Targeting the liver clock improves fibrosis by restoring TGF-β signaling

Irisin attenuates liver fibrosis by regulating energy metabolism and HMGB1/β-catenin signaling in hepatic stellate cells

Liver fibrosis is characterized by excessive extracellular matrix accumulation during chronic liver disease progression. Hepatic stellate cell (HSC) activation involves metabolic reprogramming, while both HMGB1 and β-catenin pathways have been implicated in HSC activation and liver fibrosis progression. Given irisin's established role in metabolic regulation and emerging evidence of its anti-fibrotic properties, we investigated its effects on HSC activation and liver fibrosis, focusing on potential metabolic regulation through the HMGB1/β-catenin pathway. Using both in vitro HSC-T6 cell culture and in vivo CCl4-induced rat liver fibrosis model, we analyzed irisin's impact on HSC metabolism and fibrosis progression. Our results demonstrated that irisin dose-dependently suppressed HSC-T6 cell viability and glycolytic metabolism, significantly reducing ATP levels, glucose consumption, and lactate production at concentrations of 80-100 nmol/L. Irisin treatment markedly inhibited HSC-T6 cell proliferation and migration while inducing cellular senescence, as evidenced by increased H3K9me3, γ-H2AX, P16, and P21 expression. Mechanistically, irisin systematically downregulated key glycolytic enzymes (HK2, PFK1, PKM2, LDHA) and modulated the HMGB1/β-catenin pathway by reducing both cytoplasmic HMGB1 expression and β-catenin nuclear translocation. In the CCl4-induced rat model, irisin treatment significantly ameliorated liver fibrosis, as evidenced by reduced collagen deposition and α-SMA expression, while improving liver function indicators and decreasing serum fibrosis markers (HA, PIIIP, HMGB1), showing therapeutic effects comparable to colchicine. These findings reveal irisin's anti-fibrotic effects through metabolic regulation and HMGB1/β-catenin pathway modulation, suggesting its potential as a therapeutic agent for liver fibrosis.

Circadian clock regulation of myofibroblast fate

Fibrosis-related disorders represent an increasing medical and economic burden on a worldwide scale, accounting for one-third of all disease-related deaths with limited therapeutic options. As central mediators in fibrosis development, myofibroblasts have been gaining increasing attention in the last 20 years as potential targets for fibrosis attenuation and reversal. While various aspects of myofibroblast physiology have been proposed as treatment targets, many of these approaches have shown limited long-term efficacy so far. However, ongoing research is uncovering new potential strategies for targeting myofibroblast activity, offering hope for more effective treatments in the future. The circadian molecular clock is a feature of almost every cell in the human body that dictates the rhythmic nature of various aspects of human physiology and behavior in response to changes in the surrounding environment. The dysregulation of these rhythms with aging is considered to be one of the underlying reasons behind the development of multiple aging-related chronic disorders, with fibrotic tissue scarring being a common pathological complication among the majority of them. Myofibroblast dysregulation due to skewed circadian clockwork might significantly contribute to fibrotic scar persistence. In the current review, we highlight the role of the circadian clock in the context of myofibroblast activation and deactivation and examine its dysregulation as a driver of fibrogenesis.

Chronic Inflammation and Immune Dysregulation in Metabolic-Dysfunction-Associated Steatotic Liver Disease Progression: From Steatosis to Hepatocellular Carcinoma

Background/Objectives: Metabolic-dysfunction-associated steatotic liver disease (MASLD) progresses from hepatic steatosis to hepatocellular carcinoma (HCC) as a result of systemic immunometabolic dysfunction. This review summarizes the key roles of the innate and adaptive immune mechanisms driving hepatic injury, fibrogenesis, and carcinogenesis in MASLD. Methods: A comprehensive literature review was performed using PubMed to identify relevant published studies. Eligible articles included original research and clinical studies addressing immunological and metabolic mechanisms in MASLD, as well as emerging therapeutic strategies. Results: We highlight the roles of cytokine networks, the gut-liver axis, and immune cell reprogramming. Emerging therapeutic strategies, including cytokine inhibitors, anti-fibrotic agents, metabolic modulators, and nutraceuticals, offer several indications for attenuating MASLD progression and reducing the prevalence of extrahepatic manifestations. Conclusions: Given the heterogeneity of MASLD, personalized combination-based approaches targeting both inflammation and metabolic stress are essential for effective disease management and the prevention of systemic complications.

