Crosstalk between metabolism and circadian clocks

Homeostatic regulation of NAD(H) and NADP(H) in cells

Nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) and nicotinamide adenine dinucleotide phosphate (NADP+)/reduced NADP+ (NADPH) are essential metabolites involved in multiple metabolic pathways and cellular processes. NAD+ and NADH redox couple plays a vital role in catabolic redox reactions, while NADPH is crucial for cellular anabolism and antioxidant responses. Maintaining NAD(H) and NADP(H) homeostasis is crucial for normal physiological activity and is tightly regulated through various mechanisms, such as biosynthesis, consumption, recycling, and conversion between NAD(H) and NADP(H). The conversions between NAD(H) and NADP(H) are controlled by NAD kinases (NADKs) and NADP(H) phosphatases [specifically, metazoan SpoT homolog-1 (MESH1) and nocturnin (NOCT)]. NADKs facilitate the synthesis of NADP+ from NAD+, while MESH1 and NOCT convert NADP(H) into NAD(H). In this review, we summarize the physiological roles of NAD(H) and NADP(H) and discuss the regulatory mechanisms governing NAD(H) and NADP(H) homeostasis in three key aspects: the transcriptional and posttranslational regulation of NADKs, the role of MESH1 and NOCT in maintaining NAD(H) and NADP(H) homeostasis, and the influence of the circadian clock on NAD(H) and NADP(H) homeostasis. In conclusion, NADKs, MESH1, and NOCT are integral to various cellular processes, regulating NAD(H) and NADP(H) homeostasis. Dysregulation of these enzymes results in various human diseases, such as cancers and metabolic disorders. Hence, strategies aiming to restore NAD(H) and NADP(H) homeostasis hold promise as novel therapeutic approaches for these diseases.

Regulation of metabolism by circadian rhythms: Support from time-restricted eating, intestinal microbiota & omics analysis

Circadian oscillatory system plays a key role in coordinating the metabolism of most organisms. Perturbation of genetic effects and misalignment of circadian rhythms result in circadian dysfunction and signs of metabolic disorders. The eating-fasting cycle can act on the peripheral circadian clocks, bypassing the photoperiod. Therefore, time-restricted eating (TRE) can improve metabolic health by adjusting eating rhythms, a process achieved through reprogramming of circadian genomes and metabolic programs at different tissue levels or remodeling of the intestinal microbiota, with omics technology allowing visualization of the regulatory processes. Here, we review recent advances in circadian regulation of metabolism, focus on the potential application of TRE for rescuing circadian dysfunction and metabolic disorders with the contribution of intestinal microbiota in between, and summarize the significance of omics technology.

Neurotoxicity of hexaconazole on rat brain: The aspect of biological rhythm

Hexaconazole is a widely used and frequently detected fungicide which is also reported to be persistent in environment. The toxicity of Hex to non-organisms such as reproductive toxicity, endocrine disrupting toxicity, and carcinogenic toxicity had been reported. However, study on the Hex-induced neurotoxicity is rare and the mechanism is still unclear. Therefore, in this study, environmental related concentrations of Hex were chosen to investigate the effects of Hex on nervous system from the aspect of biological rhythm under 90 d sub-chronic exposure. The results showed that Hex significantly affected the cognitive function of rats resulting in the deterioration of learning and memory ability and induced oxidative stress in rat brain. Moreover, the notable changes of neurotransmitters in rat brain suggested the disorder of nerve signaling conduction induced by Hex. The influence of Hex on biological rhythm was further detected which showed that levels of rhythm regulatory genes and proteins significantly disturbed at four monitored time periods. Based on these results, it was supposed that the underlying mechanism of Hex-induced cognitive dysfunction might through oxidative stress pathway. Our findings could systematically and comprehensively clarify the effects of Hex on nervous system and were helpful for prevention neurological diseases induced by triazole pesticides.

Moderate chronic sleep perturbation impairs glucose and lipid homeostasis in rats

STUDY OBJECTIVES

Sleep deprivation is a potential risk factor for metabolic diseases, including obesity and type 2 diabetes. We evaluated the impacts of moderate chronic sleep deprivation on glucose and lipid homeostasis in adult rats.

METHODS

Wistar rats (both sexes) were sleep-perturbed daily for 2 hours at the early (06:00-08:00) and the late light cycle (16:00-18:00) five days a week (except weekends) for 4 weeks.

RESULTS

Sleep perturbation (SP) resulted in reduced body weight gain in both sexes, associated with altered food intake and reduced adiposity. SP did not alter the short- or long-term memories or cause anxiogenic behavior. No major changes were observed in the plasma insulin, leptin, triacylglycerol, non-esterified fatty acids, and blood glucose upon SP. After SP, females exhibited a transitory glucose intolerance, while males became glucose intolerant at the end of the experimental period. Male rats also developed higher insulin sensitivity at the end of the SP protocol. Morphometric analyses revealed no changes in hepatic glycogen deposition, pancreatic islet mass, islet-cell distribution, or adrenal cortex thickness in SP rats from both sexes, except for lower adipocyte size compared with controls. We did not find homogeneous changes in the relative expression of circadian and metabolic genes in muscle or hepatic tissues from the SP rats.

CONCLUSIONS

Moderate chronic SP reduces visceral adiposity and causes glucose intolerance with a more pronounced impact on male rats, reinforcing the metabolic risks of exposure to sleep disturbances.

Association of chrononutrition patterns with biological aging: evidence from a nationally representative cross-sectional study

Previous studies mostly focused on the benefits of caloric restriction and fasting on longevity. However, whether the timing and frequency of eating affect aging remains unclear. Here, we investigated the associations between chrononutrition patterns and biological aging, and explored whether and to what extent dietary inflammation mediated this association. 16 531 adults aged 20 to 84 years from the National Health and Nutrition Examination Survey were collected. Chrononutrition patterns were determined with two 24-hour dietary recalls. Phenotypic age was calculated to reflect the biological aging status. The dietary inflammatory index (DII) was used to assess the dietary inflammation. After adjustment of the survey weight and multiple covariates including total energy intake, participants in the third tertile of the time of the first meal (mean 10 : 26) exhibited more advanced biological age (β 0.64; 95% CI, 0.26-1.00) and a higher incidence of accelerated aging (odds ratio (OR) 1.25; 95% CI, 1.06-1.47) compared to those of the first tertile (mean 6 : 14). Higher eating frequency was associated with delayed biological aging in both multivariable linear (β -0.31; 95% CI, -0.44 to -0.19) and logistic regression model (OR 0.90; 95% CI, 0.85-0.95). Furthermore, we found that DII rather than metabolic factors mediated the inverse association between eating frequency and biological aging (mediation proportion 24.67%; 95% CI, 19.83%-32.00%). Our findings demonstrated the association between chrononutrition patterns and biological aging among the US general population and the potential role of dietary inflammation in this association, suggesting that modifying chrononutrition patterns may be a practical and cost-effective strategy for combating aging.

Investigating the role of obesity, circadian disturbances and lifestyle factors in people with schizophrenia and bipolar disorder: Study protocol for the SOMBER trial

The aim of this study is to investigate circadian rhythms in independently living adults with obesity and mental disease, exploring the interplay between biological markers and lifestyle factors. Eighty participants divided equally into four groups; (i) people with obesity and schizophrenia; (ii) people with obesity and bipolar disorder; (iii) people with obesity without mental disease or sleep disorders, and (iv) people without obesity, mental disease or sleep disorders. Over two consecutive days, participants engage in repeated self-sampling of hair follicle and saliva; concurrently, data is collected on diet, body temperature, light exposure, sleep parameters, and physical activity by accelerometry. Hair follicles are analyzed for circadian gene expression, saliva samples for cortisol and melatonin concentrations. Circadian rhythms are investigated by cosinor analysis. The study employs a participant-tailored sampling schedule to minimize disruptions to daily routine and enhance ecological validity. The methodology aims to provide a comprehensive insight into the factors contributing to circadian disruptions in people with obesity, bipolar disorder and schizophrenia, potentially informing strategies for future management and mitigation. Trial registration: (ClinicalTrials.gov Identifier: NCT05413486).

