Connective tissue growth factor, steatosis and fibrosis in patients with chronic hepatitis C

Serum level of full-length connective tissue growth factor reflects liver fibrosis stage in patients with Fontan-associated liver disease

BACKGROUND

Chronic liver disease leads to liver fibrosis, and an accurate diagnosis of the fibrosis stage is crucial for medical management. Connective tissue growth factor (CTGF) is produced by endothelial cells and platelets and plays a central role in inducing fibrosis in various organs. In the present study, we tested the validity of measuring the serum levels of two types of CTGF to estimate the biopsy-confirmed liver fibrosis stage.

METHODS

We used two detection antibodies targeting the N- and C-terminal of CTGF to measure the serum levels of two forms of CTGF consisting of its full length and its N-terminal fragment. We analyzed the level of CTGF (via enzyme-linked immunosorbent assay) and the liver fibrosis stage in 38 patients with Fontan-associated liver disease (FALD) (26 cases of which were diagnosed pathologically). Correlations were determined by multivariate analysis and the area under the receiver operating characteristic curve. The 65 patients with nonalcoholic fatty liver disease (NAFLD) were included as a disease control group for examination.

RESULTS

Full-length CTGF was significantly inversely correlated with liver fibrosis in patients with FALD. Although the platelet count was also associated with the liver fibrosis stage, full-length CTGF was more closely correlated with the fibrosis stage. Furthermore, the level of full-length CTGF was inversely associated with high central venous pressure. Conversely, the serum level of CTGF was not correlated with the fibrosis stage in NAFLD.

CONCLUSION

The serum level of full-length CTGF may be useful for estimating the liver fibrosis stage in patients with FALD.

Molecular Crosstalk between the Hepatitis C Virus and the Extracellular Matrix in Liver Fibrogenesis and Early Carcinogenesis

Simple Summary

In the era of direct-acting antivirals against the hepatitis C virus (HCV), curing chronic hepatitis C has become a reality. However, while replicating chronically, HCV creates a peculiar state of inflammation and oxidative stress in the infected liver, which fuels DNA damage at the onset of HCV-induced hepatocellular carcinoma (HCC). This cancer, the second leading cause of death by cancer, remains of bad prognosis when diagnosed. This review aims to decipher how HCV durably alters elements of the extracellular matrix that compose the liver microenvironment, directly through its viral proteins or indirectly through the induction of cytokine secretion, thereby leading to liver fibrosis, cirrhosis, and, ultimately, HCC.

Abstract

Chronic infection by the hepatitis C virus (HCV) is a major cause of liver diseases, predisposing to fibrosis and hepatocellular carcinoma. Liver fibrosis is characterized by an overly abundant accumulation of components of the hepatic extracellular matrix, such as collagen and elastin, with consequences on the properties of this microenvironment and cancer initiation and growth. This review will provide an update on mechanistic concepts of HCV-related liver fibrosis/cirrhosis and early stages of carcinogenesis, with a dissection of the molecular details of the crosstalk during disease progression between hepatocytes, the extracellular matrix, and hepatic stellate cells.

Role of fibrogenic and inflammatory cytokines in HCV-induced fibrosis

HCV is one of the main causative agents of liver fibrosis and hepatocellular carcinoma. Liver inflammation resulting from HCV infection triggers fibrosis. In HCV-related fibrosis, differentiated hepatic stellate cells (HSCs) known as myofibroblasts participate in the fibrogenic and inflammatory response. TGF-β1 and CTGF, released from these HSCs, have been implicated as master cytokines mediating HCV induced hepatic fibrosis. PDGF is another potent mitogen, which facilitates the progression of liver fibrosis by enhancing the proliferation and migration of HSCs. In addition to these major cytokines, the release of TNF-α, IL-6, IL-1b and IL-10 by immune cells also promotes the effect of HCV induced fibrosis. Targeting these cytokines may offer the potential for treatments to prevent or cure fibrosis.

