Mst1 regulates hepatic lipid metabolism by inhibiting Sirt1 ubiquitination in mice

Mammalian Ste20-like kinase 1 regulates AMPK to mitigate the progression of non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic steatohepatitis (NASH) progression is strongly associated with deteriorating hepatic function, primarily driven by free cholesterol (FC) accumulation-induced lipotoxicity. Emerging evidence highlights the regulatory role of mammalian Ste20-like kinase 1 (MST1) in modulating intrahepatic lipid homeostasis, suggesting its therapeutic potential for non-alcoholic fatty liver disease (NAFLD) management. This investigation seeks to elucidate the pathophysiological mechanisms through which MST1 modulates NASH progression.

METHODS

The experimental design employed two murine genetic models-wild-type (WT) controls and MST1-knockout (MST1-KO) specimens-subjected to a nutritionally modified Western diet (WD) enriched with saturated fats, simple carbohydrates, and dietary cholesterol to induce non-alcoholic steatohepatitis (NASH) pathogenesis. Lentiviral transduction techniques facilitated targeted MST1 overexpression in WT animals maintained on this dietary regimen. Parallel in vitro investigations utilized HepG2 hepatocyte cultures exposed to free fatty acid (FFA) cocktails comprising palmitic and oleic acids, coupled with CRISPR-mediated MST1 suppression and complementary gain-of-function manipulations to delineate molecular mechanisms.

RESULTS

NASH triggers hepatic sterol biosynthesis activation, resulting in pathological FC overload concurrent with MST1 transcriptional suppression. Genetic ablation of MST1 amplifies intrahepatic FC retention and potentiates histopathological inflammation, while MST1 reconstitution mitigates steatotic FC deposition and attenuates inflammatory cascades. Mechanistic profiling revealed MST1-mediated AMPKα phosphorylation at Thr172, which suppresses cholesterogenic enzyme expression via sterol regulatory element-binding transcription factor 2 (SREBP2) axis modulation. This phosphorylation cascade demonstrates dose-dependent inhibition of HMGCR activity, resolving FC-induced hepatotoxicity. Crucially, MST1 orchestrates AMPK/SREBP2 crosstalk to maintain sterol homeostasis, with knockout models exhibiting 67% elevated SREBP2 nuclear translocation compared to controls.

CONCLUSIONS

The regulatory axis involving MST1-mediated AMPK phosphorylation emerges as a promising therapeutic modality for modulating hepatic sterol metabolism. It demonstrates significant potential in arresting the progression of inflammatory cascades and extracellular matrix remodeling characteristic of NASH pathogenesis. Mechanistic studies confirm that this phosphorylation cascade effectively suppresses de novo lipogenesis while enhancing cholesterol efflux capacity, thereby establishing a dual-target strategy against both metabolic dysfunction and fibrotic transformation in preclinical models.

Phosphorylation of an RNA-Binding Protein Rck/Me31b by Hippo Is Essential for Adipose Tissue Aging

The metazoan lifespan is determined in part by a complex signaling network that regulates energy metabolism and stress responses. Key signaling hubs in this network include insulin/IGF-1, AMPK, mTOR, and sirtuins. The Hippo/Mammalian Ste20-like Kinase1 (MST1) pathway has been reported to maintain lifespan in Caenorhabditis elegans, but its role has not been studied in higher metazoans. In this study, we report that overexpression of Hpo, the MST1 homolog in Drosophila melanogaster, decreased lifespan with concomitant changes in lipid metabolism and aging-associated gene expression, while RNAi Hpo depletion increased lifespan. These effects were mediated primarily by Hpo-induced transcriptional activation of the RNA-binding protein maternal expression at 31B (Me31b)/RCK, resulting in stabilization of mRNA-encoding a lipolytic hormone, Akh. In mouse adipocytes, Hpo/Mst1 mediated adipocyte differentiation, phosphorylation of RNA-binding proteins such as Rck, decapping MRNA 2 (Dcp2), enhancer Of MRNA decapping 3 (Edc3), nucleolin (NCL), and glucagon mRNA stability by interacting with Rck. Decreased lifespan in Hpo-overexpressing Drosophila lines required expression of Me31b, but not DCP2, which was potentially mediated by recovering expression of lipid metabolic genes and formation of lipid droplets. Taken together, our findings suggest that Hpo/Mst1 plays a conserved role in longevity by regulating adipogenesis and fatty acid metabolism.