The effects of time restricted feeding on age-related changes in the mouse retina

Dietary modifications such as caloric restriction (CR) and intermittent fasting (IF) have gained popularity due to their proven health benefits in aged populations. In time restricted feeding (TRF), a form of intermittent fasting, the amount of time for food intake is regulated without restricting the caloric intake. TRF is beneficial for the central nervous system to support brain health in the context of aging. Therefore, we here ask whether TRF also exerts beneficial effects in the aged retina. We compared aged mice (24 months) on a TRF paradigm (access to food for six hours per day) for either 6 or 12 months against young control mice (8 months) and aged control mice on an ad libitum diet. We examined changes in the retina at the functional (electroretinography), structural (histology and fluorescein angiograms) and molecular (gene expression) level. TRF treatment showed amelioration of age-related reductions in both scotopic and photopic b-wave amplitudes suggesting benefits for retinal interneuron signaling. TRF did not affect age-related signs of retinal inflammation or microglial activation at either the molecular or histological level. Our data indicate that TRF helps preserve some aspects of retinal function that are decreased with aging, adding to our understanding of the health benefits that altered feeding patterns may confer.

A coupled model between circadian, cell-cycle, and redox rhythms reveals their regulation of oxidative stress

Most organisms possess three biological oscillators, circadian clock, cell cycle, and redox rhythm, which are autonomous but interact each other. However, whether their interactions and autonomy are beneficial for organisms remains unclear. Here, we modeled a coupled oscillator system where each oscillator affected the phase of the other oscillators. We found that multiple types of coupling prevent a high H2O2 level in cells at M phase. Consequently, we hypothesized a high H2O2 sensitivity at the M phase and found that moderate coupling reduced cell damage due to oxidative stress by generating appropriate phase relationships between three rhythms, whereas strong coupling resulted in an elevated cell damage by increasing the average H2O2 level and disrupted the cell cycle. Furthermore, the multicellularity model revealed that phase variations among cells confer flexibility in synchronization with environments at the expense of adaptability to the optimal environment. Thus, both autonomy and synchrony among the oscillators are important for coordinating their phase relationships to minimize oxidative stress, and couplings balance them depending on environments.

Model integration of circadian- and sleep-wake-driven contributions to rhythmic gene expression reveals distinct regulatory principles

Analyses of gene-expression dynamics in research on circadian rhythms and sleep homeostasis often describe these two processes using separate models. Rhythmically expressed genes are, however, likely to be influenced by both processes. We implemented a driven, damped harmonic oscillator model to estimate the contribution of circadian- and sleep-wake-driven influences on gene expression. The model reliably captured a wide range of dynamics in cortex, liver, and blood transcriptomes taken from mice and humans under various experimental conditions. Sleep-wake-driven factors outweighed circadian factors in driving gene expression in the cortex, whereas the opposite was observed in the liver and blood. Because of tissue- and gene-specific responses, sleep deprivation led to a long-lasting intra- and inter-tissue desynchronization. The model showed that recovery sleep contributed to these long-lasting changes. The results demonstrate that the analyses of the daily rhythms in gene expression must take the complex interactions between circadian and sleep-wake influences into account. A record of this paper's transparent peer review process is included in the supplemental information.

Unraveling the Health Benefits and Mechanisms of Time-Restricted Feeding: Beyond Caloric Restriction

Time-restricted feeding (TRF) is a lifestyle intervention that aims to maintain a consistent daily cycle of feeding and fasting to support robust circadian rhythms. Recently, it has gained scientific, medical, and public attention due to its potential to enhance body composition, extend lifespan, and improve overall health, as well as induce autophagy and alleviate symptoms of diseases like cardiovascular diseases, type 2 diabetes, neurodegenerative diseases, cancer, and ischemic injury. However, there is still considerable debate on the primary factors that contribute to the health benefits of TRF. Despite not imposing strict limitations on calorie intake, TRF consistently led to reductions in calorie intake. Therefore, while some studies suggest that the health benefits of TRF are primarily due to caloric restriction (CR), others argue that the key advantages of TRF arise not only from CR but also from factors like the duration of fasting, the timing of the feeding period, and alignment with circadian rhythms. To elucidate the roles and mechanisms of TRF beyond CR, this review incorporates TRF studies that did not use CR, as well as TRF studies with equivalent energy intake to CR, which addresses the previous lack of comprehensive research on TRF without CR and provides a framework for future research directions.

Human primary cells can tell body time: Dedicated to Steven A. Brown

The field of chronobiology has advanced significantly since ancient observations of natural rhythms. The intricate molecular architecture of circadian clocks, their hierarchical organization within the mammalian body, and their pivotal roles in organ physiology highlight the complexity and significance of these internal timekeeping mechanisms. In humans, circadian phenotypes exhibit considerable variability among individuals and throughout the individual's lifespan. A fundamental challenge in mechanistic studies of human chronobiology arises from the difficulty of conducting serial sampling from most organs. The concept of studying circadian clocks in vitro relies on the groundbreaking discovery by Ueli Schibler and colleagues that nearly every cell in the body harbours autonomous molecular oscillators. The advent of circadian bioluminescent reporters has provided a new perspective for this approach, enabling high-resolution continuous measurements of cell-autonomous clocks in cultured cells, following in vitro synchronization pulse. The work by Steven A. Brown has provided compelling evidence that clock characteristics assessed in primary mouse and human skin fibroblasts cultured in vitro represent a reliable estimation of internal clock properties in vivo. The in vitro approach for studying molecular human clocks in cultured explants and primary cells, pioneered by Steve Brown, represents an invaluable tool for assessing inter-individual differences in circadian characteristics alongside comprehensive genetic, biochemical and functional analyses. In a broader context, this reliable and minimally invasive approach offers a unique perspective for unravelling the functional inputs and outputs of oscillators operative in nearly any human tissue in physiological contexts and across various pathologies.

Effect of Meal-Timing on the Association of Unsaturated Fatty Acids with All-Cause and Cardiovascular Mortality among Adults: A Prospective Cohort Study with 10-Year Follow-Up

BACKGROUND

Conflicting results have been reported on the association of dietary unsaturated fatty acids (UFAs) with longevity and cardiovascular health. Most previous studies have focused only on the amount of UFAs consumed, not the timing of intake.

METHODS

This prospective cohort study used data from 30,136 adults aged 18 years and older. Intakes of UFAs by meal time and types were assessed by a 24-h dietary recall for two days. The covariate-adjusted survey-weighted Cox proportional hazards models were performed to evaluate the associations of dietary total unsaturated fatty acid (TUFA), polyunsaturated fatty acid (PUFA), and monounsaturated fatty acid (MUFA) intakes throughout the day and three meals with mortality.

RESULTS

During a median of 10.0 years of follow-up, 4510 total deaths occurred. All-cause mortality decreased with increasing intakes at dinner of TUFA (HR: 0.87 [0.77-0.98]), PUFA (HR: 0.81 [0.73-0.91]), and MUFA (HR: 0.88 [0.77-0.99]). With an increased intake of PUFA at dinner, CVD mortality showed a decreasing trend. However, the inverted L-shaped non-linear trend in all-cause mortality was found with increasing intake at breakfast of TUFA (HR: 1.35 [1.17-1.57], Q3 vs. Q1), PUFA (HR: 1.30 [1.13-1.50]), and MUFA (HR: 1.28 [1.13-1.45]). Meanwhile, increased breakfast intake of UFAs was associated with increased CVD and heart disease mortality.

CONCLUSIONS

Meal timing influences the association of UFAs with all-cause and CVD-related mortality.

