Degenerative dementias: Alterations of emotions and mood disorders

A tau fragment links depressive-like behaviors and cognitive declines in Alzheimer's disease mouse models through attenuating mitochondrial function

Introduction

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease characterized by extracellular senile plaques including amyloid-β peptides and intracellular neurofibrillary tangles consisting of abnormal Tau. Depression is one of the most common neuropsychiatric symptoms in AD, and clinical evidence demonstrates that depressive symptoms accelerate the cognitive deficit of AD patients. However, the underlying molecular mechanisms of depressive symptoms present in the process of AD remain unclear.

Methods

Depressive-like behaviors and cognitive decline in hTau mice were induced by chronic restraint stress (CRS). Computational prediction and molecular experiments supported that an asparagine endopeptidase (AEP)-derived Tau fragment, Tau N368 interacts with peroxisome proliferator-activated receptor delta (PPAR-δ). Further behavioral studies investigated the role of Tau N368-PPAR-δ interaction in depressive-like behaviors and cognitive declines of AD models exposed to CRS.

Results

We found that mitochondrial dysfunction was positively associated with depressive-like behaviors and cognitive deficits in hTau mice. Chronic stress increased Tau N368 and promoted the interaction of Tau N368 with PPAR-δ, repressing PPAR-δ-mediated transactivation in the hippocampus of mice. Then we predicted and identified the binding sites of PPAR-δ. Finally, inhibition of AEP, clearance of Tau N368 and pharmacological activation of PPAR-δ effectively alleviated CRS-induced depressive-like behaviors and cognitive decline in mice.

Conclusion

These results demonstrate that Tau N368 in the hippocampus impairs mitochondrial function by suppressing PPAR-δ, facilitating the occurrence of depressive-like behaviors and cognitive decline. Therefore, our findings may provide new mechanistic insight in the pathophysiology of depression-like phenotype in mouse models of Alzheimer's disease.

Using digital assessment technology to detect neuropsychological problems in primary care settings

Introduction

Screening for neurocognitive impairment and psychological distress in ambulatory primary and specialty care medical settings is an increasing necessity. The Core Cognitive Evaluation™ (CCE) is administered/scored using an iPad, requires approximately 8 min, assesses 3- word free recall and clock drawing to command and copy, asks questions about lifestyle and health, and queries for psychological distress. This information is linked with patients' self- reported concerns about memory and their cardiovascular risks.

Methods

A total of 199 ambulatory patients were screened with the CCE as part of their routine medical care. The CCE provides several summary indices, and scores on 44 individual digital clock variables across command and copy tests conditions.

Results

Subjective memory concerns were endorsed by 41% of participants. Approximately 31% of participants reported psychological distress involving loneliness, anxiety, or depression. Patients with self-reported memory concerns scored lower on a combined delay 3- word/ clock drawing index (p < 0.016), the total summary clock drawing command/ copy score (p < 0.050), and clock drawing to command Drawing Efficiency (p < 0.036) and Simple and Complex Motor (p < 0.029) indices. Patients treated for diabetes and atherosclerotic cardiovascular disease (ASCVD) scored lower on selected CCE outcome measures (p < 0.035). Factor analyses suggest that approximately 10 underlying variables can explain digital clock drawing performance.

Discussion

The CCE is a powerful neurocognitive assessment tool that is sensitive to patient's subjective concerns about possible decline in memory, mood symptoms, possible cognitive impairment, and cardiovascular risk. iPad administration ensures total reliability for test administration and scoring. The CCE is easily deployable in outpatient ambulatory primary care settings.

Depressive-like Behaviors Induced by mGluR5 Reduction in 6xTg in Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is one representative dementia characterized by the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain, resulting in cognitive decline and memory loss. AD is associated with neuropsychiatric symptoms, including major depressive disorder (MDD). Recent studies showed a reduction in mGluR5 expression in the brains of stress-induced mice models and individuals with MDD compared to controls. In our study, we identified depressive-like behavior and memory impairment in a mouse model of AD, specifically in the 6xTg model with tau and Aβ pathologies. In addition, we investigated the expression of mGluR5 in the brains of 6xTg mice using micro-positron emission tomography (micro-PET) imaging, histological analysis, and Western blot analysis, and we observed a decrease in mGluR5 levels in the brains of 6xTg mice compared to wild-type (WT) mice. Additionally, we identified alterations in the ERK/AKT/GSK-3β signaling pathway in the brains of 6xTg mice. Notably, we identified a significant negative correlation between depressive-like behavior and the protein level of mGluR5 in 6xTg mice. Additionally, we also found a significant positive correlation between depressive-like behavior and AD pathologies, including phosphorylated tau and Aβ. These findings suggested that abnormal mGluR5 expression and AD-related pathologies were involved in depressive-like behavior in the 6xTg mouse model. Further research is warranted to elucidate the underlying mechanisms and explore potential therapeutic targets in the intersection of AD and depressive-like symptoms.

