No description available.

Human brain structure can be measured across the lifecourse (“in vivo”) with magnetic resonance imaging (MRI). MRI data are often used to create “atlases” and statistical models of brain structure across the lifecourse. These methods may define how brain structure changes through life and support diagnoses of increasingly common, yet still fatal, age-related neurodegenerative diseases. As diseases such as Alzheimer’s (AD) cast an ever growing shadow over our ageing population, it is vitally important to robustly define changes which are normal for age and those which are pathological. This work therefore assessed existing MR brain image data, atlases, and statistical models. These assessments led me to propose novel methods for accurately defining the distributions and boundaries of normal ageing and pathological brain structure. A systematic review found that there were fewer than 100 appropriately tested normal subjects aged ≥60 years openly available worldwide. These subjects did not have the range of MRI sequences required to effectively characterise the features of brain ageing. The majority of brain image atlases identified in this review were found to contain data from few or no subjects aged ≥60 years and were in a limited range of MRI sequences. All of these atlases were created with parametric (mean-based) statistics that require the assumptions of equal variance and Gaussian distributions. When these assumptions are not met, mean-based atlases and models may not well represent the distributions and boundaries of brain structure. I tested these assumptions and found that they were not met in whole brain, subregional, and voxel-based models of ~580 subjects from across the lifecourse (0- 90 years). I then implemented novel whole brain, subregional, and voxel-based statistics, e.g. percentile rank atlases and nonparametric effect size estimates. The equivalent parametric statistics led to errors in classification and inflated effects by up to 45% in normal ageing-AD comparisons. I conclude that more MR brain image data, age appropriate atlases, and nonparametric statistical models are needed to define the true limits of normal brain structure. Accurate definition of these limits will ultimately improve diagnoses, treatment, and outcome of neurodegenerative disease.

Introduction: Alzheimer’s disease is an irreversible brain disorder characterized by distortion of memory and other mental functions. Although, several psychometric tests are available for diagnosis of Alzheimer’s, there is a great concern about the validity of these tests at recognizing the early onset of the disease. Currently, brain magnetic resonance imaging is not commonly utilized in the diagnosis of Alzheimer’s, because researchers are still puzzled by the association of brain regions with the disease status and its progress. Moreover, MRI data tend to be of high dimensional nature requiring advanced statistical methods to accurately analyze them. In the past decade, the application of Least Absolute Shrinkage and Selection Operator (LASSO) has become increasingly popular in the analysis of high dimensional data. With LASSO, only a small number of the regression coefficients are believed to have a non-zero value, and therefore allowed to enter the model; other coefficients are while others are shrunk to zero. Aim: Determine the non-zero regression coefficients in models predicting patients’ classification (Normal, mild cognitive impairment (MCI), or Alzheimer’s) using both non-ordinal and ordinal LASSO. Methods: Pre-processed high dimensional MRI data of the Alzheimer’s Disease Neuroimaging Initiative was analyzed. Predictors of the following model were differentiated: Alzheimer’s vs. normal, Alzheimer’s vs. normal and MCI, Alzheimer’s and MCI vs. Normal. Cross-validation followed by ordinal LASSO was executed on these same sets of models. Results: Results were inconclusive. Two brain regions, frontal lobe and putamen, appeared more frequently in the models than any other region. Non-ordinal multinomial models performed better than ordinal multinomial models with higher accuracy, sensitivity, and specificity rates. It was determined that majority of the models were best suited to predict MCI status than the other two statues. Discussion: In future research, the other stages of the disease, different statistical analysis methods, such as elastic net, and larger samples sizes should be explored when using brain MRI for Alzheimer’s disease classification.

Alzheimer’s disease (AD) is the most common neurodegenerative disorder and is the main cause of dementia in the elderly population. AD is pathologically characterized by the accumulation of amyloid plaques and neurofibrillary tangles that results in neurodegeneration and loss of memory function. However, diagnosis of AD and characterization of biological mechanisms that lead to pathology and modulate risk for disease has proven to be extremely difficult. Cerebrospinal fluid (CSF) contains critical biomarkers for AD such as levels of amyloid beta (Aβ) phosphorylated-tau (p-tau), total-tau (t-tau), and neurofilament light chain (NfL). The CSF levels of these biomarkers are useful in determining AD status in a patient, but data collection can be time consuming, technically difficult, and expensive. While still subject to the limitations of obtaining CSF, cell free single stranded DNA (cfssDNA) is much cheaper and more reliably measured than these biomarkers. We investigated cfssDNA as a biomarker for AD status. We observed an association between low levels of concentration isolated from CSF as a potential biomarker for diagnosis of AD. Inflammation is a vital process in the immune system. Acute inflammation plays an essential role in the normal response to tissue injury. This inflammatory response initiates a cascade of cellular activation signals in innate immune cells resulting in increased production of proinflammatory cytokines and chemokines. These chemokines are essential to the recruitment and activation of other cells in the innate and adaptive immune system. Deviations from the normal production of these chemokines can result in disease status. Recently published work has identified genetic variants that show strong associations with AD-related chemokine levels in CSF and plasma. We attempted to characterize the biological mechanisms that underlie the reported associations between the ACKR2-V41A variant and CCL2 levels and the CCRL2-V180M variant and CCL4 levels. Our data demonstrate that the ACKR2-V41A receptor has a lower CCL2 binding affinity, scavenging efficiency, and receptor upregulation compared to ACKR2-WT. For CCRL2-V180M our data demonstrate higher binding affinity with chemerin and CCL19 than CCRL2-WT. Our data also show that while CCRL2-V180M and CCRL2-WT do not directly bind with CCL4, interactions between CCRL2-V180M and CCL19 alter the secretion of CCL4 from leukocytes. These findings provide evidence for a novel biomarker for AD diagnosis, mechanistic insights into the functional impact of common genetic variants on chemokine levels, and highlight a potential role of atypical chemokines in altering the risk for AD.

