Kantarci, Kejal

Abstract Normal brain aging is accompanied by patterns of functional and structural change. Alzheimer's disease (AD), a representative neurodegenerative disease, has been linked to accelerated brain aging at respective age ranges. Here, we developed a deep learning-based brain age prediction model using fluorodeoxyglucose (FDG) PET and structural MRI and tested how the brain age gap relates to degenerative cognitive syndromes including mild cognitive impairment, AD, frontotemporal dementia, and Lewy body dementia. Occlusion analysis, performed to facilitate interpretation of the model, revealed that the model learns an age- and modality-specific pattern of brain aging. The elevated brain age gap in dementia cohorts was highly correlated with the cognitive impairment and AD biomarker. However, regions generating brain age gaps were different for each diagnosis group of which the AD continuum showed similar patterns to normal aging in the CU.

The objective of this study was to investigate the cross-sectional associations of atrial fibrillation with neuroimaging measures of cerebrovascular disease and Alzheimer’s disease-related pathology, and their interaction with cognitive impairment. MRI scans of non-demented individuals (n=1044) from the population-based Mayo Clinic Study of Aging were analyzed for infarctions, total grey matter, hippocampal and white matter hyperintensity volumes. A subset of 496 individuals underwent FDG and C-11 Pittsburgh compound B (PiB) PET scans. We assessed the associations of atrial fibrillation with i) categorical MRI measures (cortical and subcortical infarctions) using multivariable logistic regression models, and with ii) continuous MRI measures ( hippocampal, total grey matter, and white matter hyperintensity volumes) and FDG-PET and PiB-PET measures using multivariable linear regression models, and adjusting for confounders. Among participants who underwent MRI (median age, 77.8, 51.6% male), 13.5% had atrial fibrillation. Presence of atrial fibrillation was associated with subcortical infarctions (odds ratio [OR], 1.83; p=0.002), cortical infarctions (OR, 1.91; p=0.03), total grey matter volume (Beta [β], -.025, p<.0001) after controlling for age, education, gender, APOE e4 carrier status, coronary artery disease, diabetes, history of clinical stroke, and hypertension. However, atrial fibrillation was not associated with white matter hyperintensity volume, hippocampal volume, Alzheimer’s pattern of FDG hypometabolism or PiB uptake. There was a significant interaction of cortical infarction (p for interaction=0.004) and subcortical infarction (p for interaction =0.015) with atrial fibrillation with regards to odds of mild cognitive impairment (MCI). Using subjects with no atrial fibrillation and no infarction as the reference, the OR (95% confidence intervals [CI]) for MCI was 2.98 (1.66, 5.35;p = 0.0002) among participants with atrial fibrillation and any infarction, 0.69 (0.36, 1.33;p= 0.27) for atrial fibrillation and no infarction, and 1.50 (0.96, 2.32;p = 0.07) for no atrial fibrillation and any infarction. These data highlight that atrial fibrillation is associated with MCI in the presence of infarctions.

Hypertension is highly prevalent in the elderly population and microinfarcts are the most common vascular brain pathology identified in older adults at autopsy. We investigated the associations between systolic and diastolic blood pressures measured antemortem and the presence of microinfarcts at autopsy. Study subjects (n=302; age range=71-95) were participants in the population-based Mayo Clinic Study of Aging autopsy study, who had blood pressure measurements recorded during life. We investigated both cross-sectional systolic and diastolic blood pressure measurements at the baseline visit and the change in blood pressure (slope). Presence and location (subcortical or cortical) of chronic microinfarcts was abstracted from the autopsy reports. Of the 302 study subjects, 47 (16%) had cerebral microinfarcts, and, of those, 18 (38%) had subcortical microinfarcts and 29 (62%) had only cortical microinfarcts. The baseline blood pressures were not different between subjects with no microinfarcts, subcortical microinfarcts, and only cortical microinfarcts. In a logistic regression model including time between last blood pressure measurement and death, a greater decline in systolic [OR= 1.06 (1.01, 1.11); p=0.02]) and greater decline in diastolic [OR= 1.11 (1.02, 1.20); p=0.01] blood pressures were predictors of the presence of subcortical microinfarcts at autopsy. However, these variables were not associated with the presence of cortical microinfarcts. In conclusion, microinfarcts are common in the older adult population, and most of them are located in the cortex. A greater decline in both systolic and diastolic blood pressures and their association with subcortical microinfarcts, but not with cortical microinfarcts, may have implications for aggressive lowering of blood pressure in the elderly population.

