Cerebrospinal Fluid Clearance in Alzheimer Disease Measured with Dynamic PET.

Evidence supporting the hypothesis that reduced cerebrospinal fluid (CSF) clearance is involved in the pathophysiology of Alzheimer disease (AD) comes primarily from rodent models. However, unlike rodents, in which predominant extracranial CSF egress is via olfactory nerves traversing the cribriform plate, human CSF clearance pathways are not well characterized. Dynamic PET with 18F-THK5117, a tracer for tau pathology, was used to estimate the ventricular CSF time-activity as a biomarker for CSF clearance. We tested 3 hypotheses: extracranial CSF is detected at the superior turbinates; CSF clearance is reduced in AD; and CSF clearance is inversely associated with amyloid deposition. Methods: Fifteen subjects, 8 with AD and 7 normal control volunteers, were examined with 18F-THK5117. Ten subjects additionally underwent 11C-Pittsburgh compound B (11C-PiB) PET scanning, and 8 were 11C-PiB-positive. Ventricular time-activity curves of 18F-THK5117 were used to identify highly correlated time-activity curves from extracranial voxels. Results: For all subjects, the greatest density of CSF-positive extracranial voxels was in the nasal turbinates. Tracer concentration analyses validated the superior nasal turbinate CSF signal intensity. AD patients showed ventricular tracer clearance reduced by 23% and 66% fewer superior turbinate CSF egress sites. Ventricular CSF clearance was inversely associated with amyloid deposition. Conclusion: The human nasal turbinate is part of the CSF clearance system. Lateral ventricle and superior nasal turbinate CSF clearance abnormalities are found in AD. Ventricular CSF clearance reductions are associated with increased brain amyloid depositions. These data suggest that PET-measured CSF clearance is a biomarker of potential interest in AD and other neurodegenerative diseases.

FDG and Amyloid PET in Cognitively Normal Individuals at Risk for Late-Onset Alzheimer's Disease.

Having a parent affected by late-onset Alzheimer's disease (AD) is a major risk factor for cognitively normal (NL) individuals. This study explores the potential of PET with 18F-FDG and the amyloid- ß (Aß) tracer 11C-Pittsburgh Compound B (PiB) for detection of individual risk in NL adults with AD-parents. METHODS: FDG- and PiB-PET was performed in 119 young to late-middle aged NL individuals including 80 NL with positive family history of AD (FH+) and 39 NL with negative family history of any dementia (FH-). The FH+ group included 50 subjects with maternal (FHm) and 30 with paternal family history (FHp). Individual FDG and PiB scans were Z scored on a voxel-wise basis relative to modality-specific reference databases using automated procedures and rated as positive or negative (+/-) for AD-typical abnormalities using predefined criteria. To determine the effect of age, the cohort was separated into younger (49 ± 9 y) and older (68 ± 5 y) groups relative to the median age (60 y). RESULTS: Among individuals of age >60 y, as compared to controls, NL FH+ showed a higher frequency of FDG+ scans vs. FH- (53% vs. 6% p < 0.003), and a trend for PiB+ scans (27% vs. 11%; p = 0.19). This effect was observed for both FHm and FHp groups. Among individuals of age ≤60 y, NL FHm showed a higher frequency of FDG+ scans (29%) compared to FH- (5%, p = 0.04) and a trend compared to FHp (11%) (p = 0.07), while the distribution of PiB+ scans was not different between groups. In both age cohorts, FDG+ scans were more frequent than PiB+ scans among NL FH+, especially FHm (p < 0.03). FDG-PET was a significant predictor of FH+ status. Classification according to PiB status was significantly less successful. CONCLUSIONS: Automated analysis of FDG- and PiB-PET demonstrates higher rates of abnormalities in at-risk FH+ vs FH- subjects, indicating potentially ongoing early AD-pathology in this population. The frequency of metabolic abnormalities was higher than that of Aß pathology in the younger cohort, suggesting that neuronal dysfunction may precede major aggregated Aß burden in young NL FH+. Longitudinal follow-up is required to determine if the observed abnormalities predict future AD.

