Sleep Deprivation Affects Tau Phosphorylation in Human Cerebrospinal Fluid

Relationship between sleep, physical fitness, brain microstructure, and cognition in healthy older adults: A pilot study

BACKGROUND

There is a critical need for neuroimaging markers of brain integrity to monitor effects of modifiable lifestyle factors on brain health. This observational, cross-sectional study assessed relationships between brain microstructure and sleep, physical fitness, and cognition in healthy older adults.

METHODS

Twenty-three adults aged 60 and older underwent whole-brain multi-shell diffusion imaging, comprehensive cognitive testing, polysomnography, and exercise testing. Neurite Orientation Dispersion and Density Imaging (NODDI) was used to quantify neurite density (NDI) and orientation dispersion (ODI). Diffusion tensor imaging (DTI) was used to quantify axial diffusivity (AxD), fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD). Relationships between sleep efficiency (SE), time and percent in N3 sleep, cognitive function, physical fitness (VO2 peak) and the diffusion metrics in regions of interest and the whole brain were evaluated.

RESULTS

Higher NDI in bilateral white and gray matter was associated with better executive functioning. NDI in the right anterior cingulate and adjacent white matter was positively associated with language skills. Higher NDI in the left posterior corona radiata was associated with faster processing speed. Physical fitness was positively associated with NDI in the left precentral gyrus and corticospinal tract. N3 % was positively associated with NDI in the left caudate and right pre- and postcentral gyri. Higher ODI in the left putamen and adjacent white matter was associated with better executive function.

CONCLUSION

NDI and ODI derived from NODDI are potential neuroimaging markers for associations between brain microstructure and modifiable risk factors in aging. If these associations are observable in clinical samples, NODDI could be incorporated into clinical trials assessing the effects of modifiable risk factors on brain integrity in aging and neurodegenerative diseases.

A bibliometric analysis on the health behaviors related to mild cognitive impairment

Background

Mild cognitive impairment (MCI) is commonly defined as a transitional subclinical state between normal aging and dementia. A growing body of research indicates that health behaviors may play a protective role against cognitive decline and could potentially slow down the progression from MCI to dementia. The aim of this study is to conduct a bibliometric analysis of literature focusing on health behaviors and MCI to summarize the factors and evidence regarding the influence of health behaviors on MCI.

Methods

The study performed a bibliometric analysis by retrieving publications from the Science Citation Index and Social Sciences Citation Index sub-databases within the Web of Science Core Collection. Utilizing VOSviewer and CiteSpace software, a total of 2,843 eligible articles underwent co-citation, co-keywords, and clustering analyses. This methodology aimed to investigate the current status, trends, major research questions, and potential future directions within the research domain.

Results

The bibliometric analysis indicates that research on healthy behaviors in individuals with MCI originated in 2002 and experienced rapid growth in 2014, reflecting the increasing global interest in this area. The United States emerged as the primary contributor, accounting for more than one-third of the total scientific output with 982 articles. Journals that published the most articles on MCI-related health behaviors included "Journal of Alzheimer's Disease," "Neurobiology of Aging," "Frontiers in Aging Neuroscience," and other geriatrics-related journals. High-impact papers identified by VOSviewer predominantly cover concepts related to MCI, such as diagnostic criteria, assessment, and multifactorial interventions. Co-occurrence keyword analysis highlights five research hotspots in health behavior associated with MCI: exercise, diet, risk factors and preventive measures for dementia, cognitive decline-related biomarkers, and clinical trials.

Conclusion

This study provides a comprehensive review of literature on health behavior in individuals with MCI, emphasizing influential documents and journals. It outlines research trends and key focal points, offering valuable insights for researchers to comprehend significant contributions and steer future studies.

Exploring the potential relationship between short sleep risks and cognitive function from the perspective of inflammatory biomarkers and cellular pathways: Insights from population-based and mice studies

AIMS

The molecular mechanism of short-sleep conditions on cognition remains largely unknown. This research aimed to investigate associations between short sleep, inflammatory biomarkers and cognitive function in the US population (NHANES data 2011-2014) and explore cellular mechanisms in mice.

METHODS

Systemic immune-inflammation index (SII) was calculated using blood-cell based biomarkers. Further, we employed integrated bioinformatics and single-cell transcriptomics (GSE137665) to examine how short sleep exposure influenced the molecular pathways associated with inflammation in the brain. To explore the signaling pathways and biological processes of sleep deprivation, we carried out enrichment analyses utilizing the GO and KEGG databases.

RESULTS

Population results showed that, compared with normal sleep group, severe short sleep was associated with lower cognitive ability in all the four tests. Moreover, a higher SII level was correlated with lower scores of cognitive tests. In mice study, elevated activation of the inflammatory pathway was observed in cell subgroups of neurons within the sleep deprivation and recovery sleep cohorts. Additionally, heightened expression of oxidative stress and integrated stress response pathways was noted in GABAergic neurons during sleep deprivation.

CONCLUSION

This study contributed to the understanding of the influence of short sleep on cognitive function and its cellular mechanisms.

Tau Aggregation-Dependent Lipid Peroxide Accumulation Driven by the hsa_circ_0001546/14-3-3/CAMK2D/Tau Complex Inhibits Epithelial Ovarian Cancer Peritoneal Metastasis

Intraperitoneal dissemination is the main method of epithelial ovarian cancer (EOC) metastasis, which is related to poor prognosis and a high recurrence rate. Circular RNAs (circRNAs) are a novel class of endogenous RNAs with covalently closed loop structures that are implicated in the regulation of tumor development. In this study, hsa_circ_0001546 is downregulated in EOC primary and metastatic tissues vs. control tissues and this phenotype has a favorable effect on EOC OS and DFS. hsa_circ_0001546 can directly bind with 14-3-3 proteins to act as a chaperone molecule and has a limited positive effect on 14-3-3 protein stability. This complex recruits CAMK2D to induce the Ser324 phosphorylation of Tau proteins, changing the phosphorylation status of Tau bound to 14-3-3 and ultimately forming the hsa_circ_0001546/14-3-3/CAMK2D/Tau complex. The existence of this complex stimulates the production of Tau aggregation, which then induces the accumulation of lipid peroxides (LPOs) and causes LPO-dependent ferroptosis. In vivo, treatment with ferrostatin-1 and TRx0237 rescued the inhibitory effect of hsa_circ_0001546 on EOC cell spreading. Therefore, based on this results, ferroptosis caused by Tau aggregation occurs in EOC cells, which is not only in Alzheimer's disease- or Parkinson's disease-related cells and this kind of ferroptosis driven by the hsa_circ_0001546/14-3-3/CAMK2D/Tau complex is LPO-dependent rather than GPX4-dependent is hypothesized.

Remote Evaluation of Sleep and Circadian Rhythms in Older Adults With Mild Cognitive Impairment and Dementia: Protocol for a Feasibility and Acceptability Mixed Methods Study

BACKGROUND

Sleep disturbances are a potentially modifiable risk factor for neurodegenerative dementia secondary to Alzheimer disease (AD) and Lewy body disease (LBD). Therefore, we need to identify the best methods to study sleep in this population.

OBJECTIVE

This study will assess the feasibility and acceptability of various wearable devices, smart devices, and remote study tasks in sleep and cognition research for people with AD and LBD.

METHODS

We will deliver a feasibility and acceptability study alongside a prospective observational cohort study assessing sleep and cognition longitudinally in the home environment. Adults aged older than 50 years who were diagnosed with mild to moderate dementia or mild cognitive impairment (MCI) due to probable AD or LBD and age-matched controls will be eligible. Exclusion criteria include lack of capacity to consent to research, other causes of MCI or dementia, and clinically significant sleep disorders. Participants will complete a cognitive assessment and questionnaires with a researcher and receive training and instructions for at-home study tasks across 8 weeks. At-home study tasks include remote sleep assessments using wearable devices (electroencephalography headband and actigraphy watch), app-based sleep diaries, online cognitive assessments, and saliva samples for melatonin- and cortisol-derived circadian markers. Feasibility outcomes will be assessed relating to recruitment and retention, data completeness, data quality, and support required. Feedback on acceptability and usability will be collected throughout the study period and end-of-study interviews will be analyzed using thematic analysis.