Alzheimer’s disease (AD) patients could benefit from a more effective treatment than the current FDA-approved options. Because amyloid-beta (Aβ) is thought to play a central role in AD pathogenesis, many experimental drugs attempt to reduce Aβ-induced pathology. Preventing amyloid accumulation may be a more effective strategy than clearing Aβ plaques after they form. If preventing Aβ accumulation can treat or prevent AD, then understanding Aβ primary nucleation may aid rational drug design. This study examines Aβ residue interaction networks and reports network and structural observations that may provide insight into primary nucleation. While many studies identify structural features of Aβ that promote aggregation, this study reports features that may resist primary nucleation by examining Aβ42 studies in more and less polar solvents. In Aβ42 in a less polar solvent (PDB ID: 1IYT), Val24 and Ile31 have higher betweenness and residue centrality values. This may be due to a predicted interaction between Val24 and Ile31. Residues in the central hydrophobic cluster (CHC) of Aβ40 and Aβ42 had significantly higher betweenness values compared to the average betweenness of the structures, highlighting the CHC’s reported role in oligomerization. The predicted interaction between Val24 and Ile31 may reduce the likelihood of primary nucleation of Aβ.

No description available.

An estimated 5.4 million individuals in the United States have Alzheimer’s disease, and the number is expected to rise exponentially over the next 50 years. Content analysis was used to examine the availability and content of online resources accessible through the Alzheimer’s Association and the National Institute on Aging (NIA) that addressed emotional and physical intimacy for a marital unit. The analysis resulted in ten documents from the Alzheimer’s Association’s website, seven from the NIA’s website, and four additional documents produced from external links that met these criteria. Five major themes emerged from these documents regarding the subject of emotional and physical intimacy. These categories included: (a) defining sexuality and intimacy, (b) changes that occur in the relationship due to a dementia diagnosis, (c) reasons for the change in the relationship, (d) responses to a dementia diagnosis, and (e) strategies for managing the changes due to a dementia diagnosis.

GPR50, an X-linked orphan G protein-coupled receptor (GPCR), is a risk factor for bipolar disorder (BD) in female subjects. It has been shown that GPR50 plays a part in neurite outgrowth, glucocorticoid receptor signalling and leptin signalling by interacting with major factors involved in these events. Yeast two-hybrid screens have identified multiple putative GPR50 interactors involved in neurodevelopment, stress response and apoptosis, lipid and glucose metabolism, as well as regulation of NMDA receptors and GABA transmission. Among these interactors, RTN3, RTN4, SREBP2 and SNX6 are known regulators of β-secretase (BACE1), a key enzyme in Aβ generation, myelination of the central/peripheral nerve, and neurite outgrowth/synapse formation. Preliminary data indicated that GPR50 expression significantly increased endogenous BACE1 activity in HEK293 cells, so I hypothesised that there is a functional interaction between the two. In this thesis, I investigated the relationship between GPR50 and BACE1 by identifying the effects of GPR50 on BACE1 expression and function, which may provide an explanation of GPR50’s potential association with psychiatric disorders and Alzheimer’s disease. Firstly, studies on expression levels revealed that when GPR50 was over-expressed, BACE1 protein expression was up-regulated in SH-SY5Y cells, but down-regulated in HEK293 cells, suggesting a differentiated regulative system between cell lines. Then I confirmed the physical association between endogenous GPR50 and BACE1 in HEK293 cells by co-localisation and co-immunoprecipitation studies. Their putative interaction sites were located at the plasma membrane and the filopodia/lamellipodia-like structures in HEK293 cells, and at the neurites in mouse primary neuronal cells. Subcellular fractionation of adult mouse brain revealed that endogenous Gpr50 and Bace1 were co-fractionated in the presynaptic vesicles. Secondly, I showed that, in contrast to HEK293 cells, GPR50 overexpression had no effects on β-secretase activity in mouse primary cortical neurons. However, the BD-associated variant GPR50del significantly decreased β-secretase activity compared to the more common variant GPR50, and showed a trend of diminishing β-secretase activity compared to the control condition. Subcellular fractionation experiments showed that in HEK293 cells, there was an increased ratio of mature BACE1 against immature BACE1 localised in the plasma membrane fractions, indicating a role in regulation of BACE1 trafficking to one of its putative activity sites; whereas in mouse primary cortical neurons, GPR50del increased co-fractionation of immature Bace1 with endoplasmic reticulum (ER) marker calreticulin, thus potentially retarding the maturation of Bace1. Importantly, the regulative trend of GPR50/GPR50del on β-secretase activity is cell line-specific and is highly correlated to their effects on β-secretase intracellular distribution. Thirdly, I found that the mRNA levels of human GPR50 and BACE1 were negatively correlated in the dorsolateral prefrontal cortex of female subjects sampled after birth. Mouse Gpr50 and Bace1 mRNA levels were negatively correlated across the telencephalon regions, and had a trend of negative correlation across the hypothalamic regions. Co-localisation of the two proteins was detected in multiple mouse brain regions, with the strongest co-localised signals occurring in CA2 pyramidal neurons, arcuate hypothalamic nucleus and dorsomedial nucleus of the hypothalamus. Finally, preliminary experiments in Alzheimer’s disease model TgSwDI mice, suggested that the expression level of Gpr50 in layer V of the entorhinal cortex was positively correlated with Aβ deposition. Decreased Gpr50 expression was identified in the hippocampus of 9 months transgenic animals compared with age-matched controls. This indicates that Gpr50 expression might be altered in this mouse model co-ordinately with Aβ deposition. The findings in this thesis provide further evidence of GPR50’s correlation to psychiatric illnesses and its interaction with enzyme BACE1 highlights a potential link to neurodegenerative disease.

