Long-term continuous positive airway pressure treatment ameliorates biological clock disruptions in obstructive sleep apnea

Sleep and male (In)Fertility: A comprehensive overview

Infertility affects millions of couples globally, with male factors contributing up to 50 % of cases. Despite the existing Assisted Reproduction Technologies (ART), decreased sperm quality and male infertility persist. Evidence suggests that sleep is crucial for normal reproductive function, and the noticeable increase in infertility rates aligns with the growing prevalence of sleep deprivation, suggesting a connection between both conditions. This literature review explores the possible links between sleep disturbances, with a special emphasis on insomnia, the most prevalent sleep disorder, and male reproductive health. It delves into the latest findings regarding factors such as sperm quality, hormone levels, and overall reproductive function from studies in mammals, both rodents and humans. Through a concise synthesis of these findings, we unveil potential mechanisms and provide crucial insights for clinicians and researchers in the field of reproductive health.

Circadian Biology in Obstructive Sleep Apnea-Associated Cardiovascular Disease

A dysregulated circadian system is independently associated with both Obstructive Sleep Apnea (OSA) and cardiovascular disease (CVD). OSA and CVD coexistence is often seen in patients with prolonged untreated OSA. However, the role of circadian dysregulation in their relationship is unclear. Half of the human genes, associated biological pathways, and physiological functions exhibit circadian rhythms, including blood pressure and heart rate regulation. Mechanisms related to circadian dysregulation and heart function are potentially involved in the coexistence of OSA and CVD. In this article, we provide a comprehensive overview of circadian dysregulation in OSA and associated CVD. We also discuss feasible animal models and new avenues for future research to understand their relationship. Oxygen-sensing pathways, inflammation, dysregulation of cardiovascular processes, oxidative stress, metabolic regulation, hormone signaling, and epigenetics are potential clock-regulated mechanisms connecting OSA and CVD.

Assessment of continuous positive airway pressure effect on the circadian clock signaling pathway in obstructive sleep apnea patients

Obstructive sleep apnea (OSA) is associated with circadian rhythm dysregulation plausibly through affecting clock genes. The study's purpose was to investigate the effect of one-night continuous positive airway pressure treatment (CPAP treatment) on circadian clock genes: BMAL1, CLOCK, CRY1, and PER1 at mRNA and protein levels. The study included 30 OSA patients, who underwent diagnostic polysomnography (PSG) and next a one-night effective CPAP treatment with PSG monitoring (CPAP). The blood was collected in the evening before and the morning after PSG and CPAP. Protein levels and mRNA expression were measured using ELISA and qRT-PCR, respectively. The increase in PER1 expression was observed in the morning after compared to the evening before CPAP (p = 0.005); additionally, PER1 protein level decreased in the morning after CPAP compared to the morning after PSG (p = 0.035). In CLOCK protein levels significant changes were observed: an increase in the morning after CPAP compared to the morning after PSG (p = 0.049), an increase in the morning after CPAP compared to the evening before (p = 0.006), and an increase in difference between the morning after and evening before CPAP vs. difference between morning after and evening before PSG (p = 0.012). Obtained results suggest that even short-term effective CPAP treatment might reverse circadian clock signaling pathway disruption in OSA.

Correlation of the expression of circadian-clock genes with the severity of obstructive sleep apnea in patients

This study investigates the connection of Obstructive Sleep Apnea (OSA) with the expression and daily oscillation patterns of core circadian clock genes and related genes. OSA, a sleep disorder characterized by repetitive airway occlusion leading to nocturnal arousals, sleep fragmentation, and intermittent hypoxemia (IH), shares sleep dysfunction as an overlapping phenotype with circadian clock genes. The research involved 40 subjects (30 OSA patients and 10 normal controls), categorized into four groups based on Polysomnography (PSG) results: normal, mild, moderate, and severe. Peripheral blood samples were collected twice from each participant in the evening before and the morning after PSG examination. Using real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR), the study measured the expression levels of target genes in leukocytes. Results revealed changes in diurnal expression patterns of several genes (PER1, PER3, CRY1, BMAL1, CLOCK, HIF-1α, IL-1β, TNFα) in OSA groups compared to normal controls. While PER2, CRY2, and NPAS2 genes did not show diurnal patterns, their expression was significantly elevated in severe OSA. Notably, the expression levels of HIF-1α, IL-1β, and TNFα increased with OSA severity, consistent with the roles of IH and inflammation as clinical indicators in OSA. These findings not only demonstrate that circadian clock-related gene expression fluctuates with OSA but also provide potential molecular markers for early diagnosis and personalized treatment. By identifying biomarkers parallel to clinical indicators in OSA, this innovative study paves the way for future research and clinical applications in the field.

