Understanding neuron-glia crosstalk and biological clocks in insomnia

Mutual coupling of neurons in the circadian master clock: What we can learn from fruit flies

Circadian master clocks in the brain consist of multiple neurons that are organized into populations with different morphology, physiology, and neuromessenger content and presumably different functions. In most animals, these master clocks are distributed bilaterally, located in close proximity to the visual system, and synchronized by the eyes with the light-dark cycles of the environment. In mammals and cockroaches, each of the two master clocks consists of a core region that receives information from the eyes and a shell region from which most of the output projections originate, whereas in flies and several other insects, the master clocks are distributed in lateral and dorsal brain regions. In all cases, morning and evening clock neurons seem to exist, and the communication between them and other populations of clock neurons, as well as the connection across the two brain hemispheres, is a prerequisite for normal rhythmic function. Phenomena such as rhythm splitting, and internal desynchronization are caused by the "decoupling" of the master clocks in the two brain hemispheres or by the decoupling of certain clock neurons within the master clock of one brain hemisphere. Since the master clocks in flies contain relatively few neurons that are well characterized at the individual level, the fly is particularly well suited to study the communication between individual clock neurons. Here, we review the organization of the bilateral master clocks in the fly brain, with a focus on synaptic and paracrine connections between the multiple clock neurons, in comparison with other insects and mammals.

Glia: the cellular glue that binds circadian rhythms and sleep

Glia are increasingly appreciated as serving an important function in the control of sleep and circadian rhythms. Glial cells in Drosophila and mammals regulate daily rhythms of locomotor activity and sleep as well as homeostatic rebound following sleep deprivation. In addition, they contribute to proposed functions of sleep, with different functions mapping to varied glial subtypes. Here, we discuss recent findings in Drosophila and rodent models establishing a role of glia in circadian or sleep regulation of synaptic plasticity, brain metabolism, removal of cellular debris, and immune challenges. These findings underscore the relevance of glia for benefits attributed to sleep and have implications for understanding the neurobiological mechanisms underlying sleep and associated disorders.

Bone-brain communication mediates the amelioration of Polgonatum cyrtonema Hua polysaccharide on fatigue in chronic sleep-deprived mice

This study aimed to investigate the anti-fatigue efficacy and underlying mechanisms of Polygonatum cyrtonema Hua polysaccharide (PCP) in chronic sleep-deprived mice. Following three weeks of oral administration, PCP demonstrated significant efficacy in alleviating fatigue symptoms. This was evidenced by the prolonged swimming and rotarod time in the high-dose group of PCP, which increased by 73 % and 64 %, respectively. Additionally, serum activities of CAT, GSH-Px, and SOD enzymes rose by 53.56 %, 37.69 % and 53.67 %, respectively, while MDA, lactic acid and BUN levels decreased by 22.90 %, 17.48 % and 24.61 %. The crosstalk between bone and brain is crucial for maintaining energy homeostasis. Molecular docking studies indicated a spontaneous and strong mutual binding between PCP and the bone-promoting target protein BMPR1A. Furthermore, it was observed that PCP enhanced osteogenic differentiation via the BMP-2/Smad1 pathway, leading to an upregulation of osteocalcin expression, which in turn regulated neurotransmitter balance and improved central arousal capacity. Moreover, PCP treatment stimulated neurogenesis by activating the CREB/BDNF/Akt signaling cascade, exhibiting neurotrophic effects. Additionally, PCP increased AMPK phosphorylation and destabilized TXNIP, facilitating astrocyte glucose uptake, glycolysis, and lactate conversion to support neuronal activity. These findings suggested that PCP could effectively respond to energy demands through bone-brain crosstalk, ultimately exerting anti-fatigue properties.

Sleep-Associated Traits and Hearing Difficulties in Noise: A Bidirectional Mendelian Randomization Study

OBJECTIVES

The aim of this study was to investigate the causal relationships between sleep-associated traits and hearing difficulties in noise (HDinN) by Mendelian randomization (MR) analysis.

DESIGN

Single nucleotide polymorphisms associated with chronotype, insomnia, sleep duration, daytime dozing or sleeping, and ease of getting up in the morning were extracted from European population genome-wide association study pooled data for bidirectional MR analysis. The MR-Egger regression, the inverse variance weighted technique, and the weighted median method were used for data analysis. The study was then expanded to include South Asian, East Asian, African, and Greater Middle Eastern populations.

