Distinct cerebrospinal fluid amyloid β peptide signatures in sporadic and PSEN1 A431E-associated familial Alzheimer's disease

<p>Abstract</p> <p>Background</p> <p>Alzheimer's disease (AD) is associated with deposition of amyloid β (Aβ) in the brain, which is reflected by low concentration of the Aβ1-42 peptide in the cerebrospinal fluid (CSF). There are at least 15 additional Aβ peptides in human CSF and their relative abundance pattern is thought to reflect the production and degradation of Aβ. Here, we test the hypothesis that AD is characterized by a specific CSF Aβ isoform pattern that is distinct when comparing sporadic AD (SAD) and familial AD (FAD) due to different mechanisms underlying brain amyloid pathology in the two disease groups.</p> <p>Results</p> <p>We measured Aβ isoform concentrations in CSF from 18 patients with SAD, 7 carriers of the FAD-associated presenilin 1 (<it>PSEN1</it>) A431E mutation, 17 healthy controls and 6 patients with depression using immunoprecipitation-mass spectrometry. Low CSF levels of Aβ1-42 and high levels of Aβ1-16 distinguished SAD patients and FAD mutation carriers from healthy controls and depressed patients. SAD and FAD were characterized by similar changes in Aβ1-42 and Aβ1-16, but FAD mutation carriers exhibited very low levels of Aβ1-37, Aβ1-38 and Aβ1-39.</p> <p>Conclusion</p> <p>SAD patients and <it>PSEN1 </it>A431E mutation carriers are characterized by aberrant CSF Aβ isoform patterns that hold clinically relevant diagnostic information. <it>PSEN1 </it>A431E mutation carriers exhibit low levels of Aβ1-37, Aβ1-38 and Aβ1-39; fragments that are normally produced by γ-secretase, suggesting that the <it>PSEN1 </it>A431E mutation modulates γ-secretase cleavage site preference in a disease-promoting manner.</p

CCL2 Is Associated with a Faster Rate of Cognitive Decline during Early Stages of Alzheimer's Disease

Chemokine (C-C motif) receptor 2 (CCR2)-signaling can mediate accumulation of microglia at sites affected by neuroinflammation. CCR2 and its main ligand CCL2 (MCP-1) might also be involved in the altered metabolism of beta-amyloid (Aβ) underlying Alzheimer's disease (AD). We therefore measured the levels of CCL2 and three other CCR2 ligands, i.e. CCL11 (eotaxin), CCL13 (MCP-4) and CCL26 (eotaxin-3), in the cerebrospinal fluid (CSF) and plasma of 30 controls and 119 patients with mild cognitive impairment (MCI) at baseline. During clinical follow-up 52 MCI patients were clinically stable for five years, 47 developed AD (i.e. cases with prodromal AD at baseline) and 20 developed other dementias. Only CSF CCL26 was statistically significantly elevated in patients with prodromal AD when compared to controls (p = 0.002). However, in patients with prodromal AD, the CCL2 levels in CSF at baseline correlated with a faster cognitive decline during follow-up (rs = 0.42, p = 0.004). Furthermore, prodromal AD patients in the highest tertile of CSF CCL2 exhibited a significantly faster cognitive decline (p<0.001) and developed AD dementia within a shorter time period (p<0.003) compared to those in the lowest tertile. Finally, in the entire MCI cohort, CSF CCL2 could be combined with CSF Tau, P-tau and Aβ42 to predict both future conversion to AD and the rate of cognitive decline. If these results are corroborated in future studies, CCL2 in CSF could be a candidate biomarker for prediction of future disease progression rate in prodromal AD. Moreover, CCR2-related signaling pathways might be new therapeutic targets for therapies aiming at slowing down the disease progression rate of AD

Prediction of Alzheimer’s disease in subjects with Mild Cognitive Impairment using biomarkers

Background: Alzheimer’s disease (AD) is the most common cause of dementia. In order to have effect of future disease-modifying therapies for AD, the disease must be identified early, before the patients have developed dementia. Many patients with Mild Cognitive Impairment (MCI) have prodromal AD, but other causes for the syndrome are common. No diagnostic method can identify AD in patients with MCI with sufficient accuracy. Aim: Evaluation of biomarkers in cerebrospinal fluid (CSF) and plasma for identifying prodromal AD in patients with MCI. Settings: At baseline 137 subjects with MCI and successful lumbar puncture were included. CSF from baseline was analyzed for phosphorylated tau (P-tau), total tau (T- tau) and amyloidβ1-42 (Aβ42). Furthermore, the levels of soluble receptors for Tumor Necrosis Factor-α (sTNFR) 1 and 2, as well as soluble CD40 (sCD40) and the CD40 ligand were analyzed. The latter biomarkers reflect inflammation. Results: After the first follow-up of around 5 years, 57 patients had developed AD dementia. The levels of T-tau, P-tau and Aβ42 could with high accuracy identify patients with prodromal AD. After the second follow-up was finished, approximately 9 years from baseline, 72 patients had developed AD dementia. The positive and negative predictive values of the Aβ42/ P-tau ratio after this follow-up were around 90%. The Aβ42 levels were pathological already 10 years before progression to dementia. Moreover, Tau and Aβ42 were quite stable over time in patients with AD dementia. The levels of TNFR 1 and 2 both in CSF and plasma and sCD40 in plasma were elevated in the MCI patients with AD 5 years before progression to dementia. Conclusion: CSF biomarkers can identify subjects with prodromal AD. Inflammation is an early feature of AD. These results have an impact on the diagnostic work-up of patients with MCI, as well as the development of AD therapies

Cube Copying Test in Combination with rCBF or CSF Abeta(42)Predicts Development of Alzheimer's Disease.

