The circadian clock and metabolic homeostasis: entangled networks

Brain-muscle communication prevents muscle aging by maintaining daily physiology

A molecular clock network is crucial for daily physiology and maintaining organismal health. We examined the interactions and importance of intratissue clock networks in muscle tissue maintenance. In arrhythmic mice showing premature aging, we created a basic clock module involving a central and a peripheral (muscle) clock. Reconstituting the brain-muscle clock network is sufficient to preserve fundamental daily homeostatic functions and prevent premature muscle aging. However, achieving whole muscle physiology requires contributions from other peripheral clocks. Mechanistically, the muscle peripheral clock acts as a gatekeeper, selectively suppressing detrimental signals from the central clock while integrating important muscle homeostatic functions. Our research reveals the interplay between the central and peripheral clocks in daily muscle function and underscores the impact of eating patterns on these interactions.

The epidermal circadian clock integrates and subverts brain signals to guarantee skin homeostasis

In mammals, the circadian clock network drives daily rhythms of tissue-specific homeostasis. To dissect daily inter-tissue communication, we constructed a mouse minimal clock network comprising only two nodes: the peripheral epidermal clock and the central brain clock. By transcriptomic and functional characterization of this isolated connection, we identified a gatekeeping function of the peripheral tissue clock with respect to systemic inputs. The epidermal clock concurrently integrates and subverts brain signals to ensure timely execution of epidermal daily physiology. Timely cell-cycle termination in the epidermal stem cell compartment depends upon incorporation of clock-driven signals originating from the brain. In contrast, the epidermal clock corrects or outcompetes potentially disruptive feeding-related signals to ensure the optimal timing of DNA replication. Together, we present an approach for cataloging the systemic dependencies of daily temporal organization in a tissue and identify an essential gate-keeping function of peripheral circadian clocks that guarantees tissue homeostasis.

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

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

Chronopharmacology of diuresis via metabolic profiling and key biomarker discovery of the traditional Chinese prescription Ji-Ming-San using tandem mass spectrometry in rat models

BACKGROUND

Ji-Ming-Shan (JMS) is a traditional prescription used for patients with rheumatism, tendons swelling, relief of foot pain, athlete's foot, diuresis, gout. Although many studies have investigated the active compounds in each herb, the functional mechanism behind its therapeutic effect remains unclear.

STUDY DESIGN

Metabolic cages for sample collection. The serum components obtained from the experimental animals were analyzed using LC-MS/MS. Furthermore, cross-analysis using the software MetaboAnalyst and Venn diagrams were used to investigate chronopharmacology of JMS in the animal models.

PURPOSE

The aim of this study is to analyze the diuretic effects of JMS and to explore their chronopharmacology involved in organ regulation through four-quarter periods from serum samples of rat models.

METHODS

Metabolic cages were used for collecting the urine samples and PocketChem UA PU-4010, Fuji DRI-CHEM 800 were used to examine the urine biochemical parameters. The serum components were identified through ultra-performance liquid chromatography-quadrupole time-of-flight (UPLC-Q-TOF) with a new developed method. Cross analysis, Venn diagram, MetaboAnalyst were used to investigate the key biomarker and major metabolism route with the oral administration of the drug.

RESULT

JMS significantly changed the 6 h urine volume with no observed kidney toxicity. Urine pH value ranges from 7.0 to 7.5. The chronopharmacology of JMS diuresis activity were 0-6 and 6-12 groups. UPLC-Q-TOF analyses identified 243 metabolites which were determined in positive mode and negative mode respectively. With cross analysis in the Venn diagram, one key biomarker naringenin-7-O-glucoside has been identified. Major metabolic pathways such as 1: Glycerophospholipid metabolism, 2: Primary bile acid biosynthesis, 3: Sphingolipid metabolism, 4: Riboflavin metabolism, 5: Linoleic acid metabolism, 6: Butanoate metabolism.

CONCLUSION

JMS significantly changed the urine output of animals in the 0-6 and 6-12 groups. No change in urine pH was observed and also kidney toxicity. A new UPLC-Q-TOF method was developed for the detection of the metabolites of JMS after oral administration. The cross analysis with Venn diagram and identified the key biomarker of JMS namely naringenin-7-O-glucoside. The results showed that six major pathways are involved in the gastrointestinal system and the liver. This study demonstrated the capability of JMS prescription in the regulation of diuresis and identified a key biomarker that is responsible for its therapeutic effect.

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.

