Elovl6 promotes nonalcoholic steatohepatitis

Single and multi-omic characterization of a porcine model of ethanol-induced hepatic fibrosis

Cirrhosis is a form of end-stage liver disease characterized by extensive hepatic fibrosis and loss of liver parenchyma. It is most commonly the result of long-term alcohol abuse in the United States. Large animal models of cirrhosis, as well as of one of its common long-term sequelae, HCC, are needed to study novel and emerging therapeutic interventions. In the present study, liver fibrosis was induced in the Oncopig cancer model, a large animal HCC model, via intrahepatic, intra-arterial ethanol infusion. Liver sections from five fibrosis induced and five age-matched controls were harvested for RNA-seq (mRNA and lncRNA), small RNA-seq (miRNA), and reduced representation bisulfite sequencing (RRBS; DNA methylation). Single- and multi-omic analysis was performed to investigate the transcriptomic and epigenomic mechanisms associated with fibrosis deposition in this model. A total of 3,439 genes, 70 miRNAs, 452 lncRNAs, and 7,715 methylation regions were found to be differentially regulated through individual single-omic analysis. Pathway analysis indicated differentially expressed genes were associated with collagen synthesis and turnover, hepatic metabolic functions such as ethanol and lipid metabolism, and proliferative and anti-proliferative pathways including PI3K and BAX/BCL signaling pathways. Multi-omic latent variable analysis demonstrated significant concordance with the single-omic analysis. lncRNA's associated with UHRF1BP1L and S1PR1 genes were found to reliably discriminate the two arms of the study. These genes were previously implicated in human cancer development and vasculogenesis, respectively. These findings support the validity and translatability of this model as a useful preclinical tool in the study of alcoholic liver disease and its treatment.

Rapamycin induced autophagy enhances lipid breakdown and ameliorates lipotoxicity in Atlantic salmon cells

Autophagy is a highly conserved cellular recycling process essential for homeostasis in all eukaryotic cells. Lipid accumulation and its regulation by autophagy are key areas of research for understanding metabolic disorders in human and model mammals. However, the role of autophagy in lipid regulation remains poorly characterized in non-model fish species of importance to food production, which could be important for managing health and welfare in aquaculture. Addressing this knowledge gap, we investigate the role of autophagy in lipid regulation using a macrophage-like cell line (SHK-1) from Atlantic salmon (Salmo salar L.), the world's most commercially valuable farmed finfish. Multiple lines of experimental evidence reveal that the autophagic pathway responsible for lipid droplet breakdown is conserved in Atlantic salmon cells. We employed global lipidomics and proteomics analyses on SHK-1 cells subjected to lipid overload, followed by treatment with rapamycin to induce autophagy. This revealed that activating autophagy via rapamycin enhances storage of unsaturated triacylglycerols and suppresses key lipogenic proteins, including fatty acid elongase 6, fatty acid binding protein 2 and acid sphingomyelinase. Moreover, fatty acid elongase 6 and fatty acid binding protein 2 were identified as possible cargo for autophagosomes, suggesting a critical role for autophagy in lipid metabolism in fish. Together, this study establishes a novel model of lipotoxicity and advances understanding of lipid autophagy in fish cells, with significant implications for addressing fish health issues in aquaculture.

Selective PPARα Modulator (SPPARMα) in the Era of the MASLD Pandemic: Current Insights and Future Prospects

Metabolic dysfunction-associated steatotic liver disease (MASLD) has emerged as a significant global health concern, affecting approximately 30% of the population. In Japan, its prevalence is also rising rapidly and is expected to reach 50% by 2040. This situation can be described as a "MASLD pandemic", emphasizing the urgent need for effective therapeutic interventions. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that play essential roles in lipid metabolism, inflammation regulation, and fibrosis modulation. Among them, PPARα is a key regulator of lipid homeostasis, primarily expressed in the liver and other metabolically active tissues. Its activation promotes fatty acid oxidation and improves lipid profiles, making it a crucial target for metabolic disorders. In Japan, a novel selective PPARα modulator (SPPARMα) was developed as a lipid-lowering agent for treating dyslipidemia. Over time, increasing clinical evidence has suggested that SPPARMα has beneficial effects on MASLD patients' liver function. This review aims to summarize the therapeutic potential of SPPARMα in MASLD by examining the functional mechanisms of PPARα, preclinical studies in animal models, and accumulating clinical evidence from MASLD patients. Furthermore, we provide an overview of ongoing clinical trials investigating SPPARMα for MASLD treatment.

Emerging insights on the role of Elovl6 in human diseases: Therapeutic challenges and opportunities

ELOVL6, elongation-of-very-long-chain-fatty acids 6, a crucial enzyme in lipid metabolism, primarily responsible for the elongation of carbon chains of C12-C16 saturated fatty acids. It plays a significant role in various human diseases, particularly those associated with metabolic disorders related to fatty acid synthesis, such as insulin resistance, non-alcoholic fatty liver disease, cancer, and cardiovascular diseases. Emerging research also links ELOVL6 to kidney diseases, neurological conditions such as epilepsy, and pulmonary fibrosis. The enzyme's expression is regulated by various factors including diet, oxidative stress, and circadian rhythms. For instance, a high-carbohydrate diet can promote an increase in ELOVL6 expression. This abnormality leads to an accumulation of long-chain fatty acids and lipid deposition, ultimately resulting in pathological consequences across multiple systems in the body. As a biological target, ELOVL6 holds promise for diagnostic and therapeutic applications, with future research expected to uncover its mechanisms and therapeutic potential, paving the way for novel interventions in multiple disease areas. Here, the expression regulation and function of ELOVL6 in various human diseases are reviewed. This review underscores ELOVL6 as a significant therapeutic target for human diseases, with its potential for diagnostic and therapeutic applications anticipated to drive future research and enable innovative interventions in various pathological conditions.

Abnormal ac4C modification in metabolic dysfunction associated steatotic liver cells

The pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) remains unclear due to the complexity of its etiology. The emerging field of the epitranscriptome has shown significant promise in advancing the understanding of disease pathogenesis and developing new therapeutic approaches. Recent research has demonstrated that N4-acetylcytosine (ac4C), an RNA modification within the epitranscriptome, is implicated in progression of various diseases. However, the role of ac4C modification in MASLD remains unexplored. Herein, we performed acRIP-ac4c-seq and RNA-seq analysis in free fatty acids-induced MASLD model cells, identifying 2128 differentially acetylated ac4C sites, with 1031 hyperacetylated and 1097 hypoacetylated peaks in MASLD model cells. Functional enrichments analysis showed that ac4C differentially modified genes were significantly involved in processes related to MASLD, such as nuclear transport and MAP kinase (MAPK) signaling pathway. We also identified 341 differentially expressed genes (DEGs), including 61 lncRNAs and 280 mRNAs, between control and MASLD model cells. Bioinformatics analysis showed that DEGs were significantly enriched in long-chain fatty acid biosynthetic process. Notably, 118 genes exhibited significant changes in both ac4C modification and expression levels in MASLD model cells. Among these proteins, JUN, caveolin-1 (CAV1), fatty acid synthase (FASN), and heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) were identified as core proteins through protein-protein interaction (PPI) network analysis using cytoscape software. Collectively, our findings establish a positive correlation between ac4C modification and the pathogenesis of MASLD and suggest that ac4C modification may serve as a therapeutic target for MASLD.

Impaired unsaturated fatty acid elongation alters mitochondrial function and accelerates metabolic dysfunction-associated steatohepatitis progression

BACKGROUND AND AIMS

Although qualitative and quantitative alterations in liver Polyunsaturated Fatty Acids (PUFAs) are observed in MASH in humans, a causal relationship of PUFAs biosynthetic pathways is yet to be clarified. ELOVL5, an essential enzyme in PUFA elongation regulates hepatic triglyceride metabolism. Nonetheless, the long-term consequences of elongase disruption, particularly in murine models of MASH, have not been evaluated.

APPROACH & RESULTS

In humans, transcriptomic data indicated that PUFAs biosynthesis enzymes and notably ELOVL5 were induced during MASH progression. Moreover, gene module association determination revealed that ELOVL5 expression was associated with mitochondrial function in both humans and mice. WT and Elovl5-deficient mice were fed a high-fat, high-sucrose (HF/HS) diet for four months. Elovl5 deficiency led to limited systemic metabolic alterations but significant hepatic phenotype was observed in Elovl5-/- mice after the HF/HS diet, including hepatomegaly, pronounced macrovesicular and microvesicular steatosis, hepatocyte ballooning, immune cell infiltration, and fibrosis. Lipid analysis confirmed hepatic triglyceride accumulation and a reshaping of FA profile. Transcriptomic analysis indicated significant upregulation of genes involved in immune cell recruitment and fibrosis, and downregulation of genes involved in oxidative phosphorylation in Elovl5-/- mice. Alterations of FA oxidation and energy metabolism were confirmed by non-targeted metabolomic approach. Analysis of mitochondrial function in Elovl5-/- mice showed morphological alterations, qualitative cardiolipin changes with an enrichment in species containing shorter unsaturated FAs, and decreased activity of I and III respiratory chain complexes.

CONCLUSION

Enhanced susceptibility to diet-induced MASH and fibrosis in Elovl5-/- mice is intricately associated with disruptions in mitochondrial homeostasis, stemming from a profound reshaping of mitochondrial lipids, notably cardiolipins.

