Circadian Clock and Liver Cancer

Identification of BMAL1-Regulated circadian genes in mouse liver and their potential association with hepatocellular carcinoma: Gys2 and Upp2 as promising candidates

Identification and functional analysis of key genes regulated by the circadian clock system will provide a comprehensive understanding of the underlying mechanisms through which circadian clock disruption impairs the health of living organisms. The initial phase involved bioinformatics analysis, drawing insights from three RNA-seq datasets (GSE184303, GSE114400, and GSE199061) derived from wild-type mouse liver tissues, which encompassed six distinct time points across a day. As expected, 536 overlapping genes exhibiting rhythmic expression patterns were identified. By intersecting these genes with differentially expressed genes (DEGs) originating from liver RNA-seq data at two representative time points (circadian time, CT: CT2 and CT14) in global Bmal1 knockout mice (Bmal1-/-), hepatocyte-specific Bmal1 knockout mice (L-Bmal1-/-), and their corresponding control groups, 80 genes potentially regulated by BMAL1 (referred to as BMAL1-regulated genes, BRGs) were identified. These genes were significantly enriched in glycolipid metabolism, immune response, and tumorigenesis pathways. Eight BRGs (Nr1d1, Cry1, Gys2, Homer2, Serpina6, Slc2a2, Nmrk1, and Upp2) were selected to validate their expression patterns in both control and L-Bmal1-/- mice livers over 24 h. Real-time quantitative polymerase chain reaction results demonstrated a comprehensive loss of rhythmic expression patterns in the eight selected BRGs in L-Bmal1-/- mice, in contrast to the discernible rhythmic patterns observed in the livers of control mice. Additionally, significant reductions in the expression levels of these selected BRGs, excluding Cry1, were also observed in L-Bmal1-/- mice livers. Chromatin immunoprecipitation (ChIP)-seq (GSE13505 and GSE39860) and JASPAR analyses validated the rhythmic binding of BMAL1 to the promoter and intron regions of these genes. Moreover, the progression of conditions, from basic steatosis to non-alcoholic fatty liver disease, and eventual malignancy, demonstrated a continuous gradual decline in Bmal1 transcripts in the human liver. Combining the aforementioned BRGs with DEGs derived from human liver cancer datasets identified Gys2 and Upp2 as potential node genes bridging the circadian clock system and hepatocellular carcinoma (HCC). In addition, CCK8 and wound healing assays demonstrated that the overexpression of human GYS2 and UPP2 proteins inhibited the proliferation and migration of HepG2 cells, accompanied by elevated expression of p53, a tumor suppressor protein. In summary, this study systematically identified rhythmic genes in the mouse liver, and a subset of circadian genes potentially regulated by BMAL1. Two circadian genes, Gys2 and Upp2, have been proposed and validated as potential candidates for advancing the prevention and treatment of HCC.

Multi-omics and single-cell sequencing analyses reveal the potential significance of circadian pathways in cancer therapy

BACKGROUND

Circadian rhythm disturbance is an independent risk factor for cancer. However, few studies have been reported on circadian rhythm related genes (CRGs) in cancer, so it is important to further explore the impact of CRGs in pan-cancer.

RESEARCH DESIGN AND METHODS

The Cancer Genome Atlas database was used to collect cancer-related data such as copy number variation, single nucleotide variants, methylation, and survival differences. Immunohistochemistry (IHC) was used to verify the expression of circadian rhythm hub genes. The circadian pathway scores (CRS) were calculated using single-sample gene enrichment analysis. TIMER and GEPIA databases were used for immune-cell integration and assessment. Single-cell sequencing data was used to evaluate the abundance of CRS in tumor microenvironment cells.

RESULTS

In this study, we found that the expression of circadian pathway varies between tumors. CSNK1E was significantly up-regulated in most tumors and CRY2 was significantly down-regulated in most tumors. The protein interaction network suggested CRY2 as the core gene and IHC verified its significant low expression in KIRC. In addition, CRGs were found to be protective factors in most tumors and have the potential to act as specific immune markers in different tumors. CRS was significantly lower in abundance in most tumors. CRS was significantly associated with overall survival in tumor patients and associated with the expression of many immune cells in the tumor immune microenvironment. CRS is significantly associated with tumor mutational burden and microsatellite instability scores in most tumors and may serve as a potential immunotherapeutic marker.

