Sleep Disorders Associated With Alzheimer's Disease: A Perspective

Associations between sleep and cognitive performance in a racially/ethnically diverse cohort: the Study of Women's Health Across the Nation

STUDY OBJECTIVES

To determine whether actigraphy-assessed indices of sleep are associated with cognitive performance in women, and explore whether these associations vary by race/ethnicity.

METHODS

Participants were 1,126 postmenopausal community-dwelling females (mean age 65 years) from the observational Study of Women's Health Across the Nation (SWAN); 25% were black, 46% white, 13% Chinese, 11% Japanese, and 5% Hispanic. Actigraphy-assessed sleep measures included total sleep time, wake after sleep onset (WASO), and fragmentation. Cognitive measures included immediate and delayed verbal memory, working memory, and information processing speed. All measures were assessed in conjunction with SWAN annual visit 15.

RESULTS

Across the sample, after covariate adjustment, greater WASO and fragmentation were concurrently associated with slower information processing speed. Black participants had significantly worse sleep relative to other race/ethnic groups. Significant race/sleep interactions were observed; in black, but not white, participants, greater fragmentation was concurrently associated with worse verbal memory and slower information processing speed, and greater WASO was concurrently associated with slower information processing speed. Sleep-cognitive performance associations were not different in Chinese and Japanese participants relative to white participants.

CONCLUSIONS

Greater wakefulness and fragmentation during sleep are concurrently associated with slower information processing. Sleep continuity impacted concurrent cognitive performance in black, but not white, women. This effect may not have been detected in white women because their sleep was largely within the normal range. Future longitudinal studies in diverse samples are critical to further understand whether race/ethnicity moderates the influence of sleep on cognitive performance.

Health Science Community Will Miss This Bright and Uniting Star: In Memory of Professor Gjumrakch Aliev, M.D, Ph.D

It is with deep sadness that we offer our memorial on the unexpected demise of our dear colleague, Professor Gjumrakch Aliev [...].

Molecular mechanisms in Alzheimer's disease and the impact of physical exercise with advancements in therapeutic approaches

Alzheimer's disease (AD) is one of the most common, severe neurodegenerative brain disorder characterized by the accumulation of amyloid-beta plaques, neurofibrillary tangles in the brain causing neural disintegration, synaptic dysfunction, and neuronal death leading to dementia. Although many US-FDA-approved drugs like Donepezil, Rivastigmine, Galantamine are available in the market, their consumption reduces only the symptoms of the disease but fails in potency to cure the disease. This disease affects many individuals with aging. Combating the disease tends to be very expensive. This review focuses on biochemical mechanisms in the neuron both at normal and AD state with relevance to the tau hypothesis, amyloid hypothesis, the risk factors influencing dementia, oxidative stress, and neuroinflammation altogether integrated with neurodegeneration. A brief survey is carried out on available biomarkers in the diagnosis of the disease, drugs used for the treatment, and the challenges in approaching therapeutic targets in inhibiting the disease pathologies. This review conjointly assesses the demerits with the inefficiency of drugs to reach targets, their side effects, and toxicity. Optimistically, this review directs on the advantageous strategies in using nanotechnology-based drug delivery systems to cross the blood-brain barrier for improving the efficacy of drugs combined with a novel neuronal stem cell therapy approach. Determinately, this review aims at the natural, non-therapeutic healing impact of physical exercise on different model organisms and the effect of safe neuromodulation treatments using repetitive Transcranial Magnetic Stimulation (rTMS), transcranial Electrical Stimulation (tES) in humans to control the disease pathologies prominent in enhancing the synaptic function.

Flowerpot method for rapid eye movement sleep deprivation does not induce stress as defined by elevated serum corticosterone level in rats

Flowerpot method of rapid eye movement sleep (REMS) deprivation (REMSD) has been most extensively used in experiments to decipher the functions of REMS. The most common but serious criticism of this method has been presumed stress experienced by the experimental animals. The lack of systematic studies with appropriate controls to resolve this issue prompted this study. We have compared serum corticosterone levels as a marker of stress in male rats under REMSD by the flowerpot method and multiple types of control conditions. Additionally, to maintain consistency and uniformity of REMSD among groups, in the same rats, we estimated brain Na-K ATPase activity, which has been consistently reported to increase upon REMSD. The most effective method was one rat in single- or multiple-platforms set-up in a pool because it significantly increased Na-K ATPase activity without elevating serum corticosterone level. More than one rat in multiple platform set-up was ineffective and must be avoided. Also, large platform- and recovery-controls must be carried out simultaneously to rule out non-specific confounding effects.

Blood-Brain Barrier Dynamics to Maintain Brain Homeostasis

The blood-brain barrier (BBB) is a dynamic platform for exchange of substances between the blood and the brain parenchyma, and it is an essential functional gatekeeper for the central nervous system (CNS). While it is widely recognized that BBB disruption is a hallmark of several neurovascular pathologies, an aspect of the BBB that has received somewhat less attention is the dynamic modulation of BBB tightness to maintain brain homeostasis in response to extrinsic environmental factors and physiological changes. In this review, we summarize how BBB integrity adjusts in critical stages along the life span, as well as how BBB permeability can be altered by common stressors derived from nutritional habits, environmental factors and psychological stress.

