Alzheimer's and neurodegenerative disease biomarkers in blood predict brain atrophy and cognitive decline.

BACKGROUND: Although blood-based biomarkers have been identified as cost-effective and scalable alternatives to PET and CSF markers of neurodegenerative disease, little is known about how these biomarkers predict future brain atrophy and cognitive decline in cognitively unimpaired individuals. Using data from the Baltimore Longitudinal Study of Aging (BLSA), we examined whether plasma biomarkers of Alzheimer's disease (AD) pathology (amyloid-ß [Aß42/40], phosphorylated tau [pTau-181]), astrogliosis (glial fibrillary acidic protein [GFAP]), and neuronal injury (neurofilament light chain [NfL]) were associated with longitudinal brain volume loss and cognitive decline. Additionally, we determined whether sex, APOEε4 status, and plasma amyloid-ß status modified these associations. METHODS: Plasma biomarkers were measured using Quanterix SIMOA assays. Regional brain volumes were measured by 3T MRI, and a battery of neuropsychological tests assessed five cognitive domains. Linear mixed effects models adjusted for demographic factors, kidney function, and intracranial volume (MRI analyses) were completed to relate baseline plasma biomarkers to baseline and longitudinal brain volume and cognitive performance. RESULTS: Brain volume analyses included 622 participants (mean age ± SD: 70.9 ± 10.2) with an average of 3.3 MRI scans over 4.7 years. Cognitive performance analyses included 674 participants (mean age ± SD: 71.2 ± 10.0) with an average of 3.9 cognitive assessments over 5.7 years. Higher baseline pTau-181 was associated with steeper declines in total gray matter volume and steeper regional declines in several medial temporal regions, whereas higher baseline GFAP was associated with greater longitudinal increases in ventricular volume. Baseline Aß42/40 and NfL levels were not associated with changes in brain volume. Lower baseline Aß42/40 (higher Aß burden) was associated with a faster decline in verbal memory and visuospatial performance, whereas higher baseline GFAP was associated with a faster decline in verbal fluency. Results were generally consistent across sex and APOEε4 status. However, the associations of higher pTau-181 with increasing ventricular volume and memory declines were significantly stronger among individuals with higher Aß burden, as was the association of higher GFAP with memory decline. CONCLUSIONS: Among cognitively unimpaired older adults, plasma biomarkers of AD pathology (pTau-181) and astrogliosis (GFAP), but not neuronal injury (NfL), serve as markers of future brain atrophy and cognitive decline.

Association of Plasma Markers of Alzheimer's Disease, Neurodegeneration, and Neuroinflammation with the Choroid Plexus Integrity in Aging.

The choroid plexus (CP) is a vital brain structure essential for cerebrospinal fluid (CSF) production. Moreover, alterations in the CP's structure and function are implicated in molecular conditions and neuropathologies including multiple sclerosis, Alzheimer's disease, and stroke. Our goal is to provide the first characterization of the association between variation in the CP microstructure and macrostructure/volume using advanced magnetic resonance imaging (MRI) methodology, and blood-based biomarkers of Alzheimer's disease (Aß42/40 ratio; pTau181), neuroinflammation and neuronal injury (GFAP; NfL). We hypothesized that plasma biomarkers of brain pathology are associated with disordered CP structure. Moreover, since cerebral microstructural changes can precede macrostructural changes, we also conjecture that these differences would be evident in the CP microstructural integrity. Our cross-sectional study was conducted on a cohort of 108 well-characterized individuals, spanning 22-94 years of age, after excluding participants with cognitive impairments and non-exploitable MR imaging data. Established automated segmentation methods were used to identify the CP volume/macrostructure using structural MR images, while the microstructural integrity of the CP was assessed using our advanced quantitative high-resolution MR imaging of longitudinal and transverse relaxation times (T1 and T2). After adjusting for relevant covariates, positive associations were observed between pTau181, NfL and GFAP and all MRI metrics. These associations reached significance (p<0.05) except for CP volume vs. pTau181 (p=0.14), CP volume vs. NfL (p=0.35), and T2 vs. NFL (p=0.07). Further, negative associations between Aß42/40 and all MRI metrics were observed but reached significance only for Aß42/40 vs. T2 (p=0.04). These novel findings demonstrate that reduced CP macrostructural and microstructural integrity is positively associated with blood-based biomarkers of AD pathology, neurodegeneration/neuroinflammation and neurodegeneration. Degradation of the CP structure may co-occur with AD pathology and neuroinflammation ahead of clinically detectable cognitive impairment, making the CP a potential structure of interest for early disease detection or treatment monitoring.