RESULTS

MR analysis indicated that in European populations, ease of getting up in the morning is a protective factor for HDinN (odds ratio [OR] = 0.932, p = 4.22 × 10-5, pFDR = 5.62 × 10-4), while shorter sleep duration was a risk factor (undersleepers: OR = 1.164, p = 0.002, pFDR = 0.014). In addition, there was an indicative causal association between daytime dozing and HDinN (OR = 1.089, p = 0.046, pFDR = 0.123). The conclusions were consistent in African populations (ease of getting up: OR = 0.696, p = 0.012, pFDR = 0.041, sleep duration: OR = 0.677, p = 0.032 pFDR = 0.091, daytime dozing: OR = 1.164, p = 0.002, pFDR = 0.014). In the reverse direction, there was a significant causal association between HDinN and both chronotype (OR = 1.413, p = 0.011, pFDR = 0.042) and ease of getting up in the morning (OR = 0.668, p = 1.75 × 10-5, pFDR = 3.49 × 10-4) in European populations, with similar conclusions respectively reached in East Asian (OR = 1.085, p = 0.010, pFDR = 0.045) and African populations (OR = 0.936, p = 0.002, pFDR = 0.012). Furthermore, although not observed in European populations, exploratory studies in non-European populations suggested a potential association between insomnia and HDinN (East Asian: OR = 1.920, p = 0.011, pFDR = 0.043, African: OR = 2.080, p = 0.004, pFDR = 0.019, South Asian: OR = 1.981, p = 1.59 × 10-4, PFDR = 0.002, Greater Middle Eastern: OR = 2.394, p = 0.002, pFDR = 0.012), and vice versa (Greater Middle Eastern: OR = 1.056, p = 0.014, pFDR = 0.044).

CONCLUSIONS

This study identified a potential bidirectional causal relationship between sleep-associated traits and HDinN. However, the underlying mechanisms of the causal relationships reported here have yet to be elucidated.

The association between insomnia and cognitive decline: A scoping review

OBJECTIVE

This study aimed to investigate the association between insomnia and cognitive decline to provide insights for clinical interventions and future research.

METHODS

The PubMed, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases were systematically searched to identify studies on the association between insomnia and cognitive decline published within the last decade. The quality of the included studies was evaluated, followed by data extraction and summary analysis.

RESULTS

A total of 36 studies were included in the review. Both subjective and objective measures were utilized across 12 indices to assess sleep status, while cognitive function was evaluated using 5 scales and 34 tests. The results revealed a significantly increased risk of cognitive decline or Alzheimer's disease among patients with insomnia, alongside notable impairments in attention, memory, visuospatial abilities, executive function, and verbal memory. Comprehensive assessments of cognitive domains were more sensitive in detecting group differences compared to assessments of specific cognitive sub-functions. Furthermore, MRI analyses showed reduced gray matter volumes in regions such as the prefrontal cortex, cingulate gyrus, temporal lobe, and hippocampus, together with reduced integrity of the white matter in patients with insomnia.

CONCLUSIONS

The findings indicate a potentially bidirectional relationship between insomnia and cognitive decline, suggesting that each may influence and exacerbate the other. Insomnia may increase the risk of cognitive decline and appears to be associated with reduced gray matter volume and compromised white matter integrity in the brain, which could potentially lead to declines in attention, memory, visuospatial abilities, executive function, and verbal memory. Conversely, cognitive decline may contribute to the onset of insomnia, further deteriorating sleep quality. However, further research is necessary to fully comprehend this intricate relationship.

Aromatherapy was used to explore the sedative and hypnotic effects of Moringa seed essential oil on insomnia rats

