Potential Roles of Dec and Bmal1 Genes in Interconnecting Circadian Clock and Energy Metabolism

The Influence of Circadian Rhythms on DNA Damage Repair in Skin Photoaging

Circadian rhythms, the internal timekeeping systems governing physiological processes, significantly influence skin health, particularly in response to ultraviolet radiation (UVR). Disruptions in circadian rhythms can exacerbate UVR-induced skin damage and increase the risk of skin aging and cancer. This review explores how circadian rhythms affect various aspects of skin physiology and pathology, with a special focus on DNA repair. Circadian regulation ensures optimal DNA repair following UVR-induced damage, reducing mutation accumulation, and enhancing genomic stability. The circadian control over cell proliferation and apoptosis further contributes to skin regeneration and response to UVR. Oxidative stress management is another critical area where circadian rhythms exert influence. Key circadian genes like brain and muscle ARNT-like 1 (BMAL1) and circadian locomotor output cycles kaput (CLOCK) modulate the activity of antioxidant enzymes and signaling pathways to protect cells from oxidative stress. Circadian rhythms also affect inflammatory and immune responses by modulating the inflammatory response and the activity of Langerhans cells and other immune cells in the skin. In summary, circadian rhythms form a complex defense network that manages UVR-induced damage through the precise regulation of DNA damage repair, cell proliferation, apoptosis, inflammatory response, oxidative stress, and hormonal signaling. Understanding these mechanisms provides insights into developing targeted skin protection and improving skin cancer prevention.

O-GlcNAcylation of circadian clock protein Bmal1 impairs cognitive function in diabetic mice

Neuronal damage in the hippocampus induced by high glucose has been shown to promote the onset and development of cognitive impairment in diabetes, but the underlying molecular mechanism remains unclear. Guided by single-cell RNA sequencing, we here report that high glucose increases O-GlcNAcylation of Bmal1 in hippocampal neurons. This glycosylation promotes the binding of Clock to Bmal1, resulting in the expression of transcription factor Bhlhe41 and its target Dnajb4. Upregulated Dnajb4 in turn leads to ubiquitination and degradation of the mitochondrial Na + /Ca2+ exchanger NCLX, thereby inducing mitochondrial calcium overload that causes neuronal damage and cognitive impairment in mice. Notably, Bhlhe41 downregulation or treatment with a short peptide that specifically blocks O-GlcNAcylation of Bmal1 on Ser424 mitigated these adverse effects in diabetic mouse models. These data highlight the crucial role of O-GlcNAcylation in circadian clock gene expression and may facilitate the design of targeted therapies for diabetes-associated cognitive impairment.

The clock gene BHLHE40 and atypical CCNG2 control androgen-induced cellular senescence as a novel tumor suppressive pathway in prostate cancer

BACKGROUND

The androgen receptor (AR) is a drug target used to inhibit AR and prostate cancer (PCa) growth. Surprisingly, treatment with supraphysiological androgen level (SAL), used in bipolar androgen therapy, inhibits growth of PCa suggesting a tumor-suppressive activity by SAL. SAL was shown to induce cellular senescence in PCa.

METHODS

RNA-seq and transcriptome analysis, ChIP-seq, human 3D PCa spheroids, mouse xenografted castration-resistant PCa, knockdown and overexpression, Co-immunoprecipitation (Co-IP), translocation analysis, immune detection, qRT-PCR, protein-protein interaction modelling.

RESULTS

Here, mice xenografts with castration-resistant PCa tumors show that SAL inhibits cancer growth in vivo suggesting that SAL activates a tumor-suppressive mechanism. RNA-seq and ChIP-seq revealed the clock gene BHLHE40 is a novel direct AR target. Compared to adjacent human prostate tissues, the expression of BHLHE40 is reduced in PCa tumors and associated with reduced survival. Knockdown suggests that BHLHE40 mediates SAL-induced cellular senescence including tumor spheroids. Interestingly, a large overlap of differentially expressed gene sets was identified between BHLHE40 and SAL leading to the identification of four classes of SAL-BHLHE40 transcriptome landscapes. Co-IP and modelling suggest binding of BHLHE40 to AR and their co-translocation into nucleus by SAL treatment. Further, RNA-seq and ChIP-seq analysis indicate that the atypical tumor suppressive cyclin G2 emerged as a novel downstream target of BHLHE40 and a mediator of SAL-induced cellular senescence.

CONCLUSIONS

The data provide evidence of the tumor suppressive activity of SAL and a novel signaling by the AR-BHLHE40-CCNG2 axis for androgen-induced cellular senescence, linking circadian rhythm factor to androgen signaling as a novel tumor suppressive pathway.

DEC1 is involved in circadian rhythm disruption-exacerbated pulmonary fibrosis

BACKGROUND

The alveolar epithelial type II cell (AT2) and its senescence play a pivotal role in alveolar damage and pulmonary fibrosis. Cell circadian rhythm is strongly associated with cell senescence. Differentiated embryonic chondrocyte expressed gene 1 (DEC1) is a very important circadian clock gene. However, the role of DEC1 in AT2 senescence and pulmonary fibrosis was still unclear.

RESULTS

In this study, a circadian disruption model of light intervention was used. It was found that circadian disruption exacerbated pulmonary fibrosis in mice. To understand the underlying mechanism, DEC1 levels were investigated. Results showed that DEC1 levels increased in lung tissues of IPF patients and in bleomycin-induced mouse fibrotic lungs. In vitro study revealed that bleomycin and TGF-β1 increased the expressions of DEC1, collagen-I, and fibronectin in AT2 cells. Inhibition of DEC1 mitigated bleomycin-induced fibrotic changes in vitro and in vivo. After that, cell senescence was observed in bleomycin-treated AT2 cells and mouse models, but these were prevented by DEC1 inhibition. At last, p21 was confirmed having circadian rhythm followed DEC1 in normal conditions. But bleomycin disrupted the circadian rhythm and increased DEC1 which promoted p21 expression, increased p21 mediated AT2 senescence and pulmonary fibrosis.

CONCLUSIONS

Taken together, circadian clock protein DEC1 mediated pulmonary fibrosis via p21 and cell senescence in alveolar epithelial type II cells.

Gut microbiota in overweight and obesity: crosstalk with adipose tissue

Overweight and obesity are characterized by excessive fat mass accumulation produced when energy intake exceeds energy expenditure. One plausible way to control energy expenditure is to modulate thermogenic pathways in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Among the different environmental factors capable of influencing host metabolism and energy balance, the gut microbiota is now considered a key player. Following pioneering studies showing that mice lacking gut microbes (that is, germ-free mice) or depleted of their gut microbiota (that is, using antibiotics) developed less adipose tissue, numerous studies have investigated the complex interactions existing between gut bacteria, some of their membrane components (that is, lipopolysaccharides), and their metabolites (that is, short-chain fatty acids, endocannabinoids, bile acids, aryl hydrocarbon receptor ligands and tryptophan derivatives) as well as their contribution to the browning and/or beiging of WAT and changes in BAT activity. In this Review, we discuss the general physiology of both WAT and BAT. Subsequently, we introduce how gut bacteria and different microbiota-derived metabolites, their receptors and signalling pathways can regulate the development of adipose tissue and its metabolic capacities. Finally, we describe the key challenges in moving from bench to bedside by presenting specific key examples.

Loss of Dec1 inhibits alcohol-induced hepatic lipid accumulation and circadian rhythm disorder

Chronic alcohol exposure increases liver damage such as lipid accumulation and hepatitis, resulting in hepatic cirrhosis. Chronic alcohol intake is known to disturb circadian rhythms in humans and animals. DEC1, a basic helix-loop-helix transcription factor, plays an important role in the circadian rhythm, inflammation, immune responses, and tumor progression. We have previously shown that Dec1 deficiency inhibits stresses such as periodontal inflammation and perivascular fibrosis of the heart. However, the significance of Dec1 deficiency in chronic alcohol consumption remains unclear. In the present study, we investigated whether the biological stress caused by chronic alcohol intake is inhibited in Dec1 knockout mice. We treated control and Dec1 knockout mice for three months by providing free access to 10% alcohol. The Dec1 knockout mice consumed more alcohol than control mice, however, we observed severe hepatic lipid accumulation and circadian rhythm disturbance in control mice. In contrast, Dec1 knockout mice exhibited little effect on these outcomes. We also investigated the expression of peroxisome proliferator-activated receptors (PPARs) and AMP-activated protein kinase (AMPK), which are involved in the regulation of fatty acid metabolism. Immunohistochemical analysis revealed increases of phosphorylation AMPK and PPARa but decreases PPARg in Dec1 knockout mice compared to that in control mice. This indicates a molecular basis for the inhibition of hepatic lipid accumulation in alcohol-treated Dec1 knockout mice. These results suggest a novel function of Dec1 in alcohol-induced hepatic lipid accumulation and circadian rhythm disorders.

