Training the Circadian Clock, Clocking the Drugs, and Drugging the Clock to Prevent, Manage, and Treat Chronic Diseases

Diet/photoperiod mediated changes in cerebellar clock genes causes locomotor shifts and imperative changes in BDNF-TrkB pathway

Neuropsychological studies report anxiety and depression like symptoms in patients suffering from lifestyle disorder but its impact on locomotor function lacks clarity. Our study investigates locomotor deficits resulting due to perturbations in cerebellum of high fat diet (HFD), chronodisruption (CD) or a combination (HCD) model of lifestyle disorder. Significant downregulation in levels of cerebellar clock genes (Bmal-1, Clock, Per 1 and Per 2) and Bdnf-Trkb pathway genes (Bdnf, TrkB and Syn1 levels) were recorded. Further, locomotor deficits were observed in all the three experimental groups as evidenced by actimeter test, pole test and wire hanging test. Nuclear pyknosis of Purkinje cells, their derangement and inflammation were the hallmark of cerebellar tissue of all the three experimental groups. Taken together, this study generates important links between cerebellar clock oscillations, locomotor function and Bdnf-TrkB signaling.

Ceramide-1-phosphate alleviates high-altitude pulmonary edema by stabilizing circadian ARNTL-mediated mitochondrial dynamics

INTRODUCTION

High-altitude pulmonary edema (HAPE) is a severe and potentially fatal condition with limited treatment options. Although ceramide kinase (CERK)-derived ceramide-1-phosphate (C1P) has been demonstrated to offer protection against various pulmonary diseases, its effects on HAPE remain unclear.

OBJECTIVES

Our study aimed to investigate the potential role of CERK-derived C1P in the development of HAPE and to reveal the molecular mechanisms underlying its protective effects. We hypothesized that CERK-derived C1P could protect against HAPE by stabilizing circadian rhythms and maintaining mitochondrial dynamics.

METHODS

To test our hypothesis, we used CERK-knockout mice and established HAPE mouse models using a FLYDWC50-1C hypobaric hypoxic cabin. We utilized a range of methods, including lipidomics, transcriptomics, immunofluorescence, Western blotting, and transmission electron microscopy, to identify the mechanisms of regulation.

RESULTS

Our findings demonstrated that CERK-derived C1P played a protective role against HAPE. Inhibition of CERK exacerbated HAPE induced by the hypobaric hypoxic environment. Specifically, we identified a novel mechanism in which CERK inhibition induced aryl hydrocarbon receptor nuclear translocator-like (ARNTL) autophagic degradation, inducing the circadian rhythm and triggering mitochondrial damage by controlling the expression of proteins required for mitochondrial fission and fusion. The decreased ARNTL caused by CERK inhibition impaired mitochondrial dynamics, induced oxidative stress damage, and resulted in defects in mitophagy, particularly under hypoxia. Exogenous C1P prevented ARNTL degradation, alleviated mitochondrial damage, neutralized oxidative stress induced by CERK inhibition, and ultimately relieved HAPE.

CONCLUSIONS

This study provides evidence for the protective effect of C1P against HAPE, specifically, through stabilizing circadian rhythms and maintaining mitochondrial dynamics. Exogenous C1P therapy may be a promising strategy for treating HAPE. Our findings also highlight the importance of the circadian rhythm and mitochondrial dynamics in the pathogenesis of HAPE, suggesting that targeting these pathways may be a potential therapeutic approach for this condition.

tauFisher predicts circadian time from a single sample of bulk and single-cell pseudobulk transcriptomic data

As the circadian clock regulates fundamental biological processes, disrupted clocks are often observed in patients and diseased tissues. Determining the circadian time of the patient or the tissue of focus is essential in circadian medicine and research. Here we present tauFisher, a computational pipeline that accurately predicts circadian time from a single transcriptomic sample by finding correlations between rhythmic genes within the sample. We demonstrate tauFisher's performance in adding timestamps to both bulk and single-cell transcriptomic samples collected from multiple tissue types and experimental settings. Application of tauFisher at a cell-type level in a single-cell RNAseq dataset collected from mouse dermal skin implies that greater circadian phase heterogeneity may explain the dampened rhythm of collective core clock gene expression in dermal immune cells compared to dermal fibroblasts. Given its robustness and generalizability across assay platforms, experimental setups, and tissue types, as well as its potential application in single-cell RNAseq data analysis, tauFisher is a promising tool that facilitates circadian medicine and research.

Daily glucocorticoids promote glioblastoma growth and circadian synchrony to the host

Glioblastoma (GBM) is the most common primary brain tumor in adults with a poor prognosis despite aggressive therapy. A recent, retrospective clinical study found that administering Temozolomide in the morning increased patient overall survival by 6 months compared to evening. Here, we tested the hypothesis that daily host signaling regulates tumor growth and synchronizes circadian rhythms in GBM. We found daily Dexamethasone promoted or suppressed GBM growth depending on time of day of administration and on the clock gene, Bmal1. Blocking circadian signals, like VIP or glucocorticoids, dramatically slowed GBM growth and disease progression. Finally, mouse and human GBM models have intrinsic circadian rhythms in clock gene expression in vitro and in vivo that entrain to the host through glucocorticoid signaling, regardless of tumor type or host immune status. We conclude that GBM entrains to the circadian circuit of the brain, which modulates its growth through clockcontrolled cues, like glucocorticoids.

Circadian Clock in Muscle Disease Etiology and Therapeutic Potential for Duchenne Muscular Dystrophy

Circadian clock and clock-controlled output pathways exert temporal control in diverse aspects of skeletal muscle physiology, including the maintenance of muscle mass, structure, function, and metabolism. They have emerged as significant players in understanding muscle disease etiology and potential therapeutic avenues, particularly in Duchenne muscular dystrophy (DMD). This review examines the intricate interplay between circadian rhythms and muscle physiology, highlighting how disruptions of circadian regulation may contribute to muscle pathophysiology and the specific mechanisms linking circadian clock dysregulation with DMD. Moreover, we discuss recent advancements in chronobiological research that have shed light on the circadian control of muscle function and its relevance to DMD. Understanding clock output pathways involved in muscle mass and function offers novel insights into the pathogenesis of DMD and unveils promising avenues for therapeutic interventions. We further explore potential chronotherapeutic strategies targeting the circadian clock to ameliorate muscle degeneration which may inform drug development efforts for muscular dystrophy.

Circadian regulation of cancer stem cells and the tumor microenvironment during metastasis

The circadian clock regulates daily rhythms of numerous physiological activities through tightly coordinated modulation of gene expression and biochemical functions. Circadian disruption is associated with enhanced tumor formation and metastasis via dysregulation of key biological processes and modulation of cancer stem cells (CSCs) and their specialized microenvironment. Here, we review how the circadian clock influences CSCs and their local tumor niches in the context of different stages of tumor metastasis. Identifying circadian therapeutic targets could facilitate the development of new treatments that leverage circadian modulation to ablate tumor-resident CSCs, inhibit tumor metastasis and enhance response to current therapies.