Peripheral clock gene oscillations are perturbed in neonatal and adult rat offspring raised under adverse limited bedding conditions

Circadian (24-h) rhythms in the suprachiasmatic nucleus (SCN) are established in utero in rodents, but rhythmicity of peripheral circadian clocks appears later in postnatal development. Since peripheral oscillators can be influenced by maternal feeding and behavior, we investigated whether exposure to the adverse environmental conditions of limited bedding (LB) during postnatal life would alter rhythmicity in the SCN, adrenal gland and liver in neonatal (postnatal day PND10), juvenile (PND28) and adult rats. We also examined locomotor activity in adults. Limited bedding increased nursing time and slightly increased fragmentation of maternal behavior. Exposure to LB reduced the amplitude of Per2 in the SCN on PND10. Adrenal clock gene expression (Bmal1, Per2, Cry1, Rev-erbα, Dbp) and corticosterone secretion were rhythmic at all ages in NB offspring, whereas rhythmicity of Bmal1, Cry1 and corticosterone was abolished in neonatal LB pups. Circadian gene expression in the adrenal and liver was well established by PND28. In adults, liver expression of several circadian genes was increased at specific daytimes by LB and the microstructure of locomotor behavior was altered. Thus, changes in maternal care and behavior might provide important signals to the maturing peripheral oscillators and modify, in particular their output functions in the long-term.

Hyperphagia, Growth, and Puberty in Children with Angelman Syndrome

Angelman Syndrome (AS) is a rare genetic disorder caused by lack of maternal UBE3A protein due to a deletion of the chromosome 15q11.2-q13 region, uniparental paternal disomy, imprinting center defect, or pathogenic variant in the UBE3A gene. Characteristics are developmental delay, epilepsy, behavioral, and sleep problems. There is some evidence for hyperphagia, shorter stature, and higher BMI compared to neurotypical children, but longitudinal studies on growth are lacking. In this study, we analyzed prospectively collected data of 145 children with AS, who visited the ENCORE Expertise Center between 2010 and 2021, with a total of 853 visits. Children showed an elevated mean score of 25 on the Dykens Hyperphagia questionnaire (range 11-55) without genotype association. Higher scores were significantly associated with higher body mass index (BMI) standard deviation scores (SDS) (p = 0.004). Mean height was -1.2 SDS (SD 1.3), mean BMI-SDS was 0.6 (SD 1.7); 43% had a BMI-SDS > 1 and 20% had a BMI-SDS > 2. Higher BMI-SDS was significantly associated with non-deletion genotype (p = 0.037) and walking independently (p = 0.023). Height SDS decreased significantly with age (p < 0.001) and BMI-SDS increased significantly with age (p < 0.001. Onset of puberty was normal. In conclusion, children with AS showed moderate hyperphagia, lower height SDS, and higher BMI-SDS compared to norm data, with increasing deviation from the norm with age. It is uncertain how loss of maternal UBE3A function may influence growth. Attention to diet, exercise, and hyperphagia from an early age is recommended to prevent obesity and associated health problems.

Nonalcoholic Steatohepatitis Disrupts Diurnal Liver Transcriptome Rhythms in Mice

BACKGROUND & AIMS

The liver ensures organismal homeostasis through modulation of physiological functions over the course of the day. How liver diseases such as nonalcoholic steatohepatitis (NASH) affect daily transcriptome rhythms in the liver remains elusive.

METHODS

To start closing this gap, we evaluated the impact of NASH on the diurnal regulation of the liver transcriptome in mice. In addition, we investigated how stringent consideration of circadian rhythmicity affects the outcomes of NASH transcriptome analyses.

RESULTS

Comparative rhythm analysis of the liver transcriptome from diet-induced NASH and control mice showed an almost 3-hour phase advance in global gene expression rhythms. Rhythmically expressed genes associated with DNA repair and cell-cycle regulation showed increased overall expression and circadian amplitude. In contrast, lipid and glucose metabolism-associated genes showed loss of circadian amplitude, reduced overall expression, and phase advances in NASH livers. Comparison of NASH-induced liver transcriptome responses between published studies showed little overlap (12%) in differentially expressed genes (DEGs). However, by controlling for sampling time and using circadian analytical tools, a 7-fold increase in DEG detection was achieved compared with methods without time control.

CONCLUSIONS

NASH had a strong effect on circadian liver transcriptome rhythms with phase- and amplitude-specific effects for key metabolic and cell repair pathways, respectively. Accounting for circadian rhythms in NASH transcriptome studies markedly improves DEG detection and enhances reproducibility.