CONCLUSIONS

The circadian rhythm pathway may be a breakthrough point in regulating the tumor microenvironment meanwhile a suitable immunotherapy method in the future.

Diurnal circadian clock gene expression is altered in models of genetic and acquired epilepsy

OBJECTIVES

Growing evidence demonstrates a relationship between epilepsy and the circadian system. However, relatively little is known about circadian function in disease states, such as epilepsy. This study aimed to characterize brain and peripheral core circadian clock gene expression in rat models of genetic and acquired epilepsy.

METHODS

For the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) study, we used 40 GAERS and 40 non-epileptic control (NEC) rats. For the kainic acid status epilepticus (KASE) study, we used 40 KASE and 40 sham rats. Rats were housed in a 7 am:7 pm light-dark cycle. Hypothalamus, hippocampus, liver, and small intestine samples were collected every 3 h throughout the light period. We then assessed core diurnal clock gene expression of per1, cry1, clock, and bmal1.

RESULTS

In the GAERS rats, all tissues exhibited significant changes in clock gene expression (P < 0.05) when compared to NEC. In the KASE rats, there were fewer effects of the epileptic condition in the hypothalamus, hippocampus, or small intestine (P > 0.05) compared with shams.

SIGNIFICANCE

These results indicate marked diurnal disruption to core circadian clock gene expression in rats with both generalized and focal chronic epilepsy. This could contribute to epileptic symptomology and implicate the circadian system as a viable target for future treatments.

Circadian control of ConA-induced acute liver injury and inflammatory response via Bmal1 regulation of Junb

Background & Aims

Circadian rhythms play significant roles in immune responses, and many inflammatory processes in liver diseases are associated with malfunctioning molecular clocks. However, the significance of the circadian clock in autoimmune hepatitis (AIH), which is characterised by immune-mediated hepatocyte destruction and extensive inflammatory cytokine production, remains unclear.

Methods

We tested the difference in susceptibility to the immune-mediated liver injury induced by concanavalin A (ConA) at various time points throughout a day in mice and analysed the effects of global, hepatocyte, or myeloid cell deletion of the core clock gene, Bmal1 (basic helix-loop-helix ARNT-like 1), on liver injury and inflammatory responses. Multiple molecular biology techniques and mice with macrophage-specific knockdown of Junb, a Bmal1 target gene, were used to investigate the involvement of Junb in the circadian control of ConA-induced hepatitis.

Results

The susceptibility to ConA-induced liver injury is highly dependent on the timing of ConA injection. The treatment at Zeitgeber time 0 (lights on) triggers the highest mortality as well as the severest liver injury and inflammatory responses. Further study revealed that this timing effect was driven by macrophage, but not hepatocyte, Bmal1. Mechanistically, Bmal1 controls the diurnal variation of ConA-induced hepatitis by directly regulating the circadian transcription of Junb and promoting M1 macrophage activation. Inhibition of Junb in macrophages blunts the administration time-dependent effect of ConA and attenuates liver injury. Moreover, we demonstrated that Junb promotes macrophage inflammation by regulating AKT and extracellular signal-regulated kinase (ERK) signalling pathways.

Conclusions

Our findings uncover a critical role of the Bmal1-Junb-AKT/ERK axis in the circadian control of ConA-induced hepatitis and provide new insights into the prevention and treatment of AIH.

Impact and Implications

This study unveils a critical role of the Bmal1-Junb-AKT/ERK axis in the circadian control of ConA-induced liver injury, providing new insights into the prevention and treatment of immune-mediated hepatitis, including autoimmune hepatitis (AIH). The findings have scientific implications as they enhance our understanding of the circadian regulation of immune responses in liver diseases. Furthermore, clinically, this research offers opportunities for optimising treatment strategies in immune-mediated hepatitis by considering the timing of therapeutic interventions.

A circadian clock gene-related signature for predicting prognosis and its association with sorafenib response in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC), one of the highest causes of cancer-associated death, has effective treatments, especially for patients with advanced HCC. Circadian rhythm participates in several important physiological functions, and its chronic disruption results in many disordered diseases, including cancer. However, the role of circadian rhythm in the overall survival (OS) of patients with HCC remains unclear.