Skeletal muscle mitochondrial function predicts cognitive impairment and is associated with biomarkers of Alzheimer's disease and neurodegeneration.

INTRODUCTION: Mitochondrial dysfunction is implicated in the pathophysiology of many chronic diseases. Whether it is related to cognitive impairment and pathological markers is unknown. METHODS: We examined the associations of in vivo skeletal muscle mitochondrial function (post-exercise recovery rate of phosphocreatine [kPCr] via magnetic resonance [MR] spectroscopy with future mild cognitive impairment (MCI) or dementia, and with positron emission tomography (PET) and blood biomarkers of Alzheimer's disease [AD] and neurodegeneration (i.e., Pittsburgh Compound-B [PiB] distribution volume ratio [DVR] for amyloid beta [Aß], flortaucipir (FTP) standardized uptake value ratio [SUVR] for tau, Aß42 /40 ratio, phosphorylated tau 181 [p-tau181], neurofilament light chain [NfL], and glial fibrillary acidic protein [GFAP]). RESULTS: After covariate adjustment, each standard deviation (SD) higher kPCr level was associated with 52% lower hazards of developing MCI/dementia, and with 59% lower odds of being PiB positive with specific associations in DVR of frontal, parietal, and temporal regions, and cingulate cortex and pallidum. Higher kPCr level was also associated with lower plasma GFAP. DISCUSSION: In aging, mitochondrial dysfunction may play a vital role in AD pathological changes and neuroinflammation. Highlights Higher in vivo mitochondrial function is related to lower risk of mild cognitive impairment (MCI)/dementia. Higher in vivo mitochondrial function is related to lower amyloid tracer uptake. Higher in vivo mitochondrial function is related to lower plasma neuroinflammation. Mitochondrial dysfunction may play a key role in Alzheimer's disease (AD) and neurodegeneration.

The association between personality and plasma biomarkers of astrogliosis and neuronal injury.

Personality traits have been associated with the risk of dementia and Alzheimer's disease neuropathology, including amyloid and tau. This study examines whether personality traits are concurrently related to plasma glial fibrillary acidic protein (GFAP), a marker of astrogliosis, and neurofilament light (NfL), a marker of neuronal injury. Cognitively unimpaired participants from the Baltimore Longitudinal Study on Aging (N = 786; age: 22-95) were assayed for plasma GFAP and NfL and completed the Revised NEO Personality Inventory, which measures 5 domains and 30 facets of personality. Neuroticism (particularly vulnerability to stress, anxiety, and depression) was associated with higher GFAP and NfL. Conscientiousness was associated with lower GFAP. Extraversion (particularly positive emotions, assertiveness, and activity) was related to lower GFAP and NfL. These associations were independent of demographic, behavioral, and health covariates and not moderated by age, sex, or apolipoprotein E genotype. The personality correlates of astrogliosis and neuronal injury tend to be similar, are found in individuals without cognitive impairment, and point to potential neurobiological underpinnings of the association between personality traits and neurodegenerative diseases.

Longitudinal changes in Alzheimer's-related plasma biomarkers and brain amyloid.