Regulatory mechanism of Elovl6 in lipid metabolism, antioxidant capacity, and immune function in Scylla paramamosain revealed by Ap-1

In mammals, elongation of very long-chain fatty acids protein 6 (ELOVL6) play a role in both the elongation of fatty acids and the development of associated inflammation. However, the function and transcriptional regulatory mechanisms of Elovl6 in invertebrates are poorly understood. This study aimed to examine the function of Elovl6 and its transcriptional regulatory mechanism in Scylla paramamosain. RNA interference experiments showed that elovl6 knockdown significantly affected the synthesis and catabolism of hepatopancreatic lipids, leading to an increase in triglyceride levels and saturated fatty acid content, and a decrease in polyunsaturated fatty acid content. Notably, antioxidant capacity and immune function were also impaired, with decreased activity of antioxidant enzymes and immune-related genes. To investigate the transcription regulation of elovl6, a 2212-bp promoter fragment upstream of elovl6 was cloned and characterized. Analysis of the luciferase reporter showed that Ap-1 regulates elovl6 transcription via the -353 to -343 binding site. In vivo injection of the Ap-1 inhibitor T-5224 verified its inhibitory effect on elovl6 expression, with results similar to those of elovl6 knockdown, indicating that Ap-1 regulates lipid metabolism, antioxidant capacity, and immune function via Elovl6.

Oral exposure to high concentrations of polystyrene microplastics alters the intestinal environment and metabolic outcomes in mice

Introduction

Oral exposure to microplastics (MPs) is a global health concern. In our previous study, MPs induced glucose intolerance and non-alcoholic fatty liver disease (NAFLD) under a high-fat diet-induced leaky gut syndrome (LGS). This study aims to evaluate the effects of high concentrations of MP on lipid metabolism under normal dietary conditions and to assess the changes in the intestinal tract resulting from MP exposure.

Methods

C57BL6/J mice were fed a normal diet (ND) without polystyrene MPs (PS-MPs) or with PS-MPs (1000 µg/L or 5000 µg/L) for six weeks. Subsequently, intestinal permeability, gut microbiota, and metabolite levels in the serum, feces, and liver were determined.

Results

Mice fed the ND showed no increase in intestinal permeability in either group. However, high MPs concentrations led to increased serum lipid levels and exacerbated fatty liver function. Oral exposure to MPs did not affect the number of innate lymphoid cells or short-chain fatty acids in the intestine. However, it increased the number of natural killer cells, altered the gut microbiota, induced inflammation, and modulated the expression of genes related to nutrient transport in the intestine. The severity of intestinal disturbance tended to worsen with dose.

Discussion

Despite the absence of LGS, high concentrations of MPs induced dyslipidemia and NAFLD. Oral exposure to MPs triggered intestinal inflammation via natural killer cells, altered the gut microbiota, and modulated nutrient metabolism. Our study highlights the need for environmental measures to reduce oral MPs exposure in the future.

Comparative analysis of the liver transcriptome in the red-eared slider (Trachemys scripta elegans) post exposure to noise

Exposure to noise can cause non-auditory health problems and has been widely studied in mammals such as rats and rabbits. However, the non-auditory effects of noise exposure on reptiles (such as red-eared sliders) remain unclear. In this study, we determined the noise exposure-induced transcriptomic changes in the liver of red-eared slider (Trachemys scripta elegans) using Illumina Novaseq6000 sequencing technology. The transcriptome analysis identified 176 differentially expressed genes (DEGs), which were mainly enriched in lipid metabolism. KEGG analysis showed that by affecting the peroxisome proliferator activated receptor (PPAR) signaling pathway these DEGs increased lipid synthesis and decreased lipid oxidation. The Oil Red O staining results validated our data that noise exposure increased hepatic lipid deposition. Thus, noise exposure may lead to lipid accumulation and toxicity, mitochondrial damage, and accelerated oxidative stress. Our findings provide insights into the molecular process underlying non-auditory damage caused by noise exposure in T. scripta elegans.

Steatotic liver disease induced by TCPOBOP-activated hepatic constitutive androstane receptor: primary and secondary gene responses with links to disease progression

Constitutive androstane receptor (CAR, Nr1i3), a liver nuclear receptor and xenobiotic sensor, induces drug, steroid, and lipid metabolizing enzymes, stimulates liver hypertrophy and hyperplasia, and ultimately, hepatocellular carcinogenesis. The mechanisms linking early CAR responses to later disease development are poorly understood. Here we show that exposure of CD-1 mice to TCPOBOP (1,4-bis[2-(3,5-dichloropyridyloxy)]benzene), a halogenated xenochemical and selective CAR agonist ligand, induces pericentral steatosis marked by hepatic accumulation of cholesterol and neutral lipid, and elevated circulating alanine aminotransferase, indicating hepatocyte damage. TCPOBOP-induced steatosis was weaker in the pericentral region but stronger in the periportal region in females compared with males. Early (1 day) TCPOBOP transcriptional responses were enriched for CAR-bound primary response genes, and for lipogenesis and xenobiotic metabolism and oxidative stress protection pathways; late (2 weeks) TCPOBOP responses included many CAR binding-independent secondary response genes, with enrichment for macrophage activation, immune response, and cytokine and reactive oxygen species production. Late upstream regulators specific to TCPOBOP-exposed male liver were linked to proinflammatory responses and hepatocellular carcinoma progression. TCPOBOP administered weekly to male mice using a high corn oil vehicle induced carbohydrate-responsive transcription factor (MLXIPL)-regulated target genes, dysregulated mitochondrial respiratory and translation regulatory pathways, and induced more advanced liver pathology. Overall, TCPOBOP exposure recapitulates histological and gene expression changes characteristic of emerging steatotic liver disease, including secondary gene responses in liver nonparenchymal cells indicative of transition to a more advanced disease state. Upstream regulators of both the early and late TCPOBOP response genes include novel biomarkers for foreign chemical-induced metabolic dysfunction-associated steatotic liver disease.

Abnormal saturated fatty acids and sphingolipids metabolism in asthma

Recent advances in fatty acid analysis have highlighted the links between lipid disruption and disease development. Lipid abnormalities are well-established risk factors for many of the most common chronic illnesses, and their involvement in asthma is also becoming clear. Here, we review research demonstrating the role of abnormal lipid metabolism in asthma, with a focus on saturated fatty acids and sphingolipids. High levels of palmitic acid, the most abundant saturated fatty acid in the human body, have been found in the airways of asthmatic patients with obesity, and were shown to worsen eosinophilic airway inflammation in asthma model mice on a high-fat diet. Aside from being a building block of longer-chain fatty acids, palmitic acid is also the starting point for de novo synthesis of ceramides, a class of sphingolipids. We outline the three main pathways for the synthesis of ceramides, which have been linked to the severity of asthma and act as precursors for the dynamic lipid mediator sphingosine 1-phosphate (S1P). S1P signaling is involved in allergen-induced eosinophilic inflammation, airway hyperresponsiveness, and immune-cell trafficking. A recent study of mice with mutations for the elongation of very long-chain fatty acid family member 6 (Elovl6), an enzyme that elongates fatty acid chains, has highlighted the potential role of palmitic acid composition, and thus lipid balance, in the pathophysiology of allergic airway inflammation. Elovl6 may be a potential therapeutic target in severe asthma.

Lipidomic Analysis Reveals Alterations in Hepatic FA Profile Associated With MASLD Stage in Patients With Obesity

CONTEXT

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by the intracellular lipid accumulation in hepatocytes. Excess caloric intake and high-fat diets are considered to significantly contribute to MASLD development.

OBJECTIVE

To evaluate the hepatic and serum fatty acid (FA) composition in patients with different stages of MASLD, and their relationship with FA dietary intake and MASLD-related risk factors.

METHODS

This was a case-control study in patients with obesity undergoing bariatric surgery at a university hospital between January 2020 and December 2021. Participants were distributed in 3 groups: no MASLD (n = 26), steatotic liver disease (n = 33), and metabolic dysfunction-associated steatohepatitis (n = 32). Hepatic and serum FA levels were determined by gas chromatography-mass spectrometry. Nutritional status was evaluated using validated food frequency questionnaires. The hepatic expression of genes involved in FA metabolism was analyzed by reverse transcription quantitative polymerase chain reaction.

RESULTS

The hepatic, but not serum, FA profiles were significantly altered in patients with MASLD compared with those without MASLD. No differences were observed in FA intake between the groups. Levels of C16:0, C18:1, and the C18:1/C18:0 ratio were higher, while C18:0 levels and C18:0/C16:0 ratio were lower in patients with MASLD, being significantly different between the 3 groups. Hepatic FA levels and ratios correlated with histopathological diagnosis and other MASLD-related parameters. The expression of genes involved in the FA metabolism was upregulated in patients with MASLD.

CONCLUSION

Alterations in hepatic FA levels in MASLD patients were due to enhancement of de novo lipogenesis in the liver.

Hepatokine ITIH3 protects against hepatic steatosis by downregulating mitochondrial bioenergetics and de novo lipogenesis

Recent studies demonstrate that liver secretory proteins, also known as hepatokines, regulate normal development, obesity, and simple steatosis to non-alcoholic steatohepatitis (NASH) progression. Using a panel of ∼100 diverse inbred strains of mice and a cohort of bariatric surgery patients, we found that one such hepatokine, inter-trypsin inhibitor heavy chain 3 (ITIH3), was progressively lower in severe non-alcoholic fatty liver disease (NAFLD) disease states highlighting an inverse relationship between Itih3/ITIH3 expression and NAFLD severity. Follow-up animal and cell culture models demonstrated that hepatic ITIH3 overexpression lowered liver triglyceride and lipid droplet accumulation, respectively. Conversely, ITIH3 knockdown in mice increased the liver triglyceride in two independent NAFLD models. Mechanistically, ITIH3 reduced mitochondrial respiration and this, in turn, reduced liver triglycerides, via downregulated de novo lipogenesis. This was accompanied by increased STAT1 signaling and Stat3 expression, both of which are known to protect against NAFLD/NASH. Our findings indicate hepatokine ITIH3 as a potential biomarker and/or treatment for NAFLD.

