Review article: hepatitis C virus-associated steatosis--pathogenic mechanisms and clinical implications

Estimating Global Prevalence of Metabolic Dysfunction-Associated Fatty Liver Disease in Overweight or Obese Adults

BACKGROUND & AIMS

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a new terminology updated from non-alcoholic fatty liver disease (NAFLD). In this study, we aim to estimate the global prevalence of MAFLD specifically in overweight and obese adults from the general population by performing a systematic review and meta-analysis through mining the existing epidemiological data on fatty liver disease.

METHODS

We searched Medline, Embase, Web of Science, Cochrane and google scholar database from inception to November, 2020. DerSimonian-Laird random-effects model with Logit transformation was performed for data analysis. Sensitivity analysis and meta-regression were used to explore predictors of MAFLD prevalence in pooled statistics with high heterogeneity.

RESULTS

We identified 116 relevant studies comprised of 2,667,052 participants in general population with an estimated global MAFLD prevalence as 50.7% (95% CI 46.9-54.4) among overweight/obese adults regardless of diagnostic techniques. Ultrasound was the most commonly used diagnostic technique generating prevalence rate of 51.3% (95% CI, 49.1-53.4). Male (59.0%; 95% CI, 52.0-65.6) had a significantly higher MAFLD prevalence than female (47.5%; 95% CI, 40.7-54.5). Interestingly, MAFLD prevalence rates are comparable based on classical NAFLD and non-NAFLD studies in general population. The pooled estimate prevalence of comorbidities such as type 2 diabetes and metabolic syndrome was 19.7% (95% CI, 12.8-29.0) and 57.5% (95% CI, 49.9-64.8), respectively.

CONCLUSIONS

MAFLD has an astonishingly high prevalence rate in overweight and obese adults. This calls for attention and dedicated action from primary care physicians, specialists, health policy makers and the general public alike.

Genetic variant of RXR involved in the vitamin D metabolic pathway was linked to HCV infection outcomes among a high-risk Chinese population

Genetic variation of related genes in Vitamin D (VD) metabolic pathway played an important role in antiviral immune response and chronic hepatitis C virus (HCV) infection. Retinoid X receptor (RXR) is one of the key genes in the metabolism pathway of VD. This study aims to investigate the effect of single nucleotide polymorphisms (SNPs) in RXR on the outcomes of HCV infection. Three SNPs (RXRɑ-rs4842194, rs1045570 and RXRβ-rs2076310) were genotyped using Sequenom MassARRAY platform in 515 spontaneous clearance subjects, 830 persistent infection subjects, and 1062 uninfected subjects. Multivariate stepwise regression analyss was used to identify the prediction factors for HCV infection outcomes. The USCS Brower and RNAfold web serves were performed to further explore the potential biological functions of positive SNPs. The results of logistic regression analysis after adjusting for age, gender and types of high-risk population showed that subjects with RXRβ rs2076310-T (recessive model: adjusted OR = 1.598, 95%CI = 1.126-2.267, P = 0.009; additive model: adjusted OR = 1.196, 95%CI = 1.011-1.416, P = 0.037) had a significantly increased possibility of HCV infection chronicity. Rs2076310, age, types of high-risk population and aspartate aminotransferase were independent predictors of chronic HCV infection (P < 0.05). And the area under the receiver operating characteristic curve of combined effects of these factors was 0.679. Bioinformatics analysis indicated that rs2076310 could affect the gene expression level by affecting the transcriptional regulatory activity of the corresponding gene region. These findings indicated that genetic variation of RXRβ was associated with the risk of HCV infection chronicity among a high-risk Chinese population.

Increased body fat percentage in patients with hepatitis B and C virus infection

Accumulated evidence has suggested associations between glucose abnormalities and insulin resistance with hepatitis C virus (HCV) and hepatitis B virus (HBV) infections. However, few studies have reported the effect of hepatitis virus infections on body composition. Our aim was to explore the association of hepatitis virus infections with percent body fat (PBF) in a cross-sectional analysis. A total of 69226 subjects obtained from the health examinations at Tri-Service General Hospital (TSGH) from 2010 to 2016 were enrolled in the study. Participants were divided into subgroups based on the presence of hepatitis B surface antigen (HBsAg) and anti-HCV. PBF was measured by bioelectrical impedance analysis (BIA). A multivariable linear regression model was applied to test the association of hepatitis virus infections with PBF and glycemic status. In male participants, hepatitis virus infections were closely associated with increased PBF, especially in those subjects with HCV/HBV coinfection. HCV/HBV coinfection was positively correlated with fasting plasma glucose and postprandial glucose while HCV and HBV mono-infection were not. The impact of hepatitis virus infection on increased PBF was observed in general population with gender difference. A further study on the treatment of hepatitis virus infection might help prevent the development of obesity-related diseases.

Investigating Molecular Connections of Non-alcoholic Fatty Liver Disease with Associated Pathological Conditions in West Virginia for Biomarker Analysis

Non-alcoholic fatty liver disease (NAFLD) is a disease characterized by a steatosis of the liver that may progress to more serious pathological conditions including: nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. As the prevalence of NAFLD has increased worldwide in recent years, pathophysiology and risk factors associated with disease progression of NAFLD are at the focus of many studies. NAFLD is related to and shares common serum biomarkers with cardiovascular disease (CVD), type 2 diabetes mellitus (T2DM), obesity, and metabolic syndrome (MetS). West Virginia (WV) is a state with some of the highest rates of CVD, obesity and diabetes mellitus. As NAFLD is closely related to these diseases, it is of particular interest in WV. Currently there is no cost-effective, standardized method used clinically to detect NAFLD prior to the onset of reversible complications. At this time, the diagnosis of NAFLD is made with costly radiologic studies and invasive biopsy. These studies are only diagnostic once changes to hepatic tissue have occurred. The diagnosis of NAFLD by traditional methods may not allow for successful intervention and may not be readily available in areas with already sparse medical resources. In this literature review, we identify a list of biomarkers common among CVD, T2DM, obesity, MetS and NAFLD. From this research we propose the following biomarkers are good candidates for inclusion in a panel of biomarkers for the early detection of NAFLD: adiponectin, AST, ALT, apo-B, CK18, CPS1, CRP, FABP-1, ferritin, GGT, GRP78, HDL-C, IGF-1, IL-1β, 6, 8, 10, IRS-2PAI-1, leptin, lumican, MDA SREBP-1c and TNF-α. Creating and implementing a biomarker panel for the early detection and attenuation of NAFLD, prior to the onset of irreversible complication would provide maximum benefit and decrease the disease burden on the patients and healthcare system of WV.