INTRODUCTION: Understanding longitudinal plasma biomarker trajectories relative to brain amyloid changes can help devise Alzheimer's progression assessment strategies. METHODS: We examined the temporal order of changes in plasma amyloid-ß ratio ( A ß 42 / A ß 40 ${{\rm A}\beta }_{42}/{{\rm A}\beta }_{40}$ ), glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), and phosphorylated tau ratios ( p-tau181 / A ß 42 $\text{p-tau181}/\mathrm{A}{\beta}_{42}$ , p-tau231 / A ß 42 $\text{p-tau231}/\mathrm{A}{\beta}_{42}$ ) relative to 11 C-Pittsburgh compound B (PiB) positron emission tomography (PET) cortical amyloid burden (PiB-/+). Participants (n = 199) were cognitively normal at index visit with a median 6.1-year follow-up. RESULTS: PiB groups exhibited different rates of longitudinal change in A ß 42 / A ß 40 ( ß = 5.41 × 10 - 4 , SE = 1.95 × 10 - 4 , p = 0.0073 ) ${{\rm A}\beta }_{42}/{{\rm A}\beta }_{40}\ ( {\beta \ = \ 5.41 \times {{10}}^{ - 4},{\rm{\ SE\ }} = \ 1.95 \times {{10}}^{ - 4},\ p\ = \ 0.0073} )$ . Change in brain amyloid correlated with change in GFAP (r = 0.5, 95% CI = [0.26, 0.68]). The greatest relative decline in A ß 42 / A ß 40 ${{\rm A}\beta }_{42}/{{\rm A}\beta }_{40}$ (-1%/year) preceded brain amyloid positivity by 41 years (95% CI = [32, 53]). DISCUSSION: Plasma A ß 42 / A ß 40 ${{\rm A}\beta }_{42}/{{\rm A}\beta }_{40}$ may begin declining decades prior to brain amyloid accumulation, whereas p-tau ratios, GFAP, and NfL increase closer in time. HIGHLIGHTS Plasma A ß 42 / A ß 40 ${{\rm A}\beta }_{42}/{{\rm A}\beta }_{40}$ declines over time among PiB- but does not change among PiB+. Phosphorylated-tau to Aß42 ratios increase over time among PiB+ but do not change among PiB-. Rate of change in brain amyloid is correlated with change in GFAP and neurofilament light chain. The greatest decline in A ß 42 / A ß 40 ${{\rm A}\beta }_{42}/{{\rm A}\beta }_{40}$ may precede brain amyloid positivity by decades.

MRI and fluid biomarkers reveal determinants of myelin and axonal loss with aging.

OBJECTIVE: White matter damage is a feature of Alzheimer's disease, yet little is known about how facets of the Alzheimer's disease process relate to key features of white matter structure. We examined the association of Alzheimer's disease (Aß42/40 ratio; pTau181), neuronal injury (NfL), and reactive astrogliosis (GFAP) biomarkers with MRI measures of myelin content and axonal density. METHODS: Among cognitively normal participants in the BLSA and GESTALT studies who received MRI measures of myelin content (defined by myelin water fraction [MWF]) and axonal density (defined by neurite density index [NDI]), we quantified plasma levels of Aß42 , Aß40 , pTau181, NfL, and GFAP. Linear regression models adjusted for demographic variables were used to relate these plasma biomarker levels to the MRI measures. RESULTS: In total, 119 participants received MWF imaging (age: 56 [SD 21]), of which 43 received NDI imaging (age: 50 [SD 18]). We found no relationship between plasma biomarkers and total brain myelin content. However, secondary analysis found higher GFAP was associated with lower MWF in the temporal lobes (ß = -0.13; P = 0.049). Further, higher levels of NfL (ß = -0.22; P = 0.009) and GFAP (ß = -0.29; P = 0.002) were associated with lower total brain axonal density. Secondary analyses found lower Aß42/40 ratio and higher pTau181 were also associated with lower axonal density, but only in select brain regions. These results remained similar after additionally adjusting for cardiovascular risk factors. INTERPRETATION: Plasma biomarkers of neuronal injury and astrogliosis are associated with reduced axonal density and region-specific myelin content. Axonal loss and demyelination may co-occur with neurodegeneration and astrogliosis ahead of clinically meaningful cognitive decline.

Cognitive impairment in chronic migraine compared to pseudotumor cerebri.