Phosphatidic acid signaling and function in nuclei

Membrane lipidomes are dynamic and their changes generate lipid mediators affecting various biological processes. Phosphatidic acid (PA) has emerged as an important class of lipid mediators involved in a wide range of cellular and physiological responses in plants, animals, and microbes. The regulatory functions of PA have been studied primarily outside the nuclei, but an increasing number of recent studies indicates that some of the PA effects result from its action in nuclei. PA levels in nuclei are dynamic in response to stimuli. Changes in nuclear PA levels can result from activities of enzymes associated with nuclei and/or from movements of PA generated extranuclearly. PA has also been found to interact with proteins involved in nuclear functions, such as transcription factors and proteins undergoing nuclear translocation in response to stimuli. The nuclear action of PA affects various aspects of plant growth, development, and response to stress and environmental changes.

Circadian clock and lipid metabolism disorders: a potential therapeutic strategy for cancer

Recent research has emphasized the interaction between the circadian clock and lipid metabolism, particularly in relation to tumors. This review aims to explore how the circadian clock regulates lipid metabolism and its impact on carcinogenesis. Specifically, targeting key enzymes involved in fatty acid synthesis (SREBP, ACLY, ACC, FASN, and SCD) has been identified as a potential strategy for cancer therapy. By disrupting these enzymes, it may be possible to inhibit tumor growth by interfering with lipid metabolism. Transcription factors, like SREBP play a significant role in regulating fatty acid synthesis which is influenced by circadian clock genes such as BMAL1, REV-ERB and DEC. This suggests a strong connection between fatty acid synthesis and the circadian clock. Therefore, successful combination therapy should target fatty acid synthesis in addition to considering the timing and duration of drug use. Ultimately, personalized chronotherapy can enhance drug efficacy in cancer treatment and achieve treatment goals.

Biomarker Development for Identifying Mud Loach (Misgurnus mizolepis) Origin Country Using Untargeted Metabolite Profiling

Mud loach (Misgurnus mizolepis) has long been consumed in Korea. Recently, Chinese mud loaches were replaced with expensive Korean mud loaches, owing to taste and preference. Such issues occur in aquatic food distribution processes, leading to inferior food delivery. Previously, a study was conducted to confirm the origin of mud loaches using genetic analysis. However, untargeted metabolites profiling of mud loaches has not been reported. Untargeted metabolomics provides information on the overall metabolic profiling of a sample, allowing the identification of new metabolites. Here, we analyzed the metabolites of mud loaches of different geographical origins using liquid chromatography (LC)-quadrupole-time-of-flight mass spectrometry (MS). Orthogonal partial least squares discriminant analysis from LC/MS datasets showed a clear distinction between Korean and Chinese mud loaches, and univariate statistical analysis showed significantly different metabolites between them. N-acetylhistidine and anserine were selected as biomarkers for geographical origin discrimination using the receiver operating characteristic curve. N-acetylhistidine and anserine levels were significantly higher in Chinese than in Korean mud loaches. These results indicate that metabolic analysis can be used to discriminate between the geographical origins of mud loaches, curtailing the inadvertent substitution of mud loaches from different regions.

CRH-R2 signalling modulates feeding and circadian gene expression in hypothalamic mHypoA-2/30 neurons

The hypothalamic type 2 corticotropin releasing hormone receptor (CRH-R2) plays critical roles in homeostatic regulation, particularly in fine tuning stress recovery. During acute stress, the CRH-R2 ligands CRH and urocortins promote adaptive responses and feeding inhibition. However, in rodent models of chronic stress, over-exposure of hypothalamic CRH-R2 to its cognate agonists is associated with urocortin 2 (Ucn2) resistance; attenuated cAMP-response element binding protein (CREB) phosphorylation and increased food intake. The molecular mechanisms involved in these altered CRH-R2 signalling responses are not well described. In the present study, we used the adult mouse hypothalamus-derived cell line mHypoA-2/30 to investigate CRH-R2 signalling characteristics focusing on gene expression of molecules involved in feeding and circadian regulation given the role of clock genes in metabolic control. We identified functional CRH-R2 receptors expressed in mHypoA-2/30 cells that differentially regulate CREB and AMP-activated protein kinase (AMPK) phosphorylation and downstream expression of the appetite-regulatory genes proopiomelanocortin (Pomc) and neuropeptide Y (Npy) in accordance with an anorexigenic effect. We studied for the first time the effects of Ucn2 on clock genes in native and in a circadian bioluminescence reporter expressing mHypoA-2/30 cells, detecting enhancing effects of Ucn2 on mRNA levels and rhythm amplitude of the circadian regulator Aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), which could facilitate anorexic responses in the activity circadian phase. These data uncover novel aspects of CRH-R2 hypothalamic signalling that might be important in regulation of circadian feeding during stress responses.

A Study on the Amelioration of Circadian Rhythm Disorders in Fat Mice Using High-Protein Diets

This innovative study investigates the effects of high-protein diets (milk protein) on the circadian rhythm of hepatic lipid metabolism. We aimed to understand how high-protein interventions regulate biological clock genes, maintain lipid metabolism balance, and affect the circadian rhythm of antioxidant levels in vivo. We divided 120 SPF-class C57BL/6J mice into the control, high-fat/low-protein (HF-LP), and high-fat/high-protein (HF-HP) groups. Mice were sacrificed during active (2 a.m. and 8 a.m.) and rest periods (2 p.m. and 8 p.m.). In the HF-LP group, hepatic lipid anabolic enzymes were consistently expressed at high levels, while key lipolytic enzymes slowly increased after feeding with no significant diurnal differences. This led to an abnormal elevation in blood lipid levels, a slow increase in and low levels of superoxide dismutase, and a rapid increase in malondialdehyde levels, deviating from the diurnal trend observed in the control group. However, high-protein interventions in the HF-HP group restored lipid synthase activity and the expression of key catabolic enzymes, exhibiting a precise circadian rhythm. It also improved the lipid-metabolism rhythm, which was disrupted by the high-fat diet. Overall, high-protein interventions restored the expression of key enzymes involved in lipid metabolism, improving the lipid-metabolism rhythm, which was disrupted by the high-fat diet.

Transcriptome and Metabolome Analyses Reveal Perfluorooctanoic Acid-Induced Kidney Injury by Interfering with PPAR Signaling Pathway

Perfluorooctanoic acid (PFOA) is widely used in aviation science and technology, transportation, electronics, kitchenware, and other household products. It is stable in the environment and has potential nephrotoxicity. To investigate the effect of PFOA exposure during pregnancy on the kidneys of offspring mice, a total of 20 mice at day 0 of gestation were randomly divided into two groups (10 mice in each group), and each group was administered 0.2 mL of PFOA at a dose of 3.5 mg/kg or deionized water by gavage during gestation. The kidney weight, kidney index, histopathological observation, serum biochemistry, transcriptomics, and metabolomics of the kidneys of the 35-day offspring mice were analyzed. In addition, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels in the kidney were measured. Transcriptome analysis results showed that 387 genes were up-regulated and 283 genes were down-regulated compared with the control group. These differentially expressed genes (DEGs) were mainly concentrated in the peroxisome-proliferator-activated receptor (PPAR) signaling pathway and circadian rhythm. Compared with the control group, 64 and 73 metabolites were up- and down-regulated, respectively, in the PFOA group. The altered metabolites were mainly enriched in the biosynthesis of unsaturated fatty acids. PFOA can affect the expression levels of circadian rhythm-related genes in the kidneys of offspring mice, and this change is influenced by the PPAR signaling pathway. PFOA causes oxidative stress in the kidneys, which is responsible for significant changes in metabolites associated with the biosynthesis of unsaturated fatty acids.

Air Pollution and Perinatal Mental Health: A Comprehensive Overview

BACKGROUND

The aim of the present study was to summarise the available data about the link between air pollution exposure and the new-onset and severity of psychiatric disorders in pregnant women during the perinatal period.

MATERIALS AND METHODS

We selected articles published until June 2022 on PubMed and the Web of Science. Pollutants included were PM2.5 (particulate matter 2.5 micrometres and smaller), PM10 (particulate matter 10 micrometres and smaller), NO2 (nitrogen dioxide), O3 (ozone), SO2 (sulphur dioxide), CO (carbon monoxide), PBDEs (polybrominated diphenyl ethers), PFAS (per- and polyfluoroalkyl substances), lead, and cadmium. The perinatal period was considered as the time of pregnancy until one year after childbirth.

RESULTS

Nine studies were included; most of them evaluated the association between exposure to air pollutants and the onset of Postpartum Depression (PPD). Two studies showed an association between, respectively, only PM2.5 and both PM2.5 and NO2 exposure and PPD onset 12 months after childbirth, while another study found a significant association between NO2 exposure and PPD occurrence 6 months after childbirth. PBDE blood levels were associated with more severe depressive symptoms. Lastly, one study observed a link between stressful symptoms and exposure to PM2.5, PM10 during pregnancy.