Introduction: Cortical superficial siderosis (cSS) refers to deposition of blood breakdown products along the cerebral cortex, causing characteristic staining patterns seen with iron-sensitive MRI techniques. Cortical superficial siderosis is a relatively rare disorder, but has been linked to cerebral amyloid angiopathy and Alzheimer’s disease. The objective of this study was to determine the frequency and natural history of cSS in the general elderly population. Methods: MRI scans from the Mayo Clinic Study of Aging (MCSA), an ongoing population-based study of elderly residents in Olmsted County, Minnesota, were reviewed by neuroradiologists. Participants with cSS were identified based on linear pattern of hypointensity on gradient recalled echo imaging consistent with cSS. Exclusion criteria were: 1) MRI findings not consistent with cSS or 2) alternative explanation for MRI findings (such as aneurysmal subarachnoid hemorrhage, intracranial surgery, or trauma). Additional data abstracted included extent of cSS, presence of cerebral microbleeds, and clinical outcome. Results: Eleven out of 1,441 participants had MRI scans showing cSS (0.8%). When stratified by age, the frequency was 0.4% in those 50 to 70 years old and 1.1% in those over 70 years old. Six participants had only focal involvement of cSS (restricted to three or fewer sulci) and five had disseminated involvement (affecting more than three sulci). Microbleeds were seen in four of five (80%) participants with disseminated cSS, but none with focal cSS. Five participants (2 focal, 3 disseminated cSS) had follow up MRI scans, with an average follow up of 25 months. There was no further hemorrhage in those with focal cSS. However, all three participants with disseminated cSS experienced additional hemorrhage: one with new microbleeds, one with new microbleeds and lobar hemorrhage, and one with sulcal subarachnoid hemorrhage and lobar hemorrhage. Conclusion: Although rare, cSS may be encountered in the general elderly population. Extent of involvement of cSS and concomitant microbleeds may be important risk factors for progression of disease and intracerebral hemorrhage. The clinical significance of focal cSS occurring in the absence of microbleeds requires further investigation.

Introduction: Cerebral microbleed (CMB) location may predict underlying pathology. Deep CMBs are more associated with hypertensive vascular disease, while lobar CMBs are more associated with cerebral amyloid angiopathy (CAA). The objective of this study was to determine the neuroimaging pathology associated with CMBs. Methods: We analyzed 1,831 nondemented ARIC participants (mean age=76.3 ±5.3 years, 40% male, 27% black) with 3T MRI scans at the fifth exam (2011-13). We fit multinomial logistic regression models to assess the effect of brain volumes (AD signature region atrophy, total gray matter, frontal, and log 2 -transformed white matter hyperintensities (WMH) volume), infarct frequencies (lacunar, non-lacunar, and total), and APOE (number of ε4 alleles) on CMB location (no, any deep, or lobar only CMBs). Models were weighted for the sample selection scheme and adjusted for age, male, education, hypertension, ever smoking status, diabetes, race-site membership, and estimated intracranial volume (brain volume models only). Results: The frequency of CMBs was 24.1%. A larger WMH volume, greater total infarct frequency, and smaller total grey volume increased the relative risks (RR) of both deep and lobar CMBs compared to no CMBs; increasing the WMH volume also increased the RR of deep to lobar CMBs. Additional lacunar infarcts increased the RR of deep compared to no CMBs, whereas AD signature region atrophy and APOE ε4 homozygosity increased the RR of lobar CMBs. Conclusion: CMBs are a common vascular pathology in the elderly. Deep CMB presence is associated with MRI features of hypertensive small vessel disease, while lobar CMB presence is associated with MRI features of CAA and Alzheimer’s disease.