Adipokines, insulin resistance, hepatic steatosis, and necroinflammation in patients with chronic viral hepatitis

Background: Hypoadiponectinemia and hyperleptinemia, and reductions in the ratio of adiponectin to leptin (A/L ratio) are associated with the development of hepatic necroinflammation in nonalcoholic fatty liver, but the association of the adipokines with hepatic steatosis in chronic viral hepatitis is unclear.

Objective: To investigate the relationship between serum A/L ratio, insulin resistance, degree of hepatic steatosis, and necroinflammation in patients with chronic viral hepatitis.

Methods: We measured serum adiponectin, leptin, and resistin levels, insulin resistance, and analyzed the association between liver histopathology and the level of the adipokines in 44 patients with chronic viral hepatitis before they started treatment.

Results: We found that insulin resistance, leptin, and resistin levels tended to increase in the group with a greater degree of hepatic steatosis and necroinflammation, but that the increase was not significant. The adiponectin/leptin ratio (A/L ratio) in a group with a low degree of hepatic steatosis was significantly higher than it was in the group with a high degree of hepatic steatosis (3.1 ± 3.1 vs 1.2 ± 0.8; P = 0.008). The A/L ratio in a group with low histological activity index (HAI) scores was significantly higher than in the group with high HAI scores (3.7 ± 3.4 vs 1.1 ± 1.1; P = 0.006). Abdominal obesity was the only variable that showed a significant association with the HAI score (P = 0.03).

Conclusion: The serum A/L ratio in patients with chronic viral hepatitis showed a significant inverse association with their degree of hepatic steatosis and necroinflammation.

Hepatitis C virus suppresses Hepatocyte Nuclear Factor 4 alpha, a key regulator of hepatocellular carcinoma

Hepatitis C Virus (HCV) infection presents with a disturbed lipid profile and can evolve to hepatic steatosis and hepatocellular carcinoma (HCC). Hepatocyte Nuclear Factor 4 alpha (HNF4α) is the most abundant transcription factor in the liver, a key regulator of hepatic lipid metabolism and a critical determinant of Epithelial to Mesenchymal Transition and hepatic development. We have previously shown that transient inhibition of HNF4α initiates transformation of immortalized hepatocytes through a feedback loop consisting of miR-24, IL6 receptor (IL6R), STAT3, miR-124 and miR-629, suggesting a central role of HNF4α in HCC. However, the role of HNF4α in Hepatitis C Virus (HCV)-related hepatocarcinoma has not been evaluated and remains controversial. In this study, we provide strong evidence suggesting that HCV downregulates HNF4α expression at both transcriptional and translational levels. The observed decrease of HNF4α expression correlated with the downregulation of its downstream targets, HNF1α and MTP. Ectopic overexpression of HCV proteins also exhibited an inhibitory effect on HNF4α levels. The inhibition of HNF4α expression by HCV appeared to be mediated at transcriptional level as HCV proteins suppressed HNF4α gene promoter activity. HCV also up-regulated IL6R, activated STAT3 protein phosphorylation and altered the expression of acute phase genes. Furthermore, as HCV triggered the loss of HNF4α a consequent change of miR-24, miR-629 or miR-124 was observed. Our findings demonstrated that HCV-related HCC could be mediated through HNF4α-microRNA deregulation implying a possible role of HNF4α in HCV hepatocarcinogenesis. HCV inhibition of HNF4α could be sustained to promote HCC.

The Impact of PNPLA3 rs738409 SNP on Liver Fibrosis Progression, Portal Hypertension and Hepatic Steatosis in HIV/HCV Coinfection

BACKGROUND

Faster fibrosis progression and hepatic steatosis are hallmarks of HIV/HCV coinfection. A single nucleotide polymorphism (SNP) of the PNPLA3-gene is associated with development of non-alcoholic steatohepatitis and a worse outcome in alcoholic liver disease. However, the role of PNPLA3 rs738409 SNP on liver fibrosis and steatosis, portal hypertension, and virological response in HIV/HCV coinfection remains unclear.

METHODS

In this cross-sectional study PNPLA3 (rs738409) and IL28B (rs12979860) SNPs were determined in 177 HIV/HCV coinfected patients. Liver fibrosis and steatosis-staged by liver biopsy and transient elastography using the Controlled Attenuation Parameter (CAP)-and portal hypertension (hepatic venous pressure gradient, HVPG) were compared across PNPLA3 genotypes.

RESULTS

75 (42.4%) patients tested positive for a PNPLA3 minor/major risk allele (G/C:66; G/G:9) showed comparable fibrosis stages (median F2 vs. F2; p = 0.292) and similar amounts of hepatic steatosis (CAP: 203.5 ± 41.9 vs. 215.5 ± 59.7 dB/m; p = 0.563) as compared to patients without a PNPLA3 risk allele. Advanced liver fibrosis was neither associated with PNPLA3 (p = 0.253) nor IL28B-genotype (p = 0.628), but with HCV-GT3 (p = 0.003), higher BMI (p = 0.008) and higher age (p = 0.007). Fibrosis progression rate (0.27 ± 0.41 vs. 0.20 ± 0.26 units/year; p = 0.984) and HVPG (3.9 ± 2.6 vs. 4.4 ± 3.0 mmHg; p = 0.472) were similar in patients with and without PNPLA3 risk alleles. SVR rates to PEGIFN/RBV therapy were similar across PNPLA3 genotypes.

CONCLUSIONS

The presence of a PNPLA3 risk allele had no independent impact on liver disease or virological response rates to PEGIFN/RBV therapy in our cohort of HIV/HCV coinfected patients.

Hepatitis C as a risk factor for carotid atherosclerosis - a systematic review

BACKGROUND

Observational studies on the association of chronic hepatitis C with carotid atherosclerosis have yielded varying results. In addition, previous related systematic reviews were limited in synthesis. By more careful selection and further synthesis, we summarize current body of evidence on the relationship between chronic hepatitis C and carotid atherosclerosis.

METHODS

All published observational studies related to the topic identified by systematic searches of PubMed and Scopus were screened based on diagnosis of chronic hepatitis C and diagnosis and estimation of the risk of a carotid atherosclerosis-related outcome. Selected studies were subjected to quality assessment, and eligible studies were used in subsequent narrative and quantitative syntheses.

