Interaction Between BDNF Val66Met and APOE4 on Biomarkers of Alzheimer's Disease and Cognitive Decline.

BACKGROUND: Whether brain-derived neurotrophic factor (BDNF) Met carriage impacts the risk or progression of Alzheimer's disease (AD) is unknown. OBJECTIVE: To evaluate the interaction of BDNF Met and APOE4 carriage on cerebral metabolic rate for glucose (CMRgl), amyloid burden, hippocampus volume, and cognitive decline among cognitively unimpaired (CU) adults enrolled in the Arizona APOE cohort study. METHODS: 114 CU adults (mean age 56.85 years, 38% male) with longitudinal FDG PET, magnetic resonance imaging, and cognitive measures were BDNF and APOE genotyped. A subgroup of 58 individuals also had Pittsburgh B (PiB) PET imaging. We examined baseline CMRgl, PiB PET amyloid burden, CMRgl, and hippocampus volume change over time, and rate of change in cognition over an average of 15 years. RESULTS: Among APOE4 carriers, BDNF Met carriers had significantly increased amyloid deposition and accelerated CMRgl decline in regions typically affected by AD, but without accompanying acceleration of cognitive decline or hippocampal volume changes and with higher baseline frontal CMRgl and slower frontal decline relative to the Val/Val group. The BDNF effects were not found among APOE4 non-carriers. CONCLUSION: Our preliminary studies suggest that there is a weak interaction between BDNF Met and APOE4 on amyloid-ß plaque burden and longitudinal PET measurements of AD-related CMRgl decline in cognitively unimpaired late-middle-aged and older adults, but with no apparent effect upon rate of cognitive decline. We suggest that cognitive effects of BDNF variants may be mitigated by compensatory increases in frontal brain activity-findings that would need to be confirmed in larger studies.

Baseline demographic, clinical, and cognitive characteristics of the Alzheimer's Prevention Initiative (API) Autosomal-Dominant Alzheimer's Disease Colombia Trial.

INTRODUCTION: The API AutosomalDominant AD (ADAD) Colombia Trial is a placebo-controlled clinical trial of crenezumab in 252 cognitively unimpaired 30 to 60-year-old Presenilin 1 (PSEN1) E280A kindred members, including mutation carriers randomized to active treatment or placebo and non-carriers who receive placebo. METHODS: Of the 252 enrolled, we present data on a total of 242 mutation carriers and non-carriers matched by age range, excluding data on 10 participants to protect participant confidentiality, genetic status, and trial integrity. RESULTS: We summarize demographic, clinical, cognitive, and behavioral data from 167 mutation carriers and 75 non-carriers, 30 to 53 years of age. Carriers were significantly younger than non-carriers ((mean age ± SD) 37 ± 5 vs 42 ± 6), had significantly lower Mini Mental Status Exam (MMSE) scores (28.8 ± 1.4 vs 29.2 ± 1.0), and had consistently lower memory scores. DISCUSSION: Although PSEN1 E280A mutation carriers in the Trial are cognitively unimpaired, they have slightly lower MMSE and memory scores than non-carriers. Their demographic characteristics are representative of the local population.

Resistance to autosomal dominant Alzheimer's disease in an APOE3 Christchurch homozygote: a case report.

We identified a PSEN1 (presenilin 1) mutation carrier from the world's largest autosomal dominant Alzheimer's disease kindred, who did not develop mild cognitive impairment until her seventies, three decades after the expected age of clinical onset. The individual had two copies of the APOE3 Christchurch (R136S) mutation, unusually high brain amyloid levels and limited tau and neurodegenerative measurements. Our findings have implications for the role of APOE in the pathogenesis, treatment and prevention of Alzheimer's disease.

Visualizing Alzheimer's disease progression in low dimensional manifolds.

While tomographic neuroimaging data is information rich, objective, and with high sensitivity in the study of brain diseases such as Alzheimer's disease (AD), its direct use in clinical practice and in regulated clinical trial (CT) still has many challenges. Taking CT as an example, unless the relevant policy and the perception of the primary outcome measures change, the need to construct univariate indices (out of the 3-D imaging data) to serve as CT's primary outcome measures will remain the focus of active research. More relevant to this current study, an overall global index that summarizes multiple complicated features from neuroimages should be developed in order to provide high diagnostic accuracy and sensitivity in tracking AD progression over time in clinical setting. Such index should also be practically intuitive and logically explainable to patients and their families. In this research, we propose a new visualization tool, derived from the manifold-based nonlinear dimension reduction of brain MRI features, to track AD progression over time. In specific, we investigate the locally linear embedding (LLE) method using a dataset from Alzheimer's Disease Neuroimaging Initiative (ADNI), which includes the longitudinal MRIs from 562 subjects. About 20% of them progressed to the next stage of dementia. Using only the baseline data of cognitively unimpaired (CU) and AD subjects, LLE reduces the feature dimension to two and a subject's AD progression path can be plotted in this low dimensional LLE feature space. In addition, the likelihood of being categorized to AD is indicated by color. This LLE map is a new data visualization tool that can assist in tracking AD progression over time.

