Your search for: 'author:("Salvado, Olivier")' has returned 15 results. (0.044s) Save search

Authors: Fazlollahi, Amir | Raniga, Parnesh | Bourgeat, Pierrick | Yates, Paul | Bush, Ashley I. | Salvado, Olivier | Ayton, Scott

Article Type: Research Article

Abstract: Background: Cortical iron accumulation has been reported as a pathological feature of Alzheimer’s disease (AD). The cause of cortical iron elevation in AD is unknown but may be contributed by hemosiderin deposits in cerebral microbleeds that frequently occur in this disease. Objective: To investigate the impact of cerebral microbleeds (which are more frequent in AD) on the magnetic susceptibility of the surrounding brain tissue. Methods: 32 MRI scans from the Australian Imaging, Biomarker and Lifestyle (AIBL) study were found to have cerebral microbleeds by manual assessment of susceptibility weighted images. Quantitative susceptibility mapping (QSM; an MRI technique that is sensitive …to iron) was used to estimate iron content in the tissue surrounding the microbleed in four concentric radii. Furthermore, the mirror regions on the contralateral hemisphere were also demarcated. A simulation analysis was conducted to investigate the effect of QSM imaging on cerebral microbleeds with varying sizes. Results: 77 microbleeds were identified from the available scans. The immediate proximal region to the cerebral microbleeds had enhanced tissue susceptibility (∼0.02 PPM), but importantly, this did not extend beyond one voxel radius. This finding with in vivo data was also replicated in a simulation study. However, the presence of microbleeds could lead to over-estimation of tissue QSM in unsupervised quantification, therefore processing methods to avoid this artefact without the need for their manual identification are proposed. Conclusion: The local changes in susceptibility due to microbleeds outside the focal lesion are restricted to 1 voxel and may be explained by partial voluming artefacts caused by limited imaging resolution. The susceptibly change induced by the microbleed is a relatively small proportion of tissue and could not account for regional iron changes observed in AD cortex. Show more

Keywords: Alzheimer’s disease, cerebral microbleeds, iron, magnetic resonance imaging, quantitative susceptibility mapping

DOI: 10.3233/JAD-200076

Citation: Journal of Alzheimer's Disease, vol. 76, no. 2, pp. 571-577, 2020

Authors: Watt, Andrew D. | Perez, Keyla A. | Faux, Noel G. | Pike, Kerryn E. | Rowe, Christopher C. | Bourgeat, Pierrick | Salvado, Olivier | Masters, Colin L. | Villemagne, Victor L. | Barnham, Kevin J.

Article Type: Research Article

Abstract: Diagnostic measures for Alzheimer's disease (AD) commonly rely on evaluating the levels of amyloid-β (Aβ) peptides within the cerebrospinal fluid (CSF) of affected individuals. These levels are often combined with levels of an additional non-Aβ marker to increase predictive accuracy. Recent efforts to overcome the invasive nature of CSF collection led to the observation of Aβ species within the blood cellular fraction, however, little is known of what additional biomarkers may be found in this membranous fraction. The current study aimed to undertake a discovery-based proteomic investigation of the blood cellular fraction from AD patients (n = 18) and healthy …controls (HC; n = 15) using copper immobilized metal affinity capture and Surface Enhanced Laser Desorption/Ionisation Time-Of-Flight Mass Spectrometry. Three candidate biomarkers were observed which could differentiate AD patients from HC (ROC AUC > 0.8). Bivariate pairwise comparisons revealed significant correlations between these markers and measures of AD severity including; MMSE, composite memory, brain amyloid burden, and hippocampal volume. A partial least squares regression model was generated using the three candidate markers along with blood levels of Aβ. This model was able to distinguish AD from HC with high specificity (90%) and sensitivity (77%) and was able to separate individuals with mild cognitive impairment (MCI) who converted to AD from MCI non-converters. While requiring further characterization, these candidate biomarkers reaffirm the potential efficacy of blood-based investigations into neurodegenerative conditions. Furthermore, the findings indicate that the incorporation of non-amyloid markers into predictive models, function to increase the accuracy of the diagnostic potential of Aβ. Show more

Keywords: Amyloid-β, biomarkers, blood, copper, diagnostics, SELDI-TOF-MS

DOI: 10.3233/JAD-2010-101722

Citation: Journal of Alzheimer's Disease, vol. 24, no. 1, pp. 47-59, 2011

Authors: Yassi, Nawaf | Hilal, Saima | Xia, Ying | Lim, Yen Ying | Watson, Rosie | Kuijf, Hugo | Fowler, Christopher | Yates, Paul | Maruff, Paul | Martins, Ralph | Ames, David | Chen, Christopher | Rowe, Christopher C. | Villemagne, Victor L. | Salvado, Olivier | Desmond, Patricia M. | Masters, Colin L.