The ELOVL6 homolog in Penaeus vannamei plays a dual role in fatty acid metabolism and immune response

In mammals, elongation of very long chain fatty acid protein 6 (ELOVL6), a key enzyme in long chain fatty acids elongation, has been reported to regulate other metabolism processes and immunity, including inflammation in vertebrates. However, little is currently known about the ELOVL6 homolog in invertebrates, especially its role in immune response. In this study, the ELOVL6 ortholog in Penaeus vannamei (designated PvELOVL6) was cloned and found to have an open reading frame (ORF) of 435 bp and encode a putative protein of 144 amino acids. Transcripts of PvELOVL6 are constitutively expressed in all shrimp tissues tested and induced in the hepatopancreas and hemocytes by Vibrio parahaemolyticus and Streptococcus iniae. Besides, PvELOVL6 knockdown followed by Vibrio parahaemolyticus challenge revealed that PvELOVL6 regulates the expression of several genes involved in fatty acid metabolism and immunity, including PvLGBP, PvLectin, PvMnSOD, PvProPO, PvFABP, PvLipase, PvCOX and PvGPDH. Moreover, transcript levels of PvELOVL6, fatty acids metabolism-related genes (i.e., PvGPDH, PvFABP, PvPERO and PvSPLA2), and immune-related genes (i.e., PvProPO, PvLectin, PvLGBP, PvLysozyme and PvCatalase) increased after silencing of the sterol regulatory element binding protein (PvSREBP). Thus, PvELOVL6 is involved in immune response and regulated by PvSREBP through an unknown mechanism in penaeid shrimp.

Hop-derived Humulinones Reveal Protective Effects in in vitro Models of Hepatic Steatosis, Inflammation and Fibrosis

Nonalcoholic fatty liver disease (NAFLD) is emerging as leading cause of liver disease worldwide. Specific pharmacologic therapy for NAFLD is a major unmet medical need. Recently, iso-alpha acids, hop-derived bitter compounds in beer, have been shown to beneficially affect NAFLD pathology. Humulinones are further hop derived bitter acids particularly found in modern styles of beer. So far, biological effects of humulinones have been unknown. Here, we investigated the effect of humulinones in in vitro models for hepatic steatosis, inflammation and fibrosis. Humulinones dose-dependently inhibited fatty acid induced lipid accumulation in primary human hepatocytes. Humulinones reduced the expression of fatty acid uptake transporter CD36 and key enzymes of (de novo) lipid synthesis. Conversely, humulinones increased the expression of FABP1, CPT1 and ACOX1, indicative for increased lipid combustion. Furthermore, humulinones ameliorated steatosis induced pro-inflammatory gene expression. Furthermore, humulinones significantly reduced the expression of pro-inflammatory and pro-fibrogenic factors in control as well as lipopolysaccharide treated activated hepatic stellate cells, which play a key role in hepatic fibrosis. In conclusion, humulinones beneficially affect different pathophysiological steps of NAFLD. Our data suggest humulinones as promising therapeutic agents for the prevention and treatment of NAFLD.

The oleic/palmitic acid imbalance in exosomes isolated from NAFLD patients induces necroptosis of liver cells via the elongase-6/RIP-1 pathway

Excessive toxic lipid accumulation in hepatocytes underlies the development of non-alcoholic fatty liver disease (NAFLD), phenotypically characterized by necrosis and steato-fibrosis, whose molecular mechanism is not yet fully understood. Patients with NAFLD display an imbalanced palmitic (PA) to oleic acid (OA) ratio. Moreover, increasing experimental evidence points out a relevant involvement of the exosomal content in disease progression. Aim of the study was to highlight the PA/OA imbalance within circulating exosomes, the subsequent intracellular alterations, and the impact on NALFD. Liver cells were challenged with exosomes isolated from both healthy subjects and NAFLD patients. The exosomal PA/OA ratio was artificially modified, and biological effects were evaluated. A NAFLD-derived exosomal PA/OA imbalance impacts liver cell cycle and cell viability. OA-modified NAFLD-derived exosomes restored cellular viability and proliferation, whereas the inclusion of PA into healthy subjects-derived exosomes negatively affected cell viability. Moreover, while OA reduced the phosphorylation and activation of the necroptosis marker, Receptor-interacting protein 1 (phospho-RIP-1), PA induced the opposite outcome, alongside increased levels of stress fibers, such as vimentin and fibronectin. Administration of NAFLD-derived exosomes led to increased expression of Elongase 6 (ELOVL6), Stearoyl-CoA desaturase 1 (SCD1), Tumor necrosis factor α (TNF-α), Mixed-lineage-kinase-domain-like-protein (MLKL) and RIP-1 in the hepatocytes, comparable to mRNA levels in the hepatocytes of NAFLD patients reported in the Gene Expression Omnibus (GEO) database. Genetic and pharmacological abrogation of ELOVL6 elicited a reduced expression of downstream molecules TNF-α, phospho-RIP-1, and phospho-MLKL upon administration of NAFLD-derived exosomes. Lastly, mice fed with high-fat diet exhibited higher phospho-RIP-1 than mice fed with control diet. Targeting the Elongase 6-RIP-1 signaling pathway offers a novel therapeutic approach for the treatment of the NALFD-induced exosomal PA/OA imbalance.

Irisin Ameliorated Skeletal Muscle Atrophy by Inhibiting Fatty Acid Oxidation and Pyroptosis Induced by Palmitic Acid in Chronic Kidney Disease

INTRODUCTION

Protein-energy waste (PEW) is a common complication in patients with chronic kidney disease (CKD), among which skeletal muscle atrophy is one of the most important clinical features of PEW. Pyroptosis is a type of proinflammatory, programmed cell death associated with skeletal muscle disease. Irisin, as a novel myokine, has attracted extensive attention for its protective role in the complications associated with CKD, but its role in muscle atrophy in CKD is unclear.

METHODS

Palmitic acid (PA)-induced muscular atrophy was evaluated by a reduction in C2C12 myotube diameter. Muscle atrophy model was established in male C57BL/6J mice treated with 0.2% adenine for 4 weeks and then fed a 45% high-fat diet. Blood urea nitrogen and creatinine levels, body and muscle weight, and muscle histology were assessed. The expression of carnitine palmitoyltransferase 1A (CPT1A) and pyroptosis-related protein was analysed by Western blots or immunohistochemistry. The release of IL-1β was detected by enzyme-linked immunosorbent assay.

RESULTS

In this study, we showed that PA-induced muscular atrophy manifested as a reduction in C2C12 myotube diameter. During this process, PA can also induce pyroptosis, as shown by the upregulation of NLRP3, cleaved caspase-1 and GSDMD-N expression and the increased IL-1β release and PI-positive cell rate. Inhibition of caspase-1 or NLRP3 attenuated PA-induced pyroptosis and myotube atrophy in C2C12 cells. Importantly, irisin treatment significantly ameliorated PA-induced skeletal muscle pyroptosis and atrophy. In terms of mechanism, PA upregulated CPT1A, a key enzyme of fatty acid oxidation (FAO), and irisin attenuated this effect, which was consistent with etomoxir (CPT1A inhibitor) treatment. Moreover, irisin improved skeletal muscle atrophy and pyroptosis in adenine-induced mice by regulating FAO.

CONCLUSION

Our study firstly verifies that pyroptosis is a novel mechanism of skeletal muscle atrophy in CKD. Irisin ameliorates skeletal muscle atrophy by inhibiting FAO and pyroptosis in CKD, and irisin may be developed as a potential therapeutic agent for the treatment of muscle wasting in CKD patients.

ELOVL6 is associated with immunosuppression in lung adenocarcinoma through bioinformatics analysis

The aim of this paper was to reveal the correlation between the expression of ELOVL fatty acid elongase 6 (ELOVL6) gene in lung adenocarcinoma (LUAD) and its clinical significance, immune cell infiltration level and prognosis. Expression profile data of ELOVL6 mRNA were collected from the cancer genome atlas database to analyze the differences in ELOVL6 mRNA expression in LUAD tissues and normal lung tissues, and to analyze the correlation between ELOVL6 and information on clinicopathological features. Based on TIMER database, TISDIB database and GEPIA2 database, the correlation between ELOVL6 expression and tumor immune cell infiltration in LUAD was analyzed. Gene ontology and Kyoto encyclopedia of genes and genomes enrichment analyses of ELOVL6-related co-expressed genes were performed to identify the involved signaling pathways and to construct their co-expressed gene protein interaction networks. Drugs affected by ELOVL6 expression were screened based on the Cell Miner database. These findings suggest that ELOVL6 plays an important role in the course of LUAD, and the expression level of this gene has a close relationship with clinicopathological characteristics and survival prognosis, and has the potential to become a prognostic marker and therapeutic target for LUAD.

