Gene Expression Patterns in Hepatic Tissue and Visceral Adipose Tissue of Patients with Non-Alcoholic Fatty Liver Disease

Evaluation of the Diagnostic Utility of Selected Serum Adipokines and Cytokines in Subjects with MASLD-A Pilot Study

Excess adipose tissue, particularly of the visceral type, triggering chronic low-grade inflammation and altering its secretory profile, is a contributing factor to the initiation and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). This study aimed to compare the levels of selected adipokines and cytokines in individuals with normal weight and obesity, assessing their potential for diagnosing MASLD and establishing a cutoff point for body fat content associated with hepatic steatosis development. The research involved 99 participants categorized by body mass index and MASLD presence, undergoing body composition analysis, liver elastography, biochemical tests, and evaluation of adipokines and cytokines in serum. The results indicated elevated IL-6 (interleukin 6) serum levels in individuals with obesity with MASLD compared to the normal-weight group without MASLD. The multivariate regression analysis demonstrated a connection between hepatic steatosis and total adipose tissue content, VAT (visceral adipose tissue), VAT/SAT (subcutaneous adipose tissue) ratio, HOMA-IR (homeostasis model assessment of insulin resistance), IL-6, Il-1β (interleukin 1β), and MMP-2 (matrix metalloproteinase 2). Among the adipokines and cytokines examined in this study, interleukin 6 was the strongest predictor of MASLD regardless of gender. In addition, an association between the development of hepatic steatosis and higher serum IL-1β levels and higher adipose tissue was observed in women. However, further studies on a larger group of patients are needed to consider the use of these cytokines as markers of MASLD. The HOMA-IR index demonstrated potential diagnostic utility in identifying hepatic steatosis.

Inflammatory Protein Signatures as Predictive Disease-Specific Markers for Non-Alcoholic Steatohepatitis (NASH)

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic disease worldwide, consisting of a broad spectrum of diseases such as simple steatosis (NAFL), non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. Hepatic inflammation plays a key role in the pathophysiology of NAFLD. Inflammatory mediators such as cytokines and chemokines are considered as contributing factors to NAFLD development and progression. In the present study, we aimed to investigate the inflammatory protein signatures as predictive disease-specific markers for non-alcoholic fatty liver disease (NAFLD). This cross-sectional study included healthy control (n = 64), NAFL (n = 109), and NASH (n = 60) human subjects. Serum concentrations of various cytokines and chemokines were evaluated using sensitive multiplex assays. We used principal component analysis (PCoA) to reveal distinct differences in the levels of cytokines and chemokines between each of the study groups. Further, a random forest classification model was developed to identify the panel of markers that could predict diseases. The protein-protein network analysis was performed to determine the various signaling pathways associated with the disease-specific panel of markers. Serum concentrations of TNF-α, IL-1β, IL-1ra, G-CSF, PDGF-BB, MCP-1, MIP-1a, MIP-1b, RANTES, eotaxin, IL-8 and IP-10 were significantly increased in NASH group as compared to control group. Furthermore, serum concentrations of IL-9 and IL-13 were significantly lower in the NASH group, whereas IL-2 levels were significantly decreased in the NAFL group when compared to the control group. PCoA results demonstrated statistically significant differences in cytokines and chemokines between each of the study groups (PERMANOVA p = 0.001; R2 = 0.102). RANTES, IL-1ra, MIP-1b, IL-2, and G-CSF could differentiate the NAFL group from the controls; G-CSF, IL-1ra, TNF-α, RANTES, and IL-9 could differentiate the NASH group from the controls; and G-CSF, IL-9, IL-13, eotaxin, and TNF- α could differentiate the NASH group from the NAFL group. Our protein-protein network revealed that these markers are involved in cytokine-cytokine receptor interaction, Th1 and Th2 cell differentiation, TNF, chemokine, JAK/STAT, P13K/Akt, TLR, NOD-like receptor, NF-kB, and adipocytokine signaling pathways which might be responsible for disease pathogenesis. Our study findings revealed a set of distinct cytokine and chemokine markers and they might be considered as biomarkers in distinguishing NASH from NAFL. Future multicentre studies with larger sample size are recommended to determine the potential utility of these panels of markers.

Markers of adipose tissue fibrogenesis associate with clinically significant liver fibrosis and are unchanged by synbiotic treatment in patients with NAFLD

BACKGROUND AND AIMS

Subcutaneous adipose tissue (SAT) dysfunction contributes to NAFLD pathogenesis and may be influenced by the gut microbiota. Whether transcript profiles of SAT are associated with liver fibrosis and are influenced by synbiotic treatment (that changes the gut microbiome) is unknown. We investigated: (a) whether the presence of clinically significant, ≥F2 liver fibrosis associated with adipose tissue (AT) dysfunction, differential gene expression in SAT, and/or a marker of tissue fibrosis (Composite collagen gene expression (CCGE)); and (b) whether synbiotic treatment modified markers of AT dysfunction and the SAT transcriptome.

METHODS

Sixty-two patients with NAFLD (60 % men) were studied before and after 12 months of treatment with synbiotic or placebo and provided SAT samples. Vibration-controlled transient elastography (VCTE)-validated thresholds were used to assess liver fibrosis. RNA-sequencing and histological analysis of SAT were performed to determine differential gene expression, CCGE and the presence of collagen fibres. Regression modelling and receiver operator characteristic curve analysis were used to test associations with, and risk prediction for, ≥F2 liver fibrosis.

RESULTS

Patients with ≥F2 liver fibrosis (n = 24) had altered markers of AT dysfunction and a SAT gene expression signature characterised by enrichment of inflammatory and extracellular matrix-associated genes, compared to those with

CONCLUSION

A differential gene expression signature in SAT associates with ≥F2 liver fibrosis is explained by a measure of systemic insulin resistance and is not changed by synbiotic treatment. SAT CCGE values are a good predictor of ≥F2 liver fibrosis in NAFLD.

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Key Words

• Adipose tissue
• Gut microbiome
• Liver fibrosis
• NAFLD
• Synbiotic
• Transcriptome

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MESH Headings

• Male
• Humans
• Female
• Non-alcoholic Fatty Liver Disease/genetics
• Non-alcoholic Fatty Liver Disease/therapy
• Non-alcoholic Fatty Liver Disease/complications
• Synbiotics
• Biomarkers
• Liver Cirrhosis/genetics
• Liver Cirrhosis/therapy
• Liver Cirrhosis/complications
• Fibrosis
• Adipose Tissue/pathology
• Collagen/genetics
• Liver/pathology

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Affiliation(s)

Josh Bilson School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK
Carolina J Oquendo School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
James Read School of Chemistry, Faculty of Engineering and Physical sciences, University of Southampton, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK
Eleonora Scorletti School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK; Division of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
Paul R Afolabi School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK
Jenny Lord School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
Laure B Bindels Metabolism and Nutrition Research Group, Louvain Drug Research Institute, UC Louvain, Université Catholique de Louvain, Brussels, Belgium; Welbio department, WEL Research Institute, Wavre, Belgium
Giovanni Targher Department of Medicine, University of Verona, Italy; Metabolic Diseases Unit, IRCCS Sacro Cuore - Don Calabria Hospital, Negrar di Valpolicella, Italy
Sumeet Mahajan School of Chemistry, Faculty of Engineering and Physical sciences, University of Southampton, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK
Diana Baralle School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
Philip C Calder School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK
Christopher D Byrne School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK.
Jaswinder K Sethi School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK.

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Clinically important alterations in pharmacogene expression in histologically severe nonalcoholic fatty liver disease

Polypharmacy is common in patients with nonalcoholic fatty liver disease (NAFLD) and previous reports suggest that NAFLD is associated with altered drug disposition. This study aims to determine if patients with NAFLD are at risk for altered drug response by characterizing changes in hepatic mRNA expression of genes mediating drug disposition (pharmacogenes) across the histological NAFLD severity spectrum. We utilize RNA-seq for 93 liver biopsies with histologically staged NAFLD Activity Score (NAS), fibrosis stage, and steatohepatitis (NASH). We identify 37 significant pharmacogene-NAFLD severity associations including CYP2C19 downregulation. We chose to validate CYP2C19 due to its actionability in drug prescribing. Meta-analysis of 16 independent studies demonstrate that CYP2C19 is significantly downregulated to 46% in NASH, to 58% in high NAS, and to 43% in severe fibrosis. Our data demonstrate the downregulation of CYP2C19 in NAFLD which supports developing personalized medicine approaches for drugs sensitive to metabolism by the CYP2C19 enzyme.

