Alzheimer’s disease (AD) is a complex neurodegenerative disease characterized by progressive memory loss and caused by a combination of genetic, environmental, and lifestyle factors. AD susceptibility is highly heritable at 58-79%, but only about one third of the AD genetic component is accounted for by common variants discovered through genome-wide association studies (GWAS). Rare variants may contribute to some of the unexplained heritability of AD and have been demonstrated to contribute to large gene expression changes across tissues, but conventional analytical approaches pose challenges because of low statistical power even for large sample sizes. Recent studies have demonstrated by expression quantitative trait locus (eQTL) analysis that changes in gene expression could play a key role in the pathogenesis of AD. However, regulation of gene expression has been shown to be context-specific (e.g., tissue and cell-types), motivating a context dependent approach to achieve more precise and statistically significant associations. To address these issues, I applied a strategy to identify new AD risk or protective rare variants by examining mutations occurring only in cases or only controls, observing that different mutations in the same gene or variable dose of a mutation may result in distinct dementias. I also evaluated the impact of rare variation on expression at the gene and gene pathway levels in blood and brain tissue, further strengthening the rare variant findings with functional evidence and finding evidence for a large immune and inflammatory component to AD. Lastly, I identified cell-type specific eQTLs in blood and brain tissue to explain underlying genetic associations of common variants in AD, and also discovered additional evidence for the role of myeloid cells in AD risk and potential novel blood and brain AD biomarkers. Collectively, these findings further explain the genetic basis of AD risk and provide insight about mechanisms leading to this disorder. / 2022-01-21T00:00:00Z

BACKGROUND: Early detection of individuals at risk for converting to Alzheimer’s disease (AD) can potentially lead to more efficient treatment and better disease management. A well-known approach has aimed at identifying individuals at the prodromal stage of dementia; namely, Mild Cognitive Impairment (MCI). Past studies showed that MCI subjects often have accelerated rates of conversion to AD, or to other types of dementia compared to healthy controls (HCs). However, with more investigations of the MCI population, it became evident that a high level of heterogeneity exists within this group: many remain clinically stable even after 10 years. MCI subtypes defined by the conventional classification criteria showed inconsistent results for determining an individual's risk of AD. As another approach, neuroimaging techniques such as magnetic resonance imaging (MRI) are able to successfully identify neurological changes during early AD. MRI markers including morphological, connectional and abnormal signal patterns in the brain have been shown to have good sensitivity for classifying AD. Based on these findings, recent studies started implementing these imaging markers to create computer-aided classification models for predicting the risk of conversion to AD. Most of these studies enrolled MCI subjects who remained stable or converted to AD within 3 years, and generated computer-aided classification models to predict conversion using various imaging markers and clinical data. To our knowledge, no classification models proposed achieved an accuracy of higher than 80% for predicting MCI-AD conversion earlier than 3 years with only using structural MRI features. In this paper, we tested the prediction range beyond 3 years, and suggested new candidate imaging measures for earlier prediction. METHODS: The subjects included in the current study are n=51 MCI non-converter, n=157 MCI converter (115 fast converters and 42 slow converters) and n=38 AD, selected from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. Using subjects' baseline T1-weighted MRI scans, we combined conventional morphometric measures (e.g. cortical thickness, surface area, volume, etc.) with novel intensity measures to differentiate MCI converters from non-converters. We additionally applied a machine learning approach to classify MCI subgroups by combining features in multiple measurement domains. RESULTS: Based on group comparison using independent t-test, we found that while MCI fast converters (conversion within 0-2 years) were highly distinct from MCI non-converters across many cortical and subcortical regions, MCI slow converters (conversion within 3-5 years) demonstrated more focal differences from MCI non-converters mainly in the temporal regions and hippocampal subfields. We identified unique imaging features associated with each converter group and had improved classification performance on both MCI converter groups by adding those markers. The best performing classifiers combined conventional imaging features, novel intensity features and neuropsychological features. For our best performing classification models, we were able to classify MCI fast converters (0-2 years) from non-converter with an average accuracy of 86.1%, sensitivity of 85.5%, and specificity of 89.8%, and to classify MCI slow converters (3-5 years) from non-converters with an accuracy of 80.5%, sensitivity of 75.7%, and specificity of 82.3%. CONCLUSION: Our results demonstrated the potential of the suggested approach for predicting the conversion from MCI to AD at an even earlier time point (3-5 years) before the onset of AD. The combination of standard morphometric features and proposed novel intensity features improved the sensitivity of using T1-weighted MRI for describing the heterogeneity between MCI subgroups.