Cloning and expression characterization of elongation of very long-chain fatty acids protein 6 (elovl6) with dietary fatty acids, ambient salinity and starvation stress in Scylla paramamosain

Introduction: Elongation of very long-chain fatty acids protein 6 (ELOVL6) played crucial roles in regulating energy expenditure and fatty acid metabolism. Many studies have performed to investigate the physiological roles and regulatory mechanisms of elovl6 in fish and animals, while few studies were reported in crustaceans. Methods: Here we reported on the molecular cloning, tissue distribution and expression profiles in response to dietary fatty acids, ambient salinity and starvation stress in Scylla paramamosain by using rapid amplification of cDNA ends (RACE) and quantitative real-time PCR. Results: Three elovl6 isoforms (named elovl6a, elovl6b and elovl6c) were isolated from S. paramamosain in the present study. The complete sequence of elovl6a was 1345 bp, the full-length sequence of elovl6b was 1419 bp, and the obtained elovl6c sequence was 1375 bp in full length. The elovl6a, elovl6b and elovl6c encoded 287, 329 and 301 amino acids respectively, and exhibited the typical structural features of ELOVL protein family members. Phylogenetic analysis showed that the ELOVL6a from S. paramamosain clustered most closely to ELOVL6 from Portunus trituberculatus and Eriocheir sinensis, while the ELOVL6b and ELOVL6c from S. paramamosain gathered alone into a single branch. Quantitative real-time PCR exhibited that the relatively abundant expression of elovl6b was observed in intestine and stomach, and the elovl6a and elovl6c were highly expressed in hepatopancreas. In addition, studies found that replacing fish oil with soybean oil could significantly increase the transcriptional levels of three elovl6 in hepatopancreas of S. paramamosain, and the expression of elovl6a and elovl6c in hepatopancreas were more sensitive to dietary fatty acids than the elovl6b. Compared with the normal sea water group (27‰), the expression of sterol-regulatory element binding protein1c (srebp-1), elovl6a, elovl6b and elovl6c were upregulated in the low salinity groups, particularly in 7‰. On the contrary, the starvation stress suppressed the expression of srebp-1, elovl6a, elovl6b and elovl6c. Discussion: These results may contribute to understand the functions of elovl6 in fatty acid synthesis and regulatory mechanisms in crustaceans.

Tumor purity-associated genes influence hepatocellular carcinoma prognosis and tumor microenvironment

Introduction

Tumor purity takes on critical significance to the progression of solid tumors. The aim of this study was at exploring potential prognostic genes correlated with tumor purity in hepatocellular carcinoma (HCC) by bioinformatics analysis.

Methods

The ESTIMATE algorithm was applied for determining the tumor purity of HCC samples from The Cancer Genome Atlas (TCGA). The tumor purity-associated genes with differential expression (DEGs) were identified based on overlap analysis, weighted gene co-expression network analysis (WGCNA), and differential expression analysis. The prognostic genes were identified in terms of the prognostic model construction based on the Kaplan-Meier (K-M) survival analysis and Least Absolute Shrinkage and Selection Operator (LASSO) regression analyses. The expression of the above-described genes was further validated by the GSE105130 dataset from the Gene Expression Omnibus (GEO) database. We also characterized the clinical and immunophenotypes of prognostic genes. Gene set enrichment analysis (GSEA) was carried out for exploring the biological signaling pathway.

Results

A total of 26 tumor purity-associated DEGs were identified, which were involved in biological processes such as immune/inflammatory responses and fatty acid elongation. Ultimately, we identified ADCK3, HK3, and PPT1 as the prognostic genes for HCC. Moreover, HCC patients exhibiting higher ADCK3 expression and lower HK3 and PPT1 expressions had a better prognosis. Furthermore, high HK3 and PPT1 expressions and low ADCK3 expression resulted in high tumor purity, high immune score, high stromal score, and high ESTIMATE score. GSEA showed that the abovementioned prognostic genes showed a significant correlation with immune-inflammatory response, tumor growth, and fatty acid production/degradation.

Discussion

In conclusion, this study identified novel predictive biomarkers (ADCK3, HK3, and PPT1) and studied the underlying molecular mechanisms of HCC pathology initially.

Physiological and pathological roles of lipogenesis

Lipids are essential metabolites, which function as energy sources, structural components and signalling mediators. Most cells are able to convert carbohydrates into fatty acids, which are often converted into neutral lipids for storage in the form of lipid droplets. Accumulating evidence suggests that lipogenesis plays a crucial role not only in metabolic tissues for systemic energy homoeostasis but also in immune and nervous systems for their proliferation, differentiation and even pathophysiological roles. Thus, excessive or insufficient lipogenesis is closely associated with aberrations in lipid homoeostasis, potentially leading to pathological consequences, such as dyslipidaemia, diabetes, fatty liver, autoimmune diseases, neurodegenerative diseases and cancers. For systemic energy homoeostasis, multiple enzymes involved in lipogenesis are tightly controlled by transcriptional and post-translational modifications. In this Review, we discuss recent findings regarding the regulatory mechanisms, physiological roles and pathological importance of lipogenesis in multiple tissues such as adipose tissue and the liver, as well as the immune and nervous systems. Furthermore, we briefly introduce the therapeutic implications of lipogenesis modulation.

PPARα activation partially drives NAFLD development in liver-specific Hnf4a-null mice

HNF4α regulates various genes to maintain liver function. There have been reports linking HNF4α expression to the development of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis. In this study, liver-specific Hnf4a-deficient mice (Hnf4aΔHep mice) developed hepatosteatosis and liver fibrosis, and they were found to have difficulty utilizing glucose. In Hnf4aΔHep mice, the expression of fatty acid oxidation-related genes, which are PPARα target genes, was increased in contrast to the decreased expression of PPARα, suggesting that Hnf4aΔHep mice take up more lipids in the liver instead of glucose. Furthermore, Hnf4aΔHep/Ppara-/- mice, which are simultaneously deficient in HNF4α and PPARα, showed improved hepatosteatosis and fibrosis. Increased C18:1 and C18:1/C18:0 ratio was observed in the livers of Hnf4aΔHep mice, and the transactivation of PPARα target gene was induced by C18:1. When the C18:1/C18:0 ratio was close to that of Hnf4aΔHep mouse liver, a significant increase in transactivation was observed. In addition, the expression of Pgc1a, a coactivator of PPARs, was increased, suggesting that elevated C18:1 and Pgc1a expression could contribute to PPARα activation in Hnf4aΔHep mice. These insights may contribute to the development of new diagnostic and therapeutic approaches for NAFLD by focusing on the HNF4α and PPARα signaling cascade.

Endotoxin Tolerance Acquisition and Altered Hepatic Fatty Acid Profile in Aged Mice

(1) Background: Aging is linked to an altered immune response and metabolism. Inflammatory conditions, such as sepsis, COVID-19, and steatohepatitis are more prevalent in the elderly and steatosis is linked both to severe COVID-19 and sepsis. We hypothesized that aging is linked to a loss of endotoxin tolerance, which normally protects the host from excessive inflammation, and that this is accompanied by elevated levels of hepatic lipids. (2) Methods: An in vivo lipopolysaccharide (LPS) tolerance model in young and old mice was used and the cytokine serum levels were measured by ELISA. Cytokine and toll-like receptor gene expression was determined by qPCR in the lungs and the liver; hepatic fatty acid composition was assessed by GC–MS. (3) Results: The old mice showed a distinct potential for endotoxin tolerance as suggested by the serum cytokine levels and gene expression in the lung tissue. Endotoxin tolerance was less pronounced in the livers of the aged mice. However, the fatty acid composition strongly differed in the liver tissues of the young and old mice with a distinct change in the ratio of C18 to C16 fatty acids. (4) Conclusions: Endotoxin tolerance is maintained in advanced age, but changes in the metabolic tissue homeostasis may lead to an altered immune response in old individuals.

Albumin-fused long-acting FGF21 analogue for the treatment of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) currently affects about 25% of the world's population, and the numbers continue to rise as the number of obese patients increases. However, there are currently no approved treatments for NAFLD. This study reports on the evaluation of the therapeutic effect of a recombinant human serum albumin-fibroblast growth factor 21 analogue fusion protein (HSA-FGF21) on the pathology of NAFLD that was induced by using two high-fat diets (HFD), HFD-60 and STHD-01. The HFD-60-induced NAFLD model mice with obesity, insulin resistance, dyslipidemia and hepatic lipid accumulation were treated with HSA-FGF21 three times per week for 4 weeks starting at 12 weeks after the HFD-60 feeding. The administration of HSA-FGF21 suppressed the increased body weight, improved hyperglycemia, hyperinsulinemia, and showed a decreased accumulation of plasma lipid and hepatic lipid levels. The elevation of C16:0, C18:0 and C18:1 fatty acids in the liver that were observed in the HFD-60 group was recovered by the HSA-FGF21 administration. The increased expression levels of the hepatic fatty acid uptake receptor (CD36) and fatty acid synthase (SREBP-1c, FAS, SCD-1, Elovl6) were also suppressed. In adipose tissue, HSA-FGF21 caused an improved adipocyte hypertrophy, a decrease in the levels of inflammatory cytokines and induced the expression of adiponectin and thermogenic factors. The administration of HSA-FGF21 to the STHD-01-induced NAFLD model mice resulted in suppressed plasma ALT and AST levels, oxidative stress, inflammatory cell infiltration and fibrosis. Together, HSA-FGF21 has some potential for use as a therapeutic agent for the treatment of NAFLD.

Effects of Different Vegetable Oils on the Nonalcoholic Fatty Liver Disease in C57/BL Mice

Background

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disorder, affecting 22-28% of the adult population and more than 50% of obese people all over the world. Modulation of the fatty acids in diet as a means of prevention against nonalcoholic fatty liver disease in animal models (NAFLD) remains unclear. The treatment of NAFLD has not been described in specific guidelines so far. Thus, the justification for the study is to check modifications in macronutrients composition, fatty acids, in particular, play a significant role in the treatment of NAFLD regardless of weight loss.