Severe Obstructive Sleep Apnea and Increased Cortical Amyloid-β Deposition

BACKGROUND

The suggested association between severe obstructive sleep apnea (OSA) and risk of Alzheimer's disease (AD) needs further study. Only few recent reports exist on associations between brain amyloid-β (Aβ) burden and severe OSA in middle-aged patients.

OBJECTIVE

Examine the possible presence of cortical Aβ accumulation in middle-aged patients with severe OSA.

METHODS

We performed detailed multimodal neuroimaging in 19 cognitive intact patients (mean 44.2 years) with severe OSA (Apnea-Hypopnea Index >30 h-1). Known etiological factors for possible Aβ accumulation were used as exclusion criteria. Aβ uptake was studied with [11C]-PiB-PET, glucose metabolism with [18F]-FDG-PET, and structural imaging with 3.0T MRI.

RESULTS

When analyzed individually, in [11C]-PiB-PET a substantial number (∼32%) of the patients exhibited statistically significant evidence of increased cortical Aβ uptake based on elevated regional Z-score values, mostly seen bilaterally in the precuneus and posterior cingulum regions. Cortical glucose hypometabolism in [18F]-FDG-PET was seen in two patients. MRI did not show structural changes suggestive of AD-related pathology.

CONCLUSION

Increased [11C]-PiB uptake was seen in middle-aged cognitively intact patients with severe OSA. These findings are similar to those described in cognitive unimpaired older OSA patients. The changes in cortical Aβ uptake suggest that severe OSA itself may predispose to alterations related to AD already in middle-age. Aβ clearance may be compromised without simultaneous evidence of metabolic or structural alterations. The results emphasize the importance of early diagnostics and proper treatment of severe OSA in cognitively intact middle-aged subjects, possibly diminishing the individual risk for later cognitive dysfunction.

Circadian changes in Alzheimer's disease: Neurobiology, clinical problems, and therapeutic opportunities

The understanding of Alzheimer's disease (AD) pathophysiology is an active area of research, and the traditional focus on hippocampus, amyloid and tau protein, and memory impairment has been expanded with components like neuroinflammation, insulin resistance, and circadian rhythm alterations. The bidirectional vicious cycle of neuroinflammation and neurodegeneration on a molecular level may cause functional deficits already long before the appearance of overt clinical symptoms. Located at the crossroads of metabolic, circadian, and hormonal signaling, the hypothalamus has been identified as another brain region affected by AD pathophysiology. Current findings on hypothalamic dysfunction open a broader horizon for studying AD pathogenesis and offer new opportunities for diagnosis and therapy. While treatments with cholinomimetics and memantine form a first line of pharmacological treatment, additional innovative research is pursued toward the development of antiinflammatory, growth factor, or antidiabetic types of medication. Following recent epidemiological data showing associations of AD incidence with modern societal and "life-style"-related risk factors, also nonpharmacological interventions, including sleep optimization, are being developed and some have been shown to be beneficial. Circadian aspects in AD are relevant from a pathophysiological standpoint, but they can also have an important role in pharmacologic and nonpharmacologic interventions, and appropriate timing of sleep, meals, and medication may boost therapeutic efficacy.

Sleep Disturbances and Cognitive Impairment in the Course of Type 2 Diabetes-A Possible Link

There is an increasing number of patients worldwide with sleep disturbances and diabetes. Various sleep disorders, including long or short sleep duration and poor sleep quality of numerous causes, may increase the risk of diabetes. Some symptoms of diabetes, such as painful peripheral neuropathy and nocturia, or associated other sleep disorders, such as sleep breathing disorders or sleep movement disorders, may influence sleep quality and quantity. Both sleep disorders and diabetes may lead to cognitive impairment. The risk of development of cognitive impairment in diabetic patients may be related to vascular and non-vascular and other factors, such as hypoglycemia, hyperglycemia, central insulin resistance, amyloid and tau deposits and other causes. Numerous sleep disorders, e.g., sleep apnea, restless legs syndrome, insomnia, and poor sleep quality are most likely are also associated with cognitive impairment. Adequate functioning of the system of clearance of the brain from toxic substances, such as amyloid β, i.e. glymphatic system, is related to undisturbed sleep and prevents cognitive impairment. In the case of coexistence, sleep disturbances and diabetes either independently lead to and/or mutually aggravate cognitive impairment.

Melatonin regulates Aβ production/clearance balance and Aβ neurotoxicity: A potential therapeutic molecule for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease with multiple predisposing factors and complicated pathogenesis. Aβ peptide is one of the most important pathogenic factors in the etiology of AD. Accumulating evidence indicates that the imbalance of Aβ production and Aβ clearance in the brain of AD patients leads to Aβ deposition and neurotoxic Aβ oligomer formation. Melatonin shows a potent neuroprotective effect and can prevent or slow down the progression of AD, supporting the view that melatonin is a potential therapeutic molecule for AD. Melatonin modulates the regulatory network of secretase expression and affects the function of secretase, thereby inhibiting amyloidogenic APP processing and Aβ production. Additionally, melatonin ameliorates Aβ-induced neurotoxicity and probably promotes Aβ clearance through glymphatic-lymphatic drainage, BBB transportation and degradation pathways. In this review, we summarize and discuss the role of melatonin against Aβ-dependent AD pathogenesis. We explore the potential cellular and molecular mechanisms of melatonin on Aβ production and assembly, Aβ clearance, Aβ neurotoxicity and circadian cycle disruption. We summarize multiple clinical trials of melatonin treatment in AD patients, showing that melatonin has a promising effect on improving sleep quality and cognitive function. This review aims to stimulate further research on melatonin as a potential therapeutic agent for AD.

