Circadian topology of metabolism

Long-lasting effects of disturbing the circadian rhythm or sleep in adolescence

Circadian rhythms are endogenous, near 24-hour rhythms that regulate a multitude of biological and behavioral processes across the diurnal cycle in most organisms. Over the lifespan, a bell curve pattern emerges in circadian phase preference (i.e. chronotype), with children and adults generally preferring to wake earlier and fall asleep earlier, and adolescents and young adults preferring to wake later and fall asleep later than their adult counterparts. This well-defined shift speaks to the variability of circadian rhythmicity over the lifespan and the changing needs and demands of the brain as an organism develops, particularly in the adolescent period. Indeed, adolescence is known to be a critical period of development during which dramatic neuroanatomical changes are occurring to allow for improved decision-making. Due to the large amount of re-structuring occurring in the adolescent brain, circadian disruptions during this period could have adverse consequences that persist across the lifespan. While the detrimental effects of circadian disruptions in adults have been characterized in depth, few studies have longitudinally assessed the potential long-term impacts of circadian disruptions during adolescence. Here, we will review the evidence that disruptions in circadian rhythmicity during adolescence have effects that persist into adulthood. As biological and social time often conflict in modern society, with school start times misaligned with adolescents' endogenous rhythms, it is critical to understand the long-term impacts of disrupted circadian rhythmicity in adolescence.

Dysfunctional circadian clock accelerates cancer metastasis by intestinal microbiota triggering accumulation of myeloid-derived suppressor cells

Circadian homeostasis in mammals is a key intrinsic mechanism for responding to the external environment. However, the interplay between circadian rhythms and the tumor microenvironment (TME) and its influence on metastasis are still unclear. Here, in patients with colorectal cancer (CRC), disturbances of circadian rhythm and the accumulation of monocytes and granulocytes were closely related to metastasis. Moreover, dysregulation of circadian rhythm promoted lung metastasis of CRC by inducing the accumulation of myeloid-derived suppressor cells (MDSCs) and dysfunctional CD8+ T cells in the lungs of mice. Also, gut microbiota and its derived metabolite taurocholic acid (TCA) contributed to lung metastasis of CRC by triggering the accumulation of MDSCs in mice. Mechanistically, TCA promoted glycolysis of MDSCs epigenetically by enhancing mono-methylation of H3K4 of target genes and inhibited CHIP-mediated ubiquitination of PDL1. Our study links the biological clock with MDSCs in the TME through gut microbiota/metabolites in controlling the metastatic spread of CRC, uncovering a systemic mechanism for cancer metastasis.

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.

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.

Circadian rhythm regulates the function of immune cells and participates in the development of tumors

Circadian rhythms are present in almost all cells and play a crucial role in regulating various biological processes. Maintaining a stable circadian rhythm is essential for overall health. Disruption of this rhythm can alter the expression of clock genes and cancer-related genes, and affect many metabolic pathways and factors, thereby affecting the function of the immune system and contributing to the occurrence and progression of tumors. This paper aims to elucidate the regulatory effects of BMAL1, clock and other clock genes on immune cells, and reveal the molecular mechanism of circadian rhythm's involvement in tumor and its microenvironment regulation. A deeper understanding of circadian rhythms has the potential to provide new strategies for the treatment of cancer and other immune-related diseases.

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.

Early chronotype favors appetite and reduced later day caloric intake among adults with obesity

Late chronotype (LC) is related to obesity and altered food intake throughout the day. But whether appetite perception and gut hormones differ among chronotypes is unclear. Thus, we examined if early chronotype (EC) have different appetite responses in relation to food intake than LC. Adults with obesity were categorized using the Morningness-Eveningness Questionnaire (MEQ) as either EC (n = 21, 18F, MEQ = 63.9 ± 1.0, 53.7 ± 1.2 yr, 36.2 ± 1.1 kg/m2) and LC (n = 28, 24F, MEQ = 47.2 ± 1.5, 55.7 ± 1.4 yr, 37.1 ± 1.0 kg/m2). Visual analog scales were used during a 120 min 75 g oral glucose tolerance test (OGTT) at 30 min intervals to assess appetite perception, as well as glucose, insulin, GLP-1 (glucagon-like polypeptide-1), GIP (glucose-dependent insulinotrophic peptide), PYY (protein tyrosine tyrosine), and acylated ghrelin. Dietary intake (food logs), resting metabolic rate (RMR; indirect calorimetry), aerobic fitness (maximal oxygen consumption (VO2max)), and body composition dual-energy X-ray absorptiometry (DXA) were also assessed. Age, body composition, RMR, and fasting appetite were similar between groups. However, EC had higher satisfaction and fullness as well as reduced desires for sweet, salty, savory, and fatty foods during the OGTT (P <0.05). Only GIP tAUC0-120 min was elevated in EC versus LC (p = 0.01). Daily dietary intake was similar between groups, but EC ate fewer carbohydrates (p = 0.05) and more protein (p = 0.01) at lunch. Further, EC had lower caloric (p = 0.03), protein (p = 0.03) and fat (p = 0.04) intake during afternoon snacking compared to LC. Dietary fat was lower, and carbohydrates was higher, in EC than LC (p = 0.05) at dinner. Low glucose and high insulin as well as GLP-1 tAUC60-120 min related to desires for sweet foods (p < 0.05). Taken together, EC had more favorable appetite and lower caloric intake later in the day compared with LC.

Effect of Aerobic Exercise and Time-Restricted Feeding on Metabolic Markers and Circadian Rhythm in Mice Fed with the High-Fat Diet

SCOPE

Diet and exercise are significant players in obesity and metabolic diseases. Time-restricted feeding (tRF) has been shown to improve metabolic responses by regulating circadian clocks but whether it acts synergically with exercise remains unknown. It is hypothesized that forced exercise alone or combined with tRF alleviates obesity and its metabolic complications.

METHODS AND RESULTS

Male C57bl6 mice are fed with high-fat or a control diet for 12 weeks either ad libitum or tRF for 10 h during their active period. High-fat diet (HFD)-fed mice are divided into exercise (treadmill for 1 h at 12 m min-1 alternate days for 9 weeks and 16 m min-1 daily for the following 3 weeks) and non-exercise groups. tRF and tRF-Ex significantly decreased body weight, food intake, and plasma lipids, and improved glucose tolerance. However, exercise reduced only body weight and plasma lipids. tRF and tRF-Ex significantly downregulated Fasn, Hmgcr, and Srebp1c, while exercise only Hmgcr. HFD feeding disrupted clock genes, but exercise, tRF, and tRF-Ex coordinated the circadian clock genes Bmal1, Per2, and Rev-Erbα in the liver, adipose tissue, and skeletal muscles.

CONCLUSION

HFD feeding disrupted clock genes in the peripheral organs while exercise, tRF, and their combination restored clock genes and improved metabolic consequences induced by high-fat diet feeding.

The effects of early time restricted eating plus daily caloric restriction compared to daily caloric restriction alone on continuous glucose levels

Background

The median eating duration in the U.S. is 14.75 h, spread throughout the period of wakefulness and ending before sleep. Food intake at an inappropriate circadian time may lead to adverse metabolic outcomes. Emerging literature suggests that time restricted eating (TRE) may improve glucose tolerance and insulin sensitivity. The aim was to compare 24-h glucose profiles and insulin sensitivity in participants after completing 12 weeks of a behavioral weight loss intervention based on early TRE plus daily caloric restriction (E-TRE+DCR) or DCR alone.

Methods

Eighty-one adults with overweight or obesity (age 18-50 years, BMI 25-45 kg/m2) were randomized to either E-TRE+DCR or DCR alone. Each participant wore a continuous glucose monitor (CGM) for 7 days and insulin sensitivity was estimated using the homeostatic model assessment of insulin resistance (HOMA-IR) at Baseline and Week 12. Changes in CGM-derived measures and HOMA-IR from Baseline to Week 12 were assessed within and between groups using random intercept mixed models.