Molecular mechanisms in liver repair and regeneration: from physiology to therapeutics

Liver repair and regeneration are crucial physiological responses to hepatic injury and are orchestrated through intricate cellular and molecular networks. This review systematically delineates advancements in the field, emphasizing the essential roles played by diverse liver cell types. Their coordinated actions, supported by complex crosstalk within the liver microenvironment, are pivotal to enhancing regenerative outcomes. Recent molecular investigations have elucidated key signaling pathways involved in liver injury and regeneration. Viewed through the lens of metabolic reprogramming, these pathways highlight how shifts in glucose, lipid, and amino acid metabolism support the cellular functions essential for liver repair and regeneration. An analysis of regenerative variability across pathological states reveals how disease conditions influence these dynamics, guiding the development of novel therapeutic strategies and advanced techniques to enhance liver repair and regeneration. Bridging laboratory findings with practical applications, recent clinical trials highlight the potential of optimizing liver regeneration strategies. These trials offer valuable insights into the effectiveness of novel therapies and underscore significant progress in translational research. In conclusion, this review intricately links molecular insights to therapeutic frontiers, systematically charting the trajectory from fundamental physiological mechanisms to innovative clinical applications in liver repair and regeneration.

Mechanism and therapeutic potential of hippo signaling pathway in type 2 diabetes and its complications

Loss of pancreatic islet cell mass and function is one of the most important factors in the development of type 2 diabetes mellitus, and hyperglycemia-induced lesions in other organs are also associated with apoptosis or hyperproliferation of the corresponding tissue cells. The Hippo signaling pathway is a key signal in the regulation of cell growth, proliferation and apoptosis, which has been shown to play an important role in the regulation of diabetes mellitus and its complications. Excessive activation of the Hippo signaling pathway under high glucose conditions triggered apoptosis and decreased insulin secretion in pancreatic islet cells, while dysregulation of the Hippo signaling pathway in the cells of other organ tissues led to proliferation or apoptosis and promoted tissue fibrosis, which aggravated the progression of diabetes mellitus and its complications. This article reviews the mechanisms of Hippo signaling, its individual and reciprocal regulation in diabetic pancreatic pathology, and its emerging role in the pathophysiology of diabetic complications. Potential therapeutics for diabetes mellitus that have been shown to target the Hippo signaling pathway are also summarized to provide information for the clinical management of type 2 diabetes mellitus.

Regulation of Hippo-YAP1/TAZ pathway in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become the most prevalent chronic liver disease worldwide, but effective treatments are still lacking. Metabolic disorders such as iron overload, glycolysis, insulin resistance, lipid dysregulation, and glutaminolysis are found to induce liver senescence and ferroptosis, which are hot topics in the research of MASLD. Recent studies have shown that Hippo-YAP1/TAZ pathway is involved in the regulations of metabolism disorders, senescence, ferroptosis, inflammation, and fibrosis in MASLD, but their complex connections and contrast roles are also reported. In addition, therapeutics based on the Hippo-YAP1/TAZ pathway hold promising for MASLD treatment. In this review, we highlight the regulation and molecular mechanism of the Hippo-YAP1/TAZ pathway in MASLD and summarize potential therapeutic strategies for MASLD by regulating Hippo-YAP1/TAZ pathway.

Ubiquitination and Metabolic Disease

The increasing incidence of metabolic diseases, including obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic fatty liver disease (NAFLD), in the past decade is a serious concern worldwide. Disruption of cellular protein homeostasis has been considered as a crucial contributor to the pathogenesis of metabolic diseases. To maintain protein homeostasis, cells have evolved multiple dynamic and self-regulating quality control processes to adapt new environmental conditions and prevent prolonged damage. Among them, the ubiquitin proteasome system (UPS), the primary proteolytic pathway for degradation of aberrant proteins via ubiquitination, has an essential role in maintaining cellular homeostasis in response to intracellular stress. Correspondingly, accumulating evidences have shown that dysregulation of ubiquitination can aggravate various metabolic derangements in many tissues, including the liver, skeletal muscle, pancreas, and adipose tissue, and is involved in the initiation and progression of diverse metabolic diseases. In this part, we will summarize the role of ubiquitination in the pathogenesis of metabolic diseases, including obesity, T2DM and NAFLD, and discuss its potential as a therapeutic target.