Article Type: Research Article

Abstract: Background: Quantifying the contribution of cerebrovascular disease to the clinical and pathological profile of Alzheimer’s disease is challenging. Objective: We aimed to determine the influence of cerebrovascular disease, amyloid-β (Aβ), and their comorbidity on cognitive decline, hippocampal atrophy, and Aβ deposition, by evaluating data from the Australian Imaging, Biomarker and Lifestyle Study of Ageing. Methods: Two-hundred and eighteen participants underwent Aβ PET, MRI, and cognitive assessment at 18-month intervals for up to 90 months. Aβ status was determined on baseline PET. Participants were also classified as V+ on baseline MRI if they had≥1 large cortical infarcts, subcortical infarcts, or cortical …cerebral microinfarcts; or white matter hyperintensity volume greater than the 90th percentile of healthy controls. Linear mixed models were conducted comparing slopes of change in cognition, hippocampal volume, and Aβ load between the four resultant groups. Results: Mean age at baseline was 74 years (range 59–96). One-hundred and fifteen participants were cognitively normal, 54 had mild cognitive impairment, and 49 had Alzheimer’s disease. Compared to the Aβ-/V- group, the Aβ+/V- and Aβ+/V+ groups showed significantly faster cognitive decline and hippocampal atrophy over 90 months. V + status was associated with greater cognitive decline (Cohen’s d  = 0.85, p  < 0.001) and hippocampal atrophy (d  = 2.05, p  < 0.001) in the Aβ+ group but not in the Aβ- group. V+ status was not associated with Aβ accumulation in any group. Conclusion: Comorbidity of cerebrovascular disease and Aβ was associated with cognitive decline and neurodegeneration. Cerebrovascular disease was not associated with the rate of Aβ accumulation. Show more

Keywords: Alzheimer’s disease, cerebrovascular disease, magnetic resonance imaging, mild cognitive impairment, positron emission tomography, stroke

DOI: 10.3233/JAD-191028

Citation: Journal of Alzheimer's Disease, vol. 73, no. 3, pp. 897-907, 2020

Authors: Gardener, Samantha L. | Sohrabi, Hamid R. | Shen, Kai-kai | Rainey-Smith, Stephanie R. | Weinborn, Michael | Bates, Kristyn A. | Shah, Tejal | Foster, Jonathan K. | Lenzo, Nat | Salvado, Olivier | Laske, Christoph | Laws, Simon M. | Taddei, Kevin | Verdile, Giuseppe | Martins, Ralph N.

Article Type: Research Article

Abstract: Increasing evidence suggests that Alzheimer’s disease (AD) sufferers show region-specific reductions in cerebral glucose metabolism, as measured by [18 F]-fluoro-2-deoxyglucose positron emission tomography (18 F-FDG PET). We investigated preclinical disease stage by cross-sectionally examining the association between global cognition, verbal and visual memory, and 18 F-FDG PET standardized uptake value ratio (SUVR) in 43 healthy control individuals, subsequently focusing on differences between subjective memory complainers and non-memory complainers. The 18 F-FDG PET regions of interest investigated include the hippocampus, amygdala, posterior cingulate, superior parietal, entorhinal cortices, frontal cortex, temporal cortex, and inferior parietal region. In the cohort as a whole, …verbal logical memory immediate recall was positively associated with 18 F-FDG PET SUVR in both the left hippocampus and right amygdala. There were no associations observed between global cognition, delayed recall in logical memory, or visual reproduction and 18 F-FDG PET SUVR. Following stratification of the cohort into subjective memory complainers and non-complainers, verbal logical memory immediate recall was positively associated with 18 F-FDG PET SUVR in the right amygdala in those with subjective memory complaints. There were no significant associations observed in non-memory complainers between 18 F-FDG PET SUVR in regions of interest and cognitive performance. We observed subjective memory complaint-specific associations between 18 F-FDG PET SUVR and immediate verbal memory performance in our cohort, however found no associations between delayed recall of verbal memory performance or visual memory performance. It is here argued that the neural mechanisms underlying verbal and visual memory performance may in fact differ in their pathways, and the characteristic reduction of 18 F-FDG PET SUVR observed in this and previous studies likely reflects the pathophysiological changes in specific brain regions that occur in preclinical AD. Show more

