Circadian Rhythms, Disease and Chronotherapy

Bmal1-Mediated Circadian MELK Expression Potentiates MELK Inhibitor Chronotherapy for Esophageal Cancer

Esophageal squamous cell carcinoma (ESCC) remains a global health challenge. Circadian clock and maternal embryonic leucine zipper kinase (MELK) play a key role in tumorigenesis. However, a link between circadian clock dysregulation and MELK function in the occurrence and development of ESCC remains elusive. Here, In the in vivo and in vitro systems, we found for the first time that MELK exhibits pronounced circadian rhythms expression in mice esophageal tissue, xenograft model, and human ESCC cells. The diurnal differences expression between peak (ZT0) and trough (ZT12) points in normal esophageal tissue is nearly 10-fold. Circadian expression of MELK in ESCC cells was regulated by Bmal1 through binding to the MELK promoter. Supporting this, the levels of MELK were increased significantly in patients with ESCC and were accompanied by altered expression of core clock genes, especially, since Bmal1 is prominently upregulated. Most importantly, Bmal1-deleted eliminated the rhythmic expression of MELK, whereas the knockdown of other core genes had no effect on MELK expression. Furthermore, in nude mice with transplanted tumors, the anticancer effect of OTS167 at ZT0 administration is twice that of ZT12. Implications: Our findings suggest that MELK represents a therapeutic target, and can as a regulator of circadian control ESCC growth, with these findings advance our understanding of the clinical potential of chronotherapy and the importance of time-based MELK inhibition in cancer treatment.

Rhythm is essential: Unraveling the relation between the circadian clock and cancer

Physiological processes such as the sleep-wake cycle, metabolism, hormone secretion, neurotransmitter release, sensory capabilities, and a variety of behaviors, including sleep, are controlled by a circadian rhythm adapted to 24-hour day-night periodicity. Disruption of circadian rhythm may lead to the risks of numerous diseases, including cancers. Several epidemiological and clinical data reveal a connection between the disruption of circadian rhythms and cancer. On the contrary, oncogenic processes may suppress the homeostatic balance imposed by the circadian clock. The integration of circadian biology into cancer research offers new options for making cancer treatment more effective, and the pharmacological modulation of core clock genes is a new approach in cancer therapy. This review highlights the role of the circadian clock in tumorigenesis, how clock disruption alters the tumor microenvironment, and discusses how pharmacological modulation of circadian clock genes can lead to new therapeutic options.

Core Molecular Clock Factors Regulate Osteosarcoma Stem Cell Survival and Behavior via CSC/EMT Pathways and Lipid Droplet Biogenesis

The circadian clock, an intrinsic 24 h cellular timekeeping system, regulates fundamental biological processes, including tumor physiology and metabolism. Cancer stem cells (CSCs), a subpopulation of cancer cells with self-renewal and tumorigenic capacities, are implicated in tumor initiation, recurrence, and metastasis. Despite growing evidence for the circadian clock's involvement in regulating CSC functions, its precise regulatory mechanisms remain largely unknown. Here, using a human osteosarcoma (OS) model (143B), we have shown that core molecular clock factors are critical for OS stem cell survival and behavior via direct modulation of CSC and lipid metabolic pathways. In single-cell-derived spheroid formation assays, 143B OS cells exhibited robust spheroid-forming capacity under 3D culture conditions. Furthermore, siRNA-mediated depletion of core clock components (i.e., BMAL1, CLOCK, CRY1/2, PER1/2)-essential positive and negative elements of the circadian clock feedback loop-significantly reduced spheroid formation in 143B CSCs isolated from in vivo OS xenografts. In contrast, knockdown of the secondary clock-stabilizing factor genes NR1D1 and NR1D2 had little effect. We also found that knockdown of BMAL1, CLOCK, or CRY1/2 markedly impaired the migration and invasion capacities of 143B CSCs. At the molecular level, silencing of BMAL1, CLOCK, or CRY1/2 distinctly altered the expression of genes associated with stem cell properties and the epithelial-mesenchymal transition (EMT) in 143B CSCs. In addition, disruption of BMAL1, CLOCK, or CRY1/2 expression significantly reduced lipid droplet formation by downregulating the expression of genes involved in lipogenesis (e.g., DGAT1, FASN, ACSL4, PKM2, CHKA, SREBP1), which are closely linked to CSC/EMT processes. Furthermore, transcriptomic analysis of human OS patient samples revealed that compared with other core clock genes, CRY1 was highly expressed in OS tumors relative to controls, and its expression exhibited strong positive correlations with patient prognosis, survival, and LD biogenesis gene expression. These findings highlight the critical role of the molecular circadian clock in regulating CSC properties and metabolism, underscoring the therapeutic potential of targeting the core clock machinery to enhance OS treatment outcomes.

Clinical Chronobiology: Circadian Rhythms in Health and Disease

Circadian rhythms (CRs) are entrainable endogenous rhythms that respond to external stimuli and regulate physiological functions. The suprachiasmatic nucleus (SCN) in the hypothalamus is the mammalian master clock that synchronizes all other tissue-specific peripheral clocks, primarily through gamma-aminobutyric acid (GABA) and vasoactive intestinal polypeptide (VIP). The SCN follows Earth's 24-hour cycle by light entrainment through the retinohypothalamic tract. At the cellular level, the core clock genes CLOCK, BMAL1, PER1-PER3, CRY1, and CRY2 regulate CRs in a negative feedback loop. The circadian disruption of the sleep-wake cycle manifests in at least six distinct clinical conditions. These are the circadian rhythm sleep-wake disorders (CRSWDs). Their diagnosis is made by history, sleep diaries, and actigraphy. Treatment involves a combination of timed light exposure, melatonin/melatonin agonists, and behavioral interventions. In addition, CR disturbances and subsequent misalignment can increase the risk of a variety of illnesses. These include infertility and menstrual irregularities as well as diabetes, obesity, fatty liver disease, and other metabolic syndromes. In addition, a disruption in the gut microbiome creates a proinflammatory environment. CR disturbances increase the risk for mood disorders, hence the utility of light-based therapies in depression. People with neurodegenerative disorders demonstrate significant disturbances in their CRs, and in their sleep-wake cycles. Circadian realignment therapies can also help decrease the symptomatic burden of these disorders. Certain epilepsy syndromes, such as juvenile myoclonic epilepsy (JME), have a circadian pattern of seizures. Circadian disturbances in epilepsy can be both the consequence and cause for breakthrough seizures. The immune system has its own CR. Disturbances in these due to shift work, for instance, can increase the risk of infections. CR disturbances can also increase the risk of cancer by impacting DNA repair, apoptosis, immune surveillance, and cell cycle regulation. Moreover, the timing of chemotherapeutic agents has been shown to increase their therapeutic impact in certain cancers.

The circadian rhythm as therapeutic target in inflammatory bowel disease

The primary objectives of the management of patients with inflammatory bowel disease (IBD) are to prevent IBD flares, prevent/delay disease progression and improve patients' quality of life. To this end, one needs to identify risk factor(s) associated with flare-ups and disease progression. We posit that disruption of circadian rhythms is one of the key factors that is associated with risk of flare-up and disease progression. This hypothesis is based on published studies that show: (1) The circadian rhythm regulates many biological processes including multiple IBD-relevant biological processes that are critical in inflammatory/immune processes such as environment/microbe interaction, microbe/host interaction, intestinal barrier integrity and mucosal immunity-all central in the pathogenesis of IBD, and (2) Circadian machinery is the primary tool for the host to interact with the environment. Circadian misalignment results in a loss of preparedness of the host to respond and adjust to the environmental changes that could make the host more vulnerable to IBD flare-ups. In this review, we first provide an overview of circadian rhythms and its role in healthy and disease states. Then we present data to support our hypothesis that: (1) IBD patients have disrupted circadian rhythms ("social jet lag") and (2) circadian misalignment and associated disrupted sleep decreases the resiliency of IBD patients resulting in microbiota dysbiosis, more disrupted intestinal barrier integrity and a more aggressive disease phenotype. We also show that circadian-directed interventions have a potential to mitigate the deleterious impact of disrupted circadian and improve IBD disease course.