Aim

To investigate different vegetable oils in prevention and progression of NAFLD in animal models.

Methods

For the experiment were used fifty C57BL/6J mice male fed with high fat and fructose diet (HFD) to induce the NAFLD status and they received different commercial vegetable oils for 16 weeks to prevent steatosis. Liver steatosis and oxidative stress parameters were analyzed using biochemical and histological methods. Fatty acids profile in the oils and in the liver samples was obtained.

Results

The high fat and fructose diet led to obesity and the vegetable oils offered were effective in maintaining body weight similar to the control group. At the end of the experiment (16 weeks), the HFHFr group had a greater body weight compared to control and treated groups (HFHFr: 44.20 ± 2.34 g/animal vs. control: 34.80 ± 3.45 g/animal; p < 0.001; HFHFr/OL: 35.40 ± 4.19 g/animal; HFHFr/C: 36.10 ± 3.92 g/animal; HFHFr/S: 36.25 ± 5.70 g/animal; p < 0.01). Furthermore, the HFD diet has caused an increase in total liver fat compared to control (p < 0.01). Among the treated groups, the animals receiving canola oil showed a reduction of hepatic and retroperitoneal fat (p < 0.05). These biochemical levels were positively correlated with the hepatic histology findings. Hepatic levels of omega-3 decreased in the olive oil and high fat diet groups compared to the control group, whereas these levels increased in the groups receiving canola and soybean oil compared to control and the high fat groups.

Conclusion

In conclusion, the commercial vegetable oils either contributed to the prevention or reduction of induced nonalcoholic fatty liver with high fat and fructose diet, especially canola oil.

Knockout of secretin ameliorates biliary and liver phenotypes during alcohol-induced hepatotoxicity

BACKGROUND

Alcohol-related liver disease (ALD) is characterized by ductular reaction (DR), liver inflammation, steatosis, fibrosis, and cirrhosis. The secretin (Sct)/secretin receptor (SR) axis (expressed only by cholangiocytes) regulates liver phenotypes in cholestasis. We evaluated the role of Sct signaling on ALD phenotypes.

METHODS

We used male wild-type and Sct-/- mice fed a control diet (CD) or ethanol (EtOH) for 8 wk. Changes in liver phenotypes were measured in mice, female/male healthy controls, and patients with alcoholic cirrhosis. Since Cyp4a10 and Cyp4a11/22 regulate EtOH liver metabolism, we measured their expression in mouse/human liver. We evaluated: (i) the immunoreactivity of the lipogenesis enzyme elongation of very-long-chain fatty acids 1 (Elovl, mainly expressed by hepatocytes) in mouse/human liver sections by immunostaining; (ii) the expression of miR-125b (that is downregulated in cholestasis by Sct) in mouse liver by qPCR; and (iii) total bile acid (BA) levels in mouse liver by enzymatic assay, and the mRNA expression of genes regulating BA synthesis (cholesterol 7a-hydroxylase, Cyp27a1, 12a-hydroxylase, Cyp8b1, and oxysterol 7a-hydroxylase, Cyp7b11) and transport (bile salt export pump, Bsep, Na+-taurocholate cotransporting polypeptide, NTCP, and the organic solute transporter alpha (OSTa) in mouse liver by qPCR.

RESULTS

In EtOH-fed WT mice there was increased biliary and liver damage compared to control mice, but decreased miR-125b expression, phenotypes that were blunted in EtOH-fed Sct-/- mice. The expression of Cyp4a10 increased in cholangiocytes and hepatocytes from EtOH-fed WT compared to control mice but decreased in EtOH-fed Sct-/- mice. There was increased immunoreactivity of Cyp4a11/22 in patients with alcoholic cirrhosis compared to controls. The expression of miR-125b decreased in EtOH-fed WT mice but returned at normal values in EtOH-fed Sct-/- mice. Elovl1 immunoreactivity increased in patients with alcoholic cirrhosis compared to controls. There was no difference in BA levels between WT mice fed CD or EtOH; BA levels decreased in EtOH-fed Sct-/- compared to EtOH-fed WT mice. There was increased expression of Cyp27a1, Cyp8b1, Cyp7b1, Bsep, NTCP and Osta in total liver from EtOH-fed WT compared to control mice, which decreased in EtOH-fed Sct-/- compared to EtOH-fed WT mice.

CONCLUSIONS

Targeting Sct/SR signaling may be important for modulating ALD phenotypes.

Identification of key microRNAs regulating ELOVL6 and glioblastoma tumorigenesis

ELOVL fatty acid elongase 6 (ELOVL6) controls cellular fatty acid (FA) composition by catalyzing the elongation of palmitate (C16:0) to stearate (C18:0) and palmitoleate (C16:1n-7) to vaccinate (C18:1n-7). Although the transcriptional regulation of ELOVL6 has been well studied, the post-transcriptional regulation of ELOVL6 is not fully understood. Therefore, this study aims to evaluate the role of microRNAs (miRNAs) in regulating human ELOVL6. Bioinformatic analysis identified five putative miRNAs: miR-135b-5p, miR-135a-5p, miR-125a-5p, miR-125b-5p, and miR-22-3p, which potentially bind ELOVL6 3'-untranslated region (UTR). Results from dual-luciferase assays revealed that these miRNAs downregulate ELOVL6 by directly interacting with the 3'-UTR of ELOVL6 mRNA. Moreover, miR-135b-5p and miR-135a-5p suppress cell proliferation and migration in glioblastoma multiforme cells by inhibiting ELOVL6 at the mRNA and protein levels. Taken together, our results provide novel regulatory mechanisms for ELOVL6 at the post-transcriptional level and identify potential candidates for the treatment of patients with glioblastoma multiforme.

ELOVL6 deficiency aggravates allergic airway inflammation through the ceramide-S1P pathway in mice

BACKGROUND

Elongation of very-long-chain fatty acids protein 6 (ELOVL6), an enzyme regulating elongation of saturated and monounsaturated fatty acids with C12 to C16 to those with C18, has been recently indicated to affect various immune and inflammatory responses; however, the precise process by which ELOVL6-related lipid dysregulation affects allergic airway inflammation is unclear.

OBJECTIVES

This study sought to evaluate the biological roles of ELOVL6 in allergic airway responses and investigate whether regulating lipid composition in the airways could be an alternative treatment for asthma.

METHODS

Expressions of ELOVL6 and other isoforms were examined in the airways of patients who are severely asthmatic and in mouse models of asthma. Wild-type and ELOVL6-deficient (Elovl6^-/-) mice were analyzed for ovalbumin-induced, and also for house dust mite-induced, allergic airway inflammation by cell biological and biochemical approaches.

RESULTS

ELOVL6 expression was downregulated in the bronchial epithelium of patients who are severely asthmatic compared with controls. In asthmatic mice, ELOVL6 deficiency led to enhanced airway inflammation in which lymphocyte egress from lymph nodes was increased, and both type 2 and non-type 2 immune responses were upregulated. Lipidomic profiling revealed that the levels of palmitic acid, ceramides, and sphingosine-1-phosphate were higher in the lungs of ovalbumin-immunized Elovl6^-/- mice compared with those of wild-type mice, while the aggravated airway inflammation was ameliorated by treatment with fumonisin B1 or DL-threo-dihydrosphingosine, inhibitors of ceramide synthase and sphingosine kinase, respectively.

CONCLUSIONS

This study illustrates a crucial role for ELOVL6 in controlling allergic airway inflammation via regulation of fatty acid composition and ceramide-sphingosine-1-phosphate biosynthesis and indicates that ELOVL6 may be a novel therapeutic target for asthma.

Apolipoprotein H: a novel regulator of fat accumulation in duck myoblasts

Apolipoprotein H (APOH) primarily engages in fat metabolism and inflammatory disease response. This study aimed to investigate the effects of APOH on fat synthesis in duck myoblasts (CS2s) by APOH overexpression and knockdown. CS2s overexpressing APOH showed enhanced triglyceride (TG) and cholesterol (CHOL) contents and elevated the mRNA and protein expression of AKT serine/threonine kinase 1 (AKT1), ELOVL fatty acid elongase 6 (ELOVL6), and acetyl-CoA carboxylase 1 (ACC1) while reducing the expression of protein kinase AMP-activated catalytic subunit alpha 1 (AMPK), peroxisome proliferator activated receptor gamma (PPARG), acyl-CoA synthetase long chain family member 1 (ACSL1), and lipoprotein lipase (LPL). The results showed that knockdown of APOH in CS2s reduced the content of TG and CHOL, reduced the expression of ACC1, ELOVL6, and AKT1, and increased the gene and protein expression of PPARG, LPL, ACSL1, and AMPK. Our results showed that APOH affected lipid deposition in myoblasts by inhibiting fatty acid beta-oxidation and promoting fatty acid biosynthesis by regulating the expression of the AKT/AMPK pathway. This study provides the necessary basic information for the role of APOH in fat accumulation in duck myoblasts for the first time and enables researchers to study the genes related to fat deposition in meat ducks in a new direction.

Uncovering the mechanism of Huanglian-Wuzhuyu herb pair in treating nonalcoholic steatohepatitis based on network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

The Huanglian-Wuzhuyu herb pair (HWHP) is a classic Chinese herbal formula consisting of the root of Coptis chinensis Franch and dried, nearly mature scented fruit of Tetradium ruticarpum (A.Juss.) T.G.Hartley. It is widely utilized to treat gastrointestinal and liver diseases such as diarrhea, dysentery, cholestasis, hepatocellular carcinoma, and nonalcoholic steatohepatitis (NASH). However, the mechanism of HWHP in treating NASH remains poorly understood.