When should I run-the role of exercise timing in metabolic health

The prevalence of type 2 diabetes is reaching epidemic proportions. First line therapy approaches are lifestyle interventions including exercise. Although a vast amount of studies reports on beneficial effects of exercise on metabolism in humans per se, overall data are contradictory which makes it difficult to optimize interventions. Innovative exercise strategies and its underlying mechanism are needed to elucidate in order to close this therapeutic gap. The skeletal muscle produces and secretes myokines and microRNAs in response to exercise and both are discussed as mechanisms linking exercise and metabolic adaptation. Aspects of chronophysiology such as diurnal variation in insulin sensitivity or exercise as a signal to reset dysregulated peripheral clocks are of growing interest in the context of impaired metabolism. Deep insight of how exercise timing determines metabolic adaptations is required to optimize exercise interventions. This review aims to summarize the current state of research on the interaction between timing of exercise and metabolism in humans, providing insights into proposed mechanistic concepts focusing on myokines and microRNAs. First evidence points to an impact of timing of exercise on health outcome, although data are inconclusive. Underlying mechanisms remain elusive. It is currently unknown if the timed release of mykokines depends on time of day when exercise is performed. microRNAs have been found as an important mediator of processes associated with exercise adaptation. Further research is needed to evaluate their full relevance. In conclusion, it seems to be too early to provide concrete recommendations on timing of exercise to maximize beneficial effects.

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

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

Oleic acid regulates the circadian rhythm of adipose tissue in obesity

The effect of oleic acid (OA) on the regulation of the circadian rhythm present in human visceral (VAT) and subcutaneous (SAT) adipose tissue from patients with morbid obesity has not been analyzed yet. VAT and SAT explants from patients with morbid obesity were incubated with OA to analyze the circadian regulation of clock and other genes related to lipid metabolism (SREBP-1c, FAS, LPL and CPT1), and their association with baseline variables and the improvement of these patients after bariatric surgery. There were significant differences in amplitude and acrophase in VAT with respect to SAT. In VAT, body weight negatively correlated with BMAL1 and CRY1 amplitude, and REVERBα acrophase; body mass index (BMI) negatively correlated with REVERBα acrophase; and waist circumference negatively correlated with PER3 acrophase. In SAT, BMI negatively correlated with CLOCK amplitude, and CLOCK, REVERBα and CRY2 MESOR; and waist circumference negatively correlated with PER3 amplitude and acrophase. A greater short-term improvement of body weight, BMI and waist circumference in patients with morbid obesity after bariatric surgery was associated with a lower CRY1 and CRY2 amplitude and an earlier PER1 and PER3 acrophase in SAT. OA produced a more relevant circadian rhythm and increased the amplitude of most clock genes and lipid metabolism-related genes. OA regulated the acrophase of most clock genes in VAT and SAT, placing CLOCK/BMAL1 in antiphase with regard to the other genes. OA increased the circadian rhythmicity, although with slight differences between adipose tissues. These differences could determine its different behavior in obesity.

Step in Time: Conservation of Circadian Clock Genes in Animal Evolution

Over the past few decades, the molecular mechanisms responsible for circadian phenotypes of animals have been studied in increasing detail in mammals, some insects, and other invertebrates. Particular circadian proteins and their interactions are shared across evolutionary distant animals, resulting in a hypothesis for the canonical circadian clock of animals. As the number of species for which the circadian clockwork has been described increases, the circadian clock in animals driving cyclical phenotypes becomes less similar. Our focus in this review is to develop and synthesize the current literature to better understand the antiquity and evolution of the animal circadian clockwork. Here, we provide an updated understanding of circadian clock evolution in animals, largely through the lens of conserved genes characterized in the circadian clock identified in bilaterian species. These comparisons reveal extensive variation within the likely composition of the core clock mechanism, including losses of many genes, and that the ancestral clock of animals does not equate to the bilaterian clock. Despite the loss of these core genes, these species retain circadian behaviors and physiology, suggesting novel clocks have evolved repeatedly. Additionally, we highlight highly conserved cellular processes (e.g., cell division, nutrition) that intersect with the circadian clock of some animals. The conservation of these processes throughout the animal tree remains essentially unknown, but understanding their role in the evolution and maintenance of the circadian clock will provide important areas for future study.