Moringa is a type of plant that is used both for medicinal and food. Moringa seed (MS) are rich in volatile oil and have initially been employed to treat diseases of the nervous system. Insomnia, a prevalent neurological disorder, has led to this study's aim: to extract the essential oil from MS and analyze its potential to improve sleep. This study utilized petroleum ether for the thermal extraction of the essential oil from MS, which was then subjected to compositional analysis using Gas Chromatograph Mass Spectrometer (GC-MS). P-chlorophenyl alanine (PCPA) was used to induce an insomnia model in Sprague-Dawley (SD) rats. Following the successful establishment of the model, the MS essential oil was administered at concentrations of 10%, 5%, and 2.5% to investigate its sedative and hypnotic effects. The efficacy of the MS essential oil was assessed by observing the general condition of rats in each group, conducting an open field test, a pentobarbital sodium righting test, and measuring the serum 5-HT (5-hydroxytryptamine) levels and hypothalamic GABA (γ-aminobutyric acid) content. GC-MS analysis of the MS essential oil revealed a rich composition, including oleic acid, palmitoleic acid, stigmasterol, and γ-stigmasterol, among other substances. Through the assessment of the rats' general condition, behavioral tests, and blood biochemical assays, it was inferred that MS essential oil aromatherapy can reduce the rat's locomotor activity, increase their interest in activity and exploration, enhance the serum 5-HT levels, and elevate hypothalamic GABA content. Consequently, it can be concluded that MS essential oil has a sedative and hypnotic effect.

Transcriptional signatures of cortical structural changes in chronic insomnia disorder

Chronic insomnia disorder (CID) is a multidimensional disease that may influence various levels of brain organization, spanning the macroscopic structural connectome to microscopic gene expression. However, the connection between genomic variations and morphological alterations in CID remains unclear. Here, we investigated brain structural changes in CID patients at the whole-brain level and whether these link to transcriptional characteristics. Brain structural data from 104 CID patients and 102 matched healthy controls (HC) were acquired to examine cortical structural alterations using morphometric similarity (MS) analysis. Partial least squares (PLS) regression and transcriptome data from the Allen Human Brain Atlas were used to extract genomes related to MS changes. Gene-category enrichment analysis (GCEA) was used to identify potential molecular mechanisms behind the observed structural changes. We found that CID patients exhibited MS reductions in the parietal and limbic regions, along with enhancements in the temporal and frontal regions compared to HCs (pFDR < .05). Subsequently, PLS and GCEA revealed that these MS alterations were spatially correlated with a set of genes, especially those significantly correlated with excitatory and inhibitory neurons and chronic neuroinflammation. This neuroimaging-transcriptomic study bridges the gap between cortical structural changes and the molecular mechanisms in CID patients, providing novel insight into the pathophysiology of insomnia and targeted treatments.

Development and validation of a nomogram for sleep disorders among stroke patients

BACKGROUND

Precisely identifying high-risk sleep disorder patients and implementing suitable measures are important for decreasing the incidence of sleep disorders. In this study, a nomogram method was adopted to construct a tool to predict sleep disorders in stroke based on four factors: individual characteristics, treatment-related factors, psychological factors, and family-related factors.

METHODS

A total of 450 stroke patients were continuously diagnosed at the Affiliated Hospital of Nantong University, and the data on participants were randomly distributed into a training set (n = 315) and a validation set (n = 135). Within the training set, using LASSO regression and random forest methods, five optimal predictors of sleep disorders were identified. Five optimal predictors were used to develop a model. The calibration, discrimination, generalization, and clinical applicability of the model were evaluated using calibration curves, receiver operating characteristic (ROC) curves, internal validation, and decision curve analysis (DCA).

RESULTS

We found that the place of residence, average daily infusion time, the Hospital Anxiety and Depression Scale (HADS), the Type D Personality Scale-14 (DS14), and the Fatigue Severity Scale (FSS) were crucial factors associated with sleep disorders. The validation data showed an area under the curve (AUC) of 0.903 compared to 0.899 in the training set. There was an approach to the diagonal in the calibration curve of this model, and the results of DCA noted that it is clinically beneficial across a range of thresholds from 5 % to 99 %.

CONCLUSION

A model was developed to predict sleep disorders among stroke patients to help hospital staff evaluate the risk among patients and screen high-risk patients.

Association between yogurt and dietary supplements containing probiotic consumption with sleep disturbance in US adults: Results from NHANES, 2009-2018

Purpose

Sleep disorders are common globally. Probiotics may improve human microbial diversity, offering potential benefits for sleep disturbances by enhancing sleep quality and reducing disorders. We aimed to use a population-based study to investigate the association between yogurt (a probiotic food) and probiotic consumption with sleep disturbances in US adults.