Elucidating the Interplay of Hypoxia-Inducible Factor and Circadian Clock Signaling in Obstructive Sleep Apnea Patients

BACKGROUND

Hypoxia-inducible factor 1 (HIF-1) affects the circadian clock in obstructive sleep apnea (OSA) and may have a bidirectional relationship with circadian mechanisms. This study examined the link between circadian clock and HIF-1 in OSA patients versus controls.

METHODS

70 participants underwent polysomnography (PSG), and were assigned into OSA (apnea-hypopnea index (AHI) ≥ 5, n = 54) or control (AHI < 5, n = 16) groups. BMAL1 (brain and muscle ARNT like 1), CLOCK (circadian locomotor output cycles kaput), PER1 (period 1), CRY1 (cryptochrome 1), HIF-1α, and HIF-1β gene expressions and protein levels were measured in evening and morning samples, collected before and after PSG.

RESULTS

The OSA group was characterized by increased CLOCK, CRY1, PER1 and HIF-1a protein levels, both in the morning and evening (all p < 0.05), and decreased morning expression of BMAL1 (p = 0.02). Associations between almost all circadian clock gene expressions and both HIF-1 subunits were observed in the OSA group at both time points (all p < 0.05), apart from association between PER1 and HIF-1α in the morning (R = 0.050, p = 0.73). In controls, only a correlation between HIF-1α levels and CRY1 expression in the morning (R = 0.588, p = 0.02) was found.

CONCLUSIONS

OSA affects the circadian clock and HIF-1 pathway, with increased CLOCK, CRY1, PER1, and HIF-1α protein levels observed in OSA patients. The interplay between these systems may involve complex posttranscriptional and posttranslational mechanisms.

Obstructive sleep apnea syndrome, orexin, and sleep-wake cycle: The link with the neurodegeneration

Obstructive sleep apnea syndrome (OSAS) significantly affects the sleep-wake circadian rhythm through intermittent hypoxia and chronic sleep fragmentation. OSAS patients often experience excessive daytime sleepiness, frequent awakenings, and sleep fragmentation, leading to a disrupted circadian rhythm and altered sleep-wake cycle. These disruptions may exacerbate OSAS symptoms and contribute to neurodegenerative processes, particularly through the modulation of clock gene expression such as CLOCK, BMAL1, and PER. Emerging evidence connects OSAS to cognitive impairment and suggests that these changes may contribute to the development of neurodegenerative disorders such as Alzheimer disease, suggesting that OSAS could be a reversible risk factor for these conditions. Biomarkers, including melatonin and orexin, play crucial roles in understanding these mechanisms. In OSAS patients, melatonin, a marker of circadian rhythmicity, often shows altered secretion patterns that are not fully corrected by continuous positive airway pressure therapy. Orexin, which regulates the sleep-wake cycle, exhibits increased cerebrospinal fluid levels in OSAS patients, possibly due to compensatory mechanisms against sleep impairment and daytime sleepiness. These biomarkers highlight the intricate relationship between circadian rhythm disruptions and neurodegenerative risks in OSAS, emphasizing the need for further research and potential therapeutic strategies to mitigate these effects and improve patient outcomes.

Impact of CPAP Therapy on Cognition and Fatigue in Patients with Moderate to Severe Sleep Apnea: A Longitudinal Observational Study

Continued solicitation of cognitive resources eventually leads to cognitive fatigue (CF), i.e., a decrease in cognitive efficiency that develops during sustained cognitive demands in conditions of constrained processing time, independently of sleepiness. The expression of CF and its impact on cognition are partly contingent upon prior sleep quality and its restorative effects. Sleep in obstructive sleep apnea (OSA) may be largely restored through the use of continuous positive airway pressure (CPAP) treatment, contributing to a gradual improvement in sleep quality. In this longitudinal observational study, we investigated immediate and longer-term behavioral effects of CPAP treatment on cognitive functioning, evaluating outcomes after the initiation of treatment, and at three and six months, in compliant CPAP-treated OSA patients. Results indicate that CPAP therapy significantly enhances subjective sleep quality and cognitive functions, including episodic memory, inhibition, sustained attention, working memory, and executive control. Noticeable performance improvements were observed in CF-inducing tasks, particularly after six months of CPAP use. Participants also reported substantial gains in quality of life, reduced daytime sleepiness, and improved mood. These results confirm that CPAP therapy not only alleviates immediate physiological disturbances associated with OSA, but also supports cognitive recovery and enhanced overall daily functioning.

Melatonin mediates intestinal barrier dysfunction and systemic inflammation in moderate-severe OSA patients

BACKGROUND

Intestinal barrier dysfunction and systemic inflammation are common in obstructive sleep apnoea (OSA). We aimed to investigate the role of melatonin, an anti-inflammatory mediator, in mediating the relationships between OSA, intestinal barrier dysfunction and systemic inflammation.

