Juha O. Rinne

C-11-PiB PET assessment of change in fibrillar amyloid-beta load in patients with Alzheimer's disease treated with bapineuzumab: a phase 2, double-blind, placebo-controlled, ascending-dose study

BACKGROUND Carbon-11-labelled Pittsburgh compound B ((11)C-PiB) PET is a marker of cortical fibrillar amyloid-beta load in vivo. We used (11)C-PiB PET to investigate whether bapineuzumab, a humanised anti-amyloid-beta monoclonal antibody, would reduce cortical fibrillar amyloid-beta load in patients with Alzheimers disease. METHODS Patients with mild-to-moderate Alzheimers disease were randomly assigned to receive intravenous bapineuzumab or placebo in a ratio of seven to three in three ascending dose groups (0.5, 1.0, or 2.0 mg/kg). Each dose group was enrolled after safety review of the previous group. Randomisation was by interactive voice response system; masking was achieved with numbered kit allocation. Patients, investigators, study site personnel, sponsor staff, and carers were masked to treatment. Patients received up to six infusions, 13 weeks apart, and had (11)C-PiB PET scans at baseline and at weeks 20, 45, and 78. The primary outcome was the difference between the pooled bapineuzumab group and the pooled placebo group in mean change from screening to week 78 in (11)C-PiB cortical to cerebellar retention ratio averaged across six cortical regions of interest. Analysis was by modified intention to treat. This study is registered with EudraCT, number 2004-004120-12; ISRCTN17517446. FINDINGS 28 patients were assigned to bapineuzumab (n=20) or placebo (n=8). 19 patients in the bapineuzumab group and seven in the placebo group were included in the modified intention-to-treat analysis. Estimated mean (11)C-PiB retention ratio change from baseline to week 78 was -0.09 (95% CI -0.16 to -0.02; p=0.014) in the bapineuzumab group and 0.15 (95% CI 0.02 to 0.28; p=0.022) in the placebo group. Estimated mean difference in (11)C-PiB retention ratio change from baseline to week 78 between the bapineuzumab group and the placebo group was -0.24 (95% CI -0.39 to -0.09; p=0.003). Differences between the bapineuzumab group and the placebo group in the individual regions of interest were similar to the overall mean difference. Adverse events were typically mild to moderate in severity and transient. Two patients in the 2.0 mg/kg bapineuzumab group had transient cerebral vasogenic oedema. INTERPRETATION Treatment with bapineuzumab for 78 weeks reduced cortical (11)C-PiB retention compared with both baseline and placebo. (11)C-PiB PET seems to be useful in assessing the effects of potential Alzheimers disease treatments on cortical fibrillar amyloid-beta load in vivo. FUNDING Elan Pharmaceuticals and Wyeth Research.

PET amyloid ligand [11C]PIB uptake is increased in mild cognitive impairment

Background: Patients with mild cognitive impairment (MCI) have increased risk to develop Alzheimer disease (AD). In AD increased brain amyloid burden has been demonstrated in vivo with PET using N-methyl-[11C]2-(4′-methylaminophenyl)-6-hydroxybenzothiazole ([11C]PIB) as a tracer. Objective: To investigate whether patients with amnestic MCI would show increased [11C]PIB uptake, indicating early AD process. Methods: We studied 13 patients with amnestic MCI and 14 control subjects with PET using [11C]PIB as tracer. Parametric images were computed by calculating the region-to-cerebellum ratio in each voxel over 60 to 90 minutes. Group differences in [11C]PIB uptake were analyzed with statistical parametric mapping (SPM) and automated region-of-interest (ROI) analysis. Results: The SPM analysis showed that patients with MCI had significantly higher [11C]PIB uptake vs control subjects in the frontal, parietal, and lateral temporal cortices as well as in the posterior cingulate showing the most prominent differences. These results were supported by the automated ROI analysis in which MCI patients showed in comparison with healthy control subjects increased [11C]PIB uptake in the frontal cortex (39% increase from the control mean, p < 0.01), the posterior cingulate (39%, p < 0.01), the parietal (31%, p < 0.01) and lateral temporal (28%, p < 0.001) cortices, putamen (17%, p < 0.05), and caudate (25%, p < 0.05). Individually, in the frontal cortex and posterior cingulate, 8 of 13 patients with MCI had [11C]PIB uptake values above 2 SD from the control mean. MCI subjects having at least one APOE ε4 allele tended to have higher [11C]PIB uptake than MCI subjects without APOE ε4. Conclusions: At group level the elevated N-methyl-[11C]2-(4′-methylaminophenyl)-6-hydroxybenzothiazole ([11C]PIB) uptake in patients with mild cognitive impairment (MCI) resembled that seen in Alzheimer disease (AD). At the individual level, about half of the MCI patients had [11C]PIB uptake in the AD range, suggestive of early AD process.

