Plasma cortisol and progression of dementia in subjects with Alzheimer-type dementia

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.

The fibroblast growth factor system in cognitive disorders and dementia

Cognitive impairment is the core precursor to dementia and other cognitive disorders. Current hypotheses suggest that they share a common pathological basis, such as inflammation, restricted neurogenesis, neuroendocrine disorders, and the destruction of neurovascular units. Fibroblast growth factors (FGFs) are cell growth factors that play essential roles in various pathophysiological processes via paracrine or autocrine pathways. This system consists of FGFs and their receptors (FGFRs), which may hold tremendous potential to become a new biological marker in the diagnosis of dementia and other cognitive disorders, and serve as a potential target for drug development against dementia and cognitive function impairment. Here, we review the available evidence detailing the relevant pathways mediated by multiple FGFs and FGFRs, and recent studies examining their role in the pathogenesis and treatment of cognitive disorders and dementia.

Neurovascular Dysfunction in Diverse Communities With Health Disparities-Contributions to Dementia and Alzheimer's Disease

Alzheimer's disease and related dementias (ADRD) are an expanding worldwide crisis. In the absence of scientific breakthroughs, the global prevalence of ADRD will continue to increase as more people are living longer. Racial or ethnic minority groups have an increased risk and incidence of ADRD and have often been neglected by the scientific research community. There is mounting evidence that vascular insults in the brain can initiate a series of biological events leading to neurodegeneration, cognitive impairment, and ADRD. We are a group of researchers interested in developing and expanding ADRD research, with an emphasis on vascular contributions to dementia, to serve our local diverse community. Toward this goal, the primary objective of this review was to investigate and better understand health disparities in Alabama and the contributions of the social determinants of health to those disparities, particularly in the context of vascular dysfunction in ADRD. Here, we explain the neurovascular dysfunction associated with Alzheimer's disease (AD) as well as the intrinsic and extrinsic risk factors contributing to dysfunction of the neurovascular unit (NVU). Next, we ascertain ethnoregional health disparities of individuals living in Alabama, as well as relevant vascular risk factors linked to AD. We also discuss current pharmaceutical and non-pharmaceutical treatment options for neurovascular dysfunction, mild cognitive impairment (MCI) and AD, including relevant studies and ongoing clinical trials. Overall, individuals in Alabama are adversely affected by social and structural determinants of health leading to health disparities, driven by rurality, ethnic minority status, and lower socioeconomic status (SES). In general, these communities have limited access to healthcare and healthy food and other amenities resulting in decreased opportunities for early diagnosis of and pharmaceutical treatments for ADRD. Although this review is focused on the current state of health disparities of ADRD patients in Alabama, future studies must include diversity of race, ethnicity, and region to best be able to treat all individuals affected by ADRD.

Better stress coping associated with lower tau in amyloid-positive cognitively unimpaired older adults

OBJECTIVE

Research in animals has shown that chronic stress exacerbates tau pathology. In humans, psychological stress has been associated with higher risk of Alzheimer disease clinical syndrome. The objective of this cross-sectional study was to assess the hypothesis that stress coping ability (assessed via the Brief Resilience Scale [BRS]) is associated with tau burden and to evaluate whether these associations differed by sex and amyloid status (A+/A-) in cognitively unimpaired (CU) older adults.

METHODS

We included 225 CU participants (mean age 70.4 ± 10.2 years, 48% female) enrolled in the population-based Mayo Clinic Study of Aging who completed the BRS and underwent amyloid-PET (Pittsburgh compound B-PET) and tau-PET (AV1451-PET). We fitted multiple regression and analysis of covariance models to assess the associations between BRS and tau-PET and the interaction with amyloid status and sex. We focused on entorhinal cortex (ERC) tau burden and also performed voxel-wise analyses. Age, sex, education, depression, and anxiety were considered as covariates.

RESULTS

Higher stress coping ability was associated with lower tau burden in the medial temporal lobe (including ERC) and occipito-temporal and cuneal/precuneal cortices. The association was present in both A+ and A- but weaker in A- CU older adults. There was an interaction between amyloid status and stress coping ability that was restricted to the medial temporal lobe tau such that A+ CU older adults with lower stress coping abilities showed higher tau. There were no significant interactions between stress coping and sex.

CONCLUSIONS

A faster termination of the stress response (higher coping ability) may limit the negative effects of stress on tau deposition. Conversely, lower stress coping ability may be an early sign of accumulating tau pathology. Longitudinal studies are warranted to clarify whether stress mechanisms act to exacerbate tau pathology or tau influences stress-related brain mechanisms and lowers the ability to cope with stress.

Longitudinal associations between diurnal cortisol variation and later-life cognitive impairment

OBJECTIVE

To determine whether hypothalamus-pituitary-adrenal axis (HPAA) dysfunction is prospectively associated with global cognitive impairment in later life.

METHODS

This cross-cohort study integrates 2 large longitudinal datasets, Whitehall II and the National Survey for Health and Development (NSHD), on data collected in the Whitehall II study between 2002-2004, 2007-2009, and 2012-2013; and for NSHD between 2006-2010 and in 2015. Serial salivary cortisol samples were collected multiple times within a 24-hour period at mean ages 61.2 and 65.9 years in Whitehall II and at age 60-64 years from NSHD participants. Cortisol profile is defined using cortisol awakening response and am:pm ratio. Cognitive function was measured using the Mini-Mental State Examination in Whitehall II and Addenbrooke's Cognitive Examination, third version, in NSHD, harmonized into a 30-point score. Models were adjusted for age, sex, diagnoses of hypertension and diabetes, body mass index (BMI), educational attainment, and interval between HPAA and cognitive assessments.

RESULTS

In fully adjusted models, increased am:pm cortisol ratio was prospectively associated with better later-life cognitive function years later (0.02 fewer errors per SD increase in am:pm cortisol ratio, p < 0.01) and verbal fluency (0.03 SD increase in verbal fluency per SD increase in am:pm ratio, p < 0.01). Increasing age, lower educational attainment, diagnosis of hypertension, diagnosis of diabetes, and increased BMI were associated with worse cognitive function and poorer verbal fluency. There were no associations between depression and later-life cognition or reverse associations between cognition and later-life cortisol profiles.

CONCLUSIONS

Loss of diurnal HPAA variation is evident in individuals subsequently experiencing more cognitive impairment. It may serve as an early preclinical marker of cognitive decline.

Is AD a Stress-Related Disorder? Focus on the HPA Axis and Its Promising Therapeutic Targets

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that has important health and economic impacts in the elderly. Despite a better understanding of the molecular mechanisms leading to the appearance of major pathological hallmarks (senile plaques and neurofibrillary tangles), effective treatments are still lacking. Sporadic AD forms (98% of all cases) are multifactorial, and a panoply of risk factors have been identified. While the major risk factor is aging, growing evidence suggests that chronic stress or stress-related disorders increase the probability to develop AD. An early dysregulation of the hypothalamic-pituitary-adrenal axis (HPA axis or stress axis) has been observed in patients. The direct consequence of such perturbation is an oversecretion of glucocorticoids (GC) associated with an impairment of its receptors (glucocorticoid receptors, GR). These steroids hormones easily penetrate the brain and act in synergy with excitatory amino acids. An overexposure could be highly toxic in limbic structures (prefrontal cortex and hippocampus) and contribute in the cognitive decline occurring in AD. GC and GR dysregulations seem to be involved in lots of functions disturbed in AD and a vicious cycle appears, where AD induces HPA axis dysregulation, which in turn potentiates the pathology. This review article presents some preclinical and clinical studies focusing on the HPA axis hormones and their receptors to fight AD. Due to its primordial role in the maintenance of homeostasis, the HPA axis appears as a key-actor in the etiology of AD and a prime target to tackle AD by offering multiple angles of action.