RESULTS

Recruitment started in February 2022. Data collection is ongoing, with final data expected in February 2024 and data analysis and publication of findings scheduled for the summer of 2024.

CONCLUSIONS

This study will allow us to assess if remote testing using smart devices and wearable technology is a viable alternative to traditional sleep measurements, such as polysomnography and questionnaires, in older adults with and without MCI or dementia due to AD or LBD. Understanding participant experience and the barriers and facilitators to technology use for research purposes and remote research in this population will assist with the development of, recruitment to, and retention within future research projects studying sleep and cognition outside of the clinic or laboratory.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/52652.

Associations of sleep disorders with all-cause MCI/dementia and different types of dementia - clinical evidence, potential pathomechanisms and treatment options: A narrative review

Due to worldwide demographic change, the number of older persons in the population is increasing. Aging is accompanied by changes of sleep structure, deposition of beta-amyloid (Aß) and tau proteins and vascular changes and can turn into mild cognitive impairment (MCI) as well as dementia. Sleep disorders are discussed both as a risk factor for and as a consequence of MCI/dementia. Cross-sectional and longitudinal population-based as well as case-control studies revealed sleep disorders, especially sleep-disorderded breathing (SDB) and excessive or insufficient sleep durations, as risk factors for all-cause MCI/dementia. Regarding different dementia types, SDB was especially associated with vascular dementia while insomnia/insufficient sleep was related to an increased risk of Alzheimer's disease (AD). Scarce and still inconsistent evidence suggests that therapy of sleep disorders, especially continuous positive airway pressure (CPAP) in SDB, can improve cognition in patients with sleep disorders with and without comorbid dementia and delay onset of MCI/dementia in patients with sleep disorders without previous cognitive impairment. Regarding potential pathomechanisms via which sleep disorders lead to MCI/dementia, disturbed sleep, chronic sleep deficit and SDB can impair glymphatic clearance of beta-amyloid (Aß) and tau which lead to amyloid deposition and tau aggregation resulting in changes of brain structures responsible for cognition. Orexins are discussed to modulate sleep and Aß pathology. Their diurnal fluctuation is suppressed by sleep fragmentation and the expression suppressed at the point of hippocampal atrophy, contributing to the progression of dementia. Additionally, sleep disorders can lead to an increased vascular risk profile and vascular changes such as inflammation, endothelial dysfunction and atherosclerosis which can foster neurodegenerative pathology. There is ample evidence indicating that changes of sleep structure in aging persons can lead to dementia and also evidence that therapy of sleep disorder can improve cognition. Therefore, sleep disorders should be identified and treated early.

Circadian regulation of microglia function: Potential targets for treatment of Parkinson's Disease

Circadian rhythms are involved in the regulation of many aspects of the body, including cell function, physical activity and disease. Circadian disturbance often predates the typical symptoms of neurodegenerative diseases and is not only a non-motor symptom, but also one of the causes of their occurrence and progression. Glial cells possess circadian clocks that regulate their function to maintain brain development and homeostasis. Emerging evidence suggests that the microglial circadian clock is involved in the regulation of many physiological processes, such as cytokine release, phagocytosis, and nutritional and metabolic support, and that disruption of the microglia clock may affect multiple aspects of Parkinson's disease, especially neuroinflammation and α-synuclein processes. Herein, we review recent advances in the circadian control of microglia function in health and disease, and discuss novel pharmacological interventions for microglial clocks in neurodegenerative disorders.

Impact of Sleep Disorders and Disturbed Sleep on Brain Health: A Scientific Statement From the American Heart Association

Accumulating evidence supports a link between sleep disorders, disturbed sleep, and adverse brain health, ranging from stroke to subclinical cerebrovascular disease to cognitive outcomes, including the development of Alzheimer disease and Alzheimer disease-related dementias. Sleep disorders such as sleep-disordered breathing (eg, obstructive sleep apnea), and other sleep disturbances, as well, some of which are also considered sleep disorders (eg, insomnia, sleep fragmentation, circadian rhythm disorders, and extreme sleep duration), have been associated with adverse brain health. Understanding the causal role of sleep disorders and disturbances in the development of adverse brain health is complicated by the common development of sleep disorders among individuals with neurodegenerative disease. In addition to the role of sleep disorders in stroke and cerebrovascular injury, mechanistic hypotheses linking sleep with brain health and biomarker data (blood-based, cerebrospinal fluid-based, and imaging) suggest direct links to Alzheimer disease-specific pathology. These potential mechanisms and the increasing understanding of the "glymphatic system," and the recognition of the importance of sleep in poststroke recovery, as well, support a biological basis for the indirect (through the worsening of vascular disease) and direct (through specific effects on neuropathology) connections between sleep disorders and brain health. Given promising evidence for the benefits of treatment and prevention, sleep disorders and disturbances represent potential targets for early treatment that may improve brain health more broadly. In this scientific statement, we discuss the evidence supporting an association between sleep disorders and disturbances and poor brain health ranging from stroke to dementia and opportunities for prevention and early treatment.

Role of sleep in neurodegeneration: the consensus report of the 5th Think Tank World Sleep Forum

Sleep abnormalities may represent an independent risk factor for neurodegeneration. An international expert group convened in 2021 to discuss the state-of-the-science in this domain. The present article summarizes the presentations and discussions concerning the importance of a strategy for studying sleep- and circadian-related interventions for early detection and prevention of neurodegenerative diseases. An international expert group considered the current state of knowledge based on the most relevant publications in the previous 5 years; discussed the current challenges in the field of relationships among sleep, sleep disorders, and neurodegeneration; and identified future priorities. Sleep efficiency and slow wave activity during non-rapid eye movement (NREM) sleep are decreased in cognitively normal middle-aged and older adults with Alzheimer's disease (AD) pathology. Sleep deprivation increases amyloid-β (Aβ) concentrations in the interstitial fluid of experimental animal models and in cerebrospinal fluid in humans, while increased sleep decreases Aβ. Obstructive sleep apnea (OSA) is a risk factor for dementia. Studies indicate that positive airway pressure (PAP) treatment should be started in patients with mild cognitive impairment or AD and comorbid OSA. Identification of other measures of nocturnal hypoxia and sleep fragmentation could better clarify the role of OSA as a risk factor for neurodegeneration. Concerning REM sleep behavior disorder (RBD), it will be crucial to identify the subset of RBD patients who will convert to a specific neurodegenerative disorder. Circadian sleep-wake rhythm disorders (CSWRD) are strong predictors of caregiver stress and institutionalization, but the absence of recommendations or consensus statements must be considered. Future priorities include to develop and validate existing and novel comprehensive assessments of CSWRD in patients with/at risk for dementia. Strategies for studying sleep-circadian-related interventions for early detection/prevention of neurodegenerative diseases are required. CSWRD evaluation may help to identify additional biomarkers for phenotyping and personalizing treatment of neurodegeneration.

Orexin Receptor Antagonism: Normalizing Sleep Architecture in Old Age and Disease

Sleep is essential for human well-being, yet the quality and quantity of sleep reduce as age advances. Older persons (>65 years old) are more at risk of disorders accompanied and/or exacerbated by poor sleep. Furthermore, evidence supports a bidirectional relationship between disrupted sleep and Alzheimer's disease (AD) or related dementias. Orexin/hypocretin neuropeptides stabilize wakefulness, and several orexin receptor antagonists (ORAs) are approved for the treatment of insomnia in adults. Dysregulation of the orexin system occurs in aging and AD, positioning ORAs as advantageous for these populations. Indeed, several clinical studies indicate that ORAs are efficacious hypnotics in older persons and dementia patients and, as in adults, are generally well tolerated. ORAs are likely to be more effective when administered early in sleep/wake dysregulation to reestablish good sleep/wake-related behaviors and reduce the accumulation of dementia-associated proteinopathic substrates. Improving sleep in aging and dementia represents a tremendous opportunity to benefit patients, caregivers, and health systems.

Tau, ADNP, and sex

With 50 years to the original discovery of Tau, I gave here my perspective, looking through the prism of activity-dependent neuroprotective protein (ADNP), and the influence of sex. My starting point was vasoactive intestinal peptide (VIP), a regulator of ADNP. I then moved to the original discovery of ADNP and its active neuroprotective site, NAP, drug candidate, davunetide. Tau-ADNP-NAP interactions were then explained with emphasis on sex and future translational medicine.