Circadian clock controlled glycolipid metabolism and its relevance to disease management

The circadian clock is a critical regulator of physiological rhythms, orchestrating metabolic processes to adapt to daily environmental changes. This review focuses on the intricate relationship between circadian regulation and glycolipid metabolism, with implications for metabolic diseases. Central and peripheral clocks coordinate the rhythmic expression of key enzymes and transporters, ensuring glycolipid homeostasis. Disruptions to these rhythms can result in metabolic disorders characterized by altered glucose utilization, insulin sensitivity, and lipid storage. The molecular mechanisms underlying these processes include transcriptional-translational feedback loops involving clock factors that regulate glycolipid metabolism. Emerging therapeutic strategies, such as pharmacological and dietary interventions, highlight the translational potential of circadian biology. This review underscores the importance of circadian rhythm maintenance for glycolipid metabolism and its role in preventing metabolic disorders. Further elucidation of the molecular mechanisms linking circadian regulation to glycolipid metabolism could pave the way for precision medicine approaches tailored to individual circadian profiles.

Dual signaling pathways of TGF-β superfamily cytokines in hepatocytes: balancing liver homeostasis and disease progression

The transforming growth factor-β (TGF-β) superfamily (TGF-β-SF) comprises over 30 cytokines, including TGF-β, activins/inhibins, bone morphogenetic proteins (BMPs), and growth differentiation factors (GDFs). These cytokines play critical roles in liver function and disease progression. Here, we discuss Smad-dependent (canonical) and non-Smad pathways activated by these cytokines in a hepatocellular context. We highlight the connection between the deregulation of these pathways or the balance between them and key hepatocellular processes (e.g., proliferation, apoptosis, and epithelial-mesenchymal transition (EMT)). We further discuss their contribution to various chronic liver conditions, such as metabolic dysfunction-associated steatotic liver disease (MASLD), metabolic dysfunction-associated steatohepatitis (MASH), and hepatocellular carcinoma (HCC). In MASLD and MASH, TGF-β signaling contributes to hepatocyte lipid accumulation, cell death and fibrosis progression through both Smad and non-Smad pathways. In HCC, TGF-β and other TGF-β-SF cytokines have a dual role, acting as tumor suppressors or promoters in early vs. advanced stages of tumor progression, respectively. Additionally, we review the involvement of non-Smad pathways in modulating hepatocyte responses to TGF-β-SF cytokines, particularly in the context of chronic liver diseases, as well as the interdependence with other key pathways (cholesterol metabolism, insulin resistance, oxidative stress and lipotoxicity) in MASLD/MASH pathogenesis. The perspectives and insights detailed in this review may assist in determining future research directions and therapeutic targets in liver conditions, including chronic liver diseases and cancer.

Circadian control of hepatic ischemia/reperfusion injury via HSD17B13-mediated autophagy in hepatocytes

BACKGROUND & AIMS

Studies have illustrated the role of circadian rhythms in hepatic ischemia/reperfusion injury (HIRI), but the mechanisms are poorly understood. Bmal1 plays a significant role in the circadian control of liver physiology and disease; however, its role in HIRI has not been investigated. Here, we aimed to explore the potential contribution of BMAL1 to HIRI.

METHODS

The impact of ischemia/reperfusion timing (Zeitgeber time [ZT]0 vs. ZT12) on liver damage was assessed in mice with Bmal1 specifically depleted in hepatocytes or myeloid cells. RNA sequencing and other techniques were employed to explore the underlying molecular mechanisms. Additionally, we investigated the role of HSD17B13, a lipid droplet-associated protein, in BMAL1-mediated circadian control of HIRI by utilizing global knockout, hepatocyte-specific knockdown, or hepatocyte-specific humanized HSD17B13 overexpression mouse models.

RESULTS

We found that initiating ischemia/reperfusion operations at ZT12 instead of ZT0 resulted in significantly more severe liver injury in wild-type mice. Bmal1 in hepatocytes, but not in myeloid cells, mediated this temporal difference. Mechanistically, BMAL1 regulates the diurnal oscillation of HIRI by directly controlling Hsd17b13 transcription via binding to E-box-like elements. Hepatocyte-specific knockdown of Hsd17b13 blunted the diurnal variation of HIRI and exacerbated ZT0 HIRI. Furthermore, depletion of the BMAL1/HSD17B13 axis may inhibit lipid degradation by blocking autophagy flux, contributing to lipid overload and exacerbating HIRI. Finally, we demonstrated that hepatocyte-specific overexpression of humanized HSD17B13 may confer protection during ZT0 HIRI but aggravate damage at ZT12.

CONCLUSIONS

Our study uncovers a pivotal role of hepatocyte BMAL1 in modulating circadian rhythms in HIRI via HSD17B13-mediated autophagy and offers a promising strategy for preventing and treating HIRI by targeting the BMAL1/HSD17B13 axis.

