Current Alzheimer Research - Volume 20, Issue 5, 2023

Chronic exposure to stress throughout the lifespan has been the focus of many studies on Alzheimer's disease (AD) because of the similarities between the biological mechanisms involved in chronic stress and the pathophysiology of AD. In fact, the earliest abnormality associated with the disease is the presence of phosphorylated tau protein in locus coeruleus neurons, a brain structure highly responsive to stress and perceived threat. Here, we introduce allostatic load as a useful concept for understanding many of the complex, interacting neuropathological changes involved in the AD degenerative process. In response to chronic stress, aberrant tau proteins that begin to accumulate within the locus coeruleus decades prior to symptom onset appear to represent a primary pathological event in the AD cascade, triggering a wide range of interacting brain changes involving neuronal excitotoxicity, endocrine alterations, inflammation, oxidative stress, and amyloid plaque exacerbation. While it is acknowledged that stress will not necessarily be the major precipitating factor in all cases, early tau-induced changes within the locus coeruleus-norepinephrine pathway suggests that a therapeutic window might exist for preventative measures aimed at managing stress and restoring balance within the HPA axis.

Thioredoxin1 (Trx1) is a ubiquitous antioxidant protein that regulates the cell's redox status. Trx1's thiol redox activity protects neurons from various physiological processes that cause neuronal damage and neurodegeneration, including oxidative stress, apoptosis, and inflammation. Several studies have found that direct or indirect Trx1 regulation has neuroprotective effects in the brain, protecting against, preventing, or delaying neurodegenerative processes or brain traumas. This review focuses on the term neuroprotection, Trx1 localization, and expression in the brain, as well as its modulation concerning its neuroprotective effect in both animal and clinical models of ischemia, hypoxia, hemorrhage, traumatic brain injury, epilepsy, Alzheimer's disease, and Parkinson's disease.

Background: Alzheimer's disease (AD) and behavioral variant frontotemporal dementia (bvFTD) are important causes of dementia with challenging differential diagnoses in many cases. Addenbrooke’s Cognitive Examination-Revised (ACE-R) is a cognitive battery that may be useful to differentiate the two disorders. Objective: The objectibe of this study is to investigate the value of the ACE-R combined with sociodemographic factors in the differential diagnosis between AD and bvFTD. Methods: The ACE-R was administered to 102 patients with mild dementia due to probable AD, 37 with mild bvFTD, and 135 controls. Performances of patients and controls were analyzed by logistic regression and by ROC curves to refine the diagnostic accuracy of the ACE-R in AD and bvFTD. Results: The ACE-R subscores Attention and Orientation, Fluency, and Memory, in combination with schooling differentiated AD from controls with an area under the ROC curve (AUC) of 0.936 (86% sensitivity and 87% specificity). The ACE-R subscores Attention and Orientation, Fluency, and Language, in combination with sex (male), age, and schooling, discriminated bvFTD from controls with an AUC of 0.908 (81% sensitivity and 95% specificity). In the differentiation between AD and bvFTD, the ACE-R subscores Attention and Orientation, Fluency, and Language, together with age, displayed an AUC of 0.865 (78% sensitivity and 85% specificity). Conclusion: The combination of ACE-R scores with sociodemographic data allowed good differentiation between AD and bvFTD in the study sample.

Background: Alzheimer's disease (AD) is a well-known neurodegenerative disease that gradually induces neural network dysfunction and progressive memory deficits. Neural network activity is represented by rhythmic oscillations that influence local field potentials (LFPs). However, changes in hippocampal neural rhythmic oscillations in the early stage of AD remain largely unexplored. Objective: This study investigated neural rhythmic oscillations in 3-month-old APP/PS1 and 5x- FAD mice to assess early neural connectivity in AD. Methods: LFPs were recorded from the hippocampal CA1 region with implanted microelectrode arrays while the mice were in the awake resting stage. Welch fast Fourier transforms, continuous wavelet transforms, and phase-amplitude coupling analyses were used to compute the power density of different frequency bands and phase-amplitude modulation indices in the LFPs. Results: Our results showed impaired theta, low gamma, and high gamma frequency band power in APP/PS1 and 5xFAD mice during the awake resting stage. AD mice also showed decreased delta, alpha, and beta frequency band power. Impaired theta-low gamma and theta-high gamma phaseamplitude coupling were observed in 5xFAD mice. Conclusion: This study revealed neural network activity differences in oscillation power and cross-frequency coupling in the early stage of AD, providing a new perspective for developing biomarkers for early AD diagnosis.