RESULTS

The initial search identified 190 unique publications, which were narrowed by preliminary review to 16 potentially relevant original articles. After quality assessment, seven studies were eligible and were used in narrative synthesis. Five studies assessed the risk of increased carotid intimal media thickening using B mode ultrasonography; five studies assessed the risk of carotid plaque formation using B mode ultrasonography. Five of these studies were used in subsequent meta-analysis. The risk of a person with chronic hepatitis C developing carotid intimal media thickening is about 4·03 times the risk of an uninfected person. The risk of a person with chronic hepatitis C developing carotid plaque is about 3·94 times the risk of an uninfected person.

CONCLUSION

Current evidence shows that hepatitis C virus (HCV) or factors associated with HCV infection can promote the occurrence and progression of carotid atherosclerosis.

A complex signaling network involving protein kinase CK2 is required for hepatitis C virus core protein-mediated modulation of the iron-regulatory hepcidin gene expression

Hepatitis C virus (HCV) infection is associated with hepatic iron overload and elevated serum iron that correlate to poor antiviral responses. Hepcidin (HAMP), a 25-aa cysteine-rich liver-specific peptide, controls iron homeostasis. Its expression is up-regulated in inflammation and iron excess. HCV-mediated hepcidin regulation remains controversial. Chronic HCV patients possess relatively low hepcidin levels; however, elevated HAMP mRNA has been reported in HCV core transgenic mice and HCV replicon-expressing cells. We investigated the effect of HCV core protein on HAMP gene expression and delineated the complex interplay of molecular mechanisms involved. HCV core protein up-regulated HAMP promoter activity, mRNA, and secreted protein levels. Enhanced promoter activity was abolished by co-transfections of core with HAMP promoter constructs containing mutated/deleted BMP and STAT binding sites. Dominant negative constructs, pharmacological inhibitors, and silencing experiments against STAT3 and SMAD4 confirmed the participation of both pathways in HAMP gene regulation by core protein. STAT3 and SMAD4 expression levels were found increased in the presence of HCV core, which orchestrated SMAD4 translocation into the nucleus and STAT3 phosphorylation. To further understand the mechanisms governing the core effect, the role of the JAK/STAT-activating kinase CK2 was investigated. A CK2-dominant negative construct, a CK2-specific inhibitor, and RNAi interference abrogated the core-induced increase on HAMP promoter activity, mRNA, and protein levels, while CK2 acted in synergy with core to significantly enhance HAMP gene expression. Therefore, HCV core up-regulates HAMP gene transcription via a complex signaling network that requires both SMAD/BMP and STAT3 pathways and CK2 involvement.

HCV NS5A co-operates with PKR in modulating HCV IRES-dependent translation

Translation initiation of the Hepatitis C virus (HCV) genome is driven by an internal ribosome entry site (IRES), located within the 5' non-coding region. Several studies have suggested that different cellular non canonical proteins or viral proteins can regulate the HCV IRES activity. However, the role of the viral proteins on HCV translation remains controversial. In this report, we confirmed previous studies showing that NS5A down-regulates IRES activity in HepG2 but not in Huh7 cells suggesting that the NS5A effect on HCV IRES is cell-type dependent. Additionally, we provide strong evidence that activated PKR up-regulates the IRES activity while silencing of endogenous PKR had the opposite effect. Furthermore, we present data indicating that the NS5A-mediated inhibitory effect on IRES-dependent translation could be linked with the PKR inactivation. Finally, we show that NS5A from GBV-C but not from GBV-B down-regulates HCV IRES activity in the absence or the presence of PKR over expression. Notably, HCV and GBV-C but not GBV-B NS5A contains a previously identified PKR interacting protein domain.

Hepcidin and the iron enigma in HCV infection

An estimated 30-40% of patients with chronic hepatitis C have elevated serum iron, transferrin saturation, and ferritin levels. Clinical data suggest that iron is a co-morbidity factor for disease progression following HCV infection. Iron is essential for a number of fundamental metabolic processes in cells and organisms. Mammalian iron homeostasis is tightly regulated and this is maintained through the coordinated action of sensory and regulatory networks that modulate the expression of iron-related proteins at the transcriptional and/or posttranscriptional levels. Disturbances of iron homeostasis have been implicated in infectious disease pathogenesis. Viruses, similarly to other pathogens, can escape recognition by the immune system, but they need iron from their host to grow and spread. Hepcidin is a 25-aa peptide, present in human serum and urine and represents the key peptide hormone, which modulates iron homeostasis in the body. It is synthesized predominantly by hepatocytes and its mature form is released in circulation. In this review, we discuss recent advances in the exciting crosstalk of molecular mechanisms and cell signaling pathways by which iron and hepcidin production influences HCV-induced liver disease.

Hepatitis C virus modulates lipid regulatory factor Angiopoietin-like 3 gene expression by repressing HNF-1α activity

BACKGROUND & AIMS

HCV relies on host lipid metabolism to complete its life cycle and HCV core is crucial to this interaction. Liver secreted ANGPTL-3 is an LXR- and HNF-1α-regulated protein, which plays a key role in lipid metabolism by increasing plasma lipids via inhibition of lipase enzymes. Here we aimed to investigate the modulation of ANGPTL-3 by HCV core and identify the molecular mechanisms involved.

METHODS

qRT-PCR and ELISA were used to assess ANGPTL-3 mRNA and protein levels in HCV patients, the JFH-1 infectious system and liver cell lines. Transfections, chromatin immunoprecipitation and immunofluorescence delineated parts of the molecular mechanisms implicated in the core-mediated regulation of ANGPTL-3 gene expression.

RESULTS

ANGPTL-3 gene expression was decreased in HCV-infected patients and the JFH-1 infectious system. mRNA and promoter activity levels were down-regulated by core. The response was lost when an HNF-1α element in ANGPTL-3 promoter was mutated, while loss of HNF-1α DNA binding to this site was recorded in the presence of HCV core. HNF-1α mRNA and protein levels were not altered by core. However, trafficking between nucleus and cytoplasm was observed and then blocked by an inhibitor of the HNF-1α-specific kinase Mirk/Dyrk1B. Transactivation of LXR/RXR signalling could not restore core-mediated down-regulation of ANGPTL-3 promoter activity.

CONCLUSIONS

ANGPTL-3 is negatively regulated by HCV in vivo and in vitro. HCV core represses ANGPTL-3 expression through loss of HNF-1α binding activity and blockage of LXR/RXR transactivation. The putative ensuing increase in serum lipid clearance and uptake by the liver may sustain HCV virus replication and persistence.