Association of Sleep Disturbances With Brain Amyloid and Tau Burden, Cortical Atrophy, and Cognitive Dysfunction Across the AD Continuum

BACKGROUND AND OBJECTIVES

Patients with Alzheimer disease (AD) frequently suffer from various sleep disturbances. However, how sleep disturbance is associated with AD and its progression remains poorly investigated. We investigated the association of total sleep time with brain amyloid and tau burden, cortical atrophy, cognitive dysfunction, and their longitudinal changes in the AD spectrum.

METHODS

In this retrospective cohort study, we enrolled participants on the AD spectrum who were positive on 18F-florbetaben (FBB) PET. All participants underwent the Pittsburgh Sleep Quality Index, brain MRI, FBB PET, 18F-flortaucipir (FTP) PET, and detailed neuropsychological testing. In addition, a subset of participants completed follow-up assessments. We analyzed the association of total sleep time with the baseline and longitudinal FBB-standardized uptake value ratio (SUVR), FTP-SUVR, cortical thickness, and cognitive domain composite scores.

RESULTS

We examined 138 participants on the AD spectrum (15 with preclinical AD, 62 with prodromal AD, and 61 with AD dementia; mean age 73.4 ± 8.0 years; female 58.7%). Total sleep time was longer in the AD dementia group (7.4 ± 1.6 hours) compared with the preclinical (6.5 ± 1.4 hours; p = 0.026) and prodromal groups (6.6 ± 1.4 hours; p = 0.001), whereas other sleep parameters did not differ between groups. Longer total sleep time was not associated with amyloid accumulation but rather with tau accumulation, especially in the amygdala, hippocampus, basal forebrain, insular, cingulate, occipital, inferior temporal cortices, and precuneus. Longer total sleep time predicted faster tau accumulation in Braak regions V-VI (β = 0.016, p = 0.007) and disease progression to mild cognitive impairment or dementia (hazard ratio = 1.554, p = 0.024). Longer total sleep time was also associated with memory deficit (β = -0.19, p = 0.008).

DISCUSSION

Prolonged total sleep time was associated with tau accumulation in sleep-related cortical and subcortical areas as well as memory dysfunction. It also predicted faster disease progression with tau accumulation. Our study highlights the clinical importance of assessing total sleep time as a marker for disease severity and prognosis in the AD spectrum.

Plasma and cerebrospinal fluid proteomic signatures of acutely sleep-deprived humans: an exploratory study

Study Objectives

Acute sleep deprivation affects both central and peripheral biological processes. Prior research has mainly focused on specific proteins or biological pathways that are dysregulated in the setting of sustained wakefulness. This exploratory study aimed to provide a comprehensive view of the biological processes and proteins impacted by acute sleep deprivation in both plasma and cerebrospinal fluid (CSF).

Methods

We collected plasma and CSF from human participants during one night of sleep deprivation and controlled normal sleep conditions. One thousand and three hundred proteins were measured at hour 0 and hour 24 using a high-scale aptamer-based proteomics platform (SOMAscan) and a systematic biological database tool (Metascape) was used to reveal altered biological pathways.

Results

Acute sleep deprivation decreased the number of upregulated and downregulated biological pathways and proteins in plasma but increased upregulated and downregulated biological pathways and proteins in CSF. Predominantly affected proteins and pathways were associated with immune response, inflammation, phosphorylation, membrane signaling, cell-cell adhesion, and extracellular matrix organization.

Conclusions

The identified modifications across biofluids add to evidence that acute sleep deprivation has important impacts on biological pathways and proteins that can negatively affect human health. As a hypothesis-driving study, these findings may help with the exploration of novel mechanisms that mediate sleep loss and associated conditions, drive the discovery of new sleep loss biomarkers, and ultimately aid in the identification of new targets for intervention to human diseases.

Sleep disturbances as risk factors for neurodegeneration later in life

The relationship between sleep disorders and neurodegeneration is complex and multi-faceted. Using over one million electronic health records (EHRs) from Wales, UK, and Finland, we mined biobank data to identify the relationships between sleep disorders and the subsequent manifestation of neurodegenerative diseases (NDDs) later in life. We then examined how these sleep disorders' severity impacts neurodegeneration risk. Additionally, we investigated how sleep attributed risk may compensate for the lack of genetic risk factors (i.e. a lower polygenic risk score) in NDD manifestation. We found that sleep disorders such as sleep apnea were associated with the risk of Alzheimer's disease (AD), amyotrophic lateral sclerosis, dementia, Parkinson's disease (PD), and vascular dementia in three national scale biobanks, with hazard ratios (HRs) ranging from 1.31 for PD to 5.11 for dementia. These sleep disorders imparted significant risk up to 15 years before the onset of an NDD. Cumulative number of sleep disorders in the EHRs were associated with a higher risk of neurodegeneration for dementia and vascular dementia. Sleep related risk factors were independent of genetic risk for Alzheimer's and Parkinson's, potentially compensating for low genetic risk in overall disease etiology. There is a significant multiplicative interaction regarding the combined risk of sleep disorders and Parkinson's disease. Poor sleep hygiene and sleep apnea are relatively modifiable risk factors with several treatment options, including CPAP and surgery, that could potentially reduce the risk of neurodegeneration. This is particularly interesting in how sleep related risk factors are significantly and independently enriched in manifesting NDD patients with low levels of genetic risk factors for these diseases.

HIGHLIGHTS

Sleep disorders, particularly sleep apnea, are associated with the risk of Alzheimer's disease, amyotrophic lateral sclerosis, dementia, Parkinson's disease, and vascular dementia in national scale biobanks.These sleep disorders imparted significant risk up to 15 years before the onset of a neurodegenerative disease.The cumulative number of sleep disorders in the electronic health records were associated with a higher risk of neurodegeneration related to dementia and vascular dementia.Sleep related risk factors are independent of genetic risk for Alzheimer's and Parkinson's, potentially compensating for low genetic risk in overall disease etiology.Significant multiplicative interaction exists regarding the combined risk of sleep disorders and Parkinson's disease.

Plasma Aβ level alterations after sleep deprivation correspond to brain structural remodeling in medical night shift workers

The relationship between brain structure alteration and metabolic product clearance after night shift work with total sleep deprivation (SD) remains unclear. Twenty-two intensive care unit staff on regularly rotating shift work were implemented with structural and diffusion MRI under both rest wakefulness (RW) and SD conditions. Peripheral blood samples were collected for the measurement of cerebral metabolites. Voxel-based morphometry and diffusion tensor imaging analysis were used to investigate the alterations in the gray matter density (GMD) and mean diffusivity (MD) within the participants. Furthermore, correlation analysis was performed to investigate the relationship between the neuroimaging metrics and hematological parameters. A significant increase in the GMD values was observed in the anterior and peripheral areas of the brain under SD. In contrast, a decrease in the values was observed in the posterior regions, such as the bilateral cerebellum and thalamus. In addition, a significant reduction in the total cerebrospinal fluid volume was observed under SD. The Aβ42/Aβ40 levels in participants under SD were significantly lower than those under RW. The mean MD increment values extracted from the region of interest (ROI) of the anterior brain were negatively correlated with the increment of plasma Aβ42/Aβ40 levels (r = -0.658, P = 0.008). The mean GMD decrement values extracted from the posterior ROI were positively correlated with the increment of plasma Aβ-40 levels (r = 0.601, P = 0.023). The findings of this study suggest that one night of shift work under SD induces extensive and direction-specific structural alterations of the brain, which are associated with aberrant brain metabolic waste clearance.

Sleep deprivation enhances amyloid beta peptide, p-tau and serotonin in the brain: Neuroprotective effects of nanowired delivery of cerebrolysin with monoclonal antibodies to amyloid beta peptide, p-tau and serotonin

Sleep deprivation is quite frequent in military during combat, intelligence gathering or peacekeeping operations. Even one night of sleep deprivation leads to accumulation of amyloid beta peptide burden that would lead to precipitation of Alzheimer's disease over the years. Thus, efforts are needed to slow down or neutralize accumulation of amyloid beta peptide (AβP) and associated Alzheimer's disease brain pathology including phosphorylated tau (p-tau) within the brain fluid environment. Sleep deprivation also alters serotonin (5-hydroxytryptamine) metabolism in the brain microenvironment and impair upregulation of several neurotrophic factors. Thus, blockade or neutralization of AβP, p-tau and serotonin in sleep deprivation may attenuate brain pathology. In this investigation this hypothesis is examined using nanodelivery of cerebrolysin- a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies against AβP, p-tau and serotonin (5-hydroxytryptamine, 5-HT). Our observations suggest that sleep deprivation induced pathophysiology is significantly reduced following nanodelivery of cerebrolysin together with monoclonal antibodies to AβP, p-tau and 5-HT, not reported earlier.