Sleep, major depressive disorder, and Alzheimer disease: A Mendelian randomization study

OBJECTIVE

To explore the causal relationships between sleep, major depressive disorder (MDD), and Alzheimer disease (AD).

METHODS

We conducted bidirectional 2-sample Mendelian randomization analyses. Genetic associations were obtained from the largest genome-wide association studies currently available in UK Biobank (n = 446,118), Psychiatric Genomics Consortium (n = 18,759), and International Genomics of Alzheimer's Project (n = 63,926). We used the inverse variance-weighted Mendelian randomization method to estimate causal effects and weighted median and Mendelian randomization-Egger for sensitivity analyses to test for pleiotropic effects.

RESULTS

We found that higher risk of AD was significantly associated with being a "morning person" (odds ratio [OR] 1.01, p = 0.001), shorter sleep duration (self-reported: β = -0.006, p = 1.9 × 10^-4; accelerometer based: β = -0.015, p = 6.9 × 10^-5), less likely to report long sleep (β = -0.003, p = 7.3 × 10^-7), earlier timing of the least active 5 hours (β = -0.024, p = 1.7 × 10^-13), and a smaller number of sleep episodes (β = -0.025, p = 5.7 × 10^-14) after adjustment for multiple comparisons. We also found that higher risk of AD was associated with lower risk of insomnia (OR 0.99, p = 7 × 10^-13). However, we did not find evidence that these abnormal sleep patterns were causally related to AD or for a significant causal relationship between MDD and risk of AD.

CONCLUSION

We found that AD may causally influence sleep patterns. However, we did not find evidence supporting a causal role of disturbed sleep patterns for AD or evidence for a causal relationship between MDD and AD.

Alzheimer's Retinopathy: Seeing Disease in the Eyes

The neurosensory retina emerges as a prominent site of Alzheimer's disease (AD) pathology. As a CNS extension of the brain, the neuro retina is easily accessible for noninvasive, high-resolution imaging. Studies have shown that along with cognitive decline, patients with mild cognitive impairment (MCI) and AD often suffer from visual impairments, abnormal electroretinogram patterns, and circadian rhythm disturbances that can, at least in part, be attributed to retinal damage. Over a decade ago, our group identified the main pathological hallmark of AD, amyloid β-protein (Aβ) plaques, in the retina of patients including early-stage clinical cases. Subsequent histological, biochemical and in vivo retinal imaging studies in animal models and in humans corroborated these findings and further revealed other signs of AD neuropathology in the retina. Among these signs, hyperphosphorylated tau, neuronal degeneration, retinal thinning, vascular abnormalities and gliosis were documented. Further, linear correlations between the severity of retinal and brain Aβ concentrations and plaque pathology were described. More recently, extensive retinal pericyte loss along with vascular platelet-derived growth factor receptor-β deficiency were discovered in postmortem retinas of MCI and AD patients. This progressive loss was closely associated with increased retinal vascular amyloidosis and predicted cerebral amyloid angiopathy scores. These studies brought excitement to the field of retinal exploration in AD. Indeed, many questions still remain open, such as queries related to the temporal progression of AD-related pathology in the retina compared to the brain, the relations between retinal and cerebral changes and whether retinal signs can predict cognitive decline. The extent to which AD affects the retina, including the susceptibility of certain topographical regions and cell types, is currently under intense investigation. Advances in retinal amyloid imaging, hyperspectral imaging, optical coherence tomography, and OCT-angiography encourage the use of such modalities to achieve more accurate, patient- and user-friendly, noninvasive detection and monitoring of AD. In this review, we summarize the current status in the field while addressing the many unknowns regarding Alzheimer's retinopathy.

The Association of Sleep Disorders, Obesity and Sleep-Related Hypoxia with Cancer

BACKGROUND

Sleep disorders have emerged as potential cancer risk factors.

OBJECTIVE

This review discusses the relationships between sleep, obesity, and breathing disorders with concomitant risks of developing cancer.

RESULTS

Sleep disorders result in abnormal expression of clock genes, decreased immunity, and melatonin release disruption. Therefore, these disorders may contribute to cancer development. Moreover, in sleep breathing disorder, which is frequently experienced by obese persons, the sufferer experiences intermittent hypoxia that may stimulate cancer cell proliferation.

DISCUSSION

During short- or long- duration sleep, sleep-wake rhythm disruption may occur. Insomnia and obstructive sleep apnea increase cancer risks. In short sleepers, an increased risk of stomach cancer, esophageal squamous cell cancer, and breast cancer was observed. Among long sleepers (>9 hours), the risk of some hematologic malignancies is elevated.

CONCLUSION

Several factors including insomnia, circadian disruption, obesity, and intermittent hypoxia in obstructive sleep apnea are contributing risk factors for increased risk of several types of cancers. However, further studies are needed to determine the more significant of these risk factors and their interactions.