Background/Aim: The aim was to identify subjects with incipient Alzheimer's disease (AD) among patients with mild cognitive impairment (MCI) using brief cognitive tests. Methods: A total of 147 MCI patients were followed for 4-6 years and the incidence of AD was 11.6%/year. At baseline, the cube copying test, clock drawing test, MMSE and measurements of regional cerebral blood flow (rCBF) and cerebrospinal fluid (CSF) beta-amyloid(1-42) (Abeta(42)) were performed. Results: The cube copying test, but not the clock drawing test, could predict AD among MCI patients with an area under the receiver operating characteristic curve of 0.64 (p < 0.01). The relative risk for future AD was increased in MCI subjects with impaired cube copying test (sex- and age-adjusted hazard ratio = 1.8, p < 0.05) and the incidence of AD was 18.2% in this subgroup. Combining the cube copying test with either rCBF or CSF Abeta(42) had additive effects on the risk assessment for future development of AD. MCI patients achieving high scores on both MMSE and cube copying test had a very low risk of developing AD (incidence of AD = 1.6%). Conclusion: In conclusion, combinations of the cube copying test with MMSE, rCBF and CSF Abeta(42) measurements can identify subgroups of MCI subjects with either substantially reduced or increased risk for future development of AD

Soluble TNF receptors are associated with Abeta metabolism and conversion to dementia in subjects with mild cognitive impairment.

OBJECTIVE: There is evidence supporting that tumor necrosis factor receptor (TNFR)-signaling can induce production of beta-amyloid (Abeta) in the brain. Moreover, amyloid-induced toxicity has been shown to be dependent on TNFR-signaling. However, it is still unclear whether TNFRs are involved in the early stages of dementia. METHODS: We analyzed soluble TNFR1 and TNFR2 levels in plasma and cerebrospinal fluid (CSF) at baseline in 137 patients with mild cognitive impairment (MCI) and 30 age-matched controls. The MCI patients were followed for 4-6 years with an incidence of Alzheimer's disease (AD) or vascular dementia (VaD) of 15% per year. RESULTS: The patients with MCI who subsequently developed these forms of dementias had higher levels of sTNFR1 and sTNFR2 in both CSF and plasma already at baseline when compared to age-matched controls (p<0.05). In the CSF of MCI subjects and controls the levels of both sTNFR1 and sTNFR2 correlated strongly with beta-site APP-cleaving enzyme 1 (BACE1) activity (r(s)=0.53-0.68, p<0.01) and Abeta 40 levels (r(s)=0.59-0.71, p<0.001). Similarly, both sTNFRs were associated with Abeta 40 (r(s)=0.39-0.46, p<0.05) in plasma. Finally, the levels of both sTNFRs correlated with the axonal damage marker tau in the CSF of MCI subjects and controls (r(s)=0.57-0.83, p<0.001). CONCLUSION: TNFR-signaling might be involved in the early pathogenesis of AD and VaD, and could be associated with beta-amyloid metabolism

Cerebrospinal Fluid Levels of β-Amyloid 1-42, but Not of Tau, Are Fully Changed Already 5 to 10 Years Before the Onset of Alzheimer Dementia.

CONTEXT: Early detection of prodromal Alzheimer disease (AD) is important because new disease-modifying therapies are most likely to be effective when initiated during the early stages of disease. OBJECTIVES: To assess the ability of the cerebrospinal fluid (CSF) biomarkers total tau (T-tau), phosphorylated tau (P-tau), and β-amyloid 1-42 (Aβ42) to predict future development of AD dementia within 9.2 years in patients with mild cognitive impairment (MCI) and to compare CSF biomarkers between early and late converters to AD. DESIGN: A clinical study with a median follow-up of 9.2 years (range, 4.1-11.8 years). SETTING: Memory disorder clinic. Patients A total of 137 patients with MCI who underwent lumbar puncture at baseline. Main Outcome Measure Conversion to AD dementia. RESULTS: During follow-up, 72 patients (53.7%) developed AD and 21 (15.7%) progressed to other forms of dementia. At baseline, CSF Aβ42 levels were reduced and T-tau and P-tau levels were elevated in patients who converted to AD during follow-up compared with nonconverters (P < .001). Baseline CSF Aβ42 levels were equally reduced in patients with MCI who converted to AD within 0 to 5 years (early converters) compared with those who converted between 5 and 10 years (late converters). However, CSF T-tau and P-tau levels were significantly higher in early converters vs late converters. A baseline Aβ42:P-tau ratio predicted the development of AD within 9.2 years with a sensitivity of 88%, specificity of 90%, positive predictive value of 91%, and negative predictive value of 86%. CONCLUSIONS: Approximately 90% of patients with MCI and pathologic CSF biomarker levels at baseline develop AD within 9 to 10 years. Levels of Aβ42 are already fully decreased at least 5 to 10 years before conversion to AD dementia, whereas T-tau and P-tau seem to be later markers. These results provide direct support in humans for the hypothesis that altered Aβ metabolism precedes tau-related pathology and neuronal degeneration