Dietary EPA+DHA Mitigate Hepatic Toxicity and Modify the Oxylipin Profile in an Animal Model of Colorectal Cancer Treated with Chemotherapy

Irinotecan (CPT-11) and 5-fluorouracil (5-FU) are commonly used to treat metastatic colorectal cancer, but chemotherapy-associated steatosis/steatohepatitis (CASSH) frequently accompanies their use. The objective of this study was to determine effect of CPT-11+5-FU on liver toxicity, liver oxylipins, and cytokines, and to explore whether these alterations could be modified by dietary eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the form of fish oil (EPA+DHA). Tumor-bearing animals were administered CPT-11+5-FU and maintained on a control diet or a diet containing EPA+DHA (2.3 g/100 g). Livers were collected one week after chemotherapy for the analysis of oxylipins, cytokines, and markers of liver pathology (oxidized glutathione, GSSH; 4-hydroxynonenal, 4-HNE, and type-I collagen fiber). Dietary EPA+DHA prevented the chemotherapy-induced increases in liver GSSH (p < 0.011) and 4-HNE (p < 0.006). Compared with the tumor-bearing animals, ten oxylipins were altered (three/ten n-6 oxylipins were elevated while seven/ten n-3 oxylipins were reduced) following chemotherapy. Reductions in the n-3 fatty-acid-derived oxylipins that were evident following chemotherapy were restored by dietary EPA+DHA. Liver TNF-α, IL-6 and IL-10 were elevated (p < 0.05) following chemotherapy; dietary EPA+DHA reduced IL-6 (p = 0.09) and eotaxin (p = 0.007) levels. Chemotherapy-induced liver injury results in distinct alterations in oxylipins and cytokines, and dietary EPA+DHA attenuates these pathophysiological effects.

Gut microbiota–mitochondrial inter-talk in non-alcoholic fatty liver disease

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD), which is a progressive disease, has exerted huge a healthcare burden worldwide. New investigations have suggested that the gut microbiota closely participates in the progression of NAFLD through the gut–liver axis or gut–brain–liver axis. The composition of the microbiota can be altered by multiple factors, primarily dietary style, nutritional supplements, or exercise. Recent evidence has revealed that gut microbiota is involved in mitochondrial biogenesis and energy metabolism in the liver by regulating crucial transcription factors, enzymes, or genes. Moreover, microbiota metabolites can also affect mitochondrial oxidative stress function and swallow formation, subsequently controlling the inflammatory response and regulating the levels of inflammatory cytokines, which are the predominant regulators of NAFLD. This review focuses on the changes in the composition of the gut microbiota and metabolites as well as the cross-talk between gut microbiota and mitochondrial function. We thus aim to comprehensively explore the potential mechanisms of gut microbiota in NAFLD and potential therapeutic strategies targeting NAFLD management.

Relationship Between Hepatic Gene Expression, Intestinal Microbiota, and Inferred Functional Metagenomic Analysis in NAFLD

INTRODUCTION

We previously reported a lower fecal abundance of Ruminococcus spp., Faecalibacterium prausnitzii , and Coprococcus spp. in nonalcoholic fatty liver disease (NAFLD). In this article, we assess the associations between hepatic gene expression, the specific taxa, and bacterial pathways.

METHODS

The relationships between hepatic genes that were differentially expressed in patients with NAFLD vs healthy controls (HC) and the abundance of these specific taxa were studied. Inferred functional metagenomic analysis using Piphillin was also performed to investigate associations with bacterial pathways.

RESULTS

Fifteen patients with NAFLD and 6 HC participated. Of 728 hepatic genes examined, 176 correlated with the abundance of Ruminococcus spp., 138 with F. prausnitzii , and 92 with Coprococcus spp. For Ruminococcus spp., genes were enriched in gene ontology (GO) terms related to apoptotic process, response to external and cytokine stimuli, and regulation of signaling. Several genes related to the Kyoto Encyclopedia of Genes and Genomes pathway insulin resistance were correlated with F. prausnitzii . The hepatic genes associated with F. prausnitzii were enriched in GO terms related to cellular response to different stimuli, apoptotic process, and regulation of metabolic pathways. For Coprococcus spp., only the GO term response to external stimulus was enriched. There was a distinct pattern of associations between hepatic genes and bacterial taxa in NAFLD vs HC. For bacterial pathways, 65 and 18 hepatic genes correlated with bacterial metabolic functions in NAFLD and HC, respectively.

DISCUSSION

Hepatic gene expression related to insulin resistance, inflammation, external stimuli, and apoptosis correlated with bacterial taxa. Patients with NAFLD showed a higher presence of bacterial pathways associated with lipid metabolism.

MicroRNA-100 Reduced Fetal Bovine Muscle Satellite Cell Myogenesis and Augmented Intramuscular Lipid Deposition by Modulating IGF1R

Previously, microRNA-100 (miR-100) and its putative mRNA target, insulin-like growth factor receptor-1 (IGF1R) were identified as differentially and inversely expressed in bovine longissimus dorsi (LD) muscles with divergent intramuscular fat (IMF) content by our group. While IGF1R signaling is implicated in myogenesis and muscle lipid metabolism, the underlying regulatory mechanisms are poorly understood. In the present study, we aimed to investigate the regulation of IGF1R by miR-100 during bovine muscle satellite cell (BMSC) myogenesis and lipid deposition. MiR-100 was confirmed to target the IGF1R 3′-untranslated region (3′-UTR) by luciferase reporter assay. Furthermore, expression of miR-100 and IGF1R was reciprocal during BMSC differentiation, suggesting a crosstalk between the two. Correspondingly, miR-100 mimic (agomiR) suppressed the levels of IGF1R, PI3K/AKT pathway signaling, myogenic gene MYOG, muscle structural components MYH7 and MYH8, whereas the inhibitor (antagomiR) had no clear stimulating effects. The IGF1R inhibitor (BMS-754807) curtailed receptor levels and triggered atrophy in muscle myotubes but did not influence miR-100 expression. AgomiR increased oleic acid-induced lipid deposition in BMSC myotubes supporting its involvement in intramuscular fat deposition, while antagomiR had no effect. Moreover, mitochondrial beta-oxidation and long-chain fatty acid synthesis-related genes were modulated by agomiR addition. Our results demonstrate modulatory roles of miR-100 in BMSC development, lipid deposition, and metabolism and suggest a role of miR-100 in marbling characteristics of meat animals and fat oxidation in muscle.

Periodontal disease-related nonalcoholic fatty liver disease and nonalcoholic steatohepatitis: An emerging concept of oral-liver axis

Periodontal disease, a chronic inflammatory disease of the periodontal tissues, is not only a major cause of tooth loss, but it is also known to exacerbate/be associated with various metabolic disorders, such as obesity, diabetes, dyslipidemia, and cardiovascular disease. Recently, growing evidence has suggested that periodontal disease has adverse effects on the pathophysiology of liver disease. In particular, nonalcoholic fatty liver disease, a hepatic manifestation of metabolic syndrome, has been associated with periodontal disease. Nonalcoholic fatty liver disease is characterized by hepatic fat deposition in the absence of a habitual drinking history, viral infections, or autoimmune diseases. A subset of nonalcoholic fatty liver diseases can develop into more severe and progressive forms, namely nonalcoholic steatohepatitis. The latter can lead to cirrhosis and hepatocellular carcinoma, which are end‐stage liver diseases. Extensive research has provided plausible mechanisms to explain how periodontal disease can negatively affect nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, namely via hematogenous or enteral routes. During periodontitis, the liver is under constant exposure to various pathogenic factors that diffuse systemically from the oral cavity, such as bacteria and their by‐products, inflammatory cytokines, and reactive oxygen species, and these can be involved in disease promotion of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Also, gut microbiome dysbiosis induced by enteral translocation of periodontopathic bacteria may impair gut wall barrier function and promote the transfer of hepatotoxins and enterobacteria to the liver through the enterohepatic circulation. Moreover, in a population with metabolic syndrome, the interaction between periodontitis and systemic conditions related to insulin resistance further strengthens the association with nonalcoholic fatty liver disease. However, most of the pathologic links between periodontitis and nonalcoholic fatty liver disease in humans are provided by epidemiologic observational studies, with the causal relationship not yet being established. Several systematic and meta‐analysis studies also show conflicting results. In addition, the effect of periodontal treatment on nonalcoholic fatty liver disease has hardly been studied. Despite these limitations, the global burden of periodontal disease combined with the recent nonalcoholic fatty liver disease epidemic has important clinical and public health implications. Emerging evidence suggests an association between periodontal disease and liver diseases, and thus we propose the term periodontal disease–related nonalcoholic fatty liver disease or periodontal disease–related nonalcoholic steatohepatitis. Continued efforts in this area will pave the way for new diagnostic and therapeutic approaches based on a periodontologic viewpoint to address this life‐threatening liver disease.