The Effect of Diet on the Cardiac Circadian Clock in Mice: A Systematic Review

Circadian rhythms play important roles in regulating physiological and behavioral processes. These are adjusted by environmental cues, such as diet, which acts by synchronizing or attenuating the circadian rhythms of peripheral clocks, such as the liver, intestine, pancreas, white and brown adipose tissue, lungs, kidneys, as well as the heart. Some studies point to the influence of diet composition, feeding timing, and dietary restriction on metabolic homeostasis and circadian rhythms at various levels. Therefore, this systematic review aimed to discuss studies addressing the effect of diet on the heart clock in animal models and, additionally, the chronodisruption of the clock and its relation to the development of cardiovascular disorders in the last 15 years. A search was conducted in the PubMed, Scopus, and Embase databases. The PRISMA guide was used to construct the article. Nineteen studies met all inclusion and exclusion criteria. In summary, these studies have linked the circadian clock to cardiovascular health and suggested that maintaining a robust circadian system may reduce the risks of cardiometabolic and cardiovascular diseases. The effect of time-of-day-dependent eating on the modulation of circadian rhythms of the cardiac clock and energy homeostasis is notable, among its deleterious effects predominantly in the sleep (light) phase and/or at the end of the active phase.

Circadian clock—A promising scientific target in oral science

The oral and maxillofacial organs play vital roles in chewing, maintaining facial beauty, and speaking. Almost all physiological processes display circadian rhythms that are driven by the circadian clock, allowing organisms to adapt to the changing environment. In recent years, increasing evidence has shown that the circadian clock system participates in oral and maxillofacial physiological and pathological processes, such as jaw and tooth development, salivary gland function, craniofacial malformations, oral carcinoma and other diseases. However, the roles of the circadian clock in oral science have not yet been comprehensively reviewed. Therefore, This paper provides a systematic and integrated perspective on the function of the circadian clock in the fields of oral science, reviews recent advances in terms of the circadian clock in oral and maxillofacial development and disease, dialectically analyzes the importance of the circadian clock system and circadian rhythm to the activities of oral and maxillofacial tissues, and focuses on analyzing the mechanism of the circadian clock in the maintenance of oral health, affecting the common diseases of the oral and maxillofacial region and the process of oral-related systemic diseases, sums up the chronotherapy and preventive measures for oral-related diseases based on changes in tissue activity circadian rhythms, meanwhile, comes up with a new viewpoint to promote oral health and human health.

Adiponectin regulates the circadian rhythm of glucose and lipid metabolism

Adiponectin is a cytokine secreted from adipocytes and regulates metabolism. Although serum adiponectin levels show diurnal variations, it is not clear if the effects of adiponectin are time-dependent. Therefore, this study conducted locomotor activity analyses and various metabolic studies using the adiponectin knockout (APN (-/-)) and the APN (+/+) mice to understand whether adiponectin regulates the circadian rhythm of glucose and lipid metabolism. We observed that the adiponectin gene deficiency does not affect the rhythmicity of core circadian clock genes expression in several peripheral tissues. In contrast, the adiponectin gene deficiency alters the circadian rhythms of liver and serum lipid levels and results in the loss of the time dependency of very-low-density lipoprotein-triglyceride secretion from the liver. In addition, the whole-body glucose tolerance of the APN (-/-) mice was normal at CT10 but reduced at CT22, compared to the APN (+/+) mice. The decreased glucose tolerance at CT22 was associated with insulin hyposecretion in vivo. In contrast, the gluconeogenesis activity was higher in the APN (-/-) mice than in the APN (+/+) mice throughout the day. These results indicate that adiponectin regulates part of the circadian rhythm of metabolism in the liver.

Rewiring of liver diurnal transcriptome rhythms by triiodothyronine (T3) supplementation

Diurnal (i.e., 24 hr) physiological rhythms depend on transcriptional programs controlled by a set of circadian clock genes/proteins. Systemic factors like humoral and neuronal signals, oscillations in body temperature, and food intake align physiological circadian rhythms with external time. Thyroid hormones (THs) are major regulators of circadian clock target processes such as energy metabolism, but little is known about how fluctuations in TH levels affect the circadian coordination of tissue physiology. In this study, a high triiodothyronine (T₃) state was induced in mice by supplementing T₃ in the drinking water, which affected body temperature, and oxygen consumption in a time-of-day-dependent manner. A 24-hr transcriptome profiling of liver tissue identified 37 robustly and time independently T₃-associated transcripts as potential TH state markers in the liver. Such genes participated in xenobiotic transport, lipid and xenobiotic metabolism. We also identified 10–15% of the liver transcriptome as rhythmic in control and T₃ groups, but only 4% of the liver transcriptome (1033 genes) were rhythmic across both conditions – amongst these, several core clock genes. In-depth rhythm analyses showed that most changes in transcript rhythms were related to mesor (50%), followed by amplitude (10%), and phase (10%). Gene set enrichment analysis revealed TH state-dependent reorganization of metabolic processes such as lipid and glucose metabolism. At high T₃ levels, we observed weakening or loss of rhythmicity for transcripts associated with glucose and fatty acid metabolism, suggesting increased hepatic energy turnover. In summary, we provide evidence that tonic changes in T₃ levels restructure the diurnal liver metabolic transcriptome independent of local molecular circadian clocks.