AIM OF THE STUDY

This study investigated the mechanisms of HWHP in NASH treatment via network pharmacology and validated the results through in vivo experiment using mouse models.

MATERIALS AND METHODS

The compounds and targets corresponding to the active ingredients of HWHP were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) database. The genes associated with NASH were obtained from the DisGeNET database. Cytoscape software was employed to construct a "drug-ingredient-target-disease" network. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were employed to analyze the related signaling pathways affected by HWHP. Moreover, AutoDock software was used to assess the potential binding affinity between the key targets of the hub pathway and the bioactive compounds. Subsequently, in vivo experiment was conducted to verify the findings of network pharmacology.

RESULTS

A total of 41 active compounds and 198 targets of HWHP were screened, of which 51 common targets were related to NASH. GO functional enrichment analysis revealed that HWHP may affect NASH by modulating inflammatory response. KEGG pathway enrichment suggested that the NOD-like receptor (NLR) signaling pathway may play an important role in treating NASH. Molecular docking results demonstrated that most HWHP components were successfully docked to NLRP3 with good binding energy. In vivo experiments revealed that HWHP alleviated liver inflammation, improved liver steatosis, reduced TC, TG, LDL-C, ALT, and AST, decreased mRNA expressions of IL-6, IL-18, and TNF-α in the liver, and lowered the expressions of NLRP3, pro-IL-1β, and ASC protein. Also, immunohistochemical findings presented downregulation of caspase-1 and IL-1β by HWHP.

CONCLUSIONS

The results disclosed that HWHP ameliorates NASH in mice by reducing inflammation and liver steatosis via inhibition of NLRP3 inflammasome. This study revealed the mechanism of HWHP in treating NASH through experiments.

Salvianolic acid B ameliorates non-alcoholic fatty liver disease by inhibiting hepatic lipid accumulation and NLRP3 inflammasome in ob/ob mice

Non-alcoholic fatty liver disease (NAFLD) has high occurrence in the global world, which poses serious threats to human health. Salvianolic acid B (SalB), an extract of the root of Salvia miltiorrhiza, has the protective effect on metabolic homeostasis. However, the mechanism is still unknown. In this study, we used ob/ob mice, a model of NAFLD, to explore the hepatoprotective effects of SalB. The results showed that SalB significantly reduced the body weights and liver weights, and ameliorated plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), hepatic free fatty acid (FFA), total cholesterol (TC) levels, and hepatic TG and TC levels in ob/ob mice. SalB reduced the number of lipid droplets and inhibited hepatic lipogenesis by regulating peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FASN), stearoyl-Co A desaturase 1 (SCD1), and cluster of differentiation 36 (CD36). Compared to ob/ob mice, the lower expressions of the pro-inflammatory cytokines, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and F4/80, were observed after SalB treatment. Importantly, SalB treatment inhibited the activation of NLRP3 inflammasome and reduced the severity of liver inflammation. Our findings suggested that SalB improved NAFLD pathology in ob/ob mice by reducing hepatic lipid accumulation and NLRP3 inflammasome activation, which might be the potential hepatoprotective mechanism of SalB.

Effects of HIV Infection in Plasma Free Fatty Acid Profiles among People with Non-Alcoholic Fatty Liver Disease

Despite its high prevalence, the mechanisms underlying non-alcoholic fatty liver disease (NAFLD) in people living with HIV (PLWH) are still unclear. In this prospective cohort study, we aim to evaluate differences in plasma fatty acid profiles between HIV-infected and HIV-uninfected participants with NAFLD. We included participants diagnosed with NAFLD, both HIV-infected and HIV-uninfected. Fatty acid methyl esters were measured from plasma samples. Ratios ([product]/[substrate]) were used to estimate desaturases and elongases activity. We used linear regression for adjusted analyses. We included 31 PLWH and 22 HIV-uninfected controls. We did not find differences in the sum of different types of FA or in FA with a greater presence of plasma. However, there were significant differences in the distribution of some FA, with higher concentrations of ALA, trans-palmitoleic, and behenic acids, and a lower concentration of lignoceric acid in PLWH. PLWH had lower C24:0/C22:0 and C16:0/C14:0 ratios, which estimates the activity of elongases ELOVL1 and ELOVL6. Both groups had similar fatty acid distribution, despite differences in traditional risk factors. PLWH had a lower proportion of specific ratios that estimate ELOVL1 and ELOVL6 activity, which had been previously described for other inflammatory conditions, such as psoriasis.

Early-life exposure to bisphenol A induces dysregulation of lipid homeostasis by the upregulation of SCD1 in male mice

Exposure of Bisphenol A (BPA) is closely associated with an increased prevalence of obesity-related metabolic syndrome. However, the potential mechanism of BPA-induced adipogenesis remains to be fully elucidated. Herein, potential mechanisms of BPA-induced adipogenesis in 3T3-L1 preadipocytes were evaluated using RNA-Seq. Then, using an early-life BPA exposure model, we further evaluated the effects of BPA exposure on lipid and glucose homeostasis. The results showed that lipid content in 3T3-L1 adipocytes was significantly increased after BPA exposure (p < 0.01) and male C57BL/6 mice with the dose of 500 μg/kg/day BPA by once-a-day oral administration for 8 weeks displayed a NAFLD-like phenotype. RNA-Seq analysis of preadipocytes showed that BPA exposure affected multiple biological processes including glycosphingolipid biosynthesis, regulation of lipolysis in adipocytes, PPAR signaling pathway and fatty acid metabolism. The dysregulation in a series of genes of mice was associated to de novo lipogenesis and lipid transport, which was linked to obesity. Importantly, we also found a significant expression increase of stearoyl-CoA desaturase 1 (SCD1) and a significant decrease of apolipoprotein D (APOD) in both fat (p < 0.01) and livers (p < 0.01) of male mice. Besides, the dysregulation of pro-inflammatory genes (TNF-α,IL-6 and SAA3) showed that BPA exposure promoted progression of hepatic inflammation. In conclusion, this study elucidated a novel mechanism in which obesity associated with BPA exposure by targeting SCD1. Exposure to BPA should be carefully examined in the chronic liver metabolic diseases.

Estimated Elovl6 and delta-5 desaturase activities might represent potential markers for insulin resistance in Japanese adults

PURPOSE

Results from a recent study indicated that lower stearic acid/palmitic acid (SA/PA) and arachidonic acid/dihomo-γ-linolenic acid (AA/DGLA) ratios were associated with metabolically unhealthy obesity. However, this has not been extensively studied in the Japanese population.

METHODS

We recruited 291 Japanese subjects with serum free fatty acid profiles undergoing health examinations. Whole serum desaturase activity was estimated as the product: precursor ratio -SA/PA ratio for elongation of long-chain fatty acid family member 6 (Elovl6) and AA/DGLA for delta-5 desaturase (D5D). The determinants of Elovl6 and D5D activity were investigated using multiple regression analyses.

RESULTS

The Elovl6 and D5D activities exhibited a negative correlation with the logmatic-transformed TG/HDL-C ratio and TyG index. Multiple regression analyses revealed that the TG/HDL-C ratio and TyG index were negatively associated with Elovl6 and D5D activities. Most atherogenic markers were worse in the low Elovl6 or D5D activity group than in the high Elovl6 or D5D activity group. When study subjects were further stratified by TG levels, most atherogenic markers were the worst in the highest TG group in either the lowest Elovl6 or lowest D5D activity groups.

CONCLUSION

The estimated Elovl6 and D5D activities might be useful markers of insulin resistance in Japanese subjects.

Influence of the nutritional status and oxidative stress in the desaturation and elongation of n-3 and n-6 polyunsaturated fatty acids: Impact on non-alcoholic fatty liver disease

Polyunsaturated fatty acids (PUFA) play essential roles in cell membrane structure and physiological processes including signal transduction, cellular metabolism and tissue homeostasis to combat diseases. PUFA are either consumed from food or synthesized by enzymatic desaturation, elongation and peroxisomal β-oxidation. The nutritionally essential precursors α-linolenic acid (C18:3n-3; ALA) and linoleic acid (C18:2n-6; LA) are subjected to desaturation by Δ6D/Δ5D desaturases and elongation by elongases 2/5, enzymes that are induced by insulin and repressed by PUFA. Maintaining an optimally low n-6/n-3 PUFA ratio is linked to prevention of the development of several diseases, including nonalcoholic fatty liver disease (NAFLD) that is characterized by depletion of PUFA promoting hepatic steatosis and inflammation. In this context, supplementation with n-3 PUFA revealed significant lowering of hepatic steatosis in obese patients, whereas prevention of fatty liver by high-fat diet in mice is observed in n-3 PUFA and hydroxytyrosol co-administration. The aim of this work is to review the role of nutritional status and nutrient availability on markers of PUFA biosynthesis. In addition, the impact of oxidative stress developed as a result of NAFLD, a redox imbalance that may alter the expression and activity of the enzymes involved, and diminished n-3 PUFA levels by free-radical dependent peroxidation processes will be discussed.