METHODS

Two hundred and thirty-five male participants who complained with sleep problems and underwent whole night polysomnography at our sleep centre between 2017 and 2018 were enrolled. Polysomnographic data, anthropometric measurements and biochemical indicators were collected. Serum melatonin, intestinal barrier function biomarker zonula occludens-1 (ZO-1) and inflammatory biomarkers C-reactive protein (CRP) with lipopolysaccharide (LPS) were detected. Spearman's correlation analysis assessed the correlations between sleep parameters, melatonin and biomarkers (ZO-1, LPS and CRP). Mediation analysis explored the effect of OSA on intestinal barrier dysfunction and systemic inflammation in moderate-severe OSA patients.

RESULTS

As OSA severity increased, serum melatonin decreased, whereas ZO-1, LPS and CRP increased. Spearman's correlation analysis showed that serum melatonin was significantly negatively correlated with ZO-1 (r = -0.19, p < .05) and LPS (r = -0.20, p < .05) in the moderate-OSA group; serum melatonin was significantly negatively correlated with ZO-1 (r = -0.46, p < .01), LPS (r = -0.35, p < .01) and CPR (r = -0.30, p < .05) in the severe-OSA group. Mediation analyses showed melatonin explain 36.12% and 35.38% of the effect of apnoea-hypopnea index (AHI) on ZO-1 and LPS in moderate to severe OSA patients.

CONCLUSIONS

Our study revealed that melatonin may be involved in mediating intestinal barrier dysfunction and systemic inflammation in moderate-to-severe OSA patients.

Circadian Regulation in Diurnal Mammals: Neural Mechanisms and Implications in Translational Research

Diurnal and nocturnal mammals have evolved unique behavioral and physiological adaptations to optimize survival for their day- or night-active lifestyle. The mechanisms underlying the opposite activity patterns are not fully understood but likely involve the interplay between the circadian time-keeping system and various arousal- or sleep-promoting factors, e.g., light or melatonin. Although the circadian systems between the two chronotypes share considerable similarities, the phase relationships between the principal and subordinate oscillators are chronotype-specific. While light promotes arousal and wakefulness in diurnal species like us, it induces sleep in nocturnal ones. Similarly, melatonin, the hormone of darkness, is commonly used as a hypnotic in humans but is secreted in the active phase of nocturnal animals. Thus, the difference between the two chronotypes is more complex than a simple reversal, as the physiological and neurological processes in diurnal mammals during the day are not equivalent to that of nocturnal ones at night. Such chronotype differences could present a significant translational gap when applying research findings obtained from nocturnal rodents to diurnal humans. The potential advantages of diurnal models are being discussed in a few sleep-related conditions including familial natural short sleep (FNSS), obstructive sleep apnea (OSA), and Smith-Magenis syndrome (SMS). Considering the difference in chronotype, a diurnal model will be more adequate for revealing the physiology and physiopathology pertaining to human health and disease, especially in conditions in which circadian rhythm disruption, altered photic response, or melatonin secretion is involved. We hope the recent advances in gene editing in diurnal rodents will promote greater utility of the diurnal models in basic and translational research.

Circadian clock dysregulation: a potential mechanism of depression in obstructive sleep apnea patients

Obstructive sleep apnea (OSA) is characterized by co-occurrence with affective disorders. Our study aims to investigate the association of circadian clock gene expressions, and the presence and severity of depressive symptoms in OSA patients. The study included 184 individuals, who underwent polysomnography (PSG) and had their peripheral blood collected in the evening before and the morning after the PSG. Patients were divided into two groups: the OSA (apnea-hypopnea index (AHI) > 5) and the control group (AHI < 5). RNA was extracted from peripheral blood leukocytes. Expression levels of the selected genes (BMAL1, CLOCK, PER1, CRY1, NPAS2, and NR1D1) were assessed by qRT-PCR. Questionnaire data was collected in the morning (including the Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), Chronotype Questionnaire (CQ), and Montgomery-Åsberg Depression Rating Scale (MADRS)). The expression of all examined circadian clock genes in OSA patients was upregulated in the morning compared to the evening (except NPAS2). No differences were observed between OSA and control groups at either time point. Additionally, there was a positive correlation between the severity of depressive symptoms (assessed with MADRS) and morning expression of circadian genes in the group of OSA patients. Finally, in multivariable linear regression, ISI score (B = 0.750, p < 0.001), AM score of CQ (B = 0.416, p = 0.007), and morning PER1 gene expression (B = 4.310, p = 0.042) were found to be predictive factors for greater severity of depression symptoms in OSA patients. Dysregulated circadian clock gene expression in OSA patients is linked to depressive symptom severity, suggesting circadian disruption may underlie affective symptoms in OSA.