INTRODUCTION: We aimed to define the prevalence of objective cognitive impairment in a group of chronic migraineurs, and to define how migraineurs with cognitive impairment differed from those without impairment, and in doing so to compare cognitive impairment in chronic migraine to another chronic headache-related disorder already associated with cognitive impairment (i.e. pseudotumor cerebri syndrome). OBJECTIVES: Cognitive impairment in migraine, especially chronic migraine, has been too little studied. Only a few studies have been done, demonstrating that cognitive impairment exists in chronic migraineurs. It is not known how this compares to other headache-related conditions. MATERIAL AND METHODS: We administered a cognitive battery consisting of the National Adult Reading Test, Mini-Mental Status Examination, Digit Span, Boston Naming Test, Rey Auditory Verbal Learning Test, Trail Making Test, Controlled Oral Word Association, and Category Fluency. Cognitive impairment was defined as mild single-domain with one test score, and mild multi- -domain with two scores more than two standard deviations below the mean for age-, gender-, and education-adjusted norms. The data from this study was compared to our previously published population of patients with pseudotumor cerebri syndrome. RESULTS: One hundred prospectively recruited patients with chronic migraine were enrolled. Fifty-seven patients had normal cognitive profiles. Forty-three patients demonstrated mild cognitive impairment, and more than half (n = 24) showed impairment in multiple cognitive domains. Migraineurs with multi-domain impairment had higher pain intensity, shorter duration of disease, were taking narcotics, had more impaired vision-related mental health scores, and worse social health scores. We found an association between objective cognitive impairment and subjective perception of impairment only when controlling for pain. We found no associations with depression and topiramate use. The mean composite cognitive Z score was no different in chronic migraineurs and patients with pseudotumor cerebri. CONCLUSIONS AND CLINICAL IMPLICATIONS: Most chronic migraineurs have normal cognitive profiles, but a large proportion of them do experience mild cognitive impairment, especially in multiple domains. The impairment seen in migraine is similar to that in pseudotumor cerebri syndrome, which has already been associated with mild cognitive impairment. Cognitively impaired migraineurs are different from non-impaired/less impaired migraineurs in several ways, which may be an important factor in influencing their migraine treatment.

Longitudinal changes in Alzheimer's-related plasma biomarkers and brain amyloid.

INTRODUCTION: Understanding longitudinal plasma biomarker trajectories relative to brain amyloid changes can help devise Alzheimer's progression assessment strategies. METHODS: We examined the temporal order of changes in plasma amyloid-ß ratio (Aß 42 /Aß 40 ), glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), and phosphorylated tau ratios (p-tau181/Aß 42 , p-tau231/Aß 42 ) relative to 11 C-Pittsburgh compound B (PiB) positron emission tomography (PET) cortical amyloid burden (PiB-/+). Participants (n = 199) were cognitively normal at index visit with a median 6.1-year follow-up. RESULTS: PiB groups exhibited different rates of longitudinal change in Aß 42 /Aß 40 (ß = 5.41 × 10^ -4 , SE = 1.95 × 10 -4 , p = 0.0073). Change in brain amyloid was correlated with change in GFAP (r = 0.5, 95% CI = [0.26, 0.68]). Greatest relative decline in Aß 42 /Aß 40 (-1%/year) preceded brain amyloid positivity onset by 41 years (95% CI = [32, 53]). DISCUSSION: Plasma Aß 42 /Aß 40 may begin declining decades prior to brain amyloid accumulation, whereas p-tau ratios, GFAP, and NfL increase closer in time.

Association of liver disease with brain volume loss, cognitive decline, and plasma neurodegenerative disease biomarkers.

Although liver dysfunction has been implicated in Alzheimer's disease (AD), it remains unknown how liver disease may influence the trajectory of brain and cognitive changes in older adults. We related self-reported liver disease to longitudinal measures of brain structure and cognition, as well as baseline measures of plasma AD/neurodegeneration biomarkers in the Baltimore Longitudinal Study of Aging. Liver disease was identified using ICD-9 classification codes. Brain volume and cognition were assessed serially using 3T-MRI and a cognitive battery. 1008, 2157, and 780 participants were included in the MRI, cognitive, and plasma biomarker analysis, respectively. After adjustment for confounders, liver disease was associated with accelerated decline in total brain and white matter volume, but not total gray matter or AD signature region volume. Although liver disease showed no relationship with domain-specific cognitive decline or plasma biomarkers, participants with a history of hepatitis demonstrated accelerated decline in verbal fluency and elevated neurofilament light. Results suggest all-cause liver disease may accelerate brain volume loss but does not appear to promote AD-specific neurocognitive changes.

Causal links among amyloid, tau, and neurodegeneration.