Many environmental conditions, including light and temperature, vary with a daily rhythm that affects how animals interact with their surroundings. Indeed, most species have developed so-called circadian clocks: internal molecular timers that cycle approximately every 24 hours and regulate many bodily functions, including digestion, energy metabolism and sleep.

The energy metabolism of the liver – the chemical reactions that occur in the organ to produce energy from nutrients – is controlled both by the circadian clock system, and by the hormones produced by a gland in the neck called the thyroid. However, the interaction between these two regulators is poorly understood. To address this question, de Assis, Harder et al. elevated the levels of thyroid hormones in mice by adding these hormones to their drinking water.

Studying these mice showed that, although thyroid hormone levels were good indicators of how much energy mice burn in a day, they do not reflect daily fluctuations in metabolic rate faithfully. Additionally, de Assis, Harder et al. showed that elevating T₃, the active form of thyroid hormone, led to a rewiring of the daily rhythms at which genes were turned on and off in the liver, affecting the daily timing of processes including fat and cholesterol metabolism. This occurred without changing the circadian clock of the liver directly.

De Assis, Harder et al.’s results indicate that time-of-day critically affects the action of thyroid hormones in the liver. This suggests that patients with hypothyroidism, who produce low levels of thyroid hormones, may benefit from considering time-of-day as a factor in disease diagnosis, therapy and, potentially, prevention. Further data on the rhythmic regulation of thyroid action in humans, including in patients with hypothyroidism, are needed to further develop this approach.

Characterization of Affective Behaviors and Motor Functions in Mice With a Striatal-Specific Deletion of Bmal1 and Per2

The expression of circadian clock genes, either centrally or in the periphery, has been shown to play an integral role in the control of behavior. Brain region-specific downregulation of clock genes revealed behavioral phenotypes associated with neuropsychiatric disorders and neurodegenerative disease. The specific function of the clock genes as well as the underlying mechanisms that contribute to the observed phenotypes, however, are not yet fully understood. We assessed anxiety- and depressive-like behavior and motor functions in male and female mice with a conditional ablation of Bmal1 or Per2 from medium spiny neurons (MSNs) of the striatum as well as mice lacking one copy of Gpr88. Whereas the conditional knockout of Bmal1 and Per2 had mild effects on affective behaviors, a pronounced effect on motor functions was found in Bmal1 knockout mice. Subsequent investigation revealed an attenuated response of Bmal1 knockout mice to dopamine receptor type 1 agonist treatment, independently of the expression of targets of the dopamine signaling pathway or mitochondrial respiration in MSNs. The study thus suggests a potential interaction of Bmal1 within the direct dopamine signaling pathway, which may provide the link to a shared, MSN-dependent mechanism regulating affective behavior and motor function in mice.

Lack of TRPV1 Channel Modulates Mouse Gene Expression and Liver Proteome with Glucose Metabolism Changes

To investigate the role of the transient receptor potential channel vanilloid type 1 (TRPV1) in hepatic glucose metabolism, we analyzed genes related to the clock system and glucose/lipid metabolism and performed glycogen measurements at ZT8 and ZT20 in the liver of C57Bl/6J (WT) and Trpv1 KO mice. To identify molecular clues associated with metabolic changes, we performed proteomics analysis at ZT8. Liver from Trpv1 KO mice exhibited reduced Per1 expression and increased Pparα, Pparγ, Glut2, G6pc1 (G6pase), Pck1 (Pepck), Akt, and Gsk3b expression at ZT8. Liver from Trpv1 KO mice also showed reduced glycogen storage at ZT8 but not at ZT20 and significant proteomics changes consistent with enhanced glycogenolysis, as well as increased gluconeogenesis and inflammatory features. The network propagation approach evidenced that the TRPV1 channel is an intrinsic component of the glucagon signaling pathway, and its loss seems to be associated with increased gluconeogenesis through PKA signaling. In this sense, the differentially identified kinases and phosphatases in WT and Trpv1 KO liver proteomes show that the PP2A phosphatase complex and PKA may be major players in glycogenolysis in Trpv1 KO mice.