The circadian clock orchestrates spermatogonial differentiation and fertilization by regulating retinoic acid signaling in vertebrates

The circadian clock generates and maintains ∼24-hour oscillations in almost all organs. The testis, however, remains mysterious, without a clear understanding of its circadian functions. Our time-series transcriptome analysis reveals more than 1000 rhythmically expressed genes in the zebrafish and mouse testes, respectively. Canonical circadian clock genes are rhythmically expressed in Sertoli cells and regulate retinoic acid (RA) production, which is also evidenced by their co-expression with RA synthesis genes in single Sertoli cells. Genetic and pharmacological manipulations and temporal desynchronization revealed that the circadian clock-regulated RA signaling synchronizes spermatogonial differentiation via zbtb16a and promotes fertilization via izumo1 in zebrafish. Our findings indicate that the testicular circadian clock contributes to reproduction in a cell-specific manner through RA signaling, highlighting circadian roles in male fertility.

Melatonin Regulates Glymphatic Function to Affect Cognitive Deficits, Behavioral Issues, and Blood-Brain Barrier Damage in Mice After Intracerebral Hemorrhage: Potential Links to Circadian Rhythms

BACKGROUND

Intracerebral hemorrhage (ICH) is a life-threatening cerebrovascular disorder with no specific pharmacological treatment. ICH causes significant behavioral deficits and cognitive impairments. Recent research suggests that circadian rhythm regulation could be a promising therapeutic strategy for ICH. Melatonin has been shown to alleviate glymphatic system (GS) dysfunction by regulating circadian rhythms, thereby improving depressive-like behaviors and postoperative sleep disorders in mice. However, its application in ICH treatment and specific mechanisms are not well understood.

METHODS

ICH models were created in 8-to-10-week-old mice using collagenase injection. Circadian rhythm modulation was tested with melatonin and luzindole. Behavioral and cognitive impairments were assessed with the modified neurological severity score, corner test, and novel object recognition test. Brain water content was measured by the dry/wet weight method, and cerebral perfusion was assessed by cerebral blood flow measurements. GS function was evaluated using RITC-dextran and Evans blue assays. Immunofluorescence and western blotting were used to analyze GS function and BBB permeability.

RESULTS

Melatonin restored GS transport after ICH, promoting hematoma and edema absorption, reducing BBB damage, and improving cognitive and behavioral outcomes. However, luzindole partially blocked these benefits and reversed the neuroprotective effects.

CONCLUSION

Melatonin and luzindole treatment affect GS function, BBB permeability, and cognitive-behavioral outcomes in mice with ICH. The underlying mechanism may involve the regulation of circadian rhythms.

Insomnia symptom severity and dynamics of arousal-related symptoms across the day

Arousal is a central component of many emotional symptoms and can contribute to insomnia. Here we assessed how the timing and fluctuating nature of arousal-related symptoms over the course of the day relate to insomnia symptom severity. In this study, 361 participants (M age = 31.9 years, 282 women, 77 men, 2 non-binary individuals) completed the Insomnia Severity Index to assess severity of insomnia symptoms, followed by repeated ratings of anxiety or nervousness, stress, sleepiness, and feeling down via their mobile phone between ~08:00 hours and 00:00 hours across 1 day. Measures of dynamics included: mean levels across the day; variation (standard deviation); instability (mean squared successive differences); and resistance to change/inertia (first-order autocorrelation). Time-of-day patterns were modelled using generalized additive mixed effects models. Insomnia symptom severity (mean Insomnia Severity Index = 9.1, SD = 5.2, range 0-25) was associated with higher mean levels of all arousal-related symptoms, and increased instability and variation throughout the day in anxiety or nervousness, stress, and feeling down. Resistance to change (inertia) was not associated with insomnia symptom severity. Generalized additive mixed effects analyses showed that while individuals with more severe insomnia symptoms had elevated symptoms across the entire day, they were especially more anxious or nervous and sleepy in the early morning (~08:00 hours), anxious or nervous, stressed and sleepy in the late afternoon/early evening (~16:00 hours-21:00 hours), and anxious or nervous and stressed in the late evening (~22:00 hours). Remarkably, higher arousal occurred in the presence of high subjective sleepiness. Together these results indicate that insomnia symptom severity is associated with problems with daytime and evening arousal regulation.

Circadian gating: concepts, processes, and opportunities

Circadian clocks provide a biological measure of time that coordinates metabolism, physiology and behaviour with 24 h cycles in the environment. Circadian systems have a variety of characteristic properties, such as entrainment to environmental cues, a self-sustaining rhythm of about 24 h and temperature compensation of the circadian rhythm. In this perspective, we discuss the process of circadian gating, which refers to the restriction of a biological event to particular times of day by the circadian clock. We introduce principles and processes associated with circadian gating in a variety of organisms, including some associated mechanisms. We highlight socioeconomic opportunities presented by the investigation of circadian gating, using selected examples from circadian medicine and agricultural crop production to illustrate its importance.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

Update on the roles of regular daily rhythms in combating brain tumors

An endogenous time-keeping system found in all kingdoms of life, the endogenous circadian clock, is the source of the essential cyclic change mechanism known as the circadian rhythm. The primary circadian clock that synchronizes peripheral circadian clocks to the proper phase is housed in the anterior hypothalamus's suprachiasmatic nuclei (SCN), which functions as a central pacemaker. According to many epidemiological studies, many cancer types, especially brain tumors, have shown evidence of dysregulated clock gene expression, and the connection between clock and brain tumors is highly specific. In some studies, it is reported that the treatment administered in the morning has been linked to prolonged survival for brain cancer patients, and drug sensitivity and gene expression in gliomas follow daily rhythms. These results suggest a relationship between the circadian rhythm and the onset and spread of brain tumors, while further accumulation of research evidence will be needed to establish definitely these positive outcomes as well as to determine the mechanism underlying them. Chronotherapy provides a means of harnessing current medicines to prolong patients' lifespans and improve their quality of life, indicating the significance of circadian rhythm in enhancing the design of future patient care and clinical trials. Moreover, it is implicated that chronobiological therapy target may provide a significant challenge that warrants extensive effort to achieve. This review examines evidence of the relationship of circadian rhythm with glioma molecular pathogenesis and summarizes the mechanisms and drugs implicated in this disease.

Chronobiology in Paediatric Neurological and Neuropsychiatric Disorders: Harmonizing Care with Biological Clocks

Background: Chronobiology has gained attention in the context of paediatric neurological and neuropsychiatric disorders, including migraine, epilepsy, autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and post-traumatic stress disorder (PTSD). Disruptions in circadian rhythms are associated with key symptoms such as sleep disturbances, mood dysregulation, and cognitive impairments, suggesting a potential for chronobiology-based therapeutic approaches. Methods: This narrative review employs a systematic approach to identify relevant studies through searches of three major scientific databases, NCBI/PubMed, ScienceDirect, and Scopus, up to July 2024. We used a combination of broad and condition-specific keywords, such as "chronobiology", "biorhythm", "pediatric", "epilepsy", "ADHD", and "ASD", among others. Articles in English that focused on clinical features, treatments, or outcomes related to circadian rhythms in paediatric populations were included, while non-peer-reviewed articles and studies lacking original data were excluded. Rayyan software was used for article screening, removing duplicates, and facilitating consensus among independent reviewers. Results: A total of 87 studies were included in the analysis. Findings reveal a consistent pattern of circadian rhythm disruptions across the disorders examined. Specifically, dysregulation of melatonin and cortisol secretion is observed in children with ASD, ADHD, and PTSD, with altered circadian timing contributing to sleep disturbances and mood swings. Alterations in core clock genes (CLOCK, BMAL1, PER, and CRY) were also noted in children with epilepsy, which was linked to seizure frequency and timing. Chronotherapy approaches showed promise in managing these disruptions: melatonin supplementation improved sleep quality and reduced ADHD symptoms in some children, while light therapy proved effective in stabilizing sleep-wake cycles in ASD and ADHD patients. Additionally, behaviour-based interventions, such as the Early Start Denver Model, showed success in improving circadian alignment in children with ASD. Conclusions: This review highlights the significant role of circadian rhythm disruptions in paediatric neurological and neuropsychiatric disorders, with direct implications for treatment. Chronobiology-based interventions, such as melatonin therapy, light exposure, and individualized behavioural therapies, offer potential for improving symptomatology and overall functioning. The integration of chronotherapy into clinical practice could provide a paradigm shift from symptom management to more targeted, rhythm-based treatments. Future research should focus on understanding the molecular mechanisms behind circadian disruptions in these disorders and exploring personalized chronotherapeutic approaches tailored to individual circadian patterns.