CONCLUSION

More comprehensive and uniform studies are required to make a roadmap for future interventions, given the growing relevance of issues such pollution and mental health, particularly during the perinatal period.

Understanding the Interplay between Air Pollution, Biological Variables, and Major Depressive Disorder: Rationale and Study Protocol of the DeprAir Study

Major depressive disorder (MDD) is a serious and disabling condition, whose etiological mechanisms are not fully understood. The aim of the DeprAir study is to verify the hypothesis that air pollution exposure may exacerbate neuroinflammation with consequent alterations in DNA methylation of genes involved in circadian rhythms and hormonal dysregulation, resulting in the worsening of depressive symptoms. The study population consists of 420 depressed patients accessing the psychiatry unit of the Policlinico Hospital (Milan, Italy), from September 2020 to December 2022. Data collection is still ongoing for about 100 subjects. For each participant demographic and lifestyle information, depression history and characteristics, as well as blood samples, were collected. MDD severity was assessed through five rating scales commonly used in clinical practice to assess the severity of affective symptoms. Exposure to particulate and gaseous air pollutants is assigned to each subject using both air pollution monitoring station measurements and estimates derived from a chemical transport model. DeprAir is the first study investigating in a comprehensive picture whether air pollution exposure could be an important modifiable environmental factor associated with MDD severity and which biological mechanisms mediate the negative effect of air pollution on mental health. Its results will represent an opportunity for preventive strategies, thus entailing a tremendous impact on public health.

Tris(4-chlorophenyl)methane and tris(4-chlorophenyl)methanol disrupt pancreatic organogenesis and gene expression in zebrafish embryos

OBJECTIVES

Tris(4-chlorophenyl) methane (TCPM) and tris(4-chlorophenyl)methanol (TCPMOH) are anthropogenic environmental contaminants believed to be manufacturing byproducts of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) due to environmental co-occurrence. TCPM and TCPMOH are persistent, bioaccumulate in the environment, and are detected in human breast milk and adipose tissues. DDT exposures have been previously shown to disrupt insulin signaling and glucoregulation, increasing risk for diabetes. We have previously shown that embryonic exposures organochlorines such as polychlorinated biphenyls disrupted pancreatic development and early embryonic glucoregulatory networks. Here, we determined the impacts of the similar compounds TCPM and TCPMOH on zebrafish pancreatic growth and gene expression following developmental exposures.

METHODS

Zebrafish embryos were exposed to 50 nM TCPM or TCPMOH beginning at 24 hr postfertilization (hpf) and exposures were refreshed daily. At 96 hpf, pancreatic growth and islet area were directly visualized in Tg(ptf1a::GFP) and Tg(insulin::GFP) embryos, respectively, using microscopy. Gene expression was assessed at 100 hpf with RNA sequencing.

RESULTS

Islet and total pancreas area were reduced by 20.8% and 13% in embryos exposed to 50 nM TCPMOH compared to controls. TCPM did not induce significant morphological changes to the developing pancreas, indicating TCPMOH, but not TCPM, impairs pancreatic development despite similarity in molecular responses. Transcriptomic responses to TCPM and TCPMOH were correlated (R²  = .903), and pathway analysis found downregulation of processes including retinol metabolism, circadian rhythm, and steroid biosynthesis.

CONCLUSION

Overall, our data suggest that TCPM and TCPMOH may be hazardous to embryonic growth and development.

Histological analysis of a Becker muscular dystrophy case, diurnal expression of dystrophin in control mice and decreased expression of dystrophin in Bmal1 knockout mice

Becker muscular dystrophy (BMD) is a hereditary disease characterized by dystrophin deletion that consequently induces muscle weakness, cardiac hypertrophy and cardiac failure; These conditions are similar to those in Duchenne muscular dystrophy. The circadian rhythm is a physiological phenomenon that is predominantly regulated by the transcription and translation of clock genes. Bmal1 (Brain and muscle Arnt-like protein 1) is one of the core clock genes, and its deficiency disturbs the circadian rhythm, results in cardiac hypertrophy and cardiac failure. Dystrophin expression under diurnal conditions and in Bmal1 deficiency is yet to be elucidated. In this study, we analyzed the heart and lungs sampled during a BMD autopsy. Macroscopical examination revealed a large heart and dilated cardiomyopathy. Microscopical examination revealed an undulated structure, as well as the degeneration, and necrosis of myocardial cells. We also analyzed dystrophin expression in tissues obtained from human autopsies and mice. In human autopsy cases, dystrophin expression was lower in the heart with BMD compared that in the heart with non-BMD hypertrophy. In the heart and muscle of control mice, dystrophin expression was higher at ZT0 than at ZT12. The dystrophin expression was found to be lower in heart-specific Bmal1 knockout mice compared to that in the control mice. Hence, our study indicated that BMD was closely associated with cardiac hypertrophy and cardiac failure, while dystrophin had a diurnal expression pattern in control mice that was regulated by Bmal1.

The Influence of Circadian Rhythm on the Activity of Oxidative Stress Enzymes

The circadian system synchronizes daily with the day-night cycle of our environment. Disruption of this rhythm impacts the emergence and development of many diseases caused, for example, by the overproduction of free radicals, leading to oxidative damage of cellular components. The goal of this study was to determine the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione transferase (GST), glutathione reductase (R-GSSG), and the concentration of glutathione (GSH) in the circadian rhythm. The study group comprised 66 healthy volunteers (20-50 years; 33 women; 33 men). The blood was collected at 2, 8 a.m., and 2, 8 p.m. All samples marked the serum melatonin concentration to confirm the correct sleeping rhythm and wakefulness throughout the day. The activity of study enzymes and the concentration of GSH were measured by the spectrophotometric method. Confirmed the existence of circadian regulation of oxidative stress enzymes except for GST activity. The peak of activity of study enzymes and GSH concentration was observed at 2 a.m. The increased activity of enzymes and the increase in GSH concentration observed at night indicate that during sleep, processes allowing to maintain of the redox balance are intensified, thus limiting the formation of oxidative stress.

Sex-specific genetic association of brain and muscle Arnt-like protein-1 (BMAL1) and obesity in Chinese youth

BACKGROUND

The circadian clock gene brain and muscle Arnt-like protein-1 (BMAL1) regulates energy metabolism, adipocyte proliferation and differentiation, glucose metabolism, and other functions. This study aimed to examine the association of potential polymorphisms in BMAL1 with obesity among Chinese youth.

METHODS

A total of 2973 participants were included in this study. According to the body mass index obesity standard of China, 208 subjects were defined as experiencing general obesity. According to the waist-to-hip ratio obesity standard, 335 participants were defined as experiencing central obesity. Four single nucleotide polymorphisms (SNPs) (rs9633835, rs6486121, rs7107287, and rs12364562) were genotyped using TaqMan probe techniques.

RESULTS

There was no significant difference in the either genotypic or allelic frequencies between the non-general and general obesity groups, while a positive association was observed between BMAL1 rs6486121 variant and central obesity risk (CC＋CT vs. TT: OR:2.139, 95% CI:1.164-3.930; P = 0.014) after adjusting for covariates. Stratification analyses revealed significant associations with central obesity risk for rs6486121 polymorphism in women according to the additive model (CC vs. CT vs. TT: OR：1.409; 95 % CI: 1.029-1.930; P = 0.032). Haplotype analysis showed that only paired haplotypes, including rs9633835G with rs6486121T, had a significant effect on central obesity with OR (95%CI) was 1.035 (1.011-1.060) and P = 0.004.

CONCLUSION

our findings suggest that BMAL1 polymorphisms are significantly associated with central obesity and sex-specific genetic effects on BMAL1-mediated genetic susceptibility to obesity.

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

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

Co-regulation of circadian clock genes and microRNAs in bone metabolism

Mammalian bone is constantly metabolized from the embryonic stage, and the maintenance of bone health depends on the dynamic balance between bone resorption and bone formation, mediated by osteoclasts and osteoblasts. It is widely recognized that circadian clock genes can regulate bone metabolism. In recent years, the regulation of bone metabolism by non-coding RNAs has become a hotspot of research. MicroRNAs can participate in bone catabolism and anabolism by targeting key factors related to bone metabolism, including circadian clock genes. However, research in this field has been conducted only in recent years and the mechanisms involved are not yet well established. Recent studies have focused on how to target circadian clock genes to treat some diseases, such as autoimmune diseases, but few have focused on the co-regulation of circadian clock genes and microRNAs in bone metabolic diseases. Therefore, in this paper we review the progress of research on the co-regulation of bone metabolism by circadian clock genes and microRNAs, aiming to provide new ideas for the prevention and treatment of bone metabolic diseases such as osteoporosis.