Methods

A total of 49,693 adults from the 2009-2018 National Health and Nutrition Examination Survey (NHANES) were included in the analyses. Sleep disorders and sleep duration were assessed according to the Sleep Disorders Questionnaire. The Dietary Questionnaire evaluated yogurt and dietary supplements containing probiotic consumption. After adjusting for confounding factors, weighted multivariable logistic regression and subgroup analyses were used to assess the association between yogurt and probiotic consumption and sleep status.

Results

Of the study cohort, 3535 (14.24 %) participants consumed yogurt and/or dietary supplements containing probiotics. The prevalence of sleep disorders was 16.22 %. Only 53.51 % of the participants achieved the recommended amount of sleep (7-9 h), with 6.10 % and 33.48 % having excessive and insufficient sleep duration, respectively. Weighted Logistic regression models indicated a significant association of probiotic intake with a decreased risk of sleep disturbances compared with those without yogurt or probiotic consumption after adjustments. (For sleep disorders: OR: 0.96, 95 % CI 0.94-0.98, P < 0.001; for sleep duration: OR: 0.98, 95 % CI 0.96-1.00, P = 0.081) Moreover, the effect size of the probiotic intake on sleep was especially significant in sex, race, and BMI subgroups.

Conclusion

The present study first indicated that yogurt and probiotic consumption were associated with a reduced risk of sleep disturbances in US adults, particularly among males, whites, and those with a normal BMI. Incorporating yogurt or probiotics into the diet could serve as a public health strategy for improving sleep disturbances, though further investigation into the underlying mechanisms is needed.

The Longevity Med Summit: insights on healthspan from cell to society

In recent years, there has been a paradigm shift with regards to ageing, challenging its traditional perception as an inevitable and natural process. Researchers have collectively identified hallmarks of ageing, nine of which were initially proposed in 2013 and expanded in 2023 to include disabled macroautophagy, chronic inflammation, and dysbiosis, enhancing our understanding of the ageing process at microscopic, cellular, and system-wide levels. Strategies to manipulate these hallmarks present opportunities for slowing, preventing, or reversing age-related diseases, thereby promoting longevity. The interdependence of these hallmarks underscores the necessity of a comprehensive, systems-based approach to address the complex processes contributing to ageing. As a primary risk factor for various diseases, ageing diminishes healthspan, leading to extended periods of compromised health and multiple age-related conditions towards the end of life. The significant gap between healthspan and lifespan holds substantial economic and societal implications. The inaugural Longevity Med Summit (4-5 May 2023, Cascais, Portugal) provided an international forum to discuss the academic and industry landscape of healthy longevity research, preventive medicine and clinical practice to enhance healthspan.

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.

Dexmedetomidine attenuates sleep deprivation-induced inhibition of hippocampal neurogenesis via VEGF-VEGFR2 signaling and inhibits neuroinflammation

Long periods of sleep deprivation (SD) have serious effects on health. While the α2 adrenoceptor agonist dexmedetomidine (DEX) can improve sleep quality for patients who have insomnia, the effect of DEX on cognition and mechanisms after SD remains elusive. C57BL/6 mice were subjected to 20 h SD daily for seven days. DEX (100 μg/kg) was administered intravenously twice daily (at 1:00 p.m. and 3:00 p.m.) during seven days of SD. We found that systemic administration of DEX attenuated cognitive deficits by performing the Y maze and novel object recognition tests and increased DCX+, SOX2+, Ki67+, and BrdU+NeuN+/NeuN+ cell numbers in the dentate gyrus (DG) region of SD mice by using immunofluorescence, western blotting, and BrdU staining. DEX did not reverse the decrease in DCX+, SOX2+, or Ki67+ cell numbers in SD mice after administration of the α2A-adrenoceptor antagonist BRL-44408. Furthermore, the vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR2) expression was upregulated in SD+DEX mice compared with SD mice. Luminex analysis showed that the neurogenic effects of DEX were possibly related to the inhibition of neuroinflammation, including IL-1α, IL-2, CCL5, and CXCL1. Our results suggested that DEX alleviated the impaired learning and memory of SD mice potentially by inducing hippocampal neurogenesis via the VEGF-VEGFR2 signaling pathway and by suppressing neuroinflammation, and α2A adrenoceptors are required for the neurogenic effects of DEX after SD. This novel mechanism may add to our knowledge of DEX in the clinical treatment of impaired memory caused by SD.