Chronic stress and Alzheimer's disease

Dapagliflozin mitigates cognitive deficits in a rat model of chronic restrained stress by addressing insulin resistance and mitochondrial dysfunction

Chronic stress is recognized as a risk factor for neurodegeneration. Sodium glucose co-transporter 2 receptors (SGLT2) have been found in various brain regions, suggesting the potential neuroprotective properties of SGLT2 inhibitors as dapagliflozin (DGF). This study aimed to investigate the effect of DGF on behavioral, and neurodegenerative changes in chronic restraint stress (CRS) as an animal model of cognitive impairment. Forty-eight male rats were allocated into four groups: Control; CRS-subjected group, rats were subjected to chronic restraint stress for 6 weeks to induce cognitive impairment; DGF-treated CRS group, dapagliflozin was given daily by oral gavage; and DGF-administered group. Behavioral tests were performed and fasting serum glucose, insulin, and corticosterone levels were measured. Hippocampal oxidative markers, insulin signaling, mitochondrial function, amyloid beta, p-tau, and brain-derived neurotrophic factor (BDNF) gene expression were evaluated. DGF significantly prevented CRS-induced cognitive dysfunction (Y maze and Morris water maze tests). Also, DGF ameliorated hippocampal neurodegenerative changes by decreasing tau and amyloid beta levels, while increasing BDNF gene expression. DGF reduced hippocampal phosphorylated mammalian target of rapamycin (p-mTOR) and protein kinase B (p-Akt) levels. In addition to its antioxidant effects, DGF increased ATP levels and cytochrome C oxidase activity. These findings were confirmed by transmission electron microscopic (TEM) examination. The current study demonstrates a biological link between chronic stress, insulin resistance, and cognitive impairment. Dapagliflozin has therapeutic potential in alleviating cognitive deficits and neurodegeneration primarily due to its insulin-sensitizing and antioxidant properties, along with its capacity to enhance mitochondrial function.

Barley polysaccharides modulate metabolic and mild cognitive impairment in naturally aging mice through the liver-gut-brain axis

Cognitive impairment associated with natural aging significantly reduces the healthy lifespan of elderly adults. Barley is rich in polysaccharides, particularly starch and dietary fibers such as β-glucan and xylan. As the predominant components of barley water extracts, these polysaccharides, especially dietary fibers, exhibit substantial potential in promoting gut and brain health. In this study, we established a natural aging model by exposing mice to a high-fat diet and chronic stress for 220 consecutive days. Our findings revealed that barley polysaccharides ameliorated cognitive deficits, particularly long-term memory, by modulating neurotransmitter levels and reducing corticosterone. Barley polysaccharides also alleviated lipid metabolism disorders, reduced liver lesions, and decreased body weight as well as the percentage of visceral fat in mice by regulating bile acid and l-lysine metabolism. Additionally, barley polysaccharides enhanced intestinal barrier integrity and reshaped the gut microbiota. They significantly increased the abundance of norank_f_Muribaculaceae and unclassified f_Lachnospiraceae, leading to elevated short-chain fatty acid levels, especially butyric acid, which contributed to improved cognitive function. These findings suggest that barley polysaccharides could serve as a promising dietary intervention to mitigate cognitive decline associated with natural aging through the liver-gut-brain axis.

Alzheimer's disease: a comprehensive review of epidemiology, risk factors, symptoms diagnosis, management, caregiving, advanced treatments and associated challenges

Background

Alzheimer's disease (AD) is a chronic, progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and impaired reasoning. It is the leading cause of dementia in older adults, marked by the pathological accumulation of amyloid-beta plaques and neurofibrillary tangles. These pathological changes lead to widespread neuronal damage, significantly impacting daily functioning and quality of life.

Objective

This comprehensive review aims to explore various aspects of Alzheimer's disease, including its epidemiology, risk factors, clinical presentation, diagnostic advancements, management strategies, caregiving challenges, and emerging therapeutic interventions.

Methods

A systematic literature review was conducted across multiple electronic databases, including PubMed, MEDLINE, Cochrane Library, and Scopus, from their inception to May 2024. The search strategy incorporated a combination of keywords and Medical Subject Headings (MeSH) terms such as "Alzheimer's disease," "epidemiology," "risk factors," "symptoms," "diagnosis," "management," "caregiving," "treatment," and "novel therapies." Boolean operators (AND, OR) were used to refine the search, ensuring a comprehensive analysis of the existing literature on Alzheimer's disease.

Results

AD is significantly influenced by genetic predispositions, such as the apolipoprotein E (APOE) ε4 allele, along with modifiable environmental factors like diet, physical activity, and cognitive engagement. Diagnostic approaches have evolved with advances in neuroimaging techniques (MRI, PET), and biomarker analysis, allowing for earlier detection and intervention. The National Institute on Aging and the Alzheimer's Association have updated diagnostic criteria to include biomarker data, enhancing early diagnosis.

Conclusion

The management of AD includes pharmacological treatments, such as cholinesterase inhibitors and NMDA receptor antagonists, which provide symptomatic relief but do not slow disease progression. Emerging therapies, including amyloid-beta and tau-targeting treatments, gene therapy, and immunotherapy, offer potential for disease modification. The critical role of caregivers is underscored, as they face considerable emotional, physical, and financial burdens. Support programs, communication strategies, and educational interventions are essential for improving caregiving outcomes. While significant advancements have been made in understanding and managing AD, ongoing research is necessary to identify new therapeutic targets and enhance diagnostic and treatment strategies. A holistic approach, integrating clinical, genetic, and environmental factors, is essential for addressing the multifaceted challenges of Alzheimer's disease and improving outcomes for both patients and caregivers.