Noradrenergic neuromodulation in ageing and disease

The locus coeruleus (LC) is a small brainstem structure located in the lower pons and is the main source of noradrenaline (NA) in the brain. Via its phasic and tonic firing, it modulates cognition and autonomic functions and is involved in the brain's immune response. The extent of degeneration to the LC in healthy ageing remains unclear, however, noradrenergic dysfunction may contribute to the pathogenesis of Alzheimer's (AD) and Parkinson's disease (PD). Despite their differences in progression at later disease stages, the early involvement of the LC may lead to comparable behavioural symptoms such as preclinical sleep problems and neuropsychiatric symptoms as a result of AD and PD pathology. In this review, we draw attention to the mechanisms that underlie LC degeneration in ageing, AD and PD. We aim to motivate future research to investigate how early degeneration of the noradrenergic system may play a pivotal role in the pathogenesis of AD and PD which may also be relevant to other neurodegenerative diseases.

Acute sleep loss decreases CSF-to-blood clearance of Alzheimer's disease biomarkers

INTRODUCTION

Sleep deprivation increases cerebrospinal fluid (CSF) amyloid beta (Aβ) and tau levels; however, sleep's effect on Aβ and tau in plasma is unknown.

METHODS

In a cross-over design, CSF Aβ and tau concentrations were measured in five cognitively normal individuals who had blood and CSF collected every 2 hours for 36 hours during sleep-deprived and normal sleep control conditions.

RESULTS

Aβ40, Aβ42, unphosphorylated tau threonine181 (T181), unphosphorylated tau threonine-217 (T217), and phosphorylated T181 (pT181) concentrations increased ∼35% to 55% in CSF and decreased ∼5% to 15% in plasma during sleep deprivation. CSF/plasma ratios of all Alzheimer's disease (AD) biomarkers increased during sleep deprivation while the CSF/plasma albumin ratio, a measure of blood-CSF barrier permeability, decreased. CSF and plasma Aβ42/40, pT181/T181, and pT181/Aβ42 ratios were stable longitudinally in both groups.

DISCUSSION

These findings show that sleep loss alters some plasma AD biomarkers by lowering brain clearance mechanisms and needs to be taken into account when interpreting individual plasma AD biomarkers but not ratios.

Role of astrocytes in sleep deprivation: accomplices, resisters, or bystanders?

Sleep plays an essential role in all studied animals with a nervous system. However, sleep deprivation leads to various pathological changes and neurobehavioral problems. Astrocytes are the most abundant cells in the brain and are involved in various important functions, including neurotransmitter and ion homeostasis, synaptic and neuronal modulation, and blood-brain barrier maintenance; furthermore, they are associated with numerous neurodegenerative diseases, pain, and mood disorders. Moreover, astrocytes are increasingly being recognized as vital contributors to the regulation of sleep-wake cycles, both locally and in specific neural circuits. In this review, we begin by describing the role of astrocytes in regulating sleep and circadian rhythms, focusing on: (i) neuronal activity; (ii) metabolism; (iii) the glymphatic system; (iv) neuroinflammation; and (v) astrocyte-microglia cross-talk. Moreover, we review the role of astrocytes in sleep deprivation comorbidities and sleep deprivation-related brain disorders. Finally, we discuss potential interventions targeting astrocytes to prevent or treat sleep deprivation-related brain disorders. Pursuing these questions would pave the way for a deeper understanding of the cellular and neural mechanisms underlying sleep deprivation-comorbid brain disorders.

Molecular mechanisms and therapeutic potential of icariin in the treatment of Alzheimer's disease

BACKGROUND

Icariin (ICA) is the main active component of Epimedium, a traditional Chinese medicine (TCM), known to enhance cognitive function in Alzheimer's disease (AD). This study aims to investigate and summarize the mechanisms through which ICA treats AD.

METHODS

The PubMed and CNKI databases were utilized to review the advancements in ICA's role in AD prevention and treatment by analyzing literature published between January 2005 and April 2023. To further illustrate ICA's impact on AD development, tables, and images are included to summarize the relationships between various mechanisms.

RESULTS

The study reveals that ICA ameliorates cognitive deficits in AD model mice by modulating Aβ via multiple pathways, including BACE-1, NO/cGMP, Wnt/Ca²⁺, and PI3K/Akt signaling. ICA exhibits neuroprotective properties by inhibiting neuronal apoptosis through the suppression of ER stress in AD mice, potentially linked to NF-κB, MAPK, ERK, and PERK/Eif2α signaling pathways. Moreover, ICA may safeguard neurons by attenuating mitochondrial oxidative stress injury. ICA can also enhance learning, memory, and cognition by improving synaptic structure via regulation of the PSD-95 protein. Furthermore, ICA can mitigate neuroinflammation by inactivating microglial activity through the upregulation of PPARγ, TAK1/IKK/NF-κB, and JNK/p38 MAPK signaling pathways.

CONCLUSION

This study indicates that ICA possesses multiple beneficial effects in AD treatment. Through the integration of pharmacological and molecular biological research, ICA may emerge as a promising candidate to expedite the advancement of TCM in the clinical management of AD.

Proteostasis failure exacerbates neuronal circuit dysfunction and sleep impairments in Alzheimer's disease

Failed proteostasis is a well-documented feature of Alzheimer's disease, particularly, reduced protein degradation and clearance. However, the contribution of failed proteostasis to neuronal circuit dysfunction is an emerging concept in neurodegenerative research and will prove critical in understanding cognitive decline. Our objective is to convey Alzheimer's disease progression with the growing evidence for a bidirectional relationship of sleep disruption and proteostasis failure. Proteostasis dysfunction and tauopathy in Alzheimer's disease disrupts neurons that regulate the sleep-wake cycle, which presents behavior as impaired slow wave and rapid eye movement sleep patterns. Subsequent sleep loss further impairs protein clearance. Sleep loss is a defined feature seen early in many neurodegenerative disorders and contributes to memory impairments in Alzheimer's disease. Canonical pathological hallmarks, β-amyloid, and tau, directly disrupt sleep, and neurodegeneration of locus coeruleus, hippocampal and hypothalamic neurons from tau proteinopathy causes disruption of the neuronal circuitry of sleep. Acting in a positive-feedback-loop, sleep loss and circadian rhythm disruption then increase spread of β-amyloid and tau, through impairments of proteasome, autophagy, unfolded protein response and glymphatic clearance. This phenomenon extends beyond β-amyloid and tau, with interactions of sleep impairment with the homeostasis of TDP-43, α-synuclein, FUS, and huntingtin proteins, implicating sleep loss as an important consideration in an array of neurodegenerative diseases and in cases of mixed neuropathology. Critically, the dynamics of this interaction in the neurodegenerative environment are not fully elucidated and are deserving of further discussion and research. Finally, we propose sleep-enhancing therapeutics as potential interventions for promoting healthy proteostasis, including β-amyloid and tau clearance, mechanistically linking these processes. With further clinical and preclinical research, we propose this dynamic interaction as a diagnostic and therapeutic framework, informing precise single- and combinatorial-treatments for Alzheimer's disease and other brain disorders.

Poorer sleep impairs brain health at midlife

Sleep is an emerging risk factor for dementia but its association with brain health remains unclear. This study included UK Biobank (n = 29,545; mean age = 54.65) participants at imaging visit with sleep measures and brain scans, and a subset (n = 14,206) with cognitive measures. Multiple linear regression analyses were conducted to study the associations between sleep and brain health. Every additional hour of sleep above 7 h/day was associated with 0.10-0.25% lower brain volumes. In contrast, a negative non-linear association was observed between sleep duration, grey matter, and hippocampal volume. Both longer (> 9 h/day) and shorter sleep (< 6 h/day) durations were associated with lower brain volumes and cognitive measures (memory, reaction time, fluid intelligence). Additionally, daytime dozing was associated with lower brain volumes (grey matter and left hippocampus volume) and lower cognitive measures (reaction time and fluid intelligence). Poor sleep (< 6 h/day, > 9 h/day, daytime dozing) at midlife was associated with lower brain health. Sleep may be an important target to improve brain health into old age and delay the onset of dementia.