Results

Forty-four participants had valid CGM data at both time points, while 38 had valid glucose, insulin, HOMA-IR, and hemoglobin A1c (A1c) data at both timepoints. There were no significant differences in sex, age, BMI, or the percentage of participants with prediabetes between the groups (28% female, age 39.2 ± 6.9 years, BMI 33.8 ± 5.7 kg/m2, 16% with prediabetes). After adjusting for weight, there were no between-group differences in changes in overall average sensor glucose, standard deviation of glucose levels, the coefficient of variation of glucose levels, daytime or nighttime average sensor glucose, fasting glucose, insulin, HOMA-IR, or A1c. However, mean amplitude of glycemic excursions changed differently over time between the two groups, with a greater reduction found in the DCR as compared to E-TRE+DCR (p = 0.03).

Conclusion

There were no major differences between E-TRE+DCR and DCR groups in continuous glucose profiles or insulin sensitivity 12 weeks after the intervention. Because the study sample included participants with normal baseline mean glucose profiles and insulin sensitivity, the ability to detect changes in these outcomes may have been limited.

Coupling allows robust mammalian redox circadian rhythms despite heterogeneity and noise

Circadian clocks are endogenous oscillators present in almost all cells that drive daily rhythms in physiology and behavior. There are two mechanisms that have been proposed to explain how circadian rhythms are generated in mammalian cells: through a transcription-translation feedback loop (TTFL) and based on oxidation/reduction reactions, both of which are intrinsically stochastic and heterogeneous at the single cell level. In order to explore the emerging properties of stochastic and heterogeneous redox oscillators, we simplify a recently developed kinetic model of redox oscillations to an amplitude-phase oscillator with 'twist' (period-amplitude correlation) and subject to Gaussian noise. We show that noise and heterogeneity alone lead to fast desynchronization, and that coupling between noisy oscillators can establish robust and synchronized rhythms with amplitude expansions and tuning of the period due to twist. Coupling a network of redox oscillators to a simple model of the TTFL also contributes to synchronization, large amplitudes and fine-tuning of the period for appropriate interaction strengths. These results provide insights into how the circadian clock compensates randomness from intracellular sources and highlight the importance of noise, heterogeneity and coupling in the context of circadian oscillators.

Circadian Rhythm Alteration of the Core Clock Genes and the Lipid Metabolism Genes Induced by High-Fat Diet (HFD) in the Liver Tissue of the Chinese Soft-Shelled Turtle (Trionyx sinensis)

Physiology disorders of the liver, as it is an important tissue in lipid metabolism, can cause fatty liver disease. The mechanism might be regulated by 17 circadian clock genes and 18 fat metabolism genes, together with a high-fat diet (HFD). Due to their rich nutritional and medicinal value, Chinese soft-shelled turtles (Trionyx sinensis) are very popular among the Chinese people. In the study, we aimed to investigate the influence of an HFD on the daily expression of both the core clock genes and the lipid metabolism genes in the liver tissue of the turtles. The two diets were formulated with 7.98% lipid (the CON group) and 13.86% lipid (the HFD group) to feed 180 juvenile turtles, which were randomly divided into two groups with three replicates per group and 30 turtles in each replicate for six weeks, and the diet experiment was administrated with a photophase regimen of a 24 h light/dark (12L:12D) cycle. At the end of the experiment, the liver tissue samples were collected from nine turtles per group every 3 h (zeitgeber time: ZT 0, 3, 6, 9, 12, 15, 18, 21 and 24) for 24 h to investigate the daily expression and correlation analysis of these genes. The results showed that 11 core clock genes [i.e., circadian locomotor output cycles kaput (Clock), brain and muscle arnt-like protein 1 and 2 (Bmal1/2), timeless (Tim), cryptochrome 1 (Cry2), period2 (Per2), nuclear factor IL-3 gene (Nfil3), nuclear receptor subfamily 1, treatment D, member 1 and 2 (Nr1d1/2) and retinoic acid related orphan receptor α/β/γ β and γ (Rorβ/γ)] exhibited circadian oscillation, but 6 genes did not, including neuronal PAS domain protein 2 (Npas2), Per1, Cry1, basic helix-loop-helix family, member E40 (Bhlhe40), Rorα and D-binding protein (Dbp), and 16 lipid metabolism genes including fatty acid synthase (Fas), diacylglycerol acyltransferase 1 (Dgat1), 3-hydroxy-3-methylglutaryl-CoA reductase (Hmgcr), Low-density lipoprotein receptor-related protein 1-like (Ldlr1), Lipin 1 (Lipin1), Carnitine palmitoyltransferase 1A (Cpt1a), Peroxisome proliferator activation receptor α, β and γ (Pparα/β/γ), Sirtuin 1 (Sirt1), Apoa (Apoa1), Apolipoprotein B (Apob), Pyruvate Dehydrogenase kinase 4 (Pdk4), Acyl-CoA synthase long-chain1 (Acsl1), Liver X receptors α (Lxrα) and Retinoid X receptor, α (Rxra) also demonstrated circadian oscillations, but 2 genes did not, Scd and Acaca, in the liver tissues of the CON group. However, in the HFD group, the circadian rhythms' expressional patterns were disrupted for the eight core clock genes, Clock, Cry2, Per2, Nfil3, Nr1d1/2 and Rorβ/γ, and the peak expression of Bmal1/2 and Tim showed delayed or advanced phases. Furthermore, four genes (Cry1, Per1, Dbp and Rorα) displayed no diurnal rhythm in the CON group; instead, significant circadian rhythms appeared in the HFD group. Meanwhile, the HFD disrupted the circadian rhythm expressions of seven fat metabolism genes (Fas, Cpt1a, Sirt1, Apoa1, Apob, Pdk4 and Acsl1). Meanwhile, the other nine genes in the HFD group also showed advanced or delayed expression peaks compared to the CON group. Most importantly of all, there were remarkably positive or negative correlations between the core clock genes and the lipid metabolism genes, and their correlation relationships were altered by the HFD. To sum up, circadian rhythm alterations of the core clock genes and the lipid metabolism genes were induced by the high-fat diet (HFD) in the liver tissues of T. sinensis. This result provides experimental and theoretical data for the mass breeding and production of T. sinensis in our country.

Behavior and physiology in female Cricetulus barabensis are associated with the expression of circadian genes

The circadian clock regulates the behavior, physiology, and metabolism of mammals, and these characteristics, such as sleep-wake cycles, exercise capacity, and hormone levels, exhibit circadian rhythms. Light signaling is the main stimulator of the mammalian circadian system. The photoperiod regulates the reproductive cycle of seasonal breeding animals, and the circadian clock plays a pivotal role in this process. However, the role of the clock in coordinating animal behavior and physiology in response to photoperiodic changes needs further investigation. The present study investigated the changes and correlation of behavioral activities, physiological indicators, and gene expression in female striped hamsters (Cricetulus barabensis) within 24 h under a 12L:12D photoperiod. We found that the daily rhythms of sleep-wake and open field were significant in hamsters. The expression of clock genes, melatonin receptor genes, and genes involved in general metabolism oscillated significantly in central and peripheral tissues (brain, hypothalamus, liver, ovary, and thymus) and was significantly associated with behavior and physiology. Our results revealed that the neuroendocrine system regulated the rhythmicity of behavior and physiology, and central and peripheral clock genes (Bmal1, Clock, Per1, Per2, Cry1, and Cry2), melatonin receptor genes (MT1, MT2, and GPR50), and metabolizing genes (SIRT1, FGF21, and PPARα) played important roles. Our results suggest that central and peripheral circadian clocks, melatonin receptors, and genes involved in general metabolism may play key roles in maintaining circadian behavior and metabolic homeostasis in striped hamsters. Our results may have important implication for rodent pest control.