Proanthocyanidins Restore the Metabolic Diurnal Rhythm of Subcutaneous White Adipose Tissue According to Time-Of-Day Consumption

Consumption of grape seed proanthocyanidin extract (GSPE) has beneficial effects on the functionality of white adipose tissue (WAT). However, although WAT metabolism shows a clear diurnal rhythm, whether GSPE consumption could affect WAT rhythmicity in a time-dependent manner has not been studied. Ninety-six male Fischer rats were fed standard (STD, two groups) or cafeteria (CAF, four groups) diet for 9 weeks (n = 16 each group). From week 6 on, CAF diet animals were supplemented with vehicle or 25 mg GSPE/kg of body weight either at the beginning of the light/rest phase (ZT0) or at the beginning of the dark/active phase (ZT12). The two STD groups were also supplemented with vehicle at ZT0 or ZT12. In week 9, animals were sacrificed at 6 h intervals (n = 4) to analyze the diurnal rhythms of subcutaneous WAT metabolites by nuclear magnetic resonance spectrometry. A total of 45 metabolites were detected, 19 of which presented diurnal rhythms in the STD groups. Although most metabolites became arrhythmic under CAF diet, GSPE consumption at ZT12, but not at ZT0, restored the rhythmicity of 12 metabolites including compounds involved in alanine, aspartate, and glutamate metabolism. These results demonstrate that timed GSPE supplementation may restore, at least partially, the functional dynamics of WAT when it is consumed at the beginning of the active phase. This study opens an innovative strategy for time-dependent polyphenol treatment in obesity and metabolic diseases.

Melanopsin (Opn4) is an oncogene in cutaneous melanoma

The search for new therapeutical targets for cutaneous melanoma and other cancers is an ongoing task. We expanded this knowledge by evaluating whether opsins, light- and thermo-sensing proteins, could display tumor-modulatory effects on melanoma cancer. Using different experimental approaches, we show that melanoma cell proliferation is slower in the absence of Opn4, compared to Opn4WT due to an impaired cell cycle progression and reduced melanocyte inducing transcription factor (Mitf) expression. In vivo tumor progression of Opn4KO cells is remarkably reduced due to slower proliferation, and higher immune system response in Opn4KO tumors. Using pharmacological assays, we demonstrate that guanylyl cyclase activity is impaired in Opn4KO cells. Evaluation of Tumor Cancer Genome Atlas (TCGA) database confirms our experimental data as reduced MITF and OPN4 expression in human melanoma correlates with slower cell cycle progression and presence of immune cells in the tumor microenvironment (TME). Proteomic analyses of tumor bulk show that the reduced growth of Opn4KO tumors is associated with reduced Mitf signaling, higher translation of G2/M proteins, and impaired guanylyl cyclase activity. Conversely, in Opn4WT tumors increased small GTPase and an immune-suppressive TME are found. Such evidence points to OPN4 as an oncogene in melanoma, which could be pharmacologically targeted.

Using Microbiome-Based Approaches to Deprogram Chronic Disorders and Extend the Healthspan following Adverse Childhood Experiences

Adverse childhood experiences (ACEs), which can include child trafficking, are known to program children for disrupted biological cycles, premature aging, microbiome dysbiosis, immune-inflammatory misregulation, and chronic disease multimorbidity. To date, the microbiome has not been a major focus of deprogramming efforts despite its emerging role in every aspect of ACE-related dysbiosis and dysfunction. This article examines: (1) the utility of incorporating microorganism-based, anti-aging approaches to combat ACE-programmed chronic diseases (also known as noncommunicable diseases and conditions, NCDs) and (2) microbiome regulation of core systems biology cycles that affect NCD comorbid risk. In this review, microbiota influence over three key cyclic rhythms (circadian cycles, the sleep cycle, and the lifespan/longevity cycle) as well as tissue inflammation and oxidative stress are discussed as an opportunity to deprogram ACE-driven chronic disorders. Microbiota, particularly those in the gut, have been shown to affect host–microbe interactions regulating the circadian clock, sleep quality, as well as immune function/senescence, and regulation of tissue inflammation. The microimmunosome is one of several systems biology targets of gut microbiota regulation. Furthermore, correcting misregulated inflammation and increased oxidative stress is key to protecting telomere length and lifespan/longevity and extending what has become known as the healthspan. This review article concludes that to reverse the tragedy of ACE-programmed NCDs and premature aging, managing the human holobiont microbiome should become a routine part of healthcare and preventative medicine across the life course.