Genetic synchronization of the brain and liver molecular clocks defend against chrono-metabolic disease

Nearly every cell of the body contains a circadian clock mechanism that is synchronized with the light-entrained clock in the suprachiasmatic nucleus (SCN). Desynchrony between the SCN and the external environment leads to metabolic dysfunction in shift workers. Similarly, mice with markedly shortened endogenous period due to the deletion of circadian REV-ERBα/β nuclear receptors in the SCN (SCN DKO) exhibit increased sensitivity to diet-induced obesity (DIO) on a 24 h light:dark cycle while mice with REV-ERBs deleted in hepatocytes (HepDKO) display exacerbated hepatosteatosis in response to a high-fat diet. Here, we show that inducing deletion of hepatocyte REV-ERBs in SCN DKO mice (Hep-SCN DDKO) rescued the exacerbated DIO and hepatic triglyceride accumulation, without affecting the shortened behavioral period. These findings suggest that metabolic disturbances due to environmental desynchrony with the central clock are due to effects on peripheral clocks which can be mitigated by matching peripheral and central clock periods even in a desynchronous environment. Thus, maintaining synchrony within an organism, rather than between endogenous and exogenous clocks, may be a viable target for the treatment of metabolic disorders associated with circadian disruption.

The effect of sleep and shift work on the primary immune response to messenger RNA-based COVID-19 vaccination

Shift work can cause circadian misalignment, which often results in sleeping problems and has been associated with immune dysfunction. To better understand the impact of shift work on a primary immune response to vaccination, we compared severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-specific humoral and cellular immune responses after one injection of the messenger RNA (mRNA)-1273 vaccine between day workers (n = 24) and night shift workers (n = 21). In addition, duration and quality of sleep were assessed for a period of 7 days around the time of vaccination using actigraphy and daily sleep diaries, and their relationship with immunogenicity of mRNA-1273 vaccination was studied. We found that median total sleep time on the 2 days immediately after vaccination, which coincided with the days that night shift workers worked night shifts, was significantly lower in night shift workers (342 and 318 min) than day workers (431 and 415 min) (both p < 0.001). There was no difference in sleep quality between day workers and night shift workers. Furthermore, no difference in the antibody response between the two groups was observed, yet night shift workers had a significantly higher virus-specific T-cell response than day workers 28 days after immunisation (p = 0.013). Multivariate regression analysis showed no association between sleep duration, sleep quality and SARS-CoV-2-specific humoral or cellular immune responses. Collectively, these findings indicate that shift work-induced sleep loss and night shift work have little to no effect on the primary immune response to mRNA-based COVID-19 vaccination.

Targeting the circadian modulation: novel therapeutic approaches in the management of ASD

Circadian dysfunction is prevalent in neurodevelopmental disorders, particularly in autism spectrum disorder (ASD). A plethora of empirical studies demonstrate a strong correlation between ASD and circadian disruption, suggesting that modulation of circadian rhythms and the clocks could yield satisfactory advancements. Research indicates that circadian dysfunction associated with abnormal neurodevelopmental phenotypes in ASD individuals, potentially contribute to synapse plasticity disruption. Therefore, targeting circadian rhythms may emerge as a key therapeutic approach. In this study, we did a brief review of the mammalian circadian clock, and the correlation between the circadian mechanism and the pathology of ASD at multiple levels. In addition, we highlight that circadian is the target or modulator to participate in the therapeutic approaches in the management of ASD, such as phototherapy, melatonin, modulating circadian components, natural compounds, and chronotherapies. A deep understanding of the circadian clock's regulatory role in the neurodevelopmental phenotypes in ASD may inspire novel strategies for improving ASD treatment.

Circadian Rhythm Disruption in Cancer Survivors: From Oncogenesis to Quality of Life

BACKGROUND

Circadian rhythms are approximately 24-hour cycles in physiological and behavioral processes. They are entrained to the external solar day via blue wavelength light. Disruptions in these intrinsic rhythms can lead to circadian dysfunction, which has several negative implications on human health, including cancer development and progression.

AIMS

Here we review the molecular mechanisms of circadian disruption and their impact on tumor development and progression, discuss the interplay between circadian dysfunction and cancer in basic scientific studies and clinical data, and propose the potential clinical implications of these data that may be used to improve patient outcomes and reduce cost of treatment.

MATERIALS & METHODS

Using scientific literature databases, relevant studies were analyzed to draw overarching conclusions of the relationship between circadian rhythm dysruption and cancer.

CONCLUSIONS

Circadian disruption can be mediated by a number of environmental factors such as exposure to light at night, shift work, jetlag, and social jetlag which drive oncogenesis. Tumor growth and progression, as well as treatment, can lead to long-term alterations in circadian rhythms that negatively affect quality of life in cancer survivors.

Unraveling the Impact of Travel on Circadian Rhythm and Crafting Optimal Management Approaches: A Systematic Review

Circadian rhythms, which regulate essential physiological and behavioral processes, are crucial for maintaining overall health and well-being. However, disruptions to these rhythms, particularly due to trans-meridian travel and shift work, can lead to significant health issues, including jet lag, metabolic imbalances, and neuropsychiatric disorders. In this systematic review, conducted in line with Preferred Reporting Items for Systematic Reviews and Metanalysis (PRISMA) 2020 guidelines, we explore the effectiveness of various interventions aimed at realigning circadian rhythms disrupted by such factors. Focusing on studies published between 2020 and 2024, our search spanned databases like PubMed, Google Scholar, PubMed Central (PMC), and ScienceDirect, emphasizing randomized controlled trials (RCTs), observational studies, and comprehensive reviews. A rigorous quality assessment using the AMSTAR tool for systematic reviews and the SANRA checklist for narrative reviews was employed. Out of an initial 2153 titles, 23 high-quality studies were identified and analyzed. The findings reveal that interventions such as melatonin supplementation, personalized light exposure, and chrono-modulation can significantly improve sleep quality, reduce jet lag symptoms, and promote better health outcomes. This review highlights the critical nature of circadian alignment in preventing serious health issues, such as mental health disorders, metabolic syndromes, and even cancer. It advocates for a personalized, integrative approach that combines melatonin, light therapy, time-restricted eating, exercise, and alternative therapies like electroacupuncture. Such strategies not only facilitate smoother transitions across time zones but also contribute to overall health and resilience. Future studies should aim to assess the long-term benefits and practical applications of these interventions in broader populations.

Effect of Circadian Rhythm Modulated Blood Flow on Nanoparticle based Targeted Drug Delivery in Virtual In Vivo Arterial Geometries

Delivery of drug using nanocarriers tethered with vasculature-targeting epitopes aims to maximize the therapeutic efficacy of the drug while minimizing the drug side effects. Circadian rhythm which is governed by the central nervous system has implications for targeted drug delivery due to sleep-wake cycle changes in blood flow dynamics. This paper presents an advanced fluid dynamics modeling method that is based on viscous incompressible shear-rate fluid (blood) coupled with an advection-diffusion equation to simulate the formation of drug concentration gradients in the blood stream and buildup of concentration at the targeted site. The method is equipped with an experimentally calibrated nanoparticle-endothelial cell adhesion model that employs Robin boundary conditions to describe nanoparticle retention based on probability of adhesion, a friction model accounting for surface roughness of endothelial cell layer, and a dispersion model based on Taylor-Aris expression for effective diffusion in the boundary layer. The computational model is first experimentally validated and then tested on engineered bifurcating arterial systems where impedance boundary conditions are applied at the outflow to account for the downstream resistance at each outlet. It is then applied to a virtual geometric model of an in vivo arterial tree developed through MRI-based image processing techniques. These simulations highlight the potential of the computational model for drug transport, adhesion, and retention at multiple sites in virtual in vivo models. The model provides a virtual platform for exploring circadian rhythm modulated blood flow for targeted drug delivery while minimizing the in vivo experimentation.

Statement of Significance

A novel integration of nanoparticle-based drug delivery framework with shear-rate dependent blood flow model is presented. The framework is comprised of a unique combination of mechanics-based dispersion model, an asperity model for endothelium surface roughness, and a stochastic nanoparticle-endothelial cell adhesion model. Simulations of MRI based in vivo carotid artery system showcase the effects of vessel geometry on nanoparticle adhesion and retention at the targeted site. Vessel geometry and target site location impact nanoparticle adhesion; curved and bifurcating regions favor local accumulation of drug. It is also shown that aligning drug administration with circadian rhythm and sleep cycle can enhance the efficacy of drug delivery processes. These simulations highlight the potential of the computational modeling for exploring circadian rhythm modulated blood flow for targeted drug delivery while minimizing the in vivo experimentation.