MicroRNA: A Key Player for the Interplay of Circadian Rhythm Abnormalities, Sleep Disorders and Neurodegenerative Diseases

Circadian rhythms are endogenous 24-h oscillators that regulate the sleep/wake cycles and the timing of biological systems to optimize physiology and behavior for the environmental day/night cycles. The systems are basically generated by transcription-translation feedback loops combined with post-transcriptional and post-translational modification. Recently, evidence is emerging that additional non-coding RNA-based mechanisms are also required to maintain proper clock function. MicroRNA is an especially important factor that plays critical roles in regulating circadian rhythm as well as many other physiological functions. Circadian misalignment not only disturbs the sleep/wake cycle and rhythmic physiological activity but also contributes to the development of various diseases, such as sleep disorders and neurodegenerative diseases. The patient with neurodegenerative diseases often experiences profound disruptions in their circadian rhythms and/or sleep/wake cycles. In addition, a growing body of recent evidence implicates sleep disorders as an early symptom of neurodegenerative diseases, and also suggests that abnormalities in the circadian system lead to the onset and expression of neurodegenerative diseases. The genetic mutations which cause the pathogenesis of familial neurodegenerative diseases have been well studied; however, with the exception of Huntington's disease, the majority of neurodegenerative diseases are sporadic. Interestingly, the dysfunction of microRNA is increasingly recognized as a cause of sporadic neurodegenerative diseases through the deregulated genes related to the pathogenesis of neurodegenerative disease, some of which are the causative genes of familial neurodegenerative diseases. Here we review the interplay of circadian rhythm disruption, sleep disorders and neurodegenerative disease, and its relation to microRNA, a key regulator of cellular processes.

Circadian and sleep dysfunction in Alzheimer's disease

Alzheimer's disease (AD) is a devastating and irreversible cognitive impairment and the most common type of dementia. Along with progressive cognitive impairment, dysfunction of the circadian rhythms also plays a pivotal role in the progression of AD. A mutual relationship among circadian rhythms, sleep, and AD has been well-recommended. The etiopathogenesis of the disturbances of the circadian system and AD share some general features that also unlock the outlook of observing them as a mutually dependent pathway. Indeed, the burden of amyloid β (Aβ), neurofibrillary tangles (NFTs), neuroinflammation, oxidative stress, and dysfunction of circadian rhythms may lead to AD. Aging can alter both sleep timings and quality that can be strongly disrupted in AD. Increased production of Aβ and reduced Aβ clearance are caused by a close interplay of Aβ, sleep disturbance and raised wakefulness. Besides Aβ, the impact of tau pathology is possibly noteworthy to the sleep deprivation found in AD. Hence, this review is focused on the primary mechanistic complexities linked to disruption of circadian rhythms, sleep deprivation, and AD. Furthermore, this review also highlights the potential therapeutic strategies to abate AD pathogenesis.

Slow Wave Sleep Is a Promising Intervention Target for Alzheimer's Disease

Alzheimer's disease (AD) is the major cause of dementia, characterized by the presence of amyloid-beta plaques and neurofibrillary tau tangles. Plaques and tangles are associated with sleep-wake cycle disruptions, including the disruptions in non-rapid eye movement (NREM) slow wave sleep (SWS). Alzheimer's patients spend less time in NREM sleep and exhibit decreased slow wave activity (SWA). Consistent with the critical role of SWS in memory consolidation, reduced SWA is associated with impaired memory consolidation in AD patients. The aberrant SWA can be modeled in transgenic mouse models of amyloidosis and tauopathy. Animal models exhibited slow wave impairments early in the disease progression, prior to the deposition of amyloid-beta plaques, however, in the presence of abundant oligomeric amyloid-beta. Optogenetic rescue of SWA successfully halted the amyloid accumulation and restored intraneuronal calcium levels in mice. On the other hand, optogenetic acceleration of slow wave frequency exacerbated amyloid deposition and disrupted neuronal calcium homeostasis. In this review, we summarize the evidence and the mechanisms underlying the existence of a positive feedback loop between amyloid/tau pathology and SWA disruptions that lead to further accumulations of amyloid and tau in AD. Moreover, since SWA disruptions occur prior to the plaque deposition, SWA disruptions may provide an early biomarker for AD. Finally, we propose that therapeutic targeting of SWA in AD might lead to an effective treatment for Alzheimer's patients.

Investigating Relationships Between Hypertension, Sleep, and Cognitive Risk in an Underserved Community

PURPOSE

The aim of this descriptive correlational pilot study was to investigate the relationship between hypertension, sleep deprivation, and risk of Alzheimer's disease in a rural, older, underserved, and ethnically diverse cohort.

SAMPLE

Residents (n = 52) from three independent subsidized housing units for retired farmer workers, located in a rural Florida area known as the Glades, volunteered for the study.

METHODS

A quantitative descriptive approach using Pearson correlations, t-tests, and scatter plot analysis was applied to surveys and Mini-CogTM results.

FINDINGS

About a quarter (23.1%) of the participants were identified as being at risk for cognitive impairment. Hypertension risk correlated moderately with cognitive impairment risk (r = 0.40, p = 0.01). However, in this ethnically, diverse cohort, sleep quality did not significantly influence either blood pressure or cognitive status. This is contrary to other studies that have found an increased risk of Alzheimer's disease among persons with hypertension (Carnevale, Perrotta, Lembo, & Trimarco, 2015) and insufficient sleep (Brzecka et al., 2018).

IMPLICATIONS

These results suggest that further investigation is needed to examine if rural living or culture moderates Alzheimer's disease risk factors of diminished sleep and hypertension. Future findings could impact the design of interventions aimed at reducing AD risk in diverse rural settings.