The dark side of apnea: altered 24-hour melatonin secretion in obstructive sleep apnea (OSAS) is disease severity dependent

PURPOSE

Melatonin aids in the synchronization of the circadian rhythm to the external environment. Few studies have tried to elucidate the relationship between melatonin and obstructive sleep apnea syndrome (OSAS). These often include few patients, do not differentiate between OSAS severity and/or do not analyse a 24-h melatonin profile. This study set out to investigate disease severity dependent differences in 24-h salivary melatonin secretion of OSAS patients compared to a reference population in a retrospective design.

METHODS

24-h salivary melatonin profiles of 169 OSAS patients were analysed (55 light, 66 moderate, 48 severe) as well as 91 reference patients. Several aspects of the melatonin curve were analysed and stratified according to OSAS severity. Parameters included: dim light melatonin onset (DLMO), time of returning below DLMO (DLMOoff), peak melatonin concentration and time, and total melatonin exposure.

RESULTS

Significant effects were corrected for confounding by age and sex using linear regression. Our analysis shows that, compared to reference and in a disease dependent manner, OSAS patients have a significantly lower 24-h melatonin curve, lower melatonin peak concentration, lower total melatonin exposure and a smaller proportion of patients reach DLMO. The differences in peak melatonin production and total melatonin exposure were resistant to confounding by age and/or sex.

CONCLUSION

This study describes clear OSAS severity dependent abnormalities in melatonin production in OSAS patients, independent of sex and/or age. Future research should indicate whether oral melatonin supplementation has beneficial effects in OSAS patients with attenuated endogenous melatonin production.

To observe the clinical effect of lipoic acid combined with continuous positive airway pressure ventilation in treating obstructive sleep apnea-hypopnea syndrome and its effect on peripheral blood γ-aminobutyric acid and melatonin levels

BACKGROUND

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common respiratory disease with potential lethality. At present, the commonly used treatment method is continuous positive airway pressure ventilation, but with the prolongation of the course of the disease, the effect of single ventilation on the improvement of oxidative stress levels is not good. Lipoic acid is a commonly used antioxidant in clinics. In this paper, lipoic acid combined with continuous positive airway pressure ventilation is used to explore whether it has a better therapeutic effect on patients.

AIM

To probe into the clinical efficacy of lipoic acid combined with continuous positive airway pressure ventilation in the therapy of OSAHS.

METHODS

82 patients with OSAHS who were cured in our hospital from March 2021 to September 2022 were prospectively collected as subjects. Based on different treatment methods, patients were grouped into a control group (43 cases) and an observation group (39 cases). The control group was treated with continuous positive airway pressure (CPAP), and the observation group was treated with lipoic acid based on control group. The therapeutic effects were measured by apnea hypopnea index (AHI), oxygen saturation (SpO2), mean oxygen saturation (MSpO2), serum malondialdehyde (MDA), superoxide dismutase (SOD), hypoxia inducible factor-1α (HIF-1α) levels, peripheral blood γ-aminobutyric acid, melatonin levels.

RESULTS

The clinical effectiveness of the observation group was better (P < 0.05). After treatment, AHI, the levels of MDA and HIF-1α in the observation group were lower and SpO2, MSpO2 and the level of SOD, γ- aminobutyric acid, and melatonin were higher than those in the control group (P < 0.05). The levels of γ- aminobutyric acid and melatonin were negatively correlated with the severity of symptoms, ESS, and AIS scores (P < 0.05).

CONCLUSIONS

The clinical effect of lipoic acid combined with CPAP in the treatment of OSAHS is better, and it has a positive effect on the levels of γ-aminobutyric acid and melatonin in peripheral blood. Lipoic acid was added to the original method for treatment, and the therapeutic effect was greatly improved.

The role of the SIRT1-BMAL1 pathway in regulating oxidative stress in the early development of ischaemic stroke