Dysregulation of PER3 clock gene and its only pseudogene in colorectal cancer and type 2 diabetes

The period (PER) family genes (PER1, PER2, and PER3) play a fundamental role in regulating the day/night cycle. PER3 has a pseudogene variant, PER3P1 or PER4, whose role and expression pattern is unclear in human health and diseases. This study was performed to evaluate the expression levels of normal PER family members and the PER3P1 pseudogene in colorectal cancer (CRC) and type 2 diabetes (T2D). Blood samples were taken from 50 diabetic patients and analyzed using real-time PCR for quantification of PER3 and PER3P1 expression. Colorectal tumor tissues of 50 individuals were also used to evaluate the expression of PER members. All PER members, including PER3P1, were found to be downregulated in colorectal tumor samples. Blood samples collected from diabetic subjects revealed an opposite expression pattern; both PER3 and its pseudogene were found to be upregulated when compared to the control group. Our results reveal coordination between the expression pattern of PER3P1 and normal PER family genes. Based on our findings and the pathological importance of this pseudogene, it can be suggested that PER3P1 may be one of the key regulators of the molecular clock network and PER family expression. This hypothesis needs to be confirmed by further studies.

Therapeutic potential of exosomes/miRNAs in polycystic ovary syndrome induced by the alteration of circadian rhythms

Polycystic ovary syndrome (PCOS) is a reproductive dysfunction associated with endocrine disorders and is most common in women of reproductive age. Clinical and/or biochemical manifestations include hyperandrogenism, persistent anovulation, polycystic ovary, insulin resistance, and obesity. Presently, the aetiology and pathogenesis of PCOS remain unclear. In recent years, the role of circadian rhythm changes in PCOS has garnered considerable attention. Changes in circadian rhythm can trigger PCOS through mechanisms such as oxidative stress and inflammation; however, the specific mechanisms are unclear. Exosomes are vesicles with sizes ranging from 30-120nm that mediate intercellular communication by transporting microRNAs (miRNAs), proteins, mRNAs, DNA, or lipids to target cells and are widely involved in the regulation of various physiological and pathological processes. Circadian rhythm can alter circulating exosomes, leading to a series of related changes and physiological dysfunctions. Therefore, we speculate that circadian rhythm-induced changes in circulating exosomes may be involved in PCOS pathogenesis. In this review, we summarize the possible roles of exosomes and their derived microRNAs in the occurrence and development of PCOS and discuss their possible mechanisms, providing insights into the potential role of exosomes for PCOS treatment.

A scoping review of the diurnal variation in the intensity of neuropathic pain

BACKGROUND

Recent studies suggest that neuropathic pain exhibit a daily diurnal pattern with peak levels usually in the late afternoon to evening and trough in the morning hours, although literature on this topic has been sparse. This scoping review examines current evidence on the chronobiology of neuropathic pain in both animal models and in humans with neuropathic pain.

METHOD

Literature search was conducted on major medical databases for relevant articles on chronobiology of neuropathic pain in both animal models and in humans with neuropathic pain. Data extracted include details of specific animal models or specific neuropathic pain conditions in humans, methods and timing of assessing pain severity, and specific findings of diurnal variation in pain intensity or its surrogate markers.

RESULTS

Thirteen animal and eight human studies published between 1976 to 2020 were included in the analysis. Seven out of 13 animal studies reported specific diurnal variation in pain intensity, with five of the seven studies reporting a trend towards increased sensitivity to mechanical allodynia or thermal hyperalgesia in the late light to dark phase. All eight studies on human subjects reported a diurnal variation in the intensity of neuropathic pain where there was an increase in pain intensity through the day with peaks in late evening and early night hours.

CONCLUSIONS

Studies included in this review demonstrated a diurnal variation in the pattern of neuropathic pain that is distinct from the pattern for nociceptive pain. These findings have implications for potential therapeutic strategies for neuropathic pain.

Circadian clock core component Bmal1 dictates cell cycle rhythm of proliferating hepatocytes during liver regeneration