Age-related dopamine D2/D3 receptor loss in extrastriatal regions of the human brain.

Loss of dopamine D2-like receptors in the striatum has been associated with both normal human aging and impairment of cognitive and motor functions in the elderly. To investigate whether there are age-associated changes in dopamine D2 and D3 receptor subtypes (D2/3Rs) outside the striatum, a D2/3R selective high-affinity radioligand [11C]FLB 457 was used in positron emission tomography (PET) examinations for 24 normal healthy male subjects (age range 19-74 years). Significant age-related declines of D2/3Rs were detected in all the brain regions studied: the anterior cingulate cortex (decline of 13% per increase of a decade in age, P < 0.001). the frontal cortex (11%, P < 0.001), the lateral temporal cortex (10%, P < 0.001), the hippocampus (10%, P < 0.01), the medial temporal cortex (9%, P < 0.001), the amygdala (7%, P < 0.01), the medial thalamus (6%, P < 0.001) and the lateral thalamus (5%, P < 0.01). The rate of D2/3R decline was significantly faster in the frontal cortex as compared to the medial temporal cortex (P < 0.05, Bonferroni corrected) and as compared to the medial thalamus (P < 0.05, Bonferroni corrected). These results indicate that the previously demonstrated age-related decline in striatal dopamine D2 receptors extends to several extrastriatal regions in normal human males. Further, the rate of D2/3R decline may be faster in the frontal cortex as compared to the temporal and thalamic regions.

An FDOPA PET study in patients with periodic limb movement disorder and restless legs syndrome

Article abstract The authors investigated nine drug-naïve patients with periodic limb movement disorder and restless legs syndrome (PLMD-RLS) and 27 healthy controls with PET using 6-[18F]fluoro-l-dopa (FDOPA). In the patients, the FDOPA uptake (Kiocc) in the caudate nucleus was 88% and in the putamen 89% of the control mean values. This equal affection of the caudate and the putamen differs, for example, from the dopaminergic dysfunction in Parkinson’s disease, which affects the putamen earlier and more severely than the caudate. The current results indicate mild nigrostriatal presynaptic dopaminergic hypofunction in PLMD-RLS.

Alpha-synuclein-immunoreactive cortical Lewy bodies are associated with cognitive impairment in Parkinson's disease

Abstract Amygdala, hippocampus and six cortical gyri were examined for the Lewy body (LB) degeneration and Alzheimer’s disease (AD) type changes in 45 patients with Parkinson’s disease (PD). For detection of LBs, the brain areas were stained with an antibody against alpha-synuclein. The extent of neuropathological lesions was investigated in relation to cognitive dysfunction and apolipoprotein E (apoE) ɛ4 allele dosage. At least one cortical LB was found in 95% of cases (43/45). Furthermore, 40% of cases (18/45) had histological findings of definite AD (CERAD class C). Those PD cases with the apoE ɛ4 allele had a significantly greater number of cortical LBs than those without the apoE ɛ4 allele, but this was statistically significant only in precentral, angular and temporal gyri. The LB density correlated better with the number of plaques than with the density of tangles. The number of LBs in several cortical areas correlated significantly with the cognitive impairment. In stepwise linear regression analysis, the number of LBs in the cingulate gyrus and the amount of tangles in the temporal cortex remained statistically significant. When the CERAD class C was excluded, the correlation between cognitive decline and the number of LBs in cortical areas became even more pronounced. A stepwise linear regression analysis in these cases found the number of LBs in the frontal gyrus to be the statistically most significant predictor of cognitive impairment. This study shows, for the first time, that in PD, alpha-synuclein-positive cortical LBs are associated with cognitive impairment independent of AD-type pathology.