The heterogeneity of late-life depression and its pathobiology: a brain network dysfunction disorder

Depression is frequent in older individuals and is often associated with cognitive impairment and increasing risk of subsequent dementia. Late-life depression (LLD) has a negative impact on quality of life, yet the underlying pathobiology is still poorly understood. It is characterized by considerable heterogeneity in clinical manifestation, genetics, brain morphology, and function. Although its diagnosis is based on standard criteria, due to overlap with other age-related pathologies, the relationship between depression and dementia and the relevant structural and functional cerebral lesions are still controversial. LLD has been related to a variety of pathogenic mechanisms associated with the underlying age-related neurodegenerative and cerebrovascular processes. In addition to biochemical abnormalities, involving serotonergic and GABAergic systems, widespread disturbances of cortico-limbic, cortico-subcortical, and other essential brain networks, with disruption in the topological organization of mood- and cognition-related or other global connections are involved. Most recent lesion mapping has identified an altered network architecture with "depressive circuits" and "resilience tracts", thus confirming that depression is a brain network dysfunction disorder. Further pathogenic mechanisms including neuroinflammation, neuroimmune dysregulation, oxidative stress, neurotrophic and other pathogenic factors, such as β-amyloid (and tau) deposition are in discussion. Antidepressant therapies induce various changes in brain structure and function. Better insights into the complex pathobiology of LLD and new biomarkers will allow earlier and better diagnosis of this frequent and disabling psychopathological disorder, and further elucidation of its complex pathobiological basis is warranted in order to provide better prevention and treatment of depression in older individuals.

Rationale for a Multi-Factorial Approach for the Reversal of Cognitive Decline in Alzheimer's Disease and MCI: A Review

Alzheimer's disease (AD) is a multifactorial, progressive, neurodegenerative disease typically characterized by memory loss, personality changes, and a decline in overall cognitive function. Usually manifesting in individuals over the age of 60, this is the most prevalent type of dementia and remains the fifth leading cause of death among Americans aged 65 and older. While the development of effective treatment and prevention for AD is a major healthcare goal, unfortunately, therapeutic approaches to date have yet to find a treatment plan that produces long-term cognitive improvement. Drugs that may be able to slow down the progression rate of AD are being introduced to the market; however, there has been no previous solution for preventing or reversing the disease-associated cognitive decline. Recent studies have identified several factors that contribute to the progression and severity of the disease: diet, lifestyle, stress, sleep, nutrient deficiencies, mental health, socialization, and toxins. Thus, increasing evidence supports dietary and other lifestyle changes as potentially effective ways to prevent, slow, or reverse AD progression. Studies also have demonstrated that a personalized, multi-therapeutic approach is needed to improve metabolic abnormalities and AD-associated cognitive decline. These studies suggest the effects of abnormalities, such as insulin resistance, chronic inflammation, hypovitaminosis D, hormonal deficiencies, and hyperhomocysteinemia, in the AD process. Therefore a personalized, multi-therapeutic program based on an individual's genetics and biochemistry may be preferable over a single-drug/mono-therapeutic approach. This article reviews these multi-therapeutic strategies that identify and attenuate all the risk factors specific to each affected individual. This article systematically reviews studies that have incorporated multiple strategies that target numerous factors simultaneously to reverse or treat cognitive decline. We included high-quality clinical trials and observational studies that focused on the cognitive effects of programs comprising lifestyle, physical, and mental activity, as well as nutritional aspects. Articles from PubMed Central, Scopus, and Google Scholar databases were collected, and abstracts were reviewed for relevance to the subject matter. Epidemiological, pathological, toxicological, genetic, and biochemical studies have all concluded that AD represents a complex network insufficiency. The research studies explored in this manuscript confirm the need for a multifactorial approach to target the various risk factors of AD. A single-drug approach may delay the progression of memory loss but, to date, has not prevented or reversed it. Diet, physical activity, sleep, stress, and environment all contribute to the progression of the disease, and, therefore, a multi-factorial optimization of network support and function offers a rational therapeutic strategy. Thus, a multi-therapeutic program that simultaneously targets multiple factors underlying the AD network may be more effective than a mono-therapeutic approach.

