Adiponectin inhibits hepatic stellate cell activation by targeting the PTEN/AKT pathway

Long non-coding RNA growth arrest-specific 5 inhibits liver fibrogenesis in biliary atresia by interacting with microRNA-222 and repressing IGF1/AKT signaling

Background

Long non-coding RNA growth arrest-specific 5 (lncRNA GAS5) has been shown to inhibit liver fibrosis through serving as a competing endogenous RNA for microRNA-222 (miR-222). Progressive liver fibrosis is a typical characteristic of biliary atresia (BA). However, the role of GAS5/miR-222 and its underlying mechanisms remain largely unknown in BA.

Methods

The expression of GAS5 was determined in the liver and primary hepatic stellate cells (HSCs) of BA patients. Then, the effects of GAS5 on the activation and proliferation of HSCs were evaluated. Furthermore, the interaction between GAS5 and miR-222 was investigated by a luciferase gene report assay. Next, the effects of IGF1/AKT signaling were determined to clarify the downstream mechanism of GAS5. Finally, GAS5 administration was performed to explore its role in an experimental BA mouse model.

Results

GAS5 expression was decreased in liver tissues and HSCs of BA patients, and was inversely correlated with liver fibrosis in BA. Up-regulation of GAS5 in LX-2 cells significantly reduced smooth muscle α-actin (α-SMA) and collagen 1a1 (COL1A1) expression, inhibited cell proliferation and clone formation ability, induced S phase increase, and promoted cell apoptosis. Moreover, GAS5 was negatively regulated by miR-222, which promoted HSCs activation and proliferation, and was positively correlated with liver fibrosis in BA. Additionally, the expressions of IGF1, p-PI3K, and p-AKT were decreased when LX-2 cells over-expressed GAS5, whereas knockdown of IGF1 or AKT significantly decreased α-SMA and COL1A1 expression, suppressed cell proliferation, and enhanced cell apoptosis in LX-2 cells. Furthermore, GAS5 administration significantly increased apoptosis and reduced liver fibrosis, α-SMA and COL1A1 expressions in liver tissues of BA mice.

Conclusions

GAS5 inhibited liver fibrosis in BA by interacting with miR-222 and regulating IGF1/AKT signaling, which may be a therapeutic target to alleviate liver fibrosis in BA.

m6A methylation-induced NR1D1 ablation disrupts the HSC circadian clock and promotes hepatic fibrosis

The roles of nuclear receptor subfamily 1 group d member 1 (NR1D1) and the circadian clock in liver fibrosis remain unclear. Here, we showed that liver clock genes, especially NR1D1, were dysregulated in mice with carbon tetrachloride (CCl₄)-induced liver fibrosis. In turn, disruption of the circadian clock exacerbated experimental liver fibrosis. NR1D1-deficient mice were more sensitive to CCl₄-induced liver fibrosis, supporting a critical role of NR1D1 in liver fibrosis development. Validation at the tissue and cellular levels showed that NR1D1 was primarily degraded by N6-methyladenosine (m⁶A) methylation in a CCl₄-induced liver fibrosis model, and this result was also validated in rhythm-disordered mouse models. In addition, the degradation of NR1D1 further inhibited the phosphorylation of dynein-related protein 1-serine site 616 (DRP1^S616), resulting in weakened mitochondrial fission function and increased mitochondrial DNA (mtDNA) release in hepatic stellate cell (HSC), which in turn activated the cGMP-AMP synthase (cGAS) pathway. Activation of the cGAS pathway induced a local inflammatory microenvironment that further stimulated liver fibrosis progression. Interestingly, in the NR1D1 overexpression model, we observed that DRP1^S616 phosphorylation was restored, and cGAS pathway was also inhibited in HSCs, resulting in improved liver fibrosis. Taken together, our results suggest that targeting NR1D1 may be an effective approach to liver fibrosis prevention and management.

