Early life adversity as a risk factor for cognitive impairment and Alzheimer's disease

COVID-19 lockdown effects on adolescent brain structure suggest accelerated maturation that is more pronounced in females than in males

Adolescence is a period of substantial social-emotional development, accompanied by dramatic changes to brain structure and function. Social isolation due to lockdowns that were imposed because of the COVID-19 pandemic had a detrimental impact on adolescent mental health, with the mental health of females more affected than males. We assessed the impact of the COVID-19 pandemic lockdowns on adolescent brain structure with a focus on sex differences. We collected MRI structural data longitudinally from adolescents prior to and after the pandemic lockdowns. The pre-COVID data were used to create a normative model of cortical thickness change with age during typical adolescent development. Cortical thickness values in the post-COVID data were compared to this normative model. The analysis revealed accelerated cortical thinning in the post-COVID brain, which was more widespread throughout the brain and greater in magnitude in females than in males. When measured in terms of equivalent years of development, the mean acceleration was found to be 4.2 y in females and 1.4 y in males. Accelerated brain maturation as a result of chronic stress or adversity during development has been well documented. These findings suggest that the lifestyle disruptions associated with the COVID-19 pandemic lockdowns caused changes in brain biology and had a more severe impact on the female than the male brain.

Enduring Neurobiological Consequences of Early-Life Stress: Insights from Rodent Behavioral Paradigms

Stress profoundly affects physical and mental health, particularly when experienced early in life. Early-life stress (ELS) encompasses adverse childhood experiences such as abuse, neglect, violence, or chronic poverty. These stressors can induce long-lasting changes in brain structure and function, impacting areas involved in emotion regulation, cognition, and stress response. Consequently, individuals exposed to high levels of ELS are at an increased risk for mental health disorders like depression, anxiety, and post-traumatic stress disorders, as well as physical health issues, including metabolic disorders, cardiovascular disease, and cancer. This review explores the biological and psychological consequences of early-life adversity paradigms in rodents, such as maternal separation or deprivation and limited bedding or nesting. The study of these experimental models have revealed that the organism's response to ELS is complex, involving genetic and epigenetic mechanisms, and is associated with the dysregulation of physiological systems like the nervous, neuroendocrine, and immune systems, in a sex-dependent fashion. Understanding the impact of ELS is crucial for developing effective interventions and preventive strategies in humans exposed to stressful or traumatic experiences in childhood.

Gender differences in the associations of psychosocial trauma and acute medical stressors with immune system activation and dementia risk

Objective: The purpose of this article is to provide a narrative review synthesizing the literature on differences between women and men in relationships among certain stressors associated with immune system activation and their relationship to cognitive dysfunction and dementia. Method: We review the cycle of stress leading to neuroinflammation via cortisol and neurochemical alterations, cell-mediated immune system activation, and pro-inflammatory cytokines, and how this is implicated in the development of dementia. We follow this by discussing sex differences in stress physiology and immune function. We then review the work on early life adversity (ELA) and adverse childhood experiences (ACEs), post-traumatic stress disorder, acute medical stressors, and their associations with cognitive dysfunction and dementia. Throughout, we emphasize women's presentations and issues unique to women (e.g. trauma disorder prevalence). Conclusions: There is a need for more mechanistic and longitudinal studies that consider trauma accumulation, both physical and emotional, as well as a greater focus on traumas more likely to occur in women (e.g. sexual abuse), and their relationship to early cognitive decline and dementia.

Cumulative Effect of Psychosis and Aging on Cognitive Function in Patients Diagnosed With Schizophrenia Spectrum Disorders: A Cognitive Domain Approach

BACKGROUND

Schizophrenia spectrum disorders are characterized by cognitive decline, which is evident even in the prodromal phase. Aging is a complex gradual procedure that affects, among other organs, the central nervous system, resulting in age-related cognitive decline.

OBJECTIVE

The objective of this study is to assess the cognitive function of patients diagnosed with psychotic disorders, in comparison with healthy controls, along the age spectrum.

METHODS

Sixty patients diagnosed with schizophrenia spectrum disorders in remission, 20-59 years old, and 60 healthy controls, matched by age and educational level, from the region of Thessaly in Central Greece, were evaluated, with respect to their cognitive performance, using the Greek version of the Montreal Cognitive Assessment (MoCA). Correlations between age and MoCA total and cognitive domains' scores, as well as statistical analysis of variance (ANOVA) and t-test among age groups, were performed using Statistical Product and Service Solutions (SPSS, version 23; IBM SPSS Statistics for Windows, Armonk, NY).