Crosstalk Between Plasma Cytokines, Inflammation, and Liver Damage as a New Strategy to Monitoring NAFLD Progression

Cytokines are involved in the immunopathogenesis of nonalcoholic fatty liver disease (NAFLD), but the relationship between them and clinical parameters of NAFLD progression is still unknown. Using flow cytometry, we evaluated the plasma levels of IL-1β, IL-6, IL-12, TNF and IL-10 and their association with clinical and biochemical parameters of liver function during simple steatosis (NAFL) and nonalcoholic steatohepatitis (NASH) in biopsy-proven patients. The NASH patients showed higher levels of IL-6 associated with a lower IL-10/IL-6 ratio. Besides heatmaps were similar in the NAFL and NASH groups, the same did not occur in signature curves, the NASH patients were high producers to IL-12 and IL-6 while the NAFL patients were not high producers of any cytokines evaluated. Integrative biomarker network analysis revealed that cytokines are differently correlated with clinical parameters, while IL-12, IL-10 presented moderate and negative correlations with glycemic and lipid profile in the NAFL group. The NASH group IL-12 and TNF revealed stronger and positive correlations with transient elastography parameters and NAFLD liver fibrosis score. These data suggest that IL-6 and IL-10 might act in chronic inflammation and insulin resistance whereas IL-12 and TNF may be involved in promoting liver damage and NAFLD progression. Plasma concentration analysis of these molecules and their association with clinical parameters can be used as new biomarkers to monitoring NAFLD progression and to reflect NASH development.

Adipose tissue browning in mice and humans

In the midst of an obesity epidemic, the promotion of brown adipose tissue (BAT) function and the browning of white adipose tissue (WAT) have emerged as promising therapeutic targets to increase energy expenditure and counteract weight gain. Despite the fact that the thermogenic potential of bone fide BAT in rodents is several orders of magnitudes higher than white fat containing brite/beige adipocytes, WAT browning represents a particularly intriguing concept in humans given the extreme amount of excess WAT in obese individuals. In addition, the clear distinction between classic brown and beige fat that has been proposed in mice does not exist in humans. In fact, studies of human BAT biopsies found controversial results suggesting both classic brown and beige characteristics. Irrespective of the true ‘color’, accumulating evidence suggests the induction of thermogenic adipocytes in human WAT depots in response to specific stimuli, highlighting that WAT browning may occur in both, mice and humans. These observations also emphasize the great plasticity of human fat depots and raise important questions about the metabolic properties of thermogenically active adipose tissue in humans and the potential therapeutic implications. We will first review the cellular and molecular aspects of selected adipose tissue browning concepts that have been identified in mouse models with emphasis on neuronal factors, the microbiome, immune cells and several hormones. We will also summarize the evidence for adipose tissue browning in humans including some experimental pharmacologic approaches.

Adipose may actively delay progression of NAFLD by releasing tumor-suppressing, anti-fibrotic miR-122 into circulation

Nonalcoholic fatty liver disease (NAFLD) is the most common liver pathology. Here we propose tissue-cooperative, homeostatic model of NAFLD. During early stages of NAFLD the intrahepatic production of miR-122 falls, while the secretion of miRNA-containing exosomes by adipose increases. Bloodstream carries exosome to the liver, where their miRNA cargo is released to regulate their intrahepatic targets. When the deterioration of adipose catches up with the failing hepatic parenchyma, the external supply of liver-supporting miRNAs gradually tapers off, leading to the fibrotic decompensation of the liver and an increase in hepatic carcinogenesis. This model may explain paradoxical observations of the disease-associated decrease in intrahepatic production of certain miRNAs with an increase in their levels in serum. Infusions of miR-122 and, possibly, some other miRNAs may be efficient for preventing NAFLD-associated hepatocellular carcinoma. The best candidates for exosome-wrapped miRNA producer are adipose tissue-derived mesenchymal stem cells (MSCs), known for their capacity to shed large amounts of exosomes into the media. Notably, MSC-derived exosomes with no specific loading are already tested in patients with liver fibrosis. Carrier exosomes may be co-manufactured along with their cargo. Exosome-delivered miRNA cocktails may augment functioning of human organs suffering from a variety of chronic diseases.

Systems-level organization of non-alcoholic fatty liver disease progression network

Non-Alcoholic Fatty Liver Disease (NAFLD) is a complex spectrum of diseases ranging from simple steatosis to Non-Alcoholic Steatohepatitis (NASH) with fibrosis, which can progress to cirrhosis and hepatocellular carcinoma. The pathogenesis of NAFLD is complex, involving crosstalk between multiple organs, cell-types, and environmental and genetic factors. Dysfunction of the adipose tissue plays a central role in NAFLD progression. Here, we analysed transcriptomics data obtained from the Visceral Adipose Tissue (VAT) of NAFLD patients to understand how the VAT metabolism is altered at the genome scale and co-regulated with other cellular processes during the progression from obesity to NASH with fibrosis. For this purpose, we performed Weighted Gene Co-expression Network Analysis (WGCNA), a method that organizes the disease transcriptome into functional modules of cellular processes and pathways. Our analysis revealed the coordination of metabolic and inflammatory modules (termed "immunometabolism") in the VAT of NAFLD patients. We found that genes of arachidonic acid, sphingolipid and glycosphingolipid metabolism were upregulated and co-expressed with genes of proinflammatory signalling pathways and hypoxia in NASH/NASH with fibrosis. We hypothesize that these metabolic alterations might play a role in sustaining VAT inflammation. Furthermore, immunometabolism related genes were also co-expressed with genes involved in Extracellular Matrix (ECM) degradation. Our analysis indicates that upregulation of both ECM degrading enzymes and their inhibitors (incoherent feedforward loop) potentially leads to the ECM deposition in the VAT of NASH with fibrosis patients.

CD98 siRNA-loaded nanoparticles decrease hepatic steatosis in mice

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid hepatic accumulation. Here, we investigated whether a reduction of CD98 expression mediated by CD98 siRNA-loaded nanoparticles (NPs) could attenuate liver disease markers in a mouse model of NAFLD. NPs were generated using a double emulsion/solvent evaporation technique. Mice fed a high fat diet for 8 weeks to induce fatty liver were treated with vein tail injections of CD98 siRNA-loaded NPs. In vitro, HepG2 treated with CD98 siRNA-loaded NPs showed significant downregulation of CD98 leading to a significant decrease of major pro-inflammatory cytokines and markers. In vivo, CD98 siRNA-loaded NPs strongly decreased all markers of NAFLD, including the blood levels of ALT and lipids accumulation, fibrosis evidence and pro-inflammatory cytokines. In conclusion, our results indicate that CD98 appears to function as a key actor/inducer in NAFLD, and that our NPs approach may offer a new targeted therapeutic for this disease.

Decreased lipid metabolism but increased FA biosynthesis are coupled with changes in liver microRNAs in obese subjects with NAFLD

BACKGROUND/OBJECTIVE

Many controversies regarding the association of liver miRNAs with obesity and nonalcoholic fatty liver diseases (NAFLD) call for additional validations. This study sought to investigate variations in genes and hepatic miRNAs in a sample of obese patients with or without NAFLD and human hepatocytes (HH).

SUBJECTS/METHODS

A total of 60 non-consecutive obese women following bariatric surgery were recruited. Subjects were classified as NAFLD (n=17), borderline (n=24) and controls (n=19) with normal enzymatic profile, liver histology and ultrasound assessments. Profiling of 744 miRNAs was performed in 8 obese women with no sign of hepatic disease and 11 NAFLD patients. Additional validation and expression of genes related to de novo fatty acid (FA) biosynthesis, uptake, transport and β-oxidation; glucose metabolism, and inflammation was tested in the extended sample. Induction of NAFLD-related genes and miRNAs was examined in HepG2 cells and primary HH treated with palmitic acid (PA), a combination of palmitate and oleic acid, or high glucose, and insulin (HG) mimicking insulin resistance in NAFLD.