Keywords: Brain glucose metabolism, cognition, 18F-FDG PET, subjective memory complaints, verbal memory, visual memory

DOI: 10.3233/JAD-151084

Citation: Journal of Alzheimer's Disease, vol. 52, no. 2, pp. 661-672, 2016

Authors: Lim, Yen Ying | Williamson, Robert | Laws, Simon M. | Villemagne, Victor L. | Bourgeat, Pierrick | Fowler, Christopher | Rainey-Smith, Stephanie | Salvado, Olivier | Martins, Ralph N. | Rowe, Christopher C. | Masters, Colin L. | Maruff, Paul | for the AIBL Research Group

Article Type: Research Article

Abstract: Background: The association between the apolipoprotein E (APOE ) ɛ 4 allele and high risk of developing Alzheimer’s disease (AD) dementia before the age of 80 has been recognized for over 30 years. However, the timing and mode of action of APOE is not understood, nor has there been a detailed analysis of the effect of APOE genotype on memory, hippocampal volume, and amyloid-β (Aβ) levels in cognitively normal adults. Objective: Examine the effect of APOE allelic genotype on the relationship between Aβ levels, hippocampal volume, and memory in cognitively normal adults. Methods: This is a cross-sectional study of 989 …cognitively normal older adults enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study, all of whom underwent APOE genotyping and memory assessment. A subset of this group underwent PET neuroimaging for Aβ (n  = 585) and MRI for hippocampal volume (n  = 303). Results: APOE ɛ 4 homozygotes (ɛ 4/ɛ 4) showed significantly worse episodic memory and higher Aβ levels than ɛ 4 heterozygotes. The relationship between increasing Aβ levels and worse episodic memory was significant for ɛ 3 homozygotes (ɛ 3/ɛ 3), ɛ 4 heterozygotes, and strongest for ɛ 4 homozygotes. There were no differences in hippocampal volume between APOE groups; the relationship between smaller hippocampal volume and worse episodic memory was significant only for ɛ 4 homozygotes. Conclusion: APOE acts in a co-dominant fashion on Aβ levels, episodic memory, and hippocampal volume in cognitively normal older adults. APOE ɛ 4 is central to the events that lead to AD in cognitively normal older adults, likely through a quantitative role in the disruption of Aβ clearance. Show more

Keywords: Alzheimer’s disease, amyloid, apolipoprotein E, hippocampal volume, memory, mild cognitive impairment

DOI: 10.3233/JAD-170072

Citation: Journal of Alzheimer's Disease, vol. 58, no. 4, pp. 1293-1302, 2017

Authors: Dang, Christa | Harrington, Karra D. | Lim, Yen Ying | Ames, David | Hassenstab, Jason | Laws, Simon M. | Yassi, Nawaf | Hickey, Martha | Rainey-Smith, Stephanie | Robertson, Joanne | Sohrabi, Hamid R. | Salvado, Olivier | Weinborn, Michael | Villemagne, Victor L. | Rowe, Christopher C. | Masters, Colin L. | Maruff, Paul | for the AIBL Research Group

Article Type: Research Article

Abstract: Background: Preclinical Alzheimer’s disease (AD) is defined by cerebral amyloid-β positivity (Aβ+) in cognitively normal (CN) older adults. Objective: To estimate the risk of progression to the symptomatic stages of AD due to PET Aβ+ and the extent that progression was influenced by other demographic, genetic, and clinical characteristics in a large prospective study. Methods: Fine-Gray subdistribution modeling was used to examine the risk of progression from CN to MCI/dementia due to Aβ+, APOE ɛ 4 carriage, and their interaction in the Australian Imaging, Biomarkers and Lifestyle (AIBL) flagship study of aging CN cohort (n  = 599) over 8 years. Results: 17.7% …Aβ+ and 8.1% Aβ–progressed over 8 years (OR: 2.43). Risk of progression for Aβ+ was 65–104% greater than Aβ–. Aβ+ APOE ɛ 4 carriers were at 348% greater risk than all other participants. Significant risk factors of progression in Aβ+ were age (HR: 1.05), PET SUVR (HR: 2.49) and APOE ɛ 4 carriage (HR: 2.63); only age was a significant risk factor in Aβ–(HR: 1.09). Aβ–progressors were not near the threshold for Aβ+. These relationships were not moderated by hypertension, diabetes, obesity, or stroke/TIA. Conclusion: Aβ+ is an important prognostic marker for progression from CN to MCI/dementia in older adults and APOE ɛ 4 carriage provides further predictive value in the presence of Aβ+. These data suggest that Aβ-associated clinical progression is consistent with clinical-pathological models of AD, whereas progression in the absence of elevated Aβ deposition may be the result of neuropathological processes other than AD that accumulate with age. Show more

