Hiroyuki Shimada

We previously identified a novel mutation in amyloid precursor protein from a Japanese pedigree of familial Alzheimer’s disease, FAD (Osaka). Our previous positron emission tomography (PET) study revealed that amyloid β (Aβ) accumulation was negligible in two sister cases of this pedigree, indicating a possibility that this mutation induces dementia without forming senile plaques. To further explore the relationship between Aβ, tau and neurodegeneration, we performed tau and Aβ PET imaging in the proband of FAD (Osaka) and in patients with sporadic Alzheimer’s disease (SAD) and healthy controls (HCs). The FAD (Osaka) patient showed higher uptake of tau PET tracer in the frontal, lateral temporal, and parietal cortices, posterior cingulate gyrus and precuneus than the HCs (>2.5 SD) and in the lateral temporal and parietal cortices than the SAD patients (>2 SD). Most noticeably, heavy tau tracer accumulation in the cerebellum was found only in the FAD (Osaka) patient. Scatter plot analysis of the two tracers revealed that FAD (Osaka) exhibits a distinguishing pattern with a heavy tau burden and subtle Aβ accumulation in the cerebral cortex and cerebellum. These observations support our hypothesis that Aβ can induce tau accumulation and neuronal degeneration without forming senile plaques.

Alzheimer’s disease is believed to begin with synaptic dysfunction caused by soluble Aβ oligomers. When this oligomer hypothesis was proposed in 2002, there was no direct evidence that Aβ oligomers actually disrupt synaptic function to cause cognitive impairment in humans. In patient brains, both soluble and insoluble Aβ species always coexist, and therefore it is difficult to determine which pathologies are caused by Aβ oligomers and which are caused by amyloid fibrils. Thus, no validity of the oligomer hypothesis was available until the Osaka mutation was discovered. This mutation, which was found in a Japanese pedigree of familial Alzheimer’s disease, is the deletion of codon 693 of APP gene, resulting in mutant Aβ lacking the 22nd glutamate. Only homozygous carriers suffer from dementia. In vitro studies revealed that this mutation has a very unique character that accelerates Aβ oligomerization but does not form amyloid fibrils. Model mice expressing this mutation demonstrated that all pathologies of Alzheimer’s disease can be induced by Aβ oligomers alone. In this review, we describe the story behind the discovery of the Osaka mutation, summarize the mutant’s phenotypes, and propose a mechanism of its recessive inheritance.

Objective This Phase 2 study assessed the performance of positron emission tomography (PET) brain images made with Flutemetamol F 18 Injection in detecting β-amyloid neuritic plaques in Japanese subjects. Methods Seventy subjects (25 with probable Alzheimer’s disease (pAD), 20 with amnestic mild cognitive impairment (aMCI), and 25 cognitively normal healthy volunteers[HVs]) underwent PET brain imaging after intravenous Flutemetamol F 18 Injection (185 MBq). Images were interpreted as normal or abnormal for neuritic plaque density by each of five non-Japanese and five Japanese readers who were blinded to clinical data. The primary efficacy analysis (based on HV and pAD data) was the agreement of the non-Japanese readers’ image interpretations with the clinical diagnosis, resulting in estimates of positive percent agreement (PPA; based on AD subjects; similar to sensitivity) and negative percent agreement (NPA; based on HVs; similar to specificity). Secondary analyses included PPA and NPA for the Japanese readers; inter-reader agreement (IRA); intra-reader reproducibility (IRR); quantitative image interpretations (standardized uptake value ratios [SUVRs]) by diagnostic subgroup; test–retest variability in five pAD subjects; and safety. Results PPA was 92% for all non-Japanese readers and ranged from 88 to 92% for the Japanese readers. NPA ranged from 96 to 100% for both the non-Japanese readers and the Japanese readers. The majority image interpretations (the interpretations made independently by ≥3 of 5 readers) resulted in PPA values of 92 and 92% and NPA values of 100 and 96% for the non-Japanese and Japanese readers, respectively. IRA and IRR were strong. Composite SUVR values (mean of multiple regional values) allowed clear differentiation between pAD subjects and HVs. Test–retest variability ranged from 1.14 to 2.27%, and test–retest agreement of the blinded visual interpretations was 100% for all readers. Flutemetamol F 18 Injection was generally well tolerated. Conclusions The detection of brain neuritic plaques in Japanese subjects using [¹⁸F]Flutemetamol PET images gave results highly consistent with clinical diagnosis, with non-Japanese and Japanese readers giving similar results. Inter-reader agreement and intra-reader reproducibility were high for both sets of readers. Visual delineation of abnormal and normal scans was corroborated by quantitative assessment, with low test–retest variability. Trial registration Clinicaltrials.gov registration number NCT02813070.