Safety, Pharmacokinetics, and Pharmacodynamics of ASP3662, a Novel 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitor, in Healthy Young and Elderly Subjects

Inhibition of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) represents a potential mechanism for improving pain conditions. ASP3662 is a potent and selective inhibitor of 11β-HSD1. Two phase I clinical studies were conducted to assess the safety, tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of single and multiple ascending doses of ASP3662 in healthy young and elderly non-Japanese and young Japanese subjects. Nonlinear, more than dose-proportional PKs were observed for ASP3662 after single-dose administration, particularly at lower doses (≤ 6 mg); the PKs at steady state were dose proportional, although the time to ASP3662 steady state was dose dependent at lower doses (≤ 2 mg). Similar PKs were observed among young Japanese, young non-Japanese, and elderly non-Japanese subjects. Specific inhibition of 11β-HSD1 occurred after both single and multiple doses of ASP3662. A marked dissociation between PKs and PDs was observed after single but not multiple doses of ASP3662. ASP3662 was generally safe and well tolerated.

Vulnerability and resilience to Alzheimer's disease: early life conditions modulate neuropathology and determine cognitive reserve

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with a high prevalence among the elderly and a huge personal and societal impact. Recent epidemiological studies have indicated that the incidence and age of onset of sporadic AD can be modified by lifestyle factors such as education, exercise, and (early) stress exposure. Early life adversity is known to promote cognitive decline at a later age and to accelerate aging, which are both primary risk factors for AD. In rodent models, exposure to 'negative' or 'positive' early life experiences was recently found to modulate various measures of AD neuropathology, such as amyloid-beta levels and cognition at later ages. Although there is emerging interest in understanding whether experiences during early postnatal life also modulate AD risk in humans, the mechanisms and possible substrates underlying these long-lasting effects remain elusive.

METHODS

We review literature and discuss the role of early life experiences in determining later age and AD-related processes from a brain and cognitive 'reserve' perspective. We focus on rodent studies and the identification of possible early determinants of later AD vulnerability or resilience in relation to early life adversity/enrichment.

RESULTS

Potential substrates and mediators of early life experiences that may influence the development of AD pathology and cognitive decline are: programming of the hypothalamic-pituitary-adrenal axis, priming of the neuroinflammatory response, dendritic and synaptic complexity and function, overall brain plasticity, and proteins such as early growth response protein 1 (EGR1), activity regulated cytoskeleton-associated protein (Arc), and repressor element-1 silencing transcription factor (REST).

CONCLUSIONS

We conclude from these rodent studies that the early postnatal period is an important and sensitive phase that influences the vulnerability to develop AD pathology. Yet translational studies are required to investigate whether early life experiences also modify AD development in human studies, and whether similar molecular mediators can be identified in the sensitivity to develop AD in humans.

HIV Neuroinfection and Alzheimer's Disease: Similarities and Potential Links?

Environmental factors such as chemicals, stress and pathogens are now widely believed to play important roles in the onset of some brain diseases, as they are associated with neuronal impairment and acute or chronic inflammation. Alzheimer’s disease (AD) is characterized by progressive synaptic dysfunction and neurodegeneration that ultimately lead to dementia. Neuroinflammation also plays a prominent role in AD and possible links to viruses have been proposed. In particular, the human immunodeficiency virus (HIV) can pass the blood-brain barrier and cause neuronal dysfunction leading to cognitive dysfunctions called HIV-associated neurocognitive disorders (HAND). Similarities between HAND and HIV exist as numerous factors involved in AD such as members of the amyloid and Tau pathways, as well as stress-related pathways or blood brain barrier (BBB) regulators, seem to be modulated by HIV brain infection, leading to the accumulation of amyloid plaques or neurofibrillary tangles (NFT) in some patients. Here, we summarize findings regarding how HIV and some of its proteins such as Tat and gp120 modulate signaling and cellular pathways also impaired in AD, suggesting similarities and convergences of these two pathologies.

Midlife Work-Related Stress Increases Dementia Risk in Later Life: The CAIDE 30-Year Study

Objective

To investigate the associations between midlife work-related stress and mild cognitive impairment (MCI), dementia, and Alzheimer's disease later in life, in a large representative population.

Method

Cardiovascular Risk Factors, Aging and Dementia (CAIDE) study participants were randomly selected from independent population-based surveys (mean age 50 years). A random sample of 2,000 individuals was invited for two reexaminations including cognitive tests (at mean age 71 and mean age 78), and 1,511 subjects participated in at least one reexamination (mean follow-up 28.5 years). Work-related stress was measured using two questions on work demands that were administered in midlife. Analyses adjusted for important confounders.

Results

Higher levels of midlife work-related stress were associated with higher risk of MCI (odds ratio [OR], 1.38; 95% confidence interval [CI], 1.08-1.76), dementia (OR, 1.53; CI, 1.13-2.07), and Alzheimer's disease (OR, 1.55; CI, 1.19-2.36) at the first follow-up among the CAIDE participants. Results remained significant after adjusting for several possible confounders. Work-related stress was not associated with MCI and dementia during the extended follow-up.

Discussion

Midlife work-related stress increases the risk for MCI, dementia, and Alzheimer's disease in later life. The association was not seen after the extended follow-up possibly reflecting selective survival/participation, heterogeneity in dementia among the oldest old, and a critical time window for the effects of midlife stress.

Environmental novelty exacerbates stress hormones and Aβ pathology in an Alzheimer's model

Cognitive stimulation has been proposed as a non-pharmacological intervention to be used in primary, secondary and tertiary prevention approaches for Alzheimer's disease. A common familial Alzheimer's disease transgenic model showed heightened levels of the stress hormone, corticosterone. When exposed to periodic enhanced cognitive stimulation, these animals demonstrated further heightened levels of corticosterone as well as increased Aβ pathology. Hence, Alzheimer's disease may be associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction, causing stimulatory environments to become stress-inducing, leading to a glucocorticoid-pathology cycle contributing to further Aβ release and plaque formation. This finding suggests that stimulation-based interventions and local environments for people with Alzheimer's disease need to be designed to minimise a stress response that may exacerbate brain pathology.

Chronic Stress and Glucocorticoids: From Neuronal Plasticity to Neurodegeneration

Stress and stress hormones, glucocorticoids (GCs), exert widespread actions in central nervous system, ranging from the regulation of gene transcription, cellular signaling, modulation of synaptic structure, and transmission and glial function to behavior. Their actions are mediated by glucocorticoid and mineralocorticoid receptors which are nuclear receptors/transcription factors. While GCs primarily act to maintain homeostasis by inducing physiological and behavioral adaptation, prolonged exposure to stress and elevated GC levels may result in neuro- and psychopathology. There is now ample evidence for cause-effect relationships between prolonged stress, elevated GC levels, and cognitive and mood disorders while the evidence for a link between chronic stress/GC and neurodegenerative disorders such as Alzheimer's (AD) and Parkinson's (PD) diseases is growing. This brief review considers some of the cellular mechanisms through which stress and GC may contribute to the pathogenesis of AD and PD.

