Cerebrospinal fluid markers for synaptic function and Alzheimer type changes in late life depression

To explore markers for synaptic function and Alzheimer disease (AD) pathology in late life depression (LLD), predementia AD and normal controls (NC). A cross-sectional study to compare cerebrospinal fluid (CSF) levels of neurogranin (Ng), Beta-site amyloid-precursor-protein cleaving enzyme1 (BACE1), Ng/BACE1 ratio and Amyloid-β 42/40 ratio, phosphorylated-tau and total-tau in LLD with (LLD AD) or without (LLD NoAD) AD pathology, predementia AD and normal controls (NC). We included 145 participants (NC = 41; predementia AD = 66 and LLD = 38). LLD comprised LLD AD (n = 16), LLD NoAD (n = 19), LLD with non-AD typical changes (n = 3, excluded). LLD AD (pADJ < 0.05) and predementia AD (pADJ < 0.0001) showed significantly higher Ng than NC. BACE1 and Ng/BACE1 ratio were altered similarly. Compared to LLD NoAD, LLD AD showed significantly higher Ng (pADJ < 0.001), BACE1 (pADJ < 0.05) and Ng/BACE1 ratio (pADJ < 0.01). All groups had significantly lower Aβ 42/40 ratio than NC (predementia AD and LLD AD, p < 0.0001; LLD NoAD, p < 0.05). Both LLD groups performed similarly on tests of memory and executive function, but significantly poorer than NC. Synaptic function in LLD depended on AD pathology. LLD showed an association to Amyloid dysmetabolism. The LLD groups performed poorer cognitively than NC. LLD AD may be conceptualized as "predementia AD with depression".

Pathophysiological subtypes of Alzheimer's disease based on cerebrospinal fluid proteomics

Alzheimer's disease is biologically heterogeneous, and detailed understanding of the processes involved in patients is critical for development of treatments. CSF contains hundreds of proteins, with concentrations reflecting ongoing (patho)physiological processes. This provides the opportunity to study many biological processes at the same time in patients. We studied whether Alzheimer's disease biological subtypes can be detected in CSF proteomics using the dual clustering technique non-negative matrix factorization. In two independent cohorts (EMIF-AD MBD and ADNI) we found that 705 (77% of 911 tested) proteins differed between Alzheimer's disease (defined as having abnormal amyloid, n = 425) and controls (defined as having normal CSF amyloid and tau and normal cognition, n = 127). Using these proteins for data-driven clustering, we identified three robust pathophysiological Alzheimer's disease subtypes within each cohort showing (i) hyperplasticity and increased BACE1 levels; (ii) innate immune activation; and (iii) blood-brain barrier dysfunction with low BACE1 levels. In both cohorts, the majority of individuals were labelled as having subtype 1 (80, 36% in EMIF-AD MBD; 117, 59% in ADNI), 71 (32%) in EMIF-AD MBD and 41 (21%) in ADNI were labelled as subtype 2, and 72 (32%) in EMIF-AD MBD and 39 (20%) individuals in ADNI were labelled as subtype 3. Genetic analyses showed that all subtypes had an excess of genetic risk for Alzheimer's disease (all P > 0.01). Additional pathological comparisons that were available for a subset in ADNI suggested that subtypes showed similar severity of Alzheimer's disease pathology, and did not differ in the frequencies of co-pathologies, providing further support that found subtypes truly reflect Alzheimer's disease heterogeneity. Compared to controls, all non-demented Alzheimer's disease individuals had increased risk of showing clinical progression (all P < 0.01). Compared to subtype 1, subtype 2 showed faster clinical progression after correcting for age, sex, level of education and tau levels (hazard ratio = 2.5; 95% confidence interval = 1.2, 5.1; P = 0.01), and subtype 3 at trend level (hazard ratio = 2.1; 95% confidence interval = 1.0, 4.4; P = 0.06). Together, these results demonstrate the value of CSF proteomics in studying the biological heterogeneity in Alzheimer's disease patients, and suggest that subtypes may require tailored therapy.

[Molecular markers of Alzheimer disease early diagnostic: investigation perspectives of peripheral tissues.]

Alzheimer's disease (AD) is a progressive neurodegenerative disorder of elderly and old age people. For intravital diagnosis of the expression of signaling molecules - AD markers, cerebrospinal fluid (CSF) and peripheral tissues are used: lymphocytes and blood platelets, buccal and olfactory epithelium, skin fibroblasts. There are several changes in the production of hyper phosphorylated form of τ-protein, BACE1 and peptide Аβ42 in CSF in case of AD, but CSF taking may have a number of side effects. Less traumatic taking of sampling tissues for the diagnosis of AD is in use of epithelium biopsy and blood portion. An increase in the expression of the hyper phosphorylated form of τ-protein is shown in blood lymphocytes of AD patients. An increase in the content of high molecular weight forms of phosphorylated t-protein and amyloid precursor protein-APP was also revealed in blood platelets of AD patients. Changes in the amount of 2 miRNA families - miR-132 family and miR-134 family were revealed in blood cells 1-5 years before the manifestation of clinical signs of AD. An increase in the concentration of bound calcium, synthesis of peptides Aβ40 and Aβ42, τ protein was observed in AD skin fibroblasts. In the olfactory and buccal epithelium an increase in the expression of hyper phosphorylated form of τ-protein and Aβ peptide was detected in patients with AD. Verification of AD markers in peripheral tissues for biopsy have the important significant for life diagnostics, prevention and and target AD treatment.

