Ove Almkvist

Impaired cerebral glucose metabolism and cognitive functioning predict deterioration in mild cognitive impairment

The objective of this study was to assess whether reduced glucose metabolism (rCMRGlu) and cognitive functioning could predict development of Alzheimers disease (AD) in subjects with mild cognitive impairment (MCI). Twenty MCI patients underwent baseline and follow-up investigations of rCMRGlu, as measured by PET, and cognitive function measured by neuropsychological test assessments. Subjects were clinically followed up with an average interval of 36.5 months. Two groups were obtained after the second clinical assessment. Nine patients were diagnosed as AD and classified as progressive MCI (P-MCI), whereas 11 patients remained clinically stable and were classified as stable MCI (S-MCI). There were no differences in demographic variables or baseline MMSE between the two subgroups. Logistic regression indicated the two variables that most effectively predicted future development of AD were rCMRGlu from the left temporoparietal area and performance on the block design. These combined measures gave an optimal 90% correct classification rate, whereas only rCMRGlu or neuropsychology alone gave 75% and 65% correct classification, respectively. Measures of temporoparietal cerebral metabolism and visuospatial function may aid in predicting the evolution to AD for patients with MCI.

Brain regions associated with episodic retrieval in normal aging and Alzheimer’s disease

Objective: To examine patterns of brain activation during verbal episodic retrieval in normal elderly subjects and patients in an early phase of AD. Background: It is established that 1) a profound episodic memory impairment is a cardinal symptom of AD; and 2) some of the earliest brain changes in this disease occur in regions critical to episodic memory, such as the hippocampus and neighboring regions. Yet, it remains largely unknown whether the episodic memory deficit seen in AD is paralleled by concomitant alterations in brain activity during actual task performance in these or other brain areas. Methods: Using PET, blood flow was assessed in normal elderly subjects and patients with early AD during two retrieval conditions involving completion of word stems: baseline and cued recall. Results: The patients with AD showed a marked performance deficit in cued recall, although the two groups were indistinguishable in the baseline task condition. Both groups showed bilateral activity in orbital and dorsolateral prefrontal cortex, left precuneus, and right cerebellum, as well as decreased activity in distinct left temporal regions during cued recall. The normal elderly alone activated the left parietal cortex and the left hippocampal formation during episodic retrieval. By contrast, AD-related increases in activity during cued recall were observed in the left orbital prefrontal cortex and left cerebellum. Conclusions: The similar patterns of activations in the two groups suggest that a large distributed network involved in episodic memory retrieval functions relatively normally in early AD. Those retrieval activations seen in the normal elderly, as opposed to the patients, may reflect AD-related failures in semantic processing and successful recollection of the target information, respectively. Finally, the AD-related increases in activity were interpreted in terms of compensatory reactions to the difficulties in performing the episodic memory task.

Sustained cholinesterase inhibition in AD patients receiving rivastigmine for 12 months

Objective To study the long-term dual inhibitory effects of rivastigmine on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in patients with AD. MethodsEleven patients with mild AD received rivastigmine for 12 months. Cholinesterase (ChE) activities in the CSF and plasma were assessed colorimetrically. Immunoblot analysis was used to evaluate AChE isoforms. Neuropsychiatric tests were performed throughout the study. ResultsAt 12 months, the mean dose of rivastigmine was 8.6 mg/d and specific activities of ChE in the CSF were lower than baseline values (by 36% for AChE and 45% for BuChE), correlating with parallel reductions in the plasma (27% for AChE and 33% for BuChE). The reduction of specific activities in the CSF, but not in the plasma, appeared to be dependent on the dose and duration of treatment. Scores of some of the neuropsychological tests associated with memory and attention were correlated with both plasma and CSF AChE and BuChE inhibition for up to 6 months. Immunoblot analysis revealed up-regulation of the “read-through” AChE isoform (AChE-R), whereas levels of the synaptic isoform were unchanged. ConclusionsRivastigmine causes persistent inhibition of AChE and BuChE in CSF as well as plasma. The persistent CSF inhibition contrasts with earlier findings after long-term treatment by the reversible ChE inhibitor tacrine, which demonstrated increased AChE activity in the CSF but not in the blood. Rivastigmine’s effects on the preferential up-regulation of the AChE-R isoform may have a favorable effect on disease stabilization.