Aryl hydrocarbon receptor impairs circadian regulation in Alzheimer's disease: Potential impact on glymphatic system dysfunction

Circadian clocks maintain diurnal rhythms of sleep-wake cycle of 24 h that regulate not only the metabolism of an organism but also many other periodical processes. There is substantial evidence that circadian regulation is impaired in Alzheimer's disease. Circadian clocks regulate many properties known to be disturbed in Alzheimer's patients, such as the integrity of the blood-brain barrier (BBB) as well as the diurnal glymphatic flow that controls waste clearance from the brain. Interestingly, an evolutionarily conserved transcription factor, that is, aryl hydrocarbon receptor (AhR), impairs the function of the core clock proteins and thus could disturb diurnal rhythmicity in the BBB. There is abundant evidence that the activation of AhR signalling inhibits the expression of the major core clock proteins, such as the brain and muscle arnt-like 1 (BMAL1), clock circadian regulator (CLOCK) and period circadian regulator 1 (PER1) in different experimental models. The expression of AhR is robustly increased in the brains of Alzheimer's patients, and protein level is enriched in astrocytes of the BBB. It seems that AhR signalling inhibits glymphatic flow since it is known that (i) activation of AhR impairs the function of the BBB, which is cooperatively interconnected with the glymphatic system in the brain, and (ii) neuroinflammation and dysbiosis of gut microbiota generate potent activators of AhR, which are able to impair glymphatic flow. I will examine current evidence indicating that activation of AhR signalling could disturb circadian functions of the BBB and impair glymphatic flow and thus be involved in the development of Alzheimer's pathology.

Exploring the metabolic implications of blue light exposure during daytime in rats

Excessive exposure to light is a global issue. Artificial light pollution has been shown to disrupt the body's natural circadian rhythm. To investigate the impacts of light on metabolism, we studied Sprague-Dawley rats chronically exposed to red or blue light during daytime or nighttime. Rats in the experimental group were exposed to extended light for 4 hours during daytime or nighttime to simulate the effects of excessive light usage. Strikingly, we found systemic metabolic alterations only induced by blue light during daytime. Furthermore, we conducted metabolomic analyses of the cerebrospinal fluid, serum, heart, liver, spleen, adrenal, cerebellum, pituitary, prostate, spermatophore, hypothalamus and kidney from rats in the control and blue light exposure during daytime. Significant changes in metabolites have been observed in cerebrospinal fluid, serum, hypothalamus and kidney of rats exposed to blue light during daytime. Metabolic alterations observed in rats encompassing pyruvate metabolism, glutathione metabolism homocysteine degradation, phosphatidylethanolamine biosynthesis, and phospholipid biosynthesis, exhibit analogous patterns to those inherent in specific physiological processes, notably neurodevelopment, cellular injury, oxidative stress, and autophagic pathways. Our study provides insights into tissue-specific metabolic changes in rats exposed to blue light during the daytime and may help explain potential mechanisms of photopathogenesis.

The circadian clock in the choroid plexus drives rhythms in multiple cellular processes under the control of the suprachiasmatic nucleus

Choroid plexus (ChP), the brain structure primarily responsible for cerebrospinal fluid production, contains a robust circadian clock, whose role remains to be elucidated. The aim of our study was to [1] identify rhythmically controlled cellular processes in the mouse ChP and [2] assess the role and nature of signals derived from the master clock in the suprachiasmatic nuclei (SCN) that control ChP rhythms. To accomplish this goal, we used various mouse models (WT, mPer2Luc, ChP-specific Bmal1 knockout) and combined multiple experimental approaches, including surgical lesion of the SCN (SCNx), time-resolved transcriptomics, and single cell luminescence microscopy. In ChP of control (Ctrl) mice collected every 4 h over 2 circadian cycles in darkness, we found that the ChP clock regulates many processes, including the cerebrospinal fluid circadian secretome, precisely times endoplasmic reticulum stress response, and controls genes involved in neurodegenerative diseases (Alzheimer's disease, Huntington's disease, and frontotemporal dementia). In ChP of SCNx mice, the rhythmicity detected in vivo and ex vivo was severely dampened to a comparable extent as in mice with ChP-specific Bmal1 knockout, and the dampened cellular rhythms were restored by daily injections of dexamethasone in mice. Our data demonstrate that the ChP clock controls tissue-specific gene expression and is strongly dependent on the presence of a functional connection with the SCN. The results may contribute to the search for a novel link between ChP clock disruption and impaired brain health.

Histone methylation: at the crossroad between circadian rhythms in transcription and metabolism

Circadian rhythms, essential 24-hour cycles guiding biological functions, synchronize organisms with daily environmental changes. These rhythms, which are evolutionarily conserved, govern key processes like feeding, sleep, metabolism, body temperature, and endocrine secretion. The central clock, located in the suprachiasmatic nucleus (SCN), orchestrates a hierarchical network, synchronizing subsidiary peripheral clocks. At the cellular level, circadian expression involves transcription factors and epigenetic remodelers, with environmental signals contributing flexibility. Circadian disruption links to diverse diseases, emphasizing the urgency to comprehend the underlying mechanisms. This review explores the communication between the environment and chromatin, focusing on histone post-translational modifications. Special attention is given to the significance of histone methylation in circadian rhythms and metabolic control, highlighting its potential role as a crucial link between metabolism and circadian rhythms. Understanding these molecular intricacies holds promise for preventing and treating complex diseases associated with circadian disruption.

Alterations in Circadian Rhythms, Sleep, and Physical Activity in COVID-19: Mechanisms, Interventions, and Lessons for the Future

Although the world is acquitting from the throes of COVID-19 and returning to the regularity of life, its effects on physical and mental health are prominently evident in the post-pandemic era. The pandemic subjected us to inadequate sleep and physical activities, stress, irregular eating patterns, and work hours beyond the regular rest-activity cycle. Thus, perturbing the synchrony of the regular circadian clock functions led to chronic psychiatric and neurological disorders and poor immunological response in several COVID-19 survivors. Understanding the links between the host immune system and viral replication machinery from a clock-infection biology perspective promises novel avenues of intervention. Behavioral improvements in our daily lifestyle can reduce the severity and expedite the convalescent stage of COVID-19 by maintaining consistent eating, sleep, and physical activity schedules. Including dietary supplements and nutraceuticals with prophylactic value aids in combating COVID-19, as their deficiency can lead to a higher risk of infection, vulnerability, and severity of COVID-19. Thus, besides developing therapeutic measures, perpetual healthy practices could also contribute to combating the upcoming pandemics. This review highlights the impact of the COVID-19 pandemic on biological rhythms, sleep-wake cycles, physical activities, and eating patterns and how those disruptions possibly contribute to the response, severity, and outcome of SARS-CoV-2 infection.

Crosstalk between circadian clocks and pathogen niche

Circadian rhythms are intrinsic 24-hour oscillations found in nearly all life forms. They orchestrate key physiological and behavioral processes, allowing anticipation and response to daily environmental changes. These rhythms manifest across entire organisms, in various organs, and through intricate molecular feedback loops that govern cellular oscillations. Recent studies describe circadian regulation of pathogens, including parasites, bacteria, viruses, and fungi, some of which have their own circadian rhythms while others are influenced by the rhythmic environment of hosts. Pathogens target specific tissues and organs within the host to optimize their replication. Diverse cellular compositions and the interplay among various cell types create unique microenvironments in different tissues, and distinctive organs have unique circadian biology. Hence, residing pathogens are exposed to cyclic conditions, which can profoundly impact host-pathogen interactions. This review explores the influence of circadian rhythms and mammalian tissue-specific interactions on the dynamics of pathogen-host relationships. Overall, this demonstrates the intricate interplay between the body's internal timekeeping system and its susceptibility to pathogens, which has implications for the future of infectious disease research and treatment.