Oxidative stress is the primary cause of ischaemic stroke and is closely related to circadian rhythm. However, the mechanism by which circadian rhythm regulates oxidative stress in ischaemic stroke remains elusive. The Silent Information Regulator 1 (SIRT1) controls circadian rhythm by activating the transcription of the circadian clock core protein Basic Helix-Loop-Helix ARNT Like 1 (BMAL1) through deacetylation. Studies have shown that the SIRT1-BMAL1 pathway can regulate oxidative stress. To investigate its correlation with oxidative stress, we examined the expression levels and influencing factors of SIRT1-BMAL1 at different times in ischaemic stroke patients and analyzed their clinical indexes, oxidative stress, and inflammatory factor indicators. The expression levels of oxidative stress and inflammatory factor indicators, including malondialdehyde (MDA), superoxide dismutase (SOD), interleukin-6 (IL-6), and tumor necrosis factor-a (TNF-α), SIRT1, and BMAL1, were detected in ischaemic stroke patients within 4.5 h of onset and in non-stroke patients. Patients were divided into four subgroups based on onset time: subgroup 1 (0:00-05:59); subgroup 2 (06:00-11:59); subgroup 3 (12:00-17: 59); and subgroup 4 (18:00-23:59). Our results showed higher MDA, IL-6, and TNF-α levels, and lower SOD, SIRT1, and BMAL1 levels in ischaemic stroke patients compared to control patients (P < 0.05). Among the four subgroups, the content of MDA, IL-6, and TNF-α was highest in patients with ischaemic stroke onset from subgroup 2 (06:00-11:59), while the expression levels of SOD, BMAL1, and SIRT1 were lowest in patients with ischaemic stroke in subgroup 2. Additionally, myeloperoxidase (MPO) reached the highest value showing the same trends consistent with MDA, IL-6, and TNF-ɑ and opposite trends consistent with SOD, BMAL1, and SIRT1. However, triglycerides (TGs), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), immediate blood glucose, immediate diastolic blood pressure, immediate systolic blood pressure, and homocysteine (HCY) did not show any statistically significant circadian rhythm changes (P > 0.05). Our findings suggest that the SIRT1-BMAL1 pathway may be involved in early oxidative stress in ischaemic stroke, which may be related to MPO.

Designing and Developing a Vision-Based System to Investigate the Emotional Effects of News on Short Sleep at Noon: An Experimental Case Study

Background: Sleep is a critical factor in maintaining good health, and its impact on various diseases has been recognized by scientists. Understanding sleep patterns and quality is crucial for investigating sleep-related disorders and their potential links to health conditions. The development of non-intrusive and contactless methods for analyzing sleep data is essential for accurate diagnosis and treatment. Methods: A novel system called the sleep visual analyzer (VSleep) was designed to analyze sleep movements and generate reports based on changes in body position angles. The system utilized camera data without requiring any physical contact with the body. A Python graphical user interface (GUI) section was developed to analyze body movements during sleep and present the data in an Excel format. To evaluate the effectiveness of the VSleep system, a case study was conducted. The participants' movements during daytime naps were recorded. The study also examined the impact of different types of news (positive, neutral, and negative) on sleep patterns. Results: The system successfully detected and recorded various angles formed by participants' bodies, providing detailed information about their sleep patterns. The results revealed distinct effects based on the news category, highlighting the potential impact of external factors on sleep quality and behaviors. Conclusions: The sleep visual analyzer (VSleep) demonstrated its efficacy in analyzing sleep-related data without the need for accessories. The VSleep system holds great potential for diagnosing and investigating sleep-related disorders. The proposed system is affordable, easy to use, portable, and a mobile application can be developed to perform the experiment and prepare the results.

Obstructive sleep apnea in a mouse model is associated with tissue-specific transcriptomic changes in circadian rhythmicity and mean 24-hour gene expression

Intermittent hypoxia (IH) is a major clinical feature of obstructive sleep apnea (OSA). The mechanisms that become dysregulated after periods of exposure to IH are unclear, particularly in the early stages of disease. The circadian clock governs a wide array of biological functions and is intimately associated with stabilization of hypoxia-inducible factors (HIFs) under hypoxic conditions. In patients, IH occurs during the sleep phase of the 24-hour sleep-wake cycle, potentially affecting their circadian rhythms. Alterations in the circadian clock have the potential to accelerate pathological processes, including other comorbid conditions that can be associated with chronic, untreated OSA. We hypothesized that changes in the circadian clock would manifest differently in those organs and systems known to be impacted by OSA. Using an IH model to represent OSA, we evaluated circadian rhythmicity and mean 24-hour expression of the transcriptome in 6 different mouse tissues, including the liver, lung, kidney, muscle, heart, and cerebellum, after a 7-day exposure to IH. We found that transcriptomic changes within cardiopulmonary tissues were more affected by IH than other tissues. Also, IH exposure resulted in an overall increase in core body temperature. Our findings demonstrate a relationship between early exposure to IH and changes in specific physiological outcomes. This study provides insight into the early pathophysiological mechanisms associated with IH.