Predicting Imminent Progression to Clinically Significant Memory Decline Using Volumetric MRI and FDG PET.

BACKGROUND: Brain imaging measurements can provide evidence of possible preclinical Alzheimer's disease (AD). Their ability to predict individual imminent clinical conversion remains unclear. OBJECTIVE: To investigate the ability of pre-specified volumetric magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (FDG-PET) measurements to predict which cognitively unimpaired older participants would subsequently progress to amnestic mild cognitive impairment (aMCI) within 2 years. METHODS: From an apolipoprotein E4 (APOE4) enriched prospective cohort study, 18 participants subsequently progressed to the clinical diagnosis of aMCI or probable AD dementia within 1.8±0.8 years (progressors); 20 participants matched for sex, age, education, and APOE allele dose remained cognitively unimpaired for at least 4 years (nonprogressors). A complementary control group not matched for APOE allele dose included 35 nonprogressors. Groups were compared on baseline FDG-PET and MRI measures known to be preferentially affected in the preclinical and clinical stages of AD and by voxel-wise differences in regional gray matter volume and glucose metabolism. Receiver Operating Characteristic, binary logistic regression, and leave-one-out procedures were used to predict clinical outcome for the a priori measures. RESULTS: Compared to non-progressors and regardless of APOE-matching, progressors had significantly reduced baseline MRI and PET measurements in brain regions preferentially affected by AD and reduced hippocampal volume was the strongest predictor of an individual's imminent progression to clinically significant memory decline (79% sensitivity/78% specificity among APOE-matched cohorts). CONCLUSION: Regional MRI and FDG-PET measurements may be useful in predicting imminent progression to clinically significant memory decline.

Brain Imaging and Blood Biomarker Abnormalities in Children With Autosomal Dominant Alzheimer Disease: A Cross-Sectional Study.

IMPORTANCE: Brain imaging and fluid biomarkers are characterized in children at risk for autosomal dominant Alzheimer disease (ADAD). OBJECTIVE: To characterize and compare structural magnetic resonance imaging (MRI), resting-state and task-dependent functional MRI, and plasma amyloid-ß (Aß) measurements in presenilin 1 (PSEN1) E280A mutation-carrying and noncarrying children with ADAD. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional measures of structural and functional MRI and plasma Aß assays were assessed in 18 PSEN1 E280A carriers and 19 noncarriers aged 9 to 17 years from a Colombian kindred with ADAD. Recruitment and data collection for this study were conducted at the University of Antioquia and the Hospital Pablo Tobon Uribe in Medellín, Colombia, between August 2011 and June 2012. MAIN OUTCOMES AND MEASURES: All participants had blood sampling, structural MRI, and functional MRI during associative memory encoding and resting-state and cognitive assessments. Outcome measures included plasma Aß1-42 concentrations and Aß1-42:Aß1-40 ratios, memory encoding-dependent activation changes, resting-state connectivity, and regional gray matter volumes. Structural and functional MRI data were compared using automated brain mapping algorithms and search regions related to AD. RESULTS: Similar to findings in adult mutation carriers, in the later preclinical and clinical stages of ADAD, mutation-carrying children were distinguished from control individuals by significantly higher plasma Aß1-42 levels (mean [SD]: carriers, 18.8 [5.1] pg/mL and noncarriers, 13.1 [3.2] pg/mL; P < .001) and Aß1-42:Aß1-40 ratios (mean [SD]: carriers, 0.32 [0.06] and noncarriers, 0.21 [0.03]; P < .001), as well as less memory encoding task-related deactivation in parietal regions (eg, mean [SD] parameter estimates for the right precuneus were -0.590 [0.50] for noncarriers and -0.087 [0.38] for carriers; P < .005 uncorrected). Unlike carriers in the later stages, mutation-carrying children demonstrated increased functional connectivity of the posterior cingulate cortex with medial temporal lobe regions (mean [SD] parameter estimates were 0.038 [0.070] for noncarriers and 0.190 [0.057] for carriers), as well as greater gray matter volumes in temporal regions (eg, left parahippocampus; P < . 049, corrected for multiple comparisons). CONCLUSIONS AND RELEVANCE: Children at genetic risk for ADAD have functional and structural brain changes and abnormal levels of plasma Aß1-42. The extent to which the underlying brain changes are either neurodegenerative or developmental remains to be determined. This study provides additional information about the earliest known biomarker changes associated with ADAD.