Frontal and Temporal Dopamine Release during Working Memory and Attention Tasks in Healthy Humans: a Positron Emission Tomography Study Using the High-Affinity Dopamine D2 Receptor Ligand [11C]FLB 457

Experimental studies on animals have shown that dopamine is a key neurotransmitter in the regulation of working memory (WM) functions in the prefrontal cortex. In humans, blood flow studies show prefrontal involvement in WM functions, but direct evidence for the involvement of the dopaminergic system in WM is lacking. Using positron emission tomography with a recently developed high-affinity dopamine D2 receptor tracer, [11C]FLB 457, we explored frontal, temporal, and parietal D2 receptor availability in 12 healthy volunteers while they were performing verbal WM and sustained attention tasks. During the performance of both tasks, reduced D2 receptor availability was observed in the left ventral anterior cingulate, suggesting an attention or arousal-related increase in dopamine release during these tasks. Compared with the sustained attention task, the verbal WM task reduced D2 receptor availability in the ventrolateral frontal cortex bilaterally and in the left medial temporal structures (amygdala, hippocampus), suggesting that dopamine release in these regions might have a specific role in WM. In addition, correlation analyses indicated that increased dopamine release in the right ventrolateral frontal cortex and the left ventral anterior cingulate during the WM task was associated with faster and more stable WM performance, respectively. Our results indicate that regionally specific components of the frontotemporal dopaminergic network are functionally involved in WM performance in humans.

Regional analysis of FDG and PIB-PET images in normal aging, mild cognitive impairment, and Alzheimer’s disease

ObjectiveThe objective of the study is to compare the diagnostic value of regional sampling of the cerebral metabolic rate of glucose metabolism (MRglc) using [18F]-fluoro-2-deoxyglucose ([18F]FDG)-positron emission tomography (PET) and amyloid-beta pathology using Pittsburgh Compound-B ([11C]PIB)-PET in the evaluation of patients with Alzheimer’s disease (AD) and mild cognitive impairment (MCI) compared to normal elderly (NL).Materials and methodsAD patients, 7 NL, 13 MCI, and 17, received clinical, neuropsychological, magnetic resonance imaging (MRI), FDG, and PIB-PET exams. Parametric images of PIB uptake and MRglc were sampled using automated regions-of-interest (ROI).ResultsAD showed global MRglc reductions, and MCI showed reduced hippocampus (HIP) and inferior parietal lobe (IP) MRglc compared to NL. On PIB, AD patients showed significantly increased uptake in the middle frontal gyrus (MFG), posterior cingulate cortex (PCC), and IP (ps < 0.05). PIB uptake in MCI subjects was either AD or NL-like. HIP MRglc and MFG PIB uptake were the best discriminators of NL from MCI and NL from AD. These two best measures showed high diagnostic agreement for AD (94%) and poor agreement for MCI (54%). For the NL vs. MCI discrimination, combining the two best measures increased the accuracy for PIB (75%) and for FDG (85%) to 90%.ConclusionFor AD, the pattern of regional involvement for FDG and PIB differ, but both techniques show high diagnostic accuracy and 94% case by case agreement. In the classification of NL and MCI, FDG is superior to PIB, but there is only 54% agreement at a case level. Combining the two modalities improves the diagnostic accuracy for MCI.

Voxel-based analysis of PET amyloid ligand [11C]PIB uptake in Alzheimer disease.