Alzheimers sjukdom (AD) är den vanligaste formen av demens och påverkar miljontals människor världen över. Förekomst av senil plack och tangles in hjärnan hos personer med AD har varit ett känt faktum sedan början av 1900-talet. Flera studier gjorda under de senaste åren har påvisat en kopplling mellan AD och Diabetes, då försämrad insulin-signalering och nedbrytning av glukos påverkar flera av de molekylära förändringar som uppvisas i AD. I det här projektet använde vi oss av immunofluorescence för att studera uttryck och lokalisering av två transkriptionsfaktorer involverade i nedbrytning av glukos; NPAS3 och RFX3, i hjärnbarken hos patienter med AD, Lewykroppsdemens (DLB) hälsosamma kontroller. Intensiteten på infärgningen av NPAS3 och RFX3 visade inte mängden protein och kvantifierades med algoritmer skrivna i ImageJ. Infärgningen av NPAS3 och RFX3 visade inte på någon signifikant skilland mellan de tre kohorterna och för att förstå mer om deras roll i nedbrytningen av glukos och om det kan påverka AD, måste både infärgnings- och kvantifieringsprocesserna använda i detta projekt optimeras. / Alzheimer's disease (AD) is the most common form of senile dementia. affecting millions o people worldwide. Beta amyloid plaques and neurofibrillary tangles are known to be part of AD pathology since the early nineteen hundreds. In recent years evidence showing that impairments in glucose metabolism can initiate plaque- and tangle formation, as well as several of the other degenerative mechanisms taking place in the AD brain, suggests a potential connection between Alzheimer's disease and Diabetes. Here we used immunofluorescence to study expression of two transcription factors involved in regulation of glucose metabolism; NPAS3 and RFX3. Expression of NPAS3 and RFX3 was investigated in temporal cortex from patients with AD, Dementia with Lewy bodies (DLB) and non-demented age matched controls. The intensity of the immunofluorescent stainings was assumed to be proportional to the amount of stained protein and was quantified in ImageJ. This explorative study did not reveal a significant difference between groups and staining- an quantification procedures would have to be optimized in order to get a clearer understanding about the role of NPAS3 and RFX3 in glucose metabolism, and if that could affect the progression of AD.

Indiana University-Purdue University Indianapolis (IUPUI) / Today, Alzheimer’s is a devastating disease that affects more than 46.8 million people worldwide. Caring for people with AD is stressful and emotionally draining for both family members and healthcare providers and would be exacerbated by the breakdown in communication. While communication challenges can take many forms, one understudied area in AD patient-provider communication is how gender role might affect the outcomes and perceived feelings during interaction. Without knowledge and attentiveness of how gender may affect patient-provider communication, healthcare providers may become more frustrated in their attempts to apply unadjusted skills, which can cause further breakdown and stress. This study is to explore how gender might be a role affecting caregiving communication within the context of Alzheimer’s. Eleven participants were recruited to have a semi-structured interview through online flyers. The findings from this study yield broad suggestions for future work within the field of Alzheimer’s communication research and specific suggestions for designing the communication training.