Florbetapir PET, FDG PET, and MRI in Down syndrome individuals with and without Alzheimer's dementia.

INTRODUCTION: Down syndrome (DS) is associated with amyloid b (Ab) deposition. METHODS: We characterized imaging measurements of regional fibrillar Ab burden, cerebral metabolic rate for glucose (rCMRgl), gray matter volumes (rGMVs), and age associations in 5 DS with dementia (DS/AD1), 12 DS without dementia (DS/AD2), and 9 normal controls (NCs). RESULTS: There were significant group differences in mean standard uptake value ratios (SUVRs) for florbetapir with DS/AD1 having the highest, followed by DS/AD2, followed by NC. For [18F]-fluorodeoxyglucose positron emission tomography, posterior cingulate rCMRgl in DS/AD1 was significantly reduced compared with DS/AD2 and NC. For volumetric magnetic resonance imaging (vMRI), hippocampal volumes were significantly reduced for the DS/AD1 compared with DS/AD2 and NC. Age-related SUVR increases and rCMRgl reductions were greater in DS participants than in NCs. DISCUSSION: DS is associated with fibrillar Ab, rCMRgl, and rGMV alterations in the dementia stage and before the presence of clinical decline. This study provides a foundation for the studies needed to inform treatment and prevention in DS.

Improved power for characterizing longitudinal amyloid-ß PET changes and evaluating amyloid-modifying treatments with a cerebral white matter reference region.

UNLABELLED: In this article, we describe an image analysis strategy with improved power for tracking longitudinal amyloid-ß (Aß) PET changes and evaluating Aß-modifying treatments. METHODS: Our aims were to compare the power of template-based cerebellar, pontine, and cerebral white matter reference regions to track 24-mo florbetapir standardized uptake value (SUV) ratio (SUVR) changes; to relate those changes to 24-mo clinical declines; and to evaluate Aß-modifying treatments in Aß-positive (Aß+) and Aß-negative (Aß-) patients with probable Alzheimer dementia (pAD), in patients with mild cognitive impairment (MCI), in cognitively normal controls (NCs), and in cognitively normal apolipoprotein E4 (APOE4) carriers and noncarriers. We used baseline and follow-up (∼24 mo) florbetapir PET scans from 332 Aß+ and Aß- subjects participating in the multicenter Alzheimer's Disease Neuroimaging Initiative. Each of the proposed analyses included 31 pAD patients, 187 MCI patients, and 114 NCs. Cerebral-to-white matter, cerebellar, and pontine SUVRs were characterized in terms of their longitudinal variability; their power to track longitudinal fibrillar Aß increases in Aß+ and Aß- subgroups and cognitively normal APOE4 carriers and noncarriers; the sample sizes needed to detect attenuated accumulation of or clearance of fibrillar Aß accumulation in randomized clinical trials; and their ability to relate 24-mo fibrillar Aß increases to clinical declines. RESULTS: As predicted, cerebral-to-white matter SUVR changes were significantly less variable and had significantly greater power to detect 24-mo fibrillar Aß increases and evaluate Aß-modifying treatment effects in Aß+ pAD, MCI, and NC subjects and cognitively normal APOE4 carriers. They were also distinguished by the ability to detect significant associations between 24-mo Aß increases and clinical declines. CONCLUSION: A cerebral white matter reference region may improve the power to track longitudinal fibrillar Aß increases, to characterize their relationship to longitudinal clinical declines, and to evaluate Aß-modifying treatments in randomized clinical trials.

A potential role for the midbrain in integrating fat-free mass determined energy needs: An H2 (15) O PET study.

Little is known on how sensing of energy needs is centrally represented, integrated, and translated into the behavioral aspects of energy homeostasis. Fat free mass (FFM) is the major determinant of energy expenditure. We investigated how interindividual variances in FFM relate to neuronal activity in humans. Healthy adults (n = 64, 21F/43M; age 31.3 ± 9.1y; percentage of body fat [PFAT] 25.6 ± 10.7%; BMI 30.4 ± 9) underwent a 36h fast and subsequent H(2) (15) O positron emission tomographic (PET) measurement of regional cerebral blood flow (rCBF). Multiple variable regression analysis revealed significant associations of FFM with rCBF within the midbrain [including parts of the periaqueductal gray (PAG), ventral tegmental area (VTA), thalamic and hypothalamic regions], the bilateral parahippocampal region, left anterior cingulate, left insular cortex, right cerebellum, and distinct regions within the temporal and occipital cortex. In contrast, no significant associations were found for fat mass (FM). We investigated the potential functional-anatomical link between FFM and central regulation of food intake by performing a conjunction analysis of FFM and the perceived hunger feelings. This showed a significant overlap within the midbrain PAG. Mediation analysis demonstrated a significant indirect effect of FFM on hunger with PAG rCBF as mediator. Most regions we found to be associated with FFM form part in ascending homeostatic pathways and cortical circuitries implicated in the regulation of basic bodily functions indicating a potential role of these central networks in the integration of FFM determined energy needs.