Protein extracts of Crassostrea gigas alleviate CCl₄-induced hepatic fibrosis in rats by reducing the expression of CTGF, TGF-β1 and NF-κB in liver tissues

Hepatic fibrosis may contribute to liver carcinoma and the mortality of patients with hepatic fibrosis is gradually increasing. However, no definitive treatment has been established for hepatic fibrosis. The hepatic fibrotic process is reversible and can be controlled; therefore, the creation of novel and effective therapeutic methods to prevent or reverse the disease is required. The aim of the present study was to identify whether protein extracts from Pacific oysters (PEPO) could alleviate the hepatic fibrosis induced by CCl4 and to examine the mechanisms involved. A total of sixty rats were randomly divided into the following experimental groups: The normal control group; the hepatic fibrosis model group; the high‑dose; medium‑dose; and low‑dose PEPO groups; and the colchicine group. The results indicated that compared with those of the model group, PEPO treatment significantly decreased the serum levels of alanine aminotransferase, aspartate aminotransferase, γ‑glutamyltransferase, alkaline phosphatase, hyaluronic acid, laminin, collagen type IV and procollagen III in rats with hepatic fibrosis. The hematoxylin and eosin staining demonstrated that PEPO markedly alleviated hepatic fibrosis. The experiments using immunohistochemistry, western blotting and quantitative PCR indicated that protein and mRNA expression levels of connective tissue growth factor (CTGF), transforming growth factor β1 (TGFβ‑1) and nuclear factor κB (NF‑κB) in the liver tissues were significantly reduced by PEPO treatment. Therefore, it was concluded that PEPO successfully alleviated hepatic fibrosis induced by CCl4 and reversed the effects of hepatotoxicity by regulating the serum levels of enzymes and decreasing the expression levels of CTGF, TGF‑β1 and NF‑κB in liver tissues. These findings may provide a novel treatment option for patients with hepatic fibrosis in the future.

Chunggan extract, a traditional herbal formula, ameliorated alcohol-induced hepatic injury in rat model

AIM: To evaluate protective effects of Chunggan extract (CGX), a traditional herbal formula, under 4 wk of alcohol consumption-induced liver injury.

METHODS: Male Sprague-Dawley Rats were orally administered 30% ethanol daily for 4 wk with or without CGX. The pharmaceutical properties were assessed through liver enzymes, histopathology, fibrogenic cytokines, and alcohol metabolism in hepatic tissues as well as by in vitro experiment using HSC-T6 cells.

RESULTS: Four weeks of alcohol consumption notably increased liver enzymes and malondialdehyde levels in serum and hepatic tissue. CGX not only prevented the collagen deposition determined by histopathology and hydroxyproline content, but also normalized transforming growth factor-beta, platelet-derived growth factor-beta and connective tissue growth factor at the gene expression and protein levels in liver tissue. Moreover, CGX treatment also significantly normalized the abnormal changes in gene expression profiles of extracellular matrix proteins, matrix metalloproteinase and their inhibitors, alcohol metabolism, and inflammatory reactions. In the acetaldehyde-stimulated HSC-T6 cells, CGX considerably inhibited collagen production and normalized fibrogenic cytokines in both gene expression and protein levels.

CONCLUSION: The present study evidenced that CGX has hepatoprotective properties via modulation of fibrogenic cytokines and alcohol metabolism in alcoholic liver injury.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Pathogenesis and significance of hepatitis C virus steatosis: An update on survival strategy of a successful pathogen

Hepatitis C virus (HCV) is a successful pathogen on the grounds that it exploits its host’s metabolism to build up viral particles; moreover it favours its own survival by inducing chronic disease and the development of specific anatomic changes in the infected organ. Steatosis, therefore, is associated with HCV infection by necessity rather than by chance alone. Approximately 6% of HCV patients have steatohepatitis. Interestingly, HCV steatosis occurs in the setting of multiple metabolic abnormalities (hyperuricemia, reversible hypocholesterolemia, insulin resistance, arterial hypertension and expansion of visceral adipose tissue) collectively referred to as “hepatitis C-associated dysmetabolic syndrome” (HCADS). General, nonalcoholic fatty liver disease (NAFLD)-like, mechanisms of steatogenesis (including increased availability of lipogenic substrates and de novo lipogenesis; decreased oxidation of fatty substrates and export of fatty substrates) are shared by all HCV genotypes. However, genotype 3 seemingly amplifies such steatogenic molecular mechanisms reported to occur in NAFLD via more profound changes in microsomal triglyceride transfer protein; peroxisome proliferator-activated receptor alpha; sterol regulatory element-binding proteins and phosphatase and tensin homologue. HCV steatosis has a remarkable clinical impact in as much as it is an acknowledged risk factor for accelerated fibrogenesis; for impaired treatment response to interferon and ribavirin; and development of hepatocellular carcinoma. Recent data, moreover, suggest that HCV-steatosis contributes to premature atherogenesis via both direct and indirect mechanisms. In conclusion, HCV steatosis fulfills all expected requirements necessary to perpetuate the HCV life cycle. A better understanding of the physiology of HCADS will likely result in a more successful handling of disease with improved antiviral success rates.