Integrative Analysis and Experimental Validation of Competing Endogenous RNAs in Obstructive Sleep Apnea

Background: Obstructive sleep apnea (OSA) is highly prevalent yet underdiagnosed. This study aimed to develop a predictive signature, as well as investigate competing endogenous RNAs (ceRNAs) and their potential functions in OSA. Methods: The GSE135917, GSE38792, and GSE75097 datasets were collected from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) database. Weighted gene correlation network analysis (WGCNA) and differential expression analysis were used to identify OSA-specific mRNAs. Machine learning methods were applied to establish a prediction signature for OSA. Furthermore, several online tools were used to establish the lncRNA-mediated ceRNAs in OSA. The hub ceRNAs were screened using the cytoHubba and validated by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Correlations between ceRNAs and the immune microenvironment of OSA were also investigated. Results: Two gene co-expression modules closely related to OSA and 30 OSA-specific mRNAs were obtained. They were significantly enriched in the antigen presentation and lipoprotein metabolic process categories. A signature that consisted of five mRNAs was established, which showed a good diagnostic performance in both independent datasets. A total of twelve lncRNA-mediated ceRNA regulatory pathways in OSA were proposed and validated, including three mRNAs, five miRNAs, and three lncRNAs. Of note, we found that upregulation of lncRNAs in ceRNAs could lead to activation of the nuclear factor kappa B (NF-κB) pathway. In addition, mRNAs in the ceRNAs were closely correlated to the increased infiltration level of effector memory of CD4 T cells and CD56bright natural killer cells in OSA. Conclusions: In conclusion, our research opens new possibilities for diagnosis of OSA. The newly discovered lncRNA-mediated ceRNA networks and their links to inflammation and immunity may provide potential research spots for future studies.

Is obstructive sleep apnea a circadian rhythm disorder?

Obstructive sleep apnea is the most common sleep-related breathing disorder worldwide and remains underdiagnosed. Its multiple associated comorbidities contribute to a decreased quality of life and work performance as well as an increased risk of death. Standard treatment seems to have limited effects on cardiovascular and metabolic aspects of the disease, emphasising the need for early diagnosis and additional therapeutic approaches. Recent evidence suggests that the dysregulation of circadian rhythms, processes with endogenous rhythmicity that are adjusted to the environment through various cues, is involved in the pathogenesis of comorbidities. In patients with obstructive sleep apnea, altered circadian gene expression patterns have been demonstrated. Obstructive respiratory events may promote circadian dysregulation through the effects of sleep disturbance and intermittent hypoxia, with subsequent inflammation and disruption of neural and hormonal homeostasis. In this review, current knowledge on obstructive sleep apnea, circadian rhythm regulation, and circadian rhythm sleep disorders is summarised. Studies that connect obstructive sleep apnea to circadian rhythm abnormalities are critically evaluated. Furthermore, pathogenetic mechanisms that may underlie this association, most notably hypoxia signalling, are presented. A bidirectional relationship between obstructive sleep apnea and circadian rhythm dysregulation is proposed. Approaching obstructive sleep apnea as a circadian rhythm disorder may prove beneficial for the development of new, personalised diagnostic, therapeutic and prognostic tools. However, further studies are needed before the clinical approach to obstructive sleep apnea includes targeting the circadian system.

Molecular characterization of the circadian clock in paediatric leukaemia patients: a prospective study protocol

BACKGROUND

In many organisms, including humans, the timing of cellular processes is regulated by the circadian clock. At the molecular level the core-clock consists of transcriptional-translational-feedback loops including several genes such as BMAL1, CLOCK, PERs and CRYs generating circa 24-h rhythms in the expression of about 40% of our genes across all tissues. Previously these core-clock genes have been shown to be differentially expressed in various cancers. Albeit a significant effect in treatment optimization of chemotherapy timing in paediatric acute lymphoblastic leukaemia has previously been reported, the mechanistic role played by the molecular circadian clock in acute paediatric leukaemia remains elusive.

METHODS

To characterize the circadian clock, we will recruit patients with newly diagnosed leukaemia and collect time course saliva and blood samples, as well as a single bone marrow sample. From the blood and bone marrow samples nucleated cells will be isolated and further undergo separation into CD19⁺ and CD19^- cells. qPCR is performed on all samples targeting the core-clock genes including BMAL1, CLOCK, PER2 and CRY1. Resulting data will be analysed for circadian rhythmicity using the RAIN algorithm and harmonic regression.

DISCUSSION

To the best of our knowledge this is the first study aiming to characterize the circadian clock in a cohort of paediatric patients with acute leukaemia. In the future we hope to contribute to uncovering further vulnerabilities of cancers associated with the molecular circadian clock and in particular adjust chemotherapy accordingly, leading to more targeted toxicity, and hence decreased systemic toxicities.

Toward Precision Medicine: Circadian Rhythm of Blood Pressure and Chronotherapy for Hypertension - 2021 NHLBI Workshop Report

Healthy individuals exhibit blood pressure variation over a 24-hour period with higher blood pressure during wakefulness and lower blood pressure during sleep. Loss or disruption of the blood pressure circadian rhythm has been linked to adverse health outcomes, for example, cardiovascular disease, dementia, and chronic kidney disease. However, the current diagnostic and therapeutic approaches lack sufficient attention to the circadian rhythmicity of blood pressure. Sleep patterns, hormone release, eating habits, digestion, body temperature, renal and cardiovascular function, and other important host functions as well as gut microbiota exhibit circadian rhythms, and influence circadian rhythms of blood pressure. Potential benefits of nonpharmacologic interventions such as meal timing, and pharmacologic chronotherapeutic interventions, such as the bedtime administration of antihypertensive medications, have recently been suggested in some studies. However, the mechanisms underlying circadian rhythm-mediated blood pressure regulation and the efficacy of chronotherapy in hypertension remain unclear. This review summarizes the results of the National Heart, Lung, and Blood Institute workshop convened on October 27 to 29, 2021 to assess knowledge gaps and research opportunities in the study of circadian rhythm of blood pressure and chronotherapy for hypertension.