Keywords: Alzheimer’s disease, APOE ɛ4, biomarkers, dementia, mild cognitive impairment

DOI: 10.3233/JAD-180507

Citation: Journal of Alzheimer's Disease, vol. 65, no. 4, pp. 1313-1325, 2018

Authors: Porter, Tenielle | Burnham, Samantha C. | Milicic, Lidija | Savage, Greg | Maruff, Paul | Lim, Yen Ying | Li, Qiao-Xin | Ames, David | Masters, Colin L. | Rainey-Smith, Stephanie | Rowe, Christopher C. | Salvado, Olivier | Groth, David | Verdile, Giuseppe | Villemagne, Victor L. | Laws, Simon M. | for the AIBL Research Group

Article Type: Research Article

Abstract: Background: With the exception of APOE, genetic variants associated with increased Alzheimer’s disease (AD) risk are characterized by small effect sizes. Polygenic risk scores (PRS) have shown utility in predicting AD risk; however, their utility for predicting decline in cognition at preclinical stages of AD is poorly understood. Objective: To validate associations of a 22-variant AD-risk-weighted PRS with AD risk and related biomarkers and to assess its utility to predict cognitive decline. Methods: The PRS was evaluated with respect to brain amyloid-β (Aβ) burden, cerebrospinal fluid (CSF) Aβ42 , total-tau, and phospho-tau, and decline in cognition in 643 (570 cognitively …normal (CN), 73 AD) PET-imaged participants from the longitudinal Australian Imaging, Biomarkers and Lifestyle (AIBL) Study of Ageing. Cognition was assessed using three composite measures; global cognition, verbal episodic memory, and a Pre-Alzheimer’s Cognitive Composite (PACC). Results: PRS, both with and without APOE, were positively correlated with brain Aβ burden, CSF total-tau, and phospho-tau in CN older adults. Further, in CN biomarker positive (Aβhigh ) participants, significant associations were observed with baseline and longitudinal cognition. However, this association was not observed after the removal of APOE. Partitioning the PRS into quartiles revealed that the PRS associations with cognitive decline in Aβhigh CN older adults is due to a saturating effect of APOE genotype. Conclusions: An AD-risk-weighted PRS is associated with cognitive decline in CN older adults. However, this association is absent when APOE genotype is excluded from the PRS, suggesting that associations with cognitive decline in this model of polygenic risk are driven by APOE genotype alone. Further research is needed to define appropriate PRSs with greater utility for predicting preclinical AD cognitive decline. Show more

Keywords: Alzheimer’s disease, amyloid-β, cognitive decline, episodic memory, polygenic risk scores

DOI: 10.3233/JAD-180713

Citation: Journal of Alzheimer's Disease, vol. 66, no. 3, pp. 1193-1211, 2018

Authors: Hollands, Simone | Lim, Yen Ying | Laws, Simon M. | Villemagne, Victor L. | Pietrzak, Robert H. | Harrington, Karra | Porter, Tenielle | Snyder, Peter | Ames, David | Fowler, Christopher | Rainey-Smith, Stephanie R. | Martins, Ralph N. | Salvado, Olivier | Robertson, Joanne | Rowe, Christopher C. | Masters, Colin L. | Maruff, Paul | for the AIBL Research Group

Article Type: Research Article

Abstract: Background: In cognitively normal (CN) older adults, carriage of the apolipoprotein E (APOE ) ɛ 4 allele is associated with increased risk for dementia of the Alzheimer type (AD-dementia). It is unclear whether this occurs solely through APOE ɛ 4 increasing amyloid-β (Aβ) accumulation or through processes independent of Aβ. Objective: To determine the extent and nature to which APOE ɛ 4 increases risk for clinical disease progression in CN older adults. Methods: Data from the total (n  = 765) and Aβ-imaged (n  = 423) CN cohort in the Australian Imaging, Biomarker and Lifestyle (AIBL) Study of Ageing was analyzed using Cox …proportional hazard models to estimate ɛ 4 risk for clinical disease progression over a 72-month follow-up. Results: With Aβ status unknown and risk from demographic characteristics controlled, ɛ 4 carriage increased risk for clinical disease progression over 72 months by 2.66 times compared to risk of non-ɛ 4 carriage. Re-analysis with Aβ status included showed that abnormally high Aβ increased risk for clinical disease progression over 72 months by 2.11 times compared to risk of low Aβ. However, with Aβ level known, ɛ 4 carriage was no longer predictive of clinical disease progression. Conclusion: In CN older adults, the risk of ɛ 4 for clinical disease progression occurs through the effect of ɛ 4 increasing Aβ levels. Show more

