Molecular Mechanisms Underlying Reciprocal Interactions Between Sleep Disorders and Parkinson's Disease

Correlation of inflammatory markers with depression and sleep disorders accompanying the prodromal stage of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder with increasing incidence and disability rates globally, placing a heavy burden on patients and their families. In the prodromal phase of PD, nonmotor symptoms, particularly depression and sleep disorders, are frequent, with profound effects on disease progression and patient quality of life. Emerging research highlights the critical role of inflammatory markers-including interleukins and tumor necrosis factor-in the pathogenesis of prodromal PD. These inflammatory mediators participate in neurodegenerative processes and may induce or exacerbate depressive symptoms and sleep disorders by disrupting the function of the hypothalamic-pituitary-adrenal axis and affecting neurotransmitter, including serotonin, metabolism. Understanding their correlations with nonmotor symptoms in prodromal PD remains incomplete, limiting our ability to develop targeted interventions. This comprehensive review aims to investigate the specific correlations between inflammatory markers and nonmotor symptoms-particularly depression and sleep disorders-in prodromal PD. The findings could have important practical applications, potentially leading to the development of new diagnostic tools and therapeutic strategies for managing PD. By identifying and understanding these correlations, healthcare providers may better predict disease progression and implement more effective treatments for nonmotor symptoms in PD.

Exploring acupuncture as a therapeutic approach for tic disorders: a review of current understanding and potential benefits

Tic disorders (TD) refer to a condition where individuals experience recurring motor movements (e.g., eye blinking) and/or vocalizations (e.g., throat clearing). These disorders vary in terms of duration, cause, and manifestation of symptoms. Tourette's syndrome (TS) involves the presence of ongoing motor and vocal tics for a minimum of 1 year, with fluctuating intensity. Persistent chronic motor or vocal tic disorder is characterized by either motor or vocal tics (not both) present for at least 1 year. Provisional TD presents with either motor or vocal tics (not both) that have been present for less than 12 months. Though medications like Aripiprazole and dopamine receptor blockers are frequently prescribed, their potential unwanted consequences increase, may result in low adherence. In an effort to improve and broaden the care available for children diagnosed with TD, alternative methods such as acupuncture are being investigated and considered. Acupuncture is a method of traditional Chinese medicine that includes the placement of thin needles into particular areas of the body in order to correct any disruptions or irregularities. Research has demonstrated that acupuncture can help regulate abnormal brain function and relieve tic symptoms in individuals with TD. Additional studies are required to fully evaluate the usefulness of complementary treatments in addressing TD in young individuals, despite its common usage. Herein, we summarized the therapeutic effects of acupuncture in the treatment of TD.

Insomnia in Parkinson's Disease: Causes, Consequences, and Therapeutic Approaches

Sleep disorders represent prevalent non-motor symptoms in Parkinson's disease (PD), affecting over 90% of the PD population. Insomnia, characterized by difficulties in initiating and maintaining sleep, emerges as the most frequently reported sleep disorder in PD, with prevalence rates reported from 27 to 80% across studies. Insomnia not only significantly impacts the quality of life of PD patients but is also associated with cognitive impairment, motor disabilities, and emotional deterioration. This comprehensive review aims to delve into the mechanisms underlying insomnia in PD, including neurodegenerative changes, basal ganglia beta oscillations, and circadian rhythms, to gain insights into the neural pathways involved. Additionally, the review explores the risk factors and comorbidities associated with insomnia in PD, providing valuable insights into its management. Special attention is given to the challenges faced by healthcare providers in delivering care to PD patients and the impact of caregiving roles on patients' quality of life. Overall, this review provides a comprehensive understanding of insomnia in PD and highlights the importance of addressing this common sleep disorder in PD patients.

Enhancing sleep quality in synucleinopathies through physical exercise

During sleep, several crucial processes for brain homeostasis occur, including the rearrangement of synaptic connections, which is essential for memory formation and updating. Sleep also facilitates the removal of neurotoxic waste products, the accumulation of which plays a key role in neurodegeneration. Various neural components and environmental factors regulate and influence the physiological transition between wakefulness and sleep. Disruptions in this complex system form the basis of sleep disorders, as commonly observed in synucleinopathies. Synucleinopathies are neurodegenerative disorders characterized by abnormal build-up of α-synuclein protein aggregates in the brain. This accumulation in different brain regions leads to a spectrum of clinical manifestations, including hypokinesia, cognitive impairment, psychiatric symptoms, and neurovegetative disturbances. Sleep disorders are highly prevalent in individuals with synucleinopathies, and they not only affect the overall well-being of patients but also directly contribute to disease severity and progression. Therefore, it is crucial to develop effective therapeutic strategies to improve sleep quality in these patients. Adequate sleep is vital for brain health, and the role of synucleinopathies in disrupting sleep patterns must be taken into account. In this context, it is essential to explore the role of physical exercise as a potential non-pharmacological intervention to manage sleep disorders in individuals with synucleinopathies. The current evidence on the efficacy of exercise programs to enhance sleep quality in this patient population is discussed.

The association between oxidative balance score and sleep duration: a mediation analysis of a cross-sectional study

Study objectives

The Oxidative Balance Score (OBS), which reflects overall oxidation through diet and lifestyle, has been linked to sleep, but few studies have clarified this relationship. We investigated the association between OBS and sleep duration, and whether oxidative stress (OS) and inflammation mediate the underlying mechanisms.

Methods

Data were obtained from the National Health and Nutrition Examination Survey spanning the years 2007 to 2018. Multivariable logistic regression analyses were used to evaluate the association between OBS and the risk of sleep duration. Mediation analyses were conducted to investigate the role of OS and inflammatory markers.