The role of artificial intelligence in the treatment of obstructive sleep apnea

BACKGROUND

The first-line and most common treatment for obstructive sleep apnea is nasal continuous positive airway pressure, which serves as a pneumatic splint to stabilize the upper airway and is effective when used with appropriate adherence. Continuous positive airway pressure compliance rates remain significantly low despite machine improvements and compliance intervention. Other treatment options include oral appliances, myofunctional therapy, and surgery. The aim of this project is to elucidate the role of artificial intelligence within improving the treatment of obstructive sleep apnea.

METHODS

Related publications between 1999 and 2022 were reviewed from PubMed and Embase databases utilizing search terms "artificial intelligence," "machine learning," "obstructive sleep apnea," and "treatment." Both authors independently screened the results by title/abstract then by full text review. 126 non-duplicate articles were screened, 38 articles were included after title and abstract screen and 30 articles were included after full text review. The inclusion criteria are outline in the PICO framework and involved studies focused on artificial intelligence application in guiding and evaluating obstructive sleep apnea treatment. Non-English articles were excluded.

RESULTS

The role of artificial intelligence in the treatment of OSA was categorized into the following sections: Predicting treatment outcomes of various treatment options, Improving/Evaluating treatment, and Personalizing treatment with improving understanding of underlying mechanisms of OSA.

CONCLUSIONS

Artificial intelligence has the capacity to improve the treatment of OSA through predicting outcomes of treatment options, evaluating the treatment the patient is currently utilizing and increasing understanding of the mechanisms that contribute to OSA disease process and physiology. Implementing AI in guiding treatment decisions allows patients to connect with treatment methods that would be most effective on an individual basis.

Linking dietary intake, circadian biomarkers, and clock genes on obesity: A study protocol

Background

The prevalence of obesity continues to rise, and although this is a complex disease, the screening is made simply with the value of the Body Mass Index. This index only considers weight and height, being limited in portraying the multiple existing obesity phenotypes. The characterization of the chronotype and circadian system as an innovative phenotype of a patient's form of obesity is gaining increasing importance for the development of novel and pinpointed nutritional interventions.

Objective

The present study is a prospective observational controlled study conducted in Portugal, aiming to characterize the chronotype and determine its relation to the phenotype and dietary patterns of patients with obesity and healthy participants.

Methods

Adults with obesity (study group) and healthy adults (control group), aged between 18 and 75, will be enrolled in this study. Data will be collected to characterize the chronotype, dietary intake, and sleep quality through validated questionnaires. Body composition will also be assessed, and blood samples will be collected to quantify circadian and metabolic biomarkers.

Discussion

This study is expected to contribute to a better understanding of the impact of obesity and dietary intake on circadian biomarkers and, therefore, increase scientific evidence to help future therapeutic interventions based on chronobiology, with a particular focus on nutritional interventions.

Circadian clock disruptions link oxidative stress and systemic inflammation to metabolic syndrome in obstructive sleep apnea patients

Objectives: Obstructive sleep apnea (OSA) is an independent risk factor for metabolic syndrome (MetS). Recent studies have indicated that circadian clock genes were dysregulated in OSA. In addition, it is clear that the impairment of circadian clocks drives the progression of MetS. Therefore, we hypothesized that circadian rhythm disruption links OSA with MetS.

Methods: A total of 118 participants, who underwent polysomnography (PSG) and were diagnosed as healthy snorers (control, n = 29) or OSA (n = 89) patients based on the apnea–hypopnea index (AHI), were enrolled in the present study. General information, anthropometric data, blood biochemical indicators, clock gene expressions, and levels of oxidative and inflammatory indicators were collected, determined, and compared in all the participants.

Results: We found that Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and Differentiated embryo chondrocyte 1 (Dec1) were upregulated, while Period 1 (Per1) was reduced in OSA patients. In addition, these changing trends were closely associated with the hypoxia indicator of AHI and have a significant impact on the presence of MetS components, such as hyperglycemia (Dec1 and Per1, p &lt; 0.05 and 0.001, respectively), hypertension (Bmal1 and Dec1, p &lt; 0.001 and 0.01, respectively), hyperlipidemia (Dec1, p &lt; 0.01), and obesity (Dec1, p &lt; 0.05). Notably, expressions of Dec1 correlated with IR and predicted the presence of MetS in OSA patients. Finally, we also observed that Dec1 expression was interrelated with levels of both oxidative indicators and inflammatory biomarkers (IL-6) in OSA.