RESULTS

The MoCA score was negatively correlated with age, both in the patients' group (p<0.001) and in the control group (p=0.001). A significant statistical difference in mean MoCA scores between patients and healthy controls was observed, not only in the total sample (p<0.001) but also in all age groups (20-29: p=0.006, 40-49: p=0.024, 50-59: p<0.001), except for age group 30-39 (30-39: p=0.356). Statistically significant differences were also found between patients and healthy controls in the total sample, regarding specific cognitive domains, in the visuospatial and executive function domain (p=0.01), attention domain (p<0.001), language domain (p<0.001), and orientation domain (p<0.005). Interestingly, different deterioration patterns in cognitive domains were observed in each age group. Specifically, in the age group 20-29, statistically significant differences were found between patients and healthy controls in the language domain (p<0.014) and orientation domain (p<0.041). No difference was found in the age group 30-39, while statistically significant differences were found between patients and healthy controls in the age group 40-49 in the attention domain (p<0.001) and language domain (p<0.001). Finally, in the age group 50-59, such differences were found in the visuospatial and executive function domain (p=0.041), attention domain (p=0.006), and language domain (p=0.001). Statistically significant cognitive decline occurs in a shorter period in the patients' group, suggesting an accelerated cognitive decline in psychotic patients after middle age.

CONCLUSIONS

Age-related cognitive decline in psychotic patients occurs at an accelerated rate in relation to the control sample, with age-specific cognitive domain decline patterns, due to the cumulative effect of aging and psychosis on cognition. Further, larger, multicenter research should focus on establishing these results and designing relevant procognitive interventions.

Associations and Mediating Pathways Between Childhood Adversity and Risk of Dementia: A Cohort Study in the UK Biobank

BACKGROUND

While childhood adversity (CA) is known to be associated with multiple adverse outcomes, its link with dementia is an area with limited exploration and inconsistent agreement. The study aimed to examine the longitudinal associations of CA with incident all-cause dementia and to quantify the potential mediating pathways.

METHODS

Data from the UK Biobank. CA, encompassing neglect and abuse, was evaluated retrospectively by an online mental health questionnaire. Physical performance, psychological factors, lifestyles, and biological indicators assessed at baseline were considered potential mediators. Incident all-cause dementia was defined by International Classification of Diseases, Tenth Revision codes obtained through self-reported medical conditions, primary care, hospital admission, and death registrations. Cox proportional hazard models were applied to estimate the longitudinal associations. Mediation analyses were conducted on potential mediators to examine their contribution.

RESULTS

This cohort study comprised 150 152 nondemented individuals (mean [SD] age, 55.9 [7.7] years) at baseline (2006-2010). Compared to individuals who did not experience CA, those exposed to any CA exhibited a 30.0% higher risk of dementia (hazard ratio = 1.300, 95% confidence interval [CI]: 1.129-1.496). Each additional CA was associated with a 15.5% (95% CI: 8.8%-22.5%, pfor trend < .001) increased dementia risks. Depression, smoking, and low grip strength explained 8.7%, 2.4%, and 0.9% of the associations, respectively. Biomarkers involving inflammation, erythrocytes, liver, and kidney function mediated the associations by 0.6%-1.4%.

CONCLUSIONS

The study revealed the detrimental effects of CA on dementia and identified some potential mediators, namely depression, smoking, low grip strength, and several targeted biomarkers. In addition to calling more attention to CA, the findings underscore the importance of interventions targeting modifiable mediators in preventing dementia.

Aging, sex, metabolic and life experience factors: Contributions to neuro-inflammaging in Alzheimer's disease research

Alzheimer's disease (AD) is prevalent around the world, yet our understanding of the disease is still very limited. Recent work suggests that the cornerstone of AD may include the inflammation that accompanies it. Failure of a normal pro-inflammatory immune response to resolve may lead to persistent central inflammation that contributes to unsuccessful clearance of amyloid-beta plaques as they form, neuronal death, and ultimately cognitive decline. Individual metabolic, and dietary (lipid) profiles can differentially regulate this inflammatory process with aging, obesity, poor diet, early life stress and other inflammatory factors contributing to a greater risk of developing AD. Here, we integrate evidence for the interface between these factors, and how they contribute to a pro-inflammatory brain milieu. In particular, we discuss the importance of appropriate polyunsaturated fatty acids (PUFA) in the diet for the metabolism of specialised pro-resolving mediators (SPMs); raising the possibility for dietary strategies to improve AD outlook.