Epigenetic regulation of connective tissue growth factor by MicroRNA-214 delivery in exosomes from mouse or human hepatic stellate cells

Connective tissue growth factor (CCN2) drives fibrogenesis in hepatic stellate cells (HSC). Here we show that CCN2 up-regulation in fibrotic or steatotic livers, or in culture-activated or ethanol-treated primary mouse HSC, is associated with a reciprocal down-regulation of microRNA-214 (miR-214). By using protector or reporter assays to investigate the 3'-untranslated region (UTR) of CCN2 mRNA, we found that induction of CCN2 expression in HSC by fibrosis-inducing stimuli was due to reduced expression of miR-214, which otherwise inhibited CCN2 expression by directly binding to the CCN2 3'-UTR. Additionally, miR-214 was present in HSC exosomes, which were bi-membrane vesicles, 50-150 nm in diameter, negatively charged (-26 mV), and positive for CD9. MiR-214 levels in exosomes but not in cell lysates were reduced by pretreatment of the cells with the exosome inhibitor, GW4869. Coculture of either quiescent HSC or miR-214-transfected activated HSC with CCN2 3'-UTR luciferase reporter-transfected recipient HSC resulted in miR-214- and exosome-dependent regulation of a wild-type CCN2 3'-UTR reporter but not of a mutant CCN2 3'-UTR reporter lacking the miR-214 binding site. Exosomes from HSC were a conduit for uptake of miR-214 by primary mouse hepatocytes. Down-regulation of CCN2 expression by miR-214 also occurred in human LX-2 HSC, consistent with a conserved miR-214 binding site in the human CCN2 3'-UTR. MiR-214 in LX-2 cells was shuttled by way of exosomes to recipient LX-2 cells or human HepG2 hepatocytes, resulting in suppression of CCN2 3'-UTR activity or expression of CCN2 downstream targets, including alpha smooth muscle actin or collagen. Experimental fibrosis in mice was associated with reduced circulating miR-214 levels.

CONCLUSION

Exosomal transfer of miR-214 is a paradigm for the regulation of CCN2-dependent fibrogenesis and identifies fibrotic pathways as targets of intercellular regulation by exosomal miRs.

Transforming growth factor-β (TGF-β)-mediated connective tissue growth factor (CTGF) expression in hepatic stellate cells requires Stat3 signaling activation

In fibrotic liver, connective tissue growth factor (CTGF) is constantly expressed in activated hepatic stellate cells (HSCs) and acts downstream of TGF-β to modulate extracellular matrix production. Distinct from other cell types in which Smad signaling plays major role in regulating CTGF production, TGF-β stimulated CTGF expression in activated HSCs is only in part dependent on Smad3. Other signaling molecules like MAPKs and PI3Ks may also participate in this process, and the underlying mechanisms have yet to be clarified. In this study, we report involvement of Stat3 activation in modulating CTGF production upon TGF-β challenge in activated HSCs. Stat3 is phosphorylated via JAK1 and acts as a critical ALK5 (activin receptor-like kinase 5) downstream signaling molecule to mediate CTGF expression. This process requires de novo gene transcription and is additionally modulated by MEK1/2, JNK, and PI3K pathways. Cell-specific knockdown of Smad3 partially decreases CTGF production, whereas it has no significant influence on Stat3 activation. The total CTGF production induced by TGF-β in activated HSCs is therefore, to a large extent, dependent on the balance and integration of the canonical Smad3 and Stat3 signaling pathways.

