Citations

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.

ABSTRACT Background and Purpose Neurodegeneration of the substantia nigra in Lewy body disease is associated with iron deposition, which increases the magnetic susceptibility of the substantia nigra on MRI. Our objective was to measure iron deposition in the substantia nigra in patients with probable dementia with Lewy bodies (pDLB) and patients who are at risk for pDLB by quantitative susceptibility mapping (QSM). Methods Participants included pDLB ( n = 36), mild cognitive impairment with at least one core feature of DLB (MCI‐LB; n = 15), idiopathic rapid eye movement sleep behavior disorder (iRBD; n = 11), and an age‐and gender‐matched clinically unimpaired control group ( n = 102). QSM was derived from multi‐echo 3D gradient recalled echo MRI at 3T, and groups were compared on mean susceptibility values of the substantia nigra and its relation to parkinsonism severity. Results Patients with pDLB had higher susceptibility in the substantia nigra compared to controls ( p < 0.001) and MCI‐LB ( p = 0.043). The susceptibility of substantia nigra showed an increasing trend from controls to iRBD and MCI‐LB, and to pDLB ( p < 0.001). Parkinsonism severity was not associated with the mean susceptibility in the substantia nigra in the patient groups. Conclusions Our data suggested that QSM is sensitive to the increased magnetic susceptibility due to higher iron content in the substantia nigra in pDLB. The trend of increasing susceptibility from controls to iRBD and MCI‐LB, and to pDLB suggests that iron deposition in the substantia nigra starts to increase as early as the prodromal stage in DLB and continues to increase as the disease progresses, independent of parkinsonism severity.

Background and Purpose: Cerebral microbleeds (CMBs) are represented by small areas of hemosiderin deposition, detected on brain magnetic resonance imaging (MRI), and found in ≈23% of the cognitively normal population over age of 60 years. CMBs predict risk of hemorrhagic and ischemic stroke. They correlate with increased cardiovascular mortality. In this article, we sought to determine in a population-based study whether antithrombotic medications correlate with CMBs and, if present, whether the association was direct or mediated by another variable. Methods: The study consisted of 1253 participants from the population-based Mayo Clinic Study of Aging who underwent T2* gradient-recalled echo magnetic resonance imaging. We tested the relationship between antithrombotic medications and CMB presence and location, using multivariable logistic-regression models. Ordinal logistic models tested the relationship between antithrombotics and CMB frequency. Using structural equation models, we assessed the effect of antithrombotic medications on presence/absence of CMBs and count of CMBs in the CMB-positive group, after considering the effects of age, sex, vascular risk factors, amyloid load by positron emission tomography, and apoE. Results: Two hundred ninety-five participants (26.3%) had CMBs. Among 678 participants taking only antiplatelet medications, 185 (27.3%) had CMBs. Among 95 participants taking only an anticoagulant, 43 (45.3%) had CMBs. Among 44 participants taking an anticoagulant and antiplatelet therapy, 21 (48.8%) had CMBs. Anticoagulants correlated with the presence and frequency of CMBs, whereas antiplatelet agents were not. Structural equation models showed that predictors for presence/absence of CMBs included older age at magnetic resonance imaging, male sex, and anticoagulant use. Predictors of CMB count in the CMB-positive group were male sex and amyloid load. Conclusions: Anticoagulant use correlated with presence of CMBs in the general population. Amyloid positron emission tomography correlated with the count of CMBs in the CMB-positive group.