Association between ALDH2 Gene Polymorphism and Late-onset Alzheimer Disease: An Up-to-date Meta-analysis

OBJECTIVES

Previous case-control studies have focused on the relationship between ALDH2 gene polymorphism and late-onset Alzheimer's Disease (LOAD), but no definite unified conclusion has been reached. Therefore, the correlation between ALDH2 Glu504Lys polymorphism and LOAD remains controversial. To analyze the correlation between ALDH2 polymorphism and the risk of LOAD, we implemented this up-to-date meta-analysis to assess the probable association.

METHODS

Studies were searched through China National Knowledge Infrastructure (CNKI), VIP Database for Chinese Technical Periodicals, China Biology Medicine, PubMed, Cochrane Library, Clinical- Trials.gov, Embase, and MEDLINE from January 1, 1994 to December 31, 2018, without any restrictions on language and ethnicity.

RESULTS

Five studies of 1057 LOAD patients and 1136 healthy controls met our criteria for the analysis. Statistically, the ALDH2 GA/AA genotype was not linked with raising LOAD risk (odds ratio (OR) = 1.48, 95% confidence interval (CI) = 0.96-2.28, p = 0.07). In subgroup analysis, the phenomenon that men with ALDH2*2 had higher risk for LOAD (OR = 1.72, 95%CI = 1.10-2.67, p = 0.02) was observed.

CONCLUSION

This study comprehends only five existing case-control studies and the result is negative. The positive trend might appear when the sample size is enlarged. In the future, more large-scale casecontrol or cohort studies should be done to enhance the association between ALDH2 polymorphism and AD or other neurodegenerative diseases.

Circadian learning and memory changes in Aβ1-42 induced Alzheimer's mice

Alzheimer disease (AD) is a growing health problem globally, which causes a progressive decline in learning and memory and multiple disturbances of circadian rhythms. Six Alzheimer's mice and six wild type (WT) mice were involved in this study. Morris Water Maze (MWM) tasks were conducted hourly to evaluate their circadian learning and memory performance. We used a single cosinor-based method to evaluate the circadian learning and memory of Alzheimer's mice and WT mice, respectively. An area sensor was used to record locomotor activity for 2 weeks continuously, including 7 days of 12 h light/12 h dark (LD) conditions and 7 days of 12 h dark/12 h dark (DD) conditions. All WT mice showed circadian rhythm presence in learning and memory, and the peak of escape latency appeared at circadian time (CT) 12. Only one in six Alzheimer's mice showed a circadian rhythm, but the peak of escape latency was postponed to CT20. Alzheimer's mice showed rhythm absence under LD or DD conditions. Under LD conditions, the WT mice activity was higher than that in the Alzheimer's mice during ZT0-5 (p = 0.007) and ZT18-23 (p = 0.353) but lower during ZT6-11 (p < 0.001) and ZT12-17 (p < 0.001). Learning and memory of wild type mice is proved to have a circadian variation throughout a day. In Alzheimer's mice, rhythmic locomotor activity and circadian learning and memory performance were disrupted. Understanding the role of rhythmic disturbances in the process of AD may assist to identify therapeutic targets.

Is Sleep Disruption a Cause or Consequence of Alzheimer's Disease? Reviewing Its Possible Role as a Biomarker

In recent years, the idea that sleep is critical for cognitive processing has gained strength. Alzheimer's disease (AD) is the most common form of dementia worldwide and presents a high prevalence of sleep disturbances. However, it is difficult to establish causal relations, since a vicious circle emerges between different aspects of the disease. Nowadays, we know that sleep is crucial to consolidate memory and to remove the excess of beta-amyloid and hyperphosphorilated tau accumulated in AD patients' brains. In this review, we discuss how sleep disturbances often precede in years some pathological traits, as well as cognitive decline, in AD. We describe the relevance of sleep to memory consolidation, focusing on changes in sleep patterns in AD in contrast to normal aging. We also analyze whether sleep alterations could be useful biomarkers to predict the risk of developing AD and we compile some sleep-related proposed biomarkers. The relevance of the analysis of the sleep microstructure is highlighted to detect specific oscillatory patterns that could be useful as AD biomarkers.

Misfolded proteins as a therapeutic target in Alzheimer's disease

For decades, Alzheimer's Disease (AD) was defined as a disorder of protein misfolding and aggregation. In particular, the extracellular peptide fragment: amyloid-β (Aβ), and the intracellular microtubule-associated protein: tau, were thought to initiate a neurodegenerative cascade which culminated in AD's progressive loss of memory and executive function. As such, both proteins became the focus of intense scrutiny, and served as the principal pathogenic target for hundreds of clinical trials. However, with varying efficacy, none of these investigations produced a disease-modifying therapy - offering patients with AD little recourse aside from transient, symptomatic medications. The near universal failure of clinical trials is unprecedented for a major research discipline. In part, this has motivated an increasing skepticism of the relevance of protein misfolding to AD's etiology. Several recent observations, principally the presence of significant protein pathologies in non-demented seniors, have lent credence to an apparent cursory role for Aβ and tau. Herein, we review both Aβ and tau, examining the processes from their biosynthesis to their pathogenesis and evaluate their vulnerability to medicinal intervention. We further attempt to reconcile the apparent failure of trials with the potential these targets hold. Ultimately, we seek to answer if protein misfolding is a viable platform in the pursuit of a disease-arresting strategy for AD.