Methods

We investigated the expression, copy number variation (CNV), and mutation profiles of core circadian clock genes in normal and tumor tissues. We developed and validated a messenger RNA signature (mRNASig) based on prognostic circadian clock genes. A set of bioinformatic tools were applied for functional annotation and tumor-associated microenvironment (TME) analysis.

Results

Core circadian clock genes were disrupted in terms of the transcription and CNV of HCC samples. The mRNASig, including NPAS2, NR1D1, PER1, RORC, and TIMELESS, was constructed. We divided patients with HCC into high-risk group and low-risk group based on the median value of the risk score. The high-risk group had a poorer prognosis than the low-risk group. The high-risk group was associated with malignant processes (e.g., proliferation, oncogenic pathway, DNA repair), metabolism, and tumor mutational burden (TMB). Surprisingly, the low-risk group was associated with enriched angiogenesis and was linked to enhanced response to sorafenib. Moreover, the high-risk group showed poor infiltration of CD8 T cells and natural killer cells accompanied by higher expression of CTLA4, PDCD1, TIGIT, and TIM3. Additionally, the mRNASig was associated with TMB.

Conclusions

The mRNASig based on core circadian clock genes is a potential prognostic signature and therapeutic strategy and is significantly associated with the malignant biology of HCC.

Timing Matters: The Interplay between Early Mealtime, Circadian Rhythms, Gene Expression, Circadian Hormones, and Metabolism-A Narrative Review

Achieving synchronization between the central and peripheral body clocks is essential for ensuring optimal metabolic function. Meal timing is an emerging field of research that investigates the influence of eating patterns on our circadian rhythm, metabolism, and overall health. This narrative review examines the relationship between meal timing, circadian rhythm, clock genes, circadian hormones, and metabolic function. It analyzes the existing literature and experimental data to explore the connection between mealtime, circadian rhythms, and metabolic processes. The available evidence highlights the importance of aligning mealtime with the body's natural rhythms to promote metabolic health and prevent metabolic disorders. Specifically, studies show that consuming meals later in the day is associated with an elevated prevalence of metabolic disorders, while early time-restricted eating, such as having an early breakfast and an earlier dinner, improves levels of glucose in the blood and substrate oxidation. Circadian hormones, including cortisol and melatonin, interact with mealtimes and play vital roles in regulating metabolic processes. Cortisol, aligned with dawn in diurnal mammals, activates energy reserves, stimulates appetite, influences clock gene expression, and synchronizes peripheral clocks. Consuming meals during periods of elevated melatonin levels, specifically during the circadian night, has been correlated with potential implications for glucose tolerance. Understanding the mechanisms of central and peripheral clock synchronization, including genetics, interactions with chronotype, sleep duration, and hormonal changes, provides valuable insights for optimizing dietary strategies and timing. This knowledge contributes to improved overall health and well-being by aligning mealtime with the body's natural circadian rhythm.

The role of the gut microbiome in the development of hepatobiliary cancers

Hepatobiliary cancers, including hepatocellular carcinoma and cancers of the biliary tract, share high mortality and rising incidence rates. They may also share several risk factors related to unhealthy western-type dietary and lifestyle patterns as well as increasing body weights and rates of obesity. Recent data also suggest a role for the gut microbiome in the development of hepatobiliary cancer and other liver pathologies. The gut microbiome and the liver interact bidirectionally through the "gut-liver axis," which describes the interactive relationship between the gut, its microbiota, and the liver. Here, we review the gut-liver interactions within the context of hepatobiliary carcinogenesis by outlining the experimental and observational evidence for the roles of gut microbiome dysbiosis, reduced gut barrier function, and exposure to inflammatory compounds as well as metabolic dysfunction as contributors to hepatobiliary cancer development. We also outline the latest findings regarding the impact of dietary and lifestyle factors on liver pathologies as mediated by the gut microbiome. Finally, we highlight some emerging gut microbiome editing techniques currently being investigated in the context of hepatobiliary diseases. Although much work remains to be done in determining the relationships between the gut microbiome and hepatobiliary cancers, emerging mechanistic insights are informing treatments, such as potential microbiota manipulation strategies and guiding public health advice on dietary/lifestyle patterns for the prevention of these lethal tumors.