Alzheimer's Disease Biomarkers and Complement Proteins Mediate the Impact of Sleep Fragmentation on Cognitive Impairment in Obstructive Sleep Apnea Patients Without Dementia

BACKGROUND

Cognitive impairment is common in patients with obstructive sleep apnea (OSA). Previous studies indicated that intermittent hypoxia, sleep fragmentation, and depressive symptoms were associated with cognitive impairment in OSA patients.

OBJECTIVE

The study aimed to investigate whether sleep characteristics and depressive symptoms affected cognitive abilities mediated by Alzheimer's disease (AD) biomarkers and complement proteins in OSA patients without dementia.

METHODS

A total of 317 subjects without dementia who had undergone polysomnography, cognitive and neuropsychological evaluations, were recruited. Neuronal-derived exosomes (NDEs) levels for amyloid-β (Aβ), total tau (T-tau), and tau phosphorylated 62 at threonine 181 (P-T181-tau) and astrocyte-derived exosomes (ADEs) levels for complement proteins were measured. Mediation analysis were performed to explore the mediation effects of AD biomarkers (Aβ42, T-tau, P-T181-tau) and complement proteins (C3b and C5b-9) on cognition.

RESULTS

The findings revealed that the association between sleep fragmentation and cognition was mediated by Aβ42 (the percentage varied from 18.25% to 30.6%), P-T181-tau (the percentage varied from 24.36% to 32.3%), and C5b-9 (the percentage varied from 30.88% to 60.7%). The influence of depressive symptoms on cognition was only mediated via C3b (the percentage varied from 24.1% to 36.6%).

CONCLUSIONS

In OSA patients without dementia, Aβ42 and P-T181-tau levels in NDEs, and C5b-9 levels in ADEs mediated the impact of sleep fragmentation on cognitive impairment, and C3b levels in ADEs mediated the impact of depressive symptoms on cognitive impairment.

The impact of sleep components, quality and patterns on glymphatic system functioning in healthy adults: A systematic review

OBJECTIVE

The glymphatic system is thought to be responsible for waste clearance in the brain. As it is primarily active during sleep, different components of sleep, subjective sleep quality, and sleep patterns may contribute to glymphatic functioning. This systematic review aimed at exploring the effect of sleep components, sleep quality, and sleep patterns on outcomes associated with the glymphatic system in healthy adults.

METHODS

PubMed®, Scopus, and Web of Science were searched for studies published in English until December 2021. Articles subjectively or objectively investigating sleep components (total sleep time, time in bed, sleep efficiency, sleep onset latency, wake-up after sleep onset, sleep stage, awakenings), sleep quality, or sleep pattern in healthy individuals, on outcomes associated with glymphatic system (levels of amyloid-β, tau, α-synuclein; cerebrospinal fluid, perivascular spaces; apolipoprotein E) were selected.

RESULTS

Out of 8359 records screened, 51 studies were included. Overall, contradictory findings were observed according to different sleep assessment method. The most frequently assessed sleep parameters were total sleep time, sleep quality, and sleep efficiency. No association was found between sleep efficiency and amyloid-β, and between slow-wave activity and tau. Most of the studies did not find any correlation between total sleep time and amyloid-β nor tau level. Opposing results correlated sleep quality with amyloid-β and tau.

CONCLUSIONS

This review highlighted inconsistent results across the studies; as such, the specific association between the glymphatic system and sleep parameters in healthy adults remains poorly understood. Due to the heterogeneity of sleep assessment methods and the self-reported data representing the majority of the observations, future studies with universal study design and sleep methodology in healthy individuals are advocated.

Nanowired Delivery of Cerebrolysin Together with Antibodies to Amyloid Beta Peptide, Phosphorylated Tau, and Tumor Necrosis Factor Alpha Induces Superior Neuroprotection in Alzheimer's Disease Brain Pathology Exacerbated by Sleep Deprivation

Sleep deprivation induces amyloid beta peptide and phosphorylated tau deposits in the brain and cerebrospinal fluid together with altered serotonin metabolism. Thus, it is likely that sleep deprivation is one of the predisposing factors in precipitating Alzheimer's disease (AD) brain pathology. Our previous studies indicate significant brain pathology following sleep deprivation or AD. Keeping these views in consideration in this review, nanodelivery of monoclonal antibodies to amyloid beta peptide (AβP), phosphorylated tau (p-tau), and tumor necrosis factor alpha (TNF-α) in sleep deprivation-induced AD is discussed based on our own investigations. Our results suggest that nanowired delivery of monoclonal antibodies to AβP with p-tau and TNF-α induces superior neuroprotection in AD caused by sleep deprivation, not reported earlier.

Sleep deficiency promotes Alzheimer's disease development and progression

Sleep disorders are a common health problem in modern society. Long-term sleep deficiency increases the risk for Alzheimer's disease. However, the exact mechanisms by which sleep deficiency affects Alzheimer's disease remain unclear. Therefore, we reviewed the relevant studies and investigated the role of sleep deprivation in Alzheimer's disease pathogenesis. Sleep deficiency was found to be associated with oxidative stress, β-amyloid protein deposition, tau hyperphosphorylation, and neuroinflammation, which are known to increase the risk for Alzheimer's disease. In addition, insufficient sleep also increases glucocorticoid levels, decreases brain-derived neurotrophic factor levels, and reduces the number of synapses in the central nervous system. These factors also promote Alzheimer's disease development and progression. The present study showed that a growing body of evidence supports an association between sleep disturbances and Alzheimer's disease. It discusses the role of sleep insufficiency in Alzheimer's disease pathogenesis, which may provide a theoretical basis for effective treatment and prevention strategies.

Interactions between apolipoprotein E, sex, and amyloid-beta on cerebrospinal fluid p-tau levels in the European prevention of Alzheimer's dementia longitudinal cohort study (EPAD LCS)

Background

Alzheimer's Disease, the leading cause of dementia, is over-represented in females. The apolipoprotein E (APOE)ε4 allele is the strongest genetic risk factor for late-onset AD and is associated with aberrant cerebrospinal fluid levels (CSF) of total tau (t-tau), phosphorylated tau (p-tau), and amyloid-β (Aβ). There is some evidence that sex may mediate the relationship between APOE status and CSF tau, however, evidence is mixed.

Methods

We aimed to examine the interaction between sex, APOE ε4 status, CSF Aβ on t-tau and p-tau in 1599 mid-to-late life individuals without a diagnosis of dementia in the European Prevention of Alzheimer's Dementia (EPAD) longitudinal cohort study.

Findings

We found a significant interaction between APOE status, sex, and CSF Aβ on CSF p-tau levels (β = 0·18, p = 0·04). Specifically, there was a stronger association between APOE status and CSF Aβ₄₂ on CSF p-tau in males compared to females. Further, in females with high Aβ levels (reflecting less cortical deposition), ε4 carriers had significantly elevated p-tau levels relative to non-carriers (W = 39663, p = 0·01). However, there were no significant differences in p-tau between male ε4 carriers and non-carriers with high Aβ (W = 23523, p = 0·64).

Interpretation

An interaction between sex and cerebrospinal fluid Aβ may mediate the relationship between APOE status and CSF p-tau. These data suggest tau accumulation may be independent of Aβ in females, but not males.

Funding

Innovative Medicines Initiative, Swedish Research Council, Alzheimer Drug Discovery Foundation, Swedish Alzheimer Foundation, the Swedish state under the agreement between the Swedish government and the County Councils: the ALF-agreement, and the Alzheimer's Association 2021 Zenith Award.