Combining lexical and context features for automatic ontology extension

BACKGROUND

Ontologies are widely used across biology and biomedicine for the annotation of databases. Ontology development is often a manual, time-consuming, and expensive process. Automatic or semi-automatic identification of classes that can be added to an ontology can make ontology development more efficient.

RESULTS

We developed a method that uses machine learning and word embeddings to identify words and phrases that are used to refer to an ontology class in biomedical Europe PMC full-text articles. Once labels and synonyms of a class are known, we use machine learning to identify the super-classes of a class. For this purpose, we identify lexical term variants, use word embeddings to capture context information, and rely on automated reasoning over ontologies to generate features, and we use an artificial neural network as classifier. We demonstrate the utility of our approach in identifying terms that refer to diseases in the Human Disease Ontology and to distinguish between different types of diseases.

CONCLUSIONS

Our method is capable of discovering labels that refer to a class in an ontology but are not present in an ontology, and it can identify whether a class should be a subclass of some high-level ontology classes. Our approach can therefore be used for the semi-automatic extension and quality control of ontologies. The algorithm, corpora and evaluation datasets are available at https://github.com/bio-ontology-research-group/ontology-extension.

Neuronal Protein Tyrosine Phosphatase 1B Hastens Amyloid β-Associated Alzheimer's Disease in Mice

Alzheimer's disease (AD) is the most common neurodegenerative disorder, resulting in the progressive decline of cognitive function in patients. Familial forms of AD are tied to mutations in the amyloid precursor protein, but the cellular mechanisms that cause AD remain unclear. Inflammation and amyloidosis from amyloid β (Aβ) aggregates are implicated in neuron loss and cognitive decline. Inflammation activates the protein-tyrosine phosphatase 1B (PTP1B), and this could suppress many signaling pathways that activate glycogen synthase kinase 3β (GSK3β) implicated in neurodegeneration. However, the significance of PTP1B in AD pathology remains unclear. Here, we show that pharmacological inhibition of PTP1B with trodusquemine or selective ablation of PTP1B in neurons prevents hippocampal neuron loss and spatial memory deficits in a transgenic AD mouse model with Aβ pathology (hAPP-J20 mice of both sexes). Intriguingly, while systemic inhibition of PTP1B reduced inflammation in the hippocampus, neuronal PTP1B ablation did not. These results dissociate inflammation from neuronal loss and cognitive decline and demonstrate that neuronal PTP1B hastens neurodegeneration and cognitive decline in this model of AD. The protective effect of PTP1B inhibition or ablation coincides with the restoration of GSK3β inhibition. Neuronal ablation of PTP1B did not affect cerebral amyloid levels or plaque numbers, but reduced Aβ plaque size in the hippocampus. In summary, our preclinical study suggests that targeting PTP1B may be a new strategy to intervene in the progression of AD.SIGNIFICANCE STATEMENT Familial forms of Alzheimer's disease (AD) are tied to mutations in the amyloid precursor protein, but the cellular mechanisms that cause AD remain unclear. Here, we used a mouse model expressing human amyloid precursor protein bearing two familial mutations and asked whether activation of a phosphatase PTP1B participates in the disease process. Systemic inhibition of this phosphatase using a selective inhibitor prevented cognitive decline, neuron loss in the hippocampus, and attenuated inflammation. Importantly, neuron-targeted ablation of PTP1B also prevented cognitive decline and neuron loss but did not reduce inflammation. Therefore, neuronal loss rather than inflammation was critical for AD progression in this mouse model, and that disease progression could be ameliorated by inhibition of PTP1B.

Epigenetic Regulation of BMAL1 with Sleep Disturbances and Alzheimer's Disease

BACKGROUND

An early symptom of Alzheimer's disease (AD) is a disturbance of the circadian rhythm that is associated with disrupted sleep/wake cycles.

OBJECTIVE

To investigate if BMAL1, a key gene that drives the circadian cycle, is epigenetically regulated in brains in relation to longitudinal changes in cognition, sleep quality, and AD neuropathology.

METHODS

Frontal cortex tissues were acquired from the Manchester Brain Bank (N = 96). DNA methylation at six CpG sites at the promoter of BMAL1, determined using bisulfite pyrosequencing, was tested for associations with Braak stage, CERAD score and Thal phase, longitudinal changes in cognition, sleep measurements and cross-section measures of depressive symptoms (BDI score).

RESULTS

Methylation across all the CpGs strongly correlated with each other. We found increased CpG2 methylation with higher Braak (t(92), p = 0.015) and CERAD (t(94), p = 0.044) stages. No significance was found between longitudinal fluid intelligence, processing speed and memory tests, but methylation at CpG1 (r = 0.20, p = 0.05) and CpG4 (r = 0.20, p = 0.05) positively correlated with vocabulary. CpG2 positively correlated with cross-sectional fluid intelligence (r = 0.20 p = 0.05) and vocabulary (r = 0.22 p = 0.03). Though longitudinal analysis revealed no significance between sleep duration, midsleep and efficiency for any of the CpG sites, CpG3 (B = 0.03, 95% CI, p = 0.03) and CpG5 (B = 0.04, 95% CI, p = 0.01) significantly correlated with night wake. CpG4 correlated with depressive symptoms (B = -0.27, 95% CI, p = 0.02).

CONCLUSION

Methylation of BMAL1 associated with tau pathology, changes in cognitive measures, a measure of sleep and depressive symptoms, suggesting an involvement of the circadian cycle.