Alzheimer’s disease (AD), the most common form of dementia in the elderly, is a global issue affecting about 24 million individuals. Because AD is a systemic pathology, dementia is not the only leading factor contributing to loss of independence in AD patients. AD may also impair skeletal muscle metabolism and function. Creatine (CR) supplementation may enhance skeletal muscle hypertrophy/mass and function in sarcopenia and muscular dystrophies, but has yet to be studied in AD. This study examined the effect of oral CR on muscle metabolism in a triple-transgenic (3xTg) AD mouse model. Twenty-four, 3×Tg AD mice (~8 month-old) were randomly assigned to control (CON) or CR (3% w/w) diet. Bodyweights and feed intakes were measured throughout the 8-week study. Lower limb (quadriceps muscle; QM and gastrocnemius; GM) and upper limb muscles (triceps; TM) were collected to analyze levels of CR, total protein, DNA, RNA, amino acids (AA), adenosine triphosphate (ATP), adenosine diphosphate (ADP), total and phosphorylated p70 ribosomal S6 kinase (p70S6K). Data (mean ± SEM) were assessed by analysis of variance (ANOVA) and Fisher’s least significant difference (LSD) post hoc test. In comparison to the CON group, CR supplementation increased CR content in both GM (p=0.002) and QM (p=0.037), with higher (p=0.032) ATP/ADP ratio in CR in comparison with CON in QM. A higher protein concentration (p<0.0001) was notable in GM of CR supplemented group vs. CON. Total branched-chain AA levels in QM increased 2-fold (p< 0.0001) in CR groups. Additionally, CR resulted in a higher (p<0.05) protein/DNA ratio; an index of muscle cell size, in both QM and GM for CR groups. The index of cell capacity for protein synthesis (RNA/DNA ratio) in GM was also higher (p=0.001) in CR groups. However, phosphorylation (activation) level of p70S6K, an integral component in protein synthesis signalling pathway, did not show any significant differences in female (p=0.161) and male (p=0.292) CR supplemented groups compared with CON. To conclude, CR supplementation is capable of inducing muscle hypertrophy/growth parameters in the 3×Tg AD mouse model, thereby enhancing protein synthesis capacity in skeletal muscles, thus possibly promoting muscle function in AD. / May 2016

The earliest stage of Alzheimer’s disease (AD) pathology begins in one of the main components of the olfactory pathway, the entorhinal cortex, making deficits in smell a potential prospective biomarker for the early detection of AD. This study contributes to the field with a reproduction and extension of work by Wilson, Arnold, Schneider, Boyle, Buchman, and Bennett (2009). A sample of 1089 individuals (M=78.4 years), more than double the data available in 2009, completed annual assessments of olfactory functioning, and cognitive functioning for up to 18 years with brain donation at death. Mixed effects models conditioned on demographics estimated between and within-person effects in olfactory functioning and episodic memory (EM). After successful reproduction of Wilson et al. (2009), addition of AD pathology (ADP) demonstrated that both ADP and olfaction were significantly related to EM at baseline. Higher ADP at autopsy was significantly related to faster declines in olfaction, as well as more rapid declines in EM. Higher olfactory scores were associated with higher EM scores and a model for EM with olfaction as time-varying covariate indicated that at a given occasion, individuals with higher olfactory scores also have higher EM scores. These results align with the hypotheses that difficulty in identifying odors predicts development of cognitive impairment; increased levels of AD pathology are related to both decreased EM at baseline and faster declines, as well as faster rates of decline in olfaction; and olfaction and cognition are travelling together over time. / Graduate / 2018-06-01 / 0766 / 0633 / jknight@uvic.ca