Biofluid-based biomarkers for Alzheimer's disease-related pathologies: An update and synthesis of the literature

The past few years have seen an explosion in sensitive and specific assays for cerebrospinal fluid (CSF) and blood biomarkers for Alzheimer's disease (AD) and related disorders, as well as some novel assays based on pathological seed-induced protein misfolding in patient samples. Here, I review this exciting field that promises to transform dementia diagnostics and disease monitoring. I discuss data on biomarkers for amyloid beta (Aβ) and tau pathology, neurodegeneration, and glial activation, mention the most promising biomarkers for α-synuclein and TDP-43 pathology, and highlight the need for further research into common co-pathologies. Finally, I consider practical aspects of blood-based biomarker-supported AD diagnostics and emphasize the importance of biomarker interpretation in a full clinical context.

Research advances in the study of sleep disorders, circadian rhythm disturbances and Alzheimer’s disease

Although there are still no satisfactory answers to the question of why we need to sleep, a better understanding of its function will help to improve societal attitudes toward sleep. Sleep disorders are very common in neurodegenerative diseases and are a key factor in the quality of life of patients and their families. Alzheimer’s disease (AD) is an insidious and irreversible neurodegenerative disease. Along with progressive cognitive impairment, sleep disorders and disturbances in circadian rhythms play a key role in the progression of AD. Sleep and circadian rhythm disturbances are more common in patients with AD than in the general population and can appear early in the course of the disease. Therefore, this review discusses the bidirectional relationships among circadian rhythm disturbances, sleep disorders, and AD. In addition, pharmacological and non-pharmacological treatment options for patients with AD and sleep disorders are outlined.

Bidirectional Relationship Between Sleep Disturbances and Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD). Both diseases share common clinical and pathological features: the gradual progression of neurological and psychiatric symptoms caused by neuronal dysfunction and neuronal cell death due to the accumulation of misfolded and neurotoxic proteins. Furthermore, both of them are multifactorial diseases in which both genetic and non-genetic factors contribute to the disease course. Non-genetic factors are of particular interest for the development of preventive and therapeutic approaches for these diseases because they are modifiable; of these, sleep is a particularly intriguing factor. Sleep disturbances are highly prevalent among both patients with AD and PD. To date, research has suggested that sleep disturbances are a consequence as well as a risk factor for the onset and progression of AD, which implies a bidirectional relationship between sleep and AD. Whether such a relationship exists in PD is less certain, albeit highly plausible given the shared pathomechanisms. This review examines the current evidence for the bidirectional relationship between sleep and PD. It includes research in both humans and animal models, followed by a discussion of the current understanding of the mechanisms underlying this relationship. Finally, potential avenues of research toward achieving disease modification to treat or prevent PD are proposed. Although further efforts are crucial for preventing the onset and slowing the progress of PD, it is evident that sleep is a valuable candidate target for future interventions to improve the outcomes of PD patients.

Long-lasting effects of postweaning sleep deprivation on cognitive function and social behaviors in adult mice

Sleep deprivation (SD) has adverse effects on physical and mental health. Recently increasing attention has been given to SD in the early-life stage. However, the effects and mechanisms of postweaning SD on cognitive function and social behaviors are still unclear. In this study, SD was conducted in mice from postnatal Day 21 (PND21) to PND42, 6 h a day. Meanwhile, changes in body weight, food and water intake were continuously monitored. Behavioral tests were carried out in adulthood of mice. The levels of serum corticosterone, the proinflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and the anti-inflammatory cytokines interleukin-10 (IL-10), vasopressin (VP) and oxytocin (OT) were measured by ELISA. Golgi staining was used to calculate neural dendritic spine density in the dorsal hippocampus (dHPC) CA1 region and medial prefrontal cortex (mPFC). We found that postweaning SD increased the food intake and the weight of female mice. Behavioral results showed that postweaning SD caused cognitive impairment and lowered social dominance in adult male mice but not in female mice. ELISA results showed that SD increased the levels of serum corticosterone, VP and OT in male mice and serum OT in female mice. Golgi staining analysis showed that SD decreased neural dendritic spine density in the dHPC in male mice. These results suggest that postweaning SD has a long-term effect on social dominance and cognitive function in male mice, which may provide a new insight into the role of SD in regulating cognitive function and social behaviors.

Sleep-Wake Disorders in Alzheimer's Disease: A Review

Alzheimer's disease (AD) is a multifactorial disease, and it has become a serious health problem in the world. Senile plaques (SPs) and neurofibrillary tangles (NFTs) are two main pathological characters of AD. SP mainly consists of aggregated β-amyloid (Aβ), and NFT is formed by hyperphosphorylated tau protein. Sleep-wake disorders are prevalent in AD patients; however, the links and mechanisms of sleep-wake disorders on the AD pathogenesis remain to be investigated. Here, we referred to the sleep-wake disorders and reviewed some evidence to demonstrate the relationship between sleep-wake disorders and the pathogenesis of AD. On one hand, the sleep-wake disorders may lead to the increase of Aβ production and the decrease of Aβ clearance, the spreading of tau pathology, as well as oxidative stress and inflammation. On the other hand, the ApoE4 allele, a risk gene for AD, was reported to participate in sleep-wake disorders. Furthermore, some neurotransmitters, such as acetylcholine, glutamate, serotonin, melatonin, and orexins, and their receptors were suggested to be involved in AD development and sleep-wake disorders. We discussed and suggested some possible therapeutic strategies for AD treatment based on the view of sleep regulation. In general, this review explored different views to find novel targets of diagnosis and therapy for AD.

MRI-visible enlarged perivascular spaces: imaging marker to predict cognitive impairment in older chronic insomnia patients

OBJECTIVE

Perivascular spaces (PVS), components of the glymphatic system in the brain, have been known to be important conduits for clearing metabolic waste, and this process mainly increases during sleep. Sleep disruption might result in PVS dysfunction and cognitive impairment. In this study, we aim to explore whether MRI-visible enlarged perivascular spaces (EPVS) could be imaging markers to predict cognitive impairment in chronic insomnia patients.

METHOD

We obtained data from 156 patients with chronic insomnia and 79 age-matched healthy individuals. Using T2-weighted MRI images, visible EPVS in various brain regions were measured and analyzed. The associations between EPVS numbers and cerebrospinal fluid (CSF) β-amyloid 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) level in chronic insomnia patients were evaluated.

RESULT

Our results showed that MRI-visible EPVS in the frontal cortex, centrum semiovale, basal ganglia, and hippocampus of chronic insomnia patients with impaired cognition (ICG) significantly increased than that in normal cognition (NCG) patients. The increased MRI-visible EPVS in the frontal cortex, centrum semiovale, and basal ganglia were also associated with the increased CSF Aβ42, t-tau, and p-tau level in ICG patients. MRI-visible EPVS in the basal ganglia and centrum semiovale had high sensitivity and specificity in distinguishing ICG chronic insomnia patients from those with NCG.

CONCLUSION

Our study indicated that MRI-visible EPVS in the basal ganglia and centrum semiovale might be valuable imaging markers to predict cognitive impairment in chronic insomnia patients. It will be meaningful to discern those cognitive decline patients in preclinical stage and take some measures to prevent disease progression.

KEY POINTS

• Increased MRI-visible EPVS were associated with the increased CSF Aβ42, t-tau, and p-tau level in older chronic insomnia patients with impaired cognition.

Sleep and Alzheimer: The Link

Alzheimer's disease is the most common type of dementia which has both cognitive and non-cognitive disabilities. Recent research has proved that sleep deprivation and insomnia have been related to the pathophysiology of Alzheimer's disease and would influence the symptoms and progression of the disease. We look at the current research that supports the idea that the lack of sleep relates to cognitive decline and dementia, with an emphasis on Alzheimer's disease. We integrated the various possible mechanisms of sleep deprivation leading to Alzheimer's disease and cognitive decline. The role of neuroinflammation, generation of reactive oxidative species and sleep disturbances play a central role in tau generation and Aβ deposition. An approach to manage sleep changes can widely prevent the cognitive decline of Alzheimer's disease.