Amyloid-ß pathology is associated with greater tau pathology and facilitates tau propagation from the medial temporal lobe to the neocortex, where tau is closely associated with local neurodegeneration. The degree of the involvement of amyloid-ß versus existing tau pathology in tau propagation and neurodegeneration has not been fully elucidated in human studies. Careful quantification of these effects can inform the development and timing of therapeutic interventions. We conducted causal mediation analyses to investigate the relative contributions of amyloid-ß and existing tau to tau propagation and neurodegeneration in two longitudinal studies of individuals without dementia: the Baltimore Longitudinal Study of Aging (N = 103, age range 57-96) and the Alzheimer's Disease Neuroimaging Initiative (N = 122, age range 56-92). As proxies of neurodegeneration, we investigated cerebral blood flow, glucose metabolism, and regional volume. We first confirmed that amyloid-ß moderates the association between tau in the entorhinal cortex and in the inferior temporal gyrus, a neocortical region exhibiting early tau pathology (amyloid group × entorhinal tau interaction term ß = 0.488, standard error [SE] = 0.126, P < 0.001 in the Baltimore Longitudinal Study of Aging; ß = 0.619, SE = 0.145, P < 0.001 in the Alzheimer's Disease Neuroimaging Initiative). In causal mediation analyses accounting for this facilitating effect of amyloid, amyloid positivity had a statistically significant direct effect on inferior temporal tau as well as an indirect effect via entorhinal tau (average direct effect =0.47, P < 0.001 and average causal mediation effect =0.44, P = 0.0028 in Baltimore Longitudinal Study of Aging; average direct effect =0.43, P = 0.004 and average causal mediation effect =0.267, P = 0.0088 in Alzheimer's Disease Neuroimaging Initiative). Entorhinal tau mediated up to 48% of the total effect of amyloid on inferior temporal tau. Higher inferior temporal tau was associated with lower colocalized cerebral blood flow, glucose metabolism, and regional volume, whereas amyloid had only an indirect effect on these measures via tau, implying tau as the primary driver of neurodegeneration (amyloid-cerebral blood flow average causal mediation effect =-0.28, P = 0.021 in Baltimore Longitudinal Study of Aging; amyloid-volume average causal mediation effect =-0.24, P < 0.001 in Alzheimer's Disease Neuroimaging Initiative). Our findings suggest targeting amyloid or medial temporal lobe tau might slow down neocortical spread of tau and subsequent neurodegeneration, but a combination therapy may yield better outcomes.

Olfaction, Cognitive Impairment, and PET Biomarkers in Community-Dwelling Older Adults.

BACKGROUND: Olfactory deficits are early features of preclinical Alzheimer's disease (AD). Whether olfaction is associated with PET biomarkers among community-dwelling older adults is less clear. OBJECTIVE: Investigate cross-sectional and longitudinal associations of olfaction with mild cognitive impairment (MCI) and amyloid-ß (Aß) and tau deposition. METHODS: We analyzed 364 initially cognitively normal participants (58% women, 24% black) who had baseline olfaction data and subsequent cognitive assessments during an average 2.4-year. A subset of 129 had PET-PiB (Aß) (n = 72 repeated) and 105 had 18F-flortaucipir (FTP)-PET (tau) (n = 44 repeated). Olfaction was measured using a 16-item Sniffin' Sticks Odor Identification Test. The association of olfaction with incident MCI was examined using Cox regression. Associations with PiB-distribution volume ratio (DVR) and FTP-standardized uptake value ratio (SUVR) were examined using partial correlation. We tested whether PiB+/-status modified these associations. Analyses were adjusted for demographics and olfactory test version. RESULTS: 17 (5%) participants developed MCI. Each unit lower odor identification score was associated with 22% higher risk of developing MCI (p = 0.04). In the PET subset, lower scores were associated with higher mean cortical DVR and DVR in orbitofrontal cortex (OFC), precuneus, and middle temporal gyrus (p≤0.04). The "olfaction*PiB+/-" interaction in OFC DVR was significant (p = 0.03), indicating the association was limited to PiB positive individuals. Greater decline in odor identification score was associated with greater increase in anterior OFC DVR and entorhinal tau SUVR (p≤0.03). CONCLUSION: Among community-dwelling older adults, poorer olfaction predicts incident MCI and is associated with overall and regional Aß. Greater olfaction decline is associated with faster Aß and tau accumulation in olfaction-related regions. Whether olfaction predicts AD-related neurodegenerative changes warrants further investigations.