Understanding risk and causal mechanisms for developing obesity in infants and young children: A National Institutes of Health workshop

Obesity in children remains a major public health problem, with the current prevalence in youth ages 2-19 years estimated to be 19.7%. Despite progress in identifying risk factors, current models do not accurately predict development of obesity in early childhood. There is also substantial individual variability in response to a given intervention that is not well understood. On April 29-30, 2021, the National Institutes of Health convened a virtual workshop on "Understanding Risk and Causal Mechanisms for Developing Obesity in Infants and Young Children." The workshop brought together scientists from diverse disciplines to discuss (1) what is known regarding epidemiology and underlying biological and behavioral mechanisms for rapid weight gain and development of obesity and (2) what new approaches can improve risk prediction and gain novel insights into causes of obesity in early life. Participants identified gaps and opportunities for future research to advance understanding of risk and underlying mechanisms for development of obesity in early life. It was emphasized that future studies will require multi-disciplinary efforts across basic, behavioral, and clinical sciences. An exposome framework is needed to elucidate how behavioral, biological, and environmental risk factors interact. Use of novel statistical methods may provide greater insights into causal mechanisms.

Association of largest meal timing and eating frequency with body mass index and obesity

BACKGROUND AND AIMS

The circadian pattern of eating behaviors has garnered increasing interest as a strategy for obesity prevention and weight loss. It is believed that the benefits stem from aligning food intake with the body's natural daily rhythms. However, the existing body of evidence is limited in scale and scope and there has been insufficient evaluation of temporal eating behaviors, such as the specific time of day in which the highest calorie consumption occurs, meal frequency, and distribution. This research aims to explore the association between the timing of the largest meal of the day and eating frequency with Body Mass Index (BMI) and obesity.

METHODS

Participants (n = 2050, 18-65y) were part of an exploratory cross-sectional and population-based research, with data collection in a virtual environment. Linear regression analyses and restricted cubic splines evaluated differences in BMI associated with independent eating variables [timing of the largest meal, number of meals/day (as continuous and categorical: ≤3 or >3/day), and each largest meal of the day (breakfast/lunch/dinner)]. Logistic regression models were fitted to assess Odds Ratios (OR) and 95 % Confidence Intervals (CI) of obesity associated with the same independent variables.

RESULTS

Our main findings were that the timing of the largest meal and reporting dinner as the largest meal were associated with higher values of BMI (respectively, 0.07 kg/m2 and 0.85 kg/m2) and increased odds of obesity [respectively OR(95%CI):1.04(1.01,1.08), and OR(95%CI):1.67(1.18,2.38)]. Those who realized more than 3 meals/day presented lower values of BMI (-0.14 kg/m2) and 32 % lower odds of having obesity [OR(95%CI):0.68(0.52,0.89)]. Reporting lunch as the largest meal also protected against obesity [OR(95%CI):0.71(0.54,0.93)]. These associations were statistically significant and independent of sex, age, marital status, education level, diet quality, sleep duration, and weekly frequency of physical exercise.

CONCLUSION

Having the largest meal earlier in the day, concentrating the majority of caloric intake during lunch, and consuming more than three meals a day, may present a promising intervention for preventing and treating obesity/overweight.

Chronobiology of the Tumor Microenvironment: Implications for Therapeutic Strategies and Circadian-Based Interventions

Numerous research works have emphasized the critical role that circadian rhythm plays in the tumor microenvironment (TME). The goal of clarifying chrono-pharmacological strategies for improving cancer treatment in clinical settings is a continuous endeavor. Consequently, to enhance the use of time-based pharmaceutical therapies in oncology, combining existing knowledge on circadian rhythms' roles within the TME is essential. This perspective elucidates the functions of circadian rhythms in the TME across various stages of cancer development, progression, and metastasis. Specifically, aging, angiogenesis, and inflammation are implicated in modulating circadian rhythm within the TME. Furthermore, circadian rhythm exerts a profound influence on current cancer treatments and thereby generates chronotheray to manage tumors. From a TME perspective, circadian rhythm offers promising opportunities for cancer prevention and treatment; nevertheless, further study is needed to address unanswered scientific problems.

Unraveling the role of the circadian clock genes in cervical squamous cell carcinoma and endocervical adenocarcinoma: A prognostic indicator for prognostic, immunotherapy response, and chemotherapy sensitivity

Background: Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) account for a significant proportion of gynecological malignancies and represent a major global health concern. Globally, CESC is ranked as the fourth most common cancer among women. Conventional treatment of this disease has a less favorable prognosis for most patients. However, the discovery of early molecular biomarkers is therefore important for the diagnosis of CESC, as well as for slowing down their progression process. Methods: To identify differentially expressed genes strongly associated with prognosis, univariate Cox proportional hazard analysis and least absolute shrinkage and selection operator (LASSO) regression analysis were used. Using multiple Cox proportional hazard regression, a multifactorial model for prognostic risk assessment was then created. Results: The expression of biological clock-related genes, which varied considerably among distinct subtypes and were associated with significantly diverse prognoses, was used to categorize CESC patients. These findings demonstrate how the nomogram developed based on the 7-CRGs signature may assist physicians in creating more precise, accurate, and successful treatment plans that can aid CESC patients at 1, 3, and 5 years. Conclusions: By using machine learning techniques, we thoroughly investigated the impact of CRGs on the prognosis of CESC patients in this study. By creating a unique nomogram, we were able to accurately predict patient prognosis. At the same time, we showed new perspectives on the development of CESC and its treatment by analyzing the associations of the prognostic model with immunity, enrichment pathways, chemotherapy sensitivity, and so on. This research provides a new direction for clinical treatment.

Circadian Mechanisms in Brain Fluid Biology

The brain is a complex organ, fundamentally changing across the day to perform basic functions like sleep, thought, and regulating whole-body physiology. This requires a complex symphony of nutrients, hormones, ions, neurotransmitters and more to be properly distributed across the brain to maintain homeostasis throughout 24 hours. These solutes are distributed both by the blood and by cerebrospinal fluid. Cerebrospinal fluid contents are distinct from the general circulation because of regulation at brain barriers including the choroid plexus, glymphatic system, and blood-brain barrier. In this review, we discuss the overlapping circadian (≈24-hour) rhythms in brain fluid biology and at the brain barriers. Our goal is for the reader to gain both a fundamental understanding of brain barriers alongside an understanding of the interactions between these fluids and the circadian timing system. Ultimately, this review will provide new insight into how alterations in these finely tuned clocks may lead to pathology.

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.

Tumor circadian clock strength influences metastatic potential and predicts patient prognosis in luminal A breast cancer

Studies in shift workers and model organisms link circadian disruption to breast cancer. However, molecular circadian rhythms in noncancerous and cancerous human breast tissues and their clinical relevance are largely unknown. We reconstructed rhythms informatically, integrating locally collected, time-stamped biopsies with public datasets. For noncancerous breast tissue, inflammatory, epithelial-mesenchymal transition (EMT), and estrogen responsiveness pathways show circadian modulation. Among tumors, clock correlation analysis demonstrates subtype-specific changes in circadian organization. Luminal A organoids and informatic ordering of luminal A samples exhibit continued, albeit dampened and reprogrammed rhythms. However, CYCLOPS magnitude, a measure of global rhythm strength, varied widely among luminal A samples. Cycling of EMT pathway genes was markedly increased in high-magnitude luminal A tumors. Surprisingly, patients with high-magnitude tumors had reduced 5-y survival. Correspondingly, 3D luminal A cultures show reduced invasion following molecular clock disruption. This study links subtype-specific circadian disruption in breast cancer to EMT, metastatic potential, and prognosis.