Metabolic and circadian inputs encode anticipatory biogenesis of hepatic fed microRNAs

Starvation and refeeding are mostly unanticipated in the wild in terms of duration, frequency, and nutritional value of the refed state. Notwithstanding this, organisms mount efficient and reproducible responses to restore metabolic homeostasis. Hence, it is intuitive to invoke expectant molecular mechanisms that build anticipatory responses to enable physiological toggling during fed-fast cycles. In this regard, we report anticipatory biogenesis of oscillatory hepatic microRNAs that peak during a fed state and inhibit starvation-responsive genes. Our results clearly demonstrate that the levels of primary and precursor microRNA transcripts increase during a fasting state, in anticipation of a fed response. We delineate the importance of both metabolic and circadian cues in orchestrating hepatic fed microRNA homeostasis in a physiological setting. Besides illustrating metabo-endocrine control, our findings provide a mechanistic basis for the overarching influence of starvation on anticipatory biogenesis. Importantly, by using pharmacological agents that are widely used in clinics, we point out the high potential of interventions to restore homeostasis of hepatic microRNAs, whose deregulated expression is otherwise well established to cause metabolic diseases.

Using routinely collected clinical data for circadian medicine: A review of opportunities and challenges

A wealth of data is available from electronic health records (EHR) that are collected as part of routine clinical care in hospitals worldwide. These rich, longitudinal data offer an attractive object of study for the field of circadian medicine, which aims to translate knowledge of circadian rhythms to improve patient health. This narrative review aims to discuss opportunities for EHR in studies of circadian medicine, highlight the methodological challenges, and provide recommendations for using these data to advance the field. In the existing literature, we find that data collected in real-world clinical settings have the potential to shed light on key questions in circadian medicine, including how 24-hour rhythms in clinical features are associated with-or even predictive of-health outcomes, whether the effect of medication or other clinical activities depend on time of day, and how circadian rhythms in physiology may influence clinical reference ranges or sampling protocols. However, optimal use of EHR to advance circadian medicine requires careful consideration of the limitations and sources of bias that are inherent to these data sources. In particular, time of day influences almost every interaction between a patient and the healthcare system, creating operational 24-hour patterns in the data that have little or nothing to do with biology. Addressing these challenges could help to expand the evidence base for the use of EHR in the field of circadian medicine.

Polymerase-Based Signal Delay for Temporally Regulating DNA Involved Reactions, Programming Dynamic Molecular Systems, and Biomimetic Sensing

Complex temporal molecular signals play a pivotal role in the intricate biological pathways of living organisms, and cells exhibit the ability to transmit and receive information by intricately managing the temporal dynamics of their signaling molecules. Although biomimetic molecular networks are successfully engineered outside of cells, the capacity to precisely manipulate temporal behaviors remains limited. In this study, the catalysis activity of isothermal DNA polymerase (DNAP) through combined use of molecular dynamics simulation analysis and fluorescence assays is first characterized. DNAP-driven delay in signal strand release ranged from 100 to 102 min, which is achieved through new strategies including the introduction of primer overhangs, utilization of inhibitory reagents, and alteration of DNA template lengths. The results provide a deeper insight into the underlying mechanisms of temporal control DNAP-mediated primer extension and DNA strand displacement reactions. Then, the regulated DNAP catalysis reactions are applied in temporal modulation of downstream DNA-involved reactions, the establishment of dynamic molecular signals, and the generation of barcodes for multiplexed detection of target genes. The utility of DNAP-based signal delay as a dynamic DNA nanotechnology extends beyond theoretical concepts and achieves practical applications in the fields of cell-free synthetic biology and bionic sensing.

Intertwined relationship of dynamin-related protein 1, mitochondrial metabolism and circadian rhythm

In recent years, mitochondria have gained significant interest in the field of biomedical research due to their impact on human health and ageing. As mitochondrial dynamics are strongly controlled by clock genes, misalignment of the circadian rhythm leads to adverse metabolic health effects. In this review, by exploring various aspects of research and potential links, we hope to update the current understanding of the intricate relationship between DRP1-mediated mitochondrial dynamics and changes in circadian rhythmicity leading to health issues. Thus, this review addresses the potential bidirectional relationships between DRP1-linked mitochondrial function and circadian rhythm misalignment, their impact on different metabolic pathways, and the potential therapeutics for metabolic and systemic disorders.

The intersection between ghrelin, metabolism and circadian rhythms

Despite the growing popular interest in sleep and diet, many gaps exist in our scientific understanding of the interaction between circadian rhythms and metabolism. In this Review, we explore a promising, bidirectional role for ghrelin in mediating this interaction. Ghrelin both influences and is influenced by central and peripheral circadian systems. Specifically, we focus on how ghrelin impacts outputs of circadian rhythm, including neuronal activity, circulating growth hormone levels, locomotor activity and eating behaviour. We also consider the effects of circadian rhythms on ghrelin expression and the consequences of disrupted circadian patterns, such as shift work and jet lag, on ghrelin secretion. Our Review is aimed at both the casual reader interested in gaining more insight into the scientific context surrounding the trending topics of sleep and metabolism, as well as experienced scientists in the fields of ghrelin and circadian biology seeking inspiration and a comprehensive overview of how these fields are related.

Energy balance drives diurnal and nocturnal brain transcriptome rhythms

Plasticity in daily timing of activity has been observed in many species, yet the underlying mechanisms driving nocturnality and diurnality are unknown. By regulating how much wheel-running activity will be rewarded with a food pellet, we can manipulate energy balance and switch mice to be nocturnal or diurnal. Here, we present the rhythmic transcriptome of 21 tissues, including 17 brain regions, sampled every 4 h over a 24-h period from nocturnal and diurnal male CBA/CaJ mice. Rhythmic gene expression across tissues comprised different sets of genes with minimal overlap between nocturnal and diurnal mice. We show that non-clock genes in the suprachiasmatic nucleus (SCN) change, and the habenula was most affected. Our results indicate that adaptive flexibility in daily timing of behavior is supported by gene expression dynamics in many tissues and brain regions, especially in the habenula, which suggests a crucial role for the observed nocturnal-diurnal switch.

Circadian Rhythms in Cardiovascular Metabolism

Energetic demand and nutrient supply fluctuate as a function of time-of-day, in alignment with sleep-wake and fasting-feeding cycles. These daily rhythms are mirrored by 24-hour oscillations in numerous cardiovascular functional parameters, including blood pressure, heart rate, and myocardial contractility. It is, therefore, not surprising that metabolic processes also fluctuate over the course of the day, to ensure temporal needs for ATP, building blocks, and metabolism-based signaling molecules are met. What has become increasingly clear is that in addition to classic signal-response coupling (termed reactionary mechanisms), cardiovascular-relevant cells use autonomous circadian clocks to temporally orchestrate metabolic pathways in preparation for predicted stimuli/stresses (termed anticipatory mechanisms). Here, we review current knowledge regarding circadian regulation of metabolism, how metabolic rhythms are synchronized with cardiovascular function, and whether circadian misalignment/disruption of metabolic processes contribute toward the pathogenesis of cardiovascular disease.

A Comprehensive Overview of the Neural Mechanisms of Light Therapy

Light is a powerful environmental factor influencing diverse brain functions. Clinical evidence supports the beneficial effect of light therapy on several diseases, including depression, cognitive dysfunction, chronic pain, and sleep disorders. However, the precise mechanisms underlying the effects of light therapy are still not well understood. In this review, we critically evaluate current clinical evidence showing the beneficial effects of light therapy on diseases. In addition, we introduce the research progress regarding the neural circuit mechanisms underlying the modulatory effects of light on brain functions, including mood, memory, pain perception, sleep, circadian rhythm, brain development, and metabolism.

