Hepatitis C virus infection promotes hepatic gluconeogenesis through an NS5A-mediated, FoxO1-dependent pathway. J Virol. 2011;85:8556-8568. [PMID: 21697492 DOI: 10.1128/jvi.00146-11]

Statins enhance extracellular release of hepatitis C virus particles through ERK5 activation

Statins, such as lovastatin, have been known to inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Statins were reported to moderately suppress hepatitis C virus (HCV) replication in cultured cells harboring HCV RNA replicons. We report here using an HCV cell culture (HCVcc) system that high concentrations of lovastatin (5-20 μg/mL) markedly enhanced the release of HCV infectious particles (virion) in the culture supernatants by up to 40 times, without enhancing HCV RNA replication, HCV protein synthesis, or HCV virion assembly in the cells. We also found that lovastatin increased the phosphorylation (activation) level of extracellular-signal-regulated kinase 5 (ERK5) in both the infected and uninfected cells in a dose-dependent manner. The lovastatin-mediated increase of HCV virion release was partially reversed by selective ERK5 inhibitors, BIX02189 and XMD8-92, or by ERK5 knockdown using small interfering RNA (siRNA). Moreover, we demonstrated that other cholesterol-lowering statins, but not dehydrolovastatin that is incapable of inhibiting HMG-CoA reductase and activating ERK5, enhanced HCV virion release to the same extent as observed with lovastatin. These results collectively suggest that statins markedly enhance HCV virion release from infected cells through HMG-CoA reductase inhibition and ERK5 activation.

Cellular Release of Infectious Hepatitis C Virus Particles via Endosomal Pathways

Hepatitis C virus (HCV) is a positive-sense, single-stranded RNA virus that causes chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. The release of infectious HCV particles from infected hepatocytes is a crucial step in viral dissemination and disease progression. While the exact mechanisms of HCV particle release remain poorly understood, emerging evidence suggests that HCV utilizes intracellular membrane trafficking and secretory pathways. These pathways include the Golgi secretory pathway and the endosomal trafficking pathways, such as the recycling endosome pathway and the endosomal sorting complex required for transport (ESCRT)-dependent multivesicular bodies (MVBs) pathway. This review provides an overview of recent advances in understanding the release of infectious HCV particles, with a particular focus on the involvement of the host cell factors that participate in HCV particle release. By summarizing the current knowledge in this area, this review aims to contribute to a better understanding of endosomal pathways involved in the extracellular release of HCV particles and the development of novel antiviral strategies.

Transcription Factor JunB Suppresses Hepatitis C Virus Replication

We previously reported that hepatitis C virus (HCV) infection activates the reactive oxygen species (ROS)/c-Jun N-terminal kinase (JNK) signaling pathway. Activation of JNK contributes to the development of liver diseases, including metabolic disorders, steatosis, liver cirrhosis and hepatocellular carcinoma. JNK is known to have numerous target genes, including JunB, a member of activator protein-1 transcription factor family. However, the roles of JunB in the HCV life cycle and HCV-associated pathogenesis remain unclear. To clarify a physiological role of JunB in HCV infection, we investigated the phosphorylation of JunB in HCV J6/JFH1-infected Huh-7.5 cells. Immunoblot analysis revealed that HCV-induced ROS/JNK activation promoted phosphorylation of JunB. The small interfering RNA (siRNA) knockdown of JunB significantly increased the amount of intracellular HCV RNA as well as the intracellular and extracellular HCV infectivity titers. Conversely, overexpression of JunB significantly reduced the amount of intracellular HCV RNA and the intracellular and extracellular HCV infectivity titers. These results suggest that JunB plays a role in inhibiting HCV propagation. Additionally, HCV-mediated JunB activation promoted hepcidin promoter activity and hepcidin mRNA levels, a key factor in modulating iron homeostasis, suggesting that JunB is involved in HCV-induced transcriptional upregulation of hepcidin. Taken together, we propose that the HCV-induced ROS/JNK/JunB signaling pathway plays roles in inhibiting HCV replication and contributing to HCV-mediated iron metabolism disorder.