The Molecular Circadian Clock Is a Target of Anti-cancer Translation Inhibitors

Circadian-paced biological processes are key to physiology and required for metabolic, immunologic, and cardiovascular homeostasis. Core circadian clock components are transcription factors whose half-life is precisely regulated, thereby controlling the intrinsic cellular circadian clock. Genetic disruption of molecular clock components generally leads to marked pathological events phenotypically affecting behavior and multiple aspects of physiology. Using a transcriptional signature similarity approach, we identified anti-cancer protein synthesis inhibitors as potent modulators of the cardiomyocyte molecular clock. Eukaryotic protein translation inhibitors, ranging from translation initiation (rocaglates, 4-EGI1, etc.) to ribosomal elongation inhibitors (homoharringtonine, puromycin, etc.), were found to potently ablate protein abundance of REV-ERBα, a repressive nuclear receptor and component of the molecular clock. These inhibitory effects were observed both in vitro and in vivo and could be extended to PER2, another component of the molecular clock. Taken together, our observations suggest that the activity spectrum of protein synthesis inhibitors, whose clinical use is contemplated not only in cancers but also in viral infections, must be extended to circadian rhythm disruption, with potential beneficial or iatrogenic effects upon acute or prolonged administration.

Imputing missing sleep data from wearables with neural networks in real-world settings

Sleep is a critical component of health and well-being but collecting and analyzing accurate longitudinal sleep data can be challenging, especially outside of laboratory settings. We propose a simple neural network model titled SOMNI (Sleep data restOration using Machine learning and Non-negative matrix factorIzation [NMF]) for imputing missing rest-activity data from actigraphy, which can enable clinicians to better handle missing data and monitor sleep-wake cycles of individuals with highly irregular sleep-wake patterns. The model consists of two hidden layers and uses NMF to capture hidden longitudinal sleep-wake patterns of individuals with disturbed sleep-wake cycles. Based on this, we develop two approaches: the individual approach imputes missing data based on the data from only one participant, while the global approach imputes missing data based on the data across multiple participants. Our models are tested with shift and non-shift workers' data from three independent hospitals. Both approaches can accurately impute missing data up to 24 hours of long dataset (>50 days) even for shift workers with extremely irregular sleep-wake patterns (AUC > 0.86). On the other hand, for short dataset (~15 days), only the global model is accurate (AUC > 0.77). Our approach can be used to help clinicians monitor sleep-wake cycles of patients with sleep disorders outside of laboratory settings without relying on sleep diaries, ultimately improving sleep health outcomes.

Circadian lifestyle determinants of immune checkpoint inhibitor efficacy

Immune Checkpoint Inhibitors (ICI) have revolutionised cancer care in recent years. Despite a global improvement in the efficacy and tolerability of systemic anticancer treatments, a sizeable proportion of patients still do not benefit maximally from ICI. Extensive research has been undertaken to reveal the immune- and cancer-related mechanisms underlying resistance and response to ICI, yet more limited investigations have explored potentially modifiable lifestyle host factors and their impact on ICI efficacy and tolerability. Moreover, multiple trials have reported a marked and coherent effect of time-of-day ICI administration and patients' outcomes. The biological circadian clock indeed temporally controls multiple aspects of the immune system, both directly and through mediation of timing of lifestyle actions, including food intake, physical exercise, exposure to bright light and sleep. These factors potentially modulate the immune response also through the microbiome, emerging as an important mediator of a patient's immune system. Thus, this review will look at critically amalgamating the existing clinical and experimental evidence to postulate how modifiable lifestyle factors could be used to improve the outcomes of cancer patients on immunotherapy through appropriate and individualised entrainment of the circadian timing system and temporal orchestration of the immune system functions.

The Impact of Immunotherapy on Sleep and Circadian Rhythms in Patients with Cancer

Immunotherapy has revolutionized treatments for both early and advanced cancers, and as their role evolves, their impact on sleep and circadian rhythms continues to unfold. The recognition, evaluation, and treatment of sleep and circadian rhythm disturbance leads to improved symptom management, quality of life and treatment outcomes. An intricate complex relationship exists in the microenvironment with immunity, sleep and the tumor, and these may further vary based on the cancer, addition of standard chemotherapy, and pre-existing patient factors. Sleep and circadian rhythms may offer tools to better utilize immunotherapy in the care of cancer patients, leading to better treatment outcome, reduced symptom burden, and increased quality of life.

tauFisher accurately predicts circadian time from a single sample of bulk and single-cell transcriptomic data

As the circadian clock regulates fundamental biological processes, disrupted clocks are often observed in patients and diseased tissues. Determining the circadian time of the patient or the tissue of focus is essential in circadian medicine and research. Here we present tau-Fisher, a computational pipeline that accurately predicts circadian time from a single transcriptomic sample by finding correlations between rhythmic genes within the sample. We demonstrate tauFisher's out-standing performance in both bulk and single-cell transcriptomic data collected from multiple tissue types and experimental settings. Application of tauFisher at a cell-type level in a single-cell RNA-seq dataset collected from mouse dermal skin implies that greater circadian phase heterogeneity may explain the dampened rhythm of collective core clock gene expression in dermal immune cells compared to dermal fibroblasts. Given its robustness and generalizability across assay platforms, experimental setups, and tissue types, as well as its potential application in single-cell RNA-seq data analysis, tauFisher is a promising tool that facilitates circadian medicine and research.

Watching the clock in glioblastoma

Glioblastoma (GBM) is the most prevalent malignant primary brain tumor, accounting for 14.2% of all diagnosed tumors and 50.1% of all malignant tumors, and the median survival time is approximately 8 months irrespective of whether a patient receives treatment without significant improvement despite expansive research (Ostrom QT, Price M, Neff C, et al. CBTRUS statistical report: primary brain and other central nervous system tumors diagnosed in the United States in 2015-2019. Neurooncology. 2022; 24(suppl 5):v1-v95.). Recently, important roles for the circadian clock in GBM tumorigenesis have been reported. Positive regulators of circadian-controlled transcription, brain and muscle ARNT-like 1 (BMAL1), and circadian locomotor output cycles kaput (CLOCK), are highly expressed also in GBM and correlated with poor patient prognosis. BMAL1 and CLOCK promote the maintenance of GBM stem cells (GSCs) and the establishment of a pro-tumorigenic tumor microenvironment (TME), suggesting that targeting the core clock proteins may augment GBM treatment. Here, we review findings that highlight the critical role the circadian clock plays in GBM biology and the strategies by which the circadian clock can be leveraged for GBM treatment in the clinic moving forward.

Approaches in line with human physiology to prevent skin aging

Skin aging is a complex process that is influenced by intrinsic and extrinsic factors that impact the skin's protective functions and overall health. As the body's outermost layer, the skin plays a critical role in defending it against external threats, regulating body temperature, providing tactile sensation, and synthesizing vitamin D for bone health, immune function, and body homeostasis. However, as individuals age, the skin undergoes structural and functional changes, leading to impairments in these essential functions. In contemporary society, there is an increasing recognition of skin health as a significant indicator of overall wellbeing, resulting in a growing demand for anti-aging products and treatments. However, these products often have limitations in terms of safety, effective skin penetration, and potential systemic complications. To address these concerns, researchers are now focusing on approaches that are safer and better aligned with physiology of the skin. These approaches include adopting a proper diet and maintaining healthy lifestyle habits, the development of topical treatments that synchronize with the skin's circadian rhythm, utilizing endogenous antioxidant molecules, such as melatonin and natural products like polyphenols. Moreover, exploring alternative compounds for sun protection, such as natural ultraviolet (UV)-absorbing compounds, can offer safer options for shielding the skin from harmful radiation. Researchers are currently exploring the potential of adipose-derived stem cells, cell-free blood cell secretome (BCS) and other endogenous compounds for maintaining skin health. These approaches are more secure and more effective alternatives which are in line with human physiology to tackle skin aging. By emphasizing these innovative strategies, it is possible to develop effective treatments that not only slow down the skin aging process but also align better with the natural physiology of the skin. This review will focus on recent research in this field, highlighting the potential of these treatments as being safer and more in line with the skin's physiology in order to combat the signs of aging.