Aspiration pneumonia (AP) following cerebral infarction (CI) has been considered as one of its most serious complications. Nevertheless, there are no reports on the association between the type or location of CI and the incidence of AP. In addition, the association between dysphagia, which leads to aspiration, and the type or location of CI has never been investigated. Therefore we hypothesized that the laterality of CI affects the development of both dysphagia and AP. We performed a retrospective cohort study to examine the association between the laterality of CI and the incidence of dysphagia and AP in 133 patients. AP was found in 6.0% of the group with left CI and in 0.8% of the group with right CI. A univariate logistic regression analysis revealed that left CI was a significant predictor of AP (hazard ratio, 8.81; 95% confidence interval, 1.07-72.59; p = 0.043). Left CI was a significant predictor of AP even after adjusting for age, sex, CI type, or presence of diabetes mellitus. In addition, although the frequency of dysphagia as the direct cause of AP did not differ according to laterality, the frequency of AP that ensued from dysphagia in the left CI group was greater than that observed in the right CI group. The group with left CI from the motor cortex to the internal capsule complicated by dysphagia exhibited a high risk of AP.

Aim: Decreased amyloid β (Aβ) clearance from the brain to blood might play a key role in the development of Alzheimer's disease (AD). Aβ is normally bound to and transported by albumin in blood, thus possibly maintaining constant concentration of free Aβ in the blood. We therefore hypothesized that decreased blood levels of albumin‐Aβ complexes could be associated with decreased Aβ removal from the brain to blood, resulting in Aβ accumulation in the brain.Methods: We carried out a cross‐sectional investigation of the association between serum levels of albumin‐Aβ complexes (SLAAC) and AD prevalence in 89 patients who visited our outpatient clinic, and gave written informed consent between August 2008 and May 2012.Results: We confirmed 45 cases of AD. Low SLAAC was associated with an increased prevalence of AD (OR 0.27; 95% CI 0.14–0.51) in a univariable logistic model and multivariable logistic models. In addition, decreased SLAAC was associated with decreased levels of Aβ42 in CSF (r = 0.38, P = 0.0221) and increased levels of p‐tau in CSF (r = −0.43, P = 0.0090), findings that have been shown to be associated with AD progression.Conclusions: This novel method might be very useful for monitoring of the progression of AD. Geriatr Gerontol Int 2014; 14: 716–723.

A recent meta-analysis on the UCHL1 S18Y variant and Parkinson’s disease (PD) showed a significant inverse association between the Y allele and PD; the individual studies included in that meta-analysis, however, have produced conflicting results. We examined the relationship between UCHL1 S18Y single nucleotide polymorphism (SNP) and sporadic PD in Japan. Included were 229 cases within 6 years of onset of PD, defined according to the UK PD Society Brain Bank clinical diagnostic criteria. Controls were 357 inpatients and outpatients without neurodegenerative disease. Adjustment was made for sex, age, region of residence, smoking, and caffeine intake. Compared with subjects with the CC or CA genotype of UCHL1 S18Y SNP, those with the AA genotype had a significantly increased risk of sporadic PD: the adjusted OR was 1.57 (95 % CI: 1.06 − 2.31). Compared with subjects with the CC or CA genotype of UCHL1 S18Y and the CC or CT genotype of SNCA SNP rs356220, those with the AA genotype of UCHL1 S18Y and the TT genotype of SNP rs356220 had a significantly increased risk of sporadic PD; the interaction, however, was not significant. Our previous investigation found significant inverse relationships between smoking and caffeine intake and PD in this population. There were no significant interactions between UCHL1 S18Y and smoking or caffeine intake affecting sporadic PD. This study reveals that the UCHL1 S18Y variant is a risk factor for sporadic PD. We could not find evidence for interactions affecting sporadic PD between UCHL1 S18Y and SNCA SNP rs356220, smoking, or caffeine intake.