Synergistic activation of AMPK by AdipoR1/2 agonist and inhibitor of EDPs-EBP interaction recover NAFLD through enhancing mitochondrial function in mice

Nonalcoholic fatty liver disease (NAFLD), especially nonalcoholic steatohepatitis (NASH), is a common hepatic manifestation of metabolic syndrome. However, there are no effective therapy to treat this devastating disease. Accumulating evidence suggests that the generation of elastin-derived peptides (EDPs) and the inhibition of adiponectin receptors (AdipoR)1/2 plays essential roles in hepatic lipid metabolism and liver fibrosis. We recently reported that the AdipoR1/2 dual agonist JT003 significantly degraded the extracellular matrix (ECM) and ameliorated liver fibrosis. However, the degradation of the ECM lead to the generation of EDPs, which could further alter liver homeostasis negatively. Thus, in this study, we successfully combined AdipoR1/2 agonist JT003 with V14, which acted as an inhibitor of EDPs-EBP interaction to overcome the defect of ECM degradation. We found that combination of JT003 and V14 possessed excellent synergistic benefits on ameliorating NASH and liver fibrosis than either alone since they compensate the shortage of each other. These effects are induced by the enhancement of the mitochondrial antioxidant capacity, mitophagy, and mitochondrial biogenesis via AMPK pathway. Furthermore, specific suppression of AMPK could block the effects of the combination of JT003 and V14 on reduced oxidative stress, increased mitophagy and mitochondrial biogenesis. These positive results suggested that this administration of combination of AdipoR1/2 dual agonist and inhibitor of EDPs-EBP interaction can be recommended alternatively for an effective and promising therapeutic strategy for the treatment of NAFLD and NASH related fibrosis.

DNA methylation in cell plasticity and malignant transformation in liver diseases

The liver possesses extraordinary regenerative capacity mainly attributable to the ability of hepatocytes (HCs) and biliary epithelial cells (BECs) to self-replicate. This ability is left over from their bipotent parent cell, the hepatoblast, during development. When this innate regeneration is compromised due to the absence of proliferative parenchymal cells, such as during cirrhosis, HCs and BEC can transdifferentiate; thus, adding another layer of complexity to the process of liver repair. In addition, dysregulated lineage maintenance in these two cell populations has been shown to promote malignant growth in experimental conditions. Here, malignant transformation, driven in part by insufficient maintenance of lineage reprogramming, contributes to end-stage liver disease. Epigenetic changes are key drivers for cell fate decisions as well as transformation by finetuning overall transcription and gene expression. In this review, we address how altered DNA methylation contributes to the initiation and progression of hepatic cell fate conversion and cancer formation. We also discussed the diagnostic and therapeutic potential of targeting DNA methylation in liver cancer, its current limitations, and what future research is necessary to facilitate its contribution to clinical translation.

Excessive gluconeogenesis causes the hepatic insulin resistance paradox and its sequelae

Background

Hepatic insulin signaling suppresses gluconeogenesis but promotes de novo lipid synthesis. Paradoxically, hepatic insulin resistance (HIR) enhances both gluconeogenesis and de novo lipid synthesis. Elucidation of the etiology of this paradox, which participates in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, the metabolic syndrome and hepatocellular carcinoma, has not been fully achieved.

Scope of review

This article briefly outlines the previously proposed hypotheses on the etiology of the HIR paradox. It then discusses literature consistent with an alternative hypothesis that excessive gluconeogenesis, the direct effect of HIR, is responsible for the aberrant lipogenesis. The mechanisms involved therein are explained, involving de novo synthesis of fructose and uric acid, promotion of glutamine anaplerosis, and induction of glucagon resistance. Thus, gluconeogenesis via lipogenesis promotes hepatic steatosis, a component of NAFLD, and dyslipidemia. Gluconeogenesis-centred mechanisms for the progression of NAFLD from simple steatosis to non-alcoholic steatohepatitis (NASH) and fibrosis are suggested. That NAFLD often precedes and predicts type 2 diabetes is explained by the ability of lipogenesis to cushion against blood glucose dysregulation in the earlier stages of NAFLD.

Major conclusions

HIR-induced excessive gluconeogenesis is a major cause of the HIR paradox and its sequelae. Such involvement of gluconeogenesis in lipid synthesis rationalizes the fact that several types of antidiabetic drugs ameliorate NAFLD. Thus, dietary, lifestyle and pharmacological targeting of HIR and hepatic gluconeogenesis may be a most viable approach for the prevention and management of the HIR-associated network of diseases.

