Alzheimer's disease (AD) is the most common form of dementia. Although uncountable clinical trials have been done to develop the treatment of AD, there are a couple of drugs that can be used only for symptomatic treatment. Therefore, many studies based on the amyloid cascade hypothesis and the tauopathy hypothesis are still ongoing. After the failure of numerous huge Phase III clinical trials, arguments on those hypotheses have arisen and efforts to establish other possible therapeutic strategies based on diverse plausible mechanisms associated with AD have been done as well. One of the new therapeutic targets for AD is the phosphatidylinositol 3-kinase (PI3K)/AKT pathway. In this review, questions on the two hypotheses, the definition of the PI3K/AKT pathway, the relationship between the pathway and AD, and the possibility of the modulation of the pathway as a new therapeutic strategy for AD will be discussed briefly.
Alzheimer Disease* ; Amyloid ; Dementia ; Phosphatidylinositol 3-Kinase ; Tauopathies

The pathological features of Alzheimer's disease are senile plaques which are aggregates of β-amyloid peptides and neurofibrillary tangles in the brain. Neurofibrillary tangles are aggregates of hyperphosphorylated tau proteins, and these induce various other neurodegenerative diseases, such as progressive supranuclear palsy, corticobasal degeneration, frontotemporal lobar degeneration, frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), and chronic traumatic encephalopathy. In the case of Alzheimer's disease, the measurement of neurofibrillary tangles associated with cognitive decline is suitable for differential diagnosis, disease progression assessment, and to monitor the effects of therapeutic treatment. This review discusses considerations for the development of tau ligands for imaging and summarizes the results of the first-in-human and preclinical studies of the tau tracers that have been developed thus far. The development of tau ligands for imaging studies will be helpful for differential diagnosis and for the development of therapeutic treatments for tauopathies including Alzheimer's disease.
Alzheimer Disease ; Brain ; Brain Injury, Chronic ; Chromosomes, Human, Pair 17 ; Diagnosis, Differential ; Disease Progression ; Frontotemporal Dementia ; Frontotemporal Lobar Degeneration ; Ligands ; Neurodegenerative Diseases ; Neurofibrillary Tangles ; Parkinsonian Disorders ; Peptides ; Plaque, Amyloid ; Supranuclear Palsy, Progressive ; tau Proteins ; Tauopathies

BACKGROUND: Tauopathies are a group of diseases caused by the accumulation of hyperphosphorylated tau protein in the central nervous system. Previous studies have revealed that there is considerable overlap in clinical, pathological, and genetic features among different taupathies. CASE REPORT: We report a patient with non-fluent/agrammatic primary progressive aphasia at the initial assessment. Over time, other symptoms belonging to corticobasal degeneration and progressive supranuclear palsy appeared in this patient. CONCLUSIONS: Clinical overlapping features in these disorders may represent different phenotypes of a single disease process.
Aphasia, Primary Progressive* ; Central Nervous System ; Humans ; Phenotype ; Supranuclear Palsy, Progressive ; tau Proteins ; Tauopathies

Accumulated evidence suggests that sporadic cases of Alzheimer's disease (AD) make up more than 95% of total AD patients, and diabetes has been implicated as a strong risk factor for the development of AD. Diabetes shares pathological features of AD, such as impaired insulin signaling, increased oxidative stress, increased amyloid-beta (Aβ) production, tauopathy and cerebrovascular complication. Due to shared pathologies between the two diseases, anti-diabetic drugs may be a suitable therapeutic option for AD treatment. In this article, we will discuss the well-known pathologies of AD, including Aβ plaques and tau tangles, as well as other mechanisms shared in AD and diabetes including reactive glia and the breakdown of blood brain barrier in order to evaluate the presence of any potential, indirect or direct links of pre-diabetic conditions to AD pathology. In addition, clinical evidence of high incidence of diabetic patients to the development of AD are described together with application of anti-diabetic medications to AD patients.
Alzheimer Disease ; Blood-Brain Barrier ; Encephalitis ; Humans ; Incidence ; Insulin ; Neuroglia ; Oxidative Stress ; Pathology ; Risk Factors ; Tauopathies

