases MGAT1, ST6GAL1, and ST6GALNAC3 was observed in AD patients but not in NCI controls. Glutamatergic neuronal cells and VLMC cells associated with the expression of GALNT10 was observed in AD patients but not in NCI controls. In contrast, GALNT11 expression associated with astrocytes was observed in NCI controls but not in AD patients.ConclusionOur findings indicate changes in cell‐type proportions and cell‐specific changes in glycosyltransferase gene expression in the brains of AD patients compared with NCI controls.

Unfavorable effects of memantine on the skeletal system in female rats

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist used in the treatment of Alzheimer's disease (AD). NMDA receptors are expressed on bone cells. The aim of the present study was to investigate the effects of memantine on the rat musculoskeletal system. Taking into account that most of female AD patients are postmenopausal, the study was carried out on intact and ovariectomized (estrogen-deficient) rats. Mature Wistar rats were divided into following groups: non-ovariectomized (NOVX) control rats, NOVX rats treated with memantine, ovariectomized (OVX) control rats, and OVX rats treated with memantine. Memantine (2 mg/kg p.o.) was administered once daily for four weeks, starting one week after ovariectomy. The serum bone turnover marker and cytokine levels, bone density, mass, mineralization, mechanical properties, histomorphometric parameters of compact and cancellous bone, skeletal muscle mass and grip strength were determined. In NOVX rats, memantine slightly decreased the strength of compact bone of the femoral diaphysis (parameters in the yield point) and unfavorably affected histomorphometric parameters of cancellous bone (the femoral epiphysis and metaphysis). In OVX rats, in which estrogen deficiency induced osteoporotic changes, memantine increased the phosphorus content in the femoral bone mineral. No other effects on bone were observed in the memantine-treated OVX rats. In conclusion, the results of the present study indicated slight damaging skeletal effects of memantine in rats with normal estrogen levels.

Retinal pathological features and proteome signatures of Alzheimer’s disease

Alzheimer’s disease (AD) pathologies were discovered in the accessible neurosensory retina. However, their exact nature and topographical distribution, particularly in the early stages of functional impairment, and how they relate to disease progression in the brain remain largely unknown. To better understand the pathological features of AD in the retina, we conducted an extensive histopathological and biochemical investigation of postmortem retina and brain tissues from 86 human donors. Quantitative examination of superior and inferior temporal retinas from mild cognitive impairment (MCI) and AD patients compared to those with normal cognition (NC) revealed significant increases in amyloid β-protein (Aβ42) forms and novel intraneuronal Aβ oligomers (AβOi), which were closely associated with exacerbated retinal macrogliosis, microgliosis, and tissue atrophy. These pathologies were unevenly distributed across retinal layers and geometrical areas, with the inner layers and peripheral subregions exhibiting most pronounced accumulations in the MCI and AD versus NC retinas. While microgliosis was increased in the retina of these patients, the proportion of microglial cells engaging in Aβ uptake was reduced. Female AD patients exhibited higher levels of retinal microgliosis than males. Notably, retinal Aβ42, S100 calcium-binding protein B+ macrogliosis, and atrophy correlated with severity of brain Aβ pathology, tauopathy, and atrophy, and most retinal pathologies reflected Braak staging. All retinal biomarkers correlated with the cognitive scores, with retinal Aβ42, far-peripheral AβOi and microgliosis displaying the strongest correlations. Proteomic analysis of AD retinas revealed activation of specific inflammatory and neurodegenerative processes and inhibition of oxidative phosphorylation/mitochondrial, and photoreceptor-related pathways. This study identifies and maps retinopathy in MCI and AD patients, demonstrating the quantitative relationship with brain pathology and cognition, and may lead to reliable retinal biomarkers for noninvasive retinal screening and monitoring of AD.

Noncanonical regulation of imprinted gene Igf2 by amyloid-beta 1–42 in Alzheimer’s disease

Reduced insulin-like growth factor 2 (IGF2) levels in Alzheimer’s disease (AD) may be the mechanism relating age-related metabolic disorders to dementia. Since Igf2 is an imprinted gene, we examined age and sex differences in the relationship between amyloid-beta 1–42 (Aβ42) accumulation and epigenetic regulation of the Igf2/H19 gene cluster in cerebrum, liver, and plasma of young and old male and female 5xFAD mice, in frontal cortex of male and female AD and non-AD patients, and in HEK293 cell cultures. We show IGF2 levels, Igf2 expression, histone acetylation, and H19 ICR methylation are lower in females than males. However, elevated Aβ42 levels are associated with Aβ42 binding to Igf2 DMR2, increased DNA and histone methylation, and a reduction in Igf2 expression and IGF2 levels in 5xFAD mice and AD patients, independent of H19 ICR methylation. Cell culture results confirmed the binding of Aβ42 to Igf2 DMR2 increased DNA and histone methylation, and reduced Igf2 expression. These results indicate an age- and sex-related causal relationship among Aβ42 levels, epigenomic state, and Igf2 expression in AD and provide a potential mechanism for Igf2 regulation in normal and pathological conditions, suggesting IGF2 levels may be a useful diagnostic biomarker for Aβ42 targeted AD therapies.