Associations between biomarkers and age in the presenilin 1 E280A autosomal dominant Alzheimer disease kindred: a cross-sectional study.

IMPORTANCE: Age-associated changes in brain imaging and fluid biomarkers are characterized and compared in presenilin 1 (PSEN1)E280A mutation carriers and noncarriers from the world's largest known autosomal dominant Alzheimer disease (AD) kindred. OBJECTIVE: To characterize and compare age-associated changes in brain imaging and fluid biomarkers in PSEN1 E280A mutation carriers and noncarriers. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional measures of 18F-florbetapir positron emission tomography, 18F-fludeoxyglucose positron emission tomography, structural magnetic resonance imaging, cerebrospinal fluid (CSF), and plasma biomarkers of AD were assessed from 54 PSEN1 E280A kindred members (age range, 20-59 years). MAIN OUTCOMES AND MEASURES: We used brain mapping algorithms to compare regional cerebral metabolic rates for glucose and gray matter volumes in cognitively unimpaired mutation carriers and noncarriers. We used regression analyses to characterize associations between age and the mean cortical to pontine 18F-florbetapir standard uptake value ratios, precuneus cerebral metabolic rates for glucose, hippocampal gray matter volume, CSF Aß1-42, total tau and phosphorylated tau181, and plasma Aß measurements. Age at onset of progressive biomarker changes that distinguish carriers from noncarriers was estimated using best-fitting regression models. RESULTS: Compared with noncarriers, cognitively unimpaired mutation carriers had significantly lower precuneus cerebral metabolic rates for glucose, smaller hippocampal volume, lower CSF Aß1-42, higher CSF total tau and phosphorylated tau181, and higher plasma Aß1-42 measurements. Sequential changes in biomarkers were seen at age 20 years (95% CI, 14-24 years) for CSF Aß1-42, age 16 years (95% CI, 11-24 years) for the mean cortical 18F-florbetapir standard uptake value ratio, age 15 years (95% CI, 10-24 years) for precuneus cerebral metabolic rate for glucose, age 15 years (95% CI, 7-20 years) for CSF total tau, age 13 years (95% CI, 8-19 years) for phosphorylated tau181, and age 6 years (95% CI, 1-10 years) for hippocampal volume, with cognitive decline up to 6 years before the kindred's estimated median age of 44 years (95% CI, 43-45 years) at mild cognitive impairment diagnosis. No age-associated findings were seen in plasma Aß1-42 or Aß1-40. CONCLUSIONS AND RELEVANCE: This cross-sectional study provides additional information about the course of different AD biomarkers in the preclinical and clinical stages of autosomal dominant AD.

Brain differences in infants at differential genetic risk for late-onset Alzheimer disease: a cross-sectional imaging study.

IMPORTANCE: Converging evidence suggests brain structure alterations may precede overt cognitive impairment in Alzheimer disease by several decades. Early detection of these alterations holds inherent value for the development and evaluation of preventive treatment therapies. OBJECTIVE: To compare magnetic resonance imaging measurements of white matter myelin water fraction (MWF) and gray matter volume (GMV) in healthy infant carriers and noncarriers of the apolipoprotein E (APOE) ε4 allele, the major susceptibility gene for late-onset AD. DESIGN, SETTING, AND PARTICIPANTS: Quiet magnetic resonance imaging was performed at an academic research imaging center on 162 healthy, typically developing 2- to 25-month-old infants with no family history of Alzheimer disease or other neurological or psychiatric disorders. Cross-sectional measurements were compared in the APOE ε4 carrier and noncarrier groups. White matter MWF was compared in one hundred sixty-two 2- to 25-month-old sleeping infants (60 ε4 carriers and 102 noncarriers). Gray matter volume was compared in a subset of fifty-nine 6- to 25-month-old infants (23 ε4 carriers and 36 noncarriers), who remained asleep during the scanning session. The carrier and noncarrier groups were matched for age, gestational duration, birth weight, sex ratio, maternal age, education, and socioeconomic status. MAIN OUTCOMES AND MEASURES: Automated algorithms compared regional white matter MWF and GMV in the carrier and noncarrier groups and characterized their associations with age. RESULTS: Infant ε4 carriers had lower MWF and GMV measurements than noncarriers in precuneus, posterior/middle cingulate, lateral temporal, and medial occipitotemporal regions, areas preferentially affected by AD, and greater MWF and GMV measurements in extensive frontal regions and measurements were also significant in the subset of 2- to 6-month-old infants (MWF differences, P < .05, after correction for multiple comparisons; GMV differences, P < .001, uncorrected for multiple comparisons). Infant ε4 carriers also exhibited an attenuated relationship between MWF and age in posterior white matter regions. CONCLUSIONS AND RELEVANCE: While our findings should be considered preliminary, this study demonstrates some of the earliest brain changes associated with the genetic predisposition to AD. It raises new questions about the role of APOE in normal human brain development, the extent to which these processes are related to subsequent AD pathology, and whether they could be targeted by AD prevention therapies.