Anti-adipogenic properties of clock activator chlorhexidine and a new derivative

Background

The circadian clock exerts temporal control of metabolic pathways to maintain homeostasis, and its disruption leads to the development of obesity and insulin resistance. In adipose tissue, key regulators of clock machinery orchestrate adipogenic processes via the Wnt signaling pathway to impact mature adipocyte development.

Methods

Based on the recent finding of chlorhexidine as a new clock activator, we determined its potential anti-adipogenic activities in distinct adipogenic progenitor models. Furthermore, we report the structural optimization of chlorhexidine leading to the discovery of analogs with improved efficacy in inhibiting adipogenesis.

Results

In adipogenic progenitors with Per2::dLuc luciferase reporter, Chlorhexidine shortened clock period length with induction of core clock components. Consistent with its clock-activating function, Chlorhexidine robustly suppressed the lineage commitment and maturation of adipogenic mesenchymal precursors, with comparable effect on inhibiting preadipocyte terminal differentiation. Mechanistically, we show that Chlorhexidine induces signaling components of the Wnt pathway resulting in activation of Wnt activity. Via modification of its chemical scaffold, we generated analogs of chlorhexidine that led to the identification of CM002 as a new clock- activating molecule with improved anti-adipogenic activity.

Conclusions

Collectively, our findings uncovered the anti-adipogenic functions of a new class of small molecule clock activators. These compounds provide novel chemical probes to dissect clock function in maintaining metabolic homeostasis and may have therapeutic implications in obesity and associated metabolic disorders.

A real-time, personalized sleep intervention using mathematical modeling and wearable devices

The prevalence of artificial light exposure has enabled us to be active any time of the day or night, leading to the need for high alertness outside of traditional daytime hours. To address this need, we developed a personalized sleep intervention framework that analyzes real-world sleep-wake patterns obtained from wearable devices to maximize alertness during specific target periods. Our framework utilizes a mathematical model that tracks the dynamic sleep pressure and circadian rhythm based on the user's sleep history. In this way, the model accurately predicts real-time alertness, even for shift workers with complex sleep and work schedules (N = 71, t = 13~21 days). This allowed us to discover a new sleep-wake pattern called the adaptive circadian split sleep, which incorporates a main sleep period and a late nap to enable high alertness during both work and non-work periods of shift workers. We further developed a mobile application that integrates this framework to recommend practical, personalized sleep schedules for individual users to maximize their alertness during a targeted activity time based on their desired sleep onset and available sleep duration. This can reduce the risk of errors for those who require high alertness during nontraditional activity times and improve the health and quality of life for those leading shift work-like lifestyles.

CIRCUST: A novel methodology for temporal order reconstruction of molecular rhythms; validation and application towards a daily rhythm gene expression atlas in humans

The circadian system drives near-24-h oscillations in behaviors and biological processes. The underlying core molecular clock regulates the expression of other genes, and it has been shown that the expression of more than 50 percent of genes in mammals displays 24-h rhythmic patterns, with the specific genes that cycle varying from one tissue to another. Determining rhythmic gene expression patterns in human tissues sampled as single timepoints has several challenges, including the reconstruction of temporal order of highly noisy data. Previous methodologies have attempted to address these challenges in one or a small number of tissues for which rhythmic gene evolutionary conservation is assumed to be preserved. Here we introduce CIRCUST, a novel CIRCular-robUST methodology for analyzing molecular rhythms, that relies on circular statistics, is robust against noise, and requires fewer assumptions than existing methodologies. Next, we validated the method against four controlled experiments in which sampling times were known, and finally, CIRCUST was applied to 34 tissues from the Genotype-Tissue Expression (GTEx) dataset with the aim towards building a comprehensive daily rhythm gene expression atlas in humans. The validation and application shown here indicate that CIRCUST provides a flexible framework to formulate and solve the issues related to the analysis of molecular rhythms in human tissues. CIRCUST methodology is publicly available at https://github.com/yolandalago/CIRCUST/.

Diurnal rhythms of wrist temperature are associated with future disease risk in the UK Biobank

Many chronic disease symptomatologies involve desynchronized sleep-wake cycles, indicative of disrupted biorhythms. This can be interrogated using body temperature rhythms, which have circadian as well as sleep-wake behavior/environmental evoked components. Here, we investigated the association of wrist temperature amplitudes with a future onset of disease in the UK Biobank one year after actigraphy. Among 425 disease conditions (range n = 200-6728) compared to controls (range n = 62,107-91,134), a total of 73 (17%) disease phenotypes were significantly associated with decreased amplitudes of wrist temperature (Benjamini-Hochberg FDR q < 0.05) and 26 (6.1%) PheCODEs passed a more stringent significance level (Bonferroni-correction α < 0.05). A two-standard deviation (1.8° Celsius) lower wrist temperature amplitude corresponded to hazard ratios of 1.91 (1.58-2.31 95% CI) for NAFLD, 1.69 (1.53-1.88) for type 2 diabetes, 1.25 (1.14-1.37) for renal failure, 1.23 (1.17-1.3) for hypertension, and 1.22 (1.11-1.33) for pneumonia (phenome-wide atlas available at http://bioinf.itmat.upenn.edu/biorhythm_atlas/ ). This work suggests peripheral thermoregulation as a digital biomarker.

Circadian clock regulator Bmal1 gates axon regeneration via Tet3 epigenetics in mouse sensory neurons

Axon regeneration of dorsal root ganglia (DRG) neurons after peripheral axotomy involves reconfiguration of gene regulatory circuits to establish regenerative gene programs. However, the underlying mechanisms remain unclear. Here, through an unbiased survey, we show that the binding motif of Bmal1, a central transcription factor of the circadian clock, is enriched in differentially hydroxymethylated regions (DhMRs) of mouse DRG after peripheral lesion. By applying conditional deletion of Bmal1 in neurons, in vitro and in vivo neurite outgrowth assays, as well as transcriptomic profiling, we demonstrate that Bmal1 inhibits axon regeneration, in part through a functional link with the epigenetic factor Tet3. Mechanistically, we reveal that Bmal1 acts as a gatekeeper of neuroepigenetic responses to axonal injury by limiting Tet3 expression and restricting 5hmC modifications. Bmal1-regulated genes not only concern axon growth, but also stress responses and energy homeostasis. Furthermore, we uncover an epigenetic rhythm of diurnal oscillation of Tet3 and 5hmC levels in DRG neurons, corresponding to time-of-day effect on axon growth potential. Collectively, our studies demonstrate that targeting Bmal1 enhances axon regeneration.