Nlrp6 protects from corticosterone-induced NSPC ferroptosis by modulating RIG-1/MAVS-mediated mitophagy

Hippocampal neural stem/progenitor cells (NSPCs) are highly vulnerable to different stress stimuli, resulting in adult neurogenesis decline and eventual cognitive defects. Our previous study demonstrated that NOD-like receptor family pyrin domain-containing 6 (Nlrp6) highly expressed in NSPCs played a critical role in sustaining hippocampal neurogenesis to resist stress-induced depression, but the underlying mechnistms are still unclear. Here, we found that Nlrp6 depletion led to cognitive defects and hippocampal NSPC loss in mice. RNA-sequencing analysis of the primary NSPCs revealed that Nlrp6 deficiency altered gene expression profiles of mitochondrial energy generation and ferroptotic process. Upon siNlrp6 transfection, as well as corticosterone (CORT) exposure, downregulation of Nlrp6 suppressed retinoic acid-inducible gene I (RIG-1)/mitochondrial antiviral signaling proteins (MAVS)-mediated autophagy, but drove NSPC ferroptotic death. More interesting, short chain fatty acids (SCFAs) upregulated Nlrp6 expression and promoted RIG-1/MAVS-mediated mitophagy, preventing CORT-induced NSPC ferroptosis. Our study further demonstrates that Nlrp6 should be a sensor for RIG-1/MAVS-mediated mitophagy and play a critical role in maintain mitochondrial homeostasis of hippocampal NSPCs. These results suggests that Nlrp6 should be a potential drug target to combat neurodegenerative diseases relative with chronic stress.

Cognitive function following early life war-time stress exposure in a cohort of Vietnamese older adults

Although Alzheimer's Disease is a leading cause of death in Vietnam and other post-conflict, low- and middle-income countries, aside from studies of veterans in western populations, research on war-related violence and deprivation as risk factors for cognitive disorders remains sparse. Using data from the Vietnam Health and Aging Study, which relied upon a multistage probability sample of 2447 older adults residing in districts of northern Vietnam differentially exposed to wartime bombing and numerous war-related stressors, this paper investigates associations between early-life war-related stressors and later-life cognitive function in a cohort whose transition to adulthood took place during the American-Vietnam War. Relationships among experiences of severe childhood hunger, war-related violence and environmental hardships, military service, and cognitive function in an analytical sample of 2162 Vietnamese older adults are estimated using quantile regression. Cognitive function is assessed by a modified Mini-Mental State Examination (MMSE) score. Analyses also address posttraumatic stress disorder (PTSD), cardiovascular health, and health behaviors as potential mediators between early life war-related stressors and current cognitive function. Results indicate that experiences of severe hunger in childhood and environmental hardships are associated with poorer cognitive function in older adulthood. PTSD, cardiovascular risk (i.e., hypertension) and disease (i.e., stroke), each of which is heightened by exposure to wartime stressors, are associated with lower cognitive scores. Results suggest that certain war exposures, like involvement in combat duties, are associated with higher cognitive function scores, suggesting that military service either positively selects for cognitive function, or certain forms of service may impart cognitive resilience. Following recent calls to incorporate population-specific stressors to advance explanatory models of cognitive function, these findings suggest that it is critical to assess the enduring scars and resilience of armed conflict in global efforts to understand, prevent, and treat cognitive impairment, Alzheimer's Disease, and related dementias.

Current perspectives on perinatal mental health and neurobehavioral development: focus on regulation, coregulation and self-regulation

PURPOSE OF REVIEW

Perinatal mental health research provides an important perspective on neurobehavioral development. Here, we aim to review the association of maternal perinatal health with offspring neurodevelopment, providing an update on (self-)regulation problems, hypothesized mechanistic pathways, progress and challenges, and implications for mental health.

RECENT FINDINGS

(1) Meta-analyses confirm that maternal perinatal mental distress is associated with (self-)regulation problems which constitute cognitive, behavioral, and affective social-emotional problems, while exposure to positive parental mental health has a positive impact. However, effect sizes are small. (2) Hypothesized mechanistic pathways underlying this association are complex. Interactive and compensatory mechanisms across developmental time are neglected topics. (3) Progress has been made in multiexposure studies. However, challenges remain and these are shared by clinical, translational and public health sciences. (4) From a mental healthcare perspective, a multidisciplinary and system level approach employing developmentally-sensitive measures and timely treatment of (self-)regulation and coregulation problems in a dyadic caregiver-child and family level approach seems needed. The existing evidence-base is sparse.