Clinico-pathological significance of hepatitis C virus core antigen levels in chronic infection

Hepatitis C virus core antigen (HCVcoreAg) may be measured in serum with a sensitive, recently validated assay. Beyond its value as a marker of viral infection, there are little data on its relation with clinical, histological, and virological parameters. In this study, the significance of HCVcoreAg levels was studied in a prospective cohort of 114 patients with chronic hepatitis C. HCVcoreAg was measured by a commercial chemiluminescent microparticle immunoassay. Clinical and virological data included quantitative HCV-RNA, HCV genotype, ALT, GGT, IL28B rs12979860 polymorphism as well as liver histology parameters. HCVcoreAg levels were correlated significantly with HCV-RNA (r=0.56; P<0.0001) but also with ALT levels (r=0.258; P<0.01) and liver necroinflammatory activity (r=0.205; P<0.04). Patients harbouring HCV genotype 3 showed lower levels of HCVcoreAg than both genotype 1 and two patients. In genotype 3, a direct correlation between steatosis and HCVcoreAg was found. Levels of HCVcoreAg also varied according to the IL28B genotype. These data suggest that the evaluation of HCVcoreAg serum levels may provide relevant data for the baseline clinical evaluation of chronic hepatitis C patients. HCVcoreAg serum levels may be a useful tool to further the understanding of chronic hepatitis C pathobiology.

Adiponectin: a key playmaker adipocytokine in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and can progress to cirrhosis, liver failure, and hepatocellular carcinoma. In the last two decades, the prevalence of NAFLD has been growing in most developed countries, mainly as a consequence of its close association with obesity and diabetes mellitus. The exact pathogenesis of NAFLD and especially the mechanisms leading to disease progression have not been completely understood. Adipocytes produce and secrete several bioactive substances known as adipocytokines which are implicated in the pathogenesis of the disease. Among them, adiponectin is an insulin-sensitizing adipocytokine possessing multiple beneficial effects on obesity-related medical complication. This review focuses on the role of adiponectin in NAFLD pathogenesis and its potential use as a diagnostic tool but also as therapeutic target for NAFLD management.

Serum FGF21 and RBP4 levels in patients with chronic hepatitis C

INTRODUCTION

Fibroblast growth factor-21 (FGF21) regulates glucose, lipid, and energy homeostasis. Retinol-binding protein-4 (RBP4) controls metabolic and proliferative cell functions.

AIMS AND METHODS

Aims of the study were to assess (1) serum FGF21 and RBP4 levels in 75 non-obese chronic hepatitis C (CHC) patients and 41 healthy controls similar in age and BMI; (2) the relationship between their serum concentration and insulin resistance, liver histology, and biochemical parameters; (3) their effectiveness as diagnostic markers.

RESULTS

FGF21 levels increased significantly in CHC patients compared with controls (p = 0.04). CHC patients with steatosis had significantly higher FGF21 levels compared with those without steatosis (p = 0.01). FGF21 concentration was positively related to steatosis grade (r = 0.39, p = 0.007). RBP4 levels did not differ between CHC patients and controls, but were negatively associated with necro-inflammatory activity grade (r = (-0.34), p = 0.04), with significantly higher levels in patients with minimal inflammatory activity (G1 vs. G2/3, p < 0.001; G1 vs. G2, p = 0 < 001; G1 vs. G3, p = 0.01). After stepwise linear regression analysis adjusting for potential confounders, RBP4 levels retained their independent significance as a predictor of necro-inflammatory activity (β = -0.31; t = -2.15, p = 0.035) and FGF21 levels as a predictor of steatosis (β = 0.34; t = 2.31, p = 0.024). Serum FGF21 correlated with serum RBP4 levels (r = 0.32, p = 0.02).

CONCLUSIONS

Serum FGF21 levels increased in CHC patients, especially in those with steatosis and were associated with steatosis grade. FGF21 seems to be a useful diagnostic marker in determining hepatic steatosis in CHC. A negative association between serum RBP4 and necro-inflammatory activity indicates that disease severity may determine RBP4 levels.

The impact of host metabolic factors on treatment outcome in chronic hepatitis C

Background. Recent data suggest that chronic hepatitis C has to be considered a metabolic disease further to a viral infection. The aim of this study was to elaborate on the complex interactions between hepatitis C virus, host metabolic factors, and treatment response. Methods. Demographic, virological, and histological data from 356 consecutive patients were analyzed retrospectively. Hepatic steatosis, obesity, and insulin resistance were examined in relation to their impact on treatment outcome. Comparison between genotype 1 and 3 patients was performed to identify differences in the determinants of hepatic steatosis. Results. Histological evidence of hepatic steatosis was found in 113 patients, distributed in 20.3%, 9.0%, and 2.5% for grades I, II, and III, respectively. Hepatic steatosis was associated with past alcohol abuse (P = 0.003) and histological evidence of advanced fibrosis (P < 0.001). Older age (OR 2.51, P = 0.002), genotype (OR 3.28, P < 0.001), cirrhosis (OR 4.23, P = 0.005), and hepatic steatosis (OR 2.48, P = 0.001) were independent predictors for nonresponse. Correlations of hepatic steatosis with alcohol, insulin resistance, and fibrosis stage were found similar for both genotypes 1 and 3. Conclusions. Host metabolic factors may predict treatment outcome, and this impact remains significant even in genotype 3, where steatosis has been believed to be exclusively virus related.

Hepatitis C virus activates the mTOR/S6K1 signaling pathway in inhibiting IRS-1 function for insulin resistance

Hepatitis C virus (HCV) infection significantly increases the prevalence of type 2 diabetes mellitus (T2DM). Insulin receptor substrate 1 (IRS-1) plays a key role in insulin signaling, thus enabling metabolic regulation in mammalian cells. We have previously shown that HCV infection modulates phosphorylation of Akt, a downstream target of IRS-1. In this study, we further examined the status of total IRS-1 and the downstream regulation of the Akt pathway in understanding mTOR/S6K1 signaling using HCV genotype 2a (clone JFH1)-infected hepatocytes. Inhibition of IRS-1 expression was observed in HCV-infected hepatocytes compared to that in a mock-infected control. The status of the tuberous sclerosis complex (TSC-1/TSC-2) was significantly decreased after HCV infection of human hepatocytes, showing a modulation of the downstream Akt pathway. Subsequent study indicated an increased level of Rheb and mTOR expression in HCV-infected hepatocytes. Interestingly, the phosphoS6K1 level was higher in HCV-infected hepatocytes, suggesting a novel mechanism for IRS-1 inhibition. Ectopic expression of TSC-1/TSC-2 significantly recovered the IRS-1 protein expression level in HCV-infected hepatocytes. Further analyses indicated that HCV core protein plays a significant role in modulating the mTOR/S6K1 signaling pathway. Proteasome inhibitor MG 132 recovered IRS-1 and TSC1/2 expression, suggesting that degradation occurred via the ubiquitin proteasome pathway. A functional consequence of IRS-1 inhibition was reflected in a decrease in GLUT4 protein expression and upregulation of the gluconeogenic enzyme PCK2 in HCV-infected hepatocytes. Together, these observations suggested that HCV infection activates the mTOR/S6K1 pathway in inhibiting IRS-1 function and perturbs glucose metabolism via downregulation of GLUT4 and upregulation of PCK2 for insulin resistance.