Sex Differences in Diurnal Sodium Handling During Diet-Induced Obesity in Rats

BACKGROUND

Emerging evidence over the past several years suggests that diurnal control of sodium excretion is sex dependent and involves the renal endothelin system. Given recent awareness of disruptions of circadian function in obesity, we determined whether diet-induced obesity impairs renal handling of an acute salt load at different times of day and whether this varies by sex and is associated with renal endothelin dysfunction.

METHODS

Male and female Sprague-Dawley rats were placed on a high-fat diet for 8 weeks before assessing renal sodium handling and blood pressure.

RESULTS

Male, but not female, rats on high fat had a significantly reduced natriuretic response to acute NaCl injection at the beginning of their active period that was associated with lower endothelin 1 (ET-1) excretion, lower ET-1 mRNA expression in the cortex and outer medulla as well as lower ET_B receptor expression in the outer medulla of the high-fat rats. Obese males also had significantly higher blood pressure (telemetry) that was exacerbated by adding high salt to the diet during the last 2 weeks. While female rats developed hypertension with a high-fat diet, they were not salt sensitive and ET-1 excretion was unchanged.

CONCLUSIONS

These data identify diet-induced obesity as a sex-specific disruptive factor for maintaining proper sodium handling. Although high-fat diets induce hypertension in both sexes, these data reveal that males are at greater risk of salt-dependent hypertension and further suggest that females have more redundant systems that can be productive against salt-sensitive hypertension in at least some circumstances.

Maturation of beta cells: lessons from in vivo and in vitro models

The ability to maintain normoglycaemia, through glucose-sensitive insulin release, is a key aspect of postnatal beta cell function. However, terminally differentiated beta cell identity does not necessarily imply functional maturity. Beta cell maturation is therefore a continuation of beta cell development, albeit a process that occurs postnatally in mammals. Although many important features have been identified in the study of beta cell maturation, as of yet no unified mechanistic model of beta cell functional maturity exists. Here, we review recent findings about the underlying mechanisms of beta cell functional maturation. These findings include systemic hormonal and nutritional triggers that operate through energy-sensing machinery shifts within beta cells, resulting in primed metabolic states that allow for appropriate glucose trafficking and, ultimately, insulin release. We also draw attention to the expansive synergistic nature of these pathways and emphasise that beta cell maturation is dependent on overlapping regulatory and metabolic networks.

Differentiated embryonic chondrocyte expressed gene-1 (DEC1) enhances the development of colorectal cancer with an involvement of the STAT3 signaling

Colorectal cancer (CRC) is the second deadly and the third most common malignancy worldwide. It has been projected that annual new cases of CRC will increase by 63% in 2040, constituting an even greater health challenge for decades to come. This study has linked DEC1 (differentiated embryonic chondrocyte expressed gene 1) to the pathogenesis of CRC. Based on the analysis of patient samples and database data, DEC1 is expressed much higher in CRC than the adjacent normal tissues. CRC patients with higher DEC1 expression have a shorter survival time. The carcinogenesis protocol with azoxymethane/dextran sulfate induces a higher number of tumors with larger sizes in DEC1^+/+ than DEC1^−/− mice. Overexpression of DEC1 increases the expression of proliferation- and antiapoptosis-related genes, but decreases the level of proapoptotic genes. Mechanistically, this study has shown that DEC1 is functionally looped to the IL-6/STAT3 signaling pathway (interleukin-6/signal transducer and activator of transcription 3). IL-6 induces DEC1, and DEC1 enhances the phosphorylation of STAT3, resulting in increased pSTAT3/STAT3 ratio. DEC1 and STAT3 are present in reciprocal immunocomplexes, pointing to physical interactions (presumably with pSTAT3). These findings establish that DEC1 is a CRC enhancer. The enhancement is achieved largely through the IL-6/STAT3 pathway. The potential of the physical interaction between DEC1 and STAT3 will likely serve as a foundation to develop intervention strategies for CRC prevention and therapy.

Prenatal Hypoxia Affects Foetal Cardiovascular Regulatory Mechanisms in a Sex- and Circadian-Dependent Manner: A Review

Prenatal hypoxia during the prenatal period can interfere with the developmental trajectory and lead to developing hypertension in adulthood. Prenatal hypoxia is often associated with intrauterine growth restriction that interferes with metabolism and can lead to multilevel changes. Therefore, we analysed the effects of prenatal hypoxia predominantly not associated with intrauterine growth restriction using publications up to September 2021. We focused on: (1) The response of cardiovascular regulatory mechanisms, such as the chemoreflex, adenosine, nitric oxide, and angiotensin II on prenatal hypoxia. (2) The role of the placenta in causing and attenuating the effects of hypoxia. (3) Environmental conditions and the mother's health contribution to the development of prenatal hypoxia. (4) The sex-dependent effects of prenatal hypoxia on cardiovascular regulatory mechanisms and the connection between hypoxia-inducible factors and circadian variability. We identified that the possible relationship between the effects of prenatal hypoxia on the cardiovascular regulatory mechanism may vary depending on circadian variability and phase of the days. In summary, even short-term prenatal hypoxia significantly affects cardiovascular regulatory mechanisms and programs hypertension in adulthood, while prenatal programming effects are not only dependent on the critical period, and sensitivity can change within circadian oscillations.

Postnatal regulation of B-1a cell development and survival by the CIC-PER2-BHLHE41 axis

B-1 cell development mainly occurs via fetal and neonatal hematopoiesis and is suppressed in adult bone marrow hematopoiesis. However, little is known about the factors inhibiting B-1 cell development at the adult stage. We report that capicua (CIC) suppresses postnatal B-1a cell development and survival. CIC levels are high in B-1a cells and gradually increase in transitional B-1a (TrB-1a) cells with age. B-cell-specific Cic-null mice exhibit expansion of the B-1a cell population and a gradual increase in TrB-1a cell frequency with age but attenuated B-2 cell development. CIC deficiency enhances B cell receptor (BCR) signaling in transitional B cells and B-1a cell viability. Mechanistically, CIC-deficiency-mediated Per2 derepression upregulates Bhlhe41 levels by inhibiting CRY-mediated transcriptional repression for Bhlhe41, consequently promoting B-1a cell formation in Cic-null mice. Taken together, CIC is a key transcription factor that limits the B-1a cell population at the adult stage and balances B-1 versus B-2 cell formation.

Effects of Dietary Fat to Carbohydrate Ratio on Obesity Risk Depending on Genotypes of Circadian Genes

Although the impacts of macronutrients and the circadian clock on obesity have been reported, the interactions between macronutrient distribution and circadian genes are unclear. The aim of this study was to explore macronutrient intake patterns in the Korean population and associations between the patterns and circadian gene variants and obesity. After applying the criteria, 5343 subjects (51.6% male, mean age 49.4 ± 7.3 years) from the Korean Genome and Epidemiology Study data and nine variants in seven circadian genes were analyzed. We defined macronutrient intake patterns by tertiles of the fat to carbohydrate ratio (FC). The very low FC (VLFC) was associated with a higher risk of obesity than the optimal FC (OFC). After stratification by the genotypes of nine variants, the obesity risk according to the patterns differed by the variants. In the female VLFC, the major homozygous allele of CLOCK rs11932595 and CRY1 rs3741892 had a higher abdominal obesity risk than those in the OFC. The GG genotype of PER2 rs2304672 in the VLFC showed greater risks for obesity and abdominal obesity. In conclusion, these findings suggest that macronutrient intake patterns were associated with obesity susceptibility, and the associations were different depending on the circadian clock genotypes of the CLOCK, PER2, and CRY1 loci.

Transcriptome analysis in comparing carcass and meat quality traits of Jiaxing Black Pig and Duroc × Duroc × Berkshire × Jiaxing Black Pig crosses

This study compares two typical strains: Chinese local excellent meat quality of Jiaxing Black (JXB) Pig and quadratic crossbred pig strain Duroc × Duroc × Berkshire × Jiaxing Black (DDBJ). It was found that between the two pig strains, carcass traits and meat quality traits differed significantly. This is exemplified by the leanness and dressing out percent of DDBJ that were significantly higher than JXB pigs of the same age (P < 0.05) and the better growth rate of DDBJ pigs as to JXB pigs was shown by quantifying muscle proliferation and differentiation of longissimus dorsi muscle employing Hematoxylin and Eosin staining of longissimus dorsi muscle. Nutrients such as inosinic acid, intramuscular fat, and free amino acids in the longissimus dorsi muscle were significantly higher in JXB pigs than DDBJ pigs (p < 0.0001); saturated fatty acids were higher in JXB than in DDBJ pigs (p = 0.0097); essential amino acids and fresh taste amino acids (serine, glutamic acid, proline, glycine, alanine) of JXB pigs was higher than that of DDBJ pigs (p < 0.0001) and amino acids in longissimus dorsi muscle of JXB pigs surpasses the amino acid concentration of DDBJ pigs (p < 0.0001), thus showing the superiority of JXB in terms of meat quality. However, the content of polyunsaturated fatty acids, which is responsible for poor meat quality, was significantly higher in the longissimus dorsi muscle of DDBJ pig than JXB pigs (p < 0.0001); RNA-seq analysis of 5 biological replicates from two of the strains was performed. The screening of 164 up-regulated genes and 183 down-regulated genes found in longissimus dorsi muscle of DDBJ was done and the results identified differentially expressed genes related to muscle development, adipogenesis, amino acid metabolism, fatty acid metabolism and inosine synthesis. In conclusion, the study identified functional genes, elucidated the mechanisms associated with carcass quality traits, meat quality traits and other related traits, and provided means of genetic enhancement to improve meat quality traits and carcass traits in Chinese commercial pigs.