Polymorphism of brain derived neurotrophic factor influences ß amyloid load in cognitively intact apolipoprotein E ε4 carriers.

Aside from apolipoprotein E (APOE), genetic risk factors for ß amyloid deposition in cognitively intact individuals remain to be identified. Brain derived neurotrophic factor (BDNF) modulates neural plasticity, which has been implicated in Alzheimer's disease. We examined in cognitively normal older adults whether the BDNF codon 66 polymorphism affects ß amyloid burden and the relationship between ß amyloid burden and cognitive scores, and how this relates to the effect of APOE. Amyloid load was measured by means of (18)F-flutemetamol PET in 64 community-recruited cognitively intact individuals (mean age 66, S.D. 5.1). Recruitment was stratified according to a factorial design with APOE (ε4 allele present vs absent) and BDNF (met allele at codon 66 present vs absent) as factors. Individuals in the four resulting cells were matched by the number of cases, age, and gender. Among the APOE ε4 carriers, BDNF met positive subjects had a significantly higher amyloid load than BDNF met negative subjects, while BDNF met carrier status did not have an effect in APOE ε4 noncarriers. This interaction effect was localized to precuneus, orbitofrontal cortex, gyrus rectus, and lateral prefrontal cortex. In the APOE ε4/BDNF met carriers, a significant inverse relationship existed between episodic memory scores and amyloid burden but not in any of the other groups. This hypothesis-generating experiment highlights a potential role of BDNF polymorphisms in the preclinical phase of ß amyloid deposition and also suggests that BDNF codon 66 polymorphisms may influence resilience against ß amyloid-related effects on cognition.

Overfeeding over 24 hours does not activate brown adipose tissue in humans.

CONTEXT: Human brown adipose tissue (BAT) is activated with cold exposure, but it is unknown whether overfeeding activates BAT. OBJECTIVE: We determined BAT activation with cold, fasting, and overfeeding and the relationship of BAT activation with future weight change. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS: Sixteen healthy adults were evaluated during energy balance, fasting, and 24 hours of 200% overfeeding. All subjects had a fluorodeoxyglucose-positron emission tomography (PET) scan after exposure to 16°C to determine cold-induced BAT activity (CIBA). The first six subjects had a second PET scan after 36 hours of fasting to establish the lack of BAT activation at 22°C. The other subjects' second PET scan occurred after 24 hours of overfeeding at 22°C but only if they demonstrated CIBA. Twelve subjects returned at 6 months for reassessment of body composition. MAIN OUTCOME MEASURES: BAT was defined in cool scans as voxels with a standardized uptake value (SUV) of 2.0 or greater and Hounsfield units between -250 and -10. Body composition was assessed by dual-energy x-ray absorptiometry. RESULTS: Although 75% of the subjects demonstrated visible CIBA, none had visual BAT activity after overfeeding. CIBA was greater than that observed in the same defined BAT voxels after fasting (n = 6; 2.9 ± 0.5 vs 1.2 ± 0.2; Δ = -1.7; 95% confidence interval -2.4, -1.0 SUV; P < .01). In the second cohort, CIBA was also higher than observed BAT voxel activity after 24 hours overfeeding (n = 8; 3.5 ± 0.7 vs 0.9 ± 0.2; Δ = -2.6; 95% confidence interval -3.2, -1.9 SUV; P < .01). Baseline CIBA negatively correlated with changes in fat mass after 6 months (r = -0.72, P = .009). CONCLUSIONS: BAT may be important in weight regulation unrelated to the response to overeating.

Genetic susceptibility for Alzheimer disease neuritic plaque pathology.