Targeted screening and identification of chlorhexidine as a pro-myogenic circadian clock activator

BACKGROUND

The circadian clock is an evolutionarily conserved mechanism that exerts pervasive temporal control in stem cell behavior. This time-keeping machinery is required for orchestrating myogenic progenitor properties in regenerative myogenesis that ameliorates muscular dystrophy. Here we report a screening platform to discover circadian clock modulators that promote myogenesis and identify chlorhexidine (CHX) as a clock-activating molecule with pro-myogenic activities.

METHODS

A high-throughput molecular docking pipeline was applied to identify compounds with a structural fit for a hydrophobic pocket within the key circadian transcription factor protein, Circadian Locomotor Output Cycles Kaput (CLOCK). These identified molecules were further screened for clock-modulatory activities and functional validations for pro-myogenic properties.

RESULTS

CHX was identified as a clock activator that promotes distinct aspects of myogenesis. CHX activated circadian clock that reduced cycling period length and augmented amplitude. This action was mediated by the targeted CLOCK structure via augmented interaction with heterodimer partner Bmal1, leading to enhanced CLOCK/Bmal1-controlled transcription with upregulation of core clock genes. Consistent with its clock-activating function, CHX displayed robust effects on stimulating myogenic differentiation in a clock-dependent manner. In addition, CHX augmented the proliferative and migratory activities of myoblasts.

CONCLUSION

Our findings demonstrate the feasibility of a screening platform to discover clock modulators with myogenic regulatory activities. Discovery of CHX as a pro-myogenic molecule could be applicable to promote regenerative capacities in ameliorating dystrophic or degenerative muscle diseases.

Understanding the role of chronopharmacology for drug optimization: what do we know?

INTRODUCTION

Circadian rhythm influences the pharmacokinetics and pharmacodynamics of a number of drugs and affects their therapeutic efficacy and toxicity depending on the time of day they are administered. Chronopharmacology is a method for incorporating knowledge about circadian rhythm into pharmacotherapy. Chronotherapy, which is the clinical application of chronopharmacology, is particularly relevant when the risk and/or severity of symptoms of a disease change in a predictable manner over time. Chronotherapy has potential benefits in the treatment of many diseases.

AREAS COVERED

Although a considerable amount of knowledge about chronopharmacology and chronotherapy has been accumulated, its therapeutic application in clinical practice remains limited in terms of therapy optimization. Resolution of these issues will improve our ability to deliver adequate drug treatment.

EXPERT OPINION

We propose four approaches for promoting chronotherapy-based drug treatment in clinical practice: targeting drug development and regulatory authorities; education about chronotherapy; drug information for both health professionals and consumers; and a chronotherapy network.

The Clock-modulatory Activity of Nobiletin Suppresses Adipogenesis Via Wnt Signaling

The circadian clock machinery exerts transcriptional control to modulate adipogenesis and its disruption leads to the development of obesity. Here, we report that Nobiletin, a circadian clock amplitude-enhancing molecule, displays antiadipogenic properties via activation of Wnt signaling pathway that is dependent on its clock modulation. Nobiletin augmented clock oscillatory amplitude with period lengthening in the adipogenic mesenchymal precursor cells and preadipocytes, accompanied by an induction of Bmal1 and clock components within the negative feedback arm. Consistent with its clock-modulatory activity, Nobiletin strongly inhibited the lineage commitment and terminal differentiation of adipogenic progenitors. Mechanistically, we show that Nobiletin induced the reactivation of Wnt signaling during adipogenesis via transcriptional up-regulation of key components within this pathway. Furthermore, Nobiletin administration in mice markedly reduced adipocyte hypertrophy, leading to a significant loss of fat mass and reduction of body weight. Last, Nobiletin inhibited the differentiation of primary preadipocytes, and this effect was dependent on a functional clock regulation. Collectively, our findings uncover a novel activity of Nobiletin in suppressing adipocyte development in a clock-dependent manner, implicating its potential application in countering obesity and associated metabolic consequences.

The Role of REV-ERB Receptors in Cancer Pathogenesis

REV-ERB receptors are members of the nuclear receptor superfamily of proteins, which act as both intracellular receptors and transcription factors, therefore modulating the expression of target genes. REV-ERBs act as transcription repressors because of their unique structure. Their predominant role involves the control of peripheral circadian rhythmicity by participating in a transcription-translation feedback loop with other major clock genes. Regarding their role in cancer pathogenesis, recent studies in various cancerous tissues have revealed that their expression was downregulated in the majority of the cases. Dysregulation of their expression was also implicated in cancer-associated cachexia. The pharmacological restoration of their effects is feasible with synthetic agonists, which have been explored in preclinical studies but with scarce data. There is a need for further investigation, primarily with mechanistic studies, on the effect of the REV-ERB-induced circadian rhythm deregulation in carcinogenesis and cancer-related systemic effects, such as cachexia, in order to address the potential of relevant therapeutic implications.

Subtype-specific circadian clock dysregulation modulates breast cancer biology, invasiveness, and prognosis

Studies in shift workers and model organisms link circadian disruption to breast cancer. However, molecular rhythms in non-cancerous and cancerous human breast tissues are largely unknown. We reconstructed rhythms informatically, integrating locally collected, time-stamped biopsies with public datasets. For non-cancerous tissue, the inferred order of core-circadian genes matches established physiology. Inflammatory, epithelial-mesenchymal transition (EMT), and estrogen responsiveness pathways show circadian modulation. Among tumors, clock correlation analysis demonstrates subtype-specific changes in circadian organization. Luminal A organoids and informatic ordering of Luminal A samples exhibit continued, albeit disrupted rhythms. However, CYCLOPS magnitude, a measure of global rhythm strength, varied widely among Luminal A samples. Cycling of EMT pathway genes was markedly increased in high-magnitude Luminal A tumors. Patients with high-magnitude tumors had reduced 5-year survival. Correspondingly, 3D Luminal A cultures show reduced invasion following molecular clock disruption. This study links subtype-specific circadian disruption in breast cancer to EMT, metastatic potential, and prognosis.

Chronic jetlag accelerates pancreatic neoplasia in conditional Kras-mutant mice

Misalignment of the circadian clock compared to environmental cues causes circadian desynchrony, which is pervasive in humans. Clock misalignment can lead to various pathologies including obesity and diabetes, both of which are associated with pancreatic ductal adenocarcinoma - a devastating cancer with an 80% five-year mortality rate. Although circadian desynchrony is associated with an increased risk of several solid-organ cancers, the correlation between clock misalignment and pancreas cancer is unclear. Using a chronic jetlag model, we investigated the impact of clock misalignment on pancreas cancer initiation in mice harboring a pancreas-specific activated Kras mutation. We found that chronic jetlag accelerated the development of pancreatic cancer precursor lesions, with a concomitant increase in precursor lesion grade. Cell-autonomous knock-out of the clock in pancreatic epithelial cells of Kras-mutant mice demonstrated no acceleration of precursor lesion formation, indicating non-cell-autonomous clock dysfunction was responsible for the expedited tumor development. Therefore, we applied single-cell RNA sequencing over time and identified fibroblasts as the cell population manifesting the greatest clock-dependent changes, with enrichment of specific cancer-associated fibroblast pathways due to circadian misalignment.

CRS: a circadian rhythm score model for predicting prognosis and treatment response in cancer patients

BACKGROUND

Circadian rhythm regulates complex physiological activities in organisms. A strong link between circadian dysfunction and cancer has been identified. However, the factors of dysregulation and functional significance of circadian rhythm genes in cancer have received little attention.