Results

A significant negative association was found between OBS and sleep duration (p < 0.01). Meanwhile, compared to participants in OBS tertile 1, the ORs (95% CIs) of incident short sleep duration were 0.78 (0.72-0.86) and 0.72 (0.67-0.79) (both p < 0.01) for OBS tertile 2 and 3, respectively. And the ORs (95% CIs) of incident long sleep duration were 0.83 (0.73, 0.95) and 0.66 (0.57, 0.75) (both p < 0.01) for OBS tertiles 2 and 3 after adjustment for multivariate variables. A linear relationship between OBS and short/long sleep duration (p for non-linearity = 0.69/0.94, both p < 0.01) were revealed. Mediation analysis showed absolute neutrophil count, serum total bilirubin mediated the association between OBS and short/long sleep duration with 5.72, 13.41% proportion of mediation, respectively (both p < 0.001).

Conclusion

OBS is negatively associated with sleep duration. OS and inflammatory biomarkers mediate the relationship.

Parkinson's Disease: A Narrative Review on Potential Molecular Mechanisms of Sleep Disturbances, REM Behavior Disorder, and Melatonin

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. There is a wide range of sleep disturbances in patients with PD, such as insomnia and rapid eye movement (REM) sleep behavior disorder (or REM behavior disorder (RBD)). RBD is a sleep disorder in which a patient acts out his/her dreams and includes abnormal behaviors during the REM phase of sleep. On the other hand, melatonin is the principal hormone that is secreted by the pineal gland and significantly modulates the circadian clock and mood state. Furthermore, melatonin has a wide range of regulatory effects and is a safe treatment for sleep disturbances such as RBD in PD. However, the molecular mechanisms of melatonin involved in the treatment or control of RBD are unknown. In this study, we reviewed the pathophysiology of PD and sleep disturbances, including RBD. We also discussed the potential molecular mechanisms of melatonin involved in its therapeutic effect. It was concluded that disruption of crucial neurotransmitter systems that mediate sleep, including norepinephrine, serotonin, dopamine, and GABA, and important neurotransmitter systems that mediate the REM phase, including acetylcholine, serotonin, and norepinephrine, are significantly involved in the induction of sleep disturbances, including RBD in PD. It was also concluded that accumulation of α-synuclein in sleep-related brain regions can disrupt sleep processes and the circadian rhythm. We suggested that new treatment strategies for sleep disturbances in PD may focus on the modulation of α-synuclein aggregation or expression.

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.

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.

Selecting Multiple Node Statistics Jointly from Functional Connectivity Networks for Brain Disorders Identification

Functional connectivity networks (FCN) analysis is instructive for the diagnosis of brain diseases, such as mild cognitive impairment (MCI) and major depressive disorder (MDD) at their early stages. As the critical step of FCN analysis, feature representation provides the basis for finding potential biomarkers of brain diseases. In previous studies, different node statistics (e.g. local efficiency and local clustering coefficients) are usually extracted from FCNs as features for the diagnosis/classification task, which can specifically locate disease-related regions on the node level, so as to help us understand the neurodevelopmental roots of brain disorders. However, each node statistic is proposed only considering a kind of specific network property, which has one-sidedness and limitations. As a result, it is incomplete to represent a node with only one statistic. To resolve this issue, we put forward a novel scheme to select multiple node statistics jointly from the estimated FCNs for automated classification, called multiple node statistics feature selection (MNSFS). Specifically, we first extract multiple statistics from the same nodes and assign each kind of statistic into a group. Then, sparse group least absolute shrinkage and selection operator (sgLASSO) is used to select groups (nodes) and statistics in the groups towards a better classification performance. Such a technique enables us to simultaneously locate the discriminative brain regions, as well as the specific statistics associated with these brain regions, making the classification results more interpretable. We conducted our scheme on two public databases for identifying subjects with MCI and MDD from normal controls. Experimental results show that the proposed scheme achieves superior classification accuracy and features interpreted on the benchmark datasets.

Emerging roles of dysregulated adenosine homeostasis in brain disorders with a specific focus on neurodegenerative diseases

In modern societies, with an increase in the older population, age-related neurodegenerative diseases have progressively become greater socioeconomic burdens. To date, despite the tremendous effort devoted to understanding neurodegenerative diseases in recent decades, treatment to delay disease progression is largely ineffective and is in urgent demand. The development of new strategies targeting these pathological features is a timely topic. It is important to note that most degenerative diseases are associated with the accumulation of specific misfolded proteins, which is facilitated by several common features of neurodegenerative diseases (including poor energy homeostasis and mitochondrial dysfunction). Adenosine is a purine nucleoside and neuromodulator in the brain. It is also an essential component of energy production pathways, cellular metabolism, and gene regulation in brain cells. The levels of intracellular and extracellular adenosine are thus tightly controlled by a handful of proteins (including adenosine metabolic enzymes and transporters) to maintain proper adenosine homeostasis. Notably, disruption of adenosine homeostasis in the brain under various pathophysiological conditions has been documented. In the past two decades, adenosine receptors (particularly A₁ and A_2A adenosine receptors) have been actively investigated as important drug targets in major degenerative diseases. Unfortunately, except for an A_2A antagonist (istradefylline) administered as an adjuvant treatment with levodopa for Parkinson's disease, no effective drug based on adenosine receptors has been developed for neurodegenerative diseases. In this review, we summarize the emerging findings on proteins involved in the control of adenosine homeostasis in the brain and discuss the challenges and future prospects for the development of new therapeutic treatments for neurodegenerative diseases and their associated disorders based on the understanding of adenosine homeostasis.