RESULTS

In the discovery sample, 14 miRNAs were associated with NAFLD. Analyses in the extended sample confirmed decreased miR-139-5p, miR-30b-5p, miR-122-5p and miR-422a, and increased miR-146b-5p in obese subjects with NAFLD. Multiple linear regression analyses disclosed that NAFLD contributed independently to explain miR-139-5p (P=0.005), miR-30b-5p (P=0.005), miR-122-5p (P=0.021), miR-422a (P=0.007) and miR-146a (P=0.033) expression variance after controlling for confounders. Decreased miR-122-5p in liver was associated with impaired FA usage. Expression of inflammatory and macrophage-related genes was opposite to decreased miR-30b-5p, miR-139-5p and miR-422a, whereas increased miR-146b-5p was associated with FABP4 and decreased glucose metabolism and FA mobilization. In partial agreement, PA (but not HG) led to decreased miR-139-5p, miR-30b-5p, miR-422a and miR-146a in vitro, in parallel with increased lipogenesis and FA transport, decreased glucose metabolism and diminished FA oxidation.

CONCLUSION

This study confirms decreased liver glucose and lipid metabolism but increased FA biosynthesis coupled with changes in five unique miRNAs in obese patients with NAFLD.

Circulating and visceral adipose miR-100 is down-regulated in patients with obesity and Type 2 diabetes

Obesity is a major public health problem conferring substantial excess risk for Type 2 diabetes (T2D). The role of microRNAs (miRNAs) in obesity and adipose tissue is not clearly defined. We hypothesize that circulating miRNA expression profiles vary according to differences in body mass index (BMI) and T2D and circulating miRNAs may reflect adipose tissue expression. Compared to healthy, lean individuals, circulating miR-100 was significantly lower in obese normoglycemic subjects and subjects with T2D. In visceral adipose tissue, expression of miR-100 was lower from obese subjects with T2D compared to obese subjects without T2D. miR-100 expression was significantly lower after adipogenic induction in human visceral, subcutaneous adipocytes and 3T3-L1 adipocytes. miR-100 reduced expression of mammalian target of rapamycin (mTOR) and Insulin Growth Factor Receptor (IGFR) directly. Differentiation of 3T3-L1 was accelerated by inhibition of miR-100 and reduced by miR-100 mimic transfection. Our data provide the first evidence of an association of circulating miR-100 with obesity and diabetes. Additionally, our in-vitro findings, and the miR-100 expression patterns in site-specific adipose tissue suggest miR-100 to modulate IGFR, mTOR and mediate adipogenesis.

Bidirectional Relationships and Disconnects between NAFLD and Features of the Metabolic Syndrome

Non-alcoholic fatty liver disease (NAFLD) represents a wide spectrum of liver disease from simple steatosis, to steatohepatitis, (both with and without liver fibrosis), cirrhosis and end-stage liver failure. NAFLD also increases the risk of hepatocellular carcinoma (HCC) and both HCC and end stage liver disease may markedly increase risk of liver-related mortality. NAFLD is increasing in prevalence and is presently the second most frequent indication for liver transplantation. As NAFLD is frequently associated with insulin resistance, central obesity, dyslipidaemia, hypertension and hyperglycaemia, NAFLD is often considered the hepatic manifestation of the metabolic syndrome. There is growing evidence that this relationship between NAFLD and metabolic syndrome is bidirectional, in that NAFLD can predispose to metabolic syndrome features, which can in turn exacerbate NAFLD or increase the risk of its development in those without a pre-existing diagnosis. Although the relationship between NAFLD and metabolic syndrome is frequently bidirectional, recently there has been much interest in genotype/phenotype relationships where there is a disconnect between the liver disease and metabolic syndrome features. Such potential examples of genotypes that are associated with a dissociation between liver disease and metabolic syndrome are patatin-like phospholipase domain-containing protein-3 (PNPLA3) (I148M) and transmembrane 6 superfamily member 2 protein (TM6SF2) (E167K) genotypes. This review will explore the bidirectional relationship between metabolic syndrome and NAFLD, and will also discuss recent insights from studies of PNPLA3 and TM6SF2 genotypes that may give insight into how and why metabolic syndrome features and liver disease are linked in NAFLD.

Leptin in nonalcoholic fatty liver disease: a narrative review

Leptin, the first described adipokine, interplays with hepatic metabolism. The aim of this review was to summarize available data on the association between leptin and nonalcoholic fatty liver disease (NAFLD). Leptin has a potential dual action on NAFLD experimental models, exerting a possible anti-steatotic, but also a proinflammatory and profibrogenic action. Observational clinical studies have shown higher or similar leptin levels between simple steatosis and nonalcoholic steatohepatitis (NASH) compared with controls. Interventional studies showed that circulating leptin diminishes together with body mass index after successful weight loss following lifestyle modifications or bariatric surgery. Studies providing evidence for the effect of other medications on leptin levels in NAFLD populations are limited and of low power. Data from small studies claim that recombinant leptin administration had a possibly beneficial effect on steatosis, but not fibrosis, in NAFLD patients with hypoleptinemia. Although the aforementioned dual leptin action has not yet been validated in humans, leptin administration in NAFLD patients with normoleptinemia or hyperleptinemia is discouraged. Further well-controlled studies in cautiously selected populations are needed to elucidate whether leptin has any prognostic and therapeutic role in NAFLD patients.

CXCL10 plays a key role as an inflammatory mediator and a non-invasive biomarker of non-alcoholic steatohepatitis

BACKGROUND & AIMS

Perpetuate liver inflammation is crucial in the pathogenesis of non-alcoholic steatohepatitis (NASH). Expression of CXCL10, a pro-inflammatory cytokine, correlates positively with obesity and type 2 diabetes. Whether CXCL10 plays a role in NASH was unknown. We aimed to investigate the functional and clinical impact of CXCL10 in NASH.

METHODS

Cxcl10 gene-deleted (Cxcl10(-/-)) and C57BL/6 wild type (WT) mice were fed a methionine- and choline-deficient (MCD) diet for 4 or 8 weeks. In other experiments, we injected neutralizing anti-CXCL10 mAb into MCD-fed WT mice. Human serum was obtained from 147 patients with biopsy-proven non-alcoholic fatty liver disease and 73 control subjects.

RESULTS

WT mice, fed the MCD diet, developed steatohepatitis with higher hepatic CXCL10 expression. Cxcl10(-/-) mice were refractory to MCD-induced steatohepatitis. We further revealed that CXCL10 was associated with the induction of important pro-inflammatory cytokines (TNF-α, IL-1β, and MCP-1) and activation of the NF-κB pathway. CXCL10 was linked to steatosis through upregulation of the lipogenic factors SREBP-1c and LXR, and also to oxidative stress (upregulation of CYP2E1 and C/EBPβ). Blockade of CXCL10 protected against hepatocyte injury in vitro and against steatohepatitis development in mice. We further investigated the clinical impact of CXCL10 and found circulating and hepatic CXCL10 levels were significantly higher in human NASH. Importantly, the circulating CXCL10 level was correlated with the degree of lobular inflammation and was an independent risk factor for NASH patients.

CONCLUSIONS

We demonstrate for the first time that CXCL10 plays a pivotal role in the pathogenesis of experimental steatohepatitis. CXCL10 maybe a potential non-invasive biomarker for NASH patients.

Expression of energy metabolism related genes in the gastric tissue of obese individuals with non-alcoholic fatty liver disease

Background

Stomach is an integral part of the energy balance regulating circuit. Studies exploring the effects of cross-system changes in the energy homeostasis in stomach tissue are scarce. The proximity of the stomach to liver - the most common secondary target affected by obesity – suggests that these two organs are exposed to each other’s local secretion. Therefore, we aimed at expression profiling of energy metabolism associated genes in the gastric tissue of obese non-alcoholic fatty liver disease (NAFLD) patients.

Methods

A total of 24 patients with histologically-proven NAFLD were included. In the gastric tissue, gene expression profiling of 84 energy metabolism associated genes was carried out.