Positron emission tomography imaging and clinical progression in relation to molecular pathology in the first Pittsburgh Compound B positron emission tomography patient with Alzheimer’s disease

The accumulation of β-amyloid in the brain is an early event in Alzheimer’s disease. This study presents the first patient with Alzheimer’s disease who underwent positron emission tomography imaging with the amyloid tracer, Pittsburgh Compound B to visualize fibrillar β-amyloid in the brain. Here we relate the clinical progression, amyloid and functional brain positron emission tomography imaging with molecular neuropathological alterations at autopsy to gain new insight into the relationship between β-amyloid accumulation, inflammatory processes and the cholinergic neurotransmitter system in Alzheimer’s disease brain. The patient underwent positron emission tomography studies with 18F-fluorodeoxyglucose three times (at ages 53, 56 and 58 years) and twice with Pittsburgh Compound B (at ages 56 and 58 years), prior to death at 61 years of age. The patient showed a pronounced decline in cerebral glucose metabolism and cognition during disease progression, while Pittsburgh Compound B retention remained high and stable at follow-up. Neuropathological examination of the brain at autopsy confirmed the clinical diagnosis of pure Alzheimer’s disease. A comprehensive neuropathological investigation was performed in nine brain regions to measure the regional distribution of β-amyloid, neurofibrillary tangles and the levels of binding of 3H-nicotine and 125I-α-bungarotoxin to neuronal nicotinic acetylcholine receptor subtypes, 3H-L-deprenyl to activated astrocytes and 3H-PK11195 to microglia, as well as butyrylcholinesterase activity. Regional in vivo 11C-Pittsburgh Compound B-positron emission tomography retention positively correlated with 3H-Pittsburgh Compound B binding, total insoluble β-amyloid, and β-amyloid plaque distribution, but not with the number of neurofibrillary tangles measured at autopsy. There was a negative correlation between regional fibrillar β-amyloid and levels of 3H-nicotine binding. In addition, a positive correlation was found between regional 11C-Pittsburgh Compound B positron emission tomography retention and 3H-Pittsburgh Compound B binding with the number of glial fibrillary acidic protein immunoreactive cells, but not with 3H-L-deprenyl and 3H-PK-11195 binding. In summary, high 11C-Pittsburgh Compound B positron emission tomography retention significantly correlates with both fibrillar β-amyloid and losses of neuronal nicotinic acetylcholine receptor subtypes at autopsy, suggesting a closer involvement of β-amyloid pathology with neuronal nicotinic acetylcholine receptor subtypes than with inflammatory processes.

High PIB Retention in Alzheimer's Disease is an Early Event with Complex Relationship with CSF Biomarkers and Functional Parameters

BACKGROUNDnNew in vivo amyloid PET imaging tracers, such as (11)C-PIB, provide possibilities to deeper understand the underlying pathological processes in Alzheimers disease (AD). In this study we investigated how (11)C-PIB retention is related to cerebral glucose metabolism, episodic memory and CSF biomarkers.nnnMETHODnThirty-seven patients with mild AD and 21 patients with mild cognitive impairment (MCI) underwent PET examinations with the amyloid tracer (11)C-PIB, (18)F-FDG for measurement of regional cerebral metabolic rate of glucose (rCMRglc), assessment of episodic memory and assay of cerebral spinal fluid (CSF) levels of amyloid-beta (Abeta(1-42)), total tau and phosphorylated tau respectively. Analyses were performed using Statistical Parametric Mapping (SPM) and regions of interest (ROIs).nnnRESULTSnPooled data from AD and MCI patients showed strong correlations between (11)C-PIB retention, levels of CSF biomarkers (especially Abeta(1-42)), rCMRglc and episodic memory. Analysis of the MCI group alone revealed significant correlations between (11)C-PIB retention and CSF biomarkers and between CSF biomarkers and episodic memory respectively. A strong correlation was observed in the AD group between rCMRglc and episodic memory as well as a significant correlation between (11)C-PIB retention and rCMRglc in some cortical regions. Regional differences were observed as sign for changes in temporal patterns across brain regions.nnnCONCLUSIONSnA complex pattern was observed between pathological and functional markers with respect to disease stage (MCI versus AD) and brain regions. Regional differences over time were evident during disease progression. (11)C-PIB PET and CSF Abeta(42) allowed detection of prodromal stages of AD. Amyloid imaging is useful for early diagnosis and evaluation of new therapeutic interventions in AD.