Background: PET studies with N-methyl-[11C]2-(4′:-methylaminophenyl)-6-hydroxybenzothiazole ([11C]PIB) have revealed an increased tracer uptake in several brain regions in Alzheimer disease (AD). Objective: To employ voxel-based analysis method to identify brain regions with significant increases in [11C]PIB uptake in AD vs healthy control subjects, indicative of increased amyloid accumulation in these regions. Methods: We studied 17 patients with AD and 11 control subjects with PET using [11C]PIB as tracer. Parametric images were computed by calculating a region-to-cerebellum ratio over 60 to 90 minutes in each voxel. Group differences in [11C]PIB uptake were analyzed with statistical parametric mapping (SPM) and automated region-of-interest (ROI) analysis. Results: SPM showed increased uptake (p < 0.001) in the frontal, parietal, and lateral temporal cortices as well as in the posterior cingulate and the striatum. No significant differences in uptake were found in the primary sensory and motor cortices, primary visual cortex, thalamus, and medial temporal lobe. These results were supported by automated ROI analysis, with most prominent increases in AD subjects in the frontal cortex ([11C]PIB uptake 163% of the control mean) and posterior cingulate (146%) followed by the parietal (146%) and temporal (145%) cortices and striatum (133%), as well as small increases in the occipital cortex (117%) and thalamus (115%). Conclusions: Voxel-based analysis revealed widespread distribution of increased [11C]PIB uptake in Alzheimer disease (AD). These findings are in accordance with the distribution and phases of amyloid pathology in AD, previously documented in postmortem studies.

Assessment of β-Amyloid in a Frontal Cortical Brain Biopsy Specimen and by Positron Emission Tomography With Carbon 11–Labeled Pittsburgh Compound B

OBJECTIVE To compare carbon 11-labeled Pittsburgh Compound B ([11C]PiB) positron emission tomography (PET) findings in patients with and without Alzheimer disease lesions in frontal cortical biopsy specimens. DESIGN Cross-sectional study of [11C]PiB PET findings in patients with or without beta-amyloid (Abeta) aggregates in frontal cortical biopsy specimens. SETTING Two university hospitals in Finland. Patients Ten patients who had undergone intraventricular pressure monitoring with a frontal cortical biopsy (evaluated for Abeta aggregates and hyperphosphorylated tau) for suspected normal-pressure hydrocephalus. INTERVENTIONS [11C]PiB PET and evaluation for cognitive impairment using a battery of neuropsychological tests. MAIN OUTCOME MEASURES Immunohistochemical evaluation for Abeta aggregates and hyperphosphorylated tau in the frontal cortical biopsy specimen and [11C]PiB PET. RESULTS In patients with Abeta aggregates in the frontal cortical biopsy specimen, PET imaging revealed higher [11C]PiB uptake (P < .05) in the frontal, parietal, and lateral temporal cortices and in the striatum as compared with the patients without frontal Abeta deposits. CONCLUSIONS Our study supports the use of noninvasive [11C]PiB PET in the assessment of Abeta deposition in the brain. Large prospective studies are required to verify whether [11C]PiB PET will be a diagnostic aid, particularly in early Alzheimer disease.

A POSTMORTEM STUDY OF BRAIN NICOTINIC RECEPTORS IN PARKINSON'S AND ALZHEIMER'S DISEASE

Brain nicotinic receptors were studied in the frontal cortex, temporal cortex, hippocampus and caudate nucleus in patients with Parkinsons disease (PD), Alzheimers disease (AD) and control. The Bmax and Kd values of (-)-[3H]nicotine binding were determined with a Scatchard analysis. The number of nicotinic receptors declined both in PD and in AD patients in all brain areas examined. The Kd values were unchanged. There was a negative correlation between the degree of dementia in PD patients and the number of nicotinic receptors in the frontal cortex. A similar correlation was seen between the muscarinic/nicotinic receptor ratio in the frontal cortex and the degree of dementia in PD patients. The present findings indicate that nicotinic receptors are affected not only in AD, but also in PD and that dysfunction of the cholinergic system in the frontal cortex is involved in the dementia process in PD.