RNF43/ZNRF3 loss predisposes to hepatocellular-carcinoma by impairing liver regeneration and altering the liver lipid metabolic ground-state

RNF43/ZNRF3 negatively regulate WNT signalling. Both genes are mutated in several types of cancers, however, their contribution to liver disease is unknown. Here we describe that hepatocyte-specific loss of Rnf43/Znrf3 results in steatohepatitis and in increase in unsaturated lipids, in the absence of dietary fat supplementation. Upon injury, Rnf43/Znrf3 deletion results in defective hepatocyte regeneration and liver cancer, caused by an imbalance between differentiation/proliferation. Using hepatocyte-, hepatoblast- and ductal cell-derived organoids we demonstrate that the differentiation defects and lipid alterations are, in part, cell-autonomous. Interestingly, ZNRF3 mutant liver cancer patients present poorer prognosis, altered hepatic lipid metabolism and steatohepatitis/NASH signatures. Our results imply that RNF43/ZNRF3 predispose to liver cancer by controlling the proliferative/differentiation and lipid metabolic state of hepatocytes. Both mechanisms combined facilitate the progression towards malignancy. Our findings might aid on the management of those RNF43/ZNRF3 mutated individuals at risk of developing fatty liver and/or liver cancer.

Diurnal variations of triglyceride accumulation in mouse and bovine adipocyte-derived cell lines

Several studies have suggested a strong interaction between the circadian clock and lipid metabolism in mammals. The circadian clock is driven by endogenous cyclic gene expression patterns, commonly referred to as clock genes, and transcription-translation negative feedback loops. Clock genes regulate the transcription of some lipid metabolism-related genes; however, the relationship between the circadian clock and triglyceride (TG) accumulation at the cellular level remains unclear. Here, we evaluated rhythms of intracellular TG accumulation levels as well as the expression of clock genes and lipid metabolism-related genes for 54 h in mouse and bovine adipose-derived cell cultures. To the best of our knowledge, this study represents the first report demonstrating that TG accumulation exhibits diurnal variations, with the pattern differing among cell types. Furthermore, we found that expression of clock genes and corresponding lipid metabolism-related genes exhibited circadian rhythms. Our results suggest that the cellular clock regulates lipid metabolism-related genes to relate circadian rhythms of TG accumulation in each cell type. We anticipate that the amount of fat stored depends on the timing of the supply of glucose-the precursor of fat. The findings of this study will contribute to the advancement of chrono-nutrition.

Pyroptosis: Mechanisms and Links with Fibrosis

Fibrosis is responsible for approximately 45% of deaths in the industrialized world and has been a major global healthcare burden. Excessive fibrosis is the primary cause of organ failure. However, there are currently no approved drugs available for the prevention or treatment of fibrosis-related diseases. It has become evident that fibrosis is characterized by inflammation. In a large number of studies of various organs in mice and humans, pyroptosis has been found to play a significant role in fibrosis. Pyroptosis is a form of programmed cell death mediated by the N-terminal fragment of cysteinyl aspartate-specific proteinase (caspase)-1-cleaved gasdermin D (GSDMD, producing GSDMD-N) that gives rise to inflammation via the release of some proinflammatory cytokines, including IL-1β, IL-18 and HMGB1. These cytokines can initiate the activation of fibroblasts. Inflammasomes, an important factor upstream of GSDMD, can activate caspase-1 to trigger the maturation of IL-1β and IL-18. Moreover, the inhibition of inflammasomes, proinflammatory cytokines and GSDMD can prevent the progression of fibrosis. This review summarizes the growing evidence indicating that pyroptosis triggers fibrosis, and highlights potential novel targets for antifibrotic therapies.

Zebrafish intestinal transcriptome highlights subdued inflammatory responses to dietary soya bean and efficacy of yeast β-glucan

Anti-nutritional factors in dietary components can have a negative impact on the intestinal barrier. Here, we present soya bean-induced changes in the intestine of juvenile zebrafish and the effect of yeast β-glucan through a transcriptomic approach. The inclusion of soya bean meal affected the expression of several intestinal barrier function-related genes like arl4ca, rab25b, rhoub, muc5ac, muc5d, clcn2c and cltb in zebrafish. Several metabolic genes like cyp2x10.2, cyp2aa2, aldh3a2b, crata, elovl4, elovl6, slc51a, gpat2 and ATP-dependent peptidase activity (lonrf, clpxb) were altered in the intestinal tissue. The expression of immune-related genes like nlrc3, nlrp12, gimap8, prdm1 and tph1a, and genes related to cell cycle, DNA damage and DNA repair (e.g. spo11, rad21l1, nabp1b, spata22, tdrd9) were also affected in the soya bean fed group. Furthermore, our study suggests the plausible effect of yeast β-glucan through the modulation of several genes that regulate immune responses and barrier integrity. Our findings indicate a subdued inflammation in juvenile zebrafish fed soya bean meal and the efficacy of β-glucan to counter these subtle inflammatory responses.

Hepatic protective effects of Shenling Baizhu powder, a herbal compound, against inflammatory damage via TLR4/NLRP3 signalling pathway in rats with nonalcoholic fatty liver disease

OBJECTIVE

High-fat diet (HFD) and inflammation are two key contributors to nonalcoholic fatty liver disease (NAFLD). Shenling Baizhu powder (SLBZP), a classical herbal compound, has been successfully used to alleviate NAFLD. However, its specific mechanisms are not fully understood. In this study, we assessed the anti-NAFLD effect of SLBZP in vivo.

METHODS

Rats were fed an HFD with or without SLBZP or with probiotics. At the end of week 16, an echo magnetic resonance imaging (EchoMRI) body composition analyser was used to quantitatively analyse body composition; a micro-computed tomography (micro-CT) imaging system was used to evaluate whole body and liver fat; and the Moor full-field laser perfusion imager 2 was used to assess liver microcirculation, after which, all rats were sacrificed. Then, biochemical indicators in the blood and the ultrastructure of rat livers were evaluated. Protein expression related to the liver Toll-like receptor 4 (TLR4)/Nod-like receptor family pyrin domain-containing 3 (NLRP3) signalling pathway was assessed using Western blot analysis. Further, high-throughput screening of 29 related inflammatory factors in liver tissue was performed using a cytokine array.

RESULTS

SLBZP supplementation reduced body weight, serum free fatty acid, and insulin resistance index (P < 0.05). It also ameliorated liver microcirculation and ultrastructural abnormalities. EchoMRI and micro-CT quantitative analyses showed that treatment with SLBZP reduced fat mass and visceral fat (P < 0.05 and P < 0.01, respectively). In addition, SLBZP decreased the expression of lipopolysaccharide (LPS)-activated TLR4/NLRP3 signalling pathway-related proteins and altered the expression levels of some inflammatory cytokines in liver tissues.

CONCLUSION

SLBZP can inhibit NLRP3 inflammasome activation and interleukin-1β release by suppressing LPS-induced TLR4 expression in rats with HFD-induced NAFLD. Thus, SLBZP may be beneficial for the prevention and treatment of inflammatory damage and associated diseases.

Multifaceted regulation of hepatic lipid metabolism by YY1

This study shows that YY1 regulates hepatic lipid metabolism by directly or indirectly regulating the expression of several key upstream transcription factors and their coactivators.

Recent studies suggested that dysregulated YY1 plays a pivotal role in many liver diseases. To obtain a detailed view of genes and pathways regulated by YY1 in the liver, we carried out RNA sequencing in HepG2 cells after YY1 knockdown. A rigid set of 2,081 differentially expressed genes was identified by comparing the YY1-knockdown samples (n = 8) with the control samples (n = 14). YY1 knockdown significantly decreased the expression of several key transcription factors and their coactivators in lipid metabolism. This is illustrated by YY1 regulating PPARA expression through binding to its promoter and enhancer regions. Our study further suggest that down-regulation of the key transcription factors together with YY1 knockdown significantly decreased the cooperation between YY1 and these transcription factors at various regulatory regions, which are important in regulating the expression of genes in hepatic lipid metabolism. This was supported by the finding that the expression of SCD and ELOVL6, encoding key enzymes in lipogenesis, were regulated by the cooperation between YY1 and PPARA/RXRA complex over their promoters.

Dietary supplementation with myo-inositol reduces high-fructose diet-induced hepatic ChREBP binding and acetylation of histones H3 and H4 on the Elovl6 gene in rats

ELOVL fatty acid elongase 6 (ELOVL6) is a long-chain fatty acid elongase, and the hepatic expression of the Elovl6 gene and accumulation of triglycerides (TG) are enhanced by long-term high-fructose intake. Fatty acid synthesis genes, including Elovl6, are regulated by lipogenic transcription factors, sterol regulatory element-binding protein 1c (SREBP-1c) and carbohydrate-responsive element-binding protein (ChREBP). In addition, carbohydrate signals induce the expression of fatty acid synthase not only via these transcription factors but also via histone acetylation. Since a major lipotrope, myo-inositol (MI), can repress short-term high-fructose-induced fatty liver and the expression of fatty acid synthesis genes, we hypothesized that MI might influence SREBP-1c, ChREBP, and histone acetylation of Elovl6 in fatty liver induced by even short-term high-fructose intake. This study aimed to investigate whether dietary supplementation with MI affects Elovl6 expression, SREBP-1 and ChREBP binding, and acetylation of histones H3 and H4 at the Elovl6 promoter in short-term high-fructose diet-induced fatty liver in rats. Rats were fed a control diet, high-fructose diet, or high-fructose diet supplemented with 0.5% MI for 10 days. This study showed that MI supplementation reduced short-term high-fructose diet-induced hepatic expression of the Elovl6 gene, ChREBP binding, but not SREBP-1 binding, and acetylation of histones H3 and H4 at the Elovl6 promoter.