Effects of sedentary behavior and physical activity on sleep quality in older people: A cross-sectional study

The aim of this cross-sectional study was to investigate the influence of replacing sedentary time with time engaged in one of two levels of physical activity on sleep quality using an isotemporal substitution model. The participants were 70 community-dwelling older Japanese adults (approximately 70% female). Physical activity types were measured using a triaxial accelerometer and categorized based on intensity as sedentary, light-intensity, and vigorous-intensity. The Pittsburgh Sleep Quality Index assessed subjective sleep quality. Objective sleep parameters were assessed using an actigraph. A series of multi-linear regression models analyzed the statistical relationships. Our findings showed that replacing 30 min of sedentary activity per day with an equal period of light-intensity physical activity significantly influenced sleep quality parameters. However, there was no significant difference in sleep quality when light-intensity activity was replaced with vigorous-intensity activity. Engaging in one activity type means less available time for other types of activity; habitual replacement of sedentary activity with light-intensity physical activity might have long-term benefits on the sleep quality of older people.

Alzheimer's disease: Neurotransmitters of the sleep-wake cycle

With aging, our sleeping pattern alters. Elderly often wake unrested because their sleep time and sleep efficacy is reduced. In Alzheimer's disease (AD) patients, these alterations are even more pronounced and may further aggravate cognitive decline. Therefore, sleep disturbances greatly impact self-care ability, caregiver exhaustion and institutionalization rate. Reestablishing an effective sleep-wake cycle in these patients still remains an unresolved challenge, partly because sleep physiology is quite complex and multiple neurotransmitter systems contribute to a single process. Gaining a better understanding of sleep physiology will be crucial for further research. Conjointly, animal models, along with a multidisciplinary approach, will be of great value to establish a common ground between AD and sleep disturbances and work towards a potential therapeutic application.

Subjective Cognitive Decline and Nighttime Sleep Alterations, a Longitudinal Analysis

Objective: The aim of this study was to analyze quantitative sleep changes and their implication on subjective cognitive decline (SCD). Objective sleep patterns were investigated by an actigraph and recorded at the baseline and 2-year after in order to examine specific sleep alterations in SCD.

Background: Sleep disorders are very common among average elderly adults and an altered sleep pattern is known to be a risk factor for future development of mild cognitive impairment (MCI) and dementia. Recent studies have shown how sleep is objectively altered in average senior adults with SCD, without any other significant change in cognition and behavior or brain structure. Considering that both SCD and disrupted sleep are risk factors for future MCI and dementia, with sleep only as a modifiable risk factor, further research is required to deeply investigate the interaction between sleep and SCD.

Methods: Among 70 community-dwelling elderly individuals who had been enrolled at baseline, 35 (64.6 ± 5.6 years, 15 M/20 F) underwent a complete neuropsychological battery and 1-week wrist actigraphy recording 2 years later during the follow-up stage. Individuals were divided into two groups according to their SCD Questionnaire (SCD-Q) score. Sleep hours, sleep efficiency and onset latency, napping and time awake after sleep onset (WASO) were collected. All individuals underwent structural magnetic resonance imaging (MRI) examination to exclude brain disorders. Data collection was performed at baseline and after 2 years at the follow-up phase.

Results: A significantly different night sleep time between the two groups was observed: SCD showed a lower total sleep time (TST) than non-SCD subjects. Moreover, a total time spent in bed (TIB) was significantly lower in SCD subjects over 2 years of observation.

Conclusions: Objective changes over time of the sleep pattern, specifically TIB and TST, are present in SCD individuals. The results of the study show that sleep alterations are common in SCD and underline the clinical importance of screening in order to assess sleep alterations as well as improve sleep in average adults with SCD complaints.

The Sleep-Immune Crosstalk in Health and Disease

Sleep and immunity are bidirectionally linked. Immune system activation alters sleep, and sleep in turn affects the innate and adaptive arm of our body's defense system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can induce an increase in sleep duration and intensity, but also a disruption of sleep. Enhancement of sleep during an infection is assumed to feedback to the immune system to promote host defense. Indeed, sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses. The induction of a hormonal constellation that supports immune functions is one likely mechanism underlying the immune-supporting effects of sleep. In the absence of an infectious challenge, sleep appears to promote inflammatory homeostasis through effects on several inflammatory mediators, such as cytokines. This notion is supported by findings that prolonged sleep deficiency (e.g., short sleep duration, sleep disturbance) can lead to chronic, systemic low-grade inflammation and is associated with various diseases that have an inflammatory component, like diabetes, atherosclerosis, and neurodegeneration. Here, we review available data on this regulatory sleep-immune crosstalk, point out methodological challenges, and suggest questions open for future research.

Mental health in elite athletes: International Olympic Committee consensus statement (2019)

Mental health symptoms and disorders are common among elite athletes, may have sport related manifestations within this population and impair performance. Mental health cannot be separated from physical health, as evidenced by mental health symptoms and disorders increasing the risk of physical injury and delaying subsequent recovery. There are no evidence or consensus based guidelines for diagnosis and management of mental health symptoms and disorders in elite athletes. Diagnosis must differentiate character traits particular to elite athletes from psychosocial maladaptations.