Assessment and Management of Sleep Disturbances in Atopic Dermatitis: A Review

Atopic dermatitis (AD) is a chronic burdensome inflammatory skin disease with well-established cutaneous and systemic comorbidities and disease burden. AD particularly has profound impacts on sleep in individuals of all ages. Sleep disturbances (SDs) affect 6.2% of school-age children and 33-87.1% of adults with AD. This narrative review addresses the burden of SD in AD patients, as well as biological mechanisms of SD in AD, including biological clocks influencing sleep, inflammation, and behavior. Approaches for early detection, diagnosis, objective quantification, patient education, and management are reviewed. It is imperative to break the itch-scratch cycle to reduce SDs and improve quality of life in individuals with AD.

Systematic analysis of circadian disrupting substances with a high-throughput zebrafish circadian behavior screening approach

Circadian rhythm aligns numerous biological functions in majority of animals. Aside from well-known external factors such as the light-dark cycle and temperature, circadian rhythm can also be regulated by rarely explored factors such as synthetic substances. Here, we established a circadian behavior screening approach utilizing zebrafish larvae model, which integrated high-throughput capabilities with automated batch processing. With this approach, we systematically analyzed the circadian disruptive effects of >60 synthetic substances commonly detected in aquatic environment by assessing both the circadian period length and amplitude of circadian behavior, with an exposure concentration set at 100 μg/L. Among tested substances, a series of circadian disrupting compounds (circadian disruptors) were identified. Several categories of the hit compounds can be recognized, such as phthalate (diisopentyl phthalate (DIPP), with 10.1 % and 49.6 % increases for circadian period length and amplitude, respectively), neuroactive substance (mirtazapine, with 10.6 % and 63.1 % increases, respectively), and biocides (thiamethoxam, with 100.3 % increase for amplitude). Among these compounds, DIPP increased circadian period length and amplitude with a high degree. Aside from DIPP, we further examined eleven other phthalates and demonstrated that benzyl butyl phthalate, diisobutyl phthalate and diisohexyl phthalate could also significantly increase the zebrafish circadian period length by 7.9 %, 3.7 % and 8.5 %, respectively. Collectively, the present findings substantiated the feasibility of this high throughput screening strategy for circadian disruptor's discovery and provided novel insights into understanding of the potential risks of synthetic substances.

Astrocytic insulin receptor controls circadian behavior via dopamine signaling in a sexually dimorphic manner

Mammalian circadian clocks respond to feeding and light cues, adjusting internal rhythms with day/night cycles. Astrocytes serve as circadian timekeepers, driving daily physiological rhythms; however, it's unknown how they ensure precise cycle-to-cycle rhythmicity. This is critical for understanding why mistimed or erratic feeding, as in shift work, disrupts circadian physiology- a condition linked to type 2 diabetes and obesity. Here, we show that astrocytic insulin signaling sets the free-running period of locomotor activity in female mice and food entrainment in male mice. Additionally, ablating the insulin receptor in hypothalamic astrocytes alters cyclic energy homeostasis differently in male and female mice. Remarkably, the mutants exhibit altered dopamine metabolism, and the pharmacological modulation of dopaminergic signaling partially restores distinct circadian traits in both male and female mutant mice. Our findings highlight the role of astrocytic insulin-dopaminergic signaling in conveying time-of-feeding or lighting cues to the astrocyte clock, thus governing circadian behavior in a sex-specific manner.

Exercise training modifies skeletal muscle clock gene expression but not 24-hour rhythmicity in substrate metabolism of men with insulin resistance

Twenty-four hour rhythmicity in whole-body substrate metabolism, skeletal muscle clock gene expression and mitochondrial respiration is compromised upon insulin resistance. With exercise training known to ameliorate insulin resistance, our objective was to test if exercise training can reinforce diurnal variation in whole-body and skeletal muscle metabolism in men with insulin resistance. In a single-arm longitudinal design, 10 overweight and obese men with insulin resistance performed 12 weeks of high-intensity interval training recurrently in the afternoon (between 14.00 and 18.00 h) and were tested pre- and post-exercise training, while staying in a metabolic research unit for 2 days under free-living conditions with regular meals. On the second days, indirect calorimetry was performed at 08.00, 13.00, 18.00, 23.00 and 04.00 h, muscle biopsies were taken from the vastus lateralis at 08.30, 13.30 and 23.30 h, and blood was drawn at least bi-hourly over 24 h. Participants did not lose body weight over 12 weeks, but improved body composition and exercise capacity. Exercise training resulted in reduced 24-h plasma glucose levels, but did not modify free fatty acid and triacylglycerol levels. Diurnal variation of muscle clock gene expression was modified by exercise training with period genes showing an interaction (time × exercise) effect and reduced mRNA levels at 13.00 h. Exercise training increased mitochondrial respiration without inducing diurnal variation. Twenty-four-hour substrate metabolism and energy expenditure remained unchanged. Future studies should investigate alternative exercise strategies or types of interventions (e.g. diet or drugs aiming at improving insulin sensitivity) for their capacity to reinforce diurnal variation in substrate metabolism and mitochondrial respiration. KEY POINTS: Insulin resistance is associated with blunted 24-h flexibility in whole-body substrate metabolism and skeletal muscle mitochondrial respiration, and disruptions in the skeletal muscle molecular circadian clock. We hypothesized that exercise training modifies 24-h rhythmicity in whole-body substrate metabolism and diurnal variation in skeletal muscle molecular clock and mitochondrial respiration in men with insulin resistance. We found that metabolic inflexibility over 24 h persisted after exercise training, whereas mitochondrial respiration increased independent of time of day. Gene expression of Per1-3 and Rorα in skeletal muscle changed particularly close to the time of day at which exercise training was performed. These results provide the rationale to further investigate the differential metabolic impact of differently timed exercise to treat metabolic defects of insulin resistance that manifest at a particular time of day.

Design of oscillatory dynamics in numerical simulations of compartment-based enzyme systems

Enzymatic reactions that yield non-neutral products are known to involve feedback due to the bell-shaped pH-rate curve of the enzyme. Compartmentalizing the reaction has been shown to lead to transport-driven oscillations in theory; however, there have been few reproducible experimental examples. Our objective was to determine how the conditions could be optimized to achieve pH oscillations. We employed numerical simulations to investigate the hydrolysis of ethyl acetate in a confined esterase enzyme system, examining the influence of key factors on its behavior. Specific parameter ranges that lead to bistability and self-sustained pH oscillations and the importance of fast base transport for oscillations in this acid-producing system are highlighted. Suggestions are made to expand the parameter space for the occurrence of oscillations, including modifying the maximum of the enzyme pH-rate curve and increasing the negative feedback rate. This research not only sheds light on the programmable nature of enzyme-driven pH regulation but also furthers knowledge on the optimal design of such feedback systems for experimentalists.

TW68, cryptochromes stabilizer, regulates fasting blood glucose levels in diabetic ob/ob and high fat-diet-induced obese mice

Cryptochromes (CRYs), transcriptional repressors of the circadian clock in mammals, inhibit cAMP production when glucagon activates G-protein coupled receptors. Therefore, molecules that modulate CRYs have the potential to regulate gluconeogenesis. In this study, we discovered a new molecule called TW68 that interacts with the primary pockets of mammalian CRY1/2, leading to reduced ubiquitination levels and increased stability. In cell-based circadian rhythm assays using U2OS Bmal1-dLuc cells, TW68 extended the period length of the circadian rhythm. Additionally, TW68 decreased the transcriptional levels of two genes, Phosphoenolpyruvate carboxykinase 1 (PCK1) and Glucose-6-phosphatase (G6PC), which play crucial roles in glucose biosynthesis during glucagon-induced gluconeogenesis in HepG2 cells. Oral administration of TW68 in mice showed good tolerance, a good pharmacokinetic profile, and remarkable bioavailability. Finally, when administered to fasting diabetic animals from ob/ob and HFD-fed obese mice, TW68 reduced blood glucose levels by enhancing CRY stabilization and subsequently decreasing the transcriptional levels of Pck1 and G6pc. These findings collectively demonstrate the antidiabetic efficacy of TW68 in vivo, suggesting its therapeutic potential for controlling fasting glucose levels in the treatment of type 2 diabetes mellitus.