Seasonal differences in clock gene expression levels in buccal epithelial cells of obese men: a pilot study

Various biological processes show seasonal variations in humans, including important metabolic pathways. Seasonal changes in gene expression may affect annual differences in human immunity. We hypothesized that seasonal changes occur in clock gene expression levels that are associated with body mass index. Six non-obese men and five obese men participated in summer and winter. Two milliliters of saliva were collected, and total RNA was isolated from buccal epithelial cells in saliva. The clock gene expression levels of CLOCK, BMAL1, PER1, CRY2, REV-ERB-α, and REV-ERB-ß were examined by real-time PCR. Blood samples were measured HbA1c, glucose, insulin, adiponectin, IL-6, and TNF-α. Participants were asked about their sleeping hours and seasonal pattern. In the present study, CLOCK, BMAL1, and REV-ERB-β gene expression levels were significantly lower in winter than in summer; BMAL1 expression level was significantly lower in obese men than in non-obese. Concentrations of adiponectin and insulin were significantly different between obese and non-obese. No significant seasonal effects were observed in HbA1c, glucose, insulin, adiponectin, IL-6, or TNF-α concentrations. Sleep duration did not significantly differ between summer and winter. The short photoperiod during winter might contribute to seasonal alterations in the expression of clock genes in men. In the present results, revealed seasonal differences in clock gene expression levels might be associated with obesity. These results also showed the potential for measuring clock gene expression in a non-invasive manner using saliva samples.

PER2-mediated ameloblast differentiation via PPARγ/AKT1/β-catenin axis

Circadian rhythm is involved in the development and diseases of many tissues. However, as an essential environmental regulating factor, its effect on amelogenesis has not been fully elucidated. The present study aims to investigate the correlation between circadian rhythm and ameloblast differentiation and to explore the mechanism by which circadian genes regulate ameloblast differentiation. Circadian disruption models were constructed in mice for in vivo experiments. An ameloblast-lineage cell (ALC) line was used for in vitro studies. As essential molecules of the circadian system, Bmal1 and Per2 exhibited circadian expression in ALCs. Circadian disruption mice showed reduced amelogenin (AMELX) expression and enamel matrix secretion and downregulated expression of BMAL1, PER2, PPARγ, phosphorylated AKT1 and β-catenin, cytokeratin-14 and F-actin in ameloblasts. According to previous findings and our study, BMAL1 positively regulated PER2. Therefore, the present study focused on PER2-mediated ameloblast differentiation and enamel formation. Per2 knockdown decreased the expression of AMELX, PPARγ, phosphorylated AKT1 and β-catenin, promoted nuclear β-catenin accumulation, inhibited mineralization and altered the subcellular localization of E-cadherin in ALCs. Overexpression of PPARγ partially reversed the above results in Per2-knockdown ALCs. Furthermore, in in vivo experiments, the length of incisor eruption was significantly decreased in the circadian disturbance group compared to that in the control group, which was rescued by using a PPARγ agonist in circadian disturbance mice. In conclusion, through regulation of the PPARγ/AKT1/β-catenin signalling axis, PER2 played roles in amelogenin expression, cell junctions and arrangement, enamel matrix secretion and mineralization during ameloblast differentiation, which exert effects on enamel formation.

Differentiated embryonic chondrocyte-expressed gene 1 promotes temozolomide resistance by modulating the SP1-MGMT axis in glioblastoma

Glioblastoma multiforme (GBM) is a malignant brain tumor with a high mortality rate and poor prognosis. Temozolomide (TMZ) is a first-line drug against GBM, but resistance limits its use. We previously reported that differentiated embryonic chondrocyte (DEC1) expression is associated with TMZ resistance and poor prognosis in GBM; however, the underlying mechanism remains unclear. By using glioma cell lines with stably overexpressed or silenced DEC1, we examined the effects of DEC1 on TMZ sensitivity using proliferation assays, Western blotting, and flow cytometry. We demonstrated that DEC1 overexpression suppressed, whereas DEC1 knockdown enhanced, TMZ-induced cell apoptosis in methylguanine methyltransferase (MGMT)-positive T98G and LN18 cells but not in MGMT-negative U251 cells. Mechanistically, DEC1 positively regulated MGMT through specificity protein 1 (SP1). MGMT silencing in DEC1-overexpressing cells or overexpression in DEC1-silenced cells abrogated DEC1's effects on TMZ sensitivity, and siRNA-mediated SP1 knockdown phenocopied TMZ sensitivity, which was rescued by MGMT overexpression. Thus, DEC1 may control TMZ resistance via the SP1-MGMT axis. Immunohistochemical staining of the human glioma tissue microarray revealed that the expression levels of DEC1 and MGMT were correlated. Therefore, DEC1 expression has a predictive value for TMZ resistance and poor outcome in glioma patients, and is a novel therapeutic target in TMZ-resistant glioma.

Environmental chemicals affect circadian rhythms: An underexplored effect influencing health and fitness in animals and humans

Circadian rhythms control the life of virtually all organisms. They regulate numerous aspects ranging from cellular processes to reproduction and behavior. Besides the light-dark cycle, there are additional environmental factors that regulate the circadian rhythms in animals as well as humans. Here, we outline the circadian rhythm system and considers zebrafish (Danio rerio) as a representative vertebrate organism. We characterize multiple physiological processes, which are affected by circadian rhythm disrupting compounds (circadian disrupters). We focus on and summarize 40 natural and anthropogenic environmental circadian disrupters in fish. They can be divided into six major categories: steroid hormones, metals, pesticides and biocides, polychlorinated biphenyls, neuroactive drugs and other compounds such as cyanobacterial toxins and bisphenol A. Steroid hormones as well as metals are most studied. Especially for progestins and glucocorticoids, circadian dysregulation was demonstrated in zebrafish on the molecular and physiological level, which comprise mainly behavioral alterations. Our review summarizes the current state of knowledge on circadian disrupters, highlights their risks to fish and identifies knowledge gaps in animals and humans. While most studies focus on transcriptional and behavioral alterations, additional effects and consequences are underexplored. Forthcoming studies should explore, which additional environmental circadian disrupters exist. They should clarify the underlying molecular mechanisms and aim to better understand the consequences for physiological processes.

Metabolic effects of air pollution exposure and reversibility

Air pollution involving particulate matter smaller than 2.5 μm in size (PM2.5) is the world's leading environmental risk factor contributing to mortality through cardiometabolic pathways. In this study, we modeled early life exposure using chow-fed C57BL/6J male mice that were exposed to real-world inhaled, concentrated PM2.5 (~10 times ambient levels/~60-120 μg/m3) or filtered air over a 14-week period. We investigated the effects of PM2.5 on phenotype, the transcriptome, and chromatin accessibility and compared these with the effects of a prototypical high-fat diet (HFD) as well as cessation of exposure on phenotype reversibility. Exposure to PM2.5 impaired glucose and insulin tolerance and reduced energy expenditure and 18FDG-PET uptake in brown adipose tissue. Multiple differentially expressed gene clusters in pathways involving metabolism and circadian rhythm were noted in insulin-responsive tissues. Although the magnitude of transcriptional change detected with PM2.5 exposure was lower than that observed with a HFD, the degree of alteration in chromatin accessibility after PM2.5 exposure was significant. The novel chromatin remodeler SMARCA5 (SWI/SNF complex) was regulated in response to PM2.5 exposure, the cessation of which was associated with a reversal of insulin resistance and restoration of chromatin accessibility and nucleosome positioning near transcription start sites, as well as a reversal of exposure-induced changes in the transcriptome, including SMARCA5. These changes indicate pliable epigenetic control mechanisms following cessation of exposure.