IMPORTANCE: While numerous genetic susceptibility loci have been identified for clinical Alzheimer disease (AD), it is important to establish whether these variants are risk factors for the underlying disease pathology, including neuritic plaques. OBJECTIVES: To investigate whether AD susceptibility loci from genome-wide association studies affect neuritic plaque pathology and to additionally identify novel risk loci for this trait. DESIGN, SETTING, AND PARTICIPANTS: Candidate analysis of single-nucleotide polymorphisms and genome-wide association study in a joint clinicopathologic cohort, including 725 deceased subjects from the Religious Orders Study and the Rush Memory and Aging Project (2 prospective, community-based studies), followed by targeted validation in an independent neuroimaging cohort, including 114 subjects from multiple clinical and research centers. MAIN OUTCOMES AND MEASURES: A quantitative measure of neuritic plaque pathologic burden, based on assessments of silver-stained tissue averaged from multiple brain regions. Validation based on ß-amyloid load by immunocytochemistry, and replication with fibrillar ß-amyloid positron emission tomographic imaging with Pittsburgh Compound B or florbetapir. RESULTS: Besides the previously reported APOE and CR1 loci, we found that the ABCA7 (rs3764650; P = .02) and CD2AP (rs9349407; P = .03) AD susceptibility loci are associated with neuritic plaque burden. In addition, among the top results of our genome-wide association study, we discovered a novel variant near the amyloid precursor protein gene (APP, rs2829887) that is associated with neuritic plaques (P = 3.3 × 10-6). This polymorphism was associated with postmortem ß-amyloid load as well as fibrillar ß-amyloid in 2 independent cohorts of adults with normal cognition. CONCLUSIONS AND RELEVANCE: These findings enhance understanding of AD risk factors by relating validated susceptibility alleles to increased neuritic plaque pathology and implicate common genetic variation at the APP locus in the earliest, presymptomatic stages of AD.

Fat-free body mass but not fat mass is associated with reduced gray matter volume of cortical brain regions implicated in autonomic and homeostatic regulation.

Obesity has been associated with alterations of both functional and structural aspects of the human central nervous system. In obese individuals both fat mass (FM; primarily consisting of adipose tissue) and fat-free mass (FFM; all non-adipose tissues) are increased and it remains unknown whether these compartments have separate effects on human brain morphology. We used voxel-based morphometry to investigate the relationships between measures of body composition and regional gray matter volume (GMV) in 76 healthy adults with a wide range of adiposity (24 F/52 M; age 32.1 ± 8.8 years; percentage of body fat [PFAT%] 25.5 ± 10.9%; BMI 29.8 ± 8.9). Fat-free mass index (FFMI kg × m(-2)) showed negative associations in bilateral temporal regions, the bilateral medial and caudolateral OFC, and the left insula. Fat mass index (FMI kg × m(-2)) showed similar, but less extensive negative associations within temporal cortical regions and the left caudolateral orbitofrontal cortex (OFC). In addition, negative associations were seen for FMI with GMV of the cerebellum. Associations of FFMI with temporal and medial orbitofrontal GMV appeared to be independent of adiposity. No associations were seen between measures of adiposity (i.e. FM and PFAT) and GMV when adjusted for FFM. The majority of regions that we find associated with FFM have been implicated in the regulation of eating behavior and show extensive projections to central autonomic and homeostatic core structures. These data indicate that not adipose tissue or relative adiposity itself, but obesity related increases in absolute tissue mass and particularly FFM may have a more predominant effect on the human brain. This might be explained by the high metabolic demand of FFM and related increases in total energy needs.

Apolipoprotein E ε4 and age effects on florbetapir positron emission tomography in healthy aging and Alzheimer disease.

OBJECTIVES: Investigate apolipoprotein E ε4 (APOE4) gene and aging effects on florbetapir F18 positron emission tomography (PET) in normal aging and Alzheimer's disease (AD). METHODS: Florbetapir F18 PET images were analyzed from 245 participants, 18-92 years of age, from Avid Radiopharmaceutical's multicenter registered trials, including 86 younger healthy control volunteers (yHC), 61 older healthy control volunteers (oHC), 53 mild cognitive impairment (MCI) patients, and 45 AD dementia patients (DAT). Mean florbetapir standard uptake value ratios (SUVRs) were used to evaluate the effects of APOE4 carrier status, older age, and their interaction in each of these groups. RESULTS: In comparison with non-carriers, the APOE4 carriers in each of the oHC, MCI, and DAT groups had higher mean cortical-to-cerebellar florbetapir SUVRs, patterns of florbetapir PET elevations characteristic of DAT, and a higher proportion meeting florbetapir PET positivity criteria. Only the oHC group had a significant association between mean cortical florbetapir SUVRs and age. In cognitively normal adults, without regards to APOE4 genotype, amyloid began to increase at age 58 (95% confidence interval [CI]: 52.3-63.7), with a predicted typical age of florbetapir positivity occurring around age 71 years. Presence of the APOE4 gene reduced the age of predicted florbetapir positivity in normal aging to around age 56 years, approximately 20 years younger than non-carriers. INTERPRETATION: Cerebral amyloid deposition is associated with APOE4 carrier status in older healthy control subjects and symptomatic AD patients, and increases with age in older cognitively normal individuals. Amyloid imaging positivity appears to begin near age 56 years in cognitively intact APOE4 carriers and age 76 years in APOE4 non-carriers.