Parkinson's disease (PD) is characterized by alterations in dopaminergic neurotransmission. Genetic polymorphisms involved in dopaminergic neurotransmission may influence susceptibility to PD. We investigated the relationship of catechol-O-methyltransferase (COMT), monoamine oxidase B (MAOB), dopamine receptor (DR) D2 and DRD4 polymorphisms and PD risk with special attention to the interaction with cigarette smoking among 238 patients with PD and 369 controls in a Japanese population. Subjects with the AA genotype of MAOB rs1799836 showed a significantly increased risk of PD (odds ratio (OR) = 1.70, 95% confidence interval (CI) = 1.12 - 2.58) compared with the AG and GG genotypes combined. The AA genotype of COMT rs4680 was marginally associated with an increased risk of PD (OR = 1.86, 95% CI = 0.98 - 3.50) compared with the GG genotype. The DRD2 rs1800497 and DRD4 rs1800955 polymorphisms showed no association with PD. A COMT -smoking interaction was suggested, with the combined GA and AA genotypes of rs4680 and non-smoking conferring significantly higher risk (OR = 3.97, 95% CI = 2.13 - 7.41) than the AA genotype and a history of smoking (P for interaction = 0.061). No interactions of smoking with other polymorphisms were observed. The COMT rs4680 and MAOB rs1799836 polymorphisms may increase susceptibility to PD risk among Japanese. Future studies involving larger control and case populations and better pesticide exposure histories will undoubtedly lead to a more thorough understanding of the role of the polymorphisms involved in the dopamine pathway in PD.

Amyloid imaging has been used to detect amyloid deposition in the brain. We performed Pittsburgh compound B (PiB)-positron emission tomography on 63 patients with dementia having cognitive decline or memory disturbance. In addition, we measured the patients' apolipoprotein E4 (apo E4) status and cerebrospinal fluid (CSF) levels of amyloid-β (Aβ)1-42, tau, and P-tau. Finally, the patients were diagnosed as having probable Alzheimer disease (AD) on the basis of their neuropsychological findings and because they met the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association criteria. Among the patients diagnosed with probable AD, 10 patients were PiB negative. The CSF levels of P-tau and tau in PiB-negative patients were significantly lower than those in the PiB-positive patients. In addition, the CSF levels of Aβ1-42 in the PiB-negative patients were significantly higher than those in the PiB-positive patients. None of the PiB-negative patients were apo E4 carriers. These results suggest that the PiB-negative patient group included not only AD patients but also non-AD-type dementia patients. However, our finding is based on a relatively small number of patients and therefore should be replicated in a larger cohort. In addition, it will be necessary to categorize these participants by longitudinal follow-up and postmortem pathological examinations.

We described the cases of two patients with dementia associated with motor neuron disease, the former with frontotemporal dementia (FTD) and the latter with Alzheimer's disease (AD), studied by the Pittsburgh compound B-positron emission tomography (PIB-PET). In the FTD patient, the PIB-PET revealed no amyloid accumulation in the cortex, whilst in the AD patient showed amyloid accumulation mainly in the frontal, parietal and lateral temporal lobes, besides the posterior cingulate gyrus and the precuneus. Thus, PIB-PET might facilitate the discrimination of different proteinopathies that cause neurodegenerative diseases, as dementia associated with ALS.