Dust fall PM2.5-induced lung inflammation in rats is associated with hypermethylation of the IFN-γ gene promoter via the PI3K-Akt-DNMT3b pathway

Inflammation is one of the major adverse effects of fine particulate matter (PM_2.5) on the lung system; however, its mechanisms remain unclear. Rats were exposed to different concentrations of PM_2.5 to investigate the mechanism of short-term exposure-induced lung inflammation. The regulation of PI3K-Akt and DNA methyltransferase 3b (DNMT3b) was assessed by using a PI3K inhibitor and a DNA methyltransferase inhibitor. We found that PM_2.5 could decrease interferon-γ (IFN-γ) levels and increase interleukin 4 (IL-4), IL-5 and IL-13 levels in bronchoalveolar lavage fluid (BALF) to promote eosinophil infiltration and eventually lead to allergic pulmonary inflammation. Moreover, the CpG island methylation rate of the IFN-γ promoter and the protein expression of DNMT3b, PI3K and p-Akt were increased in lung tissues after PM_2.5 exposure. Both inhibitors reversed the CpG island hypermethylation of IFN-γ. In conclusion, in PM_2.5-induced lung injury, the activated PI3K-Akt pathway, via an increase in DNMT3b expression, is involved in CpG hypermethylation of the IFN-γ gene promoter.

Methionine cycle in nonalcoholic fatty liver disease and its potential applications

As a chronic metabolic disease affecting epidemic proportions worldwide, the pathogenesis of Nonalcoholic Fatty Liver Disease (NAFLD) is not clear yet. There is also a lack of precise biomarkers and specific medicine for the diagnosis and treatment of NAFLD. Methionine metabolic cycle, which is critical for the maintaining of cellular methylation and redox state, is involved in the pathophysiology of NAFLD. However, the molecular basis and mechanism of methionine metabolism in NAFLD are not completely understood. Here, we mainly focus on specific enzymes that participates in methionine cycle, to reveal their interconnections with NAFLD, in order to recognize the pathogenesis of NAFLD from a new angle and at the same time, explore the clinical characteristics and therapeutic strategies.

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.

Phosphatase and Tensin Homolog in Non-neoplastic Digestive Disease: More Than Just Tumor Suppressor

The Phosphatase and tensin homolog (PTEN) gene is one of the most important tumor suppressor genes, which acts through its unique protein phosphatase and lipid phosphatase activity. PTEN protein is widely distributed and exhibits complex biological functions and regulatory modes. It is involved in the regulation of cell morphology, proliferation, differentiation, adhesion, and migration through a variety of signaling pathways. The role of PTEN in malignant tumors of the digestive system is well documented. Recent studies have indicated that PTEN may be closely related to many other benign processes in digestive organs. Emerging evidence suggests that PTEN is a potential therapeutic target in the context of several non-neoplastic diseases of the digestive tract. The recent discovery of PTEN isoforms is expected to help unravel more biological effects of PTEN in non-neoplastic digestive diseases.

Lipotoxic hepatocyte-derived exosomal miR-1297 promotes hepatic stellate cell activation through the PTEN signaling pathway in metabolic-associated fatty liver disease

BACKGROUND

Exosomes play an important role in metabolic-associated fatty liver disease (MAFLD), but the mechanism by which exosomes participate in MAFLD still remain unclear.

AIM

To figure out the function of lipotoxic exosomal miR-1297 in MAFLD.

METHODS

MicroRNA sequencing was used to detect differentially expressed miRNAs (DE-miR) in lipotoxic exosomes derived from primary hepatocytes. Bioinformatic tools were applied to analyze the target genes and pathways regulated by the DE-miRs. Quantitative real-time PCR (qPCR) was conducted for the verification of DE-miRs. qPCR, western blot, immunofluorescence staining and ethynyl-20-deoxyuridine assay were used to evaluate the function of lipotoxic exosomal miR-1297 on hepatic stellate cells (LX2 cells). A luciferase reporter experiment was performed to confirm the relationship of miR-1297 and its target gene PTEN.