Abnormal Histopathological Expression of Klotho, Ferroptosis, and Circadian Clock Regulators in Pancreatic Ductal Adenocarcinoma: Prognostic Implications and Correlation Analyses

Pancreatic ductal adenocarcinoma (PDAC) is an extremely lethal tumor with increasing incidence, presenting numerous clinical challenges. The histopathological examination of novel, unexplored biomarkers offers a promising avenue for research, with significant translational potential for improving patient outcomes. In this study, we evaluated the prognostic significance of ferroptosis markers (TFRC, ALOX-5, ACSL-4, and GPX-4), circadian clock regulators (CLOCK, BMAL1, PER1, PER2), and KLOTHO in a retrospective cohort of 41 patients deceased by PDAC. Immunohistochemical techniques (IHC) and multiple statistical analyses (Kaplan-Meier curves, correlograms, and multinomial linear regression models) were performed. Our findings reveal that ferroptosis markers are directly associated with PDAC mortality, while circadian regulators and KLOTHO are inversely associated. Notably, TFRC emerged as the strongest risk marker associated with mortality (HR = 35.905), whereas CLOCK was identified as the most significant protective marker (HR = 0.01832). Correlation analyses indicate that ferroptosis markers are positively correlated with each other, as are circadian regulators, which also positively correlate with KLOTHO expression. In contrast, KLOTHO and circadian regulators exhibit inverse correlations with ferroptosis markers. Among the clinical variables examined, only the presence of chronic pathologies showed an association with the expression patterns of several proteins studied. These findings underscore the complexity of PDAC pathogenesis and highlight the need for further research into the specific molecular mechanisms driving disease progression.

The Circadian Rhythm of Itching among 241 Adults with Atopic Dermatitis: A Cross-sectional Study

The pattern of itching in patients with atopic dermatitis has not been systematically studied. Therefore, this study aimed to assess the pattern of itching in adults with atopic dermatitis using questionnaires to assess for a circadian rhythm of itching in participating patients at a single institution (n = 241). A self-report questionnaire was used to assess circadian rhythm and intensity of itching in patients. In addition, the patients' disease severity (Eczema Area and Severity Index [EASI]) and quality of life (Dermatology Life Quality Index [DLQI]) were assessed. Itching occurred most frequently (74.69%) and with the greatest severity (62.66%) between 20:00 and 00:00, and the least number of patients (25.31%) experienced itching between 04:00 and 08:00. The DLQI and EASI scores both correlated with the average and maximum itch intensity (r = 0.582, r = 0.533, respectively; r = 0.539, r = 0.517, respectively; p < 0.001). The DLQI and EASI scores were associated with average itch intensity (B = 0.179, B = 0.204, respectively; 95% CI: 0.112 to 0.246, 95% CI: 0.096 to 0.313, respectively; p < 0.001), and the EASI score was associated with males and family history (B = 0.285, B = 0.287, respectively; 95% CI: 0.094 to 0.476, 95% CI: 0.096 to 0.478, respectively; p = 0.003). Adult patients with atopic dermatitis exhibited a circadian rhythm of itching; these study results could positively impact treatment approaches.

Hypermetabolic state is associated with circadian rhythm disruption in mouse and human cancer cells

Crosstalk between metabolism and circadian rhythms is a fundamental building block of multicellular life, and disruption of this reciprocal communication could be relevant to disease. Here, we investigated whether maintenance of circadian rhythms depends on specific metabolic pathways, particularly in the context of cancer. We found that in adult mouse fibroblasts, ATP levels were a major contributor to signal from a clock gene luciferase reporter, although not necessarily to the strength of circadian cycling. In contrast, we identified significant metabolic control of circadian function across a series of pancreatic adenocarcinoma cell lines. Metabolic profiling of congenic tumor cell clones revealed substantial diversity among these lines that we used to identify clones to generate circadian reporter lines. We observed diverse circadian profiles among these lines that varied with their metabolic phenotype: The most hypometabolic line [exhibiting low levels of oxidative phosphorylation (OxPhos) and glycolysis] had the strongest rhythms, while the most hypermetabolic line had the weakest rhythms. Pharmacological enhancement of OxPhos decreased the amplitude of circadian oscillation in a subset of tumor cell lines. Strikingly, inhibition of OxPhos enhanced circadian rhythms only in the tumor cell line in which glycolysis was also low, thereby establishing a hypometabolic state. We further analyzed metabolic and circadian phenotypes across a panel of human patient-derived melanoma cell lines and observed a significant negative association between metabolic activity and circadian cycling strength. Together, these findings suggest that metabolic heterogeneity in cancer directly contributes to circadian function and that high levels of glycolysis or OxPhos independently disrupt circadian rhythms in these cells.

Circadian Control of Lipid Metabolism

To ensure optimum health and performance, lipid metabolism needs to be temporally aligned to other body processes and to daily changes in the environment. Central and peripheral circadian clocks and environmental signals such as light provide internal and external time cues to the body. Importantly, each of the key organs involved in insect lipid metabolism contains a molecular clockwork which ticks with a varying degree of autonomy from the central clock in the brain. In this chapter, we review our current knowledge about peripheral clocks in the insect fat body, gut and oenocytes, and light- and circadian-driven diel patterns in lipid metabolites and lipid-related transcripts. In addition, we highlight selected neuroendocrine signaling pathways that are or may be involved in the temporal coordination and control of lipid metabolism.

One Health: Circadian Medicine Benefits Both Non-human Animals and Humans Alike

Circadian biology's impact on human physical health and its role in disease development and progression is widely recognized. The forefront of circadian rhythm research now focuses on translational applications to clinical medicine, aiming to enhance disease diagnosis, prognosis, and treatment responses. However, the field of circadian medicine has predominantly concentrated on human healthcare, neglecting its potential for transformative applications in veterinary medicine, thereby overlooking opportunities to improve non-human animal health and welfare. This review consists of three main sections. The first section focuses on the translational potential of circadian medicine into current industry practices of agricultural animals, with a particular emphasis on horses, broiler chickens, and laying hens. The second section delves into the potential applications of circadian medicine in small animal veterinary care, primarily focusing on our companion animals, namely dogs and cats. The final section explores emerging frontiers in circadian medicine, encompassing aquaculture, veterinary hospital care, and non-human animal welfare and concludes with the integration of One Health principles. In summary, circadian medicine represents a highly promising field of medicine that holds the potential to significantly enhance the clinical care and overall health of all animals, extending its impact beyond human healthcare.

Association between time-of-day for eating, exercise, and sleep with blood pressure in adults with elevated blood pressure or hypertension: a systematic review

The purpose of this review is to synthesize results from studies examining the association between time-of-day for eating, exercise, and sleep with blood pressure (BP) in adults with elevated BP or hypertension. Six databases were searched for relevant publications from which 789 were identified. Ten studies met inclusion criteria. Four studies examined time-of-day for eating, five examined time-of-day for exercise, and one examined time-of-day for sleep and their associations with BP. Results suggested that later time-of-day for eating ( n  = 2/4) and later sleep mid-point ( n  = 1/1) were significantly related to higher BP in multivariable models, whereas morning ( n  = 3/5) and evening ( n  = 4/5) exercise were associated with significantly lower BP. Although this small body of work is limited by a lack of prospective, randomized controlled study designs and underutilization of 24 h ambulatory BP assessment, these results provide preliminary, hypothesis-generating support for the independent role of time-of-day for eating, exercise, and sleep with lower BP.

The Relationship between Circadian Rhythm and Cancer Disease

The circadian clock regulates biological cycles across species and is crucial for physiological activities and biochemical reactions, including cancer onset and development. The interplay between the circadian rhythm and cancer involves regulating cell division, DNA repair, immune function, hormonal balance, and the potential for chronotherapy. This highlights the importance of maintaining a healthy circadian rhythm for cancer prevention and treatment. This article investigates the complex relationship between the circadian rhythm and cancer, exploring how disruptions to the internal clock may contribute to tumorigenesis and influence cancer progression. Numerous databases are utilized to conduct searches for articles, such as NCBI, MEDLINE, and Scopus. The keywords used throughout the academic archives are "circadian rhythm", "cancer", and "circadian clock". Maintaining a healthy circadian cycle involves prioritizing healthy sleep habits and minimizing disruptions, such as consistent sleep schedules, reduced artificial light exposure, and meal timing adjustments. Dysregulation of the circadian clock gene and cell cycle can cause tumor growth, leading to the need to regulate the circadian cycle for better treatment outcomes. The circadian clock components significantly impact cellular responses to DNA damage, influencing cancer development. Understanding the circadian rhythm's role in tumor diseases and their therapeutic targets is essential for treating and preventing cancer. Disruptions to the circadian rhythm can promote abnormal cell development and tumor metastasis, potentially due to immune system imbalances and hormonal fluctuations.