Biological Role and Related Natural Products of SIRT1 in Nonalcoholic Fatty Liver

Non-alcoholic fatty liver disease(NAFLD) is an umbrella term for a range of diseases ranging from hepatic fat accumulation and steatosis to non-alcoholic steatohepatitis (NASH) in the absence of excessive alcohol consumption and other definite liver damage factors. The incidence of NAFLD has increased significantly in recent years and will continue to grow in the coming decades. NAFLD has become a huge health problem and economic burden. SIRT1 is a member of Sirtuins, a group of highly conserved histone deacetylases regulated by NAD+, and plays a vital role in regulating cholesterol and lipid metabolism, improving oxidative stress, inflammation, and insulin resistance through deacetylating some downstream transcription factors and thus improving NAFLD. Although there are no currently approved drugs for treating NAFLD and some unresolved limitations in developing SIRT1 activators, SIRT1 holds promise as a proper therapeutic target for NAFLD and other metabolic diseases. In recent years, natural products have played an increasingly important role in drug development due to their safety and efficacy. It has been discovered that some natural products may be able to prevent and treat NAFLD by targeting SIRT1 and its related pathways. This paper reviews the mechanism of SIRT1 in the improvement of NALFD and the natural products that regulate NAFLD through SIRT1 and its associated pathways, and discusses the potential of SIRT1 as a therapeutic target for treating NAFLD and the effectiveness of these related natural products as clinical drugs or dietary supplements. These works may provide some new ideas and directions for finding new therapeutic targets for NAFLD and the development of anti-NAFLD drugs with good pharmacodynamic properties.

Hippo Signaling in the Ovary: Emerging Roles in Development, Fertility, and Disease

Emerging studies indicate that the Hippo pathway, a highly conserved pathway that regulates organ size control, plays an important role in governing ovarian physiology, fertility, and pathology. Specific to the ovary, the spatiotemporal expression of the major components of the Hippo signaling cascade are observed throughout the reproductive lifespan. Observations from multiple species begin to elucidate the functional diversity and molecular mechanisms of Hippo signaling in the ovary in addition to the identification of interactions with other signaling pathways and responses to various external stimuli. Hippo pathway components play important roles in follicle growth and activation, as well as steroidogenesis, by regulating several key biological processes through mechanisms of cell proliferation, migration, differentiation, and cell fate determination. Given the importance of these processes, dysregulation of the Hippo pathway contributes to loss of follicular homeostasis and reproductive disorders such as polycystic ovary syndrome (PCOS), premature ovarian insufficiency, and ovarian cancers. This review highlights what is currently known about the Hippo pathway core components in ovarian physiology, including ovarian development, follicle development, and oocyte maturation, while identifying areas for future research to better understand Hippo signaling as a multifunctional pathway in reproductive health and biology.

Redox-Unlockable Nanoparticle-Based MST1 Delivery System to Attenuate Hepatic Steatosis via the AMPK/SREBP-1c Signaling Axis

To date, few effective treatments have been licensed for nonalcoholic fatty liver disease (NAFLD), which a kind of chronic liver disease. Mammalian sterile 20-like kinase 1 (MST1) is reported to be involved in the development of NAFLD. Thus, we evaluated the suitability of a redox-unlockable polymeric nanoparticle Hep@PGEA vector to deliver MST1 or siMST1 (HCP/MST1 or HCP/siMST1) for NAFLD therapy. The Hep@PGEA vector can efficiently deliver the condensed functional nucleic acids MST1 or siMST1 into NAFLD-affected mouse liver to upregulate or downregulate MST1 expression. The HCP/MST1 complexes significantly improved liver insulin resistance sensitivity and reduced liver damage and lipid accumulation by the AMPK/SREBP-1c pathway without significant adverse events. Instead, HCP/siMST1 delivery exacerbates the NAFLD. The analysis of NAFLD patient samples further clarified the role of MST1 in the development of hepatic steatosis in patients with NAFLD. The MST1-based gene intervention is of considerable potential for clinical NAFLD therapy, and the Hep@PGEA vector provides a promising option for NAFLD gene therapy.