Background Break down of the blood brain barrier and activation of brain cells are implicated in progression of deposition of β‐amyloid that is associated with the pathophysiology of Alzheimer's disease. A previous study from our group indicated that deposition of β‐amyloid may be reduced in the brains of menopausal women treated with transdermal 17β‐estradiol. This study aimed to determine the association of peripheral microvesicles carrying markers of cells of the neurovascular unit with β‐amyloid in the brains of menopausal women and if the association was affected by prior menopausal hormone treatments (MHT). Methods Menopausal women previously enrolled in the Kronos Early Estrogen Prevention Study at Mayo Clinic underwent β‐amyloid positron emission tomography (PET) imaging of their brains 3 years following treatment with either placebo (PL, n=29), transdermal 17β‐estradiol (tE2; n=21), or oral conjugated equine estrogen (oCEE; n=17) for 4 years. Microvesicles (MV) were isolated from peripheral venous blood by differential centrifugation and analyzed by flow cytometry using fluorophore conjugated antibodies directed toward total tau, β‐amyloid 1‐42 (Ab1‐42), neuron specific class III β‐tubulin (Tuj1), microglia ionized calcium adaptor molecule 1(Iab‐1), glial fibrillar acid protein (GFAP), and low density lipoprotein receptor‐related protein 1. Principal components analysis was used to reduce the dimensionality of the 6 brain markers to 2 principal components (PCs). Proportional odds ordinal logistic regression analysis was used to regress deposition of β‐amyloid on the 2 PCs with and without adjustment for MHT group. Results Number of blood MV positive for Ab1‐42 differed significantly among MHT groups (median [IQR]: 6.06 [2.11, 12.55] in the PL; 2.49 [0.73, 3.59] in the tE2 and 4.96 [0.83, 10.31] in the oCEE; P=0.036). The first 2 PCs explain 58% of the variance of the 6 markers. PC#1 represented a contrast between MV‐Iab‐1 and the MV‐GFAP and MV‐Tuj1. In multivariable models, brain β‐amyloid load positively associated with the first PC after adjustment for MHT (P= 0.006). Conclusion MV derived from cells of the neurovascular unit can be detected in peripheral blood, and, when combined into summary scores, showed an association with deposition of β‐amyloid in the brain that is independent of MHT. Support or Funding Information Supported by grants from NIH P50 AG044170 and the Mayo Foundation This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Objective Blood thrombogenicity and vascular inflammation may influence development of white matter hyperintensities (WMH) in the brain. This study aimed to determine if menopausal hormone treatments (MHT) modified that association in recently menopausal women who were enrolled in the Kronos Early Estrogen Prevention Study (KEEPS) at Mayo Clinic. Methods Women (n=95) underwent MRI prior to and at 18, 36 and 48 months after randomization to either transdermal 17β‐estradiol (tE2, n=30), conjugated equine estrogen (oCEE, n=29) both with progesterone for 12 days per month or placebo pills and patch (PBO, n=36). Fasting blood was analyzed for a set of 14 activation markers of platelets and endothelial cells, inflammation, and thrombogenicity. Principal components (PC) analysis was used to reduce dimensionality of these markers, and the first 5 PC identified were then assessed for association with treatment and changes in WMH. Results WMH increased in all groups over the 48 months of treatment with greater increases in the oCEE compared to tE2 and PBO (P=0.015). The 5 PC explained 62% of the variation in cellular activation markers. A global test of these 5 PC revealed a borderline association with treatment group (P=0.059), with the PC reflecting total platelet count, platelet microaggregates and ATP secretion showing higher scores in the oCEE compared to the other groups (P=0.006). The change in WMH over the 48 months of MHT showed an overall association with the 5 PC (P=0.026), the most prominent of which was the first PC reflecting vascular inflammation by number of blood microveicles (MV) from activated monocytes and endothelial cells and MV positive for intercellular adhesion molecule 1 (P=0.001). There was no evidence that this association differed by MHT. Conclusion Markers of blood thrombogenicity and inflammation may influence development of WMH in the brain but this relationship may be influenced by factors other than the type of MHT used in the KEEPS study. Support or Funding Information NIH P50 AG44170 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