PET Imaging of Epigenetic Influences on Alzheimer's Disease

The precise role of environment-gene interactions (epigenetics) in the development and progression of Alzheimer's disease (AD) is unclear. This review focuses on the premise that radiotracer-specific PET imaging allows clinicians to visualize epigenetically influenced events and that such imaging may provide new, valuable insights for preventing, diagnosing, and treating AD. Current understanding of the role of epigenetics in AD and the principles underlying the use of PET radiotracers for in vivo diagnosis are reviewed. The relative efficacies of various PET radiotracers for visualizing the epigenetic influences on AD and their use for diagnosis are discussed. For example, [¹⁸F]FAHA demonstrates sites of differential HDAC activity, [¹⁸F]FDG indirectly illuminates sites of neuronal hypomethylation, and the carbon-11 isotope-containing Pittsburgh compound B ([¹¹C]PiB) images amyloid-beta plaque deposits. A definitive AD diagnosis is currently achievable only by postmortem histological observation of amyloid-beta plaques and tau neurofibrillary tangles. Therefore, reliable in vivo neuroimaging techniques could provide opportunities for early diagnosis and treatment of AD.

A 3-arm randomized controlled trial on the effects of dance movement intervention and exercises on elderly with early dementia

Background

Dementia is characterized by a progressive decline and deterioration of brain regions such as memory, spatial navigation and language, along with disturbances in daily functioning. Non-pharmacological interventions that offer a holistic approach by targeting cognitive functioning, prognosis and the psychological and social effects of dementia require rigorous investigation. The well-established benefits of physical activity for cognitive functioning and psychological support in dementia have been observed with dance-movement intervention. There is substantial evidence that dance-movement interventions provide emotional and social advantages. Thus, a randomized controlled trial (RCT) is planned to investigate the positive effects of a dance movement intervention, compared with mild physical exercise, on the physical and psychological well-being of elderly Chinese individuals with early dementia.

Methods/Design

A 3-arm RCT with waitlist control design will be used in this study. Two hundred and one elderly participants with very mild to mild dementia will be screened and randomized into the following groups: (i) dance movement based intervention, (ii) stretching and exercise intervention and (iii) no intervention waitlist-control group. The two intervention groups will receive a 1-h intervention, twice a week, for 12 weeks. The participants will be assessed four times over the course of 12 months: baseline before randomization, post-intervention (3 months), 6 months from baseline and 12 months from baseline. The primary outcomes will be compared between assessment points and between groups on neuropsychiatric symptoms, psychosocial well-being and cognitive and daily functioning. Secondary outcomes will assess the changes in salivary cortisol levels and their relationships with the primary outcome measures.

Discussion

This study will provide substantial evidence of the efficacy of a dance-movement-based intervention in slowing down dementia progression, due to its ability to act as a buffer against decline and improve areas affected by dementia. We also anticipate an association between cortisol levels and the outcome measures. The further development of this intervention into a structural program may be warranted for early psychosocial support among elderly populations.

Trial registration

The trial has been registered in the Chinese Clinical Trial Registry (ChiCTR-IOR-15006541).

Is Dysregulation of the HPA-Axis a Core Pathophysiology Mediating Co-Morbid Depression in Neurodegenerative Diseases?

There is increasing evidence of prodromal manifestation of neuropsychiatric symptoms in a variety of neurodegenerative diseases such as Parkinson's disease (PD) and Huntington's disease (HD). These affective symptoms may be observed many years before the core diagnostic symptoms of the neurological condition. It is becoming more apparent that depression is a significant modifying factor of the trajectory of disease progression and even treatment outcomes. It is therefore crucial that we understand the potential pathophysiologies related to the primary condition, which could contribute to the development of depression. The hypothalamic-pituitary-adrenal (HPA)-axis is a key neuroendocrine signaling system involved in physiological homeostasis and stress response. Disturbances of this system lead to severe hormonal imbalances, and the majority of such patients also present with behavioral deficits and/or mood disorders. Dysregulation of the HPA-axis is also strongly implicated in the pathology of major depressive disorder. Consistent with this, antidepressant drugs, such as the selective serotonin reuptake inhibitors have been shown to alter HPA-axis activity. In this review, we will summarize the current state of knowledge regarding HPA-axis pathology in Alzheimer's, PD and HD, differentiating between prodromal and later stages of disease progression when evidence is available. Both clinical and preclinical evidence will be examined, but we highlight animal model studies as being particularly useful for uncovering novel mechanisms of pathology related to co-morbid mood disorders. Finally, we purpose utilizing the preclinical evidence to better inform prospective, intervention studies.

Depression versus dementia: is this construct still relevant?

Cognitive impairment has long been identified as a component of late-life depression (LLD), and depressive symptoms are common in neurodegeneration. Depression may confer a greater risk of cognitive decline in a cognitively intact population and further cognitive decline in a mild cognitive impairment population compared with those without depression. Exploration of the link between cognitive impairment in LLD and the depressive features of neurodegeneration is an essential part of a diagnostic algorithm. In this review, we will discuss these links; we will address depressive symptoms as a risk factor for dementia and as a prodrome to dementia. We will review clinical subtypes and imaging markers as predictors of development of dementia in depressed patients and explore vascular etiologies. We will also explore LLD and dementia as a spectrum, rather than mutually exclusive diagnostic entities.

Absence of ALOX5 gene prevents stress-induced memory deficits, synaptic dysfunction and tauopathy in a mouse model of Alzheimer's disease

Although the initial events of Alzheimer's disease (AD) are still not known, it is clear that the disease in its sporadic form results from the combination of genetic and environmental risk factors. Among the latter, behavioral stress has been increasingly recognized as an important factor in the propagation of AD. However, the mechanisms underlying this modulation remain to be fully investigated. Since stress up-regulates the ALOX5 gene product, 5-lipoxygenase (5LO), herein we investigated its role in modulating stress-dependent development of the AD phenotype. To reach this goal, triple transgenic (3xTg) mice and 3xTg genetically deficient for 5LO were investigated after undergoing a restraint/isolation paradigm. In the present paper, we found that 28 days of restraint/isolation stress worsened tau phosphorylation and solubility, increased glycogen synthase kinase 3β activity, compromised long-term potentiation and impaired fear-conditioned memory recall in 3xTg animals, but not in 3xTg animals lacking 5LO (3xTg/5LO-/-). These results highlight the novel functional role that the ALOX5 gene plays in the development of the biochemical, electrophysiological and behavioral sequelae of stress in the AD context. They provide critical support that this gene and its expressed protein are viable therapeutic targets to prevent the onset or delay the progression of AD in individuals exposed to this risk factor.

Effects of corticotrophin-releasing factor receptor 1 antagonists on amyloid-β and behavior in Tg2576 mice

RATIONALE

Previous studies indicate that psychosocial stressors could accelerate amyloid-β (Aβ) levels and accelerate plaque deposition in mouse models of Alzheimer disease (AD). Stressors enhanced the release of corticotrophin-releasing factor (CRF), and exogenous CRF administration mimicked the effects of stress on Aβ levels in mouse models of AD. However, whether CRF receptor 1 (CRF1) antagonists could influence the stress-induced acceleration of an AD-like process in mouse models has not been well studied.

OBJECTIVE

We sought to examine whether CRF1 antagonists inhibit the effects of isolation stress on tissue Aβ levels, Aβ plaque deposition, and behaviors related to anxiety and memory in Tg2576 mice, and to investigate the molecular mechanism underlying such effects.