RESULTS

MicroRNA sequencing revealed that there were 61 exosomal DE-miRs (P < 0.05) with a fold-change > 2 from palmitic acid treated primary hepatocytes compared with the vehicle control group. miR-1297 was the most highly upregulated according to the microRNA sequencing. Bioinformatic tools showed a variety of target genes and pathways regulated by these DE-miRs were related to liver fibrosis. miR-1297 was overexpressed in exosomes derived from lipotoxic hepatocytes by qPCR. Fibrosis promoting genes (α-SMA, PCNA) were altered in LX2 cells after miR-1297 overexpression or miR-1297-rich lipotoxic exosome incubation via qPCR and western blot analysis. Immunofluorescence staining and ethynyl-20-deoxyuridine staining demonstrated that the activation and proliferation of LX2 cells were also promoted after the above treatment. PTEN was found to be the target gene of miR-1297 and knocking down PTEN contributed to the activation and proliferation of LX2 cells via modulating the PI3K/AKT signaling pathway.

CONCLUSION

miR-1297 was overexpressed in exosomes derived from lipotoxic hepatocytes. The lipotoxic hepatocyte-derived exosomal miR-1297 could promote the activation and proliferation of hepatic stellate cells through the PTEN/PI3K/AKT signaling pathway, accelerating the progression of MAFLD.

Schistosoma japonicum Infection Leads to the Reprogramming of Glucose and Lipid Metabolism in the Colon of Mice

The deposition of Schistosoma japonicum (S. japonicum) eggs commonly induces inflammation, fibrosis, hyperplasia, ulceration, and polyposis in the colon, which poses a serious threat to human health. However, the underlying mechanism is largely neglected. Recently, the disorder of glucose and lipid metabolism was reported to participate in the liver fibrosis induced by the parasite, which provides a novel clue for studying the underlying mechanism of the intestinal pathology of the disease. This study focused on the metabolic reprogramming profiles of glucose and lipid in the colon of mice infected by S. japonicum. We found that S. japonicum infection shortened the colonic length, impaired intestinal integrity, induced egg-granuloma formation, and increased colonic inflammation. The expression of key enzymes involved in the pathways regulating glucose and lipid metabolism was upregulated in the colon of infected mice. Conversely, phosphatase and tensin homolog deleted on chromosome ten (PTEN) and its downstream signaling targets were significantly inhibited after infection. In line with these results, in vitro stimulation with soluble egg antigens (SEA) downregulated the expression of PTEN in CT-26 cells and induced metabolic alterations similar to that observed under in vivo results. Moreover, PTEN over-expression prevented the reprogramming of glucose and lipid metabolism induced by SEA in CT-26 cells. Overall, the present study showed that S. japonicum infection induces the reprogramming of glucose and lipid metabolism in the colon of mice, and PTEN may play a vital role in mediating this metabolic reprogramming. These findings provide a novel insight into the pathogenicity of S. japonicum in hosts.

Inhibition of miR-188-5p alleviates hepatic fibrosis by significantly reducing the activation and proliferation of HSCs through PTEN/PI3K/AKT pathway