Relationship between sarcopenia and sleep status in female patients with mild to moderate Alzheimer's disease.

Sleep disorders and sarcopenia could contribute to the development of Alzheimer's disease (AD), which are risk factors that rapidly deteriorate cognitive functions. However, few studies have evaluated the relationship between sarcopenia and sleep disorders in female AD patients, who have a higher prevalence than male patients. This study aimed to investigate the relationship between sarcopenia and sleep status in female patients with mild to moderate AD. This cross-sectional study recruited 112 female outpatients aged between 60 and 85 years. Demographic characteristics, appendicular skeletal muscle mass index (ASMI), grip strength, and gait speed were assessed. Sarcopenia was diagnosed according to criteria of the Asian Working Group for Sarcopenia. Pittsburgh Sleep Quality Index (PSQI) assessed sleep variables. Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) assessed cognitive function. Binary logistic regression models explored the relationship between sleep variables and cognitive function and sarcopenia, adjusting for potential cofounders. The outpatients were divided into 36 AD patients with sarcopenia (ADSa) and 76 AD patients without sarcopenia (ADNSa), with a prevalence of 32.1%. ADSa had lower ASMI, weaker grip strength, slower gait speed, a higher incidence of poor sleep quality and poorer cognitive function. Multivariate binary logistic regression analysis showed that high total scores of PSQI (odds ratio (OR)=1.13), poor sleep quality (OR=2.73), poor subjective sleep quality (OR=1.83), low MMSE (OR=0.77) and MoCA (OR=0.76) scores were associated with high odds of sarcopenia. Compared to sleep time ≤ 15 min, >60 min (OR=5.01) were associated with sarcopenia. Sleep duration <6h (OR=3.99), 8-9h (OR=4.48) and ≥9h (OR=6.33) were associated with sarcopenia compared to 7-8h. More sleep symptoms and cognitive impairment exist in female patients with sarcopenia. The higher total scores of PSQI, poorer subjective sleep quality, longer sleep latency, excessive and insufficient sleep duration and poorer cognitive function are associated with higher odds of sarcopenia in female patients with mild to moderate AD.

Effect of long-term cannabidiol on learning and anxiety in a female Alzheimer's disease mouse model.

Cannabidiol is a promising potential therapeutic for neurodegenerative diseases, including Alzheimer’s disease (AD). Our laboratory has shown that oral CBD treatment prevents cognitive impairment in a male genetic mouse model of AD, the amyloid precursor protein 1 x presenilin 1 hemizygous (APPxPS1) mouse. However, as sex differences are evident in clinical populations and in AD mouse models, we tested the preventive potential of CBD therapy in female APPxPS1 mice. In this study, 2.5-month-old female wildtype-like (WT) and APPxPS1 mice were fed 20 mg/kg CBD or a vehicle via gel pellets daily for 8 months and tested at 10.5 months in behavioural paradigms relevant to cognition (fear conditioning, FC; cheeseboard, CB; and novel object recognition test, NORT) and anxiety-like behaviours (elevated plus maze, EPM). In the CB, CBD reduced latencies to find a food reward in APPxPS1 mice, compared to vehicle-treated APPxPS1 controls, and this treatment effect was not evident in WT mice. In addition, CBD also increased speed early in the acquisition of the CB task in APPxPS1 mice. In the EPM, CBD increased locomotion in APPxPS1 mice but not in WT mice, with no effects of CBD on anxiety-like behaviour. CBD had limited effects on the expression of fear memory. These results indicate preventive CBD treatment can have a moderate spatial learning-enhancing effect in a female amyloid-β-based AD mouse model. This suggests CBD may have some preventive therapeutic potential in female familial AD patients.