Results

The accumulation of the fat in the liver parenchyma is accompanied by downregulation of genes encoding for carboxypeptidase E (CPE) and Interleukin 1B (IL1B) in the gastric mucosa of same patient. In patients with high grade hepatic steatosis, Interleukin 1 beta encoding gene with anorexigenic function, IL1B was downregulated. The levels expression of 21 genes, including ADRA2B, CNR1 and LEP were significantly altered in the gastric tissue of NAFLD patients with hepatic inflammation. There were also indications of an increase in the opioid signaling within gastric mucosa that may results in a shift to proinflammatory environment within this organ and contribute to systemic inflammation and the pathogenic processes in hepatic parenchyma.

Conclusions

We have shown differential expression of energy metabolism associated genes in the gastric tissue of obese NAFLD patients. Importantly, these gene expression profiles are associated with changes in the hepatic parenchyma as reflected in increased scores for hepatic steatosis, inflammation, fibrosis and NASH. This study suggests the complex interplay of multiple organs in the pathogenesis of obesity-related complications such as NAFLD and provides further evidence supporting an important role for gastric tissue in promoting obesity-related complications.

CEACAM1 loss links inflammation to insulin resistance in obesity and non-alcoholic steatohepatitis (NASH)

Mounting epidemiological evidence points to an association between metabolic syndrome and non-alcoholic steatohepatitis (NASH), an increasingly recognized new epidemic. NASH pathologies include hepatocellular ballooning, lobular inflammation, hepatocellular injury, apoptosis, and hepatic fibrosis. We will review the relationship between insulin resistance and inflammation in visceral obesity and NASH in an attempt to shed more light on the pathogenesis of these major metabolic diseases. Moreover, we will identify loss of the carcinoembryonic antigen-related cell adhesion molecule 1 as a unifying mechanism linking the immunological and metabolic abnormalities in NASH.

Irisin is inversely associated with intrahepatic triglyceride contents in obese adults

BACKGROUND & AIMS

Obesity is closely related to non-alcoholic fatty liver disease (NAFLD), which has become an important public health problem because of its high prevalence and association with metabolic syndromes. Irisin was recently identified as a novel peptide to improve obesity and glucose homeostasis, and considered to be therapeutic for human metabolic diseases. The aim of this study was to examine the association of serum irisin concentration and liver triglyceride contents in obese Chinese adults.

METHODS

Serum irisin levels were measured and liver fat contents determined by (1)H MRS in 296 obese adults. Anthropometric parameters and blood biochemical indexes including liver enzymes, glucose, and lipid profiles were detected. The liver triglyceride contents of subjects were measured by (1)H MRS. The protein levels of irisin were determined by quantitative ELISA.

RESULTS

We found that serum irisin levels were reduced in obese adults with NAFLD. By dividing the distribution of intrahepatic triglyceride (IHTG) contents into quartiles, serum irisin levels were reduced gradually with the increase of IHTG contents (p<0.01). Higher serum irisin levels were associated with preferable TG levels. Serum ALT and AST concentrations were inversely correlated with serum irisin levels. Multivariate linear regression analysis demonstrated that serum irisin levels were independently associated with liver fat (p<0.01). By logistic regression analysis, the odds ratio for higher IHTG contents was reduced by 12.4% per 1 SD increase in serum irisin concentrations after adjustment for multivariate metabolic factors [OR (95% CI); 0.876 (0.777-0.987)].

CONCLUSIONS

These results demonstrated that serum irisin concentrations were inversely associated with the triglyceride contents in the liver and liver enzymes in obese Chinese adults.

Expression of genes for microRNA-processing enzymes is altered in advanced non-alcoholic fatty liver disease

BACKGROUND AND AIM

Recently, microRNAs (miRNA) have been linked to the pathogenesis of non-alcoholic fatty liver disease (NAFLD) and its progression to non-alcoholic steatohepatitis (NASH). First transcribed as pri-miRNA, these molecules are further processed by a complex of endonuclear and cytosolic RNA binding molecules to form mature miRNAs. The aim of this study is to investigate mechanisms of miRNA regulation in the visceral adipose of obese NAFLD patients via measuring expression of miRNA processing enzymes and pri-miRNA.

METHODS

Total RNAs were extracted from visceral adipose tissue (VAT) samples collected from patients undergoing bariatric surgery. All patients had biopsy-proven NAFLD (NASH patients [n = 12] and non-NASH NAFLD [n = 12]). For each patient, we profiled mRNA levels for three miRNA processing elements (Drosha, DGCR8, and Dicer1) and seven pri-miRNAs (pri-miR-125b-2, pri-miR-16-2, pri-miR-26a-1, pri-miR-26a-2, pri-miR-7-1, pri-miR-7-2, and pri-miR-7-3).

RESULTS

Expression of Dicer1, Drosha and DGCR8 was significantly increased within the NASH cohort along with expression of pri-miR-7-1. The presence of focal necrosis on the liver biopsy correlated significantly with levels of Dicer1 and DGRC8. Both NASH and ballooning degeneration of hepatocytes correlated negatively with the expression levels of hsa-miR-125b. Histologic NASH correlated positively with the expression levels of pri-miR-16-2 and pri-miR-7-1. The presence of the hepatocyte's ballooning degeneration in the liver biopsy correlated positively with pri-miR-26a-1 and pri-miR-7-1. The expression profile of pri-miR-125b-2 also correlated positively with body mass index.

CONCLUSIONS

Our findings support the hypothesis that VAT-derived miRNA may contribute to the pathogenesis of NASH in obese patients.

Exploration of a symptoms experience in people with obesity-related nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent condition strongly associated with obesity that can result in premature death. Little is known about the symptoms experience in this progressive disease, preventing health care providers from intervening in the early stages.

PURPOSE

This study explicated symptoms in persons with NAFLD at higher risk of disease progression defined as the presence of one or two copies of the PNPLA3 (rs738409)-G allele.

METHOD

Guided by the Symptoms Experience Model, 42 persons older than 21 years of age with diagnosed NAFLD were recruited from Western Michigan specialty offices in this cross-sectional descriptive study design. The Memorial Symptom Assessment Scale was used to measure the symptoms experience.

DISCUSSION

Participants (97%) experienced 1 or more symptoms (average number of symptoms 12.02, standard deviation = 8.817). There was no statistically significant relationship between symptoms and the PNPLA3 (rs738409) variants. Significant predictors of mean frequency, severity, and distress of symptoms (the Total Memorial Symptom Scale) (F[15, 25] = 2.609, p = .016) were identified.

CONCLUSION

People with NAFLD experience an average of 12 symptoms.

Time-course microarrays reveal modulation of developmental, lipid metabolism and immune gene networks in intrascapular brown adipose tissue during the development of diet-induced obesity

OBJECTIVE

The aim of this study was to establish the time-course of molecular events in intrascapular brown adipose tissue (iBAT) during the development of diet-induced obesity using microarrays and molecular network analysis.

DESIGN

C57BL/6J male inbred mice were fed a high-fat diet (HFD) or normal diet (ND) and killed at multiple time-points over 24 weeks.

METHODS

Global transcriptional changes in iBAT were determined by time-course microarrays of pooled RNA (n=6, pools per time-point) at 2, 4, 8, 20 and 24 weeks using Illumina MouseWG-6 v2.0 Beadchips. Molecular networks were constructed using the Ingenuity knowledgebase based on differentially expressed genes at each time-point.

RESULTS

Body weight and subcutaneous adipose were progressively increased over 24 weeks, whereas iBAT was significantly increased between 6 and 12 weeks in HFD-fed C57BL/6J mice compared with controls. Blood glucose and insulin levels were increased between 16 and 24 weeks. Time-course microarrays, revealed 155 differentially expressed genes at one or more time-points over 24 weeks in the iBAT of HFD-fed mice compared with controls. Time-course network analysis revealed a network of skeletal muscle development genes that was activated between 2 and 4 weeks, subsequently a network of immune trafficking genes was activated at 8 weeks. After 20 and 24 weeks, multiple lipid metabolism and immune response networks were activated. Several target genes identified by time-course microarrays were independently validated using RT-qPCR. Tnnc1 was upregulated early between 2 and 4 weeks, later Cd68 and Col1a1 were upregulated between 20 and 24 weeks, whereas 11β-hydroxysteroid dehydrogenase (Hsd11b1) was consistently downregulated during the development of diet-induced obesity.

CONCLUSION

Molecular networks in iBAT are modulated in a time-dependent manner in response to a HFD. A broad range of gene targets exists to alter molecular changes within iBAT during the development of diet-induced obesity.