White matter hyperintensities (WMHs) are associated with cerebral microvascular disease. Our objective was to investigate changes in volume of WMH in relationship to conventional cerebrovascular risk factors in recently menopausal women (within 6 months – 3 yrs of their last menses) enrolled in the Kronos Early Estrogen Prevention Study (KEEPS). Platelet activation, numbers of platelet‐derived microvesicles and conventional risk factors for cerebrovascular disease were determined in women (105) enrolled in KEEPS at Mayo Clinic. Each woman underwent MRI of the brain and WMH volumes were derived from the segmented Fluid Attenuated Inversion Recovery images at baseline and 36 months after randomization to treatment. Parametric, nonparametric and log transformation statistical analyses were conducted appropriately. Blood pressure and lipid profiles at baseline were not associated with changes in WMHs. However, baseline platelet micro‐aggregates, annexin V positive microvesicles and plasma activated protein C significantly correlated with increases in WMHs at 36 months. In conclusion, this correlation of increase in WMH with markers of platelet activation measured at baseline suggests that activated platelets and factors contributing to platelet activation may be causal to development of WMH. Supported by the Aurora Fnd, NIH HL90639, NS066147, HD65987 and the Mayo Fnd.

Abstract Dementia with Lewy bodies (DLB) is neuropathologically defined by the presence of α-synuclein aggregates, but many DLB cases show concurrent Alzheimer’s disease pathology in the form of amyloid-β plaques and tau neurofibrillary tangles. The first objective of this study was to investigate the effect of Alzheimer’s disease co-pathology on functional network changes within the default mode network (DMN) in DLB. Second, we studied how the distribution of tau pathology measured with PET relates to functional connectivity in DLB. Twenty-seven DLB, 26 Alzheimer’s disease and 99 cognitively unimpaired participants (balanced on age and sex to the DLB group) underwent tau-PET with AV-1451 (flortaucipir), amyloid-β-PET with Pittsburgh compound-B (PiB) and resting-state functional MRI scans. The resing-state functional MRI data were used to assess functional connectivity within the posterior DMN. This was then correlated with overall cortical flortaucipir PET and PiB PET standardized uptake value ratio (SUVr). The strength of interregional functional connectivity was assessed using the Schaefer atlas. Tau-PET covariance was measured as the correlation in flortaucipir SUVr between any two regions across participants. The association between region-to-region functional connectivity and tau-PET covariance was assessed using linear regression. Additionally, we identified the region with highest and the region with lowest tau SUVrs (tau hot- and cold spots) and tested whether tau SUVr in all other brain regions was associated with the strength of functional connectivity to these tau hot and cold spots. A reduction in posterior DMN connectivity correlated with overall higher cortical tau- (r = −0.39, P = 0.04) and amyloid-PET uptake (r = −0.41, P = 0.03) in the DLB group, i.e. patients with DLB who have more concurrent Alzheimer’s disease pathology showed a more severe loss of DMN connectivity. Higher functional connectivity between regions was associated with higher tau covariance in cognitively unimpaired, Alzheimer’s disease and DLB. Furthermore, higher functional connectivity of a target region to the tau hotspot (i.e. inferior/medial temporal cortex) was related to higher flortaucipir SUVrs in the target region, whereas higher functional connectivity to the tau cold spot (i.e. sensory-motor cortex) was related to lower flortaucipir SUVr in the target region. Our findings suggest that a higher burden of Alzheimer’s disease co-pathology in patients with DLB is associated with more Alzheimer’s disease-like changes in functional connectivity. Furthermore, we found an association between the brain’s functional network architecture and the distribution of tau pathology that has recently been described in Alzheimer’s disease. We show that this relationship also exists in patients with DLB, indicating that similar mechanisms of connectivity-dependent occurrence of tau pathology might be at work in both diseases.