Cerebrospinal fluid BACE1 activity and markers of amyloid precursor protein metabolism and axonal degeneration in Alzheimer's disease

OBJECTIVE

The objective of this study was to assess cerebrospinal fluid (CSF) β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) activity in relation to Alzheimer's disease (AD) and to correlate the enzyme activity with protein markers of APP metabolism and axonal degeneration.

METHODS

BACE1 activity and protein concentrations were measured and analyzed in 342 participants of the Alzheimer's Disease Neuroimaging Initiative, including 99 normal control, 75 stable mild cognitive impairment (MCI), 87 progressive MCI, and 79 AD dementia cases. All statistical analyses were Bonferroni corrected for multiple comparisons.

RESULTS

No significant differences between controls and any of the three patient groups were detected for BACE1 activity and soluble APPβ (sAPPβ) concentrations in CSF. Significant correlations with BACE1 activity were found for CSF APPβ and total tau in all four groups and for CSF phosphorylated tau181 in all groups but the progressive MCI group. There were no correlations for CSF amyloid β (Aβ)1-42 or for plasma Aβ1-42 and Aβ1-40.

CONCLUSIONS

The consistent correlation between BACE1 activity and sAPPβ supports their role as biomarkers of target engagement in clinical trials on BACE1 inhibition.

Distinct patterns of APP processing in the CNS in autosomal-dominant and sporadic Alzheimer disease

Autosomal-dominant Alzheimer disease (ADAD) is a genetic disorder caused by mutations in Amyloid Precursor Protein (APP) or Presenilin (PSEN) genes. Studies from families with ADAD have been critical to support the amyloid cascade hypothesis of Alzheimer disease (AD), the basis for the current development of amyloid-based disease-modifying therapies in sporadic AD (SAD). However, whether the pathological changes in APP processing in the CNS in ADAD are similar to those observed in SAD remains unclear. In this study, we measured β-site APP-cleaving enzyme (BACE) protein levels and activity, APP and APP C-terminal fragments in brain samples from subjects with ADAD carrying APP or PSEN1 mutations (n = 18), patients with SAD (n = 27) and age-matched controls (n = 22). We also measured sAPPβ and BACE protein levels, as well as BACE activity, in CSF from individuals carrying PSEN1 mutations (10 mutation carriers and 7 non-carrier controls), patients with SAD (n = 32) and age-matched controls (n = 11). We found that in the brain, the pattern in ADAD was characterized by an increase in APP β-C-terminal fragment (β-CTF) levels despite no changes in BACE protein levels or activity. In contrast, the pattern in SAD in the brain was mainly characterized by an increase in BACE levels and activity, with less APP β-CTF accumulation than ADAD. In the CSF, no differences were found between groups in BACE activity or expression or sAPPβ levels. Taken together, these data suggest that the physiopathological events underlying the chronic Aβ production/clearance imbalance in SAD and ADAD are different. These differences should be considered in the design of intervention trials in AD.

Levels of beta-secretase (BACE1) in cerebrospinal fluid as a predictor of risk in mild cognitive impairment

CONTEXT

Elevated beta-secretase (beta-site amyloid precursor protein-cleaving enzyme 1 [BACE1]) activity has been found in the brains of patients with sporadic Alzheimer disease (AD) compared with controls. Now we are particularly interested in whether BACE1 can be identified in the cerebrospinal fluid (CSF) of patients with mild cognitive impairment (MCI), a population at high risk for AD. The possible presence of BACE1 in the CSF of patients with AD and MCI has so far gone unreported.

OBJECTIVE

To examine whether BACE1 can be identified in the CSF of patients with MCI.

DESIGN

We evaluated CSF BACE1 levels using 2 sandwich enzyme-linked immunosorbent assays, BACE1 enzymatic activities by means of synthetic fluorescence substrate, and total amyloid-beta peptide levels using a sandwich enzyme-linked immunosorbent assay.

SETTING

Two independent research centers.

PARTICIPANTS

Eighty patients with sporadic AD, 59 patients with MCI, and 69 controls.

MAIN OUTCOME MEASURES

BACE1 levels and enzymatic activities and amyloid-beta peptide levels.

RESULTS

Increased CSF levels of BACE1 protein were associated with increased risk ratios (RRs) for patients with MCI compared with controls (RR, 2.08; 95% confidence interval [CI], 1.58-2.58) and patients with AD (RR, 1.65; 95% CI, 1.19-2.03). Similarly, patients with MCI showed increased levels of BACE1 activity compared with controls (RR, 2.17; 95% CI, 1.66-2.71) and patients with AD (RR, 3.71; 95% CI, 2.74-4.36). For total amyloid-beta peptide and tau, increased CSF levels were associated with a higher risk of MCI compared with controls. The BACE1 activity was significantly correlated with BACE1 protein level (rho = 0.23; P<.001) and amyloid-beta peptide level (rho = 0.39; P<.001), with amyloid-beta peptide correlated with BACE1 protein level (rho = 0.30; P<.001).

CONCLUSION

Significant elevation of BACE1 levels and activity in CSF is an indicator of MCI, which could be an early stage of AD.