Solute carrier family 2 member 1 is involved in the development of nonalcoholic fatty liver disease

Susceptibility to develop nonalcoholic fatty liver disease (NAFLD) has genetic bases, but the associated variants are uncertain. The aim of the present study was to identify genetic variants that could help to prognose and further understand the genetics and development of NAFLD. Allele frequencies of 3,072 single-nucleotide polymorphisms (SNPs) in 92 genes were characterized in 69 NAFLD patients and 217 healthy individuals. The markers that showed significant allele-frequency differences in the pilot groups were subsequently studied in 451 NAFLD patients and 304 healthy controls. Besides this, 4,414 type 2 diabetes mellitus (T2DM) cases and 4,567 controls were genotyped. Liver expression of the associated gene was measured and the effect of its potential role was studied by silencing the gene in vitro. Whole genome expression, oxidative stress (OS), and the consequences of oleic acid (OA)-enriched medium on lipid accumulation in siSLC2A1-THLE2 cells were studied by gene-expression analysis, dihydroethidium staining, BODIPY, and quantification of intracellular triglyceride content, respectively. Several SNPs of SLC2A1 (solute carrier family 2 [facilitated glucose transporter] member 1) showed association with NAFLD, but not with T2DM, being the haplotype containing the minor allele of SLC2A1 sequence related to the susceptibility to develop NAFLD. Gene-expression analysis demonstrated a significant down-regulation of SLC2A1 in NAFLD livers. Enrichment functional analyses of transcriptome profiles drove us to demonstrate that in vitro silencing of SLC2A1 induces an increased OS activity and a higher lipid accumulation under OA treatment.

CONCLUSIONS

Genetic variants of SLC2A1 are associated with NAFLD, and in vitro down-regulation of this gene promotes lipid accumulation. Moreover, the oxidative response detected in siSLC2A1-THLE2 cells corroborated the antioxidant properties previously related to this gene and linked the most representative clinical characteristics of NAFLD patients: oxidative injury and increased lipid storage.

Intrahepatic mRNA levels of SOCS1 and SOCS3 are associated with cirrhosis but do not predict virological response to therapy in chronic hepatitis C

BACKGROUND

Antiviral treatment of chronic hepatitis C is not invariably successful, costly and associated with serious side-effects, and therefore should be indicated only when the chances of benefitting patients exceed the potential risks. The suppressor of cytokine signalling (SOCS) family members have been suggested to affect the rate of virological response to therapy, but the published evidence is conflicting.

METHODS

We measured the intrahepatic SOCS1, SOCS3 and SOCS7 mRNA levels in 107 chronic hepatitis C patients and assessed their clinical and histological correlates with the virological response to therapy and with some factors known for affecting treatment outcome.

RESULTS

By multivariate analysis, SOCS1, SOCS3 and SOCS7 mRNA levels were not associated with rapid or sustained virological response. Similarly, no association was found between the levels of any intrahepatic SOCS mRNA and those of the homeostasis model assessment of insulin resistance. Conversely, SOCS1 (OR 2.185, 95% CI 1.223-3.906, P=0.0083) and SOCS3 (OR 40.601, 95% CI 2.357-699.25, P=0.0108) mRNA level (but not SOCS7), together with age (OR 1.156, 95% CI 1.049-1.275, P=0.0036), were independently associated with cirrhosis.

CONCLUSIONS

Intrahepatic SOCS1, SOCS3 and SOCS7 mRNA levels do not predict virological response to therapy in chronic hepatitis C. The association between SOCS1, SOCS3 and cirrhosis warrants further study.

Current understanding of insulin resistance in hepatitis C

Important breakthroughs have been made in recent years into understanding the close interaction between hepatitis C virus (HCV) infection and glucose homeostasis. Both cross-sectional and longitudinal studies have demonstrated that infection with HCV is associated with an increased risk of developing insulin resistance and Type 2 diabetes. A direct effect of HCV on hepatocyte insulin signaling has been shown in experimental models. Some preliminary observations seem to suggest that indirect mechanisms involving extrahepatic organs might also play a role. The interaction between HCV and glucose metabolism has significant clinical consequences. Insulin resistance and Type 2 diabetes not only accelerate the histological and clinical progression of chronic hepatitis C, but also reduce the virological response to IFN-α-based therapy. Thus, understanding the mechanisms underlying HCV-associated glucose metabolism derangements is of paramount interest in order to improve the clinical management of chronic hepatitis C. This article will focus on the studies that consistently argue in favor of an interrelation between HCV and insulin resistance and will highlight the latest discoveries in this field.