METHODS

Cohorts of Tg2576 mouse pups were isolated or group-housed at 21 days of age, and then the subgroups of these cohorts received daily intraperitoneal injections of the CRF1 antagonists, antalarmin or R121919 (5, 10, and 20 mg/kg), or vehicle for 1 week. Other cohorts of Tg2576 mouse pups were isolated or group-housed at 21 days of age, and then at 4 months of age, subgroups of these mice were administered antalarmin (20 mg/kg) or vehicle in their drinking water for 6 months. Finally, cultured primary hippocampal neurons from regular Tg2576 pups (P0) were incubated with CRF (0.1, 1, and 10 nM), antalarmin (100 nM) or H-89 (1 μM) for 48 h. Brain tissues or cultured neurons were collected for histological and biochemical analyses, and behavioral measures were collected in the cohorts of mice that were chronically stressed.

RESULTS

Administration of antalarmin at 20 mg/kg dose for 1 week significantly reduced Aβ1-42 levels in isolation stressed mice. Administration of antalarmin for 6 months significantly decreased plasma corticosterone levels, tissue Aβ1-42 levels, and Aβ plaque deposition in the brain and blocked the effects of isolation stress on behaviors related to anxiety and memory. Finally, incubation of neurons with 100 nM antalarmin inhibited the ability of 10 nM CRF to increase Aβ1-42 levels and protein kinase A IIβ expression. The effect of CRF1 on Aβ1-42 levels was also diminished by treatment with H-89, a c-AMP/PKA inhibitor.

CONCLUSIONS

These results suggest that CRF1 antagonists can slow an AD-like process in Tg2576 mice and that the c-AMP/PKA signaling pathway may be involved in this effect.

Antiglucocorticoid therapy for older adults with anxiety and co-occurring cognitive dysfunction: results from a pilot study with mifepristone

OBJECTIVES

In older adults with anxiety disorders, chronically elevated cortisol may contribute to cognitive impairment and elevated anxiety. We conducted a pilot study with mifepristone, a glucocorticoid receptor antagonist, as a potential treatment for late-life anxiety disorders and co-occurring cognitive dysfunction.

METHODS

Fifteen individuals 60 years and older with an anxiety disorder plus cognitive dysfunction participated in the 12-week study. In the first week, participants were randomly assigned to mifepristone 300 mg daily or placebo. In the subsequent 3 weeks, all participants received mifepristone 300 mg. Mifepristone was then discontinued, and the participants were reassessed 8 weeks later. We examined the following: (1) cognitive changes; (2) worry symptom severity; (3) safety and tolerability; and (4) salivary cortisol before, during, and after mifepristone exposure.

RESULTS

Overall safety, tolerability, and high retention supported the feasibility of this research. Participants with higher baseline cortisol levels (peak cortisol >6.0 ng/ml, n = 5) showed improvements in memory, executive function, and worry severity after 3-4 weeks of mifepristone with persistent memory and worry improvements 8 weeks after mifepristone discontinuation. Individuals with low-to-normal baseline cortisol (n = 8) showed little to no improvement. As expected, cortisol levels rose during mifepristone exposure and returned to pretreatment levels 8 weeks after mifepristone discontinuation. In the first week of treatment, there were no differences between placebo-treated and mifepristone-treated participants.

CONCLUSION

The results of this pilot study warrant further testing of antiglucocorticoid agents in late-life anxiety disorders with co-occurring cognitive dysfunction. Mifepristone is hypothesized to have benefits in patients with evidence of glucocorticoid excess. Directions for further study are discussed.

Association between autoimmune rheumatic diseases and the risk of dementia

AIM

Autoimmune rheumatic diseases (ARD) are characterized by systemic inflammation and may affect multiple organs and cause vascular events such as ischemic stroke and acute myocardial infarction. However, the association between ARD and increased risk of dementia is uncertain. This is a retrospective cohort study to investigate and compare the risk of dementia between patients clinically diagnosed with ARD and non-ARD patients during a 5-year follow-up period.

METHODS

Data were obtained from the Longitudinal Health Insurance Database 2000 (LHID2000). We included 1221 patients receiving ambulatory or hospitalization care and 6105 non-ARD patients; patients were matched by sex, age, and the year of index use of health care. Each patient was studied for 5 years to identify the subsequent manifestation of dementia. The data obtained were analyzed by Cox proportional hazard regression.

RESULTS

During the 5-year follow-up period, 30 ARD (2.48%) and 141 non-ARD patients (2.31%) developed dementia. During the 5-year follow-up period, there were no significant differences in the risks of any type of dementia (adjusted hazard ratio (HR), 1.18; 95% CI, 0.79-1.76) in the ARD group after adjusting for demographics and comorbidities.

CONCLUSIONS

Within the 5-year period, patients with and without ARD were found to have similar risks of developing dementia.

Implication of the nutritional and nonnutritional factors in the context of preservation of cognitive performance in patients with dementia/depression and Alzheimer disease

It has been postulated that Alzheimer disease (AD) is a systemic process, which involves multiple pathophysiological factors. A combination of pharmacotherapy and nonpharmacological interventions has been proposed to treat AD and other dementia. The nonpharmacological interventions include but are not limited to increasing sensory input through physical and mental activities, in order to modify cerebral blood flow and implementing nutritional interventions such as diet modification and vitamins and nutraceuticals therapy to vitalize brain functioning. This article highlights the recent research findings regarding novel treatment strategies aimed at modifying natural course of the disease and delaying cognitive decline through simultaneous implementation of pharmacological and nonpharmacological modulators as standardized treatment protocols.

Mifepristone alters amyloid precursor protein processing to preclude amyloid beta and also reduces tau pathology

BACKGROUND

Increased circulating glucocorticoids are features of both aging and Alzheimer's disease (AD), and increased glucocorticoids accelerate the accumulation of AD pathologies. Here, we analyzed the effects of the glucocorticoid receptor antagonist mifepristone (RU486) in the 3xTg-AD mouse model at an age where hippocampal damage leads to high circulating corticosterone levels.

METHODS

The effects of mifepristone were investigated in 3xTg-AD mice using a combination of biochemical, histological, and behavior analyses.

RESULTS

Mifepristone treatment rescues the pathologically induced cognitive impairments and markedly reduces amyloid beta (Aβ)-load and levels, as well as tau pathologies. Analysis of amyloid precursor protein (APP) processing revealed concomitant decreases in both APP C-terminal fragments C99 and C83 and the appearance of a larger 17-kDa C-terminal fragment. Hence, mifepristone induces a novel C-terminal cleavage of APP that prevents it being cleaved by α- or β-secretase, thereby precluding Aβ generation in the central nervous system; this cleavage and the production of the 17-kDa APP fragment was generated by a calcium-dependent cysteine protease. In addition, mifepristone treatment also reduced the phosphorylation and accumulation of tau, concomitant with reductions in p25. Notably, deficits in cyclic-AMP response element-binding protein signaling were restored with the treatment.

CONCLUSIONS

These preclinical results point to a potential therapeutic role for mifepristone as an effective treatment for AD and further highlight the impact the glucocorticoid system has as a regulator of Aβ generation.

Plasma cortisol in Alzheimer's disease with or without depressive symptoms

Background

Cortisol is presumed to be a risk factor for stress- and age-related disorders, such as depressive disorder and Alzheimer’s disease (AD). The aim of this study was to investigate the association of plasma cortisol concentration with AD in presence or absence of comorbid depressive symptoms.

Material/Methods

Plasma cortisol concentration was measured in 80 AD patients (35 of them with depressive symptoms), 27 elderly depressive patients without AD, and 37 elderly controls.