G protein-biased GPR3 signaling ameliorates amyloid pathology in a preclinical Alzheimer's disease mouse model

Biased G protein-coupled receptor (GPCR) ligands, which preferentially activate G protein or β-arrestin signaling pathways, are leading to the development of drugs with superior efficacy and reduced side effects in heart disease, pain management, and neuropsychiatric disorders. Although GPCRs are implicated in the pathophysiology of Alzheimer's disease (AD), biased GPCR signaling is a largely unexplored area of investigation in AD. Our previous work demonstrated that GPR3-mediated β-arrestin signaling modulates amyloid-β (Aβ) generation in vitro and that Gpr3 deficiency ameliorates Aβ pathology in vivo. However, Gpr3-deficient mice display several adverse phenotypes, including elevated anxiety-like behavior, reduced fertility, and memory impairment, which are potentially associated with impaired G protein signaling. Here, we generated a G protein-biased GPR3 mouse model to investigate the physiological and pathophysiological consequences of selective elimination of GPR3-mediated β-arrestin signaling in vivo. In contrast to Gpr3-deficient mice, G protein-biased GPR3 mice do not display elevated anxiety levels, reduced fertility, or cognitive impairment. We further determined that G protein-biased signaling reduces soluble Aβ levels and leads to a decrease in the area and compaction of amyloid plaques in the preclinical AppNL-G-F AD mouse model. The changes in amyloid pathology are accompanied by robust microglial and astrocytic hypertrophy, which suggest a protective glial response that may limit amyloid plaque development in G protein-biased GPR3 AD mice. Collectively, these studies indicate that GPR3-mediated G protein and β-arrestin signaling produce discrete and separable effects and provide proof of concept for the development of safer GPCR-targeting therapeutics with more directed pharmacological action for AD.

Ameliorative Processes of Beta-Carotene in Streptozotocin-Induced Diabetic Vascular Dementia in Rats

Beta-carotene (BC) is a precursor of vitamin A and an excellent antioxidant. It protects the vascular system. Vascular dementia (VaD) is one of the aging disorders causing memory dysfunction. The available medicines for the management of VaD are limited. The present study aimed to evaluate the ameliorative effect of BC in streptozotocin (STZ)-induced diabetic VaD in rats. Diabetic VaD was induced through the administration of nicotinamide (NA, 50 mg/kg; i.p.) and STZ (50 mg/kg; i.p.). The test compound BC (50 and 100 mg/kg; p.o.) and reference compound donepezil (1 mg/kg; p.o.) were administered for 15 consecutive days. Cognitive changes were assessed by transfer latency (TL) using the elevated plus maze (EPM) test. The changes in acetylcholinesterase (AChE) activity were estimated in the septohippocampal system of rat brains. The administration of STZ caused significant changes in cognitive functions (increased TL) as compared to the normal group. BC ameliorated the anxiety-related cognitive behavior and neurotransmitter (elevated AChE) changes provoked by diabetic VaD. Therefore, BC could be a potential therapeutic candidate in the management of VaD.

Management of Dementia

PURPOSE OF REVIEW

This article describes an approach to managing patients following a diagnosis of dementia, including medical management, nonpharmacologic strategies, safety interventions, caregiver support, mobilization of community resources, and advanced care planning.

RECENT FINDINGS

Dementia clinical syndromes are frequently caused by mixed pathologies, leading to varied clinical presentations that include memory loss, behavioral changes, communication challenges, safety concerns, and loss of independent function. Medications for treating dementia currently target cognitive and behavioral symptoms, although disease-modifying therapies for Alzheimer disease may be making their way into widespread clinical practice soon. Identification and treatment of co-occurring medical problems, such as obstructive sleep apnea, adverse medication effects, mood disorders, hearing loss, pain, alcohol misuse, and vascular risk factors, may mitigate the impact of these conditions on cognitive decline. Mobilization of clinical and community-based interprofessional teams will ensure that people with dementia and their care partners have the expertise, support, and access to resources they need. Addressing goals of care early in the disease course will allow people with dementia to contribute to their care plan by expressing their wishes.

SUMMARY

Developing a structured approach to treating common causes of dementia and related comorbid medical conditions, identifying a local network of interprofessional clinical and community-based referrals, and providing readily available educational resources will help clinicians provide quality dementia care management that extends beyond the clinic visit. Encouraging patients and families to engage in clinical research will advance the identification of effective therapies, preventive strategies, and quality care models for the future.

‘Dazed and Confused!’ Context and Social Disconnect in the Time of Pandemic

Humans are social animals. Our sense of identity and ‘self’ is defined in part by the roles we perform in the social groups to which we belong. This article discusses some of the variables that contribute to our sense of self, including language, place of origin, education and shared social norms. It also outlines some of the general mechanisms that underpin our various social networks. In its final part, this article reviews the impact of social isolation, such as that happened during the COVID pandemic, on these social mechanisms and the resulted disruption of psychological wellbeing in individuals diagnosed with dementia.