Sex-Related Microglial Perturbation Is Related to Mitochondrial Changes in a Model of Alzheimer’s Disease

Many studies implicate microglia in the pathogenesis of Alzheimer’s disease (AD) but precisely how these cells make their impact has not been determined to date. One contributory factor is likely to be the enhanced production of inflammatory mediators and it is now known that microglia with this secretory phenotype exhibit other adaptations including in their morphology, function, and metabolism. AD, like many neurological disorders, demonstrates a sex bias and recent evidence indicates that the sexual dimorphism in microglial function, which has been recognized for many years in early development, persists into adulthood and aging. Here, we demonstrate sex-related differences in microglia from post mortem tissue of male and female AD patients and a marked increase in the number of dystrophic and rod-shaped microglia in tissue from female AD patients compared with males. Furthermore, there was an increase in iron-laden microglia in tissue from female AD patients and this has been reported to reflect mitochondrial changes. To address this further, we assessed changes in microglia from male and female APP/PS1 mice and demonstrate that iron accumulation in microglia is increased to a greater extent in tissue prepared from females compared with males. This was associated with altered expression of genes coding for proteins that modulate mitochondrial function. The findings suggest that sex-related differences in the severity and perhaps incidence of AD may, at least in part, arise from sexual dimorphism in microglia.

Correlation of serum lipids levels of Alzheimer's disease patients with sex, age and apolipoprotein E gene polymorphism

Objective: To explore the correlation of serum lipids levels of Alzheimer's disease (AD) patients with sex, age and apolipoprotein E (Apo E) gene polymorphism. Methods: The retrospective study method was used, and 407 AD patients (142 males and 265 females, aged 52-91 years) were selected from Beijing Tiantan Hospital from January 2015 to August 2021 as the research target, and 894 healthy persons (339 males and 555 females, aged 52-94 years) who did body examination were selected as the control group. The AD patients were divided into four age groups according to the age interval of 10 years, including 85 aged 50-59 years, 163 aged 60-69 years, 119 aged 70-79 years, and 40 aged more than 80 years. The serum lipids levels were detected by biochemical analyzer, including triglycerides (TG), cholesterol (CHO), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), apolipoproteinA1(Apo A1) and apolipoprotein B (Apo B). ApoE gene polymorphism were detected by PCR fluorescent probe method. Mann-Whitney U test and Kruskal-Wallis H test were used to compare the serum lipids levels in each group. Results: The levels of serum CHO and LDL-C were 3.30(1.41,4.82) mmol/L and 1.76(1.39,2.78) mmol/L in AD patients, and 4.84(4.24, 5.56) mmol/L and 2.91(2.36, 3.57) mmol/L in control group, and the levels of serum CHO and LDL-C of AD patients were significantly lower than control group (Z=-15.172,Z=-14.583, P<0.001, P<0.001). The levels of serum HDL-C and Apo B were 1.84(1.30, 3.88) mmol/L and 1.17(0.85, 1.57) g/L in AD patients, and 1.39(1.18, 1.64) mmol/L and 0.93(0.81, 1.09) g/L in control group, and the levels of serum HDL-C and Apo-B of AD patients were significantly higher than control group (Z=-12.249, Z=-9.706, P<0.001, P<0.001). There was no significant difference in TG and Apo A1 between 2 groups (Z=-1.577, Z=-0.408, P=0.115, P=0.683). The levels of TG, CHO, LDL-C in female AD patients were significantly higher than male patients (Z=-2.737, Z=-3.963, Z=-4.417, P=0.006, P<0.001, P<0.001). There were significant differences in TG, CHO, HDL-C, LDL-C, Apo A1 and Apo B among AD patients of all age groups (Z=11.263, Z=10.060, Z=40.246, Z=10.451, Z=24.315, Z=19.922, P=0.010, P=0.018, P<0.001, P=0.015, P<0.001, P<0.001). The serum CHO and LDL-C levels were positively correlated with age (rs=0.160, rs=0.174, P=0.001, P<0.001), and HDL-C, Apo A1 and Apo B levels were negatively correlated with age (rs=-0.312, rs=-0.272, rs=-0.146, P<0.001, P<0.001, P=0.003), and there was no correlation between TG level and age in AD patients (rs=0.086, P=0.082). There were 3 cases (3.33%) of E2, 43 cases of E3 (47.78%) and 44 cases of E4 (48.89%) in AD patients, and 22 cases (12.72%) of E2, 117 cases of E3 (67.63%) and 34 cases of E4 (19.65%) in control group. There was significant difference in Apo E genotype distribution between AD patients and control group (χ²=26.381, P<0.001). Apo E4 was the most common genotype in AD patients, and the proportion was 48.89%. Except for Apo A1(Z=7.821, P=0.020), there was no significant difference in TG, CHO, HDL-C, LDL-C and Apo B levels among all patients with different genotypes (Z=3.732, Z=1.677, Z=1.455, Z=1.619, Z=2.202, P=0.155, P=0.432, P=0.483, P=0.445, P=0.333). Conclusion: The levels of CHO and LDL-C decreased while the levels of HDL-C and Apo B increased in AD patients. The dyslipidemia in AD patients might be correlated with age, but not sex and Apo E genotypes.