Results

Compared to controls, a significant increase of mean plasma cortisol was found in AD patients but not in depressive patients. Plasma cortisol was positively correlated with cognitive impairment in AD patients. We confirmed a U-shaped association between plasma cortisol and major depression and a linear association between plasma cortisol and AD without depressive symptoms. Significantly increased relative risk of disease in people with high plasma cortisol was found for AD with depressive symptoms and for AD with mild dementia.

Conclusions

Plasma cortisol reflects the degree of cognitive impairment in AD rather than the severity of comorbid depression. We confirmed that both hypercortisolemia and hypocortisolemia are associated with depressive disorder. Significant association between high plasma cortisol and AD was found, supporting the use of high plasma cortisol as a component of a panel of biochemical markers for AD with depressive symptoms as well as AD in the early stage of dementia development.

Neurodegenerative and inflammatory biomarkers in cerebrospinal fluid in patients with Cushing's syndrome in remission

OBJECTIVE

Patients with Cushing's syndrome (CS) in long-term remission have impaired cognitive function. Cerebrospinal fluid (CSF) biomarkers are important diagnostic tools in the work-up of patients with cognitive impairment. The aim of this study was to analyze neurodegenerative and inflammatory biomarkers in the CSF of patients with CS in remission.

DESIGN

A cross-sectional, single-center study.

PATIENTS

Twelve women previously treated for CS and six healthy subjects.

MEASUREMENTS

Neurodegenerative CSF markers: total tau, hyperphosphorylated tau, amyloid beta peptides, soluble amyloid precursor protein alpha and beta, neurofilament light proteins, glial fibrillary acidic protein, and monocyte chemoattractant protein 1; and inflammatory CSF markers: interferon gamma, interleukin (IL) 1B, IL2, IL4, IL5, IL8, IL10, IL12p70, IL13, and tumor necrosis factor alpha.

RESULTS

The mean age (mean±S.D.) was similar in patients with CS in remission (44.9±14 years) and healthy subjects (42.3±15.7 years; P=0.726). No differences were observed in the concentrations of any neurodegenerative biomarkers between the patients and healthy subjects. Nor were the concentrations of inflammatory biomarkers different between the groups.

CONCLUSIONS

The pattern of neurodegenerative and inflammatory biomarkers in the CSF of patients with CS in remission does not differ from that of the healthy subjects. The underlying mechanisms of the cognitive deficits in patients with CS in remission are different from those observed in patients with neurodegenerative disorders and remain to be explained.

Propranolol reduces cognitive deficits, amyloid β levels, tau phosphorylation and insulin resistance in response to chronic corticosterone administration

Chronic exposure to glucocorticoids might result not only in insulin resistance or cognitive deficits, but it is also considered as a risk factor for pathologies such as Alzheimer's disease. Propranolol is a β-adrenergic antagonist commonly used in the treatment of hypertension or acute anxiety. The effects of propranolol (5 mg/kg) have been tested in a model of chronic corticosterone administration (100 μg/ml, 4 wk) in drinking water. Corticosterone administration led to cognitive impairment in the novel object recognition test that was reversed by propranolol. Increased levels of Aβ in the hippocampus of corticosterone-treated mice were counteracted by propranolol treatment, purportedly through an increased IDE expression. Chronic corticosterone treatment induced responses characteristic of insulin resistance, as increased peripheral insulin levels, decreased activation of the insulin receptor (pIR) and decreased associated intracellular pathways (pAkt). These effects might be related to a decreased c-Jun N terminal kinase 1 expression. Again, propranolol was able to counteract all corticosterone-induced effects. One of the main kinases involved in tau phosphorylation, glycogen synthase kinase 3β (GSK3β), which is inactivated by phosphorylation by pAkt, was found to be decreased after corticosterone and increased after propranolol treatment. Concomitant changes in pTau expression were found. Overall, these data further strengthen the potential of propranolol as a therapeutic agent for pathologies associated with the interaction glucocorticoids-insulin resistance and the development of relevant cellular processes for Alzheimer's disease.

Effects of perceived long-term stress on subjective and objective aspects of memory and cognitive functioning in a middle-aged population-based sample

The longitudinal effects of perceived stress on measures of memory and two other cognitive functions (word fluency, visuospatial ability) in a middle-aged sample (40-60 years, M age = 47.1 years, SD = 6.1 years; n = 192) were examined. A group describing themselves as stressed in general at baseline, and at follow-up measurement 5 and 10 years later (n = 96) was compared with a matched (age, sex) low-stress group (n = 96). The results revealed more depressive symptoms over time in the high-stress group. With regard to memory, a dissociation between subjective and objective measures was observed. Specifically, participants in the high-stress group rated their memory as worse over time as compared with controls, and reported a higher frequency of occurrence of everyday memory failures, effects partly independent of depressive symptoms. However, the groups did not differ in terms of objective episodic memory performance, word fluency or block design performance, with stable levels of performance over time regardless of perceived stress. The lack of effects of stress on cognitive performance is discussed in the light of factors such as stress level, age of the participants, and other individual difference factors.

Religion, spirituality, and health: the research and clinical implications

This paper provides a concise but comprehensive review of research on religion/spirituality (R/S) and both mental health and physical health. It is based on a systematic review of original data-based quantitative research published in peer-reviewed journals between 1872 and 2010, including a few seminal articles published since 2010. First, I provide a brief historical background to set the stage. Then I review research on R/S and mental health, examining relationships with both positive and negative mental health outcomes, where positive outcomes include well-being, happiness, hope, optimism, and gratefulness, and negative outcomes involve depression, suicide, anxiety, psychosis, substance abuse, delinquency/crime, marital instability, and personality traits (positive and negative). I then explain how and why R/S might influence mental health. Next, I review research on R/S and health behaviors such as physical activity, cigarette smoking, diet, and sexual practices, followed by a review of relationships between R/S and heart disease, hypertension, cerebrovascular disease, Alzheimer's disease and dementia, immune functions, endocrine functions, cancer, overall mortality, physical disability, pain, and somatic symptoms. I then present a theoretical model explaining how R/S might influence physical health. Finally, I discuss what health professionals should do in light of these research findings and make recommendations in this regard.

Sex-biased stress signaling: the corticotropin-releasing factor receptor as a model

Sex differences in the prevalence or severity of many diseases and in the response to pharmacological agents are well recognized. Elucidating the biologic bases of these differences can advance our understanding of the pathophysiology of disease and facilitate the development of treatments. Despite the importance to medicine, this has been an area of limited research. Here, we review physiologic, cellular, and molecular findings supporting the idea that there are sex differences in receptor signaling and trafficking that can be determinants of pathology. The focus is on the receptor for corticotropin-releasing factor (CRF), the orchestrator of the stress response, which has been implicated in diverse stress-related diseases that show a female prevalence. Data are reviewed that show sex differences in the association of the CRF receptor (CRF1) with the Gs protein and β-arrestin 2 that would render females more responsive to acute stress and less able to adapt to chronic stress as a result of compromised CRF1 internalization. Because β-arrestin 2 serves to link CRF1 to Gs-independent signaling pathways, this sex-biased signaling is proposed to result in distinct cellular responses to stress that are translated to different physiologic and behavioral coping mechanisms and that can have different pathologic consequences. Because stress has been implicated in diverse medical and psychiatric diseases, these sex differences in CRF1 signaling could explain sex differences in a multitude of disorders. The possibility that analogous sex differences may occur with other G-protein-coupled receptors underscores the impact of this effect and is discussed.