'Easy to treat' genotypes were not created equal: can rapid virological response (RVR) level the playing field?

Genotypes 2 and 3 (G2/G3) of hepatitis C virus have been lumped together as 'easy to treat'. As a result, guidelines recommend 24 weeks of peginterferon/ribavirin for both. However, a closer look at trials shows that these genotypes are not the same, with G2 infection proving more responsive to peginterferon. The data supporting this conclusion are presented along with possible explanations for the differences observed. Ultimately, decisions must be made about therapy. Rapid virological response (RVR) may be the best parameter predicting successful antiviral therapy. For patients with G2 infection who achieve an RVR, shortened courses of therapy are effective. In contrast, for G3 patients without an RVR, there may be benefit to extending therapy to 48 weeks; however, this requires confirmation in prospective studies. Using RVR to guide therapy may level the playing field between these 'easy to treat' genotypes.

Safety and efficacy of peginterferon alpha plus ribavirin in patients with chronic hepatitis C and coexisting heart disease

BACKGROUND

Chronic hepatitis C patients with coexisting heart disease are often denied antiviral treatment due to safety concerns. However, this is not evidence-based.

AIMS

To evaluate safety and efficacy of pegylated interferon and ribavirin in chronic hepatitis C patients with heart disease.

METHODS

Patients with overt heart disease (ischaemic heart disease, prior mechanical heart valve replacement, chronic arrhythmias and cardiomyopathy) and chronic hepatitis C were treated with standard pegylated interferon/ribavirin doses for standard duration. Cardiovascular safety was monitored by electrocardiography, echocardiography and measurement of troponin and B-type natriuretic peptide.

RESULTS

Twenty-three patients (65.2% male, median age 57 years, 47.8% genotype 1) were treated. Three patients (13%) suspended treatment prematurely; 52% obtained sustained virological response, 39% relapsed, 9% were non-responders. No serious adverse event was observed. Post-treatment clinical examination, electrocardiography and echocardiography did not show any sign of progression of the pre-existing heart disease.

CONCLUSIONS

Treatment with pegylated interferon/ribavirin may be safely offered to carefully selected chronic hepatitis C patients with coexisting, clinically significant heart disease. In these patients, the outcome of antiviral treatment overlaps that observed in other patient subgroups.

HCV infection and the incidence of CKD

BACKGROUND

The risk of hepatitis C virus (HCV) infection upon incident chronic kidney disease (CKD) in the presence of traditional risk factors and renal-modifying therapy is not well known.

STUDY DESIGN

National cohort study.

SETTING & PARTICIPANTS

HCV-infected and -uninfected veterans in ERCHIVES (Electronically Retrieved Cohort of HCV Infected Veterans) in 2001-2006.

PREDICTOR

HCV infection.

OUTCOMES

Incident CKD stages 3-5.

RESULTS

We identified 18,002 patients with HCV infection and 25,137 controls with estimated glomerular filtration rate >60 mL/min/1.73 m(2) at baseline. HCV-infected patients had a lower prevalence of several CKD risk factors, including diabetes (22.9% vs 26.6%), hypertension (52.4% vs 60.8%), and dyslipidemia (39.3% vs 73.9%; P < 0.001). HCV infection was associated with a higher risk of developing CKD stages 3-5 (HR, 1.30; 95% CI, 1.23-1.37). Increasing age, hypertension, and diabetes were associated with significantly higher risks of developing CKD in HCV-infected patients and controls. Decompensated liver disease was a strong predictor of CKD in HCV-infected patients (HR, 3.37; 95% CI, 3.10-3.66) and HCV-uninfected controls (HR, 2.04; 95% CI, 1.84-2.25). In Kaplan-Meier analysis, HCV-infected persons had a shorter time to CKD.

LIMITATIONS

Lack of proteinuria data; small number of women.

CONCLUSIONS

HCV infection is associated with higher risk and shorter time to CKD despite having a lower prevalence of many CKD risk factors. HCV-infected persons should have targeted monitoring for the development and progression of CKD.

Chemerin, vaspin and insulin resistance in chronic hepatitis C

Adipocytokine profile seems to play a distinct role in the pathogenesis of chronic hepatitis C (CHC). Chemerin and vaspin are recently described adipocytokines with various suggested functions and potential to modulate inflammatory response and insulin resistance (IR). We assessed chemerin, vaspin and leptin serum concentration and studied their association with IR laboratory and morphological features in patients with hepatitis C. The study included 40 patients with hepatitis C and 20 healthy volunteers, similar in age and body mass index (43.6 +/- 11.6 vs 40.9 +/- 11.8 years and 25.0 +/- 4.1 vs 23.9 +/- 3.3 kg/m(2), respectively). Patients had to have a normal lipid profile, and diabetes was an exclusion criteria. Serum chemerin and leptin levels and IR were significantly higher in patients with hepatitis C when compared to the controls (P = 0.02, P = 0.02 and P = 0.02, respectively), whereas vaspin level was significantly decreased (P = 0.01). Serum chemerin was negatively associated with necro-inflammatory grade (r = (-0.49), P = 0.01). The lowest levels of serum chemerin were found in patients with moderate/severe inflammation (P = 0.03). Serum leptin tended to be up-regulated in patients with minimal inflammatory activity. Serum vaspin was higher, although not significantly, when fibrosis was more advanced. IR was positively associated with fibrosis stage (r = 0.33, P = 0.03). Serum chemerin and leptin were related to each other (r = 0.45, P = 0.02).Our findings support a complex interaction between the analysed adipokines and pathogenesis of inflammatory process in CHC. The role of chemerin and vaspin in pathogenesis of inflammatory response should be further investigated.