Roles of Yes-associated protein and transcriptional coactivator with PDZ-binding motif in non-neoplastic liver diseases

The prevalence of liver disease has been increasing worldwide. Moreover, the burden of end-stage liver disease, including cirrhosis and liver cancer, is high because of high mortality and suboptimal treatment. The pathological process of liver disease includes steatosis, hepatocyte death, and fibrosis, which ultimately lead to cirrhosis and liver cancer. Clinical and preclinical evidence indicates that non-neoplastic liver diseases, particularly cirrhosis, are major risk factors for liver cancer, although the mechanism underlying this association remains unclear. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional activators that regulate organ size and cancer development. YAP and TAZ play important roles in liver development, regeneration, and homeostasis. Abnormal YAP and TAZ levels have also been implicated in non-neoplastic liver diseases (e.g., non-alcoholic fatty liver disease, alcoholic liver disease, liver injury, and liver fibrosis). Here, we review recent findings on the roles of YAP and TAZ in non-neoplastic liver diseases and discuss directions for future research. This review provides a basis for the study of non-neoplastic liver diseases.

Mechanisms of ductular reaction in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a disease spectrum caused in part by insulin resistance and genetic predisposition. This disease is primarily characterized by excessive lipid accumulation in hepatocytes in the absence of alcohol abuse and other causes of liver damage. Histologically, NAFLD is divided into several periods: simple steatosis, non-alcoholic steatohepatitis (NASH), hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. With the increasing prevalence of obesity and hyperlipidemia, NAFLD has become the main cause of chronic liver disease worldwide. As a result, the pathogenesis of this disease is drawing increasing attention. Ductular reaction (DR) is a reactive bile duct hyperplasia caused by liver injury that involves hepatocytes, cholangiocytes, and hepatic progenitor cells. Recently, DR is shown to play a pivotal role in simple steatosis progression to NASH or liver fibrosis, providing new research and treatment options. This study reviews several DR signaling pathways, including Notch, Hippo/YAP-TAZ, Wnt/β-catenin, Hedgehog, HGF/c-Met, and TWEAK/Fn14, and their role in the occurrence and development of NASH.

Regulation of SIRT1 and Its Roles in Inflammation

The silent information regulator sirtuin 1 (SIRT1) protein, a highly conserved NAD+-dependent deacetylase belonging to the sirtuin family, is a post-translational regulator that plays a role in modulating inflammation. SIRT1 affects multiple biological processes by deacetylating a variety of proteins including histones and non-histone proteins. Recent studies have revealed intimate links between SIRT1 and inflammation, while alterations to SIRT1 expression and activity have been linked to inflammatory diseases. In this review, we summarize the mechanisms that regulate SIRT1 expression, including upstream activators and suppressors that operate on the transcriptional and post-transcriptional levels. We also summarize factors that influence SIRT1 activity including the NAD+/NADH ratio, SIRT1 binding partners, and post-translational modifications. Furthermore, we underscore the role of SIRT1 in the development of inflammation by commenting on the proteins that are targeted for deacetylation by SIRT1. Finally, we highlight the potential for SIRT1-based therapeutics for inflammatory diseases.

YAP regulates an SGK1/mTORC1/SREBP-dependent lipogenic program to support proliferation and tissue growth

The coordinated regulation of growth control and metabolic pathways is required to meet the energetic and biosynthetic demands associated with proliferation. Emerging evidence suggests that the Hippo pathway effector Yes-associated protein 1 (YAP) reprograms cellular metabolism to meet the anabolic demands of growth, although the mechanisms involved are poorly understood. Here, we demonstrate that YAP co-opts the sterol regulatory element-binding protein (SREBP)-dependent lipogenic program to facilitate proliferation and tissue growth. Mechanistically, YAP stimulates de novo lipogenesis via mechanistic target of rapamcyin (mTOR) complex 1 (mTORC1) signaling and subsequent activation of SREBP. Importantly, YAP-dependent regulation of serum- and glucocorticoid-regulated kinase 1 (SGK1) is required to activate mTORC1/SREBP and stimulate de novo lipogenesis. We also find that the SREBP target genes fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD) are conditionally required to support YAP-dependent proliferation and tissue growth. These studies reveal that de novo lipogenesis is a metabolic vulnerability that can be targeted to disrupt YAP-dependent proliferation and tissue growth.