Personality Associations With Amyloid and Tau: Results From the Baltimore Longitudinal Study of Aging and Meta-analysis.

BACKGROUND: Higher neuroticism and lower conscientiousness are risk factors for Alzheimer's disease and related dementias, but the underlying neuropathological correlates remain unclear. Our aim was to examine whether personality traits are associated with amyloid and tau neuropathology in a new sample and meta-analyses. METHODS: Participants from the BLSA (Baltimore Longitudinal Study of Aging) completed the Revised NEO Personality Inventory and underwent amyloid (11C-labeled Pittsburgh compound B) and tau (18F-flortaucipir) positron emission tomography. RESULTS: Among cognitively normal BLSA participants, neuroticism was associated with higher cortical amyloid burden (odds ratio 1.68, 95% CI 1.20-2.34), and conscientiousness was associated with lower cortical amyloid burden (odds ratio 0.61, 95% CI 0.44-0.86). These associations remained significant after accounting for age, sex, education, depressive symptoms, hippocampal volume, and APOE ε4. Similar associations were found with tau in the entorhinal cortex. Random-effects meta-analyses of 12 studies found that higher neuroticism (N = 3015, r = 0.07, p = .008) and lower conscientiousness (N = 2990, r = -0.11, p < .001) were associated with more amyloid deposition. Meta-analyses of 8 studies found that higher neuroticism (N = 2231, r = 0.15, p < .001) and lower conscientiousness (N = 2206, r = -0.14, p < .001) were associated with more tau pathology. The associations were moderated by cognitive status, with stronger effects in cognitively normal compared with heterogeneous samples, suggesting that the associations between personality and proteopathies are not phenomena that emerge with neuropsychiatric clinical symptoms. CONCLUSIONS: By aggregating results across samples, this study advances knowledge on the association between personality and neuropathology. Neuroticism and conscientiousness may contribute to resistance against amyloid and tau neuropathology.

Development of a novel method for the quantification of tyrosine 39 phosphorylated α- and ß-synuclein in human cerebrospinal fluid.

BACKGROUND: Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder. Biomarkers that can help monitor the progression of PD or response to disease-modifying agents will be invaluable in making appropriate therapeutic decisions. Further, biomarkers that could be used to distinguish PD from other related disorders with PD-like symptoms will be useful for accurate diagnosis and treatment. C-Abl tyrosine kinase is activated in PD resulting in increased phosphorylation of the tyrosine residue at position 39 (Y39) of α-synuclein (α-syn) (pY39 α-syn), which contributes to the death of dopaminergic neurons. Because pY39 α-syn may be pathogenic, monitoring pY39 α-syn could allow us to diagnose presymptomatic PD and help monitor disease progression and response to treatment. We sought to investigate if increased phosphorylation of pY39 α-syn can be detected in the cerebrospinal fluid (CSF) of PD patients by targeted mass spectrometry. METHODS: Here, we report a two-step enrichment method in which phosphotyrosine peptides were first enriched with an anti-phosphotyrosine antibody followed by a second round of enrichment by titanium dioxide (TiO2) beads to detect EGVLpYVGSK sequence derived from tyrosine 39 region of α- and ß-synuclein (αß-syn). Accurate quantification was achieved by adding a synthetic heavy version of pY39 αß-syn peptide before enzymatic digestion. RESULTS: Using the developed enrichment methods and optimized parallel reaction monitoring (PRM) assays, we detected pY39 αß-syn peptide in human CSF and demonstrated that the ratio of pY39 αß-syn to Y39 αß-syn was significantly increased in the CSF of patients with PD. CONCLUSIONS: We anticipate that this optimized two-step enrichment-based PRM detection method will help monitor c-Abl activation in PD patients and can also be used to quantify other phosphotyrosine peptides of low abundance in biological samples.

Association of peripheral inflammatory markers with connectivity in large-scale functional brain networks of non-demented older adults.