Persistent hepatic damage and chronic inflammation in liver activate the quiescent hepatic stellate cells (HSCs) and cause hepatic fibrosis (HF). Several microRNAs regulate the activation and proliferation of HSCs, thereby playing a critical role in HF progression. Previous studies have reported that miR‐188‐5p is dysregulated during the process of HF. However, the role of miR‐188‐5p in HF remains unclear. This study investigated the potential role of miR‐188‐5p in HSCs and HF. Firstly, we validated the miR‐188‐5p expression in primary cells isolated from liver of carbon tetrachloride (CCl₄)‐induced mice, TGF‐β1‐induced LX‐2 cells, livers from 6‐month high‐fat diet (HFD)‐induced rat and 4‐month HFD‐induced mice NASH models, and human non‐alcoholic fatty liver disease (NAFLD) patients. Furthermore, we used miR‐188‐5p inhibitors to investigate the therapeutic effects of miR‐188‐5p inhibition in the HFD + CCl₄ induced in vivo model and the potential role of miR‐188‐5p in the activation and proliferation of HSCs. This present study reported that miR‐188‐5p expression is significantly increased in the human NAFLD, HSCs isolated from liver of CCl₄ induced mice, and in vitro and in vivo models of HF. Mimicking the miR‐188‐5p resulted in the up‐regulation of HSC activation and proliferation by directly targeting the phosphatase and tensin homolog (PTEN). Moreover, inhibition of miR‐188‐5p reduced the activation and proliferation markers of HSCs through PTEN/AKT pathway. Additionally, in vivo inhibition of miR‐188‐5p suppressed the HF parameters, pro‐fibrotic and pro‐inflammatory genes, and fibrosis. Collectively, our results uncover the pro‐fibrotic role of miR‐188‐5p. Furthermore, we demonstrated that miR‐188‐5p inhibition decreases the severity of HF by reducing the activation and proliferation of HSCs through PTEN/AKT pathway.

Dual Pharmacological Targeting of HDACs and PDE5 Inhibits Liver Disease Progression in a Mouse Model of Biliary Inflammation and Fibrosis

Simple Summary

Chronic liver injury and inflammation leads to excessive deposition of extracellular matrix, known as liver fibrosis, and the distortion of the hepatic parenchyma. Liver fibrosis may progress to cirrhosis, a condition in which hepatic function is impaired and most cases of liver tumors occur. Currently, there are no effective therapies to inhibit and reverse the progression of liver fibrosis, and therefore, chronic liver disease remains a global health problem. In this study we have tested the efficacy of a new class of molecules that simultaneously target two molecular pathways known to be involved in the pathogenesis of hepatic fibrosis. In a clinically relevant mouse model of liver injury and inflammation we show that the combined inhibition of histones deacetylases and the cyclic guanosine monophosphate (cGMP) phosphodiesterase phosphodiesterase 5 (PDE5) results in potent anti-inflammatory and anti-fibrotic effects. Our findings open new avenues for the treatment of liver fibrosis and therefore, the prevention of hepatic carcinogenesis.

Abstract

Liver fibrosis, a common hallmark of chronic liver disease (CLD), is characterized by the accumulation of extracellular matrix secreted by activated hepatic fibroblasts and stellate cells (HSC). Fibrogenesis involves multiple cellular and molecular processes and is intimately linked to chronic hepatic inflammation. Importantly, it has been shown to promote the loss of liver function and liver carcinogenesis. No effective therapies for liver fibrosis are currently available. We examined the anti-fibrogenic potential of a new drug (CM414) that simultaneously inhibits histone deacetylases (HDACs), more precisely HDAC1, 2, and 3 (Class I) and HDAC6 (Class II) and stimulates the cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway activity through phosphodiesterase 5 (PDE5) inhibition, two mechanisms independently involved in liver fibrosis. To this end, we treated Mdr2-KO mice, a clinically relevant model of liver inflammation and fibrosis, with our dual HDAC/PDE5 inhibitor CM414. We observed a decrease in the expression of fibrogenic markers and collagen deposition, together with a marked reduction in inflammation. No signs of hepatic or systemic toxicity were recorded. Mechanistic studies in cultured human HSC and cholangiocytes (LX2 and H69 cell lines, respectively) demonstrated that CM414 inhibited pro-fibrogenic and inflammatory responses, including those triggered by transforming growth factor β (TGFβ). Our study supports the notion that simultaneous targeting of pro-inflammatory and fibrogenic mechanisms controlled by HDACs and PDE5 with a single molecule, such as CM414, can be a new disease-modifying strategy.