Circadian transcriptome of pancreatic adenocarcinoma unravels chronotherapeutic targets

Pancreatic ductal adenocarcinoma (PDA) is a lethal cancer characterized by a poor outcome and an increasing incidence. A significant majority (>80%) of newly diagnosed cases are deemed unresectable, leaving chemotherapy as the sole viable option, though with only moderate success. This necessitates the identification of improved therapeutic options for PDA. We hypothesized that there are temporal variations in cancer-relevant processes within PDA tumors, offering insights into the optimal timing of drug administration - a concept termed chronotherapy. In this study, we explored the presence of the circadian transcriptome in PDA using patient-derived organoids and validated these findings by comparing PDA data from The Cancer Genome Atlas with noncancerous healthy pancreas data from GTEx. Several PDA-associated pathways (cell cycle, stress response, Rho GTPase signaling) and cancer driver hub genes (EGFR and JUN) exhibited a cancer-specific rhythmic pattern intricately linked to the circadian clock. Through the integration of multiple functional measurements for rhythmic cancer driver genes, we identified top chronotherapy targets and validated key findings in molecularly divergent pancreatic cancer cell lines. Testing the chemotherapeutic efficacy of clinically relevant drugs further revealed temporal variations that correlated with drug-target cycling. Collectively, our study unravels the PDA circadian transcriptome and highlights a potential approach for optimizing chrono-chemotherapeutic efficacy.

Twenty-four-hour physical behaviour profiles across type 2 diabetes mellitus subtypes

AIM

To investigate how 24-h physical behaviours differ across type 2 diabetes (T2DM) subtypes.

MATERIALS AND METHODS

We included participants living with T2DM, enrolled as part of an ongoing observational study. Participants wore an accelerometer for 7 days to quantify physical behaviours across 24 h. We used routinely collected clinical data (age at onset of diabetes, glycated haemoglobin level, homeostatic model assessment index of beta-cell function, homeostatic model assessment index of insulin resistance, body mass index) to replicate four previously identified subtypes (insulin-deficient diabetes [INS-D], insulin-resistant diabetes [INS-R], obesity-related diabetes [OB] and age-related diabetes [AGE]), via k-means clustering. Differences in physical behaviours across the diabetes subtypes were assessed using generalized linear models, with the AGE cluster as the reference.

RESULTS

A total of 564 participants were included in this analysis (mean age 63.6 ± 8.4 years, 37.6% female, mean age at diagnosis 53.1 ± 10.0 years). The proportions in each cluster were as follows: INS-D: n = 35, 6.2%; INS-R: n = 88, 15.6%; OB: n = 166, 29.4%; and AGE: n = 275, 48.8%. Compared to the AGE cluster, the OB cluster had a shorter sleep duration (-0.3 h; 95% confidence interval [CI] -0.5, -0.1), lower sleep efficiency (-2%; 95% CI -3, -1), lower total physical activity (-2.9 mg; 95% CI -4.3, -1.6) and less time in moderate-to-vigorous physical activity (-6.6 min; 95% CI -11.4, -1.7), alongside greater sleep variability (17.9 min; 95% CI 8.2, 27.7) and longer sedentary time (31.9 min; 95% CI 10.5, 53.2). Movement intensity during the most active continuous 10 and 30 min of the day was also lower in the OB cluster.

CONCLUSIONS

In individuals living with T2DM, the OB subtype had the lowest levels of physical activity and least favourable sleep profiles. Such behaviours may be suitable targets for personalized therapeutic lifestyle interventions.

Long-term survival, toxicities, and the role of chrono-chemotherapy with different infusion rates in locally advanced nasopharyngeal carcinoma patients treated with intensity-modulated radiation therapy: a retrospective study with a 5-year follow-up

Purpose

This study aimed to evaluate 5-year outcomes and the late toxicity profile of chrono-chemotherapy with different infusion rates in patients with locally advanced nasopharyngeal carcinoma (NPC).

Methods and materials

Our retrospective analysis included 70 patients with locally advanced NPC stages III and IVB (according to the 2010 American Joint Committee on Cancer staging system). Patients were treated with two cycles of induction chemotherapy (IC) before concurrent chemoradiotherapy (CCRT) at Guizhou Cancer Hospital. The IC with docetaxel, cisplatin (DDP) and fluorouracil regimen. Patients were divided into two groups during CCRT. Using a "MELODIE" multi-channel programmed pump, DDP (100 mg/m2) was administered for 12 hours from 10:00 am to 10:00 pm and repeated every 3 weeks for 2-3 cycles. DDP was administered at the peak period of 4:00 pm in the sinusoidal chrono-modulated infusion group (Arm A, n=35). The patients in Arm B received a constant rate of infusion. Both arms received radiotherapy through the same technique and dose fraction. The long-term survival and disease progression were observed.

Results

After a median follow-up of 82.8 months, the 5-year progression-free survival rate was 81.3% in Arm A and 79.6% in Arm B (P = 0.85). The 5-year overall survival rate was not significantly different between Arm A and Arm B (79.6% vs 85.3%, P = 0.79). The 5-year distant metastasis-free survival rate was 83.6% in Arm A and 84.6% in Arm B (P = 0.75). The 5-year local recurrence-free survival rate was 88.2% in Arm A and 85.3% in Arm B (P = 0.16). There were no late toxicities of grade 3-4 in either group. Both groups had grade 1-2 late toxicities. Dry mouth was the most common late toxic side effect, followed by hearing loss and difficulty in swallowing. There was no statistically significant difference between Arm A and Arm B in terms of side effects.

Conclusion

Long-term analysis confirmed that in CCRT, cisplatin administration with sinusoidal chrono-modulated infusion was not superior to the constant infusion rate in terms of long-term toxicity and prognosis.

Circadian Effects on Vascular Immunopathologies

Circadian rhythms exert a profound impact on most aspects of mammalian physiology, including the immune and cardiovascular systems. Leukocytes engage in time-of-day-dependent interactions with the vasculature, facilitating the emigration to and the immune surveillance of tissues. This review provides an overview of circadian control of immune-vascular interactions in both the steady state and cardiovascular diseases such as atherosclerosis and infarction. Circadian rhythms impact both the immune and vascular facets of these interactions, primarily through the regulation of chemoattractant and adhesion molecules on immune and endothelial cells. Misaligned light conditions disrupt this rhythm, generally exacerbating atherosclerosis and infarction. In cardiovascular diseases, distinct circadian clock genes, while functioning as part of an integrated circadian system, can have proinflammatory or anti-inflammatory effects on these immune-vascular interactions. Here, we discuss the mechanisms and relevance of circadian rhythms in vascular immunopathologies.

Learning from circadian rhythm to transform cancer prevention, prognosis, and survivorship care

Circadian timekeeping mechanisms and cell cycle regulation share thematic biological principles in responding to signals, repairing cellular damage, coordinating metabolism, and allocating cellular resources for optimal function. Recent studies show interactions between cell cycle regulators and circadian clock components, offering insights into potential cancer treatment approaches. Understanding circadian control of metabolism informs timing for therapies to reduce adverse effects and enhance treatment efficacy. Circadian adaptability to lifestyle factors, such as activity, sleep, and nutrition sheds light on their impact on cancer. Leveraging circadian regulatory mechanisms for cancer prevention and care is vital, as most risk stems from modifiable lifestyles. Monitoring circadian factors aids risk assessment and targeted interventions across the cancer care continuum.

Circadian immunity from bench to bedside: a practical guide

The immune system is built to counteract unpredictable threats, yet it relies on predictable cycles of activity to function properly. Daily rhythms in immune function are an expanding area of study, and many originate from a genetically based timekeeping mechanism known as the circadian clock. The challenge is how to harness these biological rhythms to improve medical interventions. Here, we review recent literature documenting how circadian clocks organize fundamental innate and adaptive immune activities, the immunologic consequences of circadian rhythm and sleep disruption, and persisting knowledge gaps in the field. We then consider the evidence linking circadian rhythms to vaccination, an important clinical realization of immune function. Finally, we discuss practical steps to translate circadian immunity to the patient's bedside.