Time to fight: targeting the circadian clock molecular machinery in cancer therapy

The circadian clock regulates a wide range of molecular pathways and biological processes. The expression of clock genes is often altered in cancer, fostering tumor initiation and progression. Inhibition and activation of core circadian clock genes, as well as treatments that restore circadian rhythmicity, have been successful in counteracting tumor growth in different experimental models. Here, we provide an up-to-date overview of studies that show the therapeutic effects of targeting the clock molecular machinery in cancer, both genetically and pharmacologically. We also highlight future areas for progress that offer a promising path towards innovative anticancer strategies. Substantial limitations in the current understanding of the complex interplay between the circadian clock and cancer in vivo need to be addressed in order to allow clock-targeting therapies in cancer.

Expression Signatures of microRNAs and Their Targeted Pathways in the Adipose Tissue of Chickens during the Transition from Embryonic to Post-Hatch Development

As the chick transitions from embryonic to post-hatching life, its metabolism must quickly undergo a dramatic switch in its major energy source. The chick embryo derives most of its energy from the yolk, a lipid-rich/carbohydrate-poor source. Upon hatching, the chick’s metabolism must then be able to utilize a lipid-poor/carbohydrate-rich source (feed) as its main form of energy. We recently found that a number of hepatically-expressed microRNAs (miRNAs) help facilitate this shift in metabolic processes in the chick liver, the main site of lipogenesis. While adipose tissue was initially thought to mainly serve as a lipid storage site, it is now known to carry many metabolic, endocrine, and immunological functions. Therefore, it would be expected that adipose tissue is also an important factor in the metabolic switch. To that end, we used next generation sequencing (NGS) and real-time quantitative PCR (RT-qPCR) to generate miRNome and transcriptome signatures of the adipose tissue during the transition from late embryonic to early post-hatch development. As adipose tissue is well known to produce inflammatory and other immune factors, we used SPF white leghorns to generate the initial miRNome and transcriptome signatures to minimize complications from external factors (e.g., pathogenic infections) and ensure the identification of bona fide switch-associated miRNAs and transcripts. We then examined their expression signatures in the adipose tissue of broilers (Ross 708). Using E18 embryos as representative of pre-switching metabolism and D3 chicks as a representative of post-switching metabolism, we identified a group of miRNAs which work concordantly to regulate a diverse but interconnected group of developmental, immune and metabolic processes in the adipose tissue during the metabolic switch. Network mapping suggests that during the first days post-hatch, despite the consumption of feed, the chick is still heavily reliant upon adipose tissue lipid stores for energy production, and is not yet efficiently using their new energy source for de novo lipid storage. A number of core master regulatory pathways including, circadian rhythm transcriptional regulation and growth hormone (GH) signaling, likely work in concert with miRNAs to maintain an essential balance between adipogenic, lipolytic, developmental, and immunological processes in the adipose tissue during the metabolic switch.

Roles of HDAC3-orchestrated circadian clock gene oscillations in diabetic rats following myocardial ischaemia/reperfusion injury

The circadian clock is closely related to the development of diabetes mellitus and cardiovascular disease, and disruption of the circadian clock exacerbates myocardial ischaemia/reperfusion injury (MI/RI). HDAC3 is a key component of the circadian negative feedback loop that controls the expression pattern of the circadian nuclear receptor Rev-erbα to maintain the stability of circadian genes such as BMAL1. However, the mechanism by which the HDAC3-orchestrated Rev-erbα/BMAL1 pathway increases MI/RI in diabetes and its relationship with mitophagy have yet to be elucidated. Here, we observed that the clock genes Rev-erbα, BMAL1, and C/EBPβ oscillations were altered in the hearts of rats with streptozotocin (STZ)-induced diabetes, with upregulated HDAC3 expression. Oscillations of Rev-erbα and BMAL1 were rapidly attenuated in diabetic MI/R hearts versus non-diabetic I/RI hearts, in accordance with impaired and rhythm-disordered circadian-dependent mitophagy that increased injury. Genetic knockdown of HDAC3 significantly attenuated diabetic MI/RI by mediating the Rev-erbα/BMAL1 circadian pathway to recover mitophagy. Primary cardiomyocytes with or without HDAC3 siRNA and Rev-erbα siRNA were exposed to hypoxia/reoxygenation (H/R) in vitro. The expression of HDAC3 and Rev-erbα in cardiomyocytes was increased under high-glucose conditions compared with low-glucose conditions, with decreased BMAL1 expression and mitophagy levels. After H/R stimulation, high glucose aggravated H/R injury, with upregulated HDAC3 and Rev-erbα expression and decreased BMAL1 and mitophagy levels. HDAC3 and Rev-erbα siRNA can alleviate high glucose-induced and H/R-induced injury by upregulating BMAL1 to increase mitophagy. Collectively, these findings suggest that disruption of HDAC3-mediated circadian gene expression oscillations induces mitophagy dysfunction, aggravating diabetic MI/RI. Cardiac-specific HDAC3 knockdown could alleviate diabetic MI/RI by regulating the Rev-erbα/BMAL1 pathway to restore the activation of mitophagy.

Circadian clock and liver energy metabolism

Circadian rhythm, generated by the circadian clock, is an internal rhythm that the body evolved to adapt to the diurnal changes in the external environment. Under its influence, mammals have distinct feeding and fasting cycles, which cause rhythmic changes in nutrient supply and demand. In recent years, many studies have shown that biorhythms are closely related to body metabolism. The liver, as the metabolism center of the body, is affected by circadian rhythm. However, with the acceleration of the pace of modern life and the change of life styles, the body's original rhythm is disrupted, resulting in a significant increase in the incidence of liver related metabolic diseases. Meanwhile, the disorder of circadian rhythm can also promote the occurrence and development of these diseases, and affect their prognosis and outcome. This paper reviews the relationship between the function of liver clock genes and the metabolism of liver glucose, lipids, bile acids, protein, etc.

The Effect of Rev-erbα Agonist SR9011 on the Immune Response and Cell Metabolism of Microglia

Microglia are the immune cells of the brain. Hyperactivation of microglia contributes to the pathology of metabolic and neuroinflammatory diseases. Evidence has emerged that links the circadian clock, cellular metabolism, and immune activity in microglia. Rev-erb nuclear receptors are known for their regulatory role in both the molecular clock and cell metabolism, and have recently been found to play an important role in neuroinflammation. The Rev-erbα agonist SR9011 disrupts circadian rhythm by altering intracellular clock machinery. However, the exact role of Rev-erbα in microglial immunometabolism remains to be elucidated. In the current study, we explored whether SR9011 also had such a detrimental impact on microglial immunometabolic functions. Primary microglia were isolated from 1–3 days old Sprague-Dawley rat pups. The expression of clock genes, cytokines and metabolic genes was evaluated using RT-PCR and rhythmic expression was analyzed. Phagocytic activity was determined by the uptake capacity of fluorescent microspheres. Mitochondria function was evaluated by measuring oxygen consumption rate and extracellular acidification rate. We found that key cytokines and metabolic genes are rhythmically expressed in microglia. SR9011 disturbed rhythmic expression of clock genes in microglia. Pro-inflammatory cytokine expression was attenuated by SR9011 during an immune challenge by TNFα, while expression of the anti-inflammatory cytokine Il10 was stimulated. Moreover, SR9011 decreased phagocytic activity, mitochondrial respiration, ATP production, and metabolic gene expression. Our study highlights the link between the intrinsic clock and immunometabolism of microglia. We show that Rev-erbα is implicated in both metabolic homeostasis and the inflammatory responses in microglia, which has important implications for the treatment of metabolic and neuroinflammatory diseases.

Disabling MNK protein kinases promotes oxidative metabolism and protects against diet-induced obesity

Objectives

Diet-driven obesity is increasingly widespread. Its consequences pose major challenges to human health and health care systems. There are MAP kinase-interacting kinases (MNKs) in mice, MNK1 and MNK2. Studies have demonstrated that mice lacking either MNK1 or MNK2 were partially protected against high-fat diet (HFD)-induced weight gain and insulin resistance. The aims of this study were to evaluate the phenotype of mice lacking both MNKs when given an HFD, to assess whether pharmacological inhibition of MNK function also protects against diet-induced obesity (DIO) and its consequences and to probe the mechanisms underlying such protection.

Methods

Male wild-type (WT) C57Bl6 mice or mice lacking both MNK1 and MNK2 (double knockout, DKO) were fed an HFD or control diet (CD) for up to 16 weeks.

In a separate study, WT mice were also given an HFD for 6 weeks, after which half were treated with the recently-developed MNK inhibitor ETC-206 daily for 10 more weeks while continuing an HFD. Metabolites and other parameters were measured, and the expression of selected mRNAs and proteins was assessed.