Sleep, cerebrospinal fluid, and the glymphatic system: A systematic review

Current theories of the glymphatic system (GS) hypothesize that it relies on cerebrospinal fluid (CSF) circulation to disseminate growth factors and remove metabolic waste from the brain with increased CSF production and circulation during sleep; thereby, linking sleep disturbance with elements of CSF circulation and GS exchange. However, our growing knowledge of the relations between sleep, CSF, and the GS are plagued by variability in sleep and CSF measures across a wide array of pathologies. Hence, this review aims to summarize the dynamic relationships between sleep, CSF-, and GS-related features in samples of typically developing individuals and those with autoimmune/inflammatory, neurodegenerative, neurodevelopmental, sleep-related, neurotraumatic, neuropsychiatric, and skull atypicalities. One hundred and ninety articles (total n = 19,129 participants) were identified and reviewed for pathology, CSF circulation and related metrics, GS function, and sleep. Numerous associations were documented between sleep problems and CSF metabolite concentrations (e.g., amyloid-beta, orexin, tau proteins) and increased CSF volumes or pressure. However, these relations were not universal, with marked differences across pathologies. It is clear that elements of CSF circulation/composition and GS exchange represent pathways influenced by sleep; however, carefully designed studies and advances in GS measurement are needed to delineate the nuanced relationships.

Sleep Quality Improvement Enhances Neuropsychological Recovery and Reduces Blood Aβ42/40 Ratio in Patients with Mild–Moderate Cognitive Impairment

Background and objectives: Alzheimer’s disease is a progressive brain degeneration and is associated with a high prevalence of sleep disorders. Amyloid β peptide-42/40 (Aβ_42/40) and Tau-pT181 are the core biomarkers in cerebrospinal fluid and blood. Accumulated data from studies in mouse models and humans demonstrated an aberrant elevation of these biomarkers due to sleep disturbance, especially sleep-disordered breathing (SDB). However, it is not clear if sleep quality improvement reduces the blood levels of Ab_42/40 ratio and Tau-pT181 in Alzheimer’s disease patients. Materials and Methods: In this prospective study, a longitudinal analysis was conducted on 64 patients with mild–moderate cognition impairment (MCI) due to Alzheimer’s disease accompanied by SDB. Another 33 MCI cases without sleep-disordered breathing were included as the control group. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) score system. Neuropsychological assessments were conducted using the Montreal Cognitive Assessment (MoCA), Geriatric Depression Scale (GDS), Clinical Dementia Rating (CDR), 24-h Hamilton Rating Scale for Depression (HRSD-24), and Hamilton Anxiety Rating Scale (HAMA) scoring systems. Aβ₄₂, Aβ_40, and Tau-pT181 protein levels in blood specimens were measured using ELISA assays. All patients received donepezil treatment for Alzheimer’s disease. SDB was managed with continuous pressure ventilation. Results: A significant correlation was found among PSQI, HRSD-24, HAMA, Aβ_42/40 ratio, and Tau-pT181 level in all cases. In addition, a very strong and negative correlation was discovered between education level and dementia onset age. Compared to patients without SDB (33 non-SD cases), patients with SDB (64 SD cases) showed a significantly lower HRSD-24 score and a higher Aβ_42/40 ratio Tau-pT181 level. Sleep treatment for patients with SDB significantly improved all neuropsychological scores, Aβ_42/40 ratio, and Tau-pT181 levels. However, 11 patients did not completely recover from a sleep disorder (PSQI > 5 post-treatment). In this subgroup of patients, although HAMA score and Tau-pT181 levels were significantly reduced, MoCA and HRSD-24 scores, as well as Aβ_42/40 ratio, were not significantly improved. ROC analysis found that the blood Aβ_42/40 ratio held the highest significance in predicting sleep disorder occurrence. Conclusions: This is the first clinical study on sleep quality improvement in Alzheimer’s disease patients. Sleep quality score was associated with patient depression and anxiety scores, as well as Aβ_42/40 ratio and Tau-pT181 levels. A complete recovery is critical for fully improving all neuropsychological assessments, Aβ_42/40 ratio, and Tau-pT181 levels. Blood Aβ_42/40 ratio is a feasible prognostic factor for predicting sleep quality.

Slow-wave sleep affects synucleinopathy and regulates proteostatic processes in mouse models of Parkinson's disease

[Figure: see text].

PhosPiR: an automated phosphoproteomic pipeline in R

Large-scale phosphoproteome profiling using mass spectrometry (MS) provides functional insight that is crucial for disease biology and drug discovery. However, extracting biological understanding from these data is an arduous task requiring multiple analysis platforms that are not adapted for automated high-dimensional data analysis. Here, we introduce an integrated pipeline that combines several R packages to extract high-level biological understanding from large-scale phosphoproteomic data by seamless integration with existing databases and knowledge resources. In a single run, PhosPiR provides data clean-up, fast data overview, multiple statistical testing, differential expression analysis, phosphosite annotation and translation across species, multilevel enrichment analyses, proteome-wide kinase activity and substrate mapping and network hub analysis. Data output includes graphical formats such as heatmap, box-, volcano- and circos-plots. This resource is designed to assist proteome-wide data mining of pathophysiological mechanism without a need for programming knowledge.

A biomarker-authenticated model of schizophrenia implicating NPTX2 loss of function

Schizophrenia is a polygenetic disorder whose clinical onset is often associated with behavioral stress. Here, we present a model of disease pathogenesis that builds on our observation that the synaptic immediate early gene NPTX2 is reduced in cerebrospinal fluid of individuals with recent onset schizophrenia. NPTX2 plays an essential role in maintaining excitatory homeostasis by adaptively enhancing circuit inhibition. NPTX2 function requires activity-dependent exocytosis and dynamic shedding at synapses and is coupled to circadian behavior. Behavior-linked NPTX2 trafficking is abolished by mutations that disrupt select activity-dependent plasticity mechanisms of excitatory neurons. Modeling NPTX2 loss of function results in failure of parvalbumin interneurons in their adaptive contribution to behavioral stress, and animals exhibit multiple neuropsychiatric domains. Because the genetics of schizophrenia encompasses diverse proteins that contribute to excitatory synapse plasticity, the identified vulnerability of NPTX2 function can provide a framework for assessing the impact of genetics and the intersection with stress.

The role of orexin in Alzheimer disease: From sleep-wake disturbance to therapeutic target

Accumulating evidence has shown that sleep disturbance is a common symptom in Alzheimer's disease (AD), which is regarded as a modifiable risk factor for AD. Orexin is a key modulator of the sleep-wake cycle and has been found to be dysregulated in AD patients. The increased orexin in cerebrospinal fluid (CSF) is associated with decreased sleep efficiency and REM sleep, as well as cognitive impairment in AD patients. The orexin system has profuse projections to brain regions that are implicated in arousal and cognition and has been found to participate in the progression of AD pathology. Conversely the orexin receptor antagonists are able to consolidate sleep and reduce AD pathology. Therefore, improved understanding of the mechanisms linking orexin system, sleep disturbance and AD could make orexin receptor antagonists a promising target for the prevention or treatment of AD.

Restoring activity in the thalamic reticular nucleus improves sleep architecture and reduces Aβ accumulation in mice

Sleep disruptions promote increases of amyloid β (Aβ) and tau in the brain and increase Alzheimer’s disease (AD) risk, but the precise mechanisms that give rise to sleep disturbances have yet to be defined. The thalamic reticular nucleus (TRN) is essential for sleep maintenance and for the regulation of slow-wave sleep (SWS). We examined the TRN in transgenic mice that express mutant human amyloid precursor protein (APP) and found reduced neuronal activity, increased sleep fragmentation, and decreased SWS time as compared to nontransgenic littermates. Selective activation of the TRN using excitatory DREADDs restored sleep maintenance, increased time in SWS, and reduced amyloid plaque load in both hippocampus and cortex. Our findings suggest that the TRN may play a major role in symptoms associated with AD. Enhancing TRN activity might be a promising therapeutic strategy for AD.

Challenges and Opportunities for Applying Wearable Technology to Sleep

Wearable technology has a history in sleep research dating back to the 1970s. Because modern wearable technology is relatively cheap and widely used by the general population, this represents an opportunity to leverage wearable devices to advance sleep medicine and research. However, there is a lack of published validation studies designed to quantify device performance against accepted gold standards, especially across different populations. Recommendations for conducting performance assessments and using wearable devices are now published with the goal of standardizing wearable device implementation and advancing the field.

Sleep Characteristics and Cognitive Function in Older Adults Without Dementia: The CABLE Study

BACKGROUND

The associations between sleep characteristics and cognition are complicated. Alzheimer's disease (AD) pathologies have been proven to be associated with sleep characteristics.