After partial hepatectomy (PH), the majority of remnant hepatocytes synchronously enter and rhythmically progress through the cell cycle for three major rounds to regain lost liver mass. Whether and how the circadian clock core component Bmal1 modulates this process remains elusive. We performed PH on Bmal1+/+ and hepatocyte-specific Bmal1 knockout (Bmal1hep-/-) mice and compared the initiation and progression of the hepatocyte cell cycle. After PH, Bmal1+/+ hepatocytes exhibited three major waves of nuclear DNA synthesis. In contrast, in Bmal1hep-/- hepatocytes, the first wave of nuclear DNA synthesis was delayed by 12 h, and the third such wave was lost. Following PH, Bmal1+/+ hepatocytes underwent three major waves of mitosis, whereas Bmal1hep-/- hepatocytes fully abolished mitotic oscillation. These Bmal1-dependent disruptions in the rhythmicity of hepatocyte cell cycle after PH were accompanied by suppressed expression peaks of a group of cell cycle components and regulators and dysregulated activation patterns of mitogenic signaling molecules c-Met and epidermal growth factor receptor. Moreover, Bmal1+/+ hepatocytes rhythmically accumulated fat as they expanded following PH, whereas this phenomenon was largely inhibited in Bmal1hep-/- hepatocytes. In addition, during late stages of liver regrowth, Bmal1 absence in hepatocytes caused the activation of redox sensor Nrf2, suggesting an oxidative stress state in regenerated liver tissue. Collectively, we demonstrated that during liver regeneration, Bmal1 partially modulates the oscillation of S-phase progression, fully controls the rhythmicity of M-phase advancement, and largely governs fluctuations in fat metabolism in replicating hepatocytes, as well as eventually determines the redox state of regenerated livers.NEW & NOTEWORTHY We demonstrated that Bmal1 centrally controls the synchronicity and rhythmicity of the cell cycle and lipid accumulation in replicating hepatocytes during liver regeneration. Bmal1 plays these roles, at least in part, by ensuring formation of the expression peaks of cell cycle components and regulators, as well as the timing and levels of activation of mitogenic signaling molecules.

Energy Balance and Control of Body Weight: Possible Effects of Meal Timing and Circadian Rhythm Dysregulation

Conservation of the energy equilibrium can be considered a dynamic process and variations of one component (energy intake or energy expenditure) cause biological and/or behavioral compensatory changes in the other part of the system. The interplay between energy demand and caloric intake appears designed to guarantee an adequate food supply in variable life contexts. The circadian rhythm plays a major role in systemic homeostasis by acting as “timekeeper” of the human body, under the control of central and peripheral clocks that regulate many physiological functions such as sleep, hunger and body temperature. Clock-associated biological processes anticipate the daily demands imposed by the environment, being synchronized under ideal physiologic conditions. Factors that interfere with the expected demand, including daily distribution of macronutrients, physical activity and light exposure, may disrupt the physiologic harmony between predicted and actual behavior. Such a desynchronization may favor the development of a wide range of disease-related processes, including obesity and its comorbidities. Evidence has been provided that the main components of 24-h EE may be affected by disruption of the circadian rhythm. The sleep pattern, meal timing and meal composition could mediate these effects. An increased understanding of the crosstalk between disruption of the circadian rhythm and energy balance may shed light on the pathophysiologic mechanisms underlying weight gain, which may eventually lead to design effective strategies to fight the obesity pandemic.

Mitochondrially localized MPZL3 emerges as a signaling hub of mammalian physiology

MPZL3 is a nuclear-encoded, mitochondrially localized, immunoglobulin-like V-type protein that functions as a key regulator of epithelial cell differentiation, lipid metabolism, ROS production, glycemic control, and energy expenditure. Recently, MPZL3 has surfaced as an important modulator of sebaceous gland function and of hair follicle cycling, an organ transformation process that is also governed by peripheral clock gene activity and PPARγ. Given the phenotype similarities and differences between Mpzl3 and Pparγ knockout mice, we propose that MPZL3 serves as a signaling hub that is regulated by core clock gene products and/or PPARγ to translate signals from these nuclear transcription factors to the mitochondria to modulate circadian and metabolic regulation. Conservation between murine and human MPZL3 suggests that human MPZL3 may have similarly complex functions in health and disease. We summarize current knowledge and discuss future directions to elucidate the full spectrum of MPZL3 functions in mammalian physiology.

Eat, sleep, repeat - endocrine regulation of behavioural circadian rhythms

The adaptation of organisms to a rhythmic environment is mediated by an internal timing system termed the circadian clock. In mammals, molecular clocks are found in all tissues and organs. This circadian clock network regulates the release of many hormones, which in turn influence some of the most vital behavioural functions. Sleep-wake cycles are under strict circadian control with strong influence of rhythmic hormones such as melatonin, cortisol and others. Food intake, in contrast, receives circadian modulation through hormones such as leptin, ghrelin, insulin and orexin. A third behavioural output covered in this review is mating and bonding behaviours, regulated through circadian rhythms in steroid hormones and oxytocin. Together, these data emphasize the pervasive influence of the circadian clock system on behavioural outputs and its mediation through endocrine networks.