Responder characteristics to a single oral dose of cholinesterase inhibitor: a double-blind placebo-controlled study with tacrine in Alzheimer patients.

A proportion of Alzheimer’s disease (AD) patients treated for several months with cholinesterase (ChE) inhibitors have shown some favorable response on cognition, but the characteristics of the responders are still unclear. This study attempts to identify the characteristics of individuals with a positive behavioral response after a double-blind randomized administration of a single oral dose of tacrine (40 mg) and placebo to AD patients. Furthermore, the relationship between single-dose and long-term responders are examined. Twenty-four mildly to very mildly demented AD patients participated in the study. They all fulfilled the diagnosis of probable AD according to NINCDS-ADRDA criteria. Active treatment (tacrine 40 mg) and placebo was administered in random order on 2 consecutive days, and the effects were evaluated within 2 h using neuropsychological tests (assessing visuospatial ability, episodic memory and attention), registration of EEG activity and measurement of red blood cells (RBC) acetylcholinesterase (AChE), ChE activity and concentrations of tacrine and its metabolites in plasma. Results demonstrated significant improvement, tacrine compared to placebo, in measures of attention, but not in episodic memory or visuospatial ability. A single-dose response was therefore defined in terms of improvement in attention. The tacrine plasma concentration (pcTHA) showed a positively skewed distribution (mean ± SD: 10.5 ± 11.8, range: 1.0–51.8 ng/ml). There were no significant differences between single-dose responders compared to nonresponders in pcTHA, metabolites of tacrine, inhibition of AChE in RBC, tau levels in CSF, AChE activity in CSF or plasma and demographic variables. However, single-dose responders showed a higher right frontal alpha/theta ratio on EEG and had lower glucose metabolism in the parietal-temporal association cortex at baseline. In addition, the frequency of apolipoprotein E (APOE) Ε4 alleles was higher in responders. Interestingly, the single-dose response was related to the long-term response, although not significantly, which probably was due to lack of power. To conclude, the present study identified single-dose responders in terms of improved attentional performance associated with a relatively higher alpha/theta activity in the right frontal regions of the brain measured on EEG and predominance of APOE Ε4 allele.

Increasing CSF phospho-tau levels during cognitive decline and progression to dementia

BACKGROUNDnLittle is known about longitudinal changes of cerebrospinal fluid (CSF) biomarkers during cognitive decline in neurodegenerative disease progression.nnnOBJECTIVEnTo investigate longitudinal changes in CSF biomarkers--total-tau (T-tau), phospho-tau (P-tau) and beta-amyloid (Abeta42)--during cognitive decline.nnnMETHODSnForty memory clinic patients (47.5% females), aged 61.3+/-7.6 (S.D.) years, non-demented at baseline, underwent lumbar puncture and neuropsychological testing at two occasions. Baseline mean MMSE-score was 28.3+/-1.8. Patients were divided into three groups based on baseline memory functioning; severely impaired (SIM), moderately impaired (MIM) and no impairment (NIM).nnnRESULTSnThere was a significant increase in P-tau in the SIM-group during follow-up, while P-tau in MIM and NIM did not change. Eighty-three percent of the SIM-patients converted to dementia (80% AD), while most MIM- and NIM-patients remained non-demented. T-tau- and Abeta42-levels did not change in any of the memory groups during follow-up.nnnCONCLUSIONnIncreasing P-tau levels during cognitive decline and conversion to dementia suggest that P-tau may be useful as a longitudinal marker of the neurodegenerative process.