Anxiety and Alzheimer's disease pathogenesis: focus on 5-HT and CRF systems in 3xTg-AD and TgF344-AD animal models

Dementia remains one of the leading causes of morbidity and mortality in older adults. Alzheimer's disease (AD) is the most common type of dementia, affecting over 55 million people worldwide. AD is characterized by distinct neurobiological changes, including amyloid-beta protein deposits and tau neurofibrillary tangles, which cause cognitive decline and subsequent behavioral changes, such as distress, insomnia, depression, and anxiety. Recent literature suggests a strong connection between stress systems and AD progression. This presents a promising direction for future AD research. In this review, two systems involved in regulating stress and AD pathogenesis will be highlighted: serotonin (5-HT) and corticotropin releasing factor (CRF). Throughout the review, we summarize critical findings in the field while discussing common limitations with two animal models (3xTg-AD and TgF344-AD), novel pharmacotherapies, and potential early-intervention treatment options. We conclude by highlighting promising future pharmacotherapies and translational animal models of AD and anxiety.

Life Experience Matters: Enrichment and Stress Can Influence the Likelihood of Developing Alzheimer's Disease via Gut Microbiome

Alzheimer's disease (AD) is a chronic neurodegenerative disease, characterized by the presence of β-amyloid (Aβ) plaques and neurofibrillary tangles (NFTs) formed from abnormally phosphorylated tau proteins (ptau). To date, there is no cure for AD. Earlier therapeutic efforts have focused on the clinical stages of AD. Despite paramount efforts and costs, pharmaceutical interventions including antibody therapies targeting Aβ have largely failed. This highlights the need to alternate treatment strategies and a shift of focus to early pre-clinical stages. Approximately 25-40% of AD cases can be attributed to environmental factors including chronic stress. Gut dysbiosis has been associated with stress and the pathogenesis of AD and can increase both Aβ and NFTs in animal models of the disease. Both stress and enrichment have been shown to alter AD progression and gut health. Targeting stress-induced gut dysbiosis through probiotic supplementation could provide a promising intervention to delay disease progression. In this review, we discuss the effects of stress, enrichment, and gut dysbiosis in AD models and the promising evidence from probiotic intervention studies.

Neuroticism and Stress in Older Adults: The Buffering Role of Self-Esteem

BACKGROUND

Chronic stress is associated with accelerated aging and poor health outcomes in older adults. According to the Transactional Model of Stress (TMS), distress is experienced when one perceives the stressor, or threat, to outweigh the ability to cope. The experience of distress is correlated with trait neuroticism, which is associated with greater perceptions of stress and stress reactivity, as well as a tendency to engage in maladaptive coping strategies. However, as individual personality traits do not act in isolation, this study aimed to investigate the moderating role of self-esteem in the relationship between neuroticism and distress using a TMS framework.

METHODS

A total of 201 healthy older adults (Mage = 68.65 years) completed questionnaires measuring self-esteem, neuroticism, perceived stress, and positive coping.

RESULTS

Greater neuroticism was significantly associated with less positive coping at low (b = -0.02, p < 0.001) and mean self-esteem levels (b = -0.01, p < 0.001), but not at high self-esteem levels (b = -0.01, p = 0.06). No moderating effect was found for perceived stress or overall distress.

CONCLUSION

The results support the association between trait neuroticism and indices of stress and suggest a potential buffering effect of self-esteem in moderating the negative association between neuroticism and positive coping.

Extracellular vesicles and Alzheimer's disease in the novel era of Precision Medicine: implications for disease progression, diagnosis and treatment

Extracellular vesicles (EVs), secreted membranous nano-sized particles, are critical intercellular messengers participating in nervous system homeostasis, while recent evidence implicates EVs in Alzheimer's disease (AD) pathogenesis. Specifically, small EVs have been shown to spread toxic proteins, induce neuronal loss, and contribute to neuroinflammation and AD progression. On the other hand, EVs can reduce amyloid-beta deposition and transfer neuroprotective substances between cells, mitigating disease mechanisms. In addition to their roles in AD pathogenesis, EVs also exhibit great potential for the diagnosis and treatment of other brain disorders, representing an advantageous tool for Precision Medicine. Herein, we summarize the contribution of small EVs to AD-related mechanisms and disease progression, as well as their potential as diagnostic and therapeutic agents for AD.

Mindfulness-Based Student Training Improves Vascular Variability Associated With Sustained Reductions in Physiological Stress Response

In today's fast-paced society, chronic stress has become an increasing problem, as it can lead to psycho-physiological health problems. University students are also faced with stress due to the demands of many courses and exams. The positive effects of mindfulness-based stress reduction (MBSR) on stress management and self-regulation have already been studied. We have developed a new mindfulness intervention tailored for students—the Mindfulness-Based Student Training (MBST). In this study, we present longitudinal results of the MBST evaluation. Biosignal analysis methods, including pulse wave variability (PWV), heart rate variability, and respiratory activity, were used to assess participants' state of autonomic regulation during the 12-week intervention and at follow-up. The progress of the intervention group (IGR, N = 31) up to 3 months after the end of MBST was compared with that of a control group (CON, N = 34). In addition, the long-term effect for IGR up to 1 year after intervention was examined. The analysis showed significant positive changes in PWV exclusively for IGR. This positive effect, particularly on vascular function, persists 1 year after the end of MBST. These results suggest a physiologically reduced stress level in MBST participants and a beneficial preventive health care program for University students.