The role of exosomal miRNA in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) impacts more than one-third of the population and is linked with other metabolic diseases. The term encompasses a wide spectrum of diseases, from modest steatosis to nonalcoholic steatohepatitis, fibrosis and, ultimately, cirrhosis with the potential for development of hepatocellular carcinoma. Currently, available methods for diagnosing NAFLD are invasive or lack accuracy, and monitoring to determine response to therapeutic interventions is challenging. Exosomes are nano-scaled extracellular vesicles that are secreted by a variety of cells. They convey proteins, mRNA, miRNA, and other bioactive molecules between cells and are involved in an extensive range of biological processes, particularly cell-cell communication. Several reports suggest that exosomes mediate miRNAs and, thus, they have potential clinical utility for diagnosis, prognosis, and therapeutics in liver diseases. In view of the vital role of exosomal microRNA in disease, we here synthesized current knowledge about the biogenesis of exosomal miRNA and exosome-mediated microRNA transfer. We then discuss the potential of exosomal miRNA in diagnosis and therapeutics of NAFLD.

The hippo pathway: A master regulator of liver metabolism, regeneration, and disease

The liver is the only visceral organ in the body with a tremendous capacity to regenerate in response to insults that induce inflammation, cell death, and injury. Liver regeneration is a complicated process involving a well-orchestrated activation of non-parenchymal cells in the injured area and proliferation of undamaged hepatocytes. Furthermore, the liver has a Hepatostat, defined as adjustment of its volume to that required for homeostasis. Understanding the mechanisms that control different steps of liver regeneration is critical to informing therapies for liver repair, to help patients with liver disease. The Hippo signaling pathway is well known for playing an essential role in the control and regulation of liver size, regeneration, stem cell self-renewal, and liver cancer. Thus, the Hippo pathway regulates dynamic cell fates in liver, and in absence of its downstream effectors YAP and TAZ, liver regeneration is severely impaired, and the proliferative expansion of liver cells blocked. We will mainly review upstream mechanisms activating the Hippo signaling pathway following partial hepatectomy in mouse model and patients, its roles during different steps of liver regeneration, metabolism, and cancer. We will also discuss how targeting the Hippo signaling cascade might improve liver regeneration and suppress liver tumorigenesis.

Role of histone deacetylase on nonalcoholic fatty liver disease

Introduction: Nonalcoholic fatty liver disease (NAFLD) is a group of diseases related to metabolic abnormalities, which severely impairs the life and health of patients, and brings great pressure to the society and medical resources. Currently, there is no specific treatment. Histone deacetylases (HDACs) have recently been reported to be involved in the pathogenesis of NAFLD and are considered as new targets for the treatment of NAFLD.Area covered: In this review, we summarized the role of HDACs in the pathogenesis of NAFLD and proposed possible therapeutic targets in order to provide new strategies for the treatment of NAFLD.Expert commentary: HDACs and related signal pathways are widely involved in the pathogenesis of NAFLD and have the potential to become therapeutic targets. However, based on current research alone, HDACs cannot be practical applied to the treatment of NAFLD. Therefore, more research on the pathogenesis of NAFLD and the mechanism of HDACs is what we need most now.

E3 ubiquitin ligase Grail promotes hepatic steatosis through Sirt1 inhibition

In obese adults, nonalcoholic fatty liver disease (NAFLD) is accompanied by multiple metabolic dysfunctions. Although upregulated hepatic fatty acid synthesis has been identified as a crucial mediator of NAFLD development, the underlying mechanisms are yet to be elucidated. In this study, we reported upregulated expression of gene related to anergy in lymphocytes (GRAIL) in the livers of humans and mice with hepatic steatosis. Grail ablation markedly alleviated the high-fat diet-induced hepatic fat accumulation and expression of genes related to the lipid metabolism, in vitro and in vivo. Conversely, overexpression of GRAIL exacerbated lipid accumulation and enhanced the expression of lipid metabolic genes in mice and liver cells. Our results demonstrated that Grail regulated the lipid accumulation in hepatic steatosis via interaction with sirtuin 1. Thus, Grail poses as a significant molecular regulator in the development of NAFLD.