The diagnostic lesions of neurodegenerative tauopathies, such as chronic traumatic encephalopathy (CTE) and Alzheimer’s disease (AD), are located in the cortex, however, white matter pathology is a contributing factor to neurodegeneration. At all stages of disease, white matter axonal and glial morphological abnormalities are present in CTE. Similarly, white matter changes may emerge before cortical pathology in AD. White matter irregularities bear functional consequences, as they are associated to some of the most common and onerous symptoms of these diseases, like cognitive deficits and depression. Individuals with AD present with both reduced white matter integrity and cognitive symptoms starting early in disease progression. In CTE, which is triggered by repetitive head impacts (RHI), individuals are particularly vulnerable to white matter damage as RHI exposure alone is sufficient to injure white matter tracts and induce depression symptoms. In this dissertation, I investigated the cellular and molecular presentation of white matter glial cells, including astrocytes, oligodendrocytes (OLs), and microglia in CTE and AD as compared to controls. To investigate white matter pathology, I examined glial cells on a cellular level. Neuropathologically-verified CTE samples were compared to RHI-experienced controls, with both groups containing samples with and without depressed mood. CTE with depressed mood had reduced myelin and increased neuroinflammatory peripheral cells compared to non-depressed CTE and contained increased numbers of microglia compared to non-depressed CTE and control samples. Using single-nucleus transcriptomics in neuropathologically-verified CTE samples compared to matched RHI-naïve controls, OL loss, iron aggregates, OL iron trafficking dysregulation, and two distinct astrocyte subpopulations were detected in CTE white matter. AD white matter, compared to the same control samples in the same brain region, was also depleted of OLs by single-nucleus transcriptomics. However, OLs did not demonstrate iron-related transcriptional profile like those in CTE and, in further contrast, displayed increased numbers of microglia and astrocytes. Together, these findings implicate previously uncharacterized white matter glia in the neurodegenerative process of CTE and AD and further elucidate the etiology of neurodegeneration-related symptoms in CTE. These findings may aid in the development of therapeutics targeting glial contributions to the pathologic processes of both CTE and AD.

Alzheimer’s disease is characterized by the formation of two major pathological hallmarks: amyloid plaques and neurofibrillary tangles. Although there have been many studies to understand the role of microglia in Alzheimer’s disease, it is not yet known how microglia can promote disease progression while actively phagocytosing amyloid plaques or phosphorylated tau (p-tau). Through stereotaxic injection of adeno-associated virus expressing mutant P301L tau (AAV-P301L-tau) into the medial entorhinal cortex (MEC) of both wild-type (WT) and APPNL-G-F mice, we demonstrate how amyloid plaques exacerbate p-tau propagation to the granule cell layer (GCL) of the hippocampus. However, in mice receiving the colony-stimulating factor 1 receptor inhibitor (PLX5622), ~95% of microglia were depleted, which dramatically reduced p-tau propagation to the GCL. Although microglia depletion curtailed p-tau propagation, it also led to reduced plaque compaction and an increase in overall amyloid-beta (Aβ) plaque presence. Additionally, we found microglia depletion resulted in greater p-tau aggregation in dystrophic neurites surrounding amyloid plaques. We investigated neurodegenerative microglia (MGnD), which are activated in response to amyloid plaques, for their propensity to release extracellular vesicles in comparison to homeostatic microglia. We discovered that MGnD, identified by Clec7a or Mac2 staining, strongly express Tumor susceptibility gene 101 (Tsg101), which is an ESCRT-1 protein and a marker for extracellular vesicles (EVs). To further investigate EV release and MGnD, a novel lentivirus expressing fluorescent mEmerald conjugated to CD9 (mE-CD9) was constructed and injected into the MEC of both WT and APPNL-G-F mice which allowed for visualization of mE-CD9+ puncta around individual microglia. CD9 is a tetraspanin and also a marker for EVs. We observed that the number of mEmerald+ particles surrounding MGnD was three-fold higher compared to non-diseased, homeostatic microglia. Sequential injection of mE-CD9 and AAV-P301L-tau into the MEC revealed that microglia-derived EVs encapsulate pathologic p-tau, which is augmented by the MGnD phenotype. Taken together, these data provide strong evidence that MGnD exhibit increased secretion of tau-containing EVs, providing a possible mechanism for how amyloid deposition indirectly exacerbates tau propagation.