Conclusion: This study concluded that circadian clock disruptions, especially Dec1, link OSA with MetS in an oxidative and inflammatory-related manner. Circadian clock Dec1 can be used as a specific biomarker (p &lt; 0.001) and therapeutic target in OSA combined with Mets patients.

Melatonin treatment improves ventricular conduction via upregulation of Nav1.5 channel proteins and sodium current in the normal rat heart

Melatonin treatment was reported to reduce the risk of cardiac arrhythmias, and crucial for this antiarrhythmic action was the effect of melatonin on activation spread. The aim of the present study was evaluation of the mechanisms of this activation enhancement. Experiments were performed in a total of 123 control and melatonin-treated (10 mg/kg, daily, for 7 days) male Wistar rats. In epicardial mapping studies (64 leads, interlead distance 0.5 mm) in the anesthetized animals, activation times (ATs) were determined in each lead as dV/dt minimum during QRS complex under sinus rhythm. Epicardial pacing was performed to measure conduction velocity (CV) across the mapped area. Average left ventricular ATs were shorter in the treated animals as compared to the controls, whereas the minimal epicardial ATs indicating the duration of activation propagation via the ventricular conduction system did not differ between the groups. CV was higher in the treated groups indicating that melatonin affected conduction via contractile myocardium The area of Cx43-derived fluorescence, as well as the expression of Cx43 protein, was similar in ventricles in the control and melatonin-treated groups. Expression of Gja1 gene transcripts encoding Cx43, was increased in the last group. An uncoupling agent octanol modified myocardial conduction properties (time of activation, action potential upstroke velocity, passive electrotonic phase duration) similarly in both groups. On the other hand, the expression of both Scn5a gene transcripts encoding Nav1.5 proteins, as well as peak density of transmembrane sodium current were increased in the ventricular myocytes from the melatonin-treated animals. Thus, a week-long melatonin treatment caused the increase of conduction velocity via enhancement of sodium channel proteins expression and increase of sodium current in the ventricular myocytes.

Changes in cortisol levels by continuous positive airway pressure in patients with obstructive sleep apnoea: Meta-analysis of 637 individuals

BACKGROUND

Obesity, obstructive sleep apnoea (OSA) and hypertension frequently coexist and are associated with elevated cortisol levels. Identification and treatment of such patients is important when investigating for suspected Cushing's syndrome and hypertension. Studies of the impact of continuous positive airway pressure (CPAP) on cortisol and blood pressure are limited by the small sample size and show conflicting findings. We conducted a meta-analysis to document changes in the levels of cortisol and blood pressure in response to CPAP treatment of OSA.

METHODS

Meta-analysis was conducted using RevMan (v5.3) and expressed in standardized mean difference (SMD) for catecholamines and mean difference for systolic (SBP) and diastolic blood pressure (DBP). The quality of the studies was evaluated using standard tools for assessing the risk of bias.

RESULTS

A total of 22 studies met our search criteria; they consisted of 16 prospective cohort studies (PCS) that recruited 385 participants and six randomized control trials (RCT) totalling 252 participants. The range of mean age was 41-62 years and BMI 27.2-35.1 kg/m² . CPAP treatment reduced plasma cortisol levels in PCS: SMD = -0.28 [95% confidence interval (95% CI) = -0.45 to -0.12], I²  = 0%, p = .79 and in RCT: SMD = -0.39 (95% CI = -0.75 to -0.03), I²  = 28.3%, p = .25. CPAP treatment reduced SBP by 5.4 mmHg (95% CI = 1.7-9.1) and DBP by 3.3 mmHg (95% CI = 1.0-5.7). Interstudy heterogeneity was low for all studies. Bias in most RCT arose from the lack of blinding of participants and personnel.

CONCLUSION

CPAP treatment in individuals with OSA reduces cortisol levels and blood pressure.

Circadian Biology in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a complex process that can lead to the dysregulation of the molecular clock, as well as 24 h rhythms of sleep and wake, blood pressure, and other associated biological processes. Previous work has demonstrated crosstalk between the circadian clock and hypoxia-responsive pathways. However, even in the absence of OSA, disrupted clocks can exacerbate OSA-associated outcomes (e.g., cardiovascular or cognitive outcomes). As we expand our understanding of circadian biology in the setting of OSA, this information could play a significant role in the diagnosis and treatment of OSA. Here, we summarize the pre-existing knowledge of circadian biology in patients with OSA and examine the utility of circadian biomarkers as alternative clinical tools.