Inhibition of acetylcholinesterase in CSF versus brain assessed by 11C-PMP PET in AD patients treated with galantamine

The relationship between acetylcholinesterase (AChE) activity in the CSF and brain of patients with Alzheimers disease (AD) was investigated in 18 mild AD patients following galantamine treatment. The first 3 months of the study had a randomized double-blind placebo-controlled design, during which 12 patients received galantamine (16-24 mg/day) and six patients placebo. This was followed by 9 months galantamine treatment in all patients. Activities and protein levels of both the read-through AChE (AChE-R) and the synaptic (AChE-S) variants in CSF were assessed in parallel together with the regional brain AChE activity by (11)C-PMP and PET. The AChE-S inhibition was 30-36% in CSF, which correlated well with the in vivo AChE inhibition in the brain. No significant AChE inhibition was observed in the placebo group. The increased level of the AChE-R protein was 16% higher than that of AChE-S. Both the AChE inhibition and the increased level of AChE-R protein positively correlated with the patients performance in cognitive tests associated with visuospatial ability and attention. In conclusion, AChE levels in CSF closely mirror in vivo brain AChE levels prior to and after treatment with the cholinesterase inhibitors. A positive cognitive response seems to dependent on the AChE inhibition level, which is balanced by an increased protein level of the AChE-R variant in the patients.

Differential CSF butyrylcholinesterase levels in Alzheimer's disease patients with the ApoE ε4 allele in relation to cognitive function and cerebral glucose metabolism.

Butyrylcholinesterase (BuChE) is increased in the cerebral cortex of Alzheimers disease (AD) patients, particularly those carrying epsilon4 allele of the apolipoprotein E gene (ApoE) and certain BuChE variants that predict increased AD risk and poor response to anticholinesterase therapy. We measured BuChE activity and protein level in CSF of eighty mild AD patients in relation to age, gender, ApoE epsilon4 genotype, cognition and cerebral glucose metabolism (CMRglc). BuChE activity was 23% higher in men than women (p<0.03) and 40-60% higher in ApoE epsilon4 negative patients than in those carrying one or two epsilon4 alleles (p<0.0004). CSF BuChE level correlated with cortical CMRglc. Patients with high to moderate CSF BuChE showed better cognitive function scores than others. We hypothesize that CSF BuChE varies inversely with BuChE in cortical amyloid plaques. Thus, low BuChE in a patients CSF may predict extensive incorporation in neuritic plaques, increased neurotoxicity and greater central neurodegeneration.

Identifying Patients at High and Low Risk of Cognitive Decline Using Rey Auditory Verbal Learning Test among Middle-Aged Memory Clinic Outpatients

Objectives: To investigate whether application of cutoff levels in an episodic memory test (Rey Auditory Verbal Learning Test, RAVLT) is a useful method for identifying patients at high and low risk of cognitive decline and subsequent dementia. Methods: 224 patients with memory complaints (mean age = 60.7 years, mean MMSE = 28.2) followed-up at a memory clinic over ≈3 years were assigned retrospectively to one of three memory groups from their baseline results in RAVLT [severe (SIM), moderate (MIM) or no impairment (NIM)]. These groups were investigated regarding cognitive decline. Results: Patients assigned to SIM showed significant cognitive decline and progressed to dementia at a high rate, while a normal performance in RAVLT at baseline (NIM) predicted normal cognition after 3 years. Patients with MIM constituted a heterogeneous group; some patients deteriorated cognitively, while the majority remained stable or improved. Conclusions: The application of cutoff levels in RAVLT at baseline showed that patients with severely impaired RAVLT performance were at a high risk of cognitive decline and progression to dementia, while patients with normal RAVLT results did not show cognitive decline during 3 years. Furthermore, the initial degree of memory impairment was decisive in the cognitive prognosis 3 years later.