Epigenetic control of circadian clocks by environmental signals

Circadian clocks have evolved to enable organisms to respond to daily environmental changes. Maintaining a robust circadian rhythm under various perturbations and stresses is essential for the fitness of an organism. In the core circadian oscillator conserved in eukaryotes (from fungi to mammals), a negative feedback loop based on both transcription and translation drives circadian rhythms. The expression of circadian clock genes depends both on the binding of transcription activators at the promoter and on the chromatin state of the clock genes, and epigenetic modifications of chromatin are crucial for transcriptional regulation of circadian clock genes. Herein we review current knowledge of epigenetic regulation of circadian clock mechanisms and discuss how environmental cues can control clock gene expression by affecting chromatin states.

Single-cell transcriptomic profiling of heart reveals ANGPTL4 linking fibroblasts and angiogenesis in heart failure with preserved ejection fraction

INTRODUCTION

Despite the high morbidity and mortality, the effective therapies for heart failure with preserved fraction (HFpEF) are limited as the poor understand of its pathophysiological basis.

OBJECTIVE

This study was aimed to characterize the cellular heterogeneity and potential mechanisms of HFpEF at single-cell resolution.

METHODS

An HFpEF mouse model was induced by a high-fat diet with N-nitro-L-arginine methyl ester. Cells from the hearts were subjected to single-cell sequencing. The key protein expression was measured with Immunohistochemistry and immunofluorescence staining.

RESULTS

In HFpEF hearts, myocardial fibroblasts exhibited higher levels of fibrosis. Furthermore, an increased number of fibroblasts differentiated into high-metabolism and high-fibrosis phenotypes. The expression levels of genes encoding certain pro-angiogenic secreted proteins were decreased in the HFpEF group, as confirmed by bulk RNA sequencing. Additionally, the proportion of the endothelial cell (EC) lineages in the HFpEF group was significantly downregulated, with low angiogenesis and high apoptosis phenotypes observed in these EC lineages. Interestingly, the fibroblasts in the HFpEF heart might cross-link with the EC lineages via over-secretion of ANGPTL4, thus displaying an anti-angiogenic function. Immunohistochemistry and immunofluorescence staining then revealed the downregulation of vascular density and upregulation of ANGPTL4 expression in HFpEF hearts. Finally, we predicted ANGPTL4as a potential druggable target using DrugnomeAI.

CONCLUSION

In conclusion, this study comprehensively characterized the angiogenesis impairment in HFpEF hearts at single-cell resolution and proposed that ANGPTL4 secretion by fibroblasts may be a potential mechanism underlying this angiogenic abnormality.

"Time Is out of Joint" in Pluripotent Stem Cells: How and Why

The circadian rhythm is necessary for the homeostasis and health of living organisms. Molecular clocks interconnected by transcription/translation feedback loops exist in most cells of the body. A puzzling exemption to this, otherwise, general biological hallmark is given by the cell physiology of pluripotent stem cells (PSCs) that lack circadian oscillations gradually acquired following their in vivo programmed differentiation. This process can be nicely phenocopied following in vitro commitment and reversed during the reprogramming of somatic cells to induce PSCs. The current understanding of how and why pluripotency is "time-uncoupled" is largely incomplete. A complex picture is emerging where the circadian core clockwork is negatively regulated in PSCs at the post-transcriptional/translational, epigenetic, and other-clock-interaction levels. Moreover, non-canonical functions of circadian core-work components in the balance between pluripotency identity and metabolic-driven cell reprogramming are emerging. This review selects and discusses results of relevant recent investigations providing major insights into this context.

Comprehensive analysis of the prognosis and biological significance of RORβ in head and neck squamous cell carcinoma

Recent studies have shown that abnormal expression of the core circadian clock gene, retinoic acid-related orphan receptor β (RORβ ), is closely associated with the occurrence and progression of various malignant tumors. However, the expression and function of RORβ in head and neck squamous cell carcinoma (HNSCC) remains unclear. Here, we comprehensively investigated the altered expression, clinical significance, prognostic value, and biological functions of RORβ in HNSC, as well as its correlation with changes in the tumor immune microenvironment. We found that RORβ expression was decreased in HNSC and 19 other cancers. Low RORβ expression was significantly associated with tumor size, clinical stage, and survival time in HNSC patients, indicating that it may have diagnostic and prognostic value in HNSCC. Epigenetic analysis showed that the promoter methylation level of RORβ was significantly higher in HNSCC compared to adjacent noncancerous tissues. Furthermore, RORβ hypermethylation was significantly associated with low expression levels of RORβ and poor prognosis in HNSCC patients (p < 0.05). Enrichment analysis found that RORβ was involved in immune system regulation and T-cell activation, as well as the PI3K/AKT and ECM receptors interaction pathways. In vitro assays revealed that RORβ regulated the proliferation, migration and invasion ability of HNSCC cells. Additionally, we found that RORβ expression was significantly correlated with changes in the tumor immune microenvironment, suggesting it may affect prognosis by regulating immune infiltration in HNSC patients. Therefore, RORβ may serve as a potential prognostic biomarker and therapeutic target for HNSCC patients.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Biologically informed deep learning for explainable epigenetic clocks

Ageing is often characterised by progressive accumulation of damage, and it is one of the most important risk factors for chronic disease development. Epigenetic mechanisms including DNA methylation could functionally contribute to organismal aging, however the key functions and biological processes may govern ageing are still not understood. Although age predictors called epigenetic clocks can accurately estimate the biological age of an individual based on cellular DNA methylation, their models have limited ability to explain the prediction algorithm behind and underlying key biological processes controlling ageing. Here we present XAI-AGE, a biologically informed, explainable deep neural network model for accurate biological age prediction across multiple tissue types. We show that XAI-AGE outperforms the first-generation age predictors and achieves similar results to deep learning-based models, while opening up the possibility to infer biologically meaningful insights of the activity of pathways and other abstract biological processes directly from the model.

Tuning of liver circadian transcriptome rhythms by thyroid hormone state in male mice

Thyroid hormones (THs) are important regulators of systemic energy metabolism. In the liver, they stimulate lipid and cholesterol turnover and increase systemic energy bioavailability. It is still unknown how the TH state interacts with the circadian clock, another important regulator of energy metabolism. We addressed this question using a mouse model of hypothyroidism and performed circadian analyses. Low TH levels decreased locomotor activity, food intake, and body temperature mostly in the active phase. Concurrently, liver transcriptome profiling showed only subtle effects compared to elevated TH conditions. Comparative circadian transcriptome profiling revealed alterations in mesor, amplitude, and phase of transcript levels in the livers of low-TH mice. Genes associated with cholesterol uptake, biosynthesis, and bile acid secretion showed reduced mesor. Increased and decreased cholesterol levels in the serum and liver were identified, respectively. Combining data from low- and high-TH conditions allowed the identification of 516 genes with mesor changes as molecular markers of the liver TH state. We explored these genes and created an expression panel that assesses liver TH state in a time-of-day dependent manner. Our findings suggest that the liver has a low TH action under physiological conditions. Circadian profiling reveals genes as potential markers of liver TH state.