The relationship between cortisol and verbal memory in the early stages of Huntington's disease

Hypothalamic pituitary adrenal (HPA) axis hyperactivity has been linked to learning and memory difficulties in a range of neurodegenerative and neuropsychiatric conditions. In Huntington's disease (HD), both declines in learning and memory and HPA axis dysfunction are present early in the disease. However, the relationship between specific learning and memory deficits and HPA axis functioning in HD has not been examined. The aim of this study was to investigate cortisol levels in relation to verbal learning and memory in pre-diagnosed (pre-HD) participants and patients at the early stages of diagnosed HD (early-HD). Cortisol concentration was assayed in saliva samples from 57 participants (17 early-HD, 20 pre-HD, and 20 controls) at four time-points across a 24-h period. Verbal memory was assessed using the California Verbal Learning Test-Second Edition (CVLT-II). We focused statistical analyses on the late evening cortisol concentration, and examined cortisol levels and verbal memory function in relation to diagnostic group (control, pre-HD, early-HD), and in a separate set of analyses combining pre-HD and early-HD (and excluding controls) we also examined cortisol and verbal memory performance in relation to the severity of HD-related motor signs. Of these two classification approaches, HD motor sign severity was more strongly associated with high evening cortisol levels and both reduced information encoding and memory retrieval. Separately, there was also a trend of higher cortisol levels in pre-HD. The findings suggest hypercortisolism and the underlying pathological changes may begin many years before a clinical diagnosis is made, but the memory decline associated with HPA axis disturbance may only become detectable once motor signs become pronounced.

The neuroendocrine control of the innate immune system in health and brain diseases

The innate immune reaction takes place in the brain during immunogenic challenges, injury, and disease. Such a response is highly regulated by numerous anti-inflammatory mechanisms that may directly affect the ultimate consequences of such a reaction within the cerebral environment. The neuroendocrine control of this innate immune system by glucocorticoids is critical for the delicate balance between cell survival and damage in the presence of inflammatory mediators. Glucocorticoids play key roles in regulating the expression of inflammatory genes, and they also have the ability to modulate numerous functions that may ultimately lead to brain damage or repair after injury. Here we review these mechanisms and discuss data supporting both neuroprotective and detrimental roles of the neuroendocrine control of innate immunity.

Stress-induced anhedonia is associated with an increase in Alzheimer's disease-related markers

BACKGROUND AND PURPOSE

Stress is believed to be associated with the development of neuropsychiatric disorders, including Alzheimer's disease (AD). We have studied mechanisms implicated in vulnerability to stress and the relationship with changes in AD-related markers.

EXPERIMENTAL APPROACH

Anhedonia induced by a chronic mild stress (CMS) procedure, applied for 6 weeks, was used to select rats vulnerable or resistant to stress. Sucrose intake, the Porsolt forced swimming test and cognitive deficits in the novel object recognition test (NORT) were used to characterize vulnerable and resilient rats. The antidepressant venlafaxine (20 mg·kg(-1) p.o.) or saline was administered daily during the last 2 weeks of CMS. Biochemical markers affected by stress, PKB, ERK and synaptophysin, and those associated with AD, amyloid β-protein (Aβ), β-secretase (BACE1) and τ phosphorylation, were measured in the hippocampus.

KEY RESULTS

After CMS, 40% of rats were resistant to the development of anhedonia (CMS-resistant to stress), whereas the remaining were responsive [CMS-anhedonic (CMSA)]. Only CMSA rats displayed significant increases in immobility time in the forced swimming test and cognitive deficits in the NORT, and significant decreases in synaptophysin, phosphorylated PKB and phosphorylated ERK1/2 expression in the hippocampus. Increased levels of Aβ40, BACE1 and τ phosphorylation were also found only in CMSA rats. All these effects in CMSA rats were reverted by treatment with venlafaxine.

CONCLUSIONS AND IMPLICATIONS

Vulnerability to stress might constitute a risk factor for the development of AD, and pharmacological treatment with venlafaxine may represent a therapeutic strategy for the treatment of stress-related disorders, including AD.

Treatment-related alteration of cortisol predicts change in neuropsychological function during acute treatment of late-life anxiety disorder

OBJECTIVE

Older adults with anxiety disorders are burdened by impairment in neurocognition, which may be mediated by elevated circulating cortisol levels. In a randomized controlled trial of acute serotonin-reuptake inhibitor treatment for late-life anxiety disorder, we examined whether change in salivary cortisol concentrations during treatment predicted improvements in measures of memory and executive function.

METHODS

We examined 60 adults aged 60 years and older, who took part in a 12-week trial of escitalopram versus placebo for generalized anxiety disorder. All subjects had pre-treatment and post-treatment assessments that included monitoring of peak and total daily cortisol and a comprehensive neuropsychological evaluation.

RESULTS

Salivary cortisol changes during treatment showed significant associations with changes in immediate and delayed memory but no association with executive tasks (measures of working memory and set shifting). Analyses suggested that a decrease in cortisol due to serotonin-reuptake inhibitor treatment was responsible for the memory changes: memory improvement was seen with cortisol reduction among patients receiving escitalopram but not among patients receiving placebo.

CONCLUSION

Serotonin-reuptake inhibitor-induced alteration in circulating cortisol during treatment of generalized anxiety disorder predicted changes in immediate and delayed memory. This finding suggests a novel treatment strategy in late-life anxiety disorders: targeting hypothalamic-pituitary- adrenal axis dysfunction to improve memory.

Restraint stress in rats alters gene transcription and protein translation in the hippocampus

Stress is a relatively new and emerging risk factor for Alzheimer's disease (AD). Severe stress can alter brain characteristics such as neuronal plasticity, due to changes in the metabolism of cytoskeletal proteins. In this study, male Wistar rats were exposed to restraint stress (RS) for 5 h daily for different time periods. At the end of the exposure periods, the amounts of β-actin, cofilin, amyloid precursor protein (APP) and mitogen-activated protein kinase 1 (MAPK-1) RNAs and proteins were investigated. The mRNA expressions of β-actin, cofilin and MAPK-1 followed U-shaped time course. Acute (3 days) and chronic (21 days) RS caused a fourfold and tenfold increases, respectively, in hippocampal β-actin mRNA expression. In the case of cofilin mRNA expression, elevations were detected in the hippocampus on days 3, 7 and 21. The APP mRNA level was increased on day 21. On protein level, chronic stress elevated the levels of β-actin, cofilin and APP in the hippocampus. These results suggest that stress causes the induction of some genes and proteins that are also elevated in AD selectively in the hippocampal region of the rat brain.