METHODS

In 18 cancer types from The Cancer Genome Atlas (TCGA), the differential expression and genetic variation of 48 circadian rhythm genes (CRGs) were examined. The circadian rhythm score (CRS) model was created using the ssGSEA method, and patients were divided into high and low groups based on the CRS. The Kaplan-Meier curve was created to assess the patient survival rate. Cibersort and estimate methods were used to identify the infiltration characteristics of immune cells between different CRS subgroups. Gene Expression Omnibus (GEO) dataset is used as verification queue and model stability evaluation queue. The CRS model's ability to predict chemotherapy and immunotherapy was assessed. Wilcoxon rank-sum test was used to compare the differences of CRS among different patients. We use CRS to identify potential "clock-drugs" by the connective map method.

RESULTS

Transcriptomic and genomic analyses of 48 CRGs revealed that most core clock genes are up-regulated, while clock control genes are down-regulated. Furthermore, we show that copy number variation may affect CRGs aberrations. Based on CRS, patients can be classified into two groups with significant differences in survival and immune cell infiltration. Further studies showed that patients with low CRS were more sensitive to chemotherapy and immunotherapy. Additionally, we identified 10 compounds (e.g. flubendazole, MLN-4924, ingenol) that are positively associated with CRS, and have the potential to modulate circadian rhythms.

CONCLUSIONS

CRS can be utilized as a clinical indicator to predict patient prognosis and responsiveness to therapy, and identify potential "clock-drugs".

The role of microRNAs in the molecular link between circadian rhythm and autism spectrum disorder

Circadian rhythm regulates physiological cycles of awareness and sleepiness. Melatonin production is primarily regulated by circadian regulation of gene expression and is involved in sleep homeostasis. If the circadian rhythm is abnormal, sleep disorders, such as insomnia and several other diseases, can occur. The term 'autism spectrum disorder (ASD)' is used to characterize people who exhibit a certain set of repetitive behaviors, severely constrained interests, social deficits, and/or sensory behaviors that start very early in life. Because many patients with ASD suffer from sleep disorders, sleep disorders and melatonin dysregulation are attracting attention for their potential roles in ASD. ASD is caused by abnormalities during the neurodevelopmental processes owing to various genetic or environmental factors. Recently, the role of microRNAs (miRNAs) in circadian rhythm and ASD have gained attraction. We hypothesized that the relationship between circadian rhythm and ASD could be explained by miRNAs that can regulate or be regulated by either or both. In this study, we introduced a possible molecular link between circadian rhythm and ASD. We performed a thorough literature review to understand their complexity.

The role of the circadian clock in the development, progression, and treatment of non-alcoholic fatty liver disease

The circadian clock comprises a cellular endogenous timing system coordinating the alignment of physiological processes with geophysical time. Disruption of circadian rhythms has been associated with several metabolic diseases. In this review, we focus on liver as a major metabolic tissue and one of the most well-studied organs with regard to circadian regulation. We summarize current knowledge about the role of local and systemic clocks and rhythms in regulating biological functions of the liver. We discuss how the disruption of circadian rhythms influences the development of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). We also critically evaluate whether NAFLD/NASH may in turn result in chronodisruption. The last chapter focuses on potential roles of the clock system in prevention and treatment of NAFLD/NASH and the interaction of current NASH drug candidates with liver circadian rhythms and clocks. It becomes increasingly clear that paying attention to circadian timing may open new avenues for the optimization of NAFLD/NASH therapies and provide interesting targets for prevention and treatment of these increasingly prevalent disorders.

Diurnal rhythmicity of wearable device-measured wrist temperature predicts future disease incidence in the UK Biobank

Many chronic disease symptomatologies involve desynchronized sleep-wake cycles, indicative of disrupted biorhythms. This can be interrogated using body temperature rhythms, which are well-established biomarkers for circadian clock function. Here, we investigated the association of wrist temperature amplitudes with a future onset of disease in the UK Biobank one year after actigraphy. Among 425 disease conditions (range n =  200-6,728) compared to controls (range n =  62,107 - 91,134), a total of 73 (36.5%) disease phenotypes were significantly associated with decreased amplitudes of wrist temperature (Benjamini-Hochberg FDR q < 0.05) and 26 (13%) PheCODEs passed a more stringent significance level (Bonferroni-correction α < 0.05). Here, for example, a two-standard deviation (1.8° Celsius) lower wrist temperature amplitude corresponded to hazard ratios of 1.91 (1.58-2.31 95% CI) for NAFLD, 1.69 (1.53-1.88) for type 2 diabetes, 1.25 (1.14-1.37) for renal failure, 1.23 (1.17-1.3) for hypertension, and 1.22 (1.11-1.33) for pneumonia. A comprehensive phenome-wide atlas of the identified mappings has been made available at http://bioinf.itmat.upenn.edu/biorhythm_atlas/. These findings strongly suggest peripheral thermoregulation as a digital biomarker.

The clock-modulatory activity of Nobiletin suppresses adipogenesis via Wnt signaling

The circadian clock machinery exerts transcriptional control to modulate adipogenesis and its disruption leads to the development of obesity. Here we report that Nobiletin, a clock amplitude-enhancing molecule, displays anti-adipogenic properties via activating a clock-controlled Wnt signaling pathway that suppresses adipocyte differentiation. Nobiletin augmented clock oscillation with period length shortening in the adipogenic mesenchymal precursor cells and preadipocytes, accompanied by an induction of Bmal1 and core clock components. Consistent with its circadian clock-modulatory activity, Nobiletin inhibited the lineage commitment and terminal differentiation of adipogenic progenitors. Mechanistically, we show that Nobiletin induced the re-activation of Wnt signaling during adipogenic differentiation via transcriptional up-regulation of key components of this pathway. Furthermore, Nobiletin administration in mice markedly reduced adipocyte hypertrophy, leading to a significant loss of fat mass and body weight reduction. Lastly, Nobiletin inhibited the maturation of primary preadipocytes and this effect was dependent on a functional clock regulation. Collectively, our findings uncover a novel activity of Nobiletin in suppressing adipocyte development, implicating its potential therapeutic application in countering obesity and its associated metabolic consequences.

Chrono-Nutrition: Circadian Rhythm and Personalized Nutrition

The human circadian system has a period of approximately 24 h and studies on the consequences of "chornodisruption" have greatly expanded. Lifestyle and environmental factors of modern societies (i.e., artificial lighting, jetlag, shift work, and around-the-clock access to energy-dense food) can induce disruptions of the circadian system and thereby adversely affect individual health. Growing evidence demonstrates a complex reciprocal relationship between metabolism and the circadian system, in which perturbations in one system affect the other one. From a nutritional genomics perspective, genetic variants in clock genes can both influence metabolic health and modify the individual response to diet. Moreover, an interplay between the circadian rhythm, gut microbiome, and epigenome has been demonstrated, with the diet in turn able to modulate this complex link suggesting a remarkable plasticity of the underlying mechanisms. In this view, the study of the impact of the timing of eating by matching elements from nutritional research with chrono-biology, that is, chrono-nutrition, could have significant implications for personalized nutrition in terms of reducing the prevalence and burden of chronic diseases. This review provides an overview of the current evidence on the interactions between the circadian system and nutrition, highlighting how this link could in turn influence the epigenome and microbiome. In addition, possible nutritional strategies to manage circadian-aligned feeding are suggested.