Practice guidelines for the diagnosis and management of nonalcoholic fatty liver disease. A decalogue from the Italian Association for the Study of the Liver (AISF) Expert Committee

We report the evidence-based Italian Association for the Study of Liver guidelines for the appropriate diagnosis and management of patients with nonalcoholic fatty liver disease in clinical practice and its related research agenda. The prevalence of nonalcoholic fatty liver disease varies according to age, gender and ethnicity. In the general population, the prevalence of nonalcoholic fatty liver disease is about 25% and the incidence is of two new cases/100 people/year. 2-3% of individuals in the general population will suffer from nonalcoholic steatohepatitis. Uncomplicated steatosis will usually follow a benign course. Individuals with nonalcoholic steatohepatitis, however, have a reduced life expectancy, mainly owing to vascular diseases and liver-related causes. Moreover, steatosis has deleterious effects on the natural history of HCV infection. Nonalcoholic fatty liver disease is usually diagnosed in asymptomatic patients prompted by the occasional discovery of increased liver enzymes and/or of ultrasonographic steatosis. Medical history, complete physical examination, etiologic screening of liver injury, liver biochemistry tests, serum lipids and insulin sensitivity tests should be performed in every patient. Occult alcohol abuse should be ruled out. Ultrasonography is the first-line imaging technique. Liver biopsy, the gold standard in diagnosis and prognosis of nonalcoholic fatty liver disease, is an invasive procedure and its results will not influence treatment in most cases but will provide prognostic information. Assessment of fibrosis by composite scores, specific laboratory parameters and transient elastography might reduce the number of nonalcoholic fatty liver disease patients requiring liver biopsy. Dieting and physical training reinforced by behavioural therapy are associated with improved nonalcoholic fatty liver disease. Diabetes and the metabolic syndrome should be ruled out at timed intervals in nonalcoholic fatty liver disease. Nonalcoholic steatohepatitis patients should undergo periodic evaluation of cardiovascular risk and of advancement of their liver disease; those with nonalcoholic steatohepatitis-cirrhosis should be evaluated for early diagnosis of hepatocellular carcinoma.

Improvement of steatosis after interferon therapy in HCV genotype 4 is related to weight loss

INTRODUCTION

Hepatic steatosis is common in patients with chronic hepatitis C virus (HCV) infection, and its occurrence may be related to both host and viral factors. Relationship between improvement in steatosis and response to anti-viral treatment remains unclear. This study assessed the factors associated with steatosis in patients infected with genotype 4 HCV, and to correlate degree of changes in steatosis with host factors and response to treatment.

METHODS

Records of 175 patients with chronic genotype 4 HCV infection, who had received interferon and ribavirin combination therapy, were reviewed retrospectively to extract data on body mass index (BMI), presence of diabetes mellitus, and liver histology findings. Paired BMI data and liver biopsies (pre- and 24-weeks post-treatment) were available in 86 patients. Baseline steatosis and its changes (before and after treatment) were the dependent variables in a univariate and multivariate analyses.

RESULTS

Steatosis was found in 88/175 (50.3%) of baseline biopsies. Its presence was related to baseline BMI (r=0.33, P<0.01), but not with viral load, or grade of liver inflammation or fibrosis. On follow up, improvement in steatosis was significantly associated with degree of weight loss but not with response to anti-viral treatment.

CONCLUSION

Steatosis is common in genotype 4 HCV infection, and its presence appears to be related to high BMI, but not to viral load or degree of liver injury.

Hepatic steatosis in hepatitis C is a storage disease due to HCV interaction with microsomal triglyceride transfer protein (MTP)

Liver steatosis is a frequent histological feature in patients chronically infected with hepatitis C virus (HCV). The relationship between HCV and hepatic steatosis seems to be the result of both epigenetic and genetic factors. In vivo and in vitro studies have shown that HCV can alter intrahepatic lipid metabolism by affecting lipid synthesis, oxidative stress, lipid peroxidation, insulin resistance and the assembly and secretion of VLDL. Many studies suggest that HCV-related steatosis might be the result of a direct interaction between the virus and MTP. It has been demonstrated that MTP is critical for the secretion of HCV particles and that inhibition of its lipid transfer activity reduces HCV production. However, higher degrees of hepatic steatosis were found in chronic hepatitis C patients carrying the T allele of MTP -493G/T polymorphism that seems to be associated with increased MTP transcription. We propose here that liver steatosis in hepatitis C could be a storage disease induced by the effects of the virus and of its proteins on the intracellular lipid machinery and on MTP. Available data support the hypothesis that HCV may modulate MTP expression and activity through a number of mechanisms such as inhibition of its activity and transcriptional control. Initial up regulation could favour propagation of HCV while down regulation in chronic phase could cause impairment of triglyceride secretion and excessive lipid accumulation, with abnormal lipid droplets facilitating the "storage" of virus particles for persistent infection.

Domain 3 of hepatitis C virus core protein is sufficient for intracellular lipid accumulation

BACKGROUND

Hepatitis C virus (HCV) is a major cause of liver disease worldwide, with steatosis, or "fatty liver," being a frequent histologic finding. In previous work, we identified sequence polymorphisms within domain 3 (d3) of genotype 3 HCV core protein that correlated with steatosis and in vitro lipid accumulation. In this study, we investigated the sufficiency of d3 to promote lipid accumulation, the role of HCV genotype in d3 lipid accumulation, and the subcellular distribution of d3.

METHODS

Stable cell lines expressing green fluorescent protein (GFP) fusions with isolates of HCV genotype 3 core steatosis-associated d3 (d3S), non-steatosis-associated d3 (d3NS), and genotype 1 d3 (d3G1) were analyzed by means of immunofluorescence, oil red O (ORO) staining, and triglyceride quantitation.

RESULTS

Cells that expressed d3S had statistically significantly more ORO than did cells expressing d3NS or d3G1 (P=.02 and <.001, respectively), as well as higher triglyceride levels P =.03 and .003, respectively). Immunofluorescence analysis showed that d3 does not colocalize to lipid droplets but partially colocalizes to the Golgi apparatus.

CONCLUSIONS

Our results suggest that HCV core d3 is sufficient to mediate the accumulation of lipid by means of a mechanism that is independent of domains 1 and 2. Our results also suggest that altered lipid trafficking may be involved.

[Non alcoholic steatosis in HIV infection]

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatosis (NASH) are common conditions in the setting of HIV infection, especially if HCV coinfection or metabolic syndrome's features are present. The factors that contribute to the progression of NAFLD to NASH and fibrosis are not completely known and the role of antiretroviral therapy is especially controversial. Although the natural history of NASH in the setting of HIV infection is unknown, it may emerge as one of the leading causes of liver disease over the long term in these patients. Liver biopsy is still the gold standard for the diagnosis of NASH. Indeed, although non-invasive techniques are promising tools for the diagnosis of NAFLD, they do not assess liver damage. There is no specific therapy for NASH in HIV infection, as the role of glitazones has not been evaluated in these patients.