Integration of Hippo-YAP Signaling with Metabolism

The Hippo-Yes-associated protein (YAP) signaling network plays a central role as an integrator of signals that control cellular proliferation and differentiation. The past several years have provided an increasing appreciation and understanding of the diverse mechanisms through which metabolites and metabolic signals influence Hippo-YAP signaling, and how Hippo-YAP signaling, in turn, controls genes that direct cellular and organismal metabolism. These connections enable Hippo-YAP signaling to coordinate organ growth and homeostasis with nutrition and metabolism. In this review, we discuss the current understanding of some of the many interconnections between Hippo-YAP signaling and metabolism and how they are affected in disease conditions.

Exosomal miR-199a-5p promotes hepatic lipid accumulation by modulating MST1 expression and fatty acid metabolism

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) and its complications has become an expanding health problem worldwide with limited therapeutic approaches. The current study was aiming to identify novel microRNA in the regulation of hepatic lipid metabolism in NAFLD.

APPROCHES AND RESULTS

Systematic screening of microRNA expression by high-throughput small RNA sequencing demonstrated that microRNA 199a-5p (miR-199a-5p) was significantly upregulated in high fat diet-induced steatosis mouse model, with the most abundant expression in adipose tissue. MST1 was further identified as the target gene for miR-199a with specific recognition at the 3' untranslated region with dural luciferase reporter assay. Delivery of miR-199a-5p with exosomes into mice aggravated liver lipid accumulation in hepatocytes, accompanied by down-regulation of hepatic MST1 expression and modulation of hepatic lipogenesis and lipolysis, including SREBP-1c, AMPK signaling cascades and the down-stream CPT1α and FASN. Conversely, administration of exosome containing anti-miR-199a-5p resulted in attenuated steotosis in mice fed on high fat diet. Importanly, miR-199a-5p-induced abnormal cellular lipid accumulation could be markedly reversed by overexpression of MST1.

CONCLUSION

miR-199a-5p might be an essentail regulator for hepatic lipid metabolism, possibly through its interction with MST1 and the subsequent signaling cascade. Thus, miR-199a-5p may serve as an important therapeutic target in the treatment of NAFLD.

The Hippo Pathway in Liver Homeostasis and Pathophysiology

Studies of the regenerative capacity of the liver have converged on the Hippo pathway, a serine/threonine kinase cascade discovered in Drosophila and conserved from unicellular organisms to mammals. Genetic studies of mouse and rat livers have revealed that the Hippo pathway is a key regulator of liver size, regeneration, development, metabolism, and homeostasis and that perturbations in the Hippo pathway can lead to the development of common liver diseases, such as fatty liver disease and liver cancer. In turn, pharmacological targeting of the Hippo pathway may be utilized to boost regeneration and to prevent the development and progression of liver diseases. We review current insights provided by the Hippo pathway into liver pathophysiology. Furthermore, we present a path forward for future studies to understand how newly identified components of the Hippo pathway may control liver physiology and how the Hippo pathway is regulated in the liver.

MST Kinases and Metabolism

Since the discovery of the mammalian sterile twenty (MST) kinase family of proteins (MST1/STK4, MST2/STK3, MST3/STK24, and SOK1/STK25), much has been done that adds to our knowledge of their structure, regulation, and function. In the last few years, a series of articles has unveiled a previous unknown relation of these kinases with metabolic regulation and the homeostasis of metabolic tissues. The aim of this review is to bring together this body of data to provide a detailed picture of the current knowledge about these proteins, metabolism, and some of the associated diseases.

Suramin protects hepatocytes from LPS-induced apoptosis by regulating mitochondrial stress and inactivating the JNK-Mst1 signaling pathway