Introduction: Sensory impairments (SIs, including visual, hearing, olfactory, and taste impairments) have been individually associated with age-related cognitive function. Little is known regarding their combined associations with cognitive function. Methods: We included 2,931 participants (mean age of 69.1 years) from the National Health and Nutrition Examination Survey (NHANES, 2011-2014) and 10,785 participants (mean age of 70.2 years) from the National Health Interview Survey (NHIS, 2021). Status of visual, hearing, olfactory, and taste functions were self-reported in structured questionnaires. In NHANES, cognitive function was objectively measured by a battery of tests, including memory, verbal fluency, and processing speed. NHIS participants answered a single question about subjective cognitive complaints (SCC). We used regression models to assess the relation of the total number and the individual sensory impairments to z-scores of cognitive domains (linear regression) in NHANES and to SCC (logistic regression) in NHIS. Results: A larger number of SI was related to poorer domain-specific cognitive function (all Ptrend <0.05), including memory (beta each additional SI = -0.12, 95% confidence interval: -0.17 to -0.08), verbal fluency (-0.05, -0.10 to -0.01), and processing speed (-0.13, -0.16 to -0.09). In NHIS, each additional SI was related to 96% higher odds of SCC. We also observed independent associations of sensory impairments (except olfactory impairment) with specific cognitive domains. In addition, each individual SI was associated with higher odds of SCC (the odds ratios ranged from 1.30 to 1.78). Conclusion: A larger number of SI was related to worse cognitive function and higher odds of SCC.

Background: Frontal, temporal lobe dementia (FTD) and amyotrophic lateral sclerosis (ALS) are fatal neurodegenerative diseases. Studies have found that CCNF mutations have been found in patients with familial and sporadic ALS and FTD. Behavioural variant frontotemporal dementia (bvFTD) is a clinical syndrome characterized by progressive deterioration of personality, social behaviour, and cognitive function, which is most closely related to genetic factors. As the early symptoms of bvFTD are highly heterogeneous, the condition is often misdiagnosed as Alzheimer's disease or psychiatric disorders. In this study, a bvFTD patient had a CCNF gene mutation, which led to ubiquitinated protein accumulation and ultimately caused neurodegenerative disease. Genetic detection should be improved urgently for bvFTD patients and family members to provide a clinical reference for early diagnosis of frontotemporal dementia. Case Presentation: In this case, the patient was 65 years old with an insidious onset, early-onset memory loss, a significant decline in the episodic memory, an early AD diagnosis, and oral treatment with donepezil hydrochloride for 3 years with poor efficacy, followed by a change to oral memantine hydrochloride tablets, which controlled the condition for several months. His medication was switched to sodium oligomannate capsules, and his condition was gradually controlled, but no significant improvement was observed. After spontaneous drug withdrawal, the patient’s condition progressed rapidly; therefore, he visited our hospital and underwent neuropsychological tests for moderate to severe cognitive impairment. AD cerebrospinal fluid markers showed no significant abnormalities, and cranial MRI revealed frontotemporal lobe atrophy and decreased hippocampal volume. Genetic testing for the presence of the CCNF gene revealed a c.1532C > A (p. T511N) heterozygous variant, which might be a diagnostic criterion for bvFTD. Therefore, the patient's symptoms recurred after transient improvement with the combination of donepezil, oral memantine hydrochloride tablets, and sodium oligomannate, but his overall condition was improved compared to that before, and this treatment regimen was continued to observe changes during the follow-up. Conclusion: The early clinical manifestations of bvFTD are complex and variable, and the condition is easily misdiagnosed, thus delaying treatment. Therefore, for patients with a high clinical suspicion of FTD, in addition to a detailed understanding of their medical history and family history and improvement of relevant examinations, genetic testing should be performed as early as possible to help confirm the diagnosis. For diseases closely related to genes, genetic testing of other family members should be optimised as much as possible to allow early diagnosis and intervention and guide fertility in the next generation.