Lennart Minthon

Elevated cerebrospinal fluid BACE1 activity in incipient Alzheimer disease.

BACKGROUND We used a sensitive and specific beta-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) assay to determine the relationship between BACE1 activity in cerebrospinal fluid (CSF) and markers of APP metabolism and axonal degeneration in early and late stages of Alzheimer disease (AD). OBJECTIVE To assess CSF BACE1 activity in AD. DESIGN Case-control and longitudinal follow-up study. SETTING Specialized memory clinic. Patients Eighty-seven subjects with AD, 33 cognitively normal control subjects, and 113 subjects with mild cognitive impairment (MCI), who were followed up for 3 to 6 years. MAIN OUTCOME MEASURES Cerebrospinal fluid BACE1 activity in relation to diagnosis and CSF levels of secreted APP and amyloid beta protein (Abeta) isoforms and the axonal degeneration marker total tau. RESULTS Subjects with AD had higher CSF BACE1 activity (median, 30 pM [range, 11-96 pM]) than controls (median, 23 pM [range, 8-43 pM]) (P =.02). Subjects with MCI who progressed to AD during the follow-up period had higher baseline BACE1 activity (median, 35 pM [range, 18-71 pM]) than subjects with MCI who remained stable (median, 29 pM [range, 14-83 pM]) (P < .001) and subjects with MCI who developed other forms of dementia (median, 20 pM [range, 10-56 pM]) (P <.001). BACE1 activity correlated positively with CSF levels of secreted APP isoforms and Abeta(40) in the AD and control groups and in all MCI subgroups (P < .05) except the MCI subgroup that developed AD. Strong positive correlations were found between CSF BACE1 activity and total tau levels in all MCI subgroups (r >or= 0.57, P <or= .009). CONCLUSION Elevated BACE1 activity may contribute to the amyloidogenic process in sporadic AD and is associated with the intensity of axonal degeneration.

Measurement of alpha- and beta-secretase cleaved amyloid precursor protein in cerebrospinal fluid from Alzheimer patients

One of the major histopathological hallmarks of Alzheimers disease (AD) is redundant senile plaques mainly composed of beta-amyloid (Abeta) aggregates. Alternative cleavage of the amyloid precursor protein (APP), occurring in both normal and AD subjects, results in the generation and secretion of soluble APP (sAPP) and Abeta. We examined the cerebrospinal fluid (CSF) for alpha- and beta-secretase cleaved sAPP (alpha-sAPP and beta-sAPP) in 81 sporadic AD patients, 19 patients with mild cognitive impairment, and 42 healthy controls by using newly developed sandwich enzyme-linked immunosorbent assay methods. We found that neither the level of CSF-alpha-sAPP nor CSF-beta-sAPP differed between sporadic AD patients and healthy controls. These findings further support the conclusion that there is no change in APP expression in sporadic AD. However, the level of CSF-beta-sAPP was significantly increased in patients with mild cognitive impairment compared to controls. We also investigated the relationship between the CSF level of alpha/beta-sAPP and Abeta(42) and the apoE epsilon 4 (apoE4) allele. Significantly lower levels of CSF-alpha-sAPP were found in AD patients possessing one or two apoE4 alleles than in those not possessing the apoE4 allele. Neither the levels of CSF-beta-sAPP nor CSF-Abeta(42) differed when comparing ApoE4 allele-positive with allele-negative individuals.

No association between the alpha2-macroglobulin (A2M) deletion and Alzheimer's disease, and no change in A2M mRNA, protein, or protein expression

Summary. A polymorphism consisting of a deletion near the 5′ splice site of exon 18 on the α2-macroglobulin (A2M) gene (A2M-2) has been suggested to be associated with Alzheimers disease (AD) in family-based studies. We studied the A2M-2 allele together with the ApoE alleles in a large series on patients with AD (n = 449) and age-matched controls (n = 349). Neuropathologically confirmed diagnoses were available in 199 cases (94 AD and 107 control cases). We found no increase in A2M-2 genotype or allele frequencies in AD (27.5% and 14.6%) versus controls (26.4% and 14.9%). In contrast, a marked increase (p < 0.0001) in ApoE ε4 genotype or allele frequencies was found in AD (66.6% and 41.2%) as compared with controls (29.8% and 16.5%), suggesting sufficient statistical power in our sample. No relation was found between the A2M-2 and the ApoE ε4 allele. No change in A2M exon 17–18 mRNA size or sequence or A2M protein size was found in cases carrying the A2M-2 deletion, suggesting that there is no biological consequences of the A2M intronic deletion. No change in A2M protein level in cerebrospinal fluid was found in AD, suggesting that the A2M-2 allele does not effect the A2M protein expression in the brain. The lack of an association between the A2M-2 allele and AD in the present study, and the lack of abnormalities in the A2M mRNA or protein suggest that the A2M-2 allele is not associated with AD.