SUMMARY

During the perinatal period, addressing vulnerable contexts and building resilient systems may promote neurobehavioral development. A pluralistic approach to research, taking a multidisciplinary approach to theoretical models and empirical investigation needs to be fostered.

Pro-inflammatory cytokines in stress-induced depression: Novel insights into mechanisms and promising therapeutic strategies

Stress-mediated depression is one of the common psychiatric disorders with a high prevalence and suicide rate, there is a lack of effective treatment. Accordingly, effective treatments with few adverse effects are urgently needed. Pro-inflammatory cytokines (PICs) may play a key role in stress-mediated depression. Thereupon, both preclinical and clinical studies have found higher levels of IL-1β, TNF-α and IL-6 in peripheral blood and brain tissue of patients with depression. Recent studies have found PICs cause depression by affecting neuroinflammation, monoamine neurotransmitters, hypothalamic pituitary adrenal axis and neuroplasticity. Moreover, they play an important role in the symptom, development and progression of depression, maybe a potential diagnostic and therapeutic marker of depression. In addition, well-established antidepressant therapies have some relief on high levels of PICs. Importantly, anti-inflammatory drugs relieve depressive symptoms by reducing levels of PICs. Collectively, reducing PICs may represent a promising therapeutic strategy for depression.

Myelin Pathology in Alzheimer's Disease: Potential Therapeutic Opportunities

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by memory loss and cognitive decline. Despite significant efforts over several decades, our understanding of the pathophysiology of this disease is still incomplete. Myelin is a multi-layered membrane structure ensheathing neuronal axons, which is essential for the fast and effective propagation of action potentials along the axons. Recent studies highlight the critical involvement of myelin in memory consolidation and reveal its vulnerability in various pathological conditions. Notably, apart from the classic amyloid hypothesis, myelin degeneration has been proposed as another critical pathophysiological feature of AD, which could occur prior to the development of amyloid pathology. Here, we review recent works supporting the critical role of myelin in cognition and myelin pathology during AD progression, with a focus on the mechanisms underlying myelin degeneration in AD. We also discuss the complex intersections between myelin pathology and typical AD pathophysiology, as well as the therapeutic potential of pro-myelinating approaches for this disease. Overall, these findings implicate myelin degeneration as a critical contributor to AD-related cognitive deficits and support targeting myelin repair as a promising therapeutic strategy for AD.

A lifetime perspective on risk factors for cognitive decline with a special focus on early events

Both Alzheimer's disease and vascular dementia are the result of disease processes that typically develop over several decades. Population studies have estimated that more than half of the risk for dementia is preventable or at least modifiable through behavioral adaptations. The association between these lifestyle factors and the risk of dementia is most evident for exposure in midlife. However, habits formed in middle age often reflect a lifetime of behavior patterns and living conditions. Therefore, individuals who, for example, are able to maintain healthy diets and regular exercise during their middle years are likely to benefit from these cognition-protective habits they have practiced throughout their lives. For numerous adult diseases, significant risks can often be traced back to early childhood. Suboptimal conditions during the perinatal period, childhood and adolescence can increase the risk of adult diseases, including stroke, heart disease, insulin resistance, hypertension and dementia. This review aims at summarizing some of the evidence for dementia risks from a life-time perspective with the goal of raising awareness for early dementia prevention and successful aging.

Unlocking therapeutic potential: computational insights into TREM2 protein targeting with FDA-approved drugs for neurodegeneration

Neurodegenerative diseases such as Alzheimer's disease (AD) pose a significant global health challenge that requires the exploration of innovative therapeutic strategies. Triggering receptor expressed on myeloid cells-2 (TREM2) is one of the critical proteins involved in immune regulation and neuroinflammation. It has emerged as a promising therapeutic target to develop treatments for neurodegenerative disorders like AD. Here, we employed a comprehensive virtual screening approach to identify potential small molecule inhibitors among FDA-approved drugs for TREM2. The docking study reveals significant binding affinity, ranging from -7.8 kcal/mol to -8.5 kcal/mol, for the elucidated hits against TREM2, accompanied by several crucial interactions. Among the repurposed drugs identified in the initial screening, Carpipramine, Clocapramine, and Pimozide stood out due to their notable binding potential and favorable drug profiling. Further, we conducted molecular dynamics (MD) simulations on the selected molecules that probed their structural dynamics and stability within the TREM2 binding pocket. The structural parameters and hydrogen bond dynamics remained remarkably stable throughout the simulated trajectories. Furthermore, we performed principal component analysis (PCA) and constructed free energy landscapes (FELs) to gain deeper insights into ligand binding and conformational flexibility of TREM2. The findings revealed that the elucidated molecules, Carpipramine, Clocapramine, and Pimozide, exhibited an exceptional fit within the binding pocket of TREM2 with remarkable stability and interaction patterns throughout the 500 ns simulation window. Interestingly, these molecules possessed a spectrum of anti-neurodegenerative properties and favorable drug profiles, which suggest their potential as promising drug candidates for repurposing in the treatment of AD.Communicated by Ramaswamy H. Sarma.