Disruption of circadian rhythms promotes alcohol use: a systematic review

This systematic review investigates the bidirectional relationship between alcohol consumption and disrupted circadian rhythms. The goal of this study was to identify (i) the types of circadian rhythm disruptors (i.e. social jet lag, extreme chronotypes, and night shift work) associated with altered alcohol use and (ii) whether sex differences in the consequences of circadian disruption exist. We conducted a search of PubMed, Embase, and PsycINFO exclusively on human research. We identified 177 articles that met the inclusion criteria. Our analyses revealed that social jet lag and the extreme chronotype referred to as eveningness were consistently associated with increased alcohol consumption. Relationships between night shift work and alcohol consumption were variable; half of articles reported no effect of night shift work on alcohol consumption. Both sexes were included as participants in the majority of the chronotype and social jet lag papers, with no sex difference apparent in alcohol consumption. The night shift research, however, contained fewer studies that included both sexes. Not all forms of circadian disruption are associated with comparable patterns of alcohol use. The most at-risk individuals for increased alcohol consumption are those with social jet lag or those of an eveningness chronotype. Direct testing of the associations in this review should be conducted to evaluate the relationships among circadian disruption, alcohol intake, and sex differences to provide insight into temporal risk factors associated with development of alcohol use disorder.

Effect of oral melatonin treatment on insulin resistance and diurnal blood pressure variability in night shift workers. A double-blind, randomized, placebo-controlled study

BACKGROUND

Night shift work is associated with sleep disturbances, obesity, and cardiometabolic diseases. Disruption of the circadian clock system has been suggested to be an independent cause of type 2 diabetes and cardiovascular disease in shift workers. We aimed to improve alignment of circadian timing with social and environmental factors with administration of melatonin.

METHODS

In a randomized, placebo-controlled, prospective study, we analysed the effects of 2 mg of sustained-release melatonin versus placebo on glucose tolerance, insulin resistance indices, sleep quality, circadian profiles of plasma melatonin and cortisol, and diurnal blood pressure profiles in 24 rotating night shift workers during 12 weeks of treatment, followed by 12 weeks of wash-out. In a novel design, the time of melatonin administration (at night or in the morning) depended upon the shift schedule. We also compared the baseline profiles of the night shift (NS) workers with 12 healthy non-night shift (NNS)-working controls.

RESULTS

We found significantly impaired indices of insulin resistance at baseline in NS versus NNS (p < 0.05), but no differences in oral glucose tolerance tests nor in the diurnal profiles of melatonin, cortisol, or blood pressure. Twelve weeks of melatonin treatment did not significantly improve insulin resistance, nor did it significantly affect diurnal blood pressure or melatonin and cortisol profiles. Melatonin administration, however, caused a significant improvement in sleep quality which was significantly impaired in NS versus NNS at baseline (p < 0.001).

CONCLUSIONS

Rotating night shift work causes mild-to-moderate impairment of sleep quality and insulin resistance. Melatonin treatment at bedtime improves sleep quality, but does not significantly affect insulin resistance in rotating night shift workers after 12 weeks of administration.

New Awareness of the Interplay Between the Gut Microbiota and Circadian Rhythms

Circadian rhythms influence various aspects of the biology and physiology of the host, such as food intake and sleep/wake cycles. In recent years, an increasing amount of genetic and epidemiological data has shown that the light/dark cycle is the main cue that regulates circadian rhythms. Other factors, including sleep/wake cycles and food intake, have necessary effects on the composition and rhythms of the gut microbiota. Interestingly, the gut microbiota can affect the circadian rhythm of hosts in turn through contact-dependent and contact-independent mechanisms. Furthermore, the gut microbiota has been shown to regulate the sleep/wake cycles through gut-brain-microbiota interaction. In addition to diabetes, the gut microbiota can also intervene in the progression of neuro- degenerative diseases through the gut-brain-microbiota interaction, and also in other diseases such as hypertension and rheumatoid arthritis, where it is thought to have a spare therapeutic potential. Even though fecal microbiota transplantation has good potential for treating many diseases, the risk of spreading intestinal pathogens should not be ignored.

Circadian Rhythms in Cardiovascular Function: Implications for Cardiac Diseases and Therapeutic Opportunities

Circadian rhythms are internal 24-h intrinsic oscillations that are present in essentially all mammalian cells and can influence numerous biological processes. Cardiac function is known to exhibit a circadian rhythm and is strongly affected by the day/night cycle. Many cardiovascular variables, including heart rate, heart rate variability (HRV), electrocardiogram (ECG) waveforms, endothelial cell function, and blood pressure, demonstrate robust circadian rhythms. Many experiential and clinical studies have highlighted that disruptions in circadian rhythms can ultimately lead to maladaptive cardiac function. Factors that disrupt the circadian rhythm, including shift work, global travel, and sleep disorders, may consequently enhance the risk of cardiovascular diseases. Some cardiac diseases appear to occur at particular times of the day or night; therefore, targeting the disease at particular times of day may improve the clinical outcome. The objective of this review is to unravel the relationship between circadian rhythms and cardiovascular health. By understanding this intricate interplay, we aim to reveal the potential risks of circadian disruption and discuss the emerging therapeutic strategies, specifically those targeting circadian rhythms. In this review, we explore the important role of circadian rhythms in cardiovascular physiology and highlight the role they play in cardiac dysfunction such as ventricular hypertrophy, arrhythmia, diabetes, and myocardial infarction. Finally, we review potential translational treatments aimed at circadian rhythms. These treatments offer an innovative approach to enhancing the existing approaches for managing and treating heart-related conditions, while also opening new avenues for therapeutic development.

Hypermetabolic state is associated with circadian rhythm disruption in mouse and human cancer cells

Crosstalk between cellular metabolism and circadian rhythms is a fundamental building block of multicellular life, and disruption of this reciprocal communication could be relevant to degenerative disease, including cancer. Here, we investigated whether maintenance of circadian rhythms depends upon specific metabolic pathways, particularly in the context of cancer. We found that in adult mouse fibroblasts, ATP levels were a major contributor to overall levels of a clock gene luciferase reporter, although not necessarily to the strength of circadian cycling. In contrast, we identified significant metabolic control of circadian function in an in vitro mouse model of pancreatic adenocarcinoma. Metabolic profiling of a library of congenic tumor cell clones revealed significant differences in levels of lactate, pyruvate, ATP, and other crucial metabolites that we used to identify candidate clones with which to generate circadian reporter lines. Despite the shared genetic background of the clones, we observed diverse circadian profiles among these lines that varied with their metabolic phenotype: the most hypometabolic line had the strongest circadian rhythms while the most hypermetabolic line had the weakest rhythms. Treatment of these tumor cell lines with bezafibrate, a peroxisome proliferator-activated receptor (PPAR) agonist shown to increase OxPhos, decreased the amplitude of circadian oscillation in a subset of tumor cell lines. Strikingly, treatment with the Complex I antagonist rotenone enhanced circadian rhythms only in the tumor cell line in which glycolysis was also low, thereby establishing a hypometabolic state. We further analyzed metabolic and circadian phenotypes across a panel of human patient-derived melanoma cell lines and observed a significant negative association between metabolic activity and circadian cycling strength. Together, these findings suggest that metabolic heterogeneity in cancer directly contributes to circadian function, and that high levels of glycolysis or OxPhos independently disrupt circadian rhythms in these cells.

Improving Sleep Quality, Daytime Sleepiness, and Cognitive Function in Patients with Dementia by Therapeutic Exercise and NESA Neuromodulation: A Multicenter Clinical Trial

Dementia is a progressive decline in cognitive functions caused by an alteration in the pattern of neural network connections. There is an inability to create new neuronal connections, producing behavioral disorders. The most evident alteration in patients with neurodegenerative diseases is the alteration of sleep-wake behavior. The aim of this study was to test the effect of two non-pharmacological interventions, therapeutic exercise (TE) and non-invasive neuromodulation through the NESA device (NN) on sleep quality, daytime sleepiness, and cognitive function of 30 patients diagnosed with dementia (non-invasive neuromodulation experimental group (NNG): mean ± SD, age: 71.6 ± 7.43 years; therapeutic exercise experimental group (TEG) 75.2 ± 8.63 years; control group (CG) 80.9 ± 4.53 years). The variables were evaluated by means of the Pittsburg Index (PSQI), the Epworth Sleepiness Scale (ESS), and the Mini-Cognitive Exam Test at four different times during the study: at baseline, after 2 months (after completion of the NNG), after 5 months (after completion of the TEG), and after 7 months (after 2 months of follow-up). Participants in the NNG and TEG presented significant improvements with respect to the CG, and in addition, the NNG generated greater relevant changes in the three variables with respect to the TEG (sleep quality (p = 0.972), daytime sleepiness (p = 0.026), and cognitive function (p = 0.127)). In conclusion, with greater effects in the NNG, both treatments were effective to improve daytime sleepiness, sleep quality, and cognitive function in the dementia population.