Construction and verification of a novel circadian clock related long non-coding RNA model and prediction of treatment for survival prognosis in patients with hepatocellular carcinoma

Circadian clock genes are significant in the occurrence and development of HCC and long-non coding RNAs (lncRNAs) are closely related to HCC progression. In this study, we aimed to establish a prognostic risk model for HCC. Circadian clock-related lncRNAs expressed in HCC were extracted from The Cancer Genome Atlas. A nomogram was established to predict individual survival rate. Biological processes enriched for risk model transcripts were investigated by Gene Set Enrichment Analysis. Further, we evaluated the relationship between risk score and immune-checkpoint inhibitor-related gene expression level. The Genomics of Drug Sensitivity in Cancer (GDSC) database was used to assess the sensitivity of tumors in high- and low-risk score groups to different drugs. A total of 11 circadian clock-related lncRNAs were included in multi-Cox proportional hazards model analysis to establish a risk model. Univariate and multivariate Cox regression analysis showed that the risk model was an independent risk factor in HCC. The risk model was a significantly associated with the immune signature. Further GDSC analysis indicated that patients in each risk score group may be sensitive to different anti-cancer drugs. QRT-PCR analysis results showed that C012073.1, PRRT3-AS1, TMCC1-AS1, LINC01138, MKLN1-AS, KDM4A-AS1, AL031985.3, POLH-AS1, LINC01224, and AC099850.3 were more highly expressed in Huh-7 and HepG2, compared to LO2, while AC008549.1 were lower expressed. Our work established a prognostic model for HCC. Risk score analysis indicated that the model is significantly associated with modulation tumor immunity and could be used to guide more effective therapeutic strategies in the future.

BMAL1 Regulates Glucokinase Expression Through E-Box Elements In Vitro

The organization of a circadian system includes an endogenous pacemaker system, input pathways for environmental synchronizing (entraining) stimuli, and output pathways through which the clock regulates physiological and behavioral processes, for example, the glucose-sensing mechanism in the liver. The liver is the central regulator of metabolism and one of our peripherals clocks. In mammals, central to this pacemaker are the transcription factors Circadian Locomotor Output Cycles Kaput (CLOCK) and BMAL1 (Brain and Muscle ARNT-Like 1). BMAL1 dimerizes with CLOCK, and this heterodimer then binds to the E-box promoter elements (CACGTG) present in clock and clock-controlled genes (CCGs). However, we are just beginning to understand how output pathways and regulatory mechanisms of CCGs are involved in rhythmic physiological processes. Glucokinase (GCK) is a fundamental enzyme in glucose homeostasis, catalyzing the high Km phosphorylation of glucose and allowing its storage. Moreover, gck is a dependent circadian gene. This study aims to determine the contribution of clock genes to hepatic gck expression and to define the specific role of E-box sequences on the circadian regulation of hepatic gck. Results showed that gck expression follows a circadian rhythm in rat hepatocytes in vitro. Accordingly, bmal1 expression induces the glucokinase circadian rhythmic expression in hepatocytes and the analysis of human and rat gck promoters, indicating the presence of E-box regions. Moreover, the basal activity of gck promoter was increased by clock/bmal1 co-transfection but inhibited by Period1/Period2 (per1/per2) co-transfection. Thus, the data suggest that the clock proteins tightly regulate the transcriptional activity of the gck promoter.

The interplay between circadian clock and viral infections: A molecular perspective

The circadian clock influences almost every aspect of mammalian behavioral, physiological and metabolic processes. Being a hierarchical network, the circadian clock is driven by the central clock in the brain and is composed of several peripheral tissue-specific clocks. It orchestrates and synchronizes the daily oscillations of biological processes to the environment. Several pathological events are influenced by time and seasonal variations and as such implicate the clock in pathogenesis mechanisms. In context with viral infections, circadian rhythmicity is closely associated with host susceptibility, disease severity, and pharmacokinetics and efficacies of antivirals and vaccines. Leveraging the circadian molecular mechanism insights has increased our understanding of clock infection biology and proposes new avenues for viral diagnostics and therapeutics. In this chapter, we address the molecular interplay between the circadian clock and viral infections and discuss the importance of chronotherapy as a complementary approach to conventional medicines, emphasizing the significance of virus-clock studies.