Hydrogen peroxide in breast milk is crucial for gut microbiota formation and myelin development in neonatal mice

Early life environment influences mammalian brain development, a growing area of research within the Developmental Origins of Health and Disease framework, necessitating a deeper understanding of early life factors on children's brain development. This study introduces a mouse model, LAO1 knockout mice, to investigate the relationship between breast milk, the gut microbiome, and brain development. The results reveal that breast milk's reactive oxygen species (ROS) are vital in shaping the neonatal gut microbiota. Decreased hydrogen peroxide (H2O2) levels in milk disrupt the gut microbiome and lead to abnormal metabolite production, including D-glucaric acid. This metabolite inhibits hippocampal myelin formation during infancy, potentially contributing to behavioral abnormalities observed in adulthood. These findings suggest that H2O2 in breast milk is crucial for normal gut microbiota formation and brain development, with implications for understanding and potentially treating neurodevelopmental disorders in humans.

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.

Postnatal Maturation of the Blood-Brain Barrier in Senescence-Accelerated OXYS Rats, Which Are Prone to an Alzheimer's Disease-like Pathology

Alzheimer's disease (AD) is an old-age neurodegenerative disorder; however, AD predisposition may arise early in life. Vascular dysfunction makes a big contribution to AD development. Nonetheless, the possible role of early-life vascular dysfunction in AD development is still poorly investigated. Here, using OXYS rats as a suitable model of the most common (sporadic) type of AD, we investigated maturation of the blood-brain barrier (BBB) in the hippocampus and frontal cortex in the first 3 weeks of life. Using RNA-Seq data, we found an altered expression of BBB-associated genes in the middle of the first and second weeks of life in OXYS rats compared to control rats (Wistar strain). Moreover, by immunohistochemistry and electronic microscopy, we revealed a delay of vascularization and of subsequent pericyte coating of blood vessels in OXYS rats. These specific features were accompanied by an accelerated decrease in BBB permeability estimated using Evans blue dye. Notably, almost all of the observed differences from Wistar rats disappeared on postnatal day 20. Nonetheless, the observed features, which are characteristic of the postnatal period, may have long-term consequences and contribute to neurovascular dysfunction observed in OXYS rats late in life, thereby promoting early development of AD signs.

Paving the Way for Alzheimer's Disease Prevention: A Systematic Review of Global Open-Access Neuroimaging Datasets in Healthy Individuals

BACKGROUND

Given the advent of large-scale neuroimaging data-driven endeavors for Alzheimer's disease, there is a burgeoning need for well-characterized neuroimaging databases of healthy individuals. With the rise of initiatives around the globe for the rapid and unrestricted sharing of data resources, there is now an abundance of open-source neuroimaging datasets available to the research community. However, there is not yet a systematic review that fully details the demographic information and modalities actually available in all open access neuroimaging databases around the globe.

OBJECTIVE

This systematic review aims to provide compile a list of MR structural imaging databases encompassing healthy individuals across the lifespan.

METHODS

In this systematic review, we searched EMBASE and PubMed until May 2022 for open-access neuroimaging databases containing healthy control participants of any age, race, with normal development and cognition having at least one structural T1-weighted neuroimaging scan.

RESULTS

A total of 403 databases were included, for up to total of 48,268 participants with all available demographic information and imaging modalities detailed in Supplementary Table 1. There were significant trends noted when compiling normative databases for this systematic review, notably that 11.7% of databases included reported ethnicity in their participants, with underrepresentation of many socioeconomic groups globally.

CONCLUSIONS

As efforts to improve primary prevention of AD may require a broader perspective including increased relevance of earlier stages in life, and strategies in addressing modifiable risk factors may be individualized to specific demographics, improving data characterization to be richer and more rigorous will greatly enhance these efforts.