Management strategies should address all contributors to mental health symptoms and consider biopsychosocial factors relevant to athletes to maximise benefit and minimise harm. Management must involve both treatment of affected individual athletes and optimising environments in which all elite athletes train and compete. To advance a more standardised, evidence based approach to mental health symptoms and disorders in elite athletes, an International Olympic Committee Consensus Work Group critically evaluated the current state of science and provided recommendations.

On the central role of mitochondria dysfunction and oxidative stress in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the commonest cause of dementia, with approximately 5 million new cases occurring annually. Despite decades of research, its complex pathophysiology and etiopathogenesis presents a major hindrance to the development of an effective treatment and prevention strategy. Aging is the biggest risk factor for the development of AD, and the total number of older people in the population is going to significantly increase in the next decades, suggesting that AD incidence and prevalence is likely to increase in the future. This makes the need for a better understanding of the disease to be extremely urgent.

METHODS

A search was done by accessing PubMed/Medline, EBSCO, and PsycINFO databases. The search string used was "(dementia* OR Alzheimer's) AND (pathophysiology* OR pathogenesis)". New key terms were identified (new term included "vitamin D, thyroid hormone, mitochondria dysfunction, oxidative stress, testosterone, estrogen, melatonin, progesterone, luteinizing hormone, amyloid-β (Aβ), and hyperphosphorylated tau"). The electronic databases were searched for titles or abstracts containing these terms in all published articles between January 1, 1965, and January 31, 2019. The search was limited to studies published in English and other languages involving both animal and human subjects.

RESULTS

Mitochondria dysfunction and oxidative stress play a critical role in AD etiopathogenesis and pathophysiology.

CONCLUSION

AD treatment and prevention strategies must be geared towards improving mitochondrial function and attenuating oxidative stress.

Dynamic 11C-PiB PET Shows Cerebrospinal Fluid Flow Alterations in Alzheimer Disease and Multiple Sclerosis

Cerebrospinal fluid (CSF) plays an important role in solute clearance and maintenance of brain homeostasis. ¹¹C-Pittsburgh compound B (PiB) PET was recently proposed as a tool for detection of CSF clearance alterations in Alzheimer disease. The current study investigates the magnitude of ¹¹C-PiB PET signal in the lateral ventricles of an independent group of Alzheimer and mild cognitive impairment subjects. We have also evaluated multiple sclerosis as a model of disease with CSF clearance alterations without amyloid-β tissue accumulation. Methods: A set of 11 Alzheimer and 12 mild cognitive impairment subjects and a set of 20 multiple sclerosis subjects with matched controls underwent MRI and dynamic ¹¹C-PiB PET. Lateral ventricle regions of interest were generated manually from MRI data. PET data were analyzed using cerebellum or a supervised reference region for the Alzheimer and multiple sclerosis data sets, respectively. The magnitude of ¹¹C-PiB signal in the lateral ventricles was calculated as area under the curve from 35 to 80 min and SUV ratio (SUVR) from 50 to 70 min. Compartmental modeling analysis was performed on a separate data set containing 11 Alzheimer and matched control subjects; this analysis included an arterial input function, to further understand the kinetics of the lateral ventricular ¹¹C-PiB signal. Results: ANOVA revealed significant group differences in lateral ventricular SUVR across the Alzheimer, mild cognitive impairment, and healthy control groups (P = 0.004). Pairwise comparisons revealed significantly lower lateral ventricular SUVR in Alzheimer subjects than in healthy controls (P < 0.001) or mild cognitive impairment subjects (P = 0.029). Lateral ventricular SUVR was significantly lower in multiple sclerosis subjects than in healthy controls (P = 0.008). Compartmental modeling analysis revealed significantly lower uptake rates of ¹¹C-PiB signal from blood (P = 0.005) and brain tissue (P = 0.004) to the lateral ventricles and significantly lower ¹¹C-PiB signal clearance out of the lateral ventricles (P = 0.002) in Alzheimer subjects than in healthy controls. Conclusion: These results indicate that dynamic ¹¹C-PiB PET can be used to observe pathologic changes in CSF dynamics. We have replicated previous work demonstrating CSF clearance deficits in Alzheimer disease associated with amyloid-β deposits and have extended the observations to include ventricular CSF clearance deficits in mild cognitive impairment and multiple sclerosis.

Sleep Disturbance as a Potential Modifiable Risk Factor for Alzheimer's Disease

Sleep disturbance is a common symptom in patients with various neurodegenerative diseases, including Alzheimer’s disease (AD), and it can manifest in the early stages of the disease. Impaired sleep in patients with AD has been attributed to AD pathology that affects brain regions regulating the sleep–wake or circadian rhythm. However, recent epidemiological and experimental studies have demonstrated an association between impaired sleep and an increased risk of AD. These studies have led to the idea of a bidirectional relationship between AD and impaired sleep; in addition to the conventional concept that impaired sleep is a consequence of AD pathology, various evidence strongly suggests that impaired sleep is a risk factor for the initiation and progression of AD. Despite this recent progress, much remains to be elucidated in order to establish the benefit of therapeutic interventions against impaired sleep to prevent or alleviate the disease course of AD. In this review, we provide an overview of previous studies that have linked AD and sleep. We then highlight the studies that have tested the causal relationship between impaired sleep and AD and will discuss the molecular and cellular mechanisms underlying this link. We also propose future works that will aid the development of a novel disease-modifying therapy and prevention of AD via targeting impaired sleep through non-pharmacological and pharmacological interventions.