OBJECTIVE

We aimed to investigate the associations between sleep characteristics and cognitive function and examine the roles of AD pathologies in modulating the association of sleep duration with cognition.

METHODS

A total of 974 participants who had measurements of cerebrospinal fluid (CSF) amyloid-β (Aβ), phosphorylated tau (P-tau), total tau proteins (T-tau), cognitive function, and sleep characteristics were included from the Chinese Alzheimer's Biomarker and Lifestyle (CABLE) study. Linear regression analyses were utilized to explore the associations of sleep characteristics with cognition. Non-linear regression analyses were utilized to explore the associations of sleep habits with cognition. Causal mediation analyses were conducted to explore the mediation effects of AD pathologies on cognition.

RESULTS

The Pittsburgh Sleep Quality Index (PSQI) total score was significantly negatively correlated with Montreal Cognitive Assessment (MoCA) score (p = 0.0176). Long latency (p = 0.0054) and low efficiency (p = 0.0273) were associated with cognitive impairment. Habitual nap behavior was associated with lower MoCA scores (p = 0.0045). U-shaped associations were observed between sleep habits (bedtime and nocturnal sleep duration) and cognition. A causal mediation analysis indicated that P-tau/Aβ42 mediated the association of sleep duration with cognition.

CONCLUSION

These findings showed sleep characteristics were associated with cognitive functions. Sleep habits (duration, bedtime) had U-shaped associations with cognition. AD core pathologies might partially mediate the influence of sleep duration on cognitive impairments.

Plasma phospho-tau181 in presymptomatic and symptomatic familial Alzheimer's disease: a longitudinal cohort study

Blood biomarkers have great potential to advance clinical care and accelerate trials in Alzheimer's disease (AD). Plasma phospho-tau181 (p-tau181) is a promising blood biomarker however, it is unknown if levels increase in presymptomatic AD. Therefore, we investigated the timing of p-tau181 changes using 153 blood samples from 70 individuals in a longitudinal study of familial AD (FAD). Plasma p-tau181 was measured, using an in-house single molecule array assay. We compared p-tau181 between symptomatic carriers, presymptomatic carriers, and non-carriers, adjusting for age and sex. We examined the relationship between p-tau181 and neurofilament light and estimated years to/from symptom onset (EYO), as well as years to/from actual onset in a symptomatic subgroup. In addition, we studied associations between p-tau181 and clinical severity, as well testing for differences between genetic subgroups. Twenty-four were presymptomatic carriers (mean baseline EYO -9.6 years) while 27 were non-carriers. Compared with non-carriers, plasma p-tau181 concentration was higher in both symptomatic (p < 0.001) and presymptomatic mutation carriers (p < 0.001). Plasma p-tau181 showed considerable intra-individual variability but individual values discriminated symptomatic (AUC 0.93 [95% CI 0.85-0.98]) and presymptomatic (EYO ≥ -7 years) (AUC 0.86 [95% CI 0.72-0.94]) carriers from non-carriers of the same age and sex. From a fitted model there was evidence (p = 0.050) that p-tau181 concentrations were higher in mutation carriers than non-carriers from 16 years prior to estimated symptom onset. Our finding that plasma p-tau181 concentration is increased in symptomatic and presymptomatic FAD suggests potential utility as an easily accessible biomarker of AD pathology.

Sleep and liver disease: a bidirectional relationship

Sleep is a complex, highly regulated process essential for human health and wellbeing. Increasingly, sleep-wake disturbance has been implicated in the pathogenesis of chronic liver disease, particularly the development and progression of non-alcoholic fatty liver disease and alcohol-related liver disease. Patients with cirrhosis also have a high burden of sleep abnormalities with substantial implications for their quality of life and physical health. This Review summarises the epidemiology and pathophysiology of sleep-wake disturbance in liver disease and discusses the multiple converging pathways leading to abnormal sleeping patterns in patients with cirrhosis. This includes contributions from altered melatonin metabolism, neuromuscular complications, and aberrant thermoregulation. In turn, a vicious cycle is established whereby disrupted sleep can further contribute to liver disease progression. We also begin to unravel the complex, interlinking relationship between sleep-wake disturbance and hepatic encephalopathy, discussing both overlapping and distinct mechanisms and clinical features. Finally, we summarise the current and future therapeutic approaches aiming to improve sleep quality in patients with cirrhosis.

Aberrant waste disposal in neurodegeneration: why improved sleep could be the solution

Sleep takes up a large percentage of our lives and the full functions of this state are still not understood. However, over the last 10 years a new and important function has emerged as a mediator of brain clearance. Removal of toxic metabolites and proteins from the brain parenchyma generated during waking activity and high levels of synaptic processing is critical to normal brain function and only enabled during deep sleep. Understanding of this process is revealing how impaired sleep contributes an important and likely causative role in the accumulation and aggregation of aberrant proteins such as β-amyloid and phosphorylated tau, as well as inflammation and neuronal damage. We are also beginning to understand how brain slow-wave activity interacts with vascular function allowing the flow of CSF and interstitial fluid to drain into the body's lymphatic system. New methodology is enabling visualization of this process in both animals and humans and is revealing how these processes break down during ageing and disease. With this understanding we can begin to envisage novel therapeutic approaches to the treatment of neurodegeneration, and how reversing sleep impairment in the correct manner may provide a way to slow these processes and improve brain function.

Sleep, neuronal hyperexcitability, inflammation and neurodegeneration: Does early chronic short sleep trigger and is it the key to overcoming Alzheimer's disease?

Evidence links neuroinflammation to Alzheimer's disease (AD); however, its exact contribution to the onset and progression of the disease is poorly understood. Symptoms of AD can be seen as the tip of an iceberg, consisting of a neuropathological build-up in the brain of extracellular amyloid-β (Aβ) plaques and intraneuronal hyperphosphorylated aggregates of Tau (pTau), which are thought to stem from an imbalance between its production and clearance resulting in loss of synaptic health and dysfunctional cortical connectivity. The glymphatic drainage system, which is particularly active during sleep, plays a key role in the clearance of proteinopathies. Poor sleep can cause hyperexcitability and promote Aβ and tau pathology leading to systemic inflammation. The early neuronal hyperexcitability of γ-aminobutyric acid (GABA)-ergic inhibitory interneurons and impaired inhibitory control of cortical pyramidal neurons lie at the crossroads of excitatory/inhibitory imbalance and inflammation. We outline, with a prospective framework, a possible vicious spiral linking early chronic short sleep, neuronal hyperexcitability, inflammation and neurodegeneration. Understanding the early predictors of AD, through an integrative approach, may hold promise for reducing attrition in the late stages of neuroprotective drug development.

Increased Cerebrospinal Fluid Amyloid-β During Sleep Deprivation in Healthy Middle-Aged Adults Is Not Due to Stress or Circadian Disruption

BACKGROUND

Concentrations of soluble amyloid-β (Aβ) oscillate with the sleep-wake cycle in the interstitial fluid of mice and cerebrospinal fluid (CSF) of humans. Further, the concentration of Aβ in CSF increases during sleep deprivation. Stress and disruption of the circadian clock are additional mechanisms hypothesized to increase CSF Aβ levels. Cortisol is a marker for stress and has an endogenous circadian rhythm. Other factors such as glucose and lactate have been associated with changes in sleep-wake activity and/or Aβ.

OBJECTIVE

In this exploratory study, we used samples collected in a previous study to examine how sleep deprivation affects Aβ, cortisol, lactate, and glucose in plasma and CSF from healthy middle-aged adults (N = 11).

METHODS

Eleven cognitively normal participants without evidence of sleep disturbance were randomized to sleep deprivation or normal sleep control. All participants were invited to repeat the study. Cortisol, lactate, glucose, and Aβ were measured in 2-h intervals over a 36-h period in both plasma and CSF. All concentrations were normalized to the mean prior to calculating mesor, amplitude, acrophase, and other parameters.

RESULTS

One night of sleep deprivation increases the overnight concentration of Aβ in CSF approximately 10%, but does not significantly affect cortisol, lactate, or glucose concentrations in plasma or CSF between the sleep-deprived and control conditions.

CONCLUSION

These data suggest that sleep deprivation-related changes in CSF Aβ are not mediated by stress or circadian disruption as measured by cortisol.