Dexamethasone and Aβ₂₅-₃₅ accelerate learning and memory impairments due to elevate amyloid precursor protein expression and neuronal apoptosis in 12-month male rats

Alzheimer's disease (AD) is an irreversible, progressive brain disorder of the elderly characterized by learning and memory impairment. Stress level glucocorticoids (GCs) and β-amyloid (Aβ) peptides deposition are found to be correlated with dementia progression in patients with AD. However, little is known about the simultaneous effects of glucocorticoids and Aβ on learning and memory impairment and its mechanism. In this study, 12-month-old male rats were chronically treated with Aβ(25-35) (10 μg/rat, hippocampal CA1 injection) and dexamethasone (DEX, 1.5mg/kg) for 14 days to investigate the effects of DEX and Aβ(25-35) treatment on learning and memory impairments, pathological changes, neuronal ultrastructure, amyloid precursor protein (APP) processing and neuronal cell apoptosis. Our results showed that DEX or Aβ(25-35) treatment alone for 14 days had caused slight damage on learning and memory impairments and hippocampal neurons, but damages were significantly increased with DEX+Aβ(25-35) treatment. And the mRNA levels of the APP, β-secretase and caspase 3 were significantly increased after DEX+Aβ(25-35) treatment. The immunohistochemistry demonstrated that APP, Aβ(1-40), caspase 3 and cytochrome c in hippocampus CA1 were significantly increased. Furthermore, Hoechst 33258 staining and Aβ(1-40) ELISA results showed that DEX+Aβ(25-35) treatment induced hippocampus CA1 neuron apoptosis and increased the level of Aβ(1-40). The results suggest that the simultaneous effects of GCs and Aβ may have important roles in the etiopathogenesis of AD, and demonstrate that stressful life events and GC therapy may increase the toxicity of Aβ and have cumulative impacts on the course of AD development and progression.

Identification of a blood-based biomarker panel for classification of Alzheimer's disease

An ideal diagnostic test for Alzheimer's disease (AD) should be non-invasive and easily applicable. Thus, there is a clear need to search for biomarkers in blood. In the present study, we have used multivariate data analysis [support vector machine (SVM)] to investigate whether a blood-based biomarker panel allows discrimination between AD patients and healthy controls at the individual level. We collected a total of 155 serum samples from individuals with early AD and age-matched healthy controls and measured serum levels of 24 markers involved in several biological pathways by ELISA. The dataset was randomly split into a training set for predictor discovery and classification training and a test set for class prediction of blinded samples (3:1 ratio) to evaluate the chosen predictors and parameters. After selection of a feature group of the three most discriminative parameters (cortisol, von Willebrand factor, oxidized LDL antibodies) in the training set, the application of SVM to the training/independent test dataset resulted in an 81.7%/87.1% correct classification for AD and control subjects. In conclusion, we identified a panel of three blood markers, which allowed SVM-based distinguishing of AD patients from healthy controls on a single-subject classification level with clinically relevant accuracy and validity. Blood-based biomarkers might have utility in AD diagnostics as screening tool before further classification with CSF biomarkers and imaging. Future studies should examine whether blood-based biomarkers may also be useful to differentiate AD patients from other dementias.

The effect of different maternal deprivation paradigms on the expression of hippocampal glucocorticoid receptors, calretinin and calbindin-D28k in male and female adolescent rats

Maternal deprivation (MD) is a well-established protocol used to investigate neurobiological changes that are associated with the etiology of and vulnerability to stress-related diseases in animal models. The resulting psychophysiological effects, the timing and duration of these adverse stimuli, and the method by which they exert their effects on the animals remain unclear. This study characterized differences in the hippocampal expression of glucocorticoid receptors (GRs) and the calcium-binding proteins calretinin (CALR) and calbindin-D28k (CALB) in male and female rats that underwent different MD paradigms during the stress hyporesponsive period (SHRP). Both GRs and the two calcium-binding proteins were much more abundant in females than in males. MD paradigms had a significant effect on CALR and CALB expression in both males and females but affected GR levels only in males. Additionally, expression of the two calcium-binding proteins in the hippocampus responded differently to MD-induced stress, especially in females. Taken together, these results indicate that females are able to modulate their response to stress better than males.

Occlusal disharmony increases amyloid-β in the rat hippocampus

Amyloid-β plays a causative role in Alzheimer's disease. Occlusal disharmony causes chronic psychological stress, and psychological stress increases amyloid-β accumulation. The purpose of the present study was to investigate whether occlusal disharmony-induced psychological stress affects the accumulation of amyloid-β and its related gene expressions in the rat hippocampus. Eight-week-old male Wistar rats (n = 18) were divided into three groups of six rats each: (1) a control group that received no treatment for 8 weeks; (2) an occlusal disharmony group that underwent cutoff maxillary molar cusps for 8 weeks; and (3) a recovered group that underwent cutoff maxillary molar cusps for 4 weeks followed by recovery for 4 weeks. Occlusal disharmony increased plasma corticosterone levels in a time-dependent manner. Levels of amyloid-β 40 and 42, glucocorticoid receptor (Gr) protein, and cleaved caspase 3 (Casp3) as well as gene expressions of amyloid precursor protein, beta-secretase, Casp3, and Gr in the hippocampus in the occlusal disharmony group were significantly higher than those in the control group (P < 0.016). These findings were significantly improved by recovery of occlusion (P < 0.016). These results indicate that psychological stress induced by occlusal disharmony reversibly induces amyloid-β 40 and 42 in the rat hippocampus through the glucocorticoid signal.

Restraint stress and repeated corticotrophin-releasing factor receptor activation in the amygdala both increase amyloid-β precursor protein and amyloid-β peptide but have divergent effects on brain-derived neurotrophic factor and pre-synaptic proteins in the prefrontal cortex of rats

Both environmental stress and anxiety may represent important risk factors for Alzheimer's disease (AD) pathogenesis. Previous studies demonstrate that restraint stress is associated with increased amyloid beta (Aβ) and decreased brain-derived neurotrophic factor (BDNF) levels in the brain. Aβ deposition, synaptic loss, and neurodegeneration define major hallmarks of AD, and BDNF is responsible for the maintenance of neurons. In contrast to restraint stress, repeated injections of sub-anxiogenic doses of the corticotrophin releasing factor receptor agonist urocortin1 (Ucn1) administered in the basolateral amygdala (BLA) of rats elicits persistent anxiety-like responses. We hypothesized that both restraint stress and Ucn1-induced anxiety would contribute to a neurobiological abnormality that would change the levels of Aβ precursor protein (APP) and Aβ as well as BDNF and pre-synaptic markers. In the first experiment, adult male Wister rats (n=5) were subjected to 3-h restraint, as compared to unstressed controls. In the second experiment, adult male Wistar rats (n=6) were subjected to sub-anxiogenic doses of Ucn1 (6 fmol/100 nl) administered in the BLA for 5 consecutive days, as compared to controls. Following each respective treatment, the social interaction (SI) test was performed to measure anxiety-like behavior. Protein studies were then conducted to quantify levels of APP, Aβ, BDNF and presynaptic proteins in the prefrontal cortex (PFC). In both experiments, we detected differences in either corticosterone levels or the SI test associated with a stress response. Furthermore, our findings indicate that both restraint stress and Ucn1 administration in the BLA lead to increased APP and Aβ deposition. However, restraint-induced stress leads to reductions in the levels of BDNF and presynaptic markers, while Ucn1-induced anxiety is associated with increases in the levels of each respective protein. This demonstrates a convergent role for stress response and Ucn1-induced anxiety in the regulation of APP and Aβ, but opposing roles for each respective treatment in the regulation of BDNF and presynaptic markers.

Elevated cortisol in older adults with generalized anxiety disorder is reduced by treatment: a placebo-controlled evaluation of escitalopram

BACKGROUND

Generalized anxiety disorder (GAD) is a common disorder in older adults, which has been linked to hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis in this age group. The authors examined whether treatment of GAD in older adults with a selective serotonin reuptake inhibitor (SSRI) corrects this HPA axis hyperactivity.

METHODS

The authors examined adults aged 60 years and older with GAD in a 12-week randomized controlled trial comparing the SSRI escitalopram with placebo. The authors collected salivary cortisol at six daily time points for 2 consecutive days to assess peak and total (area under the curve) cortisol, both at baseline and posttreatment.