AKR-001, an Fc-FGF21 Analog, Showed Sustained Pharmacodynamic Effects on Insulin Sensitivity and Lipid Metabolism in Type 2 Diabetes Patients

Experimental fibroblast growth factor 21 (FGF21) analogs can improve lipid profiles in patients with metabolic diseases. However, their effects on markers of insulin sensitivity appear to be minimal, potentially because of insufficient exposure. Systemic drug levels vary from sub-pharmacological to demonstrating pharmacodynamic effects but with dose-limiting adverse events. Here we report results from a phase 1 multiple ascending dose study of AKR-001, an Fc-FGF21 fusion protein engineered for sustained systemic pharmacologic exposure, in individuals with type 2 diabetes. With a half-life of 3-3.5 days, the peak-to-trough ratio under steady-state conditions is approximately 2 following QW dosing. AKR-001 appears to demonstrate pharmacodynamic effects on serum markers of insulin sensitivity and acceptable tolerability up to and including 70 mg QW. Positive trends in lipoprotein profile, including triglycerides, non-high-density lipoprotein (non-HDL) cholesterol, HDL-C, and apolipoproteins B and C3 are consistent with other FGF21 analogs. AKR-001's clinical profile supports further evaluation as a treatment for metabolic diseases.

Effect of PFOA on DNA Methylation and Alternative Splicing in Mouse Liver

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant prevalent in the environment and implicated in damage to the liver leading to a fatty liver phenotype called hepatocellular steatosis. Our goal is to provide a basis for PFOA-induced hepatocellular steatosis in relation to epigenetic alterations and mRNA splicing. Young adult female mice exposed to different concentrations of PFOA showed an increase in liver weight with decreased global DNA methylation (5-mC). At higher concentrations, the expression of DNA methyltransferase 3A (Dnmt3a) was significantly reduced and the expression of tet methycytosine dioxygenase 1 (Tet1) was significantly increased. There was no significant change in the other Dnmts and Tets. PFOA exposure significantly increased the expression of cell cycle regulators and anti-apoptotic genes. The expression of multiple genes involved in mTOR (mammalian target of rapamycin) signaling pathway were altered significantly with reduction in Pten (phosphatase and tensin homolog, primary inhibitor of mTOR pathway) expression. Multiple splicing factors whose protein but not mRNA levels affected by PFOA exposure were identified. The changes in protein abundance of the splicing factors was also reflected in altered splicing pattern of their target genes, which provided new insights on the previously unexplored mechanisms of PFOA-mediated hepatotoxicity and pathogenesis.

Epigenetic silencing of LncRNA ANRIL enhances liver fibrosis and HSC activation through activating AMPK pathway

Long non‐coding RNAs (LncRNAs) and DNA methylation are important epigenetic mark play a key role in liver fibrosis. Currently, how DNA methylation and LncRNAs control the hepatic stellate cell (HSC) activation and fibrosis has not yet been fully characterized. Here, we explored the role of antisense non‐coding RNA in the INK4 locus (ANRIL) and DNA methylation in HSC activation and fibrosis. The expression levels of DNA methyltransferases 3A (DNMT3A), ANRIL, α‐Smooth muscle actin (α‐SMA), Type I collagen (Col1A1), adenosine monophosphate‐activated protein kinase (AMPK) and p‐AMPK in rat and human liver fibrosis were detected by immunohistochemistry, qRT‐PCR and Western blotting. Liver tissue histomorphology was examined by haematoxylin and eosin (H&E), Sirius red and Masson staining. HSC was transfected with DNMT3A‐siRNA, over‐expressing ANRIL and down‐regulating ANRIL. Moreover, cell proliferation ability was examined by CCK‐8, MTT and cell cycle assay. Here, our study demonstrated that ANRIL was significantly decreased in activated HSC and liver fibrosis tissues, while Col1A1, α‐SMA and DNMT3A were significantly increased in activated HSC and liver fibrosis tissues. Further, we found that down‐regulating DNMT3A expression leads to inhibition of HSC activation. Reduction in DNMT3A elevated ANRIL expression in activated HSC. Furthermore, we performed the over expression ANRIL suppresses HSC activation and AMPK signalling pathways. In sum, our study found that epigenetic DNMT3A silencing of ANRIL enhances liver fibrosis and HSC activation through activating AMPK pathway. Targeting epigenetic modulators DNMT3A and ANRIL, and offer a novel approach for liver fibrosis therapy.