Circadian regulated control of myocardial ischemia-reperfusion injury

Circadian mechanisms have been associated with the pathogenesis of a variety of cardiovascular diseases, including myocardial ischemia-reperfusion injury (I-R). Myocardial ischemia resulting from impaired oxygen delivery to cardiac muscle sets into motion a cascade of cellular events that paradoxically triggers greater cardiac dysfunction upon reinstitution of coronary blood supply, a phenomenon known as I-R. I-R injury has been attributed to a number of cellular defects including increased reactive oxygen species (ROS), increased intracellular calcium and impaired mitochondrial bioenergetics that ultimately lead to cardiac cell death, ventricular remodeling and heart failure. Emerging evidence has identified a strong correlation between cellular defects that underlie I-R and the disrupted circadian. In fact, recent studies have shown that circadian dysfunction exacerbates cardiac injury following MI from impaired cellular quality control mechanisms such as autophagy, which are vital in the clearance of damaged cellular proteins and organelles such as mitochondria from the cell. The accumulation of cellular debris is posited as the central underlying cause of excessive cardiac cell death and ventricular dysfunction following MI. The complexities that govern the interplay between circadian biology and I-R injury following MI is at its infancy and understanding how circadian misalignment, such as in shift workers impacts I-R injury is of great scientific and clinical importance toward development of new therapeutic strategies using chronotherapy and circadian regulation to mitigate cardiac injury and improve cardiac outcomes after injury. In this review, we highlight recent advances in circadian biology and adaptive cellular quality control mechanisms that influence cardiac injury in response to MI injury with a specific focus on how circadian biology can be utilized to further cardiovascular medicine and patient care.

Exercise training induces alteration of clock genes and myokines expression in tumor-bearing mice

To investigate the impact of different exercise training schedules (following a fixed schedule or at random times of the day) on clock genes and myokine expression patterns in the skeletal muscle of tumor-bearing mice. Mice were divided into three groups: tumor (LLC), tumor + exercise training (LLC + T) always performed at the same time of the day (ZT2) and exercise training at random times of the day (ZTAlt). Mice were inoculated subcutaneously with Lewis lung carcinoma cells. The gastrocnemius muscle was dissected and the clock gene expression (Clock/Per1/Per2/Per3/Rev-Erbα/GAPDH) was investigated by quantitative reverse transcription polymerase chain reaction with SYBR® Green. Myokine content in muscle (tumour necrosis factor alpha/IL-10/IL-4) was assessed by enzyme-linked immunosorbent assay. At the end of the protocol, the trained groups showed a reduction in total weight, when compared to Lewis lung carcinoma. Tumor weight was lower in the LLC + T (ZTAlt), when compared to LLC. Clock gene mRNA expression showed a significant increase for ZT20 in the groups that performed physical exercise at LLC + T (ZTAlt), when compared with LLC. The Per family showed increased mRNA expression in ZT4 in both trained mice groups, when compared with LLC. LLC + T (ZTAlt) presented reduction of the expression of anti-inflammatory myokines (Il-10/IL-4) during the night, compared with LLC + T(ZT2). Exercise training is able to induce marked modification of clock gene expression and of the production of myokines, in a way that is dependent on schedule exercise training strategy. Taken together, the results show that exercise is a potent Zeitgeber and may thus contribute to change clock genes expression and myokines that are able to reduce the tumor weight.

The impact of prolonged fasting on 24h energy metabolism and its 24h rhythmicity in healthy, lean males: A randomized cross-over trial

OBJECTIVE

Human energy expenditure and substrate oxidation are under circadian control and food intake is a time cue for the human biological clock, leading to 24h feeding-fasting cycles in energy and substrate metabolism. In recent years, (intermittent) fasting protocols have also become popular to improve metabolic health. Here, we aimed to investigate the impact of food intake on the 24h patterns of energy metabolism as well as to provide data on the timeline of changes in energy metabolism that occur upon an extended period of fasting.

RESEARCH DESIGN AND METHODS

In a randomized, cross-over design, twelve healthy males underwent a 60h fast which was compared to a 60h fed condition. In the fed condition meals were provided at energy balance throughout the study. Conditions were separated by a two week period of habitual diet. Volunteers resided in a respiration chamber for the entire 60h to measure energy expenditure and substrate oxidation hour by hour. Volunteers performed a standardized activity protocol while in the chamber. Blood samples were drawn after 12, 36 and 60h.

RESULTS

Immediately following the breakfast meal (in the fed condition), fat oxidation became higher in the fasted condition compared to the fed condition and remained elevated throughout the study period. The initial rapid increase in fat oxidation corresponded with a decline in the hepatokine activin A (r = -0.86, p = 0.001). The contribution of fat oxidation to total energy expenditure gradually increased with extended abstinence from food, peaking after 51h of fasting at 160 mg/min. Carbohydrate oxidation stabilized at a low level during the second day of fasting and averaged around 60 mg/min with only modest elevations in response to physical activity. Although 24h energy expenditure was significantly lower with prolonged fasting (11.0 ± 0.4 vs 9.8 ± 0.2 and 10.9 ± 0.3 vs 10.3 ± 0.3 MJ in fed vs fasting, day 2 and 3 respectively, p < 0.01), the 24h fluctuations in energy expenditure were comparable between the fasted and fed condition. The fluctuations in substrate oxidation were, however, significantly (p < 0.001 for both carbohydrate and fat oxidation) altered in the fasted state, favouring fat oxidation.

CONCLUSIONS

Energy expenditure displays a day-night rhythm, which is independent of food intake. In contrast, the day-night rhythm of both carbohydrate and fat oxidation is mainly driven by food intake. Upon extended fasting, the absolute rate of fat oxidation rapidly increases and keeps increasing during a 60h fast, whereas carbohydrate oxidation becomes progressively diminished.

TRIAL REGISTRATION

www.trialregister.nl NTR 2042.

Connecting the Dots: Potential Interactions Between Sex Hormones and the Circadian System During Memory Consolidation

Both the circadian clock and sex hormone signaling can strongly influence brain function, yet little is known about how these 2 powerful modulatory systems might interact during complex neural processes like memory consolidation. Individually, the molecular components and action of each of these systems have been fairly well-characterized, but there is a fundamental lack of information about how these systems cooperate. In the circadian system, clock genes function as timekeeping molecules that convey time-of-day information on a well-stereotyped cycle that is governed by the suprachiasmatic nucleus. Keeping time is particularly important to synchronize various physiological processes across the brain and body, including those that regulate memory consolidation. Similarly, sex hormones are powerful modulators of memory, with androgens, estrogens, and progestins, all influencing memory consolidation within memory-relevant brain regions like the hippocampus. Despite clear evidence that each system can influence memory individually, exactly how the circadian and hormonal systems might interact to impact memory consolidation remains unclear. Research investigating either sex hormone action or circadian gene function within memory-relevant brain regions has unveiled several notable places in which the two systems could interact to control memory. Here, we bring attention to known interactions between the circadian clock and sex hormone signaling. We then review sex hormone-mediated control of memory consolidation, highlighting potential nodes through which the circadian system might interact during memory formation. We suggest that the bidirectional relationship between these two systems is essential for proper control of memory formation based on an animal's hormonal and circadian state.

Dissecting the daily feeding pattern: Peripheral CLOCK/CYCLE generate the feeding/fasting episodes and neuronal molecular clocks synchronize them

A 24-h rhythm of feeding behavior, or synchronized feeding/fasting episodes during the day, is crucial for survival. Internal clocks and light input regulate rhythmic behaviors, but how they generate feeding rhythms is not fully understood. Here we aimed to dissect the molecular pathways that generate daily feeding patterns. By measuring the semidiurnal amount of food ingested by single flies, we demonstrate that the generation of feeding rhythms under light:dark conditions requires quasimodo (qsm) but not molecular clocks. Under constant darkness, rhythmic feeding patterns consist of two components: CLOCK (CLK) in digestive/metabolic tissues generating feeding/fasting episodes, and the molecular clock in neurons synchronizing them to subjective daytime. Although CLK is a part of the molecular clock, the generation of feeding/fasting episodes by CLK in metabolic tissues was independent of molecular clock machinery. Our results revealed novel functions of qsm and CLK in feeding rhythms in Drosophila.