Background: The relationship between cerebral microbleeds (CMBs) on hemosiderin-sensitive MRI sequences and cerebral amyloid angiopathy (CAA) remains unclear in population-based participants or in individuals with dementia. Objective: To determine whether CMBs on antemortem MRI correlate with CAA. Methods: We reviewed 54 consecutive participants with antemortem T2*GRE-MRI sequences and subsequent autopsy. CMBs were quantified on MRIs closest to death. Autopsy CAA burden was quantified in each region including leptomeningeal/cortical and capillary CAA. By a clustering approach, we examined the relationship among CAA variables and performed principal component analysis (PCA) for dimension reduction to produce two scores from these 15 interrelated predictors. Hurdle models assessed relationships between principal components and lobar CMBs. Results: MRI-based CMBs appeared in 20/54 (37%). 10 participants had ≥2 lobar-only CMBs. The first two components of the PCA analysis of the CAA variables explained 74% variability. The first rotated component (RPC1) consisted of leptomeningeal and cortical CAA and the second rotated component of capillary CAA (RPC2). Both the leptomeningeal and cortical component and the capillary component correlated with lobar-only CMBs. The capillary CAA component outperformed the leptomeningeal and cortical CAA component in predicting lobar CMBs. Both capillary and the leptomeningeal/cortical components correlated with number of lobar CMBs. Conclusion: Capillary and leptomeningeal/cortical scores correlated with lobar CMBs on MRI but lobar CMBs were more closely associated with the capillary component. The capillary component correlated with APOE ɛ4, highlighting lobar CMBs as one aspect of CAA phenotypic diversity. More CMBs also increase the probability of underlying CAA.

Background: The identification of blood-borne biomarkers for the diagnosis and prognosis of Alzheimer’s disease and related dementias is more feasible at the population level than obtaining cerebrospinal fluid or neuroimaging markers. Objective: This study determined the association of blood microvesicles, derived from cells of the neurovascular unit, with brain amyloid-β deposition in menopausal women. Methods: A subset of women from the Kronos Early Estrogen Prevention Study underwent brain amyloid-β positron emission tomography three years following cessation of study treatment with placebo (PL, n = 29), transdermal 17β-estradiol (tE2; n = 21), or oral conjugated equine estrogen (oCEE; n = 17). Isolated peripheral venous blood microvesicles were analyzed by digital flow cytometry using fluorophore conjugated antibodies directed toward total tau, amyloid-β 1–42 (Aβ1–42), neuron specific class III β-tubulin (Tuj1), microglia ionized calcium -binding adaptor molecule 1(Iba1), glial fibrillary acid protein (GFAP), and low density lipoprotein receptor-related protein1 (LRP1). Principal components analysis reduced the dimensionality of these selected six markers to two principal components (PCs). Proportional odds ordinal logistic regression analysis was used with amyloid-β deposition regressed on these PCs. Results: Only the number of microvesicles positive for Aβ1–42 differed statistically among prior treatment groups (median [IQR]: 6.06 [2.11, 12.55] in PL; 2.49 [0.73, 3.59] in tE2; and 4.96 [0.83, 10.31] in oCEE; p = 0.032). The joint association between the 2 PCs and brain amyloid-β deposition was significant (p = 0.045). Conclusion: Six selected markers expressing peripheral blood microvesicles derived from cells of the neurovascular unit, when summarized into two principal components, were associated with brain amyloid-β deposition.

Hormone therapy improves sleep in menopausal women and recent data suggest that transdermal 17β-estradiol may reduce the accumulation of cortical amyloid-β. However, how menopausal hormone therapies modify the associations of amyloid-β accumulation with sleep quality is not known. In this study, associations of sleep quality with cortical amyloid-β deposition and cognitive function were assessed in a subset of women who had participated in the Kronos early estrogen prevention study. It was a randomized, placebo-controlled trial in which recently menopausal women (age, 42–58; 5–36 months past menopause) were randomized to (1) oral conjugated equine estrogen (n = 19); (2) transdermal 17β-estradiol (tE2, n = 21); (3) placebo pills and patch (n = 32) for 4 years. Global sleep quality score was calculated using Pittsburgh sleep quality index, cortical amyloid-β deposition was measured with Pittsburgh compound-B positron emission tomography standard uptake value ratio and cognitive function was assessed in four cognitive domains 3 years after completion of trial treatments. Lower global sleep quality score (i.e., better sleep quality) correlated with lower cortical Pittsburgh compound-B standard uptake value ratio only in the tE2 group (r = 0.45, P = 0.047). Better global sleep quality also correlated with higher visual attention and executive function scores in the tE2 group (r = −0.54, P = 0.02) and in the oral conjugated equine estrogen group (r = −0.65, P = 0.005). Menopausal hormone therapies may influence the effects of sleep on cognitive function, specifically, visual attention and executive function. There also appears to be a complex relationship between sleep, menopausal hormone therapies, cortical amyloid-β accumulation and cognitive function, and tE2 formulation may modify the relationship between sleep and amyloid-β accumulation.