X.-Y. Wang

Comparison of Gene Expression Patterns Between Mouse Models of Nonalcoholic Fatty Liver Disease and Liver Tissues From Patients

BACKGROUND & AIMS Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder in industrialized countries. Mouse models of NAFLD have been used in studies of pathogenesis and treatment, and have certain features of the human disease. We performed a systematic transcriptome-wide analysis of liver tissues from patients at different stages of NAFLD progression (ranging from healthy obese individuals to those with steatosis), as well as rodent models of NAFLD, to identify those that most closely resemble human disease progression in terms of gene expression patterns. METHODS We performed a systematic evaluation of genome-wide messenger RNA expression using liver tissues collected from mice fed a standard chow diet (controls) and 9 mouse models of NAFLD: mice on a high-fat diet (with or without fructose), mice on a Western-type diet, mice on a methionine- and choline-deficient diet, mice on a high-fat diet given streptozotocin, and mice with disruption of Pten in hepatocytes. We compared gene expression patterns with those of liver tissues from 25 patients with nonalcoholic steatohepatitis (NASH), 27 patients with NAFLD, 15 healthy obese individuals, and 39 healthy nonobese individuals (controls). Liver samples were obtained from patients undergoing liver biopsy for suspected NAFLD or NASH, or during liver or bariatric surgeries. Data sets were analyzed using the limma R-package. Overlap of functional profiles was analyzed by gene set enrichment analysis profiles. RESULTS We found differences between human and mouse transcriptomes to be significantly larger than differences between disease stages or models. Of the 65 genes with significantly altered expression in patients with NASH and 177 genes with significantly altered expression in patients with NAFLD, compared with controls, only 1-18 of these genes also differed significantly in expression between mouse models of NAFLD and control mice. However, expression of genes that regulate pathways associated with the development of NAFLD were altered in some mouse models (such as pathways associated with lipid metabolism). On a pathway level, gene expression patterns in livers of mice on the high-fat diet were associated more closely with human fatty liver disease than other models. CONCLUSIONS In comparing gene expression profiles between liver tissues from different mouse models of NAFLD and patients with different stages of NAFLD, we found very little overlap. Our data set is available for studies of pathways that contribute to the development of NASH and NAFLD and selection of the most applicable mouse models (http://www.nash-profiler.com).

Inducible knockdown of procollagen I protects mice from liver fibrosis and leads to dysregulated matrix genes and attenuated inflammation

Organ fibrosis is characterized by a chronic wound-healing response, with excess deposition of extracellular matrix components. Here, collagen type I represents the most abundant scar component and a primary target for antifibrotic therapies. Liver fibrosis can progress to cirrhosis and primary liver cancer, which are the major causes of liver related morbidity and mortality. However, a (pro-)collagen type I specific therapy remains difficult and its therapeutic abrogation may incur unwanted side effects. We therefore designed tetracycline-regulated procollagen alpha1(I) short hairpin (sh)RNA expressing mice that permit a highly efficient inducible knockdown of the procollagen alpha1(I) gene in activated (myo-)fibroblasts, to study the effect of induced procollagen type I deficiency. Transgenic mice were generated using recombinase-mediated integration in embryonic stem cells or zinc-finger nuclease-aided genomic targeting combined with miR30-shRNA technology. Liver fibrosis was induced in transgenic mice by carbon tetrachloride, either without or with doxycycline supplementation. Doxycycline treated mice showed an 80-90% suppression of procollagen alpha1(I) transcription and a 40-50% reduction in hepatic collagen accumulation. Procollagen alpha1(I) knockdown also downregulated procollagens type III, IV and VI and other fibrosis related parameters. Moreover, this was associated with an attenuation of chronic inflammation, suggesting that collagen type I serves not only as major scar component, but also as modulator of other collagens and promoter of chronic inflammation.

Determinants of fibrosis progression and regression in NASH

Cirrhosis has become the major liver-related clinical endpoint in non-alcoholic steatohepatitis (NASH). However, progression to cirrhosis is less predictable in NASH than in other chronic liver diseases. This is due to the complex and multifactorial aetiology of NASH, which is determined by lifestyle and nutrition, multiple genetic and epigenetic factors, and a prominent role of hepatic and extrahepatic comorbidities. Thus, modest changes in these cofactors can also induce fibrosis regression, at least in patients with precirrhotic liver disease. Fibrogenesis in NASH correlates with, but is indirectly coupled to, classical inflammation, since fibrosis progression is driven by repetitive periods of repair. While hepatocyte lipoapoptosis is a key driving force of fibrosis progression, activated hepatic stellate cells, myofibroblasts, cholangiocytes, macrophages and components of the pathological extracellular matrix are major fibrogenic effectors and thus pharmacological targets for therapies aimed at inhibition of fibrosis progression or induction of fibrosis reversal. The advent of novel, highly sensitive and specific serum biomarkers and imaging methods to assess the dynamics of liver fibrosis in NASH will improve detection, stratification and follow-up of patients with progressive NASH . These non-invasive tools will also promote the clinical development of antifibrotic drugs, by permitting the design of lean proof-of-concept studies, and enabling development of a personalised antifibrotic therapy for patients with rapid fibrosis progression or advanced disease.