Weak synchronization can alter circadian period length: implications for aging and disease conditions

The synchronization of multiple oscillators serves as the central mechanism for maintaining stable circadian rhythms in physiology and behavior. Aging and disease can disrupt synchronization, leading to changes in the periodicity of circadian activities. While our understanding of the circadian clock under synchronization has advanced significantly, less is known about its behavior outside synchronization, which can also fall within a predictable domain. These states not only impact the stability of the rhythms but also modulate the period length. In C57BL/6 mice, aging, diseases, and removal of peripheral circadian oscillators often result in lengthened behavioral circadian periods. Here, we show that these changes can be explained by a surprisingly simple mathematical relationship: the frequency is the reciprocal of the period, and its distribution becomes skewed when the period distribution is symmetric. The synchronized frequency of a population in the skewed distribution and the macroscopic frequency of combined oscillators differ, accounting for some of the atypical circadian period outputs observed in networks without synchronization. Building on this finding, we investigate the dynamics of circadian outputs in the context of aging and disease, where synchronization is weakened.

Adaptive Circadian Rhythms for Autonomous and Biologically Inspired Robot Behavior

Biological rhythms are periodic internal variations of living organisms that act as adaptive responses to environmental changes. The human pacemaker is the suprachiasmatic nucleus, a brain region involved in biological functions like homeostasis or emotion. Biological rhythms are ultradian (<24 h), circadian (∼24 h), or infradian (>24 h) depending on their period. Circadian rhythms are the most studied since they regulate daily sleep, emotion, and activity. Ambient and internal stimuli, such as light or activity, influence the timing and the period of biological rhythms, making our bodies adapt to dynamic situations. Nowadays, robots experience unceasing development, assisting us in many tasks. Due to the dynamic conditions of social environments and human-robot interaction, robots exhibiting adaptive behavior have more possibilities to engage users by emulating human social skills. This paper presents a biologically inspired model based on circadian biorhythms for autonomous and adaptive robot behavior. The model uses the Dynamic Circadian Integrated Response Characteristic method to mimic human biology and control artificial biologically inspired functions influencing the robot's decision-making. The robot's clock adapts to light, ambient noise, and user activity, synchronizing the robot's behavior to the ambient conditions. The results show the adaptive response of the model to time shifts and seasonal changes of different ambient stimuli while regulating simulated hormones that are key in sleep/activity timing, stress, and autonomic basal heartbeat control during the day.

Parallel trajectories in the discovery of the SCN-OVLT and pituitary portal pathways: Legacies of Geoffrey Harris

A map of central nervous system organization based on vascular networks provides a layer of organization distinct from familiar neural networks or connectomes. As a well-established example, the capillary networks of the pituitary portal system enable a route for small amounts of neurochemical signals to reach local targets by traveling along specialized pathways, thereby avoiding dilution in the systemic circulation. The first evidence of such a pathway in the brain came from anatomical studies identifying a portal pathway linking the hypothalamus and the pituitary gland. Almost a century later, we demonstrated a vascular portal pathway that joined the capillary beds of the suprachiasmatic nucleus and a circumventricular organ, the organum vasculosum of the lamina terminalis, in a mouse brain. For each of these portal pathways, the anatomical findings opened many new lines of inquiry, including the determination of the direction of flow of information, the identity of the signal that flowed along this pathway, and the function of the signals that linked the two regions. Here, we review landmark steps to these discoveries and highlight the experiments that reveal the significance of portal pathways and more generally, the implications of morphologically distinct nuclei sharing capillary beds.

Familiarity of Brazilian psychologists with basic concepts in sleep science and chronobiology

Desynchronization of circadian rhythms and sleep-wake patterns impacts biochemical, physiological, and behavioral functions, including mental processes. The complex relationship between circadian rhythms and mental health makes it challenging to determine causality between circadian desynchronization and mental disorders. Regarding the fact that psychologists act as the front line for initial mental health care, we aimed to assess the knowledge and use of sleep science and basic chronobiology by professional psychologists in Brazil. Data were collected via an online questionnaire completed by 1384 professional psychologists between October 2018 and May 2019. Our findings revealed that ±80% of psychologists reported that at least half of their patients presented some sleep-related complaints; however, only ±27% routinely inquired about sleep quality even in the absence of patient complaints. Additionally, only ±66% initiated treatments to understand these complaints, potentially influenced by the lack of prior academic exposure to biological rhythms as reported by ±76% of Brazilian psychologists interviewed. Importantly, ±15% did not believe in an association between mental health and biological rhythms, and even a significant ±67% were unfamiliar with the term chronobiology and ±63% were not able to describe any other biological rhythm except for the sleep-wake cycle. These results demonstrate that fundamental concepts in chronobiology and sleep science are unknown to a substantial proportion of Brazilian psychologists. In conclusion, we propose that this subject could be more effectively integrated into psychologists' academic training, potentially promoting benefits through the incorporation of a chronobiological approach in mental health practice.

Circadian Rhythms and Astrocytes: The Good, the Bad, and the Ugly

This review explores the interface between circadian timekeeping and the regulation of brain function by astrocytes. Although astrocytes regulate neuronal activity across many time domains, their cell-autonomous circadian clocks exert a particular role in controlling longer-term oscillations of brain function: the maintenance of sleep states and the circadian ordering of sleep and wakefulness. This is most evident in the central circadian pacemaker, the suprachiasmatic nucleus, where the molecular clock of astrocytes suffices to drive daily cycles of neuronal activity and behavior. In Alzheimer's disease, sleep impairments accompany cognitive decline. In mouse models of the disease, circadian disturbances accelerate astroglial activation and other brain pathologies, suggesting that daily functions in astrocytes protect neuronal homeostasis. In brain cancer, treatment in the morning has been associated with prolonged survival, and gliomas have daily rhythms in gene expression and drug sensitivity. Thus, circadian time is fast becoming critical to elucidating reciprocal astrocytic-neuronal interactions in health and disease.

Combining biomechanical stimulation and chronobiology: a novel approach for augmented chondrogenesis?

The unique structure and composition of articular cartilage is critical for its physiological function. However, this architecture may get disrupted by degeneration or trauma. Due to the low intrinsic regeneration properties of the tissue, the healing response is generally poor. Low-grade inflammation in patients with osteoarthritis advances cartilage degradation, resulting in pain, immobility, and reduced quality of life. Generating neocartilage using advanced tissue engineering approaches may address these limitations. The biocompatible microenvironment that is suitable for cartilage regeneration may not only rely on cells and scaffolds, but also on the spatial and temporal features of biomechanics. Cell-autonomous biological clocks that generate circadian rhythms in chondrocytes are generally accepted to be indispensable for normal cartilage homeostasis. While the molecular details of the circadian clockwork are increasingly well understood at the cellular level, the mechanisms that enable clock entrainment by biomechanical signals, which are highly relevant in cartilage, are still largely unknown. This narrative review outlines the role of the biomechanical microenvironment to advance cartilage tissue engineering via entraining the molecular circadian clockwork, and highlights how application of this concept may enhance the development and successful translation of biomechanically relevant tissue engineering interventions.

FABP7: a glial integrator of sleep, circadian rhythms, plasticity, and metabolic function

Sleep and circadian rhythms are observed broadly throughout animal phyla and influence neural plasticity and cognitive function. However, the few phylogenetically conserved cellular and molecular pathways that are implicated in these processes are largely focused on neuronal cells. Research on these topics has traditionally segregated sleep homeostatic behavior from circadian rest-activity rhythms. Here we posit an alternative perspective, whereby mechanisms underlying the integration of sleep and circadian rhythms that affect behavioral state, plasticity, and cognition reside within glial cells. The brain-type fatty acid binding protein, FABP7, is part of a larger family of lipid chaperone proteins that regulate the subcellular trafficking of fatty acids for a wide range of cellular functions, including gene expression, growth, survival, inflammation, and metabolism. FABP7 is enriched in glial cells of the central nervous system and has been shown to be a clock-controlled gene implicated in sleep/wake regulation and cognitive processing. FABP7 is known to affect gene transcription, cellular outgrowth, and its subcellular localization in the fine perisynaptic astrocytic processes (PAPs) varies based on time-of-day. Future studies determining the effects of FABP7 on behavioral state- and circadian-dependent plasticity and cognitive processes, in addition to functional consequences on cellular and molecular mechanisms related to neural-glial interactions, lipid storage, and blood brain barrier integrity will be important for our knowledge of basic sleep function. Given the comorbidity of sleep disturbance with neurological disorders, these studies will also be important for our understanding of the etiology and pathophysiology of how these diseases affect or are affected by sleep.