Keywords: Alzheimer’s disease, Alzheimer type dementia, amyloid-β, apolipoprotein E4, positron emission tomography

DOI: 10.3233/JAD-161019

Citation: Journal of Alzheimer's Disease, vol. 57, no. 2, pp. 411-422, 2017

Authors: Fernando, W.M.A.D. Binosha | Rainey-Smith, Stephanie R. | Gardener, Samantha L. | Villemagne, Victor L. | Burnham, Samantha C. | Macaulay, S. Lance | Brown, Belinda M. | Gupta, Veer Bala | Sohrabi, Hamid R. | Weinborn, Michael | Taddei, Kevin | Laws, Simon M. | Goozee, Kathryn | Ames, David | Fowler, Christopher | Maruff, Paul | Masters, Colin L. | Salvado, Olivier | Rowe, Christopher C. | Martins, Ralph N. | For the AIBL Research Group

Article Type: Research Article

Abstract: Accumulating evidence suggests a diet high in protein and fiber may confer some protection against Alzheimer’s disease (AD). However, no human studies to-date have assessed the relationship between protein and fiber intake, and plasma and brain amyloid-β (Aβ). Consequently, this cross-sectional study, investigated the association of self-reported dietary intakes of protein and fiber, with plasma and brain Aβ burden (n  = 541, and n  = 162 respectively), in a well-characterized cohort of cognitively normal older adults, drawn from the larger Australian Imaging, Biomarkers and Lifestyle (AIBL) study of aging. We observed 12.59 and 8.43 higher odds of ‘high’ brain Aβ burden (PiB …PET SUVR≥1.5) if protein intake fell in the lowest and middle tertile, respectively, compared to the highest tertile (p  = 0.008; p  = 0.013). Thus, in this cohort, the more protein consumed, the less likelihood of ‘high’ Aβ burden in the brain. No other significant associations were observed. The results of this study highlight the potentially protective impact of high dietary protein intake on brain Aβ burden in older adults, before objective memory decline is apparent. While longitudinal validation is required, these findings may assist in the development of dietary approaches aimed at preventing or delaying AD onset. Show more

Keywords: Alzheimer’s disease, amyloid-β, dietary fiber, dietary protein, PiB PET

DOI: 10.3233/JAD-170742

Citation: Journal of Alzheimer's Disease, vol. 61, no. 4, pp. 1589-1598, 2018

Authors: Fernandez, Shane | Burnham, Samantha C. | Milicic, Lidija | Savage, Greg | Maruff, Paul | Peretti, Madeline | Sohrabi, Hamid R. | Lim, Yen Ying | Weinborn, Michael | Ames, David | Masters, Colin L. | Martins, Ralph N. | Rainey-Smith, Stephanie | Rowe, Christopher C. | Salvado, Olivier | Groth, David | Verdile, Giuseppe | Villemagne, Victor L. | Porter, Tenielle | Laws, Simon M.

Article Type: Research Article

Abstract: Abstract. Background: Genetic variation in Spondin-1, specifically rs11023139, has been associated with reduced rates of cognitive decline in individuals with Alzheimer’s disease. Objective: The aim of this study was to assess whether the association was present in cognitively normal older adults. Methods: Longitudinal cognitive decline was investigated using linear mixed modelling in a cohort of 590 cognitively normal older adults enrolled in the Australian Imaging, Biomarkers and Lifestyle Study. Results: No independent effect of Spondin-1 rs11023139 on cognitive decline was observed. However, significant associations were observed for the interaction between Apolipoprotein E (APOE) ɛ 4 and rs11023139 in individuals with …high amyloid-β burden. APOE ɛ 4/rs11023139-A carriers declined significantly faster than APOE ɛ 4/rs11023139-G_G carriers in measures of global cognition (p  = 0.011) and verbal episodic memory (p  = 0.020). Conclusion: These results suggest that carriage of the Spondin-1 rs11023139-A allele significantly contributes to a worsening of cognitive performance in APOE ɛ 4 cognitively normal older adults with a high neocortical amyloid-β burden. Show more

Keywords: Alzheimer’s disease, amyloid-β, APOE, cognitive decline, SPON1, Spondin-1

DOI: 10.3233/ADR-200246

Citation: Journal of Alzheimer's Disease Reports, vol. 5, no. 1, pp. 111-120, 2021