IL-4 Receptor Alpha Signaling through Macrophages Differentially Regulates Liver Fibrosis Progression and Reversal

Chronic hepatitis leads to liver fibrosis and cirrhosis. Cirrhosis is a major cause of worldwide morbidity and mortality. Macrophages play a key role in fibrosis progression and reversal. However, the signals that determine fibrogenic vs fibrolytic macrophage function remain ill defined. We studied the role of interleukin-4 receptor α (IL-4Rα), a potential central switch of macrophage polarization, in liver fibrosis progression and reversal. We demonstrate that inflammatory monocyte infiltration and liver fibrogenesis were suppressed in general IL-4Rα−/− as well as in macrophage-specific IL-4Rα−/− (IL-4RαΔLysM) mice. However, with deletion of IL-4RαΔLysM spontaneous fibrosis reversal was retarded. Results were replicated by pharmacological intervention using IL-4Rα-specific antisense oligonucleotides. Retarded resolution was linked to the loss of M2-type resident macrophages, which secreted MMP-12 through IL-4 and IL-13-mediated phospho-STAT6 activation. We conclude that IL-4Rα signaling regulates macrophage functional polarization in a context-dependent manner. Pharmacological targeting of macrophage polarization therefore requires disease stage-specific treatment strategies. Research in Context Alternative (M2-type) macrophage activation through IL-4Rα promotes liver inflammation and fibrosis progression but speeds up fibrosis reversal. This demonstrates context dependent, opposing roles of M2-type macrophages. During reversal IL-4Rα induces fibrolytic MMPs, especially MMP-12, through STAT6. Liver-specific antisense oligonucleotides efficiently block IL-4Rα expression and attenuate fibrosis progression.

P0926 : Representation of human non-alcoholic fatty liver disease in murine models

COX-2 enhances insulin signaling. Finally, the relationship between COX-2 and the miRNAs was confirmed in NAS. Conclusions: COX-2 represses the expression of miRNAs implicated in the insulin signaling pathway via a PI3K/p300-dependent upregulation of DDX5, and by modulating the activity of the Drosha complex. Our study proposes a novel miRNA-dependent mechanism through which COX-2 promotes insulin signaling in liver cells.

Su1807 Nutritional Wheat Alpha-Amylase Trypsin Inhibitors (ATIS) Synergize With a High Fat Diet to Worsen Non-Alcoholic Fatty Liver Disease

Background: The prognosis of nonalcoholic fatty liver disease (NAFLD) is largely dependent on the severity of hepatic fibrosis. Macrophage and Kupffer cell activation correlates with hepatic fibrosis in chronic viral hepatitis. Apoptosis inhibitor of macrophage (AIM) supports survival of macrophages and soluble CD163 (sCD163) is a marker of macrophage activation. The aim of this study was to assess the relationship between markers of macrophage activation and survival and the presence of advanced fibrosis in adult patients with NAFLD. Methods: Patients with biopsy-proven NAFLD were enrolled in the study. Venous blood was collected from the patients on the day of the biopsy. Patients were divided into 2 groups: early stage fibrosis (F0-2) and advanced fibrosis (F3-4) based on Metavir score as assessed by an independent pathologist. Serum levels of AIM and CD 163 were measured using specific ELISAs. Comparisons between the groups were analyzed by MannWhitney U test and the data expressed as mean ± standard deviation. A p<0.05 was considered significant. Results: 40 patients were included (24 with stage 0-2 fibrosis and 16 with advanced fibrosis (F34) with a mean age of 54± 9.4 years and 32.5% were male. Patients with advanced fibrosis were more likely to have type 2 diabetes and had significantly higher AST/ALT ratio than those F0-2 (p = 0.041). More importantly, serum AIM levels were significantly higher in patients with advanced fibrosis than those with F0-2 (2042 ± 764 ng/ml and 1216± 580 ng/ml, respectively; p<0.001) with an area under the ROC curve (AUC) for predicting the presence of advanced fibrosis of 0.782 (95% CI: 0.635 -0.929). Similarly, serum sCD163 levels were significantly higher in patients with F3-4 (1722 ± 916 ng/ml) compared to those without advanced fibrosis (930 ± 433 ng/ml); p<0.001 with an AUC for predicting advanced fibrosis of 0.756 (0.589-0.922). Conclusion: Taken together, our data suggest that decreased apoptosis of macrophages leading to their increased activity as evident by high AIM and CD 163 levels plays a central role in fibrosis progression in subjects with NAFLD.