Results

MNK-DKO mice were almost completely protected from HFD-induced obesity. Higher energy expenditure (EE) in MNK-DKO mice was observed, which probably reflects the changes in a number of genes or proteins linked to lipolysis, mitochondrial function/biogenesis, oxidative metabolism, and/or ATP consumption. The MNK inhibitor ETC-206 also prevented HFD-induced weight gain, confirming that the activity of the MNKs facilitates weight gain due to excessive caloric consumption.

Conclusions

Disabling MNKs in mice, either genetically or pharmacologically, strongly prevents weight gain on a calorie-rich diet. This finding likely results from increased energy utilisation, involving greater ATP consumption, mitochondrial oxidative metabolism, and other processes.

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Knockout of MNK1/MNK2 protects mice against diet-induced obesity.

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MNK1/2 DKO mice have higher energy expenditure.

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MNK1/2 DKO increases the expression of genes of lipid and mitochondrial metabolism.

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Pharmacological inhibition of MNKs has similar effects.

Genetic Associations of Chronotype in the Finnish General Population

Individuals with a later chronotype (evening types) tend to have unhealthier behaviors and increased morbidity and mortality as compared with those with an earlier chronotype (morning types). However, the role of genetics in explaining evening types' adverse health and health behavior is unclear. Our aim was to study genetic associations of chronotype among 8433 Finns from the cross-sectional National FINRISK 2007 and 2012 studies. First, we studied associations between chronotype and 20 key clock genes with a candidate-gene approach and then performed a full genome-wide association study (GWAS) of chronotype. We also developed a genetic risk score (GRS) for chronotype based on 313 single nucleotide polymorphisms (SNPs) that have previously been associated with chronotype. Chronotype was assessed with a shortened version of Horne and Östberg's Morningness-Eveningness Questionnaire (sMEQ), and for comparison, we also used the single self-evaluation question on chronotype from the questionnaire. Linear and logistic regression was used for statistical analysis assuming additive effects. The clock gene analysis revealed 1 independent association signal within NR1D2 (lead SNP rs4131403) that was associated with chronotype (p < 0.05; as based on both chronotype assessment methods). The GWAS analysis did not yield any genome-wide significant associations (p > 5 × 10^-8). However, higher GRS was associated with evening chronotype (p < 0.001; as based on both chronotype assessment methods). In conclusion, our findings indicated novel genetic associations between chronotype and the NR1D2 clock gene, which has previously been associated with carbohydrate and lipid metabolism. Furthermore, the GRS was able to capture the genetic aspect of chronotype in our study population. These findings expand our knowledge of the genetic basis of chronotype.

Downregulation of DEC1 by RNA interference attenuates ischemia/reperfusion-induced myocardial inflammation by inhibiting the TLR4/NF-κB signaling pathway

Inflammation has been implicated in the pathogenesis of myocardial ischemia/reperfusion (I/R) injury (MIRI). Previous studies have confirmed that deleted in esophageal cancer 1 (DEC1) is an important transcription factor in inflammation. However, the role of DEC1 in MIRI remains unclear. The present study aimed to determine whether the downregulation of DEC1 by RNA interference alleviated inflammation to protect against MIRI. Adult Sprague-Dawley rats (n=48) were randomly divided into four groups: Sham; I/R; adenovirus expressing green fluorescent protein control (Ad-G-Control); and DEC1-targeting RNA interference (Ad-G-DEC1) groups. Following gene delivery 4 days later, the rat myocardial I/R model was established and myocardial enzymes [creatine kinase (CK) and lactate dehydrogenase (LDH)] were detected. Hematoxylin and eosin (H&E) staining was performed to evaluate the myocardial damage and the infarct area was assessed using Evans Blue/triphenyltetrazolium chloride staining. The inflammatory mediators interleukin (IL)-β and tumor necrosis factor (TNF)-α were also detected using ELISA kits to assess the inflammatory response. Finally, western blotting and reverse transcription-quantitative PCR were used to analyze the expression levels of associated proteins and mRNAs. Ad-G-DEC1 RNA interference markedly decreased DEC1 expression levels. In addition, following the downregulation of DEC1 expression, the infarct size, CK, LDH, Toll-like receptor (TLR)4, NF-κB, IL-β and TNF-α levels were all significantly decreased. In conclusion, the results of the present study suggested that the downregulation of DEC1 may decrease the inflammation by suppressing the TLR4/NF-κB signaling pathway, which may represent a therapeutic target for MIRI.

Circadian Clock Component Rev-erbα Regulates Diurnal Rhythm of UDP-Glucuronosyltransferase 1a9 and Drug Glucuronidation in Mice

UDP-glucuronosyltransferases (UGTs) are a family of phase II enzymes that play an important role in metabolism and elimination of numerous endo- and xenobiotics. Here, we aimed to characterize diurnal rhythm of Ugt1a9 in mouse liver and to determine the molecular mechanisms underlying the rhythmicity. Hepatic Ugt1a9 mRNA and protein displayed robust diurnal rhythms in wild-type mice with peak levels at zeitgeber time (ZT) 6. Rhythmicity in Ugt1a9 expression was confirmed using synchronized Hepa-1c1c7 cells. We observed time-varying glucuronidation (ZT6 > ZT18) of propofol, a specific Ugt1a9 substrate, consistent with the diurnal pattern of Ugt1a9 protein. Loss of Rev-erbα (a circadian clock component) downregulated the Ugt1a9 expression and blunted its rhythm in mouse liver. Accordingly, propofol glucuronidation was reduced and its dosing time dependency was lost in Rev-erbα ^-/- mice. Dec2 (a transcription factor) was screened to be the potential intermediate that mediated Rev-erbα regulation of Ugt1a9. We confirmed Rev-erbα as a negative regulator of Dec2 in mice and in Hepa-1c1c7 cells. Based on promoter analysis and luciferase reporter assays, it was found that Dec2 trans-repressed Ugt1a9 via direct binding to an E-box-like motif in the gene promoter. Additionally, regulation of Ugt1a9 by Rev-erbα was Dec2-dependent. In conclusion, Rev-erbα generates and regulates rhythmic Ugt1a9 through periodical inhibition of Dec2, a transcriptional repressor of Ugt1a9. Our study may have implications for understanding of circadian clock-controlled drug metabolism and of metabolism-based chronotherapeutics. SIGNIFICANCE STATEMENT: Hepatic Ugt1a9 displays diurnal rhythmicities in expression and glucuronidation activity in mice. It is uncovered that Rev-erbα generates and regulates rhythmic Ugt1a9 through periodical inhibition of Dec2, a transcriptional repressor of Ugt1a9. The findings may have implications for understanding of circadian clock-controlled drug metabolism and of metabolism-based chronotherapeutics.

Gut microbiota: closely tied to the regulation of circadian clock in the development of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM), a worldwide epidemic disease, has caused tremendous economic and social burden, but the pathogenesis remains uncertain. Nowadays, the impact of unrhythmic circadian clock caused by irregular sleep and unhealthy diet on T2DM has be increasingly studied. However, the contribution of the endogenous circadian clock system to the development of T2DM has not yet been satisfactorily explored. It is now becoming clear that the gut microbiota and the circadian clock interact with each other to regulate the host metabolism. Considering all these above, we reviewed the literature related to the gut microbiota, circadian clock, and T2DM to elucidate the idea that the gut microbiota is closely tied to the regulation of the circadian clock in the development of T2DM, which provides potential for gut microbiota-directed therapies to ameliorate the effects of circadian disruptions linked to the occurrence and development of T2DM.

Circadian Clock, Time-Restricted Feeding and Reproduction

The goal of this review was to seek a better understanding of the function and differential expression of circadian clock genes during the reproductive process. Through a discussion of how the circadian clock is involved in these steps, the identification of new clinical targets for sleep disorder-related diseases, such as reproductive failure, will be elucidated. Here, we focus on recent research findings regarding circadian clock regulation within the reproductive system, shedding new light on circadian rhythm-related problems in women. Discussions on the roles that circadian clock plays in these reproductive processes will help identify new clinical targets for such sleep disorder-related diseases.

Interaction of melatonin and Bmal1 in the regulation of PI3K/AKT pathway components and cellular survival

The circadian rhythm is driven by a master clock within the suprachiasmatic nucleus which regulates the rhythmic secretion of melatonin. Bmal1 coordinates the rhythmic expression of transcriptome and regulates biological activities, involved in cell metabolism and aging. However, the role of Bmal1 in cellular- survival, signaling, its interaction with intracellular proteins, and how melatonin regulates its expression is largely unclear. Here we observed that melatonin increases the expression of Bmal1 and both melatonin and Bmal1 increase cellular survival after oxygen glucose deprivation (OGD) while the inhibition of Bmal1 resulted in the decreased cellular survival without affecting neuroprotective effects of melatonin. By using a planar surface immunoassay for PI3K/AKT signaling pathway components, we revealed that both melatonin and Bmal1 increased phosphorylation of AKT, ERK-1/2, PDK1, mTOR, PTEN, GSK-3αβ, and p70S6K. In contrast, inhibition of Bmal1 resulted in decreased phosphorylation of these proteins, which the effect of melatonin on these signaling molecules was not affected by the absence of Bmal1. Besides, the inhibition of PI3K/AKT decreased Bmal1 expression and the effect of melatonin on Bmal1 after both OGD in vitro and focal cerebral ischemia in vivo. Our data demonstrate that melatonin controls the expression of Bmal1 via PI3K/AKT signaling, and Bmal1 plays critical roles in cellular survival via activation of survival kinases.