Nutrient intake and brain biomarkers of Alzheimer's disease in at-risk cognitively normal individuals: a cross-sectional neuroimaging pilot study.

OBJECTIVE: There is increasing evidence to suggest that diet, one of the most important modifiable environmental factors, may play a role in preventing or delaying cognitive decline and Alzheimer's disease (AD). This study examines the relationship between dietary nutrients and brain biomarkers of AD in cognitively normal individuals (NL) with and without AD risk factors. DESIGN: As part of an ongoing brain imaging study, participants received clinical and laboratory examinations, a neurocognitive test battery, positron emission tomography (PET) with (11)C-Pittsburgh Compound-B (PiB; a measure of amyloid-ß (Aß) load) and (18)F-fluorodeoxyglucose (FDG; a proxy of neuronal activity), and completed semiquantitative food frequency questionnaires. SETTING: Research centre affiliated with the Alzheimer's disease Core Center at New York University School of Medicine. PARTICIPANTS: 49 NL individuals (age 25-72 years, 69% women) with dietary information, (11)C-PiB and (18)F-FDG PET scans were examined. RESULTS: Controlling for age and total caloric intake, higher intake of vitamin B12, vitamin D and ω-3 polyunsaturated fatty acid (PUFA) was associated with lower Aß load in AD regions on PiB-PET, while higher intake of ß-carotene and folate was associated with higher glucose metabolism on FDG-PET. ß-carotene and folate were associated with reduced glucose metabolism for women, apolipoprotein E epsilon 4 (APOE4) carriers and participants with positive AD family history, but not for their risk-free counterparts. The associations of vitamin B12, vitamin D and ω-3 PUFA with PiB retention were independent of gender, APOE and family history. The identified nutrient combination was associated with higher intake of vegetables, fruit, whole grains, fish and legumes, and lower intake of high-fat dairies, meat and sweets. CONCLUSIONS: Our data provide a potential pathophysiological mechanism for epidemiological findings showing that dietary interventions may play a role in the prevention of AD. Longitudinal studies are needed to determine whether there is a direct link between nutrient intake, brain biomarkers and risk of AD.

Brain imaging of cognitively normal individuals with 2 parents affected by late-onset AD.

OBJECTIVES: This brain imaging study examines whether cognitively normal (NL) individuals with 2 parents affected by late-onset Alzheimer disease (LOAD) show evidence of more extensive Alzheimer disease pathology compared with those who have a single parent affected by LOAD. METHODS: Fifty-two NL individuals received MRI, (11)C-Pittsburgh compound B (PiB)-PET, and (18)F-fluoro-2-deoxyglucose (FDG)-PET. These included 4 demographically balanced groups (n = 13/group, aged 32-72 years, 60% female, 30% APOE ε4 carriers) of NL individuals with maternal (FHm), paternal (FHp), and maternal and paternal (FHmp) family history of LOAD, and with negative family history (FH-). Statistical parametric mapping, voxel-based morphometry, and z-score mapping were used to compare MRI gray matter volumes (GMVs), partial volume-corrected PiB retention, and FDG metabolism across FH groups and vs FH-. RESULTS: NL FHmp showed more severe abnormalities in all 3 biomarkers vs the other groups regarding the number of regions affected and magnitude of impairment. PiB retention and hypometabolism were most pronounced in FHmp, intermediate in FHm, and lowest in FHp and FH-. GMV reductions were highest in FHmp and intermediate in FHm and FHp vs FH-. In all FH+ groups, amyloid-ß deposition exceeded GMV loss and hypometabolism exceeded GMV loss (p < 0.001), while amyloid-ß deposition exceeded hypometabolism in FHmp and FHp but not in FHm. CONCLUSIONS: These biomarker findings show a "LOAD parent-dose effect" in NL individuals several years, if not decades, before possible clinical symptoms.

Physical Activity, Mediterranean Diet and Biomarkers-Assessed Risk of Alzheimer's: A Multi-Modality Brain Imaging Study.

