Ahmadul Kadir

PET imaging of cortical 11C-nicotine binding correlates with the cognitive function of attention in Alzheimer´s disease.

RationalePatients suffering from Alzheimer’s disease (AD) experience a marked reduction in cortical nicotinic acetylcholine receptors (nAChRs). In particular, selective loss of the α4β2 nAChR subtype was observed in postmortem AD brain tissue. The α4 and α7 nAChR subunits were suggested to play an important role in cognitive function. Positron emission tomography (PET) has so far been used to visualize neuronal nAChRs in vivo by 11C-nicotine binding.ObjectivesTo investigate the relationship between measures of cognitive function and in vivo 11C-nicotine binding in mild AD brain as assessed by PET.Materials and methodsTwenty-seven patients with mild AD were recruited in this study. A dual tracer model with administration of 15O-water for regional cerebral blood flow and (S)(−)11C-nicotine was used to assess nicotine binding sites in the brain by PET. Cognitive function was assessed using neuropsychological tests of global cognition, episodic memory, attention, and visuospatial ability.ResultsMean cortical 11C-nicotine binding significantly correlated with the results of attention tests [Digit Symbol test (r=−0.44 and p=0.02) and Trail Making Test A (TMT-A) (r=0.42 and p=0.03)]. No significant correlation was observed between 11C-nicotine binding and the results of tests of episodic memory or visuospatial ability. Regional analysis showed that 11C-nicotine binding in the frontal and parietal cortex, which are the main areas for attention, correlated significantly with the Digit Symbol test and TMT-A results.ConclusionCortical nicotinic receptors in vivo in mild AD patients are robustly associated with the cognitive function of attention.

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.

Dynamic changes in PET amyloid and FDG imaging at different stages of Alzheimer's disease

In this study 5 patients with mild cognitive impairment (MCI) and 9 Alzheimers disease (AD) patients underwent respectively 3- and 5-year follow-up positron emission tomography (PET) studies with N-methyl [(11)C] 2-(4-methylaminophenyl)-6-hydroxy-benzothiazole ((11)C-PIB) and (18)F-fluorodeoxyglucose ((18)F-FDG) to understand the time courses in AD disease processes. Significant increase in PIB retention as well as decrease in regional cerebral metabolic rate of glucose (rCMRglc) was observed at group level in the MCI patients while no significant change was observed in cognitive function. At group level the AD patients showed unchanged high PIB retention at 5-year follow-up compared with baseline. At the individual level, increased, stable, and decreased PIB retention were observed while disease progression was reflected in significant decrease in rCMRglc and cognition. In conclusion, after a long-term follow-up with PET, we observed an increase in fibrillar amyloid load in MCI patients followed by more stable level in clinical AD patients. The rCMRglc starts to decline in MCI patients and became more pronounced in clinical stage which related to continuous decline in cognition.

Effect of phenserine treatment on brain functional activity and amyloid in Alzheimer's disease

The effects of (−)‐phenserine (phenserine) and placebo/donepezil treatment on regional cerebral metabolic rate for glucose (rCMRglc) and brain amyloid load were investigated by positron emission tomography in 20 patients with mild Alzheimers disease in relation to cerebrospinal fluid (CSF) and plasma biomarkers, and cognitive function.

Encapsulated Cell Biodelivery of Nerve Growth Factor to the Basal Forebrain in Patients with Alzheimer’s Disease

Background/Aims: Degeneration of cholinergic neurons in the basal forebrain correlates with cognitive decline in patients with Alzheimer’s disease (AD). Targeted delivery of exogenous nerve growth factor (NGF) has emerged as a potential AD therapy due to its regenerative effects on the basal forebrain cholinergic neurons in AD animal models. Here we report the results of a first-in-man study of encapsulated cell (EC) biodelivery of NGF to the basal forebrain of AD patients with the primary objective to explore safety and tolerability. Methods: This was an open-label, 12-month study in 6 AD patients. Patients were implanted stereotactically with EC-NGF biodelivery devices targeting the basal forebrain. Patients were monitored with respect to safety, tolerability, disease progression and implant functionality. Results: All patients were implanted successfully with bilateral single or double implants without complications or signs of toxicity. No adverse events were related to NGF or the device. All patients completed the study, including removal of implants at 12 months. Positive findings in cognition, EEG and nicotinic receptor binding in 2 of 6 patients were detected. Conclusions: This study demonstrates that surgical implantation and removal of EC-NGF biodelivery to the basal forebrain in AD patients is safe, well tolerated and feasible.