A circadian rhythm-related gene signature for prognosis, invasion and immune microenvironment of breast cancer

Background: Circadian dysregulation is linked to the onset and progression of cancer, but current knowledge of the role of circadian rhythm-related genes (CRRGs) in breast cancer (BC) is limited and incomplete. The purpose of this study was to investigate the potential role and immune-related prognostic significance of CRRGs in BC. Methods: The Cancer Genome Atlas breast cancer (TCGA-BRCA) genetic data were combined with 1369 CRRGs to create a model of BC prognosis-related CRRGs. To validate the model's predictive power in TCGA and other external datasets, the Kaplan-Meier survival curve and receptor operation characteristic curve were plotted. The relationship between CRRGs model and gene enrichment pathways, immune cell infiltration, and differences in patient response to immune checkpoint inhibitors (ICIs) therapy was then discussed. Results: A CRRG-based eighteen-gene model was developed that accurately predicted the survival time of BC patients. Based on this model, BC patients can be classified as high or low risk. The high-risk group has negative immune cell infiltration (such as macrophages M0 and M2) and a poor therapeutic response to ICIs due to lower immune checkpoint gene expression. Furthermore, TCF7 and IFNG were found to be strongly associated with immune checkpoints in CRRGs model. Conclusion: The 18 CRRGs may be useful in assessing the prognosis of BC patients, studying immune infiltration, and developing more effective immunotherapy strategies.

TimeTeller for timing health: The potential of circadian medicine to improve performance, prevent disease and optimize treatment

Circadian medicine, the study of the effects of time on health and disease has seen an uprising in recent years as a means to enhance health and performance, and optimize treatment timing. Our endogenous time generating system -the circadian clock- regulates behavioural, physiological and cellular processes. Disruptions of the clock, via external factors like shift work or jet lag, or internal perturbations such as genetic alterations, are linked to an increased risk of various diseases like obesity, diabetes, cardiovascular diseases and cancer. By aligning an individual's circadian clock with optimal times for performing daily routines, physical and mental performance, and also the effectiveness of certain therapies can be improved. Despite the benefits of circadian medicine, the lack of non-invasive tools for characterizing the clock limits the potential of the field. TimeTeller is a non-invasive molecular/digital tool for the characterization of circadian rhythms and prediction of daily routines, including treatment timing, to unlock the potential of circadian medicine and implementing it in various settings. Given the multiple known and potentially yet unknown dependent health factors of individual circadian rhythms, the utility of this emerging biomarker is best exploited in data driven, personalized medicine use cases, using health information across lifestyle, care, and research settings.

Circadian medicine for aging attenuation and sleep disorders: Prospects and challenges

Aging causes progressive deterioration of daily rhythms in behavioral and metabolic processes and disruption in the regular sleep-wake cycle. Circadian disruption is directly related to diverse age-induced health abnormalities. Rising evidence from various organisms shows that core clock gene mutations cause premature aging, reduced lifespan, and sleeping irregularities. Improving the clock functions and correcting its disruption by pharmacological interventions or time-regulated feeding patterns could be a novel avenue for effective clinical management of aging and sleep disorders. To this end, many drugs for sleep disorders and anti-aging compounds interact with the core clock machinery and alter the circadian output. Evaluation of dosing time-dependency and circadian regulation of drug metabolism for therapeutic improvement of the existing drugs is another fundamental facet of chronomedicine. Multiple studies have demonstrated dose-dependent manipulation of the circadian period and phase-shifting by pharmacologically active compounds. The chronobiology research field is gradually moving towards the development of novel therapeutic strategies based on targeting the molecular clock or dosing time-oriented medications. However, such translational research ventures would require more experimental evidence from studies on humans. This review discusses the impact of circadian rhythms on aging and sleep, emphasizing the potentiality of circadian medicine in aging attenuation and sleep disorders.

Circadian stabilization loop: the regulatory hub and therapeutic target promoting circadian resilience and physiological health

The circadian clock is a fundamental biological mechanism that orchestrates essential cellular and physiological processes to optimize fitness and health. The basic functional unit is the cell-autonomous oscillator, consisting of intersecting negative feedback loops. Whereas the core loop is primarily responsible for rhythm generation, auxiliary loops, most notably the secondary or stabilization loop, play pivotal roles to confer temporal precision and molecular robustness. The stabilization loop contains opposing nuclear receptor subfamilies REV-ERBs and retinoic acid receptor-related orphan receptors (RORs), competing to modulate rhythmic expression of the basic helix-loop-helix ARNT like 1 ( Bmal1) genes in the core loop as well as other clock-controlled genes. Therefore, REV-ERBs and RORs are strategically located to interface the oscillator and the global transcriptomic network, promoting cellular homeostasis and physiological fitness throughout lifespan. Disruption of REV-ERB and ROR functions has been linked with diseases and aging, and pharmacological manipulation of these factors has shown promise in various mouse disease models. Nobiletin is a natural compound that directly binds to and activates RORα/γ, modulating circadian rhythms, and shows robust in vivo efficacies to combat clock-associated pathophysiologies and age-related decline. Results from several studies demonstrate an inverse relation between nobiletin efficacy and clock functional state, where nobiletin elicits little effect in young and healthy mice with growing efficacy as the clock is perturbed by environmental and genetic challenges. This mode of action is consistent with the function of the stabilization loop to promote circadian and physiological resilience. Future studies should further investigate the function and mechanism of REV-ERBs and RORs, and test strategies targeting these factors against disease and aging.

Circadian stabilization loop: the regulatory hub and therapeutic target promoting circadian resilience and physiological health

The circadian clock is a fundamental biological mechanism that orchestrates essential cellular and physiological processes to optimize fitness and health. The basic functional unit is the cell-autonomous oscillator, consisting of intersecting negative feedback loops. Whereas the core loop is primarily responsible for rhythm generation, auxiliary loops, most notably the secondary or stabilization loop, play pivotal roles to confer temporal precision and molecular robustness. The stabilization loop contains opposing nuclear receptor subfamilies REV-ERBs and retinoic acid receptor-related orphan receptors (RORs), competing to modulate rhythmic expression of the basic helix-loop-helix ARNT like 1 ( Bmal1) genes in the core loop as well as other clock-controlled genes. Therefore, REV-ERBs and RORs are strategically located to interface the oscillator and the global transcriptomic network, promoting cellular homeostasis and physiological fitness throughout lifespan. Disruption of REV-ERB and ROR functions has been linked with diseases and aging, and pharmacological manipulation of these factors has shown promise in various mouse disease models. Nobiletin is a natural compound that directly binds to and activates RORα/γ, modulating circadian rhythms, and shows robust in vivo efficacies to combat clock-associated pathophysiologies and age-related decline. Results from several studies demonstrate an inverse relation between nobiletin efficacy and clock functional state, where nobiletin elicits little effect in young and healthy mice with growing efficacy as the clock is perturbed by environmental and genetic challenges. This mode of action is consistent with the function of the stabilization loop to promote circadian and physiological resilience. Future studies should further investigate the function and mechanism of REV-ERBs and RORs, and test strategies targeting these factors against disease and aging.