Is Fasting Good When One Is at Risk of Liver Cancer?

Hepatocellular carcinoma (HCC), one of the leading causes of cancer-related deaths worldwide, is a multistep process that usually develops in the background of cirrhosis, but also in a non-cirrhotic state in patients with non-alcoholic fatty liver disease (NAFLD) or viral hepatis. Emerging evidence suggests that intermittent fasting can reduce the risk of cancer development and could improve response and tolerance to treatment through the metabolic and hormonal adaptations induced by the low energy availability that finally impairs cancer cells’ adaptability, survival and growth. The current review will outline the beneficial effects of fasting in NAFLD/NASH patients and the possible mechanisms that can prevent HCC development, including circadian clock re-synchronization, with a special focus on the possibility of applying this dietary intervention to cirrhotic patients.

Circular RNA hsa_circ_0062682 Binds to YBX1 and Promotes Oncogenesis in Hepatocellular Carcinoma

Simple Summary

Circular RNA (circRNA) have a role in carcinogenesis in different cancers, also in hepatocellular carcinoma (HCC). The transcriptome analyses of HCC tumours identified an upregulated circRNA hsa_circ_0062682. We show that this circRNA affects several aspects of oncogenesis, which are cell proliferation, migration, and invasion. Using transcriptome analyses we identified modulated signalling pathways and transcription factors, confirming the observed phenotype in cells. We identified Y-box-binding protein 1 (YBX1), a known oncogene and RNA-binding protein, as a binding partner, which was in line with transcriptome analyses. We also identified a cell-specific response to sorafenib after circRNA modulation, which is in line with a heterogeneous molecular pathology of HCC subtypes.

Abstract

Circular RNAs (circRNAs) have been shown to play an important role in the pathogenesis of hepatocellular carcinoma (HCC). By implementing available transcriptomic analyses of HCC patients, we identified an upregulated circRNA hsa_circ_0062682. Stable perturbations of hsa_circ_0062682 in Huh-7 and SNU-449 cell lines influenced colony formation, migration, cell proliferation, sorafenib sensitivity, and additionally induced morphological changes in cell lines, indicating an important role of hsa_circ_0062682 in oncogenesis. Pathway enrichment analysis and gene set enrichment analysis of the transcriptome data from hsa_circ_0062682 knockdown explained the observed phenotypes and exposed transcription factors E2F1, Sp1, HIF-1α, and NFκB1 as potential downstream targets. Biotinylated oligonucleotide pulldown combined with proteomic analyses identified protein interaction partners of which YBX1, a known oncogene, was confirmed by RNA immunoprecipitation. Furthermore, we discovered a complex cell-type-specific phenotype in response to the oncogenic potential of hsa_circ_0062682. This finding is in line with different classes of HCC tumours, and more studies are needed to shed a light on the molecular complexity of liver cancer.

Obesity, cancer risk, and time-restricted eating

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

Circadian Rhythm Dysregulation and Leukemia Development: The Role of Clock Genes as Promising Biomarkers

The circadian clock (CC) is a daily system that regulates the oscillations of physiological processes and can respond to the external environment in order to maintain internal homeostasis. For the functioning of the CC, the clock genes (CG) act in different metabolic pathways through the clock-controlled genes (CCG), providing cellular regulation. The CC’s interruption can result in the development of different diseases, such as neurodegenerative and metabolic disorders, as well as cancer. Leukemias correspond to a group of malignancies of the blood and bone marrow that occur when alterations in normal cellular regulatory processes cause the uncontrolled proliferation of hematopoietic stem cells. This review aimed to associate a deregulated CC with the manifestation of leukemia, looking for possible pathways involving CG and their possible role as leukemic biomarkers.