Diabetogenic viruses: linking viruses to diabetes mellitus

Diabetes Mellitus (DM) is a group of chronic metabolic diseases distinguished by elevated glycemia due to the alterations in insulin metabolism. DM is one of the most relevant diseases of the modern world, with high incidence and prevalence worldwide, associated with severe systemic complications and increased morbidity and mortality rates. Although genetic factors and lifestyle habits are two of the main factors involved in DM onset, viral infections, such as enteroviruses, cytomegalovirus, hepatitis C virus, human immunodeficiency virus, severe acute respiratory syndrome coronavirus 2, among others, have been linked as triggers of type 1 (T1DM) and type 2 (T2DM) diabetes. Over the years, various groups identified different mechanisms as to how viruses can promote these metabolic syndromes. However, this field is still poorly explored and needs further research, as millions of people live with these pathologies. Thus, this review aims to ex-plore the different processes of how viruses can induce DM and their contribution to the prevalence and incidence of DM worldwide.

Unraveling the Molecular Mechanisms Involved in HCV-Induced Carcinogenesis

Cancer induced by a viral infection is among the leading causes of cancer. Hepatitis C Virus (HCV) is a hepatotropic oncogenic positive-sense RNA virus that leads to chronic infection, exposing the liver to a continuous process of damage and regeneration and promoting hepatocarcinogenesis. The virus promotes the development of carcinogenesis through indirect and direct molecular mechanisms such as chronic inflammation, oxidative stress, steatosis, genetic alterations, epithelial-mesenchymal transition, proliferation, and apoptosis, among others. Recently, direct-acting antivirals (DAAs) showed sustained virologic response in 95% of cases. Nevertheless, patients treated with DAAs have reported an unexpected increase in the early incidence of Hepatocellular carcinoma (HCC). Studies suggest that HCV induces epigenetic regulation through non-coding RNAs, DNA methylation, and chromatin remodeling, which modify gene expressions and induce genomic instability related to HCC development that persists with the infection's clearance. The need for a better understanding of the molecular mechanisms associated with the development of carcinogenesis is evident. The aim of this review was to unravel the molecular pathways involved in the development of carcinogenesis before, during, and after the viral infection's resolution, and how these pathways were regulated by the virus, to find control points that can be used as potential therapeutic targets.

Association Between the Risk of Hyperuricemia and Changes in Branched-Chain Amino Acids Intake Over Twelve Years: A Latent Class Trajectory Analysis From the China Health and Nutrition Survey, 1997-2009

Objective

This study aims to identify dietary branched-chain amino acids (BCAA) consumption trajectories in Chinese adults and to evaluate their association with the risk of hyperuricemia (HU).

Methods

Cohort data from the China Health and Nutrition Survey 1997–2009 were adopted in this research. A total of 6,810 participants aged ≥18 years were included in this study. Participants were designated into four subgroups on basis of the trajectories of dietary BCAA consumption. Cox proportional hazards models were performed to discuss the relationships between varied trajectories and the risk of HU after adjusting potential confounders. The intermediary effect of differential blood indexes between the trajectories and the risk of HU was explored with mediation analysis.

Results

Four distinct trajectory groups of dietary BCAA consumption were identified. Compared with the low stable trajectory group, high to low trajectory group was greatly related to an increased risk of HU (HR 1.35 (95% CI 1.03 to 1.79)) with modification for covariates. Total cholesterol (TC), hemoglobin A1c (HbA1c), fasting blood glucose (FBG), and triglyceride (TG) partially regulated trajectories and HU.

Conclusion

Gradually decreasing dietary BCAA intake increased the risk of HU, which is, at least, partially mediated by TC, HbA1c, FBG, and TG levels.

Hepatitis C Virus, Insulin Resistance, and Diabetes: A Review

Hepatitis C virus (HCV) infection and diabetes mellitus (DM) are two chronic diseases that are a cause of significant health and economic burdens worldwide. HCV is associated with the development of insulin resistance (IR) and diabetes mellitus (DM). The mechanisms through which HCV induces IR and DM include direct viral effects, pro-inflammatory cytokines and other immune-mediated processes. Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are both chronic diseases that involve impaired glucose homeostasis, albeit through different mechanisms. T1DM is an autoimmune disease that leads to the destruction of pancreatic beta cells resulting in insulin deficiency. In T2DM, a combination of peripheral insulin resistance and irregular production of insulin eventually lead to beta cell destruction and insulin insufficiency. Both type 1 and type 2 DM etiologies involve a combination of genetic and environmental factors. The data on HCV and T1DM association is limited, unlike T2DM, where a large body of evidence linking HCV to T2DM is available. Here, we intend to outline the current state of knowledge on HCV, IR, and DM. This article is protected by copyright. All rights reserved.