Increases in p53 expression induce CTGF synthesis by mouse and human hepatocytes and result in liver fibrosis in mice

The tumor suppressor p53 has been implicated in the pathogenesis of non-cancer-related conditions such as insulin resistance, cardiac failure, and early aging. In addition, accumulation of p53 has been observed in the hepatocytes of individuals with fibrotic liver diseases, but the significance of this is not known. Herein, we have mechanistically linked p53 activation in hepatocytes to liver fibrosis. Hepatocyte-specific deletion in mice of the gene encoding Mdm2, a protein that promotes p53 degradation, led to hepatocyte synthesis of connective tissue growth factor (CTGF; the hepatic fibrogenic master switch), increased hepatocyte apoptosis, and spontaneous liver fibrosis; concurrent removal of p53 completely abolished this phenotype. Compared with wild-type controls, mice with hepatocyte-specific p53 deletion exhibited similar levels of hepatocyte apoptosis but decreased liver fibrosis and hepatic CTGF expression in two models of liver fibrosis. The clinical significance of these data was highlighted by two observations. First, p53 upregulated CTGF in a human hepatocellular carcinoma cell line by repressing miR-17-92. Second, human liver samples showed a correlation between CTGF and p53-regulated gene expression, which were both increased in fibrotic livers. This study reveals that p53 induces CTGF expression and promotes liver fibrosis, suggesting that the p53/CTGF pathway may be a therapeutic target in the treatment of liver fibrosis.

Glucagon-like peptide-1 reduces hepatic lipogenesis via activation of AMP-activated protein kinase

BACKGROUND & AIMS

Glucagon-like peptide-1 (GLP-1), a gut-derived peptide degraded by dipeptidyl peptidase-4 (DPP4), stimulates insulin secretion in response to nutrients, yet its direct effect on the liver is controversial. We investigated the effects of GLP-1 on hepatic fat and glucose metabolism and elucidated its mechanism of action.

METHODS

Hepatic fat metabolism, including lipogenic enzymes and signal transduction regulators, was assessed in livers of DPP4-deficient rats (DPP4-) with chronically elevated GLP-1 and in GLP-1-treated primary hepatocytes. The effect of chronic elevated GLP-1 on insulin sensitivity was measured using the hyperinsulinemic-euglycemic clamp.

RESULTS

Normal and high fat diet fed DPP4-rats displayed reduced hepatic triglycerides, accompanied by down-regulation of lipogenesis enzymes and parallel up-regulation of carnitine palmitoyltransferase-1, a key enzyme in fatty acid β-oxidation. In vitro studies demonstrated that these effects were directly induced by GLP-1. Mechanistically, GLP-1 increased cAMP in hepatocytes, resulting in the phosphorylation of cAMP-activated protein kinase (AMPK), a suppressor of lipogenesis. Indeed, hepatocytes expressing a dominant negative Ad-DN-AMPK displayed attenuated GLP-1 effects on AMPK phosphorylation and its downstream lipogenic targets. Importantly, normoglycemic DPP4-rats did not display improved hepatic insulin sensitivity in vivo, suggesting a direct effect of GLP-1 on fat metabolism. Finally, DPP4-rats expressed lower levels of hepatic proinflammatory and profibrotic cytokines in response to nutrient stimuli.

CONCLUSIONS

GLP-1 suppresses hepatic lipogenesis via activation of the AMPK pathway. GLP-1 inhibitory effects on hepatic fat accumulation and nutrient-induced hepatic proinflammatory response suggest GLP-1 analogs as novel therapies for non-alcoholic fatty liver diseases.

Mechanisms of hepatic fibrogenesis

Multiple etiologies of liver disease lead to liver fibrosis through integrated signaling networks that regulate the deposition of extracellular matrix. This cascade of responses drives the activation of hepatic stellate cells (HSCs) into a myofibroblast-like phenotype that is contractile, proliferative and fibrogenic. Collagen and other extracellular matrix (ECM) components are deposited as the liver generates a wound-healing response to encapsulate injury. Sustained fibrogenesis leads to cirrhosis, characterized by a distortion of the liver parenchyma and vascular architecture. Uncovering the intricate mechanisms that underlie liver fibrogenesis forms the basis for efforts to develop targeted therapies to reverse the fibrotic response and improve the outcomes of patients with chronic liver disease.