Metabolism and exercise: the skeletal muscle clock takes centre stage

Circadian rhythms that influence mammalian homeostasis and overall health have received increasing interest over the past two decades. The molecular clock, which is present in almost every cell, drives circadian rhythms while being a cornerstone of physiological outcomes. The skeletal muscle clock has emerged as a primary contributor to metabolic health, as the coordinated expression of the core clock factors BMAL1 and CLOCK with the muscle-specific transcription factor MYOD1 facilitates the circadian and metabolic programme that supports skeletal muscle physiology. The phase of the skeletal muscle clock is sensitive to the time of exercise, which provides a rationale for exploring the interactions between the skeletal muscle clock, exercise and metabolic health. Here, we review the underlying mechanisms of the skeletal muscle clock that drive muscle physiology, with a particular focus on metabolic health. Additionally, we highlight the interaction between exercise and the skeletal muscle clock as a means of reinforcing metabolic health and discuss the possible implications of the time of exercise as a chronotherapeutic approach.

Rhythms in barriers and fluids: Circadian clock regulation in the aging neurovascular unit

The neurovascular unit is where two very distinct physiological systems meet: The central nervous system (CNS) and the blood. The permeability of the barriers separating these systems is regulated by time, including both the 24 h circadian clock and the longer processes of aging. An endogenous circadian rhythm regulates the transport of molecules across the blood-brain barrier and the circulation of the cerebrospinal fluid and the glymphatic system. These fluid dynamics change with time of day, and with age, and especially in the context of neurodegeneration. Factors may differ depending on brain region, as can be highlighted by consideration of circadian regulation of the neurovascular niche in white matter. As an example of a potential target for clinical applications, we highlight chaperone-mediated autophagy as one mechanism at the intersection of circadian dysregulation, aging and neurodegenerative disease. In this review we emphasize key areas for future research.

Chronotherapy in Glioblastoma: state of the art and future perspectives

Circadian rhythms regulate various processes in the human body, including drug metabolism. Chronotherapy optimizes treatment timing based on the circadian rhythm of the individual patient, such that the treatment efficacy is maximized, and adverse effects are minimized. It has been explored in different cancers with varying conclusions. Glioblastoma multiforme (GBM) is the most aggressive type of brain tumour with a very dismal prognosis. In recent years, there has been very little success in designing successful therapies to fight this disease. Chronotherapy offers the opportunity to leverage existing treatments to extend patient survival and to increase their quality of life. Here, we discuss recent advances in using chronotherapy regimens in the treatment of GMB, such as radiotherapy, temozolomide (TMZ) and bortezomib, as well as discuss novel treatments with drugs of short half-life or circadian phase specific activity, and examine the therapeutic potential of new approaches that target elements of the core circadian clock.

Can chronoradiotherapy offer benefits to cervical cancer patients? A scoping review

The objective of this scoping review was to synthesize the available evidence and evaluate the effectiveness of chronoradiotherapy interventions in cervical cancer patients. This scoping review was performed by searching in the PubMed, Cochrane Library, Embase, Web of Science, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), China National Knowledge Infrastructure (CNKI), Wanfang, Wenpu, and Chinese Biomedical Literature (CBM) databases. Databases were searched for studies published in English or Chinese from inception to 21 May 2021, and reference lists of relevant reports were scanned. Two investigators independently screened eligible studies in accordance with predetermined eligibility criteria and extracted data. The included studies were summarized and analyzed. Five studies including a total of 422 patients with cervical cancer were included in the scoping review; four studies were Chinese, and one was Indian. Main themes identified included the efficiency of chronoradiotherapy and relevant toxic and side effects, including diarrhea toxicity, hematologic toxicity, myelosuppression, gastrointestinal mucositis, and skin reactions. Administration of radiotherapy at different times of the day resulted in similar efficacy. However, the toxic side effects of morning radiotherapy (MR) and evening radiotherapy (ER) differed, with radiotherapy in the evening leading to more severe hematologic toxicity and myelosuppression. There were conflicting conclusions about gastrointestinal reactions with chronoradiotherapy, and further studies are needed. Radiation responses may be associated with circadian genes, through the influence of cell cycles and apoptosis.

Clocking Epilepsies: A Chronomodulated Strategy-Based Therapy for Rhythmic Seizures

Epilepsy is a neurological disorder characterized by hypersynchronous recurrent neuronal activities and seizures, as well as loss of muscular control and sometimes awareness. Clinically, seizures have been reported to display daily variations. Conversely, circadian misalignment and circadian clock gene variants contribute to epileptic pathogenesis. Elucidation of the genetic bases of epilepsy is of great importance because the genetic variability of the patients affects the efficacies of antiepileptic drugs (AEDs). For this narrative review, we compiled 661 epilepsy-related genes from the PHGKB and OMIM databases and classified them into 3 groups: driver genes, passenger genes, and undetermined genes. We discuss the potential roles of some epilepsy driver genes based on GO and KEGG analyses, the circadian rhythmicity of human and animal epilepsies, and the mutual effects between epilepsy and sleep. We review the advantages and challenges of rodents and zebrafish as animal models for epileptic studies. Finally, we posit chronomodulated strategy-based chronotherapy for rhythmic epilepsies, integrating several lines of investigation for unraveling circadian mechanisms underpinning epileptogenesis, chronopharmacokinetic and chronopharmacodynamic examinations of AEDs, as well as mathematical/computational modeling to help develop time-of-day-specific AED dosing schedules for rhythmic epilepsy patients.

Immunological and inflammatory effects of infectious diseases in circadian rhythm disruption and future therapeutic directions

BACKGROUND

Circadian rhythm is characterised by daily variations in biological activity to align with the light and dark cycle. These diurnal variations, in turn, influence physiological functions such as blood pressure, temperature, and sleep-wake cycle. Though it is well established that the circadian pathway is linked to pro-inflammatory responses and circulating immune cells, its association with infectious diseases is widely unknown.

OBJECTIVE

This comprehensive review aims to describe the association between circadian rhythm and host immune response to various kinds of infection.

METHODS

We conducted a literature search in databases Pubmed/Medline and Science direct. Our paper includes a comprehensive analysis of findings from articles in English which was related to our hypothesis.

FINDINGS

Molecular clocks determine circadian rhythm disruption in response to infection, influencing the host's response toward infection. Moreover, there is a complex interplay with intrinsic oscillators of pathogens and the influence of specific infectious processes on the CLOCK: BMAL1 pathway. Such mechanisms vary for bacterial and viral infections, both well studied in the literature. However, less is known about the association of parasitic infections and fungal pathogens with circadian rhythm modulation.

CONCLUSION

It is shown that bidirectional relationships exist between circadian rhythm disruption and infectious process, which contains interplay between the host's and pathogens' circadian oscillator, immune response, and the influence of specific infectious. Further studies exploring the modulations of circadian rhythm and immunity can offer novel explanations of different susceptibilities to infection and can lead to therapeutic avenues in circadian immune modulation of infectious diseases.

Physiological consequences of space flight, including abnormal bone metabolism, space radiation injury, and circadian clock dysregulation: Implications of melatonin use and regulation as a countermeasure

Exposure to the space environment induces a number of pathophysiological outcomes in astronauts, including bone demineralization, sleep disorders, circadian clock dysregulation, cardiovascular and metabolic dysfunction, and reduced immune system function. A recent report describing experiments aboard the Space Shuttle mission, STS-132, showed that the level of melatonin, a hormone that provides the biochemical signal of darkness, was decreased during microgravity in an in vitro culture model. Additionally, abnormal lighting conditions in outer space, such as low light intensity in orbital spacecraft and the altered 24-h light-dark cycles, may result in the dysregulation of melatonin rhythms and the misalignment of the circadian clock from sleep and work schedules in astronauts. Studies on Earth have demonstrated that melatonin regulates various physiological functions including bone metabolism. These data suggest that the abnormal regulation of melatonin in outer space may contribute to pathophysiological conditions of astronauts. In addition, experiments with high-linear energy transfer radiation, a ground-based model of space radiation, showed that melatonin may serve as a protectant against space radiation. Gene expression profiling using an in vitro culture model exposed to space flight during the STS-132 mission, showed that space radiation alters the expression of DNA repair and oxidative stress response genes, indicating that melatonin counteracts the expression of these genes responsive to space radiation to promote cell survival. These findings implicate the use of exogenous melatonin and the regulation of endogenous melatonin as countermeasures for the physiological consequences of space flight.