Increased physical activity and higher adherence to a Mediterranean-type diet (MeDi) have been independently associated with reduced risk of Alzheimer's disease (AD). Their association has not been investigated with the use of biomarkers. This study examines whether, among cognitively normal (NL) individuals, those who are less physically active and show lower MeDi adherence have brain biomarker abnormalities consistent with AD. METHODS: Forty-five NL individuals (age 54 ± 11, 71% women) with complete leisure time physical activity (LTA), dietary information, and cross-sectional 3D T1-weigthed MRI, 11C-Pittsburgh Compound B (PiB) and 18F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) scans were examined. Voxel-wise multivariate partial least square (PLS) regression was used to examine the effects of LTA, MeDi and their interaction on brain biomarkers. Age, gender, ethnicity, education, caloric intake, BMI, family history of AD, Apolipoprotein E (APOE) genotype, presence of hypertension and insulin resistance were examined as confounds. Subjects were dichotomized into more and less physically active (LTA+ vs. LTA-; n = 21 vs. 24), and into higher vs. lower MeDi adherence groups (n = 18 vs. 27) using published scoring methods. Spatial patterns of brain biomarkers that represented the optimal association between the images and the groups were generated for all modalities using voxel-wise multivariate Partial Least Squares (PLS) regression. RESULTS: Groups were comparable for clinical and neuropsychological measures. Independent effects of LTA and MeDi factors were observed in AD-vulnerable brain regions for all modalities (p < 0.001). Increased AD-burden (in particular higher Aß load and lower glucose metabolism) were observed in LTA- compared to LTA+ subjects, and in MeDi- as compared to MeDi+ subjects. A gradient effect was observed for all modalities so that LTA-/MeDi- subjects had the highest and LTA+/MeDi+ subjects had the lowest AD-burden (p < 0.001), although the LTA × MeDi interaction was significant only for FDG measures (p < 0.03). Adjusting for covariates did not attenuate these relationships. CONCLUSION: Lower physical activity and MeDi adherence were associated with increased brain AD-burden among NL individuals, indicating that lifestyle factors may modulate AD risk. Studies with larger samples and longitudinal evaluations are needed to determine the predictive power of the observed associations.

Amyloid and metabolic positron emission tomography imaging of cognitively normal adults with Alzheimer's parents.

This study examines the relationship between fibrillar beta-amyloid (Aß) deposition and reduced glucose metabolism, a proxy for neuronal dysfunction, in cognitively normal (NL) individuals with a parent affected by late-onset Alzheimer's disease (AD). Forty-seven 40-80-year-old NL received positron emission tomography (PET) with (11)C-Pittsburgh compound B (PiB) and 18F-fluoro-2-deoxy-d-glucose (FDG). These included 19 NL with a maternal history (MH), 12 NL with a paternal history (PH), and 16 NL with negative family history of AD (NH). Automated regions of interest, statistical parametric mapping, voxel-wise intermodality correlations, and logistic regressions were used to examine cerebral-to-cerebellar PiB and FDG standardized uptake value ratios across groups. The MH group showed higher PiB retention and lower metabolism in AD regions compared with NH and PH, which were negatively correlated in posterior cingulate, frontal, and parieto-temporal regions (Pearson r ≤ -0.57, p ≤ 0.05). No correlations were observed in NH and PH. The combination of Aß deposition and metabolism yielded accuracy ≥ 69% for MH vs. NH and ≥ 71% for MH vs. PH, with relative risk = 1.9-5.1 (p values < 0.005). NL individuals with AD-affected mothers show co-occurring Aß increases and hypometabolism in AD-vulnerable regions, suggesting an increased risk for AD.

Framingham cardiovascular risk profile correlates with impaired hippocampal and cortical vasoreactivity to hypercapnia.