Differentially expressed transcripts study during pregnancy and postpartum anestrus of yak (Bos grunniens)

Background: Yak is the main livestock species in the plateau area, and its reproductive performance is low, usually two years or three years. A very few of yaks recover within a certain period of time after delivery and smoothly enter the next estrous cycle, while most of them enter the postpartum anestrus and show no estrus performance. However, the key biological factors and influencing mechanisms that cause postpartum anestrus in yaks are not clear. Objective: To study the expression of differential transcripts in ovaries of yak during pregnancy and postpartum anestrus. Methods: Each three yaks in pregnancy and anestrus under natural grazing conditions in Haiyan County, Qinghai Province were selected and slaughtered, and their ovaries were collected and sent to Biomarker Technologies. Oxford Nanopore Technologies single-molecule real-time electrical signal sequencing technology was used to perform full-length transcriptome sequencing. Astalavista software was used to identify the types of alternative splicing events in yak estrus and pregnancy, and TAPIS pipeline was used to identify alternative polyadenylation. Results: The results showed that there were 1751 differentially expressed transcripts (DETs) between pregnancy and anestrus in yak, of which 808 were upregulated and 943 were downregulated. GO analysis showed that the biological processes of DETs were mainly reproductive, reproductive and rhythmic processes. KEGG analysis showed that the DET cell junction-related adhesion junction protein (β-catenin) and amino terminal kinase (JNK) were involved in FAs (local adhesion). Phosphatidylinositol-3-kinase (PI3K) is involved in the PI3K/AKT/mTOR signaling pathway. Circadian rhythm output cycle failure (Clock) and brain and muscle tissue aromatic hydrocarbon receptor nuclear transporter-like protein 1 (Bmal1) are involved in circadian rhythm signaling pathway. Conclusion: This study found that β-catenin, JNK, PI3K, Clock and Bmal1 were closely related to postpartum anestrus in yak.

Studying the Human Microbiota: Advances in Understanding the Fundamentals, Origin, and Evolution of Biological Timekeeping

The recently observed circadian oscillations of the intestinal microbiota underscore the profound nature of the human-microbiome relationship and its importance for health. Together with the discovery of circadian clocks in non-photosynthetic gut bacteria and circadian rhythms in anucleated cells, these findings have indicated the possibility that virtually all microorganisms may possess functional biological clocks. However, they have also raised many essential questions concerning the fundamentals of biological timekeeping, its evolution, and its origin. This narrative review provides a comprehensive overview of the recent literature in molecular chronobiology, aiming to bring together the latest evidence on the structure and mechanisms driving microbial biological clocks while pointing to potential applications of this knowledge in medicine. Moreover, it discusses the latest hypotheses regarding the evolution of timing mechanisms and describes the functions of peroxiredoxins in cells and their contribution to the cellular clockwork. The diversity of biological clocks among various human-associated microorganisms and the role of transcriptional and post-translational timekeeping mechanisms are also addressed. Finally, recent evidence on metabolic oscillators and host-microbiome communication is presented.

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.

Stride-to-Stride Fluctuations of Human Gait Are Affected By Chronobiology: An Exploratory Study

Physiological processes present daily oscillations of ≈24 h, called circadian rhythms. Motor performance, for example, reaches its peak in the afternoon, although this can be affected by chronotype. Certain motor activities, for example, walking, can also be affected by circadian rhythms. Healthy walking exhibits stride-to-stride fluctuations with a fractal-like structure that enables adaptability. While pathology and aging are shown to lead to random-like fluctuations; and, therefore, decreased adaptability; the influence of circadian rhythms remains unknown. This study investigates how these fluctuations present in healthy gait are affected by the time of day and chronotype. Eighteen young adults walk for 10 min every 2 h, from 8 a.m. to 6 p.m. Footswitches are used to determine heel-strike and calculate stride time. Then, detrended fluctuation analysis is used to calculate fractal scaling. A mixed-model Analysis of Variance is used and followed by a backward stepwise elimination process. Tukey's tests are used for pairwise comparisons. The statistical model shows the effect of time during the day (12 p.m. exhibits a higher fractal scaling compared to 8 a.m.); and chronotype (evening-types exhibit higher fractal scaling compared to morning-types). This study reveals the influence of chronobiology on stride-to-stride fluctuations. These findings open new perspectives to integrate circadian medicine in biomechanics.

Light phase does not affect operant sucrose self-administration in adult male C57BL/6JAbr mice

Circadian rhythm can have significant impacts on several physiological domains relevant to the expression of behaviour in mice, including body temperature, corticosterone levels, hormones and immune function. Mice are nocturnal; yet many behavioural studies are performed during the light phase, when mice are naturally inactive. Not surprisingly, the time of day when mice are behaviourally tested can significantly impact on domains such as locomotor activity, e.g. dark phase testing results in higher locomotion rates than light phase testing. However, effects on other behavioural domains, such as cognition, are not well-established, with inconsistent reports on improved cognition during dark phase testing compared to light phase testing in mice. Importantly, the impact of circadian rhythm on operant responding, a common task relevant to research into drug abuse and cognitive disorders, has rarely been investigated in mice. Here we evaluated if testing adult male C57BL/6JAbr mice in operant chambers during the light or dark phase affects acquisition of lever responding, lever discrimination under different fixed ratio (FR) schedules (FR1, FR2, FR4), and/or motivation under a progressive ratio schedule for 10% oral sucrose. We found no effect of circadian rhythm on levels of active and inactive lever pressing, or lever discrimination for oral sucrose at any stage of the experiment. These results may be due to high levels of motivation for sucrose under food restriction and low levels of task complexity limiting detection of any effect of light phase on operant behaviour.

Exhaled volatile fatty acids, ruminal methane emission, and their diurnal patterns in lactating dairy cows

To date, the commonly used methods to assess rumen fermentation are invasive. Exhaled breath contains hundreds of volatile organic compounds (VOC) that can reflect animal physiological processes. In the present study, for the first time, we aimed to use a noninvasive metabolomics approach based on high-resolution mass spectrometry to identify rumen fermentation parameters in dairy cows. Enteric methane (CH4) production from 7 lactating cows was measured 8 times over 3 consecutive days using the GreenFeed system (C-Lock Technology Inc.). Simultaneously, exhalome samples were collected in Tedlar gas sampling bags and analyzed offline using a secondary electrospray ionization high-resolution mass spectrometry system. In total, 1,298 features were detected, among them targeted exhaled volatile fatty acids (eVFA; i.e., acetate, propionate, butyrate), which were putatively annotated using their exact mass-to-charge ratio. The intensity of eVFA, in particular acetate, increased immediately after feeding and followed a similar pattern to that observed for ruminal CH4 production. The average total eVFA concentration was 35.5 count per second (CPS), and among the individual eVFA, acetate had the greatest concentration, averaging 21.3 CPS, followed by propionate at 11.5 CPS, and butyrate at 2.67 CPS. Further, exhaled acetate was on average the most abundant of the individual eVFA at around 59.3%, followed by 32.5 and 7.9% of the total eVFA for propionate and butyrate, respectively. This corresponds well with the previously reported proportions of these VFA in the rumen. The diurnal patterns of ruminal CH4 emission and individual eVFA were characterized using a linear mixed model with cosine function fit. The model characterized similar diurnal patterns for eVFA and ruminal CH4 and H2 production. Regarding the diurnal patterns of eVFA, the phase (time of peak) of butyrate occurred first, followed by that of acetate and propionate. Importantly, the phase of total eVFA occurred around 1 h before that of ruminal CH4. This corresponds well with existing data on the relationship between rumen VFA production and CH4 formation. Results from the present study revealed a great potential to assess the rumen fermentation of dairy cows using exhaled metabolites as a noninvasive proxy for rumen VFA. Further validation, with comparisons to rumen fluid, and establishment of the proposed method are required.