Hepatic steatosis in patients with chronic hepatitis C virus genotype 2 or 3 does not affect viral response in patients treated with peginterferon alpha-2a (40KD) (PEGASYS) plus ribavirin (COPEGUS) for 16 or 24 weeks

BACKGROUND

Hepatic steatosis is common in patients infected with hepatitis C virus (HCV). The effect of steatosis on anti-HCV therapy efficacy is unclear.

METHODS

We studied host and viral factors associated with steatosis and the effect of steatosis on treatment efficacy using the database of a large prospective trial in patients with HCV genotypes 2 and 3.

RESULTS

Out of 885 patients assessed for steatosis, a total of 614 patients or 69% had steatosis. Patients with genotype 3 were more likely to have steatosis than those with genotype 2 (79 vs. 59%, P<0.001). Using the logistic regression model, steatosis was associated with genotype 3 (P<0.0001), older age (P=0.0025), heavier weight (P<0.0001), higher HCV RNA (P<0.0001), and higher ALT levels (P=0.015). By univariate analysis, steatosis was associated with lower sustained virological response (SVR) in patients with genotype 3, but not in patients with genotype 2. When all factors associated with steatosis and SVR were evaluated by logistic regression analysis; genotype, age, bodyweight, histological diagnosis, ALT quotient, baseline HCV RNA and treatment duration were associated with the probability of SVR, but gender, race and steatosis were not. Further analysis showed that steatosis remained a non-significant factor while baseline viral load was significantly associated with the probability of an SVR.

CONCLUSIONS

Steatosis did not influence the efficacy of treatment in our study population. Baseline viral load is a confounding factor, particularly in patients infected with genotype 3 and once baseline viral load was accounted for, the association between steatosis and SVR was not relevant.

The accuracy of sonography in predicting steatosis and fibrosis in chronic hepatitis C

The accuracy and clinical significance of sonography (US) in demonstrating fatty liver and hepatic fibrosis in chronic hepatitis C (CHC) are rarely reported. US had sensitivity 71.1%, specificity 72.9%, 58.7% positive predictive value (PPV), and 82.3% negative predictive value (NPV) in demonstrating histological steatosis > or =5%. US had sensitivity 85.7%, specificity 60.4%, 13% PPV, and 98.4% NPV in demonstrating histological steatosis > or =30% with clinical significance in predicting prognosis and therapeutic response in CHC. Subjects with fatty liver on US had a greater prevalence of body mass index (BMI) > or =25 kg/m2, inflammation-necrosis grade >2, and total bilirubin <1.2 mg/dl in multivariate analyses. US had sensitivity 27.4%, specificity 62.5%, 71.9% PPV, and 19.7% NPV in demonstrating histological fibrosis of stage II or above, and sensitivity 13.6%, specificity 66.3%, 9.4% PPV, and 75.0% NPV in demonstrating fibrosis of stage III or above. There was no correlation between fibrotic sonographic patterns and histological stage of fibrosis (r = -0.167, P = 0.083). Besides hepatic steatosis, clinicians should be alert to the possibility of advanced necrosis-inflammation grade in interpreting a report of bright liver on gray-scale US. Gray-scale US cannot replace liver biopsy as the optimal diagnostic procedure for the prediction of hepatic steatosis and fibrosis prior to initiating therapy for CHC.

Review article: nonalcoholic fatty liver disease and hepatitis C virus--partners in crime

BACKGROUND

Both nonalcoholic fatty liver disease (NAFLD) and chronic hepatitis C (CHC) are frequent causes of chronic liver disease. In recent years, there have been significant revelations as regards the relationship between NAFLD and CHC.

AIM

To conduct a systematic, evidence-based review of the epidemiology, pathophysiology and potential treatments of coexistent NAFLD and CHC.

METHODS

The terms such as hepatitis C, fatty liver, NAFLD, nonalcoholic steatohepatitis and steatosis were searched on PubMed up to January 2008. References from selected articles and pertinent abstracts were also included.

RESULTS

Hepatic steatosis affects up to 80% of patients with CHC and is dependent on both viral and host factors. While insulin resistance (IR) is associated with hepatic steatosis and hepatitis C virus, genotype-specific pathogenic mechanisms have been identified and are currently the focus of intense investigation in the literature. Clinical implications of concurrent NAFLD, CHC and IR include increased disease progression, elevated risk of hepatocellular carcinoma, and decreased response to antiviral therapy.

CONCLUSIONS

NAFLD and IR are common in patients with CHC virus infection. IR is a driving force in the development of hepatic steatosis. Because of the clinical implications of hepatic steatosis and IR in the setting of CHC, further studies evaluating treatments, which may increase response to antiviral therapy, are needed.

Steatohepatitis: Risk factors and impact on disease severity in human immunodeficiency virus/hepatitis C virus coinfection

Hepatic steatosis has been reported in human immunodeficiency virus (HIV)/hepatitis C virus (HCV) coinfection. However, the features of steatohepatitis, including cytologic ballooning and pericellular fibrosis, its risk factors, and the impact on disease severity in such patients are unknown. To assess this, we prospectively reviewed liver histology in consecutive coinfected patients to define the prevalence and severity of the features of steatohepatitis, its risk factors, and its impact on the severity of liver disease. A total of 222 subjects (74% male, mean age 45, 78% African American, 90% genotype 1) were studied. The mean body mass index (BMI) was 26, and 18% had a BMI >30. The prevalence of risk factors for steatosis were: diabetes (31%), hypertension (15%), dyslipidemia (8%), metabolic syndrome (9%), and alcohol abuse (21%). Steatosis was present in 23% and steatohepatitis was present in 17%. The steatosis was mild (5%-33%) in 19%, and moderate to severe (>33%) in 4%. Cytologic ballooning and pericellular fibrosis were present in 30% and 13%, respectively. The mean Ishak score was 6.9, and 33% had bridging fibrosis or cirrhosis. Both steatosis and cytologic ballooning were associated with BMI, metabolic syndrome, and insulin resistance, and presence of either was strongly associated with advanced fibrosis (P < 0.0001). By multiple logistic regressions, the following associations were identified: increased BMI, diabetes, and genotype 3 with steatosis; diabetes with cytologic ballooning; and longer duration of infection with steatohepatitis.