Alzheimer’s Disease is a growing public health problem, with the number of Americans suffering from the disease projected to more than double from 5.8 million today to 13.8 million in 2050. While there is still no cure for Alzheimer’s Disease, a preventative strategy may mitigate its cost to society in the future. Previous studies have shown an ameliorative effect of perinatal choline supplementation on amyloidosis in the hippocampus of APP.PS1 mice. In this study, we test the effects of perinatal choline supplementation on the APP.NLGF strain of mice – which uses a gene knock-in strategy to avoid the non-physiologic overexpression of amyloid precursor protein and better recapitulate the disease in humans. When compared to APP.NLGF mice raised on a control diet, the perinatal choline supplemented APP.NLGF mice exhibited: i) an amelioration of learning and memory deficits in 9- and 12-months old mice as measured by contextual fear conditioning, ii) reduced amyloidosis in the cortex of 9- and 12-months old mice, and iii) an age- and brain region-dependent response to perinatal choline supplementation. These results suggest that increasing the dietary intake of choline during pregnancy may protect the offspring from AD-associated cognitive decline and amyloidosis.

Previous studies showed that memantine inhibits tau hyperphosphorylation in vitro. In this study, phosphorylated tau (P-tau) and total tau (T-tau) were measured before and after 6 month treatment with memantine in 12 subjects ranging from normal cognition with subjective memory complaints, through mild cognitive impairment to mild Alzheimer's disease. Thirteen non-treated individuals served as controls. Treatment was associated with a reduction of P-tau in subjects with normal cognition. No treatment effects were seen among impaired individuals, suggesting that longer treatment time may be necessary to achieve biomarker effect in this group.

Small-molecule inhibitors of tau fibrillization are under investigation as tools for interrogating the tau aggregation pathway and as potential therapeutic agents for Alzheimer's disease. Established inhibitors include thiacarbocyanine dyes, which can inhibit recombinant tau fibrillization in the presence of anionic surfactant aggregation inducers. In an effort to increase inhibitory potency, a cyclic bis-thiacarbocyanine molecule containing two thiacarbocyanine moieties was synthesized and characterized with respect to tau fibrillization inhibitory activity by electron microscopy and ligand aggregation state by absorbance spectroscopy. Results showed that the inhibitory activity of the bis-thiacarbocyanine was qualitatively similar to a monomeric cyanine dye, but was more potent with 50% inhibition achieved at ∼80 nM concentration. At all concentrations tested in aqueous solution, the bis-thiacarbocyanine collapsed to form a closed clamshell structure. However, the presence of tau protein selectively stabilized the open conformation. These results suggest that the inhibitory activity of bis-thiacarbocyanine results from multivalency, and reveal a route to more potent tau aggregation inhibitors.