Hexosamine biosynthetic pathway and O-GlcNAc cycling of glucose metabolism in brain function and disease

Impaired brain glucose metabolism is considered a hallmark of brain dysfunction and neurodegeneration. Disruption of the hexosamine biosynthetic pathway (HBP) and subsequent O-linked N-acetylglucosamine (O-GlcNAc) cycling has been identified as an emerging link between altered glucose metabolism and defects in the brain. Myriads of cytosolic and nuclear proteins in the nervous system are modified at serine or threonine residues with a single N-acetylglucosamine (O-GlcNAc) molecule by O-GlcNAc transferase (OGT), which can be removed by β-N-acetylglucosaminidase (O-GlcNAcase, OGA). Homeostatic regulation of O-GlcNAc cycling is important for the maintenance of normal brain activity. Although significant evidence linking dysregulated HBP metabolism and aberrant O-GlcNAc cycling to induction or progression of neuronal diseases has been obtained, the issue of whether altered O-GlcNAcylation is causal in brain pathogenesis remains uncertain. Elucidation of the specific functions and regulatory mechanisms of individual O-GlcNAcylated neuronal proteins in both normal and diseased states may facilitate the identification of novel therapeutic targets for various neuronal disorders. The information presented in this review highlights the importance of HBP/O-GlcNAcylation in the neuronal system and summarizes the roles and potential mechanisms of O-GlcNAcylated neuronal proteins in maintaining normal brain function and initiation and progression of neurological diseases.

Metabolic Basis of Circadian Dysfunction in Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. The management of PD is a challenging aspect for general physicians and neurologists. It is characterized by the progressive loss of dopaminergic neurons. Impaired α-synuclein secretion and dopamine release may cause mitochondrial dysfunction and perturb energy metabolism, subsequently altering the activity and survival of dopaminergic neurons, thus perpetuating the neurodegenerative process in PD. While the etiology of PD remains multifactorial, emerging research indicates a crucial role of circadian dysfunction in its pathogenesis. Researchers have revealed that circadian dysfunction and sleep disorders are common among PD subjects and disruption of circadian rhythms can increase the risk of PD. Hence, understanding the findings of circadian biology from translational research in PD is important for reducing the risk of neurodegeneration and for improving the quality of life. In this review, we discuss the intricate relationship between circadian dysfunction in cellular metabolism and PD by summarizing the evidence from animal models and human studies. Understanding the metabolic basis of circadian dysfunction in PD may shed light on novel therapeutic approaches to restore circadian rhythm, preserve dopaminergic function, and ameliorate disease progression. Further investigation into the complex interplay between circadian rhythm and PD pathogenesis is essential for the development of targeted therapies and interventions to alleviate the burden of this debilitating neurodegenerative disorder.

Emergence of Photomodulated Protometabolism by Short Peptide-Based Assemblies

In the early Earth, rudimentary enzymes must have utilized the available light energy source to modulate protometabolic processes. Herein, we report the light-responsive C-C bond manipulation via short peptide-based assemblies bound to the photosensitive molecular cofactor (azo-based photoswitch) where the energy of the light source regulated the binding sites which subsequently modulated the retro-aldolase activity. In the presence of a continual source of high-energy photons, temporal realization of a catalytically more proficient state could be achieved under nonequilibrium conditions. Further, the hydrophobic surface of peptide assemblies facilitated the binding of an orthogonal molecular catalyst that showed augmented activity (promiscuous hydrolytic activity) upon binding. This latent activity was utilized for the in situ generation of light-sensitive cofactor that subsequently modulated the retro-aldolase activity, thus creating a reaction network.

Regulation of feeding and energy homeostasis by clock-mediated Gart in Drosophila

Feeding behavior is essential for growth and survival of animals; however, relatively little is known about its intrinsic mechanisms. Here, we demonstrate that Gart is expressed in the glia, fat body, and gut and positively regulates feeding behavior via cooperation and coordination. Gart in the gut is crucial for maintaining endogenous feeding rhythms and food intake, while Gart in the glia and fat body regulates energy homeostasis between synthesis and metabolism. These roles of Gart further impact Drosophila lifespan. Importantly, Gart expression is directly regulated by the CLOCK/CYCLE heterodimer via canonical E-box, in which the CLOCKs (CLKs) in the glia, fat body, and gut positively regulate Gart of peripheral tissues, while the core CLK in brain negatively controls Gart of peripheral tissues. This study provides insight into the complex and subtle regulatory mechanisms of feeding and lifespan extension in animals.

Molecular clocks, satellite cells, and skeletal muscle regeneration

Skeletal muscle comprises approximately 50% of individual body mass and plays vital roles in locomotion, heat production, and whole body metabolic homeostasis. This tissue exhibits a robust diurnal rhythm that is under control of the suprachiasmatic nucleus (SCN) region of the hypothalamus. The SCN acts as a "central" coordinator of circadian rhythms, while cell-autonomous "peripheral" clocks are located within almost all other tissues/organs in the body. Synchronization of the peripheral clocks in muscles (and other tissues) together with the central clock is crucial to ensure temporally coordinated physiology across all organ systems. By virtue of its mass, human skeletal muscle contains the largest collection of peripheral clocks, but within muscle resides a local stem cell population, satellite cells (SCs), which have their own functional molecular clock, independent of the numerous muscle clocks. Skeletal muscle has a daily turnover rate of 1%-2%, so the regenerative capacity of this tissue is important for whole body homeostasis/repair and depends on successful SC myogenic progression (i.e., proliferation, differentiation, and fusion). Emerging evidence suggests that SC-mediated muscle regeneration may, in part, be regulated by molecular clocks involved in SC-specific diurnal transcription. Here we provide insights on molecular clock regulation of muscle regeneration/repair and provide a novel perspective on the interplay between SC-specific molecular clocks, myogenic programs, and cell cycle kinetics that underpin myogenic progression.

The Risk of Breast Cancer between Western and Mediterranean Dietary Patterns

Breast cancer is a significant public health problem globally and prevention strategies have become of great interest as its incidence rises. Exploring the connection between dietary patterns and the reduction of breast cancer risk is considered a promising approach. High levels of fiber, phytochemicals, a good antioxidant profile, and a composition of advantageous fatty acids are characteristics of healthy dietary programs such as the Mediterranean diet. This review summarized and discussed the active compounds that are considered important in preventing breast cancer, including dietary components from recent related reports. These include polyunsaturated fatty acids, fiber, phytochemicals, and alcohol. Although the exact mechanism for preventing breast cancer using these dietary factors is not well understood, the combination of all the elements in a healthy diet plays a role in reducing breast cancer risk. Considering the elevated probability of breast cancer relapse and mortality, it is crucial to investigate the correlation between a nutritious dietary pattern and breast cancer, while identifying bioactive components that have the potential to mitigate the risk of breast cancer incidence.