From circadian clocks to non-alcoholic fatty liver disease

Introduction: The circadian rhythm is an integral regulator of various endocrine processes in the body, including sleep-wake cycles, hormonal regulation, and metabolism. In addition to metabolic, genetic, and environmental factors, a dysregulated circadian rhythm resulting from lifestyle changes has been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). An accumulating body of evidence also supports strong association between NAFLD and metabolic disorder, the pathogenesis of which is related to periodic fluctuations in hormonal homeostasis. It is clear that endocrine and circadian rhythms are tightly interconnected. Generally, the circadian rhythm regulates flux patterns of physiological functions. The present review will discuss the modulation of bodily processes by the circadian rhythm with specific attention to the regulation of NAFLD by leptin and related hormones.Areas covered: PubMed/MEDLINE was searched for articles related to concomitant occurrence of NAFLD and T2DM between January 1995 and September 2019. Areas covered included epidemiological, physiology and pathophysiology aspects.Expert opinion: NAFLD and NASH are increasingly prevalent and may be largely mitigated with effective lifestyle modification and, potentially, circadian rhythm stabilization. Improved knowledge of the specific pathogenesis of NAFLD in addition to enhanced diagnostic screening tools and prediction of future disease burden is imperative.

Circadian Clock Genes in the Metabolism of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a common disease, which is characterized by the accumulation of triglycerides in the hepatocytes without excess alcohol intake. Circadian rhythms can participate in lipid, glucose, and cholesterol metabolism and are closely related to metabolism seen in this disease. Circadian clock genes can modulate liver lipid metabolism. Desynchrony of circadian rhythms and the influences imparted by external environmental stimuli can increase morbidity. By contrast, synchronizing circadian rhythms can help to alleviate the metabolic disturbance seen in NAFLD. In this review, we have discussed the current research connections that exist between the circadian clock and the metabolism of NAFLD, and we have specifically focused on the key circadian clock genes, Bmal1, Clock, Rev-Erbs, Rors, Pers, Crys, Nocturnin, and DECs.

Circadian rhythms and proteomics: It's all about posttranslational modifications!

The circadian clock is a molecular endogenous timekeeping system and allows organisms to adjust their physiology and behavior to the geophysical time. Organized hierarchically, the master clock in the suprachiasmatic nuclei, coordinates peripheral clocks, via direct, or indirect signals. In peripheral organs, such as the liver, the circadian clock coordinates gene expression, notably metabolic gene expression, from transcriptional to posttranslational level. The metabolism in return feeds back on the molecular circadian clock via posttranslational-based mechanisms. During the last two decades, circadian gene expression studies have mostly been relying primarily on genomics or transcriptomics approaches and transcriptome analyses of multiple organs/tissues have revealed that the majority of protein-coding genes display circadian rhythms in a tissue specific manner. More recently, new advances in mass spectrometry offered circadian proteomics new perspectives, that is, the possibilities of performing large scale proteomic studies at cellular and subcellular levels, but also at the posttranslational modification level. With important implications in metabolic health, cell signaling has been shown to be highly relevant to circadian rhythms. Moreover, comprehensive characterization studies of posttranslational modifications are emerging and as a result, cell signaling processes are expected to be more deeply characterized and understood in the coming years with the use of proteomics. This review summarizes the work studying diurnally rhythmic or circadian gene expression performed at the protein level. Based on the knowledge brought by circadian proteomics studies, this review will also discuss the role of posttranslational modification events as an important link between the molecular circadian clock and metabolic regulation. This article is categorized under: Laboratory Methods and Technologies > Proteomics Methods Physiology > Mammalian Physiology in Health and Disease Biological Mechanisms > Cell Signaling.

"Gut Microbiota-Circadian Clock Axis" in Deciphering the Mechanism Linking Early-Life Nutritional Environment and Abnormal Glucose Metabolism

The prevalence of diabetes mellitus (DM) has been increasing dramatically worldwide, but the pathogenesis is still unknown. A growing amount of evidence suggests that an abnormal developmental environment in early life increases the risk of developing metabolic diseases in adult life, which is referred to as the "metabolic memory" and the Developmental Origins of Health and Disease (DOHaD) hypothesis. The mechanism of "metabolic memory" has become a hot topic in the field of DM worldwide and could be a key to understanding the pathogenesis of DM. In recent years, several large cohort studies have shown that shift workers have a higher risk of developing type 2 diabetes mellitus (T2DM) and worse control of blood glucose levels. Furthermore, a maternal high-fat diet could lead to metabolic disorders and abnormal expression of clock genes and clock-controlled genes in offspring. Thus, disorders of circadian rhythm might play a pivotal role in glucose metabolic disturbances, especially in terms of early adverse nutritional environments and the development of metabolic diseases in later life. In addition, as a peripheral clock, the gut microbiota has its own circadian rhythm that fluctuates with periodic feeding and has been widely recognized for its significant role in metabolism. In light of the important roles of the gut microbiota and circadian clock in metabolic health and their interconnected regulatory relationship, we propose that the "gut microbiota-circadian clock axis" might be a novel and crucial mechanism to decipher "metabolic memory." The "gut microbiota-circadian clock axis" is expected to facilitate the future development of a novel target for the prevention and intervention of diabetes during the early stage of life.

G Protein-Coupled Receptor Systems as Crucial Regulators of DNA Damage Response Processes

G protein-coupled receptors (GPCRs) and their associated proteins represent one of the most diverse cellular signaling systems involved in both physiological and pathophysiological processes. Aging represents perhaps the most complex biological process in humans and involves a progressive degradation of systemic integrity and physiological resilience. This is in part mediated by age-related aberrations in energy metabolism, mitochondrial function, protein folding and sorting, inflammatory activity and genomic stability. Indeed, an increased rate of unrepaired DNA damage is considered to be one of the 'hallmarks' of aging. Over the last two decades our appreciation of the complexity of GPCR signaling systems has expanded their functional signaling repertoire. One such example of this is the incipient role of GPCRs and GPCR-interacting proteins in DNA damage and repair mechanisms. Emerging data now suggest that GPCRs could function as stress sensors for intracellular damage, e.g., oxidative stress. Given this role of GPCRs in the DNA damage response process, coupled to the effective history of drug targeting of these receptors, this suggests that one important future activity of GPCR therapeutics is the rational control of DNA damage repair systems.

Lipid Metabolism Alteration by Endocrine Disruptors in Animal Models: An Overview

Exposure to potential Endocrine Disrupting Chemicals (EDCs) pose a documented risk to both wildlife and human health. Many studies so far described declining sperm counts, genital malformations, early puberty onset, highlighting the negative impact on reproduction caused by the exposure to many anthropogenic chemicals. In the last years, increasing evidence suggested that these compounds, other than altering reproduction, affect metabolism and induce the onset of obesity and metabolic disorders. According to the "environmental obesogens" hypothesis, evidence exists that exposure to potential EDCs during critical periods when adipocytes are differentiating, and organs are developing, can induce diseases that manifest later in the life. This review summarizes the effects occurring at the hepatic level in different animal models, describing morphological alterations and changes of molecular pathways elicited by the toxicant exposure. Results currently available demonstrated that these chemicals impair normal metabolic processes via interaction with members of the nuclear receptor superfamily, including steroid hormone receptors, thyroid hormone receptors, retinoid X receptors, peroxisome proliferator-activated receptors, liver X receptors, and farnesoid X receptors. In addition, novel results revealed that EDC exposure can either affect circadian rhythms as well as up-regulate the expression of signals belonging to the endocannabinoid system, in both cases leading to a remarkable increase of lipid accumulation. These results warrant further research and increase the interest toward the identification of new mechanisms for EDC metabolic alterations. The last part of this review article condenses recent evidences on the ability of potential EDCs to cause "transgenerational effects" by a single prenatal or early life exposure. On this regard, there is compelling evidence that epigenetic modifications link developmental environmental insults to adult disease susceptibility. This review will contribute to summarize the mechanisms underlying the insurgence of EDC-induced metabolic alterations as well as to build integrated strategies for their better management. In fact, despite the large number of results obtained so far, there is still a great demand for the development of frameworks that can integrate mechanistic and toxicological/epidemiological observations. This would increase legal and governmental institution awareness on this critical environmental issue responsible for negative consequences in both wild species and human health.