Objective: The aims of this project were to (a) perform a systematic review and meta-analysis of the associations between multiple neurological disorders (or neurological diseases) and potential influencing factors, including the association between fine particulate matter (PM 2.5) and intestinal dysfunction, and (b) investigate the mechanisms and toxicological effects of PM 2.5 exposure in the brain and intestines using a mouse model of Alzheimer's disease (AD). Design: A systematic review and meta-analysis was conducted to assess the risks of PM 2.5 exposure, as manifested by the incidence of exposure-associate neurological disorders or intestinal dysfunction. An APP/PS1 transgenic mouse model for AD was used to study the brain damage resulting from PM 2.5 exposure, and the miRNA/mRNA regulatory mechanisms contributing to this damage. The inflammatory injuries and bacterial community changes in the intestines of AD mice exposed to PM 2.5 were also investigated. Data sources: Articles for systematic review and meta-analysis were obtained by searching PubMed and China National Knowledge Infrastructure (CNKI), which were published for more than ten years. Animal experiments were conducted at Shanxi University of Taiyuan in China, and toxicological tests were performed according to the stipulated methods and protocols. Review and experimental methods: Data on the risks of incidence of neurological disorders associated with the environmental factor (PM 2.5) and biological factors (intestinal disorders and bacteria) were obtained, and random- or fixed-effects models (depending on the I 2 value) were used to pool the odds ratios (OR) with the 95% confidence intervals (CI) from individual studies. In the animal experiments, mice were divided into four groups of five animals per group, as follows: normal control mice in filtered air, AD mice in filtered air, normal control mice in PM 2.5 air, and AD mice in PM 2.5 air. PM 2.5 mice were exposed to ambient PM 2.5 in a whole-body inhalation exposure device for 8 weeks in Taiyuan, China. Well-established methods were used to explore the toxicological mechanisms by which PM 2.5 exacerbated brain damage in AD mice, namely open-field testing, enzyme-linked immunosorbent assay (ELISA), real-time quantitative RT-PCR, hematoxylin-eosin (HE) staining, and transmission electron microscopy (TEM). Brain damage and related biomarkers in the brains were measured, and miRNA and mRNA profiles were detected using high-throughput sequencing methods. The signaling pathways of miRNAs or mRNAs were predicted and summarized, and specific miRNAs and mRNAs were screened to explore the possible regulatory mechanisms of PM 2.5 -induced brain damage in AD mice. Intestinal and fecal samples from these mice were also subjected to 16S rRNA gene sequencing. HE staining, ELISA, and metagenome bacterial diversity analyses were performed to investigate the effects of PM 2.5 inhalation on intestinal tissue damage, inflammatory responses, and changes of bacterial diversity and communities in AD mice. Results: Long-term PM 2.5 exposure has been associated with increased risks of stroke, dementia, AD, autism spectrum disorder (ASD), and Parkinson's disease (PD) in humans, with the risks of ischemic and hemorrhagic stroke being higher than that of stroke in general. Furthermore, a relatively higher risk of stroke has been observed in heavily polluted countries compared to less polluted countries. It is known that some intestinal disorders and related problems such as constipation, inflammatory bowel disease, irritable bowel syndrome, small intestinal bacterial overgrowth, and diarrhea significantly increase the risks of developing AD or PD. For example, the risk estimates of Helicobacter pylori infection were significantly associated with AD and PD. From another angle, preliminary animal experimental results showed that PM 2.5 promoted brain morphological damage and decreased spatial exploration ability in AD mice, and was concomitant with increases in the concentrations of amyloid-β-42, acetylcholinesterase, tumor necrosis factor-α, and interleukin-6 and decreases in the concentrations of choline acetyltransferase. High-throughput sequencing and bioinformatics analyses revealed that miRNAs and mRNA had differential expression profiles subsequent to PM 2.5 exposure, which suggested that these species are involved in the molecular regulatory mechanisms and possible signal pathways of PM 2.5 -aggravated brain injury in AD mice. These PM 2.5 -aggravated brain injuries were correlated with pathological intestinal injury, inflammatory responses, and changes in bacterial diversity in the intestines and feces of PM 2.5 -exposed AD mice, and decreases in predominant bacteria were identified. These data will assist in delineating the ability of PM 2.5 exposure to induce pathological changes in the brain and gut tissue via the brain-gut axis and thereby aggravate AD. Conclusions: A systematic review and meta-analysis showed that there is a significant association between PM 2.5 exposure and the occurrence of stroke, dementia, AD, ASD, and PD, and a strong association between intestinal disorders and the presence of certain bacteria and the development of AD and PD. PM 2.5 (environmental factors) and intestinal disorders accompanied by changes in bacterial diversity (internal biological factors) appeared to be the two most important factors that increase the risk of developing neurological disorders. Experimental animal data showed that PM 2.5 potently damaged the brain and intestines of AD mice, and that the toxicological mechanisms of this PM 2.5 -mediated brain injury led to morphological changes, inflammation, and perturbation of miRNA/mRNA regulation in the brain. These data suggest that PM 2.5 inhalation also have modulatory effects on the abundance and diversity of intestinal bacteria in AD mice. The findings of this study have clarified positive relationships between environmental and biological factors and neurological disorders and have elucidated the potential mechanisms by which PM 2.5 may mediate the initiation or exacerbation of AD