Structural basis of synthetic agonist activation of the nuclear receptor REV-ERB

The nuclear receptor REV-ERB plays an important role in a range of physiological processes. REV-ERB behaves as a ligand-dependent transcriptional repressor and heme has been identified as a physiological agonist. Our current understanding of how ligands bind to and regulate transcriptional repression by REV-ERB is based on the structure of heme bound to REV-ERB. However, porphyrin (heme) analogues have been avoided as a source of synthetic agonists due to the wide range of heme binding proteins and potential pleotropic effects. How non-porphyrin synthetic agonists bind to and regulate REV-ERB has not yet been defined. Here, we characterize a high affinity synthetic REV-ERB agonist, STL1267, and describe its mechanism of binding to REV-ERB as well as the method by which it recruits transcriptional corepressor both of which are unique and distinct from that of heme-bound REV-ERB.

Getting the clock back on its feet: targeting the circadian clock to treat osteoarthritis

Growing evidence suggests that circadian clock dysfunction may contribute to the pathology of osteoarthritis. In this issue, He et al. use in vivo and human-derived osteoarthritis models to demonstrate the therapeutic potential of pharmacologically manipulating components of the cartilage circadian clock. In doing so, the authors provide an important proof-of-principle supporting circadian clock-targeted therapy as a treatment option for osteoarthritis. Comment on: https://doi.org/10.1111/febs.16601.

Characteristics of circadian rhythm-related genes and establishment of a prognostic scoring system for lung adenocarcinoma with experimental verification: a bioinformatics analysis

BACKGROUND

Non-small cell lung cancer (NSCLC) is one of the most common malignant tumors worldwide. Lung adenocarcinoma (LUAD), the main subtype of NSCLC, has a poor prognosis. In recent years, circadian rhythm (CR)-related genes (CRRGs) have demonstrated associations with tumor occurrence and development, but the relationship between CRRGs and LUAD is not clear. Because of the correlation between CRRGs and tumors, we have reason to believe that CRRGs will become an important prognostic indicator for LUAD and guide the treatment of LUAD prognosis.

METHODS

Based on data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, we explored the biological function and immune cell infiltration of LUAD in different CR clusters and quantified CR genes using principal component analysis (PCA). Then, we built a CR scoring system (CRscore) to explore the relationship between CRRGs and LUAD prognosis.

RESULTS

Patients were divided into three clusters (A, B, and C). Biological characteristics, such as survival, immune cell infiltration, and gene enrichment, were significantly different among the three clusters (P<0.001). We then established the usefulness of the CR score, which could probably predict the prognosis of LUAD. Specifically, patients with a high CR score had a better prognosis and were more sensitive to chemotherapy than those with a low CR score.

CONCLUSIONS

It is possible to use CRRGs to assess the prognosis of patients with LUAD. Quantification of CR using the CRscore tool in patients with LUAD maybe help to guide personalized cancer immunotherapy strategies in the future. Thus, the CRscore may be a prognostic tool for LUAD.

The pancreatic clock is a key determinant of pancreatic fibrosis progression and exocrine dysfunction

Chronic pancreatitis (CP) is characterized by progressive fibrosis and exocrine dysregulation, which have long been considered irreversible. As a peripheral oscillator, the pancreas harbors autonomous and self-sustained timekeeping systems in both its endocrine and exocrine compartments, although the role of the latter remains poorly understood. By using different models of CP established in mice with dysfunctional pancreatic clocks, we found that the local clock played an important role in CP pathology, and genetic or external disruption of the pancreatic clock exacerbated fibrogenesis and exocrine insufficiency. Mechanistically, an impaired retinoic acid receptor-related orphan receptor A (Rora)/nuclear receptor subfamily 1, group D, member 1 (Nr1d1)/aryl hydrocarbon receptor nuclear translocator-like (Arntl or Bmal1) loop, called the circadian stabilizing loop, resulted in the deficiency of pancreatic Bmal1, which was responsible for controlling the fibrogenic properties of pancreatic stellate cells (PSCs) and for rewiring the function of acinar cells in a clock-TGF signaling-IL-11/IL-11RA axis-dependent manner. During PSC activation, the antagonistic interaction between Nr1d1 and Rora was unbalanced in response to the loss of cytoplasmic retinoid-containing lipid droplets. Patients with CP also exhibited reduced production of endogenous melatonin. Enhancing the clock through pharmacological restoration of the circadian stabilizing loop using a combination of melatonin and the Rora agonist SR1078 attenuated intrapancreatic pathological changes in mouse models of CP. Collectively, this study identified a protective role of the pancreatic clock against pancreatic fibrosis and exocrine dysfunction. Pancreatic clock-targeted therapy may represent a potential strategy to treat CP.

Obesity, cancer risk, and time-restricted eating

Obesity and the associated metabolic syndrome is considered a pandemic whose prevalence is steadily increasing in many countries worldwide. It is a complex, dynamic, and multifactorial disorder that presages the development of several metabolic, cardiovascular, and neurodegenerative diseases, and increases the risk of cancer. In patients with newly diagnosed cancer, obesity worsens prognosis, increasing the risk of recurrence and decreasing survival. The multiple negative effects of obesity on cancer outcomes are substantial, and of great clinical importance. Strategies for weight control have potential utility for both prevention efforts and enhancing cancer outcomes. Presently, time-restricted eating (TRE) is a popular dietary intervention that involves limiting the consumption of calories to a specific window of time without any proscribed caloric restriction or alteration in dietary composition. As such, TRE is a sustainable long-term behavioral modification, when compared to other dietary interventions, and has shown many health benefits in animals and humans. The preliminary data regarding the effects of time-restricted feeding on cancer development and growth in animal models are promising but studies in humans are lacking. Interestingly, several short-term randomized clinical trials of TRE have shown favorable effects to reduce cancer risk factors; however, long-term trials of TRE have yet to investigate reductions in cancer incidence or outcomes in the general population. Few studies have been conducted in cancer populations, but a number are underway to examine the effect of TRE on cancer biology and recurrence. Given the simplicity, feasibility, and favorable metabolic improvements elicited by TRE in obese men and women, TRE may be useful in obese cancer patients and cancer survivors; however, the clinical implementation of TRE in the cancer setting will require greater in-depth investigation.

Antiproliferative Effects of Cynara Cardunculus in Colorectal Cancer Cells Are Modulated by the Circadian Clock

The circadian clock generates 24 h rhythms in behavioural, cellular and molecular processes. Malfunctions of the clock are associated with enhanced susceptibility to cancer, worse treatment response and poor prognosis. Clock-controlled genes are involved in cellular processes associated with tumour development and progression including metabolism of drugs and the cell cycle. Cynara cardunculus, a plant of the Asteraceae family, has been reported to have antiproliferative effects on breast cancer cells. Here, we used the human colorectal cancer (CRC) cell line HCT116 and its knockout variants for different core-clock genes (BMAL1, PER2, NR1D1), to investigate the treatment effect of C. cardunculus lipophilic leaf extract under different clock scenarios. Our results show a direct effect of C. cardunculus on the circadian phenotype of the cells, as indicated by alterations in the phase, amplitude, and period length of core-clock gene oscillations. Furthermore, our data indicate a role for the circadian clock in sensitivity to C. cardunculus treatment. In particular, the treatment inhibited proliferation and induced cytotoxicity and apoptosis in a clock knockout-specific manner, in CRC cells. These results point to a potential effect of C. cardunculus lipophilic leaf extracts as a modulator of the circadian clock, in addition to its anti-proliferative properties.