Vascular risk factors affect cerebral blood flow (CBF) and cerebral vascular reactivity, contributing to cognitive decline. Hippocampus is vulnerable to both Alzheimer's disease (AD) pathology and ischemia; nonetheless, the information about the impact of vascular risk on hippocampal perfusion is minimal. Cognitively, healthy elderly (NL=18, 69.9±6.7 years) and subjects with mild cognitive impairment (MCI=15, 74.9±8.1 years) were evaluated for the Framingham cardiovascular risk profile (FCRP). All underwent structural imaging and resting CBF assessment with arterial spin labeling (ASL) at 3T magnetic resonance imaging (MRI). In 24 subjects (NL=17, MCI=7), CBF was measured after a carbon dioxide rebreathing challenge. Across all subjects, FCRP negatively correlated with hippocampal (ρ=-0.41, P=0.049) and global cortical (ρ=-0.46, P=0.02) vasoreactivity to hypercapnia (VR(h)). The FCRP-VR(h) relationships were most pronounced in the MCI group: hippocampus (ρ=-0.77, P=0.04); global cortex (ρ=-0.83, P=0.02). The FCRP did not correlate with either volume or resting CBF. The hippocampal VR(h) was lower in MCI than in NL subjects (Z=-2.0, P=0.047). This difference persisted after age and FCRP correction (F([3,20])=4.6, P=0.05). An elevated risk for vascular pathology is associated with a reduced response to hypercapnia in both hippocampal and cortical tissue. The VR(h) is more sensitive to vascular burden than either resting CBF or brain volume.

Increased fibrillar amyloid-{beta} burden in normal individuals with a family history of late-onset Alzheimer's.

Having a parent affected with late-onset Alzheimer's disease (LOAD) is a major risk factor among cognitively normal (NL) individuals. This (11)C-Pittsburgh Compound B (PiB)-PET study examines whether NL individuals with LOAD parents show increased fibrillar amyloid-beta (Abeta) deposition, a hallmark of Alzheimer's disease (AD) pathology and whether there are parent-of-origin effects. Forty-two 50- to 80-year-old NL persons were examined with PiB-PET. These individuals included 14 NL subjects with a maternal family history (FH) of LOAD (FHm), 14 NL subjects with a paternal FH (FHp), and 14 NL subjects with a negative family history of any dementia (FH-). Statistical parametric mapping and automated regions-of-interest were used to compare cerebral-to-cerebellar PiB standardized uptake value ratios, reflecting fibrillar Abeta burden, across groups. FH groups did not differ in age, gender, education, and apolipoprotein E (ApoE) status. NL FHm subjects showed higher PiB retention in AD-affected anterior and posterior cingulate cortex (PCC), precuneus, parietal, temporal, occipital, and frontal cortices, right basal ganglia, and thalamus, compared with FH- and FHp subjects. FHp subjects showed increased PiB retention in the PCC and frontal cortex, intermediate between FHm and FH- subjects. Results remained significant after controlling for age, gender, education, and ApoE status. Children of parents with LOAD, particularly those with affected mothers, have increased fibrillar Abeta load in AD-vulnerable regions compared with controls, perhaps accounting for the known increased risk for AD. Present findings may motivate further research on familial transmission and parent-of-origin effects in LOAD.

Subregional hippocampal atrophy predicts Alzheimer's dementia in the cognitively normal.

Atrophic changes of the hippocampus are typically regarded as an early sign of Alzheimer's dementia (AD). Using the radial distance atrophy mapping approach, we compared the longitudinal MRI data of 10 cognitively normal elderly subjects who remained normal at 3-year and 6-year follow-up (NL-NL) and 7 cognitively normal elderly subjects who were diagnosed with mild cognitive impairment (MCI) 2.8 (range 2.0-3.9) and with AD 6.8 years (range 6.1-8.2) after baseline (NL-MCI(AD)). 3D statistical maps revealed greater hippocampal atrophy in the NL-MCI(AD) relative to the NL-NL group at baseline (left p=0.05; right p=0.06) corresponding to 10-15% CA1, and 10-25% subicular atrophy, and bilateral differences at 3-year follow-up (left p=0.001, right p<0.02) corresponding to 10-30% subicular, 10-20% CA1, and 10-20% newly developed CA2-3 atrophy. This preliminary study suggests that excess CA1 and subicular atrophy is present in cognitively normal individuals predestined to decline to amnestic MCI, while progressive involvement of the CA1 and subiculum, and atrophy spreading to the CA2-3 subfield in amnestic MCI, suggests future diagnosis of AD.