Florbetapir PET analysis of amyloid-ß deposition in the presenilin 1 E280A autosomal dominant Alzheimer's disease kindred: a cross-sectional study.

BACKGROUND: Fibrillar amyloid-ß (Aß) is thought to begin accumulating in the brain many years before the onset of clinical impairment in patients with Alzheimer's disease. By assessing the accumulation of Aß in people at risk of genetic forms of Alzheimer's disease, we can identify how early preclinical changes start in individuals certain to develop dementia later in life. We sought to characterise the age-related accumulation of Aß deposition in presenilin 1 (PSEN1) E280A mutation carriers across the spectrum of preclinical disease. METHODS: Between Aug 1 and Dec 6, 2011, members of the familial Alzheimer's disease Colombian kindred aged 18-60 years were recruited from the Alzheimer's Prevention Initiative's registry at the University of Antioquia, Medellín, Colombia. Cross-sectional assessment using florbetapir PET was done in symptomatic mutation carriers with mild cognitive impairment or mild dementia, asymptomatic carriers, and asymptomatic non-carriers. These assessments were done at the Banner Alzheimer's Institute in Phoenix, AZ, USA. A cortical grey matter mask consisting of six predefined regions.was used to measure mean cortical florbetapir PET binding. Cortical-to-pontine standard-uptake value ratios were used to characterise the cross-sectional accumulation of fibrillar Aß deposition in carriers and non-carriers with regression analysis and to estimate the trajectories of fibrillar Aß deposition. FINDINGS: We enrolled a cohort of 11 symptomatic individuals, 19 presymptomatic mutation carriers, and 20 asymptomatic non-carriers, ranging in age from 20 to 56 years. There was greater florbetapir binding in asymptomatic PSEN1 E280A mutation carriers than in age matched non-carriers. Fibrillar Aß began to accumulate in PSEN 1E280A mutation carriers at a mean age of 28·2 years (95% CI 27·3-33·4), about 16 years and 21 years before the predicted median ages at mild cognitive impairment and dementia onset, respectively. (18)F florbetapir binding rose steeply over the next 9·4 years and plateaued at a mean age of 37·6 years (95% CI 35·3-40·2), about 6 and 11 years before the expected respective median ages at mild cognitive impairment and dementia onset. Prominent florbetapir binding was seen in the anterior and posterior cingulate, precuneus, and parietotemporal and frontal grey matter, as well as in the basal ganglia. Binding in the basal ganglia was not seen earlier or more prominently than in other regions. INTERPRETATION: These findings contribute to the understanding of preclinical familial Alzheimer's disease and help set the stage for assessment of amyloid-modifying treatments in the prevention of familial Alzheimer's disease. FUNDING: Avid Radiopharmaceuticals, Banner Alzheimer's Foundation, Nomis Foundation, Anonymous Foundation, Forget Me Not Initiative, Colciencias, National Institute on Aging, and the State of Arizona.

Cerebral blood flow in Alzheimer's disease.

BACKGROUND: Alzheimer's disease (AD) dementia is a consequence of heterogeneous and complex interactions of age-related neurodegeneration and vascular-associated pathologies. Evidence has accumulated that there is increased atherosclerosis/arteriosclerosis of the intracranial arteries in AD and that this may be additive or synergistic with respect to the generation of hypoxia/ischemia and cognitive dysfunction. The effectiveness of pharmacologic therapies and lifestyle modification in reducing cardiovascular disease has prompted a reconsideration of the roles that cardiovascular disease and cerebrovascular function play in the pathogenesis of dementia. METHODS: Using two-dimensional phase-contrast magnetic resonance imaging, we quantified cerebral blood flow within the internal carotid, basilar, and middle cerebral arteries in a group of individuals with mild to moderate AD (n = 8) and compared the results with those from a group of age-matched nondemented control (NDC) subjects (n = 9). Clinical and psychometric testing was performed on all individuals, as well as obtaining their magnetic resonance imaging-based hippocampal volumes. RESULTS: Our experiments reveal that total cerebral blood flow was 20% lower in the AD group than in the NDC group, and that these values were directly correlated with pulse pressure and cognitive measures. The AD group had a significantly lower pulse pressure (mean AD 48, mean NDC 71; P = 0.0004). A significant group difference was also observed in their hippocampal volumes. Composite z-scores for clinical, psychometric, hippocampal volume, and hemodynamic data differed between the AD and NDC subjects, with values in the former being significantly lower (t = 12.00, df = 1, P = 0.001) than in the latter. CONCLUSION: These results indicate an association between brain hypoperfusion and the dementia of AD. Cardiovascular disease combined with brain hypoperfusion may participate in the pathogenesis/pathophysiology of neurodegenerative diseases. Future longitudinal and larger-scale confirmatory investigations measuring multidomain parameters are warranted.