Elevated plasma levels of soluble CD40 in incipient Alzheimer's disease.

CD40 is a member of the tumor necrosis factor receptor super-family and has been suggested to play a role in the metabolism of beta-amyloid (Abeta) in Alzheimer's disease (AD). However, the role of CD40-signalling in incipient AD has not yet been studied. We investigated the plasma levels of soluble CD40 (sCD40) and the soluble CD40 ligand (sCD40L) at baseline in 136 subjects with mild cognitive impairment (MCI) and 30 age-matched controls. Sixty of the 136 MCI cases converted to AD (MCI-AD) during a clinical follow-up period of 4-7 years. The baseline levels of sCD40, but not sCD40L, were elevated in MCI-AD cases when compared to age-matched controls (Mann-Whitney U-test, p=0.02). However, MCI patients who were cognitively stable or developed vascular dementia during follow-up did not have significantly increased levels of sCD40 or sCD40L when compared to controls. The levels of sCD40 correlated to decreased baseline performance on mini-mental state examination (MMSE) in both controls (r(s)=-0.37, p<0.05) and MCI-AD cases (r(s)=-0.29, p<0.05). Finally, the plasma levels of sCD40 correlated with the levels of soluble amyloid precursor protein-alpha (sAPP-alpha) (r(s)=0.28, p<0.01) and sAPP-beta (r(s)=0.23, p<0.05) in cerebrospinal fluid. In conclusion, CD40-signalling might play a role in the pathogenesis of early AD

Combined rCBF and CSF biomarkers predict progression from mild cognitive impairment to Alzheimer's disease.

This study aimed to identify preclinical Alzheimer's disease (AD) in patients with mild cognitive impairment (MCI) using measurements of both regional cerebral blood flow (rCBF) and cerebrospinal fluid (CSF) biomarkers. Baseline rCBF assessments (133Xe method) were performed in 70 patients with MCI who were cognitively stable for 4–6 years, 69 patients with MCI who subsequently developed AD, and 33 healthy individuals. CSF was collected at baseline and analyzed for β-amyloid1–42, total tau and phophorylated tau. In contrast to patients with stable MCI, those who subsequently developed AD had decreased rCBF in the temporo-parietal cortex already at baseline. The relative risk of future progression to AD was particularly increased in MCI patients with decreased rCBF in parietal cortex (hazard ratio 3.1, P < 0.0001). Subjects with pathological levels of both CSF tau and β-amyloid1–42 were also at high risk of developing AD (hazard ratio 13.4, P < 0.0001). The MCI patients with a combination of decreased parietal rCBF and pathological CSF biomarkers at baseline had a substantially increased risk of future development of AD, with a hazard ratio of 24.3 (P < 0.0001), when compared to those with normal CSF biomarkers. Moreover, decreased parietal rCBF (but not CSF biomarkers) was associated with a more rapid progression to AD. In conclusion, the combination of rCBF and CSF biomarkers improves the risk assessment of progression to AD in patients with MCI

Prediction of Alzheimer's Disease Using the CSF Abeta42/Abeta40 Ratio in Patients with Mild Cognitive Impairment.

Evidence supports an important role for beta-amyloid (A beta) in the pathogenesis of Alzheimer's disease ( AD). Here, we investigate baseline levels of the 40- and 42-amino-acid-long A beta peptides (A beta 40 and A beta 42) in cerebrospinal fluid (CSF) from a cohort of patients with mild cognitive impairment (MCI, n = 137) in relation to the final diagnosis after 4 - 6 years of follow-up time. CSF A beta 42 concentration at baseline and the A beta 42/A beta 40 ratio were significantly decreased in the MCI patients who developed AD as compared to cognitively stable MCI patients and MCI patients who developed other forms of dementia ( p < 0.001). The baseline levels of A beta 40 were similar in all MCI groups but correlated with change in Mini Mental State Examination scores in converters to AD. The A beta 42/A beta 40 ratio was superior to A beta 42 concentration with regard to identifying incipient AD in MCI ( p < 0.05). In conclusion, the data provide further support for the view that amyloid precursor protein metabolism is disturbed in early sporadic AD and points to the usefulness of the A beta 42/ A beta 40 ratio as a predictive biomarker for AD