Sex-Specific Regulation of β-Secretase: A Novel Estrogen Response Element (ERE)-Dependent Mechanism in Alzheimer's Disease.

Women have a higher prevalence and incidence of Alzheimer's disease (AD) than age-matched men, and loss of estrogen might be partially responsible for the higher risk of AD in aged women. While β-secretase (BACE1) plays an important role in AD pathogenesis, whether BACE1 involved the sex difference in AD pathology remains unclear. This study investigated the hypothesis that estrogen regulates BACE1 transcription via the estrogen response element (ERE) and designated pathways. Using estrogen receptor (ER) knock-out mice and mutagenesis of EREs in HEK293 cells, we demonstrated sex-specific inhibition of BACE1 transcription by estrogen via direct binding to ERE sites and ERα. We also used a repressor of estrogen receptor activity (REA) and showed that an REA-ERE complex downregulated BACE1. A chromatin immunoprecipitation assay analysis determined that all three EREs at the BACE1 promoter were required for estradiol-mediated downregulation of BACE1 transcription in mice. Last, we confirmed the impairment of the REA pathway in the cortex of female AD patients. Our study identified an estrogen-specific BACE1 transcriptional regulation pathway from cell and animal models to AD patients.SIGNIFICANCE STATEMENT With the increase in the aging population and Alzheimer's disease worldwide, an urgent need to find effective approaches to treat or prevent AD. Women have a higher prevalence and incidence of AD than men. Identification of the sex-specific risk for AD may be valuable for disease prevention. This study evaluated several estrogen response element (ERE) sites on the promoter of β-secretase (BACE1), a key enzyme for AD pathology. We demonstrated that estrogen downregulated BACE1 transcription through direct binding and complex formation with ERE and cofactors. Our novel findings provide evidence that an estrogen supplement may decrease the risk of AD in menopausal and postmenopausal women. Furthermore, this study demonstrates the "sex-specific" mechanisms of BACE1 as a role in AD pathogenesis.

A novel key driver gene of Alzheimer's disease impacts AD-related cognitive deficit, pathology and neuro-inflammation in sex- and APOE-specific manners.

Alzheimer's Disease (AD) has complex etiologies and the impact of sex on AD varies over the course of disease development. Literature provides some evidence of sex-specific contributions to AD. However, molecular mechanisms of sex biased differences in AD remain elusive. Multi-omics data in tandem with systems biology approaches offer a new avenue to not only dissect sex-stratified molecular mechanisms of AD but also develop sex-specific diagnostic and therapeutic strategies for AD. We integrated RNA expression datasets from the para-hippocampal gyrus of the Mount Sinai Medical Center Brain Bank (MSBB) and the prefrontal cortex from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP) to perform multiscale network analysis. The differentially expressed genes (DEGs) between AD and control, female and male, ApoE3 and ApoE4 genotype were rank-ordered based on their relevance to clinical dementia rating scale (CDR) and AD pathology (Braak stage, CERAD and plaque density). The trend analyses and gene co-expression network analysis were then performed to identify key drivers with sexually dimorphic expression patterns or differentially respond to APOE genotypes between sexes. In this study, we identified ldl receptor-related protein (lrp10), a receptor possibly involved in the uptake of ApoE and APP trafficking as the highest-ranked key driver gene candidate accounting for the sex differences in AD. Lrp10 mRNA was increased in female AD patients when compared to female controls or male AD patients. In contrast, LRP10 protein levels were reduced in AD when compared to controls, suggesting possible post-translational modifications of LRP10 in AD human brains. Gene perturbation studies in EFAD mouse hippocampal brain regions suggest that over-expression of lrp10 improved cognitive function, reduced Aβ42 and p-Tau, and increased microglial recruitment around amyloid plaques in female E4FAD mice. In contrast, down-regulation of lrp10 exacerbated cognitive impairment as well as increased brain Aβ42 and total tau levels in male E3FAD mice. These results strongly support our hypothesis that lrp10 is a causal regulator gene for AD, whose expression is strongly associated with cognition performance in sex- and APOE-specific manners. Our findings further implicate a role of lrp10 in regulating microglial function and neuro-inflammation in AD.

Sex-Specific Cross Tissue Meta-Analysis Identifies Immune Dysregulation in Women With Alzheimer's Disease.