Genomic aspects of NAFLD pathogenesis

Non-alcoholic fatty liver disease (NAFLD) is the most predominant liver disease worldwide and hepatic manifestation of the metabolic syndrome. Its histology spectrum ranges from steatosis, to steatohepatitis (NASH) that can further progress to cirrhosis and hepatocellular carcinoma (HCC). The increasing incidence of NAFLD has contributed to rising numbers of HCC occurrences. NAFLD progression is governed by genetic susceptibility, environmental factors, lifestyle and features of the metabolic syndrome, many of which overlap with HCC. Gene expression profiling and genome wide association studies have identified novel disease pathways and polymorphisms in genes that may be potential biomarkers of NAFLD progression. However, the multifactorial nature of NAFLD and the limited number of sufficiently powered studies are among the current limitations for validated biomarkers of clinical utility. Further studies incorporating the links between circadian regulation and hepatic metabolism might represent an additional direction in the search for predictive biomarkers of liver disease progression and treatment outcomes.

Time-dependent network analysis reveals molecular targets underlying the development of diet-induced obesity and non-alcoholic steatohepatitis

Prolonged high-fat diet leads to the development of obesity and multiple comorbidities including non-alcoholic steatohepatitis (NASH), but the underlying molecular basis is not fully understood. We combine molecular networks and time course gene expression profiles to reveal the dynamic changes in molecular networks underlying diet-induced obesity and NASH. We also identify hub genes associated with the development of NASH. Core diet-induced obesity networks were constructed using Ingenuity pathway analysis (IPA) based on 332 high-fat diet responsive genes identified in liver by time course microarray analysis (8 time points over 24 weeks) of high-fat diet-fed mice compared to normal diet-fed mice. IPA identified five core diet-induced obesity networks with time-dependent gene expression changes in liver. These networks were associated with cell-to-cell signaling and interaction (Network 1), lipid metabolism (Network 2), hepatic system disease (Network 3 and 5), and inflammatory response (Network 4). When we merged these core diet-induced obesity networks, Tlr2, Cd14, and Ccnd1 emerged as hub genes associated with both liver steatosis and inflammation and were altered in a time-dependent manner. Further, protein-protein interaction network analysis revealed Tlr2, Cd14, and Ccnd1 were interrelated through the ErbB/insulin signaling pathway. Dynamic changes occur in molecular networks underlying diet-induced obesity. Tlr2, Cd14, and Ccnd1 appear to be hub genes integrating molecular interactions associated with the development of NASH. Therapeutics targeting hub genes and core diet-induced obesity networks may help ameliorate diet-induced obesity and NASH.

Nonalcoholic fatty liver disease and bariatric surgery

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease worldwide. Treatment recommendations for NAFLD are aimed towards weight reduction, thereby reducing insulin resistance. Unfortunately, lifestyle modifications have not yielded long-term success, while durable weight loss is routinely achieved with bariatric surgery. This article reviews the effects of bariatric surgery on patients with NAFLD. In these patients, postsurgical evaluations of liver histology by repeat liver biopsy are hindered by the risk of the procedure and the inherent sample variability, which makes the impact of bariatric surgery on NAFLD difficult to quantify. In longitudinal studies of NAFLD, the biopsy-based evaluations should be augmented by repeated measurements of the noninvasive biomarkers that may provide an insight into the changes in the physiological state of the liver after bariatric or other types of interventions. Nevertheless, currently available tests are not able to provide this type of in-depth outcome measures for these patients.

A systems biology approach for understanding the collagen regulatory network in alcoholic liver disease

Among the pathogenesis and risk factors of alcoholic liver disease (ALD) are the source of dietary fat, obesity, insulin resistance, adipokines and acetaldehyde. Translocation of Gram-negative bacteria from the gut, the subsequent effects mediated by endotoxin, and the increased production of matricellular proteins, cytokines, chemokines and growth factors, actively participate in the progression of liver injury. In addition, generation of reactive oxygen and nitrogen species and the activation of non-parenchymal cells also contribute to the pathophysiology of ALD. A key event leading to liver damage is the transition of quiescent hepatic stellate cells into activated myofibroblasts, with the consequent deposition of fibrillar collagen I resulting in significant scarring. Thus, it is becoming clearer that matricellular proteins are critical players in the pathophysiology of liver disease; however, additional mechanistic insight is needed to understand the signalling pathways involved in the up-regulation of collagen I protein. At present, systems biology approaches are helping to answer the many unresolved questions in this field and are allowing to more comprehensively identify protein networks regulating pathological collagen I deposition in hopes of determining how to prevent the onset of liver fibrosis and/or to slow disease progression. Thus, this review article provides a snapshot on current efforts for identifying pathological protein regulatory networks in the liver using systems biology tools. These approaches hold great promise for future research in liver disease.

Caffeine is protective in patients with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of metabolic syndrome, is the most common cause of primary liver disease. Although recent studies have found that coffee drinking is protective against end stage chronic liver disease, there are scarce caffeine intake data in NAFLD specifically.

AIM

To investigate the effects of dietary behaviour in NAFLD patients, using four continuous cycles of the National Health and Nutrition Examination Surveys (NHANES 2001-2008).

METHODS

Using data from four continuous cycles of NHANES, dietary intake questionnaires that list 62 nutrition components. Logistic regression was used to identify independent predictors of NAFLD among nutrition components after adjustment for potential clinical confounders. All analyses were run using sas 9.1 and SUDAAN 10.0 (SAS Institute Inc., Cary, NC, USA).

RESULTS

Of the 62 nutrient components used for the univariate analysis, 38% were significant (P-value <0.05) in NAFLD with caffeine consumption being higher in the control group (P-value <0.001). The multivariate analysis using demographics, clinical parameters and nutritional components found five factors independently associated with NAFLD [African American Race P-value <0.001); Male gender P-value <0.001); Obesity (BMI ≥ 30) P-value <0.001); Caffeine intake (mg) P-value <0.001) and total plain water consumption (g) P-value ≤ 0.02)].

CONCLUSIONS

Our analysis shows that caffeine intake is independently associated with a lower risk for NAFLD suggesting a potential protective effect. These data necessitate further research to elucidate the mechanism by which caffeine can protect against NAFLD.

Analysis of global and absorption, distribution, metabolism, and elimination gene expression in the progressive stages of human nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is characterized by a series of pathological changes that range from simple fatty liver to nonalcoholic steatohepatitis (NASH). The objective of this study is to describe changes in global gene expression associated with the progression of human NAFLD. This study is focused on the expression levels of genes responsible for the absorption, distribution, metabolism, and elimination (ADME) of drugs. Differential gene expression between three clinically defined pathological groups-normal, steatosis, and NASH-was analyzed. Genome-wide mRNA levels in samples of human liver tissue were assayed with Affymetrix GeneChip Human 1.0ST arrays. A total of 11,633 genes exhibited altered expression out of 33,252 genes at a 5% false discovery rate. Most gene expression changes occurred in the progression from steatosis to NASH. Principal component analysis revealed that hepatic disease status was the major determinant of differential ADME gene expression rather than age or sex of sample donors. Among the 515 drug transporters and 258 drug-metabolizing enzymes (DMEs) examined, uptake transporters but not efflux transporters or DMEs were significantly over-represented in the number of genes down-regulated. These results suggest that uptake transporter genes are coordinately targeted for down-regulation at the global level during the pathological development of NASH and that these patients may have decreased drug uptake capacity. This coordinated regulation of uptake transporter genes is indicative of a hepatoprotective mechanism acting to prevent accumulation of toxic intermediates in disease-compromised hepatocytes.