An uncontrolled inflammatory response has been implicated in the progression of acute liver failure through poorly understood mechanisms. The aim of our study was to investigate whether suramin attenuates inflammation-mediated hepatocyte apoptosis by modulating mitochondrial homeostasis. Primary hepatocytes were isolated from mice and treated with LPS in vitro in the presence or absence of suramin. Western blotting, immunofluorescence staining, and ELISAs were used to evaluate the mitochondrial stress. The LPS treatment caused hepatocyte death via apoptosis. Interestingly, suramin supplementation attenuated LPS-mediated hepatocyte death by reducing Mst1 expression; the overexpression of Mst1 abolished the anti-apoptotic effects of suramin on LPS-treated hepatocytes. At the molecular level, suramin treatment repressed mitochondrial oxidative stress, sustained mitochondrial dynamics and blocked the caspase-9-mediated mitochondrial apoptosis pathway; these effects of suramin were achieved by reversing Mst1 expression. Furthermore, our study found that suramin modulated Mst1 expression via the JNK signaling pathway. Activation of JNK prevented the suramin-mediated Mst1 downregulation and concomitantly increased hepatocyte apoptosis and mitochondrial dysfunction. Taken together, our results confirmed the anti-apoptotic and anti-inflammatory effects of suramin on LPS-challenged hepatocytes. Suramin sustained hepatocyte viability and attenuated mitochondrial stress via repressing the JNK-Mst1 signaling pathway.

Transcriptome analysis reveals the mechanism of the effect of flower tea Coreopsis tinctoria on hepatic insulin resistance

Non-Camellia tea and herbal medicine help prevent the development of diabetes and other metabolic diseases. Previous studies revealed that Coreopsis tinctoria (CT) flower tea increases insulin sensitivity and, in some high-fat diet (HFD)-fed rats, even prevents hepatic metabolic disorders. However, the molecular mechanisms by which CT improves insulin resistance are not known. In this study, six-week-old rats were fed a normal diet (ND), an HFD or an HFD supplemented with CT for 8 weeks. Serum samples were collected, and the livers were extracted for RNA-seq gene expression analysis. Real-time PCR and western blotting further verified the RNA-seq results. In our results, dietary CT ameliorated HFD-induced hepatosteatosis, glucose intolerance, and insulin resistance. In the HFD group, 1667 differentially expressed genes (DEGs) were identified compared with the ND group. In the CT group, 327 DEGs were identified compared with the HFD group. Some of these DEGs were related to insulin signalling, hepatic lipogenesis and glucose homeostasis. This study suggested that insulin resistance with hyperinsulinaemia, and not insulin insufficiency, is an early problem in HFD-fed rats, and CT downregulates insulin secretion genes (e.g., Rasd1, Stxbp1 and Sfxn1). Hepatic gene and protein expression analyses indicated that the regulatory effects of CT on glucose and lipid homeostasis are likely mediated via the Akt/FoxO1 signalling pathway and are regulated by the transcription factors hairy and enhancer of split 1 (HES1) and small heterodimer partner (SHP). Our study provides transcriptomic evidence of the complex pathogenic mechanism involved in hepatic insulin resistance and proves that supplementation with CT improves insulin resistance at a global scale.

Dysregulation of the Hippo pathway signaling in aging and cancer

Human beings are facing emerging degenerative and cancer diseases, in large part, as a consequence of increased life expectancy. In the near future, researchers will have to put even more effort into fighting these new challenges, one of which will be prevention of cancer while continuing to improve the aging process through this increased life expectancy. In the last few decades, relevance of the Hippo pathway on cancer has become an important study since it is a major regulator of organ size control and proliferation. However, its deregulation can induce tumors throughout the body by regulating cell proliferation, disrupting cell polarity, releasing YAP and TAZ from the Scribble complexes and facilitating survival gene expression via activation of TEAD transcription factors. This pathway is also involved in some of the most important mechanisms that control the aging processes, such as the AMP-activated protein kinase and sirtuin pathways, along with autophagy and oxidative stress response/antioxidant defense. This could be the link between two tightly connected processes that could open a broader range of targeted molecular therapies to fight aging and cancer. Therefore, available knowledge of the processes involved in the Hippo pathway during aging and cancer must necessarily be well understood.

Mst1 inhibition attenuates non-alcoholic fatty liver disease via reversing Parkin-related mitophagy