Interactions of circadian clock genes with the hallmarks of cancer

The molecular machinery of the circadian clock regulates the expression of many genes and processes in the organism, allowing the adaptation of cellular activities to the daily light-dark cycles. Disruption of the circadian rhythm can lead to various pathologies, including cancer. Thus, disturbance of the normal circadian clock at both genetic and environmental levels has been described as an independent risk factor for cancer. In addition, researchers have proposed that circadian genes may have a tissue-dependent and/or context-dependent role in tumorigenesis and may function both as tumor suppressors and oncogenes. Finally, circadian clock core genes may trigger or at least be involved in different hallmarks of cancer. Hence, expanding the knowledge of the molecular basis of the circadian clock would be helpful to identify new prognostic markers of tumorigenesis and potential therapeutic targets.

Hepatocyte SREBP signaling mediates clock communication within the liver

Rhythmic intraorgan communication coordinates environmental signals and the cell-intrinsic clock to maintain organ homeostasis. Hepatocyte-specific KO of core components of the molecular clock Rev-erbα and -β (Reverb-hDKO) alters cholesterol and lipid metabolism in hepatocytes as well as rhythmic gene expression in nonparenchymal cells (NPCs) of the liver. Here, we report that in fatty liver caused by diet-induced obesity (DIO), hepatocyte SREBP cleavage-activating protein (SCAP) was required for Reverb-hDKO-induced diurnal rhythmic remodeling and epigenomic reprogramming in liver macrophages (LMs). Integrative analyses of isolated hepatocytes and LMs revealed that SCAP-dependent lipidomic changes in REV-ERB-depleted hepatocytes led to the enhancement of LM metabolic rhythms. Hepatocytic loss of REV-ERBα and β (REV-ERBs) also attenuated LM rhythms via SCAP-independent polypeptide secretion. These results shed light on the signaling mechanisms by which hepatocytes regulate diurnal rhythms in NPCs in fatty liver disease caused by DIO.

Co-expression of diurnal and ultradian rhythms in the plasma metabolome of common voles (Microtus arvalis)

Metabolic rhythms include rapid, ultradian (hourly) dynamics, but it remains unclear what their relationship to circadian metabolic rhythms is, and what role meal timing plays in coordinating these ultradian rhythms in metabolism. Here, we characterized widespread ultradian rhythms under ad libitum feeding conditions in the plasma metabolome of the vole, the gold standard animal model for behavioral ultradian rhythms, naturally expressing ~2-h foraging rhythms throughout the day and night. These ultradian metabolite rhythms co-expressed with diurnal 24-h rhythms in the same metabolites and did not align with food intake patterns. Specifically, under light-dark entrained conditions we showed twice daily entrainment of phase and period of ultradian behavioral rhythms associated with phase adjustment of the ultradian cycle around the light-dark and dark-light transitions. These ultradian activity patterns also drove an ultradian feeding pattern. We used a unique approach to map this behavioral activity/feeding status to high temporal resolution (every 90 min) measures of plasma metabolite profiles across the 24-h light-dark cycle. A total of 148 known metabolites were detected in vole plasma. Supervised, discriminant analysis did not group metabolite concentration by feeding status, instead, unsupervised clustering of metabolite time courses revealed clusters of metabolites that exhibited significant ultradian rhythms with periods different from the feeding cycle. Two clusters with dissimilar ultradian dynamics, one lipid-enriched (period = 3.4 h) and one amino acid-enriched (period = 4.1 h), both showed co-expression with diurnal cycles. A third cluster solely comprised of glycerophospholipids (specifically ether-linked phosphatidylcholines) expressed an 11.9 h ultradian rhythm without co-expressed diurnal rhythmicity. Our findings show coordinated co-expression of diurnal metabolic rhythms with rapid dynamics in feeding and metabolism. These findings reveal that ultradian rhythms are integral to biological timing of metabolic regulation, and will be important in interpreting the impact of circadian desynchrony and meal timing on metabolic rhythms.

Artepillin C Time−Dependently Alleviates Metabolic Syndrome in Obese Mice by Regulating CREB/CRTC2−BMAL1 Signaling

Artepillin C (APC), a cAMP-response element−binding (CREB)/CREB regulated transcription coactivator 2 (CRTC2) inhibitor isolated from Brazilian green propolis, can ameliorate metabolic syndrome in obese mice. Because the sensitivity and responsiveness of the body to the drug depend on the time of day and the circadian clock alignment, the optimal administration time of APC for desired efficacy in treating metabolic syndrome remains unclear. In this study, APC (20 mg/kg) or the vehicle was intraperitoneally injected into obese mice once daily for one or three weeks. The results of the insulin tolerance test, pyruvate tolerance test, and histological and biochemical assays showed that APC could improve whole−body glucose homeostasis and decrease hepatic lipid synthesis following a circadian rhythm. Further exploration of the underlying mechanism revealed that APC may disturb the diurnal oscillations of the expression of brain and muscle ARNT−like protein (BMAL1) in primary hepatocytes and the livers of the study subjects. Moreover, APC could inhibit hepatic BMAL1 expression by blocking the CREB/CRTC2 transcription complex. BMAL1 overexpression in primary hepatocytes or the livers of db/db mice antagonized the inhibitory effect of APC on hepatic lipid metabolism. In conclusion, the chronotherapy of APC may relieve metabolic syndrome in obese mice, and the mechanism behind APC−mediated time−of−day effects on metabolic syndrome were unveiled, thereby providing a foundation for optimized APC treatment from a mechanistic perspective.

Turning Back the Clock: A Retrospective Single-Blind Study on Brain Age Change in Response to Nutraceuticals Supplementation vs. Lifestyle Modifications

BACKGROUND

There is a growing consensus that chronological age (CA) is not an accurate indicator of the aging process and that biological age (BA) instead is a better measure of an individual's risk of age-related outcomes and a more accurate predictor of mortality than actual CA. In this context, BA measures the "true" age, which is an integrated result of an individual's level of damage accumulation across all levels of biological organization, along with preserved resources. The BA is plastic and depends upon epigenetics. Brain state is an important factor contributing to health- and lifespan.

METHODS AND OBJECTIVE

Quantitative electroencephalography (qEEG)-derived brain BA (BBA) is a suitable and promising measure of brain aging. In the present study, we aimed to show that BBA can be decelerated or even reversed in humans (N = 89) by using customized programs of nutraceutical compounds or lifestyle changes (mean duration = 13 months).

RESULTS

We observed that BBA was younger than CA in both groups at the end of the intervention. Furthermore, the BBA of the participants in the nutraceuticals group was 2.83 years younger at the endpoint of the intervention compared with their BBA score at the beginning of the intervention, while the BBA of the participants in the lifestyle group was only 0.02 years younger at the end of the intervention. These results were accompanied by improvements in mental-physical health comorbidities in both groups. The pre-intervention BBA score and the sex of the participants were considered confounding factors and analyzed separately.

CONCLUSIONS

Overall, the obtained results support the feasibility of the goal of this study and also provide the first robust evidence that halting and reversal of brain aging are possible in humans within a reasonable (practical) timeframe of approximately one year.

The cold-sensing ion channel TRPM8 regulates central and peripheral clockwork and the circadian oscillations of body temperature

AIM

Physiological functions in mammals show circadian oscillations, synchronized by daily cycles of light and temperature. Central and peripheral clocks participate in this regulation. Since the ion channel TRPM8 is a critical cold sensor, we investigated its role in circadian function.

METHODS

We used TRPM8 reporter mouse lines and TRPM8-deficient mice. mRNA levels were determined by in situ hybridization or RT-qPCR and protein levels by immunofluorescence. A telemetry system was used to measure core body temperature (Tc).