Blockade of IL-6 signaling exacerbates liver injury and suppresses antiapoptotic gene expression in methionine choline-deficient diet-fed db/db mice

Our previous study revealed that blockade of interleukin-6 (IL-6)-STAT3 signaling ameliorated liver injury, although hepatic STAT3(-/-) or GP130(-/-) mice have been reported to develop severe liver injury, in a murine methionine choline deficient (MCD) diet-induced model of non-alcoholic steatohepatitis (NASH). In this study, to determine whether profound blockade of IL-6-STAT3 signaling may still ameliorate liver injury, we studied db/db mice, which have impaired leptin-mediated STAT3 activation, using the MCD diet-induced NASH model. Male lean and db/db mice (6 weeks old) were fed either control chow or an MCD diet for 8 or 12 weeks. Half of the mice were treated with 15 mg/kg rat anti-mouse IL-6 receptor neutralizing antibody (MR16-1) intraperitoneally twice weekly, the remainder were injected with 15 mg/kg rat IgG as a control. Hepatic steatosis, injury, fibrosis, markers of lipid peroxidation/oxidant stress and antiapoptotic gene expression were evaluated. Plasma IL-6 levels were elevated in all groups of db/db mice. Although hepatic IL-6/ GP130 signaling was activated in chow-fed db/db mice, this was suppressed in MCD diet-fed db/db mice, accompanied by downregulation of hepatic IL-6 receptor and GP130 mRNA expression. MR16-1 treatment of MCD diet-fed db/db mice further repressed STAT3 activities and expression of STAT3-related antiapoptotic genes, such as Bcl-2 and Ref-1, but increased plasma-free fatty acid and hepatic markers of lipid peroxidation/oxidant stress, leading to increased liver injury, hepatocyte apoptosis and liver fibrosis. Although 'moderate' blockade of enhanced IL-6-STAT3 signaling may be beneficial in NASH, as we reported previously, these findings demonstrate that a profound defect in STAT3 activation is detrimental in terms of liver injury, hepatocyte apoptosis and liver fibrosis, indicating the hepato-protective role of IL-6 signaling in this severe NASH model.

Decreased immunoexpression of survivin could be a potential marker in human non-alcoholic fatty liver disease progression?

BACKGROUND/AIM

Regulation of apoptosis in non-alcoholic fatty liver disease (NAFLD) has been a theme of growing debate. Although no other study assessed the role of survivin in NAFLD, its expression has been reported in hepatic carcinogenesis because of other aetiological factors with relevant discrepancies. The aim of this study was to assess the pattern of survivin immunoexpression by tissue microarray along the whole spectrum of NAFLD, including non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC).

METHODS

Liver biopsies from 56 patients with NAFLD were evaluated: 18 with steatosis, 21 non-cirrhotic NASH, 10 NASH-related cirrhosis, seven NASH-related HCC, as compared with 71 HCC related to other causes and with 12 normal livers.

RESULTS

Survivin immunoexpression in NAFLD was restricted to cytoplasm and was found to be progressively lower in advanced stages, including cirrhosis and HCC: steatosis vs NASH-related cirrhosis (P=0.0243); steatosis vs NASH-related HCC (P=0.0010); NASH vs NASH-related cirrhosis (P=0.0318); and NASH vs NASH-related HCC (P=0.0007), thus suggesting a deregulation of apoptosis from NAFLD towards HCC. Interestingly, survivin immunoreactivity in NASH-related HCC was also found to be significantly lower than in HCC related to other causes (P<0.05). Remarkably, nuclear staining for survivin was not detected in any case of NAFLD, contrasting to its presence in all other cases of HCC.

CONCLUSIONS

Survivin immunoexpression in NASH-related HCC is herein originally found substantially different than in HCC related to other causes, thus requiring further studies to elucidate the role of survivin in human NAFLD progression.

Mirnome analysis reveals novel molecular determinants in the pathogenesis of diet-induced nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is an emerging disease with a broad spectrum of liver conditions. The complex molecular pathogenesis of NAFLD is still unclear. In this study, we conducted an analysis of microRNA (miRNA) expression profiles in liver of rats made NAFLD by different diets. To this aim, Sprague-Dawley rats were fed ad libitum for 3 months with different diets: standard diet (SD), diet enriched in fats and low in carbohydrates (HFD), SD with high fructose (SD-HF) and diet with high levels of fats and fructose (HFD-HF). Our results demonstrated that the treatment with different dietetic regimens caused a significant increase of the body weight and the alteration of some metabolic parameters compared with control animals, as well as various liver injuries. The miRNAs analysis showed the significant downregulation of three miRNAs (miR-122, miR-451 and miR-27) and the upregulation of miR-200a, miR-200b and miR-429 in HFD, SD-HF and HFD-HF rats. Besides, miR-21 expression was significantly decreased only in fructose-enriched diets. These miRNAs target molecules involved in the control of lipid and carbohydrate metabolism, signal transduction, cytokine and chemokine-mediated signaling pathway and apoptosis. Western blot analysis of PKCδ, LITAF, ALDOLASE-A, p38MAPK, PTEN, LIPIN1, EPHRIN-A1, EPHA2 and FLT1 showed a diet-induced deregulation of all these proteins. Interestingly, the expression pattern of LITAF, PTEN, LIPIN1, EPHRIN-A1, EPHA2 and FLT1 might be well explained by the trend of their specific mRNAs, by potentially regulatory miRNAs, or both. In conclusion, we highlight for the first time the potential involvement of novel determinants (miRNAs and proteins) in the molecular pathogenesis of diet-induced NAFLD.

Hepatic expression patterns of inflammatory and immune response genes associated with obesity and NASH in morbidly obese patients

BACKGROUND

Obesity modulates inflammation and activation of immune pathways which can lead to liver complications. We aimed at identifying expression patterns of inflammatory and immune response genes specifically associated with obesity and NASH in the liver of morbidly obese patients.

METHODOLOGY/PRINCIPAL FINDINGS

Expression of 222 genes was evaluated by quantitative RT-PCR in the liver of morbidly obese patients with histologically normal liver (n = 6), or with severe steatosis without (n = 6) or with NASH (n = 6), and in lean controls (n = 5). Hepatic expression of 58 out of 222 inflammatory and immune response genes was upregulated in NASH patients. The most notable changes occurred in genes encoding chemokines and chemokine receptors involved in leukocyte recruitment, CD and cytokines involved in the T cell activation towards a Th1 phenotype, and immune semaphorins. This regulation seems to be specific for the liver since visceral adipose tissue expression and serum levels of MCP1, IP10, TNFα and IL6 were not modified. Importantly, 47 other genes were already upregulated in histologically normal liver (e.g. CRP, Toll-like receptor (TLR) pathway). Interestingly, serum palmitate, known to activate the TLR pathway, was increased with steatosis.

CONCLUSION/SIGNIFICANCE

The liver of obese patients without histological abnormalities already displayed a low-grade inflammation and could be more responsive to activators of the TLR pathway. NASH was then characterized by a specific gene signature. These findings help to identify new potential actors of the pathogenesis of NAFLD.

Blockade of interleukin-6 signaling enhances hepatic steatosis but improves liver injury in methionine choline-deficient diet-fed mice

Inflammatory processes have an important role in the development of hepatic steatosis and progression to nonalcoholic steatohepatitis (NASH). Interleukin-6 (IL-6) is known to be a proinflammatory cytokine, but also promotes liver regeneration and protects the liver against various forms of damage. The role of IL-6/Glycoprotein 130 (GP130) in NASH remains unclear. In this study, we determined whether blocking IL-6/GP130 signaling prevents progression of steatohepatitis in a mouse NASH model. Six-week-old male C57/BL6 mice were fed either chow control or a methionine choline-deficient (MCD) diet for 8 weeks. Half of the MCD diet-fed mice were treated with 15 mg/kg rat anti-mouse IL-6 receptor antibody (MR16-1), intraperitoneally twice weekly, the remainder and chow-fed mice were injected with 15 mg/kg rat IgG as a control. Hepatic steatosis, injury, fibrosis, apoptosis, markers of lipid peroxidation/oxidant stress and IL-6-related gene expressions were evaluated. MR16-1 treatment decreased signal transducer and activator of transcription 3 activities and expression of suppressor of cytokine signaling 3 in MCD diet-treated mouse livers. Although this treatment enhanced intrahepatic lipid accumulation accompanied by increased sterol regulatory element-binding protein 1 and decreased peroxisome proliferator-activated receptor-alpha expression, elevated plasma alanine aminotransferase levels were improved with decreased plasma free fatty acid levels, lipid peroxidation/oxidant stress and hepatic apoptosis. Blocking IL-6/GP130 signaling by MR16-1 enhanced MCD diet-induced hepatic steatosis, but ameliorated liver injury. These findings suggest that hepatic IL-6 signaling has a protective role against the progression of hepatic steatosis but may enhance liver inflammation.

Differential expression of miRNAs in the visceral adipose tissue of patients with non-alcoholic fatty liver disease

BACKGROUND

Progression of non-alcoholic fatty liver disease (NAFLD) can be facilitated by soluble molecules secreted by visceral adipose tissue (VAT). MicroRNAs (miRNAs) are likely to regulate some of these molecular pathways involved in pathogenesis of NAFLD.