Effect of circadian rhythm on NAD and other metabolites in human brain

Nicotinamide Adenine Dinucleotide (NAD) plays a central role in the master circadian clock of the brain (the suprachiasmatic nuclei, SCN) as demonstrated in many model organisms. NAD acts as an enzyme co-factor and substrate and its modulation was found to be tightly regulated to the periodicity of the cycles. However, in human brain, the effect of the circadian rhythm (CR) on the metabolism of the SCN and other brain regions is poorly understood. We conducted a magnetic resonance spectroscopy (MRS) study at a high magnetic field, measuring the occipital brain NAD levels and other metabolites in two different morning and afternoon diurnal states in 25 healthy participants. Salivary cortisol levels were determined to confirm that the experiment was done in two chronologically different physiological conditions, and a behavioral test of risk-taking propensity was administered. Overall, we found that the CR did not significantly affect NAD levels in the occipital brain region. The other brain metabolites measured, including lactate, were not significantly affected by the CR either, except for taurine. The CR did impact risk-taking behavior and salivary cortisol level, confirming that the participants were in two circadian different behavioral and physiological states in the morning and in the afternoon. Measurement of the CR effect on NAD and taurine levels in other brain regions might provide stronger effects.

Ruscogenin timing administration mitigates cerebral ischemia-reperfusion injury through regulating circadian genes and activating Nrf2 pathway

BACKGROUND

Ruscogenin (Rus), a steroidal sapogenin extracted from Ophiopogon japonicus (L. f.) Ker-Gawl., has the effect of alleviating cerebral ischemia-reperfusion injury (IRI), acute lung injury. At present, the chronopharmacological effects of Rus are still unknown.

PURPOSE

This study explored the alleviating effect and mechanism of Rus timing administration on mice cerebral IRI.

METHODS

The animals in different groups were administrated Rus (10 mg/kg) by gavage at four time points (23:00-01:00, 05:00-07:00, 11:00-13:00, 17:00-19:00) respectively for 3 days. On the 4th day, middle cerebral artery occlusion (MCAO) surgery was operated during 5:00-7:00. Behavioral tests were executed and the brain was collected for infarct volume, qPCR and immunoblot detection. The levels of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin-1beta (IL-1β) and inducible nitric oxide synthase (iNOS) were detected by qPCR. Glutathione (GSH), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in serum and cerebral cortex were detected. The clock genes were tested by western blot. Based on these results, 17:00-19:00 was selected to administrate Rus for further mechanism study and Nrf2 blocker group was administrated all-trans-retinoic acid (ATRA) at 14:00 for 3 days.

RESULTS

Administration of Rus reduced cerebral infarcted volume, ameliorated the behavior score and upregulated the mRNA and protein expression of Per1, Bmal1, Clock, Rev-erbα, transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), quinone oxidoreductase 1 (NQO1). Administration of Rus during 17:00-19:00 had better preventive effect than other three time points. Combined administration of ATRA blunted the preventive effect of Rus.

CONCLUSION

The preventive effect of Rus is affected by the time of administration, which was regulated by Nrf2 pathway. Taken together, we provide solid evidence to suggest that different administration time point affect the effectiveness of Rus in alleviating IRI.

Role of Bmal1 and Gut Microbiota in Alzheimer's Disease and Parkinson's Disease Pathophysiology: The Probable Effect of Melatonin on Their Association

In recent years, the role of new factors in the pathophysiology of neurodegenerative diseases has been investigated. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases worldwide. Although pathological changes such as the accumulation of aggregated proteins in the brain and inflammatory responses are known as the main factors involved in the development of these diseases, new studies show the role of gut microbiota and circadian rhythm in the occurrence of these changes. However, the association between circadian rhythm and gut microbiota in AD and PD has not yet been investigated. Recent results propose that alterations in circadian rhythm regulators, mainly Bmal1, may regulate the abundance of gut microbiota. This correlation has been linked to the regulation of the expression of immune-related genes and Bmal-1 mediated oscillation of IgA and hydrogen peroxide production. These data seem to provide new insight into the molecular mechanism of melatonin inhibiting the progression of AD and PD. Therefore, this manuscript aims to review the role of the gut microbiota and circadian rhythm in health and AD and PD and also presents a hypothesis on the effect of melatonin on their communication.

Acute and Repeated Ozone Exposures Differentially Affect Circadian Clock Gene Expression in Mice

Circadian rhythms have an established role in regulating physiological processes, such as inflammation, immunity, and metabolism. Ozone, a common environmental pollutant with strong oxidative potential, is implicated in lung inflammation/injury in asthmatics. However, whether O3 exposure affects the expression of circadian clock genes in the lungs is not known. In this study, changes in the expression of core clock genes are analyzed in the lungs of adult female and male mice exposed to filtered air (FA) or O3 using qRT-PCR. The findings are confirmed using an existing RNA-sequencing dataset from repeated FA- and O3 -exposed mouse lungs and validated by qRT-PCR. Acute O3 exposure significantly alters the expression of clock genes in the lungs of females (Per1, Cry1, and Rora) and males (Per1). RNA-seq data revealing sex-based differences in clock gene expression in the airway of males (decreased Nr1d1/Rev-erbα) and females (increased Skp1), parenchyma of females and males (decreased Nr1d1 and Fbxl3 and increased Bhlhe40 and Skp1), and alveolar macrophages of males (decreased Arntl/Bmal1, Per1, Per2, Prkab1, and Prkab2) and females (increased Cry2, Per1, Per2, Csnk1d, Csnk1e, Prkab2, and Fbxl3). These findings suggest that lung inflammation caused by O3 exposure affects clock genes which may regulate key signaling pathways.

Sweet treats before sleep disrupt the clock system and increase metabolic risk markers in healthy rats

AIM

Biological rhythms are endogenously generated natural cycles that act as pacemakers of different physiological mechanisms and homeostasis in the organism, and whose disruption increases metabolic risk. The circadian rhythm is not only reset by light but it is also regulated by behavioral cues such as timing of food intake. This study investigates whether the chronic consumption of a sweet treat before sleeping can disrupt diurnal rhythmicity and metabolism in healthy rats.

METHODS

For this, 32 Fischer rats were administered daily a low dose of sugar (160 mg/kg, equivalent to 2.5 g in humans) as a sweet treat at 8:00 a.m. or 8:00 p.m. (ZT0 and ZT12, respectively) for 4 weeks. To elucidate diurnal rhythmicity of clock gene expression and metabolic parameters, animals were sacrificed at different times, including 1, 7, 13, and 19 h after the last sugar dose (ZT1, ZT7, ZT13, and ZT19).

RESULTS

Increased body weight gain and higher cardiometabolic risk were observed when sweet treat was administered at the beginning of the resting period. Moreover, central clock and food intake signaling genes varied depending on snack time. Specifically, the hypothalamic expression of Nampt, Bmal1, Rev-erbα, and Cart showed prominent changes in their diurnal expression pattern, highlighting that sweet treat before bedtime disrupts hypothalamic control of energy homeostasis.

CONCLUSIONS

These results show that central clock genes and metabolic effects following a low dose of sugar are strongly time-dependent, causing higher circadian metabolic disruption when it is consumed at the beginning of the resting period, that is, with the late-night snack.

Circadian regulation of liver function: from molecular mechanisms to disease pathophysiology

A wide variety of liver functions are regulated daily by the liver circadian clock and via systemic circadian control by other organs and cells within the gastrointestinal tract as well as the microbiome and immune cells. Disruption of the circadian system, as occurs during jetlag, shift work or an unhealthy lifestyle, is implicated in several liver-related pathologies, ranging from metabolic diseases such as obesity, type 2 diabetes mellitus and nonalcoholic fatty liver disease to liver malignancies such as hepatocellular carcinoma. In this Review, we cover the molecular, cellular and organismal aspects of various liver pathologies from a circadian viewpoint, and in particular how circadian dysregulation has a role in the development and progression of these diseases. Finally, we discuss therapeutic and lifestyle interventions that carry health benefits through support of a functional circadian clock that acts in synchrony with the environment.