Magnetic resonance imaging improves cerebrospinal fluid biomarkers in the early detection of Alzheimer's disease.

Little is known of combined utility of magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) biomarkers for prediction of Alzheimer's disease (AD) and longitudinal data is scarce. We examined these biomarkers at baseline and longitudinally in incipient AD. Forty-five subjects [21 controls (NL-NL), 16 stable MCI (MCI-MCI), 8 MCI who declined to AD (MCI-AD)] received MRI and lumbar puncture at baseline and after 2 years. CSF measures included total and phosphorylated tau (T-tau, P-tau(231)), amyloid-beta (Abeta(42)/Abeta(40)) and isoprostane. Voxel-based morphometry identified gray matter concentration (GMC) differences best distinguishing study groups and individual GMC values were calculated. Rate of medial temporal lobe (MTL) atrophy was examined using regional boundary shift (rBS) method. At baseline, for MRI, MCI-AD showed reduced GMC-MTL, and for CSF higher CSF T-tau, P-tau(231), IP and lower Abeta(42)/Abeta(40) as compared with MCI-MCI or NL-NL. Longitudinally, rBS-MTL atrophy was higher in MCI-AD than in either MCI-MCI or NL-NL, particularly in the left hemisphere. CSF data showed longitudinally greater increases of isoprostane in MCI-AD as compared with NL-NL. Combining baseline CSF-P-tau(231) and GMC-MTL significantly increased overall prediction of AD from 74% to 84% (p(step)<0.05). These results provide support for including multiple modalities of biomarkers in the identification of memory clinic patients at increased risk for dementia.

Multicenter standardized 18F-FDG PET diagnosis of mild cognitive impairment, Alzheimer's disease, and other dementias.

UNLABELLED: This multicenter study examined (18)F-FDG PET measures in the differential diagnosis of Alzheimer's disease (AD), frontotemporal dementia (FTD), and dementia with Lewy bodies (DLB) from normal aging and from each other and the relation of disease-specific patterns to mild cognitive impairment (MCI). METHODS: We examined the (18)F-FDG PET scans of 548 subjects, including 110 healthy elderly individuals ("normals" or NLs), 114 MCI, 199 AD, 98 FTD, and 27 DLB patients, collected at 7 participating centers. Individual PET scans were Z scored using automated voxel-based comparison with generation of disease-specific patterns of cortical and hippocampal (18)F-FDG uptake that were then applied to characterize MCI. RESULTS: Standardized disease-specific PET patterns were developed that correctly classified 95% AD, 92% DLB, 94% FTD, and 94% NL. MCI patients showed primarily posterior cingulate cortex and hippocampal hypometabolism (81%), whereas neocortical abnormalities varied according to neuropsychological profiles. An AD PET pattern was observed in 79% MCI with deficits in multiple cognitive domains and 31% amnesic MCI. (18)F-FDG PET heterogeneity in MCI with nonmemory deficits ranged from absent hypometabolism to FTD and DLB PET patterns. CONCLUSION: Standardized automated analysis of (18)F-FDG PET scans may provide an objective and sensitive support to the clinical diagnosis in early dementia.

A non-toxic ligand for voxel-based MRI analysis of plaques in AD transgenic mice.

Amyloid plaques are a characteristic feature in Alzheimer's disease (AD). A novel non-toxic contrast agent is presented, Gd-DTPA-K6Abeta1-30, which is homologous to Abeta, and allows plaque detection in vivo. microMRI was performed on AD model mice and controls prior to and following intracarotid injection with Gd-DTPA-K6Abeta1-30 in mannitol solution, to transiently open the blood-brain barrier. A gradient echo T2(*)-weighted sequence was used to provide 100 microm isotropic resolution with imaging times of 115 min. The scans were examined with voxel-based analysis (VBA) using statistical parametric mapping, for un-biased quantitative comparison of ligand-injected mice and controls. The results indicate that: (1) Gd-DTPA-K6Abeta1-30 is an effective, non-toxic, ligand for plaque detection when combined with VBA (p< or =0.01-0.001), comparing pre and post-ligand injection scans. (2) Large plaques can be detected without the use of a contrast agent and this detection co-localizes with iron deposition. (3) Smaller, earlier plaques require contrast ligand for MRI visualization. Our ligand when combined with VBA may be useful for following therapeutic approaches targeting amyloid in transgenic mouse models.