AIM

To profile miRNA expression in the visceral adipose tissue of patients with NAFLD.

METHODS

Visceral adipose tissue samples were collected from NAFLD patients and frozen. Patients with biopsy-proven NAFLD were divided into non-alcoholic steatohepatitis (NASH) (n = 12) and non-NASH (n = 12) cohorts controlled for clinical and demographic characteristics. Extracted total RNA was profiled using TaqMan Human MicroRNA arrays. Univariate Mann-Whitney comparisons and multivariate regression analysis were performed to compare miRNA profiles.

RESULTS

A total of 113 miRNA differentially expressed between NASH patients and non-NASH patients (P < 0.05). Of these, seven remained significant after multiple test correction (hsa-miR-132, hsa-miR-150, hsa-miR-433, hsa-miR-28-3p, hsa-miR-511, hsa-miR-517a, hsa-miR-671). Predicted target genes for these miRNAs include insulin receptor pathway components (IGF1, IGFR13), cytokines (CCL3, IL6), ghrelin/obestatin gene, and inflammation-related genes (NFKB1, RELB, FAS). In addition, two miRNA species, hsa-miR-197 and hsa-miR-99, were significantly associated with pericellular fibrosis in NASH patients (P < 0.05). Levels of IL-6 in the serum negatively correlated with the expression levels of all seven miRNAs capable of down regulating IL-6 encoding gene.

CONCLUSIONS

miRNA expression from VAT may contribute to the pathogenesis of NAFLD - a finding which may distinguish relatively simple steatosis from NASH. This could help identify potential targets for pharmacological treatment regimens and candidate biomarkers for NASH.

Lack of interleukin-6/glycoprotein 130/signal transducers and activators of transcription-3 signaling in hepatocytes predisposes to liver steatosis and injury in mice

A deregulated cytokine balance is involved in triggering the sequence from steatosis to nonalcoholic steatohepatitis, ultimately leading to liver fibrosis and cancer. To better define the role of proinflammatory interleukin-6 (IL-6)-type cytokines in hepatocytes we investigated the role of IL-6 and its shared receptor, glycoprotein 130 (gp130), in a mouse model of steatohepatitis. IL-6(-/-) mice were fed a choline-deficient, ethionine-supplemented (CDE) diet. Conditional gp130 knockout and knockin mice were used to achieve hepatocyte-specific deletion of gp130 (gp130(Deltahepa)), gp130-dependent rat sarcoma (Ras)-(gp130(DeltahepaRas)), and signal transducers and activators of transcription (STAT)-(gp130(DeltahepaSTAT)) activation. CDE-treated IL-6(-/-) mice showed a significant hepatic steatosis at 2 weeks after feeding. The mice rapidly developed elevated fasting blood glucose, insulin serum levels, and transaminases. To better define IL-6-dependent intracellular pathways, specifically in hepatocytes, we next treated gp130(Deltahepa) mice with a CDE diet. These animals also developed a marked steatosis with hyperglycemia and displayed elevated insulin serum levels. Additionally, gp130(Deltahepa) animals showed an imbalanced inflammatory response with increased hepatic tumor necrosis factor-alpha and decreased adiponectin messenger RNA levels. Dissecting the hepatocyte-specific gp130-dependent pathways revealed a similar disease phenotype in gp130(DeltahepaSTAT) mice, whereas gp130(DeltahepaRas) animals were protected. In CDE-treated mice lack of gp130-STAT3 signaling was associated with immune-cell-infiltration, jun kinase-activation, a blunted acute-phase-response, and elevated transaminases. Furthermore, gp130(Deltahepa) and gp130(DeltahepaSTAT) mice showed beginning signs of liver fibrosis compared to gp130(DeltahepaRas) mice and controls.

CONCLUSION

During CDE treatment mice lacking IL-6 and gp130-STAT signaling in hepatocytes are prone to hepatic metabolic changes and inflammation. This ultimately leads to progressive steatohepatitis with signs of liver remodeling. Thus, the presented model allows one to further dissect the role of IL-6/gp130-type signaling in hepatocytes during fatty liver degeneration to define new therapeutic targets in metabolic liver diseases.

Expression of cytokine signaling genes in morbidly obese patients with non-alcoholic steatohepatitis and hepatic fibrosis

BACKGROUND

White adipose tissue (WAT) from visceral adiposity plays an important role in the pathogenesis of non-alcoholic steatohepatitis (NASH). Development of NASH and its progression to fibrosis is partially due to cytokines and adipokines produced by WAT. The aim of this study was to assess the association of hepatic fibrosis and NASH by evaluating the intrinsic differences in the inflammatory cytokine signaling in the visceral adipose tissue obtained from morbidly obese patients.

METHODS

We used targeted microarrays representing human genes involved in the inflammatory and fibrogenic reactions to profile visceral adipose samples of 15 well-matched NASH patients with and without fibrosis. Additionally, visceral adipose samples were subjected to real-time polymerase chain reaction profiling of 84 inflammations related genes.

RESULTS

Eight genes (CCL2, CCL4, CCL18, CCR1, IL10RB, IL15RA, and LTB) were differentially expressed in NASH with fibrosis. Additionally, an overlapping but distinct list of the differentially expressed genes were found in NASH with type II diabetes (DM; IL8, BLR1, IL2RA, CD40LG, IL1RN, IL15RA, and CCL4) as compared to NASH without DM.

CONCLUSIONS

Inflammatory cytokines are differentially expressed in the adipose tissue of NASH with fibrosis, as well in NASH with DM. These findings point at the interaction of adipose inflammatory cytokines, DM, hepatic fibrosis in NASH, and its progression to cirrhosis and end-stage liver disease.

Hepatitis C, insulin resistance and diabetes: clinical and pathogenic data

Epidemiological data indicate a strong risk for development of insulin resistance (IR), and, ultimately, overt diabetes mellitus (DM) in patients with chronic hepatitis C virus (HCV) infection. Steatosis, or fatty liver, is closely linked with IR in persons without HCV, such as those with metabolic syndrome, primarily due to increased visceral fat leading to altered adipokine production and increased free fatty acid (FFA) release. Moreover, there is evidence that liver fat can have an impact on the development of hepatic IR independently of changes in adipose tissue. Multiple mechanisms can account for the development of IR in patients with chronic HCV. In particular, there is evidence for a triangular interaction between steatosis, inflammatory processes and IR. In patients infected by the genotype 1 virus, steatosis is strongly related to IR, leading to a metabolic steatosis, while, in genotype 3 patients, steatosis is related to viral load in the context of a viral steatosis. Chronic inflammatory processes in the liver may be mediated by persistently activated macrophages and other immune cells, with concomitant overproduction of pro-inflammatory cytokines such as tumour necrosis factor-alpha. Activation of inflammatory pathways, together with increased levels of FFAs, can disrupt hepatocyte intracellular pathways and inhibit insulin signalling, leading to IR. Molecular studies have also shown that the HCV core protein can directly inhibit the insulin signalling pathway and increase reactive oxygen species production, both of which can further exacerbate IR. The available data provide an understanding of chronic HCV whereby chronic inflammatory processes, steatosis and IR contribute to each other, leading to an increased risk of DM, and its associated poor outcomes, in persons with chronic HCV.

Gene expression in human NAFLD

Despite the high prevalence of nonalcoholic fatty liver disease (NAFLD), little is known of its pathogenesis based on study of human liver samples. By the use of Affymetrix GeneChips (17,601 genes), we investigated gene expression in the human liver of subjects with extreme steatosis due to NAFLD without histological signs of inflammation (liver fat 66.0 +/- 6.8%) and in subjects with low liver fat content (6.4 +/- 2.7%). The data were analyzed by using sequence-based reannotation of Affymetrix probes and a robust model-based normalization method. We identified genes involved in hepatic glucose and lipid metabolism, insulin signaling, inflammation, coagulation, and cell adhesion to be significantly associated with liver fat content. In addition, genes involved in ceramide signaling (MAP2K4) and metabolism (UGCG) were found to be positively associated with liver fat content. Genes involved in lipid metabolism (PLIN, ACADM), fatty acid transport (FABP4, CD36), amino acid catabolism (BCAT1), and inflammation (CCL2) were validated by real-time PCR and were found to be upregulated in subjects with high liver fat content. The data show that multiple changes in gene expression characterize simple steatosis.