CONCLUSION

Steatosis and steatohepatitis are present in 23% and 30%, respectively, of patients with HIV/HCV coinfection, and both are associated with an increased risk of having advanced fibrosis. Although we did identify genotype 3, increased BMI, and diabetes as risk factors, we found no independent association with antiretroviral therapy.

Adiponectin: a new independent predictor of liver steatosis and response to IFN-alpha treatment in chronic hepatitis C

OBJECTIVES

To compare serum adiponectin and tumor necrosis factor (TNF)-alpha among patients with viral liver diseases; to investigate associations of serum adiponectin and TNF-alpha with histological or viral characteristics of chronic hepatitis C (CHC); to investigate adiponectin and TNF-alpha alterations during interferon (IFN)-alpha treatment; and to assess the relationship between serum adiponectin and TNF-alpha and response rates to treatment.

METHODS

Adiponectin (mug/mL) and TNF-alpha (pg/mL) determinations by enzyme-linked immunosorbent assay (ELISA) in serial samples (before, the middle, the end, and 6 months after the end of treatment) from 83 CHC and 59 chronic hepatitis B (CHB) patients. Forty-three blood donors served as healthy controls. Patients were treated with IFN-alpha (4.5 MU/t.i.w.) for 12 months in CHB cases, and IFN-alpha (3 MU/t.i.w.) plus ribavirin for 6-12 months according to hepatitis C virus (HCV) genotype in CHC cases.

RESULTS

After adjustment for gender and body mass index (BMI), HCV genotype 3 overweight patients (BMI > 25 kg/m(2)) had significantly lower adiponectin (7.3 +/- 2.7) at baseline compared with non-3 HCV genotype overweight patients (P < 0.05). Lower adiponectin (HCV genotype 3, P= 0.02 and HCV genotype 1, P= 0.025) and higher TNF-alpha (P= 0.025) at baseline were identified as independent predictors of liver steatosis in CHC patients. Lower adiponectin was also identified as an independent predictor of no virological response at the end of treatment (odds ratio [OR] 0.76, 95% confidence interval [CI] 0.66-0.87, P < 0.001). At the end of IFN-alpha therapy, only HCV genotype 3 patients had significantly higher serum adiponectin (10.4 +/- 6.3) compared with its levels before treatment (8.7 +/- 4.7, P < 0.05).

CONCLUSIONS

This study suggests that HCV genotype 3 may directly affect adiponectin. This is further supported by the significant increase in adiponectin at the end of treatment only in HCV genotype 3 patients. Serum adiponectin at baseline appears to be an independent predictor of liver steatosis and for the achievement of end-of-treatment virological response, while serum TNF-alpha at baseline was identified as an independent predictor only of liver steatosis.

Hepatitis C virus core protein upregulates serine phosphorylation of insulin receptor substrate-1 and impairs the downstream akt/protein kinase B signaling pathway for insulin resistance

Chronic hepatitis C virus (HCV) infection has a significantly increased prevalence of type 2 diabetes mellitus (T2DM). Insulin resistance is a critical component of T2DM pathogenesis. Several mechanisms are likely to be involved in the pathogenesis of HCV-related insulin resistance. Since we and others have previously observed that HCV core protein activates c-Jun N-terminal kinase (JNK) and mitogen-activated protein kinase, we examined the contribution of these pathways to insulin resistance in hepatocytes. Our experimental findings suggest that HCV core protein alone or in the presence of other viral proteins increases Ser(312) phosphorylation of the insulin receptor substrate-1 (IRS-1). Hepatocytes infected with cell culture-grown HCV genotype 1a or 2a displayed a significant increase in the Ser(473) phosphorylation status of the Ser/Thr kinase protein kinase B (Akt/PKB), while Thr(308) phosphorylation was not significantly altered. HCV core protein-mediated Ser(312) phosphorylation of IRS-1 was inhibited by JNK (SP600125) and phosphatidylinositol-3 kinase (LY294002) inhibitors. A functional assay also suggested that hepatocytes expressing HCV core protein alone or infected with cell culture-grown HCV exhibited a suppression of 2-deoxy-d-[(3)H]glucose uptake. Inhibition of the JNK signaling pathway significantly restored glucose uptake despite HCV core expression in hepatocytes. Taken together, our results demonstrated that HCV core protein increases IRS-1 phosphorylation at Ser(312) which may contribute in part to the mechanism of insulin resistance.

Enhancement of de novo fatty acid biosynthesis in hepatic cell line Huh7 expressing hepatitis C virus core protein

Hepatitis C virus (HCV) core protein plays important roles in the pathogeneses of liver steatosis as well as hepatocellular carcinomas due to HCV infection. In this study, we examined de novo fatty acid biosynthesis in hepatic cell line Huh7 cells expressing HCV core protein. The rate of metabolic labeling of cellular fatty acids with [(3)H]acetate in core-expressing (Uc39-6) cells was ca. 1.5-fold higher than that in non-expressing (Uc321) cells. The enzyme activities responsible for fatty acid biosynthesis were assayed in vitro. Cytosolic acetyl-CoA carboxylase activity in Uc39-6 cells was ca. 1.6-fold higher than that in Uc321 cells. On the other hand, cytosolic fatty acid synthase activity in Uc39-6 cells was only slightly higher than that in Uc321 cells. Immunoblot analysis of acetyl-CoA carboxylase 1 (ACC1), which is a rate-limiting enzyme for fatty acid biosynthesis, revealed a higher expression level of the protein in Uc39-6 cells than in Uc321 cells. The ACC1 mRNA content in Uc39-6 cells was 1.4-fold higher than that in Uc321 cells. These results strongly suggest that enhancement of fatty acid biosynthesis in core-expressing cells is caused by increased expression of fatty acid biosynthetic enzymes, especially ACC1. Up-regulation of de novo fatty acid biosynthesis by HCV core protein may affect cellular lipid metabolism, resulting in neutral lipid accumulation in HCV-infected cells.

Hepatitis C virus core protein: an update on its molecular biology, cellular functions and clinical implications

The present review article is an update on various features of hepatitis C virus (HCV) core protein including its molecular biology, role in HCV replication, involvement in HCV pathogenesis, etiological role in hepatocellular carcinogenesis, significance in diagnosis and vaccination against HCV infection. Core protein is a structural protein of HCV virus and has only recently been characterized. It was found to play a major role in HCV-induced viral hepatitis. Although published information shows a lot about the clinical significance of HCV core protein, several studies are still needed to demonstrate its exact significance in viral biology and underlying HCV pathogenesis.