Cognitive impairment is a result of dementia of diverse causes, such as cholinergic dysfunction and Alzheimer's disease (AD). Houttuynia cordata Thunb. (Saururaceae) has long been used as a traditional herbal medicine. It has biological activities including protective effects against amyloid beta (Abeta) toxicity, via regulation of calcium homeostasis, in rat hippocampal cells. To extend previous reports, we investigated the effects of water extracts of H. cordata herb (HCW) on tauopathies, also involving calcium influx. We then confirmed the effects of HCW in improving memory impairment and neuronal damage in mice with Abeta-induced neurotoxicity. We also investigated the effects of HCW against scopolamine-induced cholinergic dysfunction in mice. In primary neuronal cells, HCW inhibited the phosphorylation of tau by regulating p25/p35 expression in Abeta-induced neurotoxicity. In mice with Abeta-induced neurotoxicity, HCW improved cognitive impairment, as assessed with behavioral tasks, such as novel object recognition, Y-maze, and passive avoidance tasks. HCW also inhibited the degeneration of neurons in the CA3 region of the hippocampus in Abeta-induced neurotoxicity. Moreover, HCW, which had an IC50 value of 79.7 microg/ml for acetylcholinesterase inhibition, ameliorated scopolamine-induced cognitive impairment significantly in Y-maze and passive avoidance tasks. These results indicate that HCW improved cognitive impairment, due to cholinergic dysfunction, with inhibitory effects against tauopathies and cholinergic antagonists, suggesting that HCW may be an interesting candidate to investigate for the treatment of AD.
Acetylcholinesterase ; Alzheimer Disease ; Amyloid ; Animals ; Calcium ; Cholinergic Antagonists ; Dementia ; Herbal Medicine ; Hippocampus ; Homeostasis ; Houttuynia* ; Inhibitory Concentration 50 ; Memory ; Mice ; Neurons ; Phosphorylation ; Rats ; Tauopathies ; Water

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder that is associated with repetitive head injury and has distinctive neuropathological features that differentiate this disease from other neurodegenerative diseases. Intraneuronal tau aggregates, although they occur in different patterns, are diagnostic neuropathological features of CTE, but the precise mechanism of tauopathy is not known in CTE. We performed whole RNA sequencing analysis of post-mortem brain tissue from patients with CTE and compared the results to normal controls to determine the transcriptome signature changes associated with CTE. The results showed that the genes related to the MAP kinase and calcium-signaling pathways were significantly downregulated in CTE. The altered expression of protein phosphatases (PPs) in these networks further suggested that the tauopathy observed in CTE involves common pathological mechanisms similar to Alzheimer's disease (AD). Using cell lines and animal models, we also showed that reduced PPP3CA/PP2B phosphatase activity is directly associated with increases in phosphorylated (p)-tau proteins. These findings provide important insights into PP-dependent neurodegeneration and may lead to novel therapeutic approaches to reduce the tauopathy associated with CTE.
Alzheimer Disease ; Brain ; Brain Injury, Chronic* ; Cell Line ; Craniocerebral Trauma ; Gene Expression Profiling* ; Humans ; Models, Animal ; Neurodegenerative Diseases ; Phosphoprotein Phosphatases ; Phosphotransferases ; Sequence Analysis, RNA ; Tauopathies* ; Transcriptome*

BACKGROUND AND PURPOSE: Behavioral variant frontotemporal dementia (bvFTD) is a subtype of frontotemporal dementia, which has clinical symptoms of progressive personality and behavioral changes with deterioration of social cognition and executive functions. The pathology of bvFTD is known to be tauopathy or TDP-43 equally. We analyzed the 18F-THK5351 positron emission tomography (PET) scans, which were recently developed tau PET, in patients with clinically-diagnosed bvFTD. METHODS: Forty-eight participants, including participants with behavioral variant frontotemporal dementia (bvFTD, n=3), Alzheimer's disease (AD, n=21) and normal cognition (NC, n=24) who completed 3T magnetic resonance images, 18F-THK5351 PET scans, and detailed neuropsychological tests were included in the study. Voxel-wise statistical analysis and region of interest (ROI)-based analyses were performed to evaluate the retention of THK in bvFTD patients. RESULTS: In the voxel-based and ROI-based analyses, patients with bvFTD showed greater THK retention in the prefrontal, medial frontal, orbitofrontal, anterior cingulate, insula, anterior inferior temporal and striatum regions compared to NC participants. Left-right asymmetry was noted in the bvFTD patients. A patient with extrapyramidal symptoms showed much greater THK retention in the brainstem. CONCLUSIONS: The distribution of THK retention in the bvFTD patients was mainly in the frontal, insula, anterior temporal, and striatum regions which are known to be the brain regions corresponding to the clinical symptoms of bvFTD. Our study suggests that 18F-THK5351 PET imaging could be a supportive tool for diagnosis of bvFTD.
Alzheimer Disease ; Brain ; Brain Stem ; Cognition ; Diagnosis ; Executive Function ; Frontotemporal Dementia* ; Gyrus Cinguli ; Humans ; Neuropsychological Tests ; Pathology ; Positron-Emission Tomography ; Tauopathies