Postprandial plasma PYY concentrations are associated with increased regional gray matter volume and rCBF declines in caudate nuclei--a combined MRI and H2(15)O PET study.

The anorexigenic gastrointestinal hormone Peptide YY plays an important role in the communication between the gastrointestinal tract and the central nervous system. PYY has been shown to modulate brain activity in regions implicated in reward and food related behavior. Its effects on brain structure however, remain unknown. Voxel-based morphometry was used to investigate the relationship between fasting and postprandial plasma PYY concentrations and regional gray matter volume (GMV). For this analysis twenty adult, non diabetic Caucasians were included (18F/2M, age 31±9 y, percentage of body fat [PFAT] 32±8%) who had volumetric brain magnetic resonance images and underwent H(2)(15)O positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF), a marker of local neuronal activity, and measurements of plasma total PYY, prior to (fasting) and following a satiating liquid meal. Voxel-wise analysis revealed a regional positive association between postprandial PYY and gray matter volume bilaterally in the caudate nuclei. These associations remained significant (p<0.05) after small volume correction for multiple comparisons. Based on these findings we investigated whether postprandial PYY is associated with PET measured rCBF of the caudate nucleus. We found a significant negative association between average postprandial caudate rCBF and postprandial plasma PYY concentrations (r=-0.60, p<0.02, age, sex and PFAT adjusted). Average postprandial caudate rCBF was also negatively associated with rCBF in the right medial orbitofrontal cortex and the right hippocampal formation (p<0.05, corrected for multiple comparisons). Total PYY is positively associated with gray matter but negatively with postprandial activity in the caudate nuclei while caudate activity is negatively associated with rCBF in prefrontal and paralimbic regions implicated in reward behavior. Thus, PYY may act centrally to modulate eating behavior via striatal networks.

Using positron emission tomography and florbetapir F18 to image cortical amyloid in patients with mild cognitive impairment or dementia due to Alzheimer disease.

OBJECTIVES: To characterize quantitative florbetapir F 18 (hereafter referred to as simply florbetapir) positron emission tomographic (PET) measurements of fibrillar ß-amyloid (Aß) burden in a large clinical cohort of participants with probable Alzheimer disease (AD) or mild cognitive impairment (MCI) and older healthy controls (OHCs). DESIGN: Cerebral-to-whole-cerebellar florbetapir standard uptake value ratios (SUVRs) were computed. Mean cortical SUVRs were compared. A threshold of SUVRs greater than or equal to 1.17 was used to reflect pathological levels of amyloid associated with AD based on separate antemortem PET and postmortem neuropathology data from 19 end-of-life patients. Similarly, a threshold of SUVRs greater than 1.08 was used to signify the presence of any identifiable Aß because this was the upper limit from a separate set of 46 individuals 18 to 40 years of age who did not carry apolipoprotein E (APOE) ε4. SETTING: Multiple research imaging centers. PARTICIPANTS: A total of 68 participants with probable AD, 60 participants with MCI, and 82 OHCs who were 55 years of age or older. Main Outcome Measure Florbetapir-PET activity. RESULTS: All of the participants (ie, those with probable AD or MCI and those who were OHCs) differed significantly in mean (SD) cortical florbetapir SUVRs (1.39 [0.24], 1.17 [0.27], and 1.05 [0.16], respectively; P < 1.0 × 10⁻7), in percentage meeting levels of amyloid associated with AD by SUVR criteria (80.9%, 40.0%, and 20.7%, respectively; P < 1.0 × 10⁻7), and in percentage meeting SUVR criteria for the presence of any identifiable Aß (85.3%, 46.6%, and 28.1%, respectively; P < 1.0 × 10⁻7). Among OHCs, the percentage of florbetapir positivity increased linearly by age decile (P = .05). For the 54 OHCs with available APOE genotypes, APOE ε4 carriers had a higher mean (SD) cortical SUVR than did noncarriers (1.14 [0.2] vs 1.03 [0.16]; P = .048). CONCLUSIONS: The findings of our analysis confirm the ability of florbetapir-PET SUVRs to characterize amyloid levels in clinically probable AD, MCI, and OHC groups using continuous and binary measures of fibrillar Aß burden. It introduces criteria to determine whether an image is associated with an intermediate-to-high likelihood of pathologic AD or with having any identifiable cortical amyloid level above that seen in low-risk young controls.