Mechanisms of hepatic fibrogenesis

Multiple etiologies of liver disease lead to liver fibrosis through integrated signaling networks that regulate the deposition of extracellular matrix. This cascade of responses drives the activation of hepatic stellate cells (HSCs) into a myofibroblast-like phenotype that is contractile, proliferative and fibrogenic. Collagen and other extracellular matrix (ECM) components are deposited as the liver generates a wound-healing response to encapsulate injury. Sustained fibrogenesis leads to cirrhosis, characterized by a distortion of the liver parenchyma and vascular architecture. Uncovering the intricate mechanisms that underlie liver fibrogenesis forms the basis for efforts to develop targeted therapies to reverse the fibrotic response and improve the outcomes of patients with chronic liver disease.

Mechanisms of hepatic fibrogenesis

Multiple etiologies of liver disease lead to liver fibrosis through integrated signaling networks that regulate the deposition of extracellular matrix. This cascade of responses drives the activation of hepatic stellate cells (HSCs) into a myofibroblast-like phenotype that is contractile, proliferative and fibrogenic. Collagen and other extracellular matrix (ECM) components are deposited as the liver generates a wound-healing response to encapsulate injury. Sustained fibrogenesis leads to cirrhosis, characterized by a distortion of the liver parenchyma and vascular architecture. Uncovering the intricate mechanisms that underlie liver fibrogenesis forms the basis for efforts to develop targeted therapies to reverse the fibrotic response and improve the outcomes of patients with chronic liver disease.

Hepatitis C and hepatic steatosis

Hepatic steatosis is commonly seen in patients with chronic hepatitis C infection, and the two together have a greater association than by chance alone. Hepatitis C virus is closely associated with lipid metabolism throughout its lifecycle. Hepatic steatosis is more common in genotype 3 infection, due to direct viral effects including through microsomal triglyceride transfer protein, peroxisome proliferator activating receptor, and sterol regulatory element binding protein. In non-genotype 3 infection, hepatic steatosis is considered largely to be due to alterations in host metabolism, particularly through insulin resistance. The clinical relevance of this association has yet to be fully explored. Hepatic steatosis is associated with increased hepatic fibrosis and a reduced level of sustained virological response to pegylated interferon and ribavirin. Small studies trialing adjuvant anti-diabetic therapies or HMG-CoA reductase inhibitors with pegylated-interferon and ribavirin have shown an improved sustained virological response and reduced viral titer. Furthermore, simple lifestyle alterations showed positive effects on parameters of disease activity. These insights raise the possibility of novel treatment options.

Connective tissue growth factor hammerhead ribozyme attenuates human hepatic stellate cell function

AIM: To determine the effect of hammerhead ribozyme targeting connective tissue growth factor (CCN2) on human hepatic stellate cell (HSC) function.

METHODS: CCN2 hammerhead ribozyme cDNA plus two self-cleaving sequences were inserted into pTriEx2 to produce pTriCCN2-Rz. Each vector was individually transfected into cultured LX-2 human HSCs, which were then stimulated by addition of transforming growth factor (TGF)-β1 to the culture medium. Semi-quantitative RT-PCR was used to determine mRNA levels for CCN2 or collagen I, while protein levels of each molecule in cell lysates and conditioned medium were measured by ELISA. Cell-cycle progression of the transfected cells was assessed by flow cytometry.

RESULTS: In pTriEx2-transfected LX-2 cells, TGF-β1 treatment caused an increase in the mRNA level for CCN2 or collagen I, and an increase in produced and secreted CCN2 or extracellular collagen I protein levels. pTriCCN2-Rz-transfected LX-2 cells showed decreased basal CCN2 or collagen mRNA levels, as well as produced and secreted CCN2 or collagen I protein. Furthermore, the TGF-β1-induced increase in mRNA or protein for CCN2 or collagen I was inhibited partially in pTriCCN2-Rz-transfected LX-2 cells. Inhibition of CCN2 using hammerhead ribozyme cDNA resulted in fewer of the cells transitioning into S phase.