Primary age-related tauopathy (PART) is characterized by the presence of tau neurofibrillary tangles (NFTs) which are typically observed in Alzheimer's disease (AD) brains, with few or without β-amyloid (Aβ) plaques. The diagnosis of PART can be categorized into "definite" or "possible" depending on the amount of Aβ plaques. Definite PART is diagnosed when NFTs are observed and the Braak stage is ≤IV, with Thal Aβ Phase 0 (Crary et al., 2014). According to the neuropathological diagnostic criteria, we reported that PART was frequently observed in the Chinese population according to our findings from specimens in our brain bank, with 47% of brain bank subjects meeting the criteria for PART. There is no consensus on the nature of PART. It remains to be elucidated whether PART is an early form of AD or a novel tauopathy (Duyckaerts et al., 2015; Jellinger et al., 2015).
Aged ; Aged, 80 and over ; Aging/pathology* ; Alzheimer Disease/pathology* ; Brain/pathology* ; Cohort Studies ; Female ; Humans ; Male ; Middle Aged ; Neurofibrillary Tangles/pathology* ; Tauopathies/pathology*

Sixty years ago, Steele, Richardson and Olszewski designated progressive supranuclear palsy (PSP) as a new clinicopathological entity in their seminal paper. Since then, in addition to the classic Richardson's syndrome (RS), different clinical phenotypic presentations have been linked with this four-repeat tauopathy. The clinical heterogeneity is associated with variability of regional distribution and severity of abnormal tau accumulation and neuronal loss. In PSP subtypes, the presence of certain clinical pointers may be useful for antemortem prediction of the underlying PSP-tau pathology. Midbrain atrophy on conventional MRI correlates with the clinical phenotype of RS but is not predictive of PSP pathology. Cerebrospinal fluid biomarkers and tau ligand positron emission tomography are promising biomarkers of PSP. A multidisciplinary approach to meet the patients' complex needs is the current core treatment strategy for this devastating disorder.
Atrophy ; Biomarkers ; Cerebrospinal Fluid ; Magnetic Resonance Imaging ; Mesencephalon ; Neurons ; Pathology ; Phenotype ; Population Characteristics ; Positron-Emission Tomography ; Steel ; Supranuclear Palsy, Progressive* ; Tauopathies

Criticisms about amyloid cascade hypothesis of Alzheimer's disease(AD) are based on the findings, first, that the degree of dementia does not correlate with the number of plaques, and second, that the neurofibrillary tangle formation seems to predate plaque formation. In addition, neurofibrillary tangle counts correlate well with the degree of cognitive impairment. These findings suggest the independent importance of tau abnormality in AD research which is involved in the neurofibrillary tangle formation. Recently, tau pathology without amyloid deposits and mutations in tau protein gene were reported to be the major pathogenic mechanism in Pick's disease, progressive supranuclear palsy, corticobasal degeneration and FTDP-17(frontotemporal dementia and parkinsonism linked with chromosome 17). These data suggest that understanding the causes and consequences of tau dysfunction might give new clinical and therapeutic solutions to many known tauopathies.
Amyloid ; Dementia ; Frontotemporal Dementia ; Frontotemporal Lobar Degeneration ; Molecular Biology* ; Neurofibrillary Tangles ; Parkinsonian Disorders ; Pathology ; Pick Disease of the Brain ; Plaque, Amyloid ; Prednisolone ; Supranuclear Palsy, Progressive ; tau Proteins* ; Tauopathies