Omega-3FAs Can Inhibit the Inflammation and Insulin Resistance of Adipose Tissue Caused by HHcy Induced Lipids Profile Changing in Mice

The adipose Nod-like receptor protein 3 (NLRP3) inflammasome initiates insulin resistance; however, the mechanism of inflammasome activation in adipose tissue remains elusive. In this study, homocysteine (Hcy) was found to participate in insulin resistance via a NLRP3 inflammasome-related process. Hcy-induced activation of NLRP3 inflammasomes were observed in adipose tissue during the generation of insulin resistance in vivo. This animal model suggests that diets high in omega-3 fatty acids alter serum and adipose lipid profiles, and in this way, omega-3 fatty acids may reduce adipose tissue inflammation and attenuate insulin resistance.

Neutral Ceramidase Mediates Nonalcoholic Steatohepatitis by Regulating Monounsaturated Fatty Acids and Gut IgA+ B Cells

BACKGROUND AND AIMS

Nonalcoholic steatohepatitis (NASH) is associated with obesity and an increased risk for liver cirrhosis and cancer. Neutral ceramidase (NcDase), which is highly expressed in the intestinal brush border of the small intestine, plays a critical role in digesting dietary sphingolipids (ceramide) to regulate the balance of sphingosine and free fatty acids. It remains unresolved whether obesity-associated alteration of NcDase contributes to the manifestation of NASH. Here, we revealed that NcDase deficiency in murine models of NASH prevents hepatic inflammation and fibrosis but not steatosis.

APPROACH AND RESULTS

NcDase^-/- mice display reduced stearoyl-CoA desaturase (SCD) 1 expression with a compositional decrease of monounsaturated fatty acids (MUFAs) under the different dietary conditions. We further found that NcDase is a functional regulator of intestinal B cells and influences the abundance and quality of the secretory IgA response toward commensal bacteria. Analysis of composition of the gut microbiota found that Clostridiales colonization was increased in NcDase^-/- mice. The colonization of germ-free mice with gut microbiota from NcDase^-/- mice resulted in a greater decrease in the expression of SCD1 and the level of MUFAs in the liver relative to gut microbiota from wild-type littermates, which are associated with the alternation of IgA-bound bacteria, including increase of Ruminococcaceae and reduction of Desulfovibrio. Mechanistically, NcDase is a crucial link that controls the expression of SCD1 and MUFA-mediated activation of the Wnt/β-catenin. Very importantly, our experiments further demonstrated that Wnt3a stimulation can enhance the activity of NcDase in hepatocytes.

CONCLUSIONS

Thus, the NcDase-SCD1-Wnt feedback loop promotes the diet-induced steatohepatitis and fibrosis through the regulation of intestinal IgA⁺ immune cells.

ELOVL5 Is a Critical and Targetable Fatty Acid Elongase in Prostate Cancer

The androgen receptor (AR) is the key oncogenic driver of prostate cancer, and despite implementation of novel AR targeting therapies, outcomes for metastatic disease remain dismal. There is an urgent need to better understand androgen-regulated cellular processes to more effectively target the AR dependence of prostate cancer cells through new therapeutic vulnerabilities. Transcriptomic studies have consistently identified lipid metabolism as a hallmark of enhanced AR signaling in prostate cancer, yet the relationship between AR and the lipidome remains undefined. Using mass spectrometry-based lipidomics, this study reveals increased fatty acyl chain length in phospholipids from prostate cancer cells and patient-derived explants as one of the most striking androgen-regulated changes to lipid metabolism. Potent and direct AR-mediated induction of ELOVL fatty acid elongase 5 (ELOVL5), an enzyme that catalyzes fatty acid elongation, was demonstrated in prostate cancer cells, xenografts, and clinical tumors. Assessment of mRNA and protein in large-scale data sets revealed ELOVL5 as the predominant ELOVL expressed and upregulated in prostate cancer compared with nonmalignant prostate. ELOVL5 depletion markedly altered mitochondrial morphology and function, leading to excess generation of reactive oxygen species and resulting in suppression of prostate cancer cell proliferation, 3D growth, and in vivo tumor growth and metastasis. Supplementation with the monounsaturated fatty acid cis-vaccenic acid, a direct product of ELOVL5 elongation, reversed the oxidative stress and associated cell proliferation and migration effects of ELOVL5 knockdown. Collectively, these results identify lipid elongation as a protumorigenic metabolic pathway in prostate cancer that is androgen-regulated, critical for metastasis, and targetable via ELOVL5. SIGNIFICANCE: This study identifies phospholipid elongation as a new metabolic target of androgen action that is critical for prostate tumor metastasis.

A trans fatty acid substitute enhanced development of liver proliferative lesions induced in mice by feeding a choline-deficient, methionine-lowered, L-amino acid-defined, high-fat diet

Background

Nonalcoholic steatohepatitis (NASH) is a form of liver disease characterized by steatosis, necroinflammation, and fibrosis, resulting in cirrhosis and cancer. Efforts have focused on reducing the intake of trans fatty acids (TFAs) because of potential hazards to human health and the increased risk for NASH. However, the health benefits of reducing dietary TFAs have not been fully elucidated. Here, the effects of TFAs vs. a substitute on NASH induced in mice by feeding a choline-deficient, methionine-lowered, L-amino acid-defined, high-fat diet (CDAA-HF) were investigated.

Methods

Mice were fed CDAA-HF containing shortening with TFAs (CDAA-HF-T(+)), CDAA-HF containing shortening without TFAs (CDAA-HF-T(−)), or a control chow for 13 or 26 weeks.

Results

At week 13, NASH was induced in mice by feeding CDAA-HF-T(+) containing TFAs or CDAA-HF-T(−) containing no TFAs, but rather mostly saturated fatty acids (FAs), as evidenced by elevated serum transaminase activity and liver changes, including steatosis, inflammation, and fibrosis. CDAA-HF-T(−) induced a greater extent of hepatocellular apoptosis at week 13. At week 26, proliferative (preneoplastic and non-neoplastic) nodular lesions were more pronounced in mice fed CDAA-HF-T(−) than CDAA-HF-T(+).

Conclusions

Replacement of dietary TFAs with a substitute promoted the development of proliferation lesions in the liver of a mouse NASH model, at least under the present conditions. Attention should be paid regarding use of TFA substitutes in foods for human consumption, and a balance of FAs is likely more important than the particular types of FAs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-020-01423-3.

Establishing and validating a pathway prognostic signature in pancreatic cancer based on miRNA and mRNA sets using GSVA

Pancreatic cancer (PC) is a severe disease with the highest mortality rate among various cancers. It is urgent to find an effective and accurate way to predict the survival of PC patients. Gene set variation analysis (GSVA) was used to establish and validate a miRNA set-based pathway prognostic signature for PC (miPPSPC) and a mRNA set-based pathway prognostic signature for PC (mPPSPC) in independent datasets. An optimized miPPSPC was constructed by combining clinical parameters. The miPPSPC, optimized miPPSPC and mPPSPC were established and validated to predict the survival of PC patients and showed excellent predictive ability. Four metabolic pathways and one oxidative stress pathway were identified in the miPPSPC, whereas linoleic acid metabolism and the pentose phosphate pathway were identified in the mPPSPC. Key factors of the pentose phosphate pathway and linoleic acid metabolism, G6PD and CYP2C8/9/18/19, respectively, are related to the survival of PC patients according to our tissue microarray. Thus, the miPPSPC, optimized miPPSPC and mPPSPC can predict the survival of PC patients efficiently and precisely. The metabolic and oxidative stress pathways may participate in PC progression.

Fibrinogen-like protein 2 aggravates nonalcoholic steatohepatitis via interaction with TLR4, eliciting inflammation in macrophages and inducing hepatic lipid metabolism disorder

Rationale: The functions of fibrinogen-like protein 2 (fgl2) have been studied in many inflammatory and neoplastic diseases, but the role of fgl2 in nonalcoholic fatty liver disease has not yet been elucidated. In this study, we sought to investigate the role of fgl2 in the pathogenesis of nonalcoholic steatohepatitis (NASH). Methods: Hepatic fgl2 expression was tested in patients with nonalcoholic fatty liver (NAFL) or NASH and controls. Wild-type and fgl2-/- C57BL/6 mice were subjected to a methionine/choline-deficient (MCD) diet or a high-fat diet (HFD) to establish NASH models. Bone marrow-derived macrophages (BMDMs) stimulated with LPS or free fatty acids were used for the in vitro study. Results: In both humans and mice with NASH, macrophage accumulation was concomitant with significantly increased fgl2 expression in the liver. Fgl2 deficiency attenuated liver steatosis and inflammation in diet-induced murine models of NASH. In both liver tissues and BMDMs from NASH mice, fgl2 deficiency resulted in reduced levels of proinflammatory cytokines and reactive oxygen species (ROS) compared with levels in wild-type controls. Activation of NF-κB, p38-MAPK and NLRP3 inflammasomes was also suppressed upon fgl2 disruption. Moreover, lipogenic genes (Fasn and SREBP-2) were downregulated while lipolytic genes (PPAR and CPT1A) were upregulated in the livers of fgl2-/- NASH mice. Primary hepatocytes incubated with the medium collected from fgl2-/- BMDMs showed less fat deposition than those incubated with WT BMDMs. Furthermore, we discovered that fgl2 combined with TLR4 mediates the activation of the Myd88-dependent signaling pathway, which may contribute to inflammation and lipid metabolism disorders. Conclusions: These data suggest that fgl2 aggravates the progression of NASH through activation of NF-κB, p38-MAPK and NLRP3 inflammasomes in macrophages, which consequently induces overproduction of proinflammatory cytokines and lipid metabolism disorders. An interaction of fgl2 and TLR4 may in part contribute to the activation of inflammatory signaling pathways in macrophages.