CONCLUSION: Endogenous CCN2 is a mediator of basal or TGF-β1-induced collagen I production in human HSCs and regulates entry of the cells into S phase.

Hepatitis C virus and type 2 diabetes

This review focuses on the relationship between hepatitis C virus (HCV) infection and glucose metabolism derangements. Cross-sectional and longitudinal studies have shown that the chronic HCV infection is associated with an increased risk of developing insulin resistance (IR) and type 2 diabetes (T2D). The direct effect of HCV on the insulin signaling has been analyzed in experimental models. Although currently available data should be considered as preliminary, HCV seems to affect glucose metabolism via mechanisms that involve cellular pathways that have been implicated in the host innate immune response. IR and T2D not only accelerate the histological and clinical progression of chronic hepatitis C, but also reduce the early and sustained virological response to interferon-alpha-based therapy. Thus, a detailed knowledge of the mechanisms underlying the HCV-associated glucose metabolism derangements is warranted, in order to improve the clinical management of chronic hepatitis C patients.

[Bushen Rougan Recipe in prevention of hepatic fibrosis in rats induced by dimethylnitrosamine: a study on its preliminary mechanism]

OBJECTIVE

To study the effects of Bushen Rougan Recipe (BSRGR), a compound traditional Chinese herbal medicine, on hepatic fibrosis in rats induced by dimethylnitrosamine (DMN), and to explore its preliminary mechanism.

METHODS

A total of 40 male Wistar rats were randomly divided into normal control group (n=10), untreated group (n=15), and BSRGR group (n=15). Except for the rats in normal control group, hepatic fibrosis in rats was induced by peritoneal injection of DMN for 4 weeks. And the rats in the BSRGR group were also intragastrically administered BSRGR within the 4-week course. At the end of the 4-week course, rats were all sacrificed. The liver functions were determined by automatic biochemistry analyzer, including serum total bilirubin (Tbil), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and albumin. Expressions of connective tissue growth factor (CTGF) and collagen type I mRNA in liver tissue were detected by reverse transcription polymerase chain reaction.

RESULTS

It was found that the serum Tbil level and the activities of AST, ALT were declined in the BSRGR group as compared with those in the untreated group (P<0.01). The serum albumin content in the BSRGR group was increased as compared with that in the untreated group (P<0.01). The expressions of collagen type I and CTGF mRNAs in the untreated group were higher than those in the BSRGR group (P<0.01).

CONCLUSION

BSRGR can decrease the expressions of collagen type I and CTGF mRNAs in the rats with hepatic fibrosis, which may be one of possible mechanisms in treating hepatic fibrosis.

Connective tissue growth factor: a fibrogenic master switch in fibrotic liver diseases

Connective tissue growth factor (CTGF=CCN2), one of six members of cysteine-rich, secreted, heparin-binding proteins with a modular structure, is recognized as an important player in fibrogenic pathways as deduced from findings in non-hepatic tissues and emerging results from liver fibrosis. Collectively, the data show strongly increased expression in fibrosing tissues and transforming growth factor (TGF-beta)-stimulated expression in hepatocytes, biliary epithelial cells and stellate cells. Functional activity as a mediator of fibre-fibre, fibre-matrix and matrix-matrix interactions, as an enhancer of profibrogenic TGF-beta and several secondary effects owing to TGF-beta enhancement, and as a down-modulator of the bioactivity of bone morphogenetic protein-7 has been proposed. By changing the activity ratio of TGF-beta to its antagonist bone-morphogenetic protein-7, CTGF is proposed as a fibrogenic master switch for epithelial-mesenchymal transition. Consequently, knockdown of CTGF considerably attenuates experimental liver fibrosis. The spill-over of CTGF from the liver into the blood stream proposes this protein as a non-invasive reporter of TGF-beta bioactivity in this organ. Indeed, CTGF-levels in sera correlate significantly with fibrogenic activity. The data suggest CTGF as a multifaceted regulatory protein in fibrosis, which offers important translational aspects for diagnosis and follow-up of hepatic fibrogenesis and as a target for therapeutic interventions. In addition, CTGF-promoter polymorphism might be of importance as a prognostic genetic marker to predict the progression of fibrosis.