RESULTS

TRPM8 is expressed in the retina, specifically in cholinergic amacrine interneurons and in a subset of melanopsin-positive ganglion cells which project to the central pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus. TRPM8-positive fibres were also found innervating choroid and ciliary body vasculature, with a putative function in intraocular temperature, as shown in TRPM8-deficient mice. Interestingly, Trpm8^-/- animals displayed increased expression of the clock gene Per2 and vasopressin (AVP) in the SCN, suggesting a regulatory role of TRPM8 on the central oscillator. Since SCN AVP neurons control body temperature, we studied Tc in driven and free-running conditions. TRPM8-deficiency increased the amplitude of Tc oscillations and, under dim constant light, induced a greater phase delay and instability of Tc rhythmicity. Finally, TRPM8-positive fibres innervate peripheral organs, like liver and white adipose tissue. Notably, Trpm8^-/- mice displayed a dysregulated expression of Per2 mRNA in these metabolic tissues.

CONCLUSION

Our findings support a function of TRPM8 as a temperature sensor involved in the regulation of central and peripheral clocks and the circadian control of Tc.

Disturbed rhythmicity of intestinal hydrogen peroxide alters gut microbial oscillations in BMAL1-deficient monkeys

Circadian oscillation of gut microbiota exerts significant influence on host physiology, but the host factors that sustain microbial oscillations are rarely reported. We compared the gut microbiome and metabolome of wild-type and BMAL1-deficient cynomolgus monkeys during a diurnal cycle by performing 16S rRNA sequencing and untargeted fecal metabolomics and uncovered the influence of intestinal H₂O₂ on microbial compositions. Ablation of BMAL1 induced expansion of Bacteroidota at midnight and altered microbial oscillations. Some important fecal metabolites changed significantly, and we investigated their correlations with microbes. Further analyses revealed that disturbed rhythmicity of NOX1-derived intestinal H₂O₂ was responsible for the altered microbial oscillations in BMAL1-deficient monkeys. Mechanistic studies showed that BMAL1 transactivated NOX1 via binding to the E1-E2 site in its promoter. Notably, BMAL1-dependent activation of NOX1 was conserved in cynomolgus monkeys and humans. Our study demonstrates the importance of intestine clock-controlled H₂O₂ rhythmicity on the rhythmic oscillation of gut microbiota.

The Circadian Clock, Nutritional Signals and Reproduction: A Close Relationship

The circadian rhythm, which is necessary for reproduction, is controlled by clock genes. In the mouse uterus, the oscillation of the circadian clock gene has been observed. The transcription of the core clock gene period (Per) and cryptochrome (Cry) is activated by the heterodimer of the transcription factor circadian locomotor output cycles kaput (Clock) and brain and muscle Arnt-like protein-1 (Bmal1). By binding to E-box sequences in the promoters of Per1/2 and Cry1/2 genes, the CLOCK-BMAL1 heterodimer promotes the transcription of these genes. Per1/2 and Cry1/2 form a complex with the Clock/Bmal1 heterodimer and inactivate its transcriptional activities. Endometrial BMAL1 expression levels are lower in human recurrent-miscarriage sufferers. Additionally, it was shown that the presence of BMAL1-depleted decidual cells prevents trophoblast invasion, highlighting the importance of the endometrial clock throughout pregnancy. It is widely known that hormone synthesis is disturbed and sterility develops in Bmal1-deficient mice. Recently, we discovered that animals with uterus-specific Bmal1 loss also had poor placental development, and these mice also had intrauterine fetal death. Furthermore, it was shown that time-restricted feeding controlled the uterine clock's circadian rhythm. The uterine clock system may be a possibility for pregnancy complications, according to these results. We summarize the most recent research on the close connection between the circadian clock and reproduction in this review.

Connecting insufficient sleep and insomnia with metabolic dysfunction

The global epidemic of obesity and type 2 diabetes parallels the rampant state of sleep deprivation in our society. Epidemiological studies consistently show an association between insufficient sleep and metabolic dysfunction. Mechanistically, sleep and circadian rhythm exert considerable influences on hormones involved in appetite regulation and energy metabolism. As such, data from experimental sleep deprivation in humans demonstrate that insufficient sleep induces a positive energy balance with resultant weight gain, due to increased energy intake that far exceeds the additional energy expenditure of nocturnal wakefulness, and adversely impacts glucose metabolism. Conversely, animal models have found that sleep loss-induced energy expenditure exceeds caloric intake resulting in net weight loss. However, animal models have significant limitations, which may diminish the clinical relevance of their metabolic findings. Clinically, insomnia disorder and insomnia symptoms are associated with adverse glucose outcomes, though it remains challenging to isolate the effects of insomnia on metabolic outcomes independent of comorbidities and insufficient sleep durations. Furthermore, both pharmacological and behavioral interventions for insomnia may have direct metabolic effects. The goal of this review is to establish an updated framework for the causal links between insufficient sleep and insomnia and risks for type 2 diabetes and obesity.

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.

Chronotype Differences in Body Composition, Dietary Intake and Eating Behavior Outcomes: A Scoping Systematic Review

The timing and nutritional composition of food intake are important zeitgebers for the biological clocks in humans. Thus, eating at an inappropriate time (e.g., during the night) may have a desynchronizing effect on the biological clocks and, in the long term, may result in adverse health outcomes (e.g., weight gain, obesity, and poor metabolic function). Being a very late or early chronotype not only determines preferred sleep and wake times but may also influence subsequent mealtimes, which may affect the circadian timing system. In recent years, an increased number of studies have examined the relation between chronotype and health outcomes, with a main focus on absolute food intake and metabolic markers and, to a lesser extent, on dietary intake distribution and eating behavior. Therefore, this review aimed to systematically determine whether chronotype indirectly affects eating behaviors, dietary intake (timing, choice, nutrients), and biomarkers leading to body composition outcomes in healthy adults. A systematic literature search on electronic databases (PubMed, CINAHL, MEDLINE, SCOPUS, Cochrane library) was performed (International Prospective Register of Systematic Reviews number: CRD42020219754). Only studies that included healthy adults (aged >18 y), classified according to chronotype and body composition profiles, using outcomes of dietary intake, eating behavior, and/or biomarkers, were considered. Of 4404 articles, 24 met the inclusion criteria. The results revealed that late [evening type (ET)] compared with early [morning type (MT)] chronotypes were more likely to be overweight/obese with poorer metabolic health. Both MT and ET had similar energy and macronutrient intakes, consuming food during their preferred sleep-wake timing: later for ET than MT. Most of the energy and macronutrient intakes were distributed toward nighttime for ET and exacerbated by unhealthy eating behaviors and unfavorable dietary intakes. These findings from our systematic review give further insight why higher rates of overweight/obesity and unhealthier metabolic biomarkers are more likely to occur in ET.

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.

Circadian lncRNA ADIRF-AS1 binds PBAF and regulates renal clear cell tumorigenesis

We identify ADIRF-AS1 circadian long non-coding RNA (lncRNA). Deletion of ADIRF-AS1 in U2OS cells alters rhythmicity of clock-controlled genes and expression of extracellular matrix genes. ADIRF-AS1 interacts with all components of the PBAF (PBRM1/BRG1) complex in U2OS cells. Because PBRM1 is a tumor suppressor mutated in over 40% of clear cell renal carcinoma (ccRCC) cases, we evaluate ADIRF-AS1 in ccRCC cells. Reducing ADIRF-AS1 expression in ccRCC cells decreases expression of some PBAF-suppressed genes. Expression of these genes is partially rescued by PBRM1 loss, consistent with ADIRF-AS1 acting in part to modulate PBAF. ADIRF-AS1 expression correlates with survival in human ccRCC, particularly in PBRM1 wild-type, but not mutant, tumors. Loss of ADIRF-AS1 eliminates in vivo tumorigenesis, partially rescued by concurrent loss of PBRM1 only when co-injected with Matrigel, suggesting a PBRM1-independent function of ADIRF-AS1. Our findings suggest that ADIRF-AS1 functions partly through PBAF to regulate specific genes as a BMAL1-CLOCK-regulated, oncogenic lncRNA.