Background: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia in the United States. In spite of evidence of females having a greater lifetime risk of developing Alzheimer’s Disease (AD) and greater apolipoprotein E4-related (APOE ε4) AD risk compared to males, molecular signatures underlying these differences remain elusive.Methods: We took a meta-analysis approach to study gene expression in the brains of 1,084 AD patients and age-matched controls and whole blood from 645 AD patients and age-matched controls in seven independent datasets. Sex-specific gene expression patterns were investigated through use of gene-based, pathway-based and network-based approaches. The ability of a sex-specific AD gene expression signature to distinguish Alzheimer’s disease from healthy controls was assessed using a linear support vector machine model. Cell type deconvolution from whole blood gene expression data was performed to identify differentially regulated cells in males and females with AD.Results: Strikingly gene-expression, network-based analysis and cell type deconvolution approaches revealed a consistent immune signature in the brain and blood of female AD patients that was absent in males. In females, network-based analysis revealed a coordinated program of gene expression involving several zinc finger nuclease genes related to Herpes simplex viral infection whose expression was modulated by the presence of the APOE ε4 allele. Interestingly, this gene expression program was missing in the brains of male AD patients. Cell type deconvolution identified an increase in neutrophils and naïve B cells and a decrease in M2 macrophages, memory B cells, and CD8+ T cells in AD samples compared to controls in females. Interestingly, among males with AD, no significant differences in immune cell proportions compared to controls were observed. Machine learning-based classification of AD using gene expression from whole blood in addition to clinical features produced an improvement in classification accuracy upon stratifying by sex, achieving an AUROC of 0.91 for females and 0.80 for males.Conclusion: These results help identify sex and APOE ε4 genotype-specific transcriptomic signatures of AD and underscore the importance of considering sex in the development of biomarkers and therapeutic strategies for AD.

Noncanonical Metabotropic Glutamate Receptor 5 Signaling in Alzheimer's Disease.

Metabotropic glutamate receptor 5 (mGluR5) is ubiquitously expressed in brain regions responsible for memory and learning. It plays a key role in modulating rapid changes in synaptic transmission and plasticity. mGluR5 supports long-term changes in synaptic strength by regulating the transcription and translation of essential synaptic proteins. β-Amyloid 42 (Aβ42) oligomers interact with a mGluR5/cellular prion protein (PrPC) complex to disrupt physiological mGluR5 signal transduction. Aberrant mGluR5 signaling and associated synaptic failure are considered an emerging pathophysiological mechanism of Alzheimer's disease (AD). Therefore, mGluR5 represents an attractive therapeutic target for AD, and recent studies continue to validate the efficacy of various mGluR5 allosteric modulators in improving memory deficits and mitigating disease pathology. However, sex-specific differences in the pharmacology of mGluR5 and activation of noncanonical signaling downstream of the receptor suggest that its utility as a therapeutic target in female AD patients needs to be reconsidered.

Sex Difference in Network Topology and Education Correlated With Sex Difference in Cognition During the Disease Process of Alzheimer.

Background: Alzheimer’s disease (AD) manifests differently in males and females. However, the neuro-mechanism and influence factors are still unknown.Objective: To explore sex differences in brain network topology during AD disease progression and its association with cognition and possible influencing factors.Methods: Resting-state functional magnetic resonance imaging (MRI) data and cognitive scores were collected from 82 AD patients (50 females), 56 amnestic mildly cognitive impaired patients (29 females), and 63 healthy controls (38 females). Global and regional topological network metrics and modular architecture were calculated. Two-way ANOVA was performed to explore group and sex interactions and their main effects. Mediation analysis was used to explore the relationship among education, inter/intra-network connectivity, and the Mini-Mental State Examination (MMSE) score.Results: Lower levels of education, lower MMSE scores, and a positive correlation between the level of education and MMSE scores were found in female AD patients (p = 0.024, r = 0.319). Significantly lower connectivity strength within the sensorimotor network, dorsal attention network, ventral attention network (VAN), and between the sensorimotor and VAN were observed in male AD patients (p = 0.006, 0.028, 0.046, and 0.013, respectively). Group and sex interactions were also found in nodal properties, mainly in the frontal lobe, temporal lobe, middle cingulum, precuneus, and postcentral gyrus. Several of the altered brain network properties were associated with cognitive behavior in male AD patients. Education regulated the MMSE score through the mediation of connection strength between the default mode and limbic networks (LN) in the patient group (aMCI and AD combined).Conclusion: Our results demonstrate that sex differences exist at the brain network level in AD. Sex differences in network topology and education are correlated with sex differences in cognition during AD progression.