IMPACT AND IMPLICATIONS

This study unveils a pivotal role of the BMAL1/HSD17B13 axis in the circadian control of hepatic ischemia/reperfusion injury, providing new insights into the prevention and treatment of hepatic ischemia/reperfusion injury. The findings have scientific implications as they enhance our understanding of the circadian regulation of hepatic ischemia/reperfusion injury. Furthermore, clinically, this research offers opportunities for optimizing treatment strategies in hepatic ischemia/reperfusion injury by considering the timing of therapeutic interventions.

Notch1 siRNA and AMD3100 Ameliorate Metabolic Dysfunction-Associated Steatotic Liver Disease

Background and Objectives: As a key mechanism of metabolic dysfunction-associated steatotic liver disease (MASLD) pathogenesis, inflammation triggered by chronic liver injury and immune cells with macrophages enables MASLD to progress to an advanced stage with irreversible processes such as fibrosis, cell necrosis, and cancer in the liver. The complexity of MASLD, including crosstalk between multiple organs and the liver, makes developing a new drug for MASLD challenging, especially in single-drug therapy. It was reported that upregulation of Notch1 is closely associated with the function of pro-inflammatory macrophages. To leverage this signaling pathway in treating MASLD, we developed a combination therapy. Materials and Methods: We chose Notch1 siRNA (siNotch1) to block the Notch pathway so that phenotypic regulation and functional recovery can be achieved in macrophages, combining with small molecule drug AMD3100. AMD3100 can cut off the migration of inflammatory cells to the liver to impede the development of inflammation and inhibit the CXCL12/CXCR4 biological axis in liver fibrosis to protect against the activation of HSCs. Then, we investigated the efficacy of the combination therapy on resolving inflammation and MASLD. Results: We demonstrated that in liver cells, siNotch1 combined with AMD3100 not only directly modulated macrophages by downregulating multiple pathways downstream of Notch, exerting anti-inflammatory, anti-migration, and switch of macrophage phenotype, but also modulated macrophage phenotypes through inhibiting NET release. The restored macrophages further regulate HSC and neutrophils. In in vivo pharmacodynamic studies, combination therapy exhibits a superior therapeutical effect over monotherapy in MASLD models. Conclusions: These results constitute an siRNA therapeutical approach combined with a small molecule drug against inflammation and liver injury in MASLD, offering a promising therapeutic intervention for MASLD.

Topic "Signaling Pathways in Liver Disease"

Liver diseases pose a significant global health challenge, affecting millions of individuals and resulting in substantial morbidity and mortality [...].

Imeglimin Halts Liver Damage by Improving Mitochondrial Dysfunction in a Nondiabetic Male Mouse Model of Metabolic Dysfunction-Associated Steatohepatitis

Imeglimin promotes glucose-stimulated insulin secretion in the pancreas in a glucose-dependent manner and inhibits gluconeogenesis in the liver. Meanwhile, imeglimin can improve mitochondrial function in hepatocytes. We used a nondiabetic metabolic dysfunction-associated steatohepatitis (MASH) model to examine the effects of imeglimin on MASH independent of its glucose-lowering action. Mice fed a choline-deficient high-fat diet (CDA-HFD) were orally administered imeglimin (100 and 200 mg/kg twice daily), and MASH pathophysiology was evaluated after 8 weeks. Moreover, an in vitro study investigated the effects of imeglimin on palmitic acid (PA)-stimulated lipid accumulation, apoptosis, and mitochondrial dysfunction in human hepatocytes. CDA-HFD-fed mice showed hepatic steatosis, inflammation, and fibrosis without hyperglycemia. Imeglimin reduced hepatic steatosis in response to increased expression of β-oxidation-related markers. Imeglimin reduced reactive oxygen species accumulation and increased mitochondrial biogenesis in CDA-HFD-fed mice. Consequently, imeglimin suppressed hepatocyte apoptosis and decreased macrophage infiltration with reduced proinflammatory cytokine expression, suppressing hepatic fibrosis development. PA-stimulated hepatocytes induced lipogenesis, inflammatory cytokine production, and apoptosis, which were significantly suppressed by imeglimin. In mitochondrial function, imeglimin improved PA-stimulated decrease in mitochondrial membrane potential, mitochondrial complexes activity, oxygen consumption rate, and mitochondrial biogenesis marker expression. In conclusion, imeglimin could contribute to prevention of MASH progression through suppressing de novo lipogenesis and enhancing fatty acid oxidation.