Nonalcoholic Fatty Liver Disease in Adults: Current Concepts in Etiology, Outcomes, and Management

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of disease, extending from simple steatosis to inflammation and fibrosis with a significant risk for the development of cirrhosis. It is highly prevalent and is associated with significant adverse outcomes both through liver-specific morbidity and mortality but, perhaps more important, through adverse cardiovascular and metabolic outcomes. It is closely associated with type 2 diabetes and obesity, and both of these conditions drive progressive disease toward the more advanced stages. The mechanisms that govern hepatic lipid accumulation and the predisposition to inflammation and fibrosis are still not fully understood but reflect a complex interplay between metabolic target tissues including adipose and skeletal muscle, and immune and inflammatory cells. The ability to make an accurate assessment of disease stage (that relates to clinical outcome) can also be challenging. While liver biopsy is still regarded as the gold-standard investigative tool, there is an extensive literature on the search for novel noninvasive biomarkers and imaging modalities that aim to accurately reflect the stage of underlying disease. Finally, although no therapies are currently licensed for the treatment of NAFLD, there are interventions that appear to have proven efficacy in randomized controlled trials as well as an extensive emerging therapeutic landscape of new agents that target many of the fundamental pathophysiological processes that drive NAFLD. It is highly likely that over the next few years, new treatments with a specific license for the treatment of NAFLD will become available.

FGF21: An Emerging Therapeutic Target for Non-Alcoholic Steatohepatitis and Related Metabolic Diseases

The rising global prevalence of obesity, metabolic syndrome, and type 2 diabetes has driven a sharp increase in non-alcoholic fatty liver disease (NAFLD), characterized by excessive fat accumulation in the liver. Approximately one-sixth of the NAFLD population progresses to non-alcoholic steatohepatitis (NASH) with liver inflammation, hepatocyte injury and cell death, liver fibrosis and cirrhosis. NASH is one of the leading causes of liver transplant, and an increasingly common cause of hepatocellular carcinoma (HCC), underscoring the need for intervention. The complex pathophysiology of NASH, and a predicted prevalence of 3-5% of the adult population worldwide, has prompted drug development programs aimed at multiple targets across all stages of the disease. Currently, there are no approved therapeutics. Liver-related morbidity and mortality are highest in more advanced fibrotic NASH, which has led to an early focus on anti-fibrotic approaches to prevent progression to cirrhosis and HCC. Due to limited clinical efficacy, anti-fibrotic approaches have been superseded by mechanisms that target the underlying driver of NASH pathogenesis, namely steatosis, which drives hepatocyte injury and downstream inflammation and fibrosis. Among this wave of therapeutic mechanisms targeting the underlying pathogenesis of NASH, the hormone fibroblast growth factor 21 (FGF21) holds considerable promise; it decreases liver fat and hepatocyte injury while suppressing inflammation and fibrosis across multiple preclinical studies. In this review, we summarize preclinical and clinical data from studies with FGF21 and FGF21 analogs, in the context of the pathophysiology of NASH and underlying metabolic diseases.

Reduced m6A modification predicts malignant phenotypes and augmented Wnt/PI3K-Akt signaling in gastric cancer

Background

As the most abundant epigenetic modification on mRNAs and long non‐coding RNAs, N6‐methyladenosine (m6A) modification extensively exists in mammalian cells. Controlled by writers (methyltransferases), readers (signal transducers), and erasers (demethylases), m6A influences mRNA structure, maturation, and stability, thus negatively regulating protein expression in a post‐translational manner. Nevertheless, current understanding of m6A's roles in tumorigenesis, especially in gastric cancer (GC) remains to be unveiled. In this study, we assessed m6A's clinicopathological relevance to GC and explored the underlying mechanisms.

Methods

By referring to a proteomics‐based GC cohort we previously generated and the TCGA‐GC cohort, we merged expressions of canonical m6A writers (METTL3/METTL14), readers (YTHDF1/YTHDF2/YTHDF3), and erasers (ALKBH5/FTO), respectively, as W, R, and E signatures to represent m6A modification. We stratified patients according to these signatures to decipher m6A's associations with crucial mutations, prognosis, and clinical indexes. m6A's biological functions in GC were predicted by gene set enrichment analysis (GSEA) and validated by in vitro experiments.