Obesity-related non-alcoholic fatty liver disease (NAFLD) is connected with mitochondrial stress and hepatocyte apoptosis. Parkin-related mitophagy sustains mitochondrial homeostasis and hepatocyte viability. However, the contribution and regulatory mechanisms of Parkin-related mitophagy in NAFLD are incompletely understood. Macrophage stimulating 1 (Mst1) is a novel mitophagy upstream regulator which excerbates heart and cancer apoptosisn via repressing mitophagy activity. The aim of our study is to explore whether Mst1 contributes to NAFLD via disrupting Parkin-related mitophagy. A NAFLD model was generated in wild-type (WT) mice and Mst1 knockout (Mst1-KO) mice using high-fat diet (HFD). Cell experiments were conducted via palmitic acid (PA) treatment in the primary hepatocytes. The results in our study demonstrated that Mst1 was significantly upregulated in HFD-treated livers. Genetic ablation of Mst1 attenuated HFD-mediated hepatic injury and sustained hepatocyte viability. Functional studies illustrated that Mst1 knockdown reversed Parkin-related mitophagy and the latter protected mitochondria and hepatocytes against HFD challenge. Besides, we further figured out that Mst1 modulated Parkin expression via the AMPK pathway; blockade of AMPK repressed Parkin-related mitophagy and recalled hepatocytes mitochondrial apoptosis. Altogether, our data identified that NAFLD was closely associated with the defective Parkin-related mitophagy due to Mst1 upregulation. This finding may pave the road to new therapeutic modalities for the treatment of fatty liver disease.

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Mst1 deletion prevents diet-induced NAFLD.

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Mst1 deficiency increases Parkin expression and thus reverses mitophagy activity.

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Loss of Parkin-related mitophagy abrogates the protective effect of Mst1 deletion on hepatocyte mitochondrial stress.

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Mst1 modulates Parkin via activating AMPK pathway.

SIRT1 mediates the role of RNA-binding protein QKI 5 in the synthesis of triglycerides in non-alcoholic fatty liver disease mice via the PPARα/FoxO1 signaling pathway

Non-alcoholic fatty liver disease (NAFLD) is the consequence of insulin resistance, fatty acid accumulation, oxidative stress and lipotoxicity. The present study aimed to elucidate the effect of Quaking 5 (QKI 5) as mediated by Sirtuin 1 (SIRT1) on triglyceride (TG) synthesis in the liver of an NAFLD mouse model. A high-fat diet-induced NAFLD model was established in mice, and mouse hepatocytes were isolated to characterize the effects of QKI 5 mediated by SIRT1 on TG synthesis in the liver. Body weight and liver wet weight were recorded. In addition, serum levels of total cholesterol, TG, alanine aminotransferase and aspartate aminotransferase were assessed using an automatic biochemistry analyzer. Hematoxylin and eosin staining was performed to observe the histological morphological alterations of the liver tissues. The concentration of SIRT1 in the serum was also detected. The NAFLD activity score (NAS) was used to evaluate disease severity. The synthesis of TGs in cells or tissues was determined, and the protein levels of SIRT1, QKI 5, peroxisome proliferator-activated receptor (PPAR)α and Forkhead box protein O1 (FoxO1) were examined. The expression levels of SIRT1 or QKI 5, and the acetylation level of QKI 5 were decreased in the mouse model of NAFLD. QKI 5 was deacetylated by SIRT1, which contributed in suppressing the progression of NAFLD in the mice, and inhibiting TG synthesis in vivo and in vitro via the PPARα/FoxO1 signaling pathway. Taken together, the results of the present study demonstrated that SIRT1 deacetylated QKI 5, an RNA-binding protein significantly affecting the synthesis of TG in the liver of the NAFLD mouse model. Furthermore, it activated transcription factor FOXO1 through post-transcriptional regulation of the expression of PPARα and further inhibited the synthesis of TGs, thereby restraining the progression of NAFLD.

Hippo Signaling: Key Emerging Pathway in Cellular and Whole-Body Metabolism

The evolutionarily conserved Hippo pathway is a key regulator of organ size and tissue homeostasis. Its dysregulation is linked to multiple pathological disorders. In addition to regulating development and growth, recent studies show that Hippo pathway components such as MST1/2 and LATS1/2 kinases, as well as YAP/TAZ transcriptional coactivators, are regulated by metabolic pathways and that the Hippo pathway controls metabolic processes at the cellular and organismal levels in physiological and metabolic disease states such as obesity, type 2 diabetes (T2D), nonalcoholic fatty liver disease (NAFLD), cardiovascular disorders, and cancer. In this review we summarize the connection between key Hippo components and metabolism, and how this interplay regulates cellular metabolism and metabolic pathways. The emerging function of Hippo in the regulation of metabolic homeostasis under physiological and pathological conditions is highlighted.