Circadian regulation of liver metabolism: experimental approaches in human, rodent, and cellular models

Circadian rhythms are endogenous oscillations with approximately a 24-h period that allow organisms to anticipate the change between day and night. Disruptions that desynchronize or misalign circadian rhythms are associated with an increased risk of cardiometabolic disease. This review focuses on the liver circadian clock as relevant to the risk of developing metabolic diseases including nonalcoholic fatty liver disease (NAFLD), insulin resistance, and type 2 diabetes (T2D). Many liver functions exhibit rhythmicity. Approximately 40% of the hepatic transcriptome exhibits 24-h rhythms, along with rhythms in protein levels, posttranslational modification, and various metabolites. The liver circadian clock is critical for maintaining glucose and lipid homeostasis. Most of the attention in the metabolic field has been directed toward diet, exercise, and rather little to modifiable risks due to circadian misalignment or disruption. Therefore, the aim of this review is to systematically analyze the various approaches that study liver circadian pathways, targeting metabolic liver diseases, such as diabetes, nonalcoholic fatty liver disease, using human, rodent, and cell biology models.NEW & NOTEWORTHY Over the past decade, there has been an increased interest in understanding the intricate relationship between circadian rhythm and liver metabolism. In this review, we have systematically searched the literature to analyze the various experimental approaches utilizing human, rodent, and in vitro cellular approaches to dissect the link between liver circadian rhythms and metabolic disease.

Bioinformatics Integrative Analysis of Circadian Rhythms Effects on Atopic Dermatitis and Dendritic Cells

Background

Atopic dermatitis (AD) is an allergic inflammatory skin disease caused by aberrant and over-reactive immune response. Although circadian rhythm disruption is implicated in multiple immunoinflammatory conditions, including AD, the mechanisms at the molecular level underlying AD and circadian rhythms remain elusive.

Methods

Bulk and single-cell RNA-sequencing data of AD patients were acquired from the Gene Expression Omnibus, including GSE121212, GSE120721, and GSE153760 datasets. A single-sample gene set enrichment analysis was performed to estimate circadian rhythm gene expression levels. A differential expression analysis was utilized to identify the key candidate genes in AD. CIBERSORT was used to quantify the proportions of immune cells, and the R package "Seurat" was utilized to investigate single-cell RNA-sequencing data.

Results

Circadian rhythm gene expression levels were lower in AD skin samples than in normal skin samples. Dendritic cells were significantly upregulated and negatively correlated with circadian rhythm gene expression levels in AD patients. Compared with circadian rhythm-related genes in the control samples, ARNTL2, NOCT, and RORC were differentially expressed in AD; ARNTL2 and NOCT were significantly upregulated, whereas RORC was significantly downregulated in AD. ARNTL2, NOCT, and RORC also showed robust abilities to diagnose AD. We validated that the abundance of the dendritic cell was positively correlated with the ARNTL2 and NOCT expression levels using bulk RNA-sequencing data of the GSE121212 and single-cell RNA-sequencing data of the GSE153760. Moreover, the functional enrichment analysis showed that the IL-17 and NF-κB signaling pathways, Th1 and Th2 cell differentiations, and primary immunodeficiency, were enriched in AD patients.

Conclusion

The findings of this study suggested that the circadian rhythm is involved in the progression of AD, and RNTL2, NOCT, and RORC as well as dendritic cells are differentially expressed in AD. These findings could be used to introduce diagnostic and chronotherapeutic modalities for AD.

Intermittent fasting-the future treatment in NASH patients?

NASH is one of the leading causes of chronic liver disease with the potential of evolving towards end-stage liver disease and HCC, even in the absence of cirrhosis. Apart from becoming an increasingly prevalent indication for liver transplantation in cirrhotic and HCC patients, its burden on the healthcare system is also exerted by the increased number of noncirrhotic NASH patients. Intermittent fasting has recently gained more interest in the scientific community as a possible treatment approach for different components of metabolic syndrome. Basic science and clinical studies have shown that apart from inducing body weight loss, improving cardiometabolic parameters, namely blood pressure, cholesterol, and triglyceride levels; insulin and glucose metabolism; intermittent fasting can reduce inflammatory markers, endoplasmic reticulum stress, oxidative stress, autophagy, and endothelial dysfunction, as well as modulate gut microbiota. This review aims to further explore the main NASH pathogenetic metabolic drivers on which intermittent fasting can act upon and improve the prognosis of the disease, and summarize the current clinical evidence.

Insights on the role of L-lactate as a signaling molecule in skin aging

L-lactate is a catabolite from the anaerobic metabolism of glucose, which plays a paramount role as a signaling molecule in various steps of the cell survival. Its activity, as a master tuner of many mechanisms underlying the aging process, for example in the skin, is still presumptive, however its crucial position in the complex cross-talk between mitochondria and the process of cell survival, should suggest that L-lactate may be not a simple waste product but a fine regulator of the aging/survival machinery, probably via mito-hormesis. Actually, emerging evidence is highlighting that ROS are crucial in the signaling of skin health, including mechanisms underlying wound repair, renewal and aging. The ROS, including superoxide anion, hydrogen peroxide, and nitric oxide, play both beneficial and detrimental roles depending upon their levels and cellular microenvironment. Physiological ROS levels are essential for cutaneous health and the wound repair process. Aberrant redox signaling activity drives chronic skin disease in elderly. On the contrary, impaired redox modulation, due to enhanced ROS generation and/or reduced levels of antioxidant defense, suppresses wound healing via promoting lymphatic/vascular endothelial cell apoptosis and death. This review tries to elucidate this issue.

Recent advances in the study of circadian rhythm disorders that induce diabetic retinopathy

Diabetic retinopathy (DR) is a severe microvascular complication of diabetes mellitus and a major cause of blindness in young adults. Multiple potential factors influence DR; however, the exact mechanisms are poorly understood. Advanced treatments for DR, including laser therapy, vitrectomy, and intraocular drug injections, slow the disease's progression but fail to cure or reverse visual impairment. Therefore, additional effective methods to prevent and treat DR are required. The biological clock plays a crucial role in maintaining balance in the circadian rhythm of the body. Poor lifestyle habits, such as irregular routines and high-fat diets, may disrupt central and limbic circadian rhythms. Disrupted circadian rhythms can result in altered glucose metabolism and obesity. Misaligned central and peripheral clocks lead to a disorder of the rhythm of glucose metabolism, and chronically high sugar levels lead to the development of DR. We observed a disturbance in clock function in patients with diabetes, and a misaligned clock could accelerate the development of DR. In the current study, we examine the relationship between circadian rhythm disorders, diabetes, and DR. We conclude that: 1) abnormal function of the central clock and peripheral clock leads to abnormal glucose metabolism, further causing DR and 2) diabetes causes abnormal circadian rhythms, further exacerbating DR. Thus, our study presents new insights into the prevention and treatment of DR.

Reciprocal regulation between the molecular clock and kidney injury

Tubulointerstitial fibrosis is the common pathological substrate for many etiologies leading to chronic kidney disease. Although perturbations in the circadian rhythm have been associated with renal disease, the role of the molecular clock in the pathogenesis of fibrosis remains incompletely understood. We investigated the relationship between the molecular clock and renal damage in experimental models of injury and fibrosis (unilateral ureteral obstruction, folic acid, and adenine nephrotoxicity), using genetically modified mice with selective deficiencies of the clock components Bmal1, Clock, and Cry We found that the molecular clock pathway was enriched in damaged tubular epithelial cells with marked metabolic alterations. In human tubular epithelial cells, TGFβ significantly altered the expression of clock components. Although Clock played a role in the macrophage-mediated inflammatory response, the combined absence of Cry1 and Cry2 was critical for the recruitment of neutrophils, correlating with a worsening of fibrosis and with a major shift in the expression of metabolism-related genes. These results support that renal damage disrupts the kidney peripheral molecular clock, which in turn promotes metabolic derangement linked to inflammatory and fibrotic responses.