Signaling Induced by Chronic Viral Hepatitis: Dependence and Consequences

Chronic viral hepatitis is a main cause of liver disease and hepatocellular carcinoma. There are striking similarities in the pathological impact of hepatitis B, C, and D, although these diseases are caused by very different viruses. Paired with the conventional study of protein-host interactions, the rapid technological development of -omics and bioinformatics has allowed highlighting the important role of signaling networks in viral pathogenesis. In this review, we provide an integrated look on the three major viruses associated with chronic viral hepatitis in patients, summarizing similarities and differences in virus-induced cellular signaling relevant to the viral life cycles and liver disease progression.

Hepatitis C virus (HCV)-induced ROS/JNK signaling pathway activates the E3 ubiquitin ligase Itch to promote the release of HCV particles via polyubiquitylation of VPS4A

We previously reported that hepatitis C virus (HCV) infection activates the reactive oxygen species (ROS)/c-Jun N-terminal kinase (JNK) signaling pathway. However, the roles of ROS/JNK activation in the HCV life cycle still remain unclear. We sought to identify a novel role of ROS/JNK signaling pathway in the HCV life cycle. Immunoblot analysis revealed that HCV-induced ROS/JNK activation promoted phosphorylation of Itch, a HECT-type E3 ubiquitin ligase, leading to activation of Itch. The siRNA-knockdown of Itch significantly reduced the extracellular HCV infectivity titers, HCV RNA, and HCV core protein without affecting intracellular HCV infectivity titers, HCV RNA, and HCV proteins, suggesting that Itch is involved in release of HCV particles. HCV-mediated JNK/Itch activation specifically promoted polyubiquitylation of an AAA-type ATPase VPS4A, but not VPS4B, required to form multivesicular bodies. Site-directed mutagenesis revealed that two lysine residues (K23 and K121) on VPS4A were important for VPS4A polyubiquitylation. The siRNA-knockdown of VPS4A, but not VPS4B, significantly reduced extracellular HCV infectivity titers. Co-immunoprecipitation analysis revealed that HCV infection specifically enhanced the interaction between CHMP1B, a subunit of endosomal sorting complexes required for transport (ESCRT)-III complex, and VPS4A, but not VPS4B, whereas VPS4A K23R/K121R greatly reduced the interaction with CHMP1B. HCV infection significantly increased ATPase activity of VPS4A, but not VPS4A K23R/K121R or VPS4B, suggesting that HCV-mediated polyubiquitylation of VPS4A contributes to activation of VPS4A. Taken together, we propose that HCV-induced ROS/JNK/Itch signaling pathway promotes VPS4A polyubiquitylation, leading to enhanced VPS4A-CHMP1B interaction and promotion of VPS4A ATPase activity, thereby promoting the release of HCV particles. IMPORTANCE ROS/JNK signaling pathway contributes to liver diseases, including steatosis, metabolic disorders, and hepatocellular carcinoma. We previously reported that HCV activates the ROS/JNK signaling pathway, leading to the enhancement of hepatic gluconeogenesis and apoptosis induction. This study further demonstrates that HCV-induced ROS/JNK signaling pathway activates the E3 ubiquitin ligase Itch to promote release of HCV particles via polyubiquitylation of VPS4A. We provide evidence suggesting that HCV infection promotes the ROS/JNK/Itch signaling pathway and ESCRT/VPS4A machinery to release infectious HCV particles. Our results may lead to a better understanding of the mechanistic details of HCV particle release.

GP73 is a glucogenic hormone contributing to SARS-CoV-2-induced hyperglycemia

Severe cases of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are associated with elevated blood glucose levels and metabolic complications. However, the molecular mechanisms for how SARS-CoV-2 infection alters glycometabolic control are incompletely understood. Here, we connect the circulating protein GP73 with enhanced hepatic gluconeogenesis during SARS-CoV-2 infection. We first demonstrate that GP73 secretion is induced in multiple tissues upon fasting and that GP73 stimulates hepatic gluconeogenesis through the cAMP/PKA signaling pathway. We further show that GP73 secretion is increased in cultured cells infected with SARS-CoV-2, after overexpression of SARS-CoV-2 nucleocapsid and spike proteins and in lungs and livers of mice infected with a mouse-adapted SARS-CoV-2 strain. GP73 blockade with an antibody inhibits excessive glucogenesis stimulated by SARS-CoV-2 in vitro and lowers elevated fasting blood glucose levels in