RESULTS

Compared with placebo-treated patients, SSRI-treated patients had a significantly greater reduction in both peak and total cortisol. This reduction in cortisol was limited to patients with elevated (above the median) baseline cortisol, in whom SSRI-treated patients showed substantially greater reduction in cortisol than did placebo-treated patients. Reductions in cortisol were associated with improvements in anxiety. Additionally, genetic variability at the serotonin transporter promoter predicted cortisol changes.

CONCLUSIONS

SSRI treatment of GAD in older adults reduces HPA axis hyperactivity. Further research should determine whether these treatment-attributable changes are sustained and beneficial.

Protective effect of extract of Astragalus on learning and memory impairments and neurons' apoptosis induced by glucocorticoids in 12-month-old male mice

Alzheimer's disease (AD) is a chronic neurodegenerative disorder marked by a progressive loss of memory and cognitive function. Stress-level glucocorticoids are correlated with dementia progression in patients with AD. In this study, 12-month male mice were chronically treated with stress-level dexamethasone (DEX, 5 mg/kg) and extract of Astragalus (EA, 10, 20, and 40 mg/kg) or Ginsenoside Rg1 (Rg1, 6.5 mg/kg) for 21 days. We investigated the protective effect of EA against DEX injury in mice and its action mechanism. Our results indicate that DEX can induce learning and memory impairments and neuronal cell apoptosis. The mRNA levels of caspase-3 are selectively increased after DEX administration. The results of immunohistochemistry demonstrate that caspase-3 and cytochrome c in hippocampus (CA1, CA3) and neocortex are significantly increased. Furthermore, DEX treatment increased the activity of caspase-9 and caspase-3. Treatment groups with EA (20 and 40 mg/kg) or Rg1 (6.5 mg/kg) significantly improve learning and memory, downregulate the mRNA level of caspase-3, decrease expression of caspase-3 and cytochrome c in hippocampus (CA1, CA3) and neocortex, and inhibit activity of caspase-9 and caspase-3. The present findings highlight a possible mechanism by which stress level of DEX accelerates learning and memory impairments and increases neuronal apoptosis and the potential neuronal protection of EA.

A common pathogenic mechanism linking type-2 diabetes and Alzheimer's disease: evidence from animal models

The failure of large-scale drug trials targeting the amyloidogenic pathway in Alzheimer's disease (AD) is increasing the need to identify a novel pathogenic mechanism. Studies finding a relationship between sporadic AD and type-2 diabetes mellitus (T2DM) are now receiving more attention. The risk for developing both T2DM and sporadic AD increases exponentially with age, and having T2DM doubles the risk of developing AD. The postmortem brains of AD patients show altered activities of insulin receptors and downstream molecules, as well as reduced protein and mRNA levels of insulin. More-recent laboratory research using animal models has identified mechanisms that are shared by diabetes and AD. Exogenous application of streptozotocin, which disrupts systemic insulin secretion, results in insulin deficiency, increased tau phosphorylation, and cognitive impairments that can be reversed by exogenous insulin supplementation. However, AD pathology is more severe in T2DM animal models exhibiting hyperinsulinemia and insulin resistance, and this is not modulated by insulin. The symptoms of this AD pathology included increased tau phosphorylation at multiple sites, increased tau cleavage, and greater neuronal and synaptic damage, even with increased amyloid β protein production. It has therefore been suggested that hyperinsulinemia and insulin resistance represent major factors underlying AD in T2DM. A recent study involving cross-mating ob/ob and amyloid precursor protein transgenic mice provided evidence that T2DM and AD aggravate each other, and suggested that cerebral vessels constitute an important substrate that is commonly damaged by the two major disorders. Given the evidence provided by animal models, further investigation of the mechanisms underlying T2DM in AD should help to identify potential treatment targets in AD.

Stress, exercise, and Alzheimer's disease: a neurovascular pathway

Genetic factors are known to play a role in Alzheimer's disease (AD) vulnerability, yet less than 1% of incident AD cases are directly linked to genetic causes, suggesting that environmental variables likely play a role in the majority of cases. Several recent human and animal studies have examined the effects of behavioral factors, specifically psychological stress and exercise, on AD vulnerability. Numerous animal studies have found that, while stress exacerbates neuropathological changes associated with AD, exercise reduces these changes. Some human studies suggest that psychological stress can increase the risk of developing AD, while other studies suggest that exercise can significantly reduce AD risk. Most animal studies investigating the mechanisms responsible for the effects of these behavioral factors have focused on neuronal processes, including the effects of stress hormones and neurotrophic factors on the neuropathological hallmarks of AD, namely amyloid-beta (Aβ) deposition and tau-phosphorylation. However, cumulative evidence indicates that, in humans, AD is associated with the presence of cerebrovascular disease, and cardiovascular risk factors are associated with increased risk of developing AD. There is an extensive literature demonstrating that behavioral factors, particularly stress and exercise, can powerfully modulate the pathophysiology of vascular disease. Thus, the following model proposes that the influence of stress and exercise on AD risk may be partially due to the effects of these behavioral factors on vascular homeostasis and pathology. These effects are likely due to both indirect modification of AD risk through alterations in vascular risk factors, such as hypertension, diabetes, and aortic stiffening, as well as direct influence on the cerebrovasculature, including changes in cerebral blood flow, angiogenesis, and vascular disease. Future studies examining the effects of behavioral factors on AD risk should incorporate measures of both peripheral and cerebral vascular function to further our understanding of the mechanisms by which behavior can modify AD susceptibility. Greater knowledge of the molecular mechanisms behind these behavioral effects would further our understanding of the disease and lead to innovative treatment and preventive approaches.

Chronic stress, cognitive functioning and mental health

This review aims to discuss the evidence supporting the link between chronic stress, cognitive function and mental health. Over the years, the associations between these concepts have been investigated in different populations. This review summarizes the findings that have emerged from older populations as well as from populations suffering from pathological aging, namely Mild Cognitive Impairment and Alzheimer's Disease. Although older adults are an interesting population to study in terms of chronic stress, other stress-related diseases can occur throughout the lifespan. The second section covers some of these stress-related diseases that have recently received a great deal of attention, namely burnout, depression, and post-traumatic stress disorder. Given that chronic stress contributes to the development of certain pathologies by accelerating and/or exacerbating pre-existing vulnerabilities that vary from one individual to the other, the final section summarizes data obtained on potential variables contributing to the association between chronic stress and cognition.

Health-related conditions and depression in elderly mexican american and non-Hispanic white residents of a United States-Mexico border county: moderating effects of educational attainment

We investigated the prevalence of "high" levels of depressive symptomatology and 13 health-related medical conditions in elderly Mexican American (MA) and non-Hispanic white (NHW) residents of El Paso County, Texas. We analyzed the extent to which depressive symptoms in this population are associated with these conditions. Elderly MA residents possessed a higher prevalence of current depression, a relatively unique health-related condition profile, and were more likely to experience a set of conditions that impede participation in daily life-conditions that we found to be strongly associated with high depressive symptomatology in the elderly. After adjusting for educational attainment, using multiple regression analyses, depression was not associated with ethnicity and only six of the health related conditions showed significant differences between MA and NHW subjects. We believe these results provide an important insight into the mechanism of health-related conditions and depressive symptomatology in a large sample of elderly MAs; and how conditions typically attributed to MA ethnicity may in actuality be an artifact of socioeconomic status variables such as educational-attainment.