Target-Specific PET Probes for Neurodegenerative Disorders Related to Dementia

Dementia is a highly prevalent problem causing considerable disability and mortality and exacting great costs to individuals, their families, and society. The 4 most common neurodegenerative disorders that cause dementia—Alzheimer disease, frontotemporal dementia, dementia with Lewy bodies, and dementia in Parkinson disease—have different underlying etiologies and pathogenetic mechanisms. There is a great need for early diagnostic markers; functional brain imaging may therefore assist in the detection and differential diagnosis of dementia due to neurodegenerative diseases. Functional imaging such as PET allows in vivo imaging of functional brain activity indicating cerebral blood flow and cerebral glucose metabolism, and PET allows imaging of neurotransmitter activity, including that of the cholinergic, dopaminergic, and serotonergic systems. New PET neuroimaging tracers are being developed for detecting pathologic parameters such as amyloid plaque and microglial activity. The development of molecular imaging is important for early diagnosis of dementia, selection of patients for therapies, and evaluation of therapies.

Long-term effects of galantamine treatment on brain functional activities as measured by PET in Alzheimer's disease patients.

The effects of galantamine (16 to 24 mg/day) treatment on brain functional activities (blood flow and glucose metabolism) were examined in 18 patients with mild Alzheimers disease (AD) in relation to brain acetylcholinesterase (AChE) activity and nicotinic receptors and cognitive function. The study consisted of an initial double-blind phase of three months (short-term) followed by an open-label phase until twelve months after the beginning of the study (long-term). The AD patients underwent positron emission tomography (PET) studies with the tracers [15O]-H2O for measurement of regional cerebral blood flow (rCBF) at baseline, 3 weeks, 3 and 12 months treatment, and [18F]-fluoro-deoxyglucose (FDG) for measurement of regional cerebral metabolic rate for glucose (rCMRglc) at baseline and 12 months. A battery of neuropsychological assessments was performed on each patient in order to follow changes in cognition during the treatment period. Throughout the study, different cortical areas showed significant increases in rCBF after galantamine treatment. rCBF positively correlated with AChE activity, nicotinic receptors and cognition. In addition to these positive changes, an increase in rCMRglc in the frontal brain region and stabilization in other cortical areas was observed after 12 months galantamine treatment. This stabilization in rCMRglc was also correlated with a stabilization of cognition. Our results ultimately suggest that treatment with galantamine has a long-term positive effect on brain perfusion and rCMRglc and stabilizes cognition.

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.

Changes in CSF cholinergic biomarkers in response to cell therapy with NGF in patients with Alzheimer's disease

The extensive loss of central cholinergic functions in Alzheimers disease (AD) brain is linked to impaired nerve growth factor (NGF) signaling. The cardinal cholinergic biomarker is the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT), which has recently been found in cerebrospinal fluid (CSF). The purpose of this study was to see if EC‐NGF therapy will alter CSF levels of cholinergic biomarkers, ChAT, and acetylcholinesterase.

Correlations between Alzheimer’s Disease Cerebrospinal Fluid Biomarkers and Cerebral Glucose Metabolism after 12 Months of Phenserine Treatment

New therapeutic strategies in Alzheimers disease (AD) are focused on targeting amyloid-β (Aβ) to modify the underlying cause of the disease rather than just the symptoms. The aim of this study was to investigate the long-term effects of treatment with the anti-Aβ compound phenserine on (i) cerebrospinal fluid (CSF) biomarkers for Aβ and tau pathology and (ii) brain metabolism as assessed by the regional cerebral metabolic rate for glucose (rCMRglc), using positron emission tomography. Twenty patients with mild AD were included in the study and after 12 months treatment with phenserine, CSF Aβ40 and α- and β-secretase-cleaved soluble amyloid-β protein precursor (sAβPP) levels had significantly increased and rCMRglc had stabilized. Levels of CSF Aβ40 and sAβPP correlated positively with rCMRglc and cognition while CSF Aβ42 levels, the Aβ42/40 ratio, P-tau, and T-tau correlated negatively with rCMRglc and cognition. In summary, long-term phenserine treatment resulted in increased levels of CSF Aβ40, sAβPPα, and sAβPPβ, which positively correlated with improvements in rCMRglc and cognition. The study illustrates the value of using biomarkers in the CSF and brain for evaluation of drug effects.