BACKGROUND: Systemic inflammation has emerged as a risk factor for cognitive decline and Alzheimer's disease, but inflammation's effect on distributed brain networks is unclear. We examined the relationship between peripheral inflammatory markers and subsequent functional connectivity within five large-scale cognitive networks and evaluated the modifying role of cortical amyloid and APOE ε4 status. METHODS: Blood levels of soluble tumor necrosis factor-alpha receptor-1 and interleukin 6 were assessed in 176 participants (at baseline mean age: 65 (SD 9) years; 63% women; 85% cognitively normal, 15% mild cognitive impairment (MCI)) and were combined to derive an Inflammatory Index. Approximately six years later, participants underwent resting-state functional magnetic resonance imaging to quantify functional connectivity; a subset of 137 participants also underwent 11C Pittsburgh compound-B (PiB) PET imaging to assess cortical amyloid burden. RESULTS: Using linear regression models adjusted for demographic characteristics and cardiovascular risk factors, a higher Inflammatory Index was associated with lower connectivity within the Default Mode (ß = -0.013; 95% CI: -0.023, -0.003) and the Dorsal Attention Networks (ß = -0.017; 95% CI: -0.028, -0.006). The strength of these associations did not vary by amyloid status (positive/negative). However, there was a significant interaction between Inflammatory Index and APOE ε4 status, whereby ε4-positive participants with a higher Inflammatory Index demonstrated lower connectivity. Inflammatory Index was unrelated to connectivity within other large-scale cognitive networks (Control, Limbic, and Salience/Ventral Attention networks). CONCLUSION: Peripheral pro-inflammatory signaling in older adults without dementia, especially among APOE ε4-positive individuals, is associated with altered connectivity within two large-scale cognitive networks.

Plasma Markers of Inflammation Linked to Clinical Progression and Decline During Preclinical AD.

OBJECTIVE: To examine the prospective association between blood biomarkers of immune functioning (i.e., innate immune activation, adaptive immunity, and inflammation) and subsequent cognitive decline and clinical progression to mild cognitive impairment (MCI) in cognitively normal individuals. METHODS: The BIOCARD study is an observational cohort study of N = 191 initially cognitively healthy participants (mean age 65.2 years). Blood plasma samples were assayed for markers of chronic inflammation (TNFR1, IL-6), adaptive immunity (CD25), and innate immune activation (CD14 and CD163). Participants were followed annually for ongoing clinical assessment and cognitive testing for up to 7.3 years. Primary study outcomes were progression to MCI and cognitive change over time, as measured by a global factor score encompassing multiple cognitive domains. RESULTS: Higher levels of plasma TNFR1 were associated with greater risk of progression from normal cognition to MCI (HR: 3.27; 95% confidence interval, CI: 1.27, 8.40). Elevated levels of TNFR1 were also associated with steeper rate of cognitive decline on follow-up but not with baseline cognitive performance. Baseline IL-6 levels and markers of innate and adaptive immune activation showed no relationship with MCI risk or cognitive decline. CONCLUSION: Inflammation, mediated by TNF signaling, may play a selective role in the early phase of AD. Accordingly, plasma TNFR1 may facilitate improved prediction of disease progression for individuals in the preclinical stage of AD.

Neuropathologic, genetic, and longitudinal cognitive profiles in primary age-related tauopathy (PART) and Alzheimer's disease.

INTRODUCTION: Primary age-related tauopathy (PART) is a recently described entity that can cause cognitive impairment in the absence of Alzheimer's disease (AD). Here, we compared neuropathological features, tau haplotypes, apolipoprotein E (APOE) genotypes, and cognitive profiles in age-matched subjects with PART and AD pathology. METHODS: Brain autopsies (n = 183) were conducted on participants 85 years and older from the Baltimore Longitudinal Study of Aging and Johns Hopkins Alzheimer's Disease Research Center. Participants, normal at enrollment, were followed with periodic cognitive evaluations until death. RESULTS: Compared with AD, PART subjects showed significantly slower rates of decline on measures of memory, language, and visuospatial performance. They also showed lower APOE ε4 allele frequency (4.1% vs. 17.6%, P = .0046). DISCUSSION: Our observations suggest that PART is separate from AD and its distinction will be important for the clinical management of patients with cognitive impairment and for public health care planning.

Hypothetical Preclinical Alzheimer Disease Groups and Longitudinal Cognitive Change.