An Analysis of Microwave Ablation Parameters for Treatment of Liver Tumors from the 3D-IRCADb-01 Database

Simulation techniques are powerful tools for determining the optimal conditions necessary for microwave ablation to be efficient and safe for treating liver tumors. Owing to the complexity and computational resource consumption, most of the existing numerical models are two-dimensional axisymmetric models that emulate actual three-dimensional cancers and the surrounding tissue, which is often far from reality. Different tumor shapes and sizes require different input powers and ablation times to ensure the preservation of healthy tissues that can be determined only by the full three-dimensional simulations. This study aimed to tailor microwave ablation therapeutic conditions for complete tumor ablation with an adequate safety margin, while avoiding injury to the surrounding healthy tissue. Three-dimensional simulations were performed for a multi-slot microwave antenna immersed in two tumors obtained from the 3D-IRCADb-01 liver tumors database. The temperature dependence of the dielectric and thermal properties of healthy and tumoral liver tissues, blood perfusion, and water content are crucial for calculating the correct ablation time and, thereby, the correct ablation process. The developed three-dimensional simulation model may help practitioners in planning patient-individual procedures by determining the optimal input power and duration of the ablation process for the actual shape of the tumor. With proper input power, necrotic tissue is placed mainly in the tumor, and only a small amount of surrounding tissue is damaged.

The role of REV-ERB in NASH

REV-ERBs are atypical nuclear receptors as they function as ligand-regulated transcriptional repressors. The natural ligand for the REV-ERBs (REV-ERBα and REV-ERBβ) is heme, and heme-binding results in recruitment of transcriptional corepressor proteins such as N-CoR that mediates repression of REV-ERB target genes. These two receptors regulate a large range of physiological processes including several important in the pathophysiology of non-alcoholic steatohepatitis (NASH). These include carbohydrate and lipid metabolism as well as inflammatory pathways. A number of synthetic REV-ERB agonists have been developed as chemical tools and they show efficacy in animal models of NASH. Here, we will review the functions of REV-ERB with regard to their relevance to NASH as well as the potential to target REV-ERB for treatment of this disease.

On Efficacy of Microwave Ablation in the Thermal Treatment of an Early-Stage Hepatocellular Carcinoma

Microwave ablation at 2.45 GHz is gaining popularity as an alternative therapy to hepatic resection with a higher overall survival rate than external beam radiation therapy and proton beam therapy. It also offers better long-term recurrence-free overall survival when compared with radiofrequency ablation. To improve the design and optimization of microwave ablation procedures, numerical models can provide crucial information. A three-dimensional model of the antenna and targeted tissue without homogeneity assumptions are the most realistic representation of the physical problem. Due to complexity and computational resources consumption, most of the existing numerical studies are based on using two-dimensional axisymmetric models to emulate actual three-dimensional cancers and surrounding tissue, which is often far from reality. The main goal of this study is to develop a fully three-dimensional model of a multislot microwave antenna immersed into liver tissue affected by early-stage hepatocellular carcinoma. The geometry of the tumor is taken from the 3D-IRCADb-01 liver tumors database. Simulations were performed involving the temperature dependence of the blood perfusion, dielectric and thermal properties of both healthy and tumoral liver tissues. The water content changes during the ablation process are also included. The optimal values of the input power and the ablation time are determined to ensure complete treatment of the tumor with minimal damage to the healthy tissue. It was found that a multislot antenna is designed to create predictable, large, spherical zones of the ablation that are not influenced by varying tissue environments. The obtained results may be useful for determining optimal conditions necessary for microwave ablation to be as effective as possible for treating early-stage hepatocellular carcinoma, with minimized invasiveness and collateral damages.

Nuclear receptors: a bridge linking the gut microbiome and the host

Background

The gut microbiome is the totality of microorganisms, bacteria, viruses, protozoa, and fungi within the gastrointestinal tract. The gut microbiome plays key roles in various physiological and pathological processes through regulating varieties of metabolic factors such as short-chain fatty acids, bile acids and amino acids. Nuclear receptors, as metabolic mediators, act as a series of intermediates between the microbiome and the host and help the microbiome regulate diverse processes in the host. Recently, nuclear receptors such as farnesoid X receptor, peroxisome proliferator-activated receptors, aryl hydrocarbon receptor and vitamin D receptor have been identified as key regulators of the microbiome-host crosstalk. These nuclear receptors regulate metabolic processes, immune activity, autophagy, non-alcoholic and alcoholic fatty liver disease, inflammatory bowel disease, cancer, obesity, and type-2 diabetes.

Conclusion

In this review, we have summarized the functions of the nuclear receptors in the gut microbiome-host axis in different physiological and pathological conditions, indicating that the nuclear receptors may be the good targets for treatment of different diseases through the crosstalk with the gut microbiome.