Hypometabolism and altered cerebrospinal fluid markers in normal apolipoprotein E E4 carriers with subjective memory complaints.

BACKGROUND: We examined whether cerebral metabolic rates for glucose (CMRglc) on 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) and cerebrospinal fluid (CSF) markers of Alzheimer's disease (AD) are altered in cognitively normal apolipoprotein E (ApoE) E4 carriers with subjective memory complaints (SMC). METHODS: Twenty-eight middle-aged normal subjects (NL) were examined, including 13 E4 carriers (E4+; 6 with SMC [SMC+] and 7 without SMC [SMC-]) and 15 noncarriers (E4-; 7 SMC+ and 8 SMC-). Subjects received an FDG-PET scan and a lumbar puncture to measure CSF total (T-Tau) and hyperphosphorylated tau(231) (P-Tau), 40 and 42 amino acid forms of beta-amyloid (Abeta40 and Abeta42), and F(2)-isoprostane (IP). RESULTS: As compared with E4-, E4+ subjects showed decreased CMRglc in AD-related brain regions and associated higher CSF IP, P-Tau, T-Tau, and P-Tau/Abeta42 levels (p's < .05). As compared with SMC-, SMC+ subjects showed reduced parietotemporal and parahippocampal gyrus (PHG) CMRglc. A significant ApoE by SMC status interaction was found, with the E4+/SMC+ showing the lowest PHG CMRglc and the highest CSF IP, P-Tau, and P-Tau/Abeta42 levels as compared with all other subgroups (p's < or = .05). The combination of CSF and CMRglc measures significantly improved the accuracy of either measures alone in discriminating ApoE groups (86% accuracy, odds ratio [OR] = 4.1, p < .001) and E4+/SMC+ from all other subgroups (86% accuracy, OR = 3.7, p = .005). Parahippocampal gyrus CMRglc was the most accurate discriminator of SMC groups (75% accuracy, OR = 2.4, p < .001). CONCLUSIONS: Normal E4 carriers with SMC show altered AD-related CSF and FDG-PET measures. Longitudinal studies are needed to assess whether these brain abnormalities foreshadow clinical decline.

Quantitation, regional vulnerability, and kinetic modeling of brain glucose metabolism in mild Alzheimer's disease.

PURPOSE: To examine CMRglc measures and corresponding glucose transport (K1 and k2) and phosphorylation (k3) rates in the medial temporal lobe (MTL, comprising the hippocampus and amygdala) and posterior cingulate cortex (PCC) in mild Alzheimer's disease (AD). METHODS: Dynamic FDG PET with arterial blood sampling was performed in seven mild AD patients (age 68+/-8 years, four females, median MMSE 23) and six normal (NL) elderly (age 69+/-9 years, three females, median MMSE 30). Absolute CMRglc (micromol/100 g/min) was calculated from MRI-defined regions of interest using multiparametric analysis with individually fitted kinetic rate constants, Gjedde-Patlak plot, and Sokoloff's autoradiographic method with population-based rate constants. Relative ROI/pons CMRglc (unitless) was also examined. RESULTS: With all methods, AD patients showed significant CMRglc reductions in the hippocampus and PCC, and a trend towards reduced parietotemporal CMRglc, as compared with NL. Significant k3 reductions were found in the hippocampus, PCC and amygdala. K1 reductions were restricted to the hippocampus. Relative CMRglc had the largest effect sizes in separating AD from NL. However, the magnitude of CMRglc reductions was 1.2- to 1.9-fold greater with absolute than with relative measures. CONCLUSION: CMRglc reductions are most prominent in the MTL and PCC in mild AD, as detected with both absolute and relative CMRglc measures. Results are discussed in terms of clinical and pharmaceutical applicability.