IMPORTANCE: Clinical trials testing treatments for Alzheimer disease (AD) are increasingly focused on cognitively normal individuals in the preclinical phase of the disease. To optimize observing a treatment effect, such trials need to enroll cognitively normal individuals likely to show cognitive decline over the duration of the trial. OBJECTIVE: To identify which group of cognitively normal individuals shows the greatest cognitive decline over time based on their cerebrospinal fluid biomarker profile. DESIGN, SETTING, AND PARTICIPANTS: In this cohort study, cognitively normal participants were classified into 1 of the following 4 hypothetical preclinical AD groups using baseline cerebrospinal fluid levels of Aß and tau or Aß and phosphorylated tau (p-tau): stage 0 (high Aß and low tau), stage 1 (low Aß and low tau), stage 2 (low Aß and high tau), and suspected non-AD pathology (SNAP) (high Aß and high tau). The data presented herein were collected between August 1995 and August 2014. MAIN OUTCOMES AND MEASURES: An a priori cognitive composite score based on the following 4 tests previously shown to predict progression from normal cognition to symptom onset of mild cognitive impairment or dementia: Paired Associates immediate recall, Logical Memory delayed recall, Boston Naming, and Digit-Symbol Substitution. Linear mixed-effects models were used to compare the cognitive composite scores across the 4 groups over time, adjusting for baseline age, sex, education, and their interactions with time. RESULTS: Two hundred twenty-two cognitively normal participants were included in the analyses (mean follow-up, 11.0 years [range, 0-18.3 years] and mean baseline age, 56.9 years [range, 22.1-85.8 years]). Of these, 102 were stage 0, 46 were stage 1, 28 were stage 2, and 46 were SNAP. Individuals in stage 2 (low Aß and high tau [or p-tau]) had lower baseline cognitive scores and a greater decline in the cognitive composite score relative to the other 3 groups (ß ≤ -0.06 for all and P ≤ .001 for the rate of decline for all). Individuals in stage 0, stage 1, and SNAP did not differ from one another in cognitive performance at baseline or over time (11.0 years) and showed practice-related improvement in performance. The APOE ε4 genotype was not associated with baseline cognitive composite score or the rate of change in the cognitive composite score. CONCLUSIONS AND RELEVANCE: These results suggest that, to optimize observing a treatment effect, clinical trials enrolling cognitively normal individuals should selectively recruit participants with abnormal levels of both amyloid and tau (ie, stage 2) because this group would be expected to show the greatest cognitive decline over time if untreated.

Proteomics in India: A Report on a Brainstorming Meeting at Hyderabad, India.

The Centre for Cellular and Molecular Biology, Hyderabad, India, was host for an international forum, or "brainstorming meeting," on proteomics held in November 2014, which provided the opportunity to showcase proteomic science in India and to allow discussions between Indian scientists and students and several international visitors. This provided an amalgamation of speakers and participants whose interests lay mainly in developing and using mass-spectrometry-based proteomics to advance their research work. A week-long workshop with hands-on training in proteomic methodology followed the meeting.

Klotho in the cerebrospinal fluid of adults with and without Alzheimer's disease.

The aging-suppressor gene klotho encodes a single-pass transmembrane protein that is predominantly secreted by the choroid plexus of the brain and in the kidney. Klotho-deficient mice develop multiple aging phenotypes, including impaired cognition. Klotho concentrations have not been described in the CSF of humans. We measured klotho in the CSF of 20 older adults with Alzheimer's disease and in 20 older and 20 younger adults with normal cognition. In 10 adults, aged 38-87 years, CSF klotho measurements were made at baseline and every 6h up to 18-30 h later. Mean (95% confidence interval [C.I.]) CSF klotho in men versus women were 899 (814, 983) and 716 (632, 801) pg/mL, respectively (P=0.002). Mean (95% C.I.) CSF klotho in older adults with and without Alzheimer's disease were 664 (603, 725) and 776 (705, 828) pg/mL, respectively (P=0.02), adjusting for sex. Mean (95% C.I.) klotho in older versus younger adults were 766 (658, 874) and 992 (884, 1100) pg/mL, respectively (P=0.005), adjusting for sex. In the longitudinal study of CSF klotho, no significant circadian fluctuations were found in CSF klotho levels. This study suggests that CSF klotho concentrations are lower in females compared with males, in Alzheimer's disease, and in older versus younger adults.