Circadian clock-mediated nuclear receptors in cancer

Circadian system coordinates the daily periodicity of physiological and biochemical functions to adapt to environmental changes. Circadian disruption has been identified to increase the risk of cancer and promote cancer progression, but the underlying mechanism remains unclear. And further mechanistic understanding of the crosstalk between clock components and cancer is urgent to achieve clinical anticancer benefits from chronochemotherapy. Recent studies discover that several nuclear receptors regulating circadian clock, also play crucial roles in mediating multiple cancer processes. In this review, we aim to summarize the latest developments of clock-related nuclear receptors in cancer biology and dissect mechanistic insights into how nuclear receptors coordinate with circadian clock to regulate tumorigenesis and cancer treatment. A better understanding of circadian clock-related nuclear receptors in cancer could help prevent tumorigenesis and improve anticancer efficacy.

Tryptophan metabolism is a physiological integrator regulating circadian rhythms

OBJECTIVE

The circadian clock aligns physiology with the 24-hour rotation of Earth. Light and food are the main environmental cues (zeitgebers) regulating circadian rhythms in mammals. Yet, little is known about the interaction between specific dietary components and light in coordinating circadian homeostasis. Herein, we focused on the role of essential amino acids.

METHODS

Mice were fed diets depleted of specific essential amino acids and their behavioral rhythms were monitored and tryptophan was selected for downstream analyses. The role of tryptophan metabolism in modulating circadian homeostasis was studied using isotope tracing as well as transcriptomic- and metabolomic- analyses.

RESULTS

Dietary tryptophan depletion alters behavioral rhythms in mice. Furthermore, tryptophan metabolism was shown to be regulated in a time- and light- dependent manner. A multi-omics approach and combinatory diet/light interventions demonstrated that tryptophan metabolism modulates temporal regulation of metabolism and transcription programs by buffering photic cues. Specifically, tryptophan metabolites regulate central circadian functions of the suprachiasmatic nucleus and the core clock machinery in the liver.

CONCLUSIONS

Tryptophan metabolism is a modulator of circadian homeostasis by integrating environmental cues. Our findings propose tryptophan metabolism as a potential point for pharmacologic intervention to modulate phenotypes associated with disrupted circadian rhythms.

Circadian Control of Mitochondria in Reactive Oxygen Species Homeostasis

Significance: Mitochondria produce most of the cellular ATP through the process of oxidative phosphorylation. Energy metabolism in the mitochondria is associated with the production of reactive oxygen species (ROS). Excessive ROS production leads to oxidative stress and compromises cellular physiology. Energy metabolism in the mitochondria depends on nutrient flux and cellular metabolic needs, which are in turn connected with the feeding/fasting cycle. In animals, the feeding/fasting cycle is controlled by the circadian clock that generates 24-h rhythms in behavior, metabolism, and signaling. Recent Advances: Here, we discuss the role of the circadian clock and rhythms in mitochondria on ROS homeostasis. The circadian clock is involved in mitochondrial ROS production and detoxification through the control of nutrient flux and oxidation, uncoupling, antioxidant defense, and mitochondrial dynamics. Critical Issues: Little is known on the molecular mechanisms of circadian control of mitochondrial functions. The circadian clock regulates the expression and activity of mitochondrial metabolic and antioxidant enzymes. The regulation involves a direct transcriptional control by Circadian Locomotor Output Cycles Kaput/brain and muscle ARNT-like 1(CLOCK/BMAL1), nuclear factor erythroid-2-related factor 2 (NRF2) transcriptional network, and sirtuin-dependent posttranslational protein modifications. Future Perspectives: We hypothesize that the circadian clock orchestrates mitochondrial physiology to synchronize it with the feeding/fasting cycle. Circadian coordination of mitochondrial function couples energy metabolism with diets and contributes to antioxidant defense to prevent metabolic diseases and delay aging. Antioxid. Redox Signal. 37, 647-663.

Circadian transcriptional pathway atlas highlights a proteasome switch in intermittent fasting

While intermittent fasting is a safe strategy to benefit health, it remains unclear whether a “timer” exists in vivo to record fasting duration and trigger a transcriptional switch. Here, we map a circadian transcriptional pathway atlas from 600 samples across four metabolic tissues of mice under five feeding regimens. Results show that 95.6% of detected canonical pathways are rhythmic in a tissue-specific and feeding-regimen-specific manner, while only less than 25% of them induce changes in transcriptional function. Fasting for 16 h initiates a circadian resonance of 43 pathways in the liver, and the resonance punctually switches following refeeding. The hepatic proteasome coordinates the resonance, and most genes encoding proteasome subunits display a 16-h fasting-dependent transcriptional switch. These findings indicate that the hepatic proteasome may serve as a fasting timer and a coordinator of pathway transcriptional resonance, which provide a target for revealing the underlying mechanism of intermittent fasting.

While intermittent fasting benefits health, the optimal duration of each fasting remains an open question. Wei et al. map an atlas of canonical pathways in intermittent fasting, find that fasting for 16 h initiates circadian resonance of pathways in the liver, and identify the proteasome as a liver-specific fasting “timer”.

The role of MTNR1B polymorphism on circadian rhythm-related cancer: A UK Biobank cohort study

A common G risk allele in the melatonin receptor 1B (MTNR1B, rs10830963) gene has been associated with altered melatonin signaling and secretion. Given that melatonin possesses anticancerogenic properties, we hypothesized that breast and prostate cancer risks vary by rs10830963 genotype. A total of 216 702 participants from the UK Biobank without cancer at baseline (aged 56.4 ± 8.0 years, 50.79% female) were included. Multivariable Cox regression adjusting for known risk factors for breast or prostate cancer was used to estimate the independent effects of the rs10830963 SNP and chronotype on cancer risk. Over a median follow-up of 8 years, 2367 (2.15% of women) incidences of breast cancer and 2866 (2.69% of men) incidences of prostate cancer were documented in females and males, respectively. rs10830963 genotype is not associated with cancer risk independently (female P_trend  = .103, male P_trend  = .281). A late chronotype is associated with breast cancer risk in females (P_trend  = .014), but not prostate cancer risk in males (P_trend  = .915). Further stratification analysis revealed that the rs10830963 genotype is associated with a breast cancer risk in females with moderate evening chronotype (P_trend  = .001) and late chronotype is associated with breast cancer risk in females who carry rs10830963 G risk allele (P_trend  = .015). Our study suggests that having a late chronotype might increase the risk of breast cancer among females, while the effect of MTNR1B rs10830963 genotype on breast cancer risk is mediated by chronotype.

Circadian mechanism disruption is associated with dysregulation of inflammatory and immune responses: a systematic review

The circadian rhythms are regulated by the circadian clock which is under the control of suprachiasmatic nucleus of hypothalamus. The central and peripheral clocks on different tissue together synchronize to form circadian system. Factors disrupt the circadian rhythm, such as irregular eating patterns, sleep/wake time, night shift work and temperature. Due to the misalignment of central clock components, it has been recognized as the pathophysiology of lifestyle-related diseases mediated by the inflammation such as diabetes, obesity, neurological disorder and hormonal imbalance. Also we discuss the therapeutic effect of time-restricted feeding over diabetes and obesity caused by miscommunication between central and peripheral clock. The genetic and epigenetic changes involve due to the deregulation of circadian system. The aim of the present review is to discuss the circadian mechanisms that are involved in the complex interaction between host and external factors and its disruption is associated with deregulation of inflammatory and immune responses. Hence, we need to understand the mechanism of functioning of our biological clocks so that it helps us treat health-related problems such as jet lags, sleep disorders due to night-time shift work, obesity and mental disturbances. We hope minimal cost behavioural and lifestyle changes can improve circadian rhythms and presumably provide a better health.