Results

We discovered that W and R were potential tumor suppressive signatures, while E was a potential oncogenic signature in GC. According to W/R/E stratifications, patients with low m6A‐indications were accompanied with higher mutations of specific genes (CDH1, AR, GLI3, SETBP1, RHOA, MUC6, and TP53) and also demonstrated adverse clinical outcomes. GSEA suggested that reduced m6A was correlated with oncogenic signaling and phenotypes. Through in vitro experiments, we proved that m6A suppression (represented by METTL14 knockdown) promoted GC cell proliferation and invasiveness through activating Wnt and PI3K‐Akt signaling, while m6A elevation (represented by FTO knockdown) reversed these phenotypical and molecular changes. m6A may also be involved in interferon signaling and immune responses of GC.

Conclusions

Our work demonstrated that low‐m6A signatures predicted adverse clinicopathological features of GC, while the reduction of RNA m6A methylation activated oncogenic Wnt/PI3K‐Akt signaling and promoted malignant phenotypes of GC cells.

miR-140-3p Knockdown Suppresses Cell Proliferation and Fibrogenesis in Hepatic Stellate Cells via PTEN-Mediated AKT/mTOR Signaling

PURPOSE

Liver fibrosis is a major cause of morbidity and mortality and the outcome of various chronic liver diseases. Activation of hepatic stellate cells (HSCs) is the key event in liver fibrosis. Studies have confirmed that miR-140-3p plays a potential regulatory effect on HSC activation. However, whether miR-140-3p mediates the liver fibrosis remains unknown.

MATERIALS AND METHODS

Expression of miR-140-3p was detected by real-time quantitative PCR (qPCR). Cell proliferation was measured by MTT, while cell apoptosis rate was determined via flow cytometry. Western blot assay was used to detect the expression of cleaved PARP. The fibrogenic effect was evaluated by expression of α-smooth muscle actin and desmin. Functional experiments were performed in transforming growth factor β1 (TGF-β1)-induced HSC-T6 cells with transfection of anti-miR-140-3p and/or siPTEN. Target binding between miR-140-3p and PTEN was predicted by the TargetScan database and identified using luciferase reporter assay and RNA immunoprecipitation.

RESULTS

TGF-β1 induced the activation of HSC-T6 cells, and miR-140-3p expression varied according to HSC-T6 cell activation status. Knockdown of miR-140-3p reduced cell proliferation and the expressions of α-SMA and desmin, as well as increased apoptosis, in TGF-β1-induced HSC-T6 cells, which could be blocked by PTEN silencing. Additionally, inactivation of the AKT/mTOR signaling pathway stimulated by miR-140-3p knockdown was abolished when silencing PTEN expression. PTEN was negatively regulated by miR-140-3p via direct binding in HSC-T6 cells.

CONCLUSION

miR-140-3p is an important mediator in HSC-T6 cell activation, and miR-140-3p knockdown suppresses cell proliferation and fibrogenesis in TGF-β1-induced HSC-T6 cells, indicating that miR-140-3p may be a potential novel molecular target for liver fibrosis.

Di-n-butyl phthalate epigenetically induces reproductive toxicity via the PTEN/AKT pathway

Di-n-butyl phthalate (DBP) is a kind of ubiquitous chemical linked to hormonal disruptions that affects male reproductive system. However, the mechanism of DBP-induced germ cells toxicity remains unclear. Here, we demonstrate that DBP induces reduction of proliferation, increase of apoptosis and DNA damage dependent on the PTEN/AKT pathway. Mechanistically, DBP decreases PTEN promoter methylation and increases its transcriptional activity, leading to increased PTEN expression. Notably, DNMT3b is confirmed as a target of miR-29b and miR-29b-mediated status of PTEN methylation is involved in the effects of DBP treatment. Meanwhile, DBP decreases AKT pathway expression via increasing PTEN expression. In addition, the fact that DBP decreases the sperm number and the percentage of motile and progressive sperm is associated with downregulated AKT pathway and sperm flagellum-related genes. Collectively, these findings indicate that DBP induces aberrant PTEN demethylation, leading to inhibition of the AKT pathway, which contributes to the reproductive toxicity.