Correlation of longitudinal cerebrospinal fluid biomarkers with cognitive decline in healthy older adults.

BACKGROUND Abnormal cerebrospinal fluid (CSF) biomarker levels predict development of Alzheimer disease with good accuracy and are thought to precede cognitive deterioration. OBJECTIVE To investigate whether changes in CSF biomarker levels over time in healthy older adults are associated with a concurrent decline in cognitive performance. DESIGN Retrospective analysis of longitudinal CSF biomarker levels and clinical data. SETTING A combined academic dementia disorder research center and dementia clinic. PARTICIPANTS Thirty-seven cognitively healthy older volunteers (mean age, 73 years). MAIN OUTCOME MEASURES Longitudinal CSF total tau protein, hyperphosphorylated tau protein 181, and beta-amyloid(1-42) protein levels and cognitive assessments at baseline and at follow-up 4 years later. RESULTS Low levels of CSF beta-amyloid(1-42) protein at follow-up were associated with decreased delayed word recall score on the Alzheimer Disease Assessment Scale-cognitive subscale (r(s) = -0.437, P < .01) and with slower results on A Quick Test of Cognitive Speed (r(s) = -0.540, P < .001). Individuals with a decrease during the 4-year study of 15% or more in CSF beta-amyloid(1-42) protein level performed worse on the Alzheimer Disease Assessment Scale-cognitive subscale delayed word recall (z = -2.18, P < .05) and A Quick Test of Cognitive Speed (z = -2.35, P < .05) at follow-up. An increase over time of 20% or more in CSF hyperphosphorylated tau protein 181 level correlated with slower results on A Quick Test of Cognitive Speed at follow-up (z = -2.13, P < .05). Furthermore, the presence of the APOE-epsilon4 (OMIM 107741) allele was associated with a greater longitudinal decrease in CSF beta-amyloid(1-42) protein level (chi(2) = 10.47, P < .05) and with a higher CSF total tau protein level at follow-up (chi(2) = 8.83, P < .05). No correlation existed between baseline CSF biomarker levels and baseline or follow-up cognitive scores. CONCLUSIONS In this group of healthy older adults, changes in CSF biomarker levels previously associated with Alzheimer disease correlated with a decline in cognitive functions. Changes in CSF biomarker levels may identify early neurodegenerative processes of Alzheimer disease.

Differential increase in cerebrospinal fluid-acetylcholinesterase after treatment with acetylcholinesterase inhibitors in patients with Alzheimer's disease

The clinical significance and the effects of pharmacological treatment of patients with Alzheimers disease (AD) were evaluated by measurement of acetylcholinesterase (AChE) in the cerebrospinal fluid (CSF). CSF-AChE of AD patients was lower, not significantly, compared with controls. However, CSF-AChE was significantly increased after treatment of AD patients with AChE inhibitors (donepezil and galantamine). The increase was higher in patients treated with donezepil than in those treated with galantamine, which might be related to different mechanisms for the substances. The increase was also dose-dependent, and was especially marked in patients showing a clinical response. These data suggest that CSF biomarkers are capable not only of identifying a biochemical effect of drugs, but also of differentiating between different compounds in a dose-dependent manner.

Cerebrospinal fluid levels of biomarkers and activity of acetylcholinesterase (AChE) and butyrylcholinesterase in AD patients before and after treatment with different AChE inhibitors.

Abstract. In order to evaluate the biochemical effects of long-term treatment with inhibitors of acetylcholinesterase (AChE) in patients with Alzheimers disease (AD), we measured the activities of AChE and butyrylcholinesterase (BuChe) and the concentrations of β-amyloid (1–42), τ and phosphorylated τ proteins in the cerebrospinal fluid (CSF). A total of 91 patients suffering from probable AD of mild to moderate degree were treated for 6 months with donepezil (n=59), galantamine (n=15), rivastigmine (n=10), or placebo (n=7). AChE activity in CSF was significantly increased after treatment with donepezil and galantamine; the opposite was observed in the rivastigmine-treated group. Untreated patients did not show any AChE activity variation. BuChE did not show any change in any of the groups studied. Mean values of β-amyloid(1–42), total τ and phosphorylated τ also did not vary significantly. We conclude that AChE inhibitors induce different effects on CSF AChE activity, while other CSF biomarkers are not significantly affected by treatment.

Processing of neuropeptide Y, galanin, and somatostatin in the cerebrospinal fluid of patients with Alzheimer's disease and frontotemporal dementia

Alzheimers disease (AD) and frontotemporal dementia (FTD) are two prevalent neurodegenerative disorders for which the causes are unknown, except in rare familial cases. Several changes in neuropeptide levels as measured by radioimmunoassay (RIA) have been observed in these illnesses. Somatostatin (SOM) levels in cerebrospinal fluid (CSF) are consistently decreased in AD and FTD. Neuropeptide Y (NPY) levels are decreased in AD, but normal in FTD. Galanin (GAL) levels increase with the duration of illness in AD patients. The majority of studies of neuropeptides in CSF have not been verified by HPLC. The observed decrease in a neuropeptide level as measured by RIA may therefore reflect an altered synthesis or extracellular processing, resulting in neuropeptide fragments that may or may not be detected by RIA. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-MS) has been shown to be a powerful technique in the analysis of biological materials without any pre-treatment, by detecting peptides and proteins at a specific mass-to-charge (m/z) ratio. We studied the processing of the neuropeptides NPY, NPY, SOM and GAL in the cerebrospinal fluid of patients with AD (n = 3), FTD (n = 3) and controls (n = 2) using MALDI-MS. We found that considerable inter-individual variability exists in the rate of neuropeptide metabolism in CSF, as well as the number of peptide fragments formed. Certain patients showed differences in the processing of specific neuropeptides, relative to other patients and controls. This analysis of the metabolic processing of neuropeptides in CSF yielded a large amount of data for each individual studied. Further studies are required to determine the changes in neuropeptide processing that can be associated with AD and FTD. With further investigations using MALDI-MS analysis, it may be possible to identify a neuropeptide fragment or processing enzyme that can be correlated to these disease states.

Cerebrospinal fluid tau and beta-amyloid(1-42) in dementia disorders

The reliability of cerebrospinal fluid (CSF)-tau and CSF-beta-amyloid assays for diagnosis of Alzheimers disease and other dementing disorders such as frontotemporal dementia (FTD), dementia with Lewy bodies (DLB) and Creutzfeldt-Jakob disease (CJD) is reviewed. CSF assessment of the two proteins is useful in early diagnosis of AD and to differentiate it from FTD and DLB. Extremely high CSF-tau levels can discriminate CJD from AD.

Five-year outcome of cholinergic treatment of Alzheimer's disease: early response predicts prolonged time until nursing home placement, but does not alter life expectancy.

Fifty consecutive outpatients with Alzheimer’s disease (AD) received treatment with the cholinesterase inhibitor tacrine in an open longitudinal study. Assessments using Mini-Mental State Examination, Alzheimer’s Disease Assessment Scale – cognitive subscale, and a global rating were made at baseline and at 6, 12, 24, 36, 48 and 60 months. Three outcome groups were characterized: responders, unchanged and deteriorated. Additional outcome measures were time until nursing home placement, and mortality rate. At 6 months –75%, at 12 months –42%, at 24 months –20%, and after that 10% of the patients still on medication had improved or remained stable. The mortality rate did not differ between the outcome groups. Response to tacrine treatment at 6 or 12 months was found to predict a prolonged time until nursing home placement. No predictors for a positive treatment response could be identified at baseline.

Tacrine and rate of progression in Alzheimer's disease--relation to ApoE allele genotype

Summary. Today, cognitive impairment can be successfully treated with acetylcholine esterase inhibitors (AChE-I) in many, but not all, patients with Alzheimers disease (AD). To investigate the relation between tacrine treatment, inheritance of ApoE ε4 alleles, and rate of progression, the differences in MMSE and CIBIC scores (efficacy parameters) after 6 and 12 months of tacrine (an AChE-I) treatment were investigated in 145 AD patients. Of these, 84 were ApoE ε4-positive (ApoE4) and 61 were ApoE ε4-negative (ApoE2-3). No differences were found after 6 months of treatment, but after 12 months the CIBIC scores revealed that the ApoE4 patients had declined more than the ApoE2-3 patients (p < 0.05). No differences were found for the last 6 months of treatment. The results primarily suggest a faster rate of decline in the ApoE4 AD compared to the ApoE2-3, but may also reflect that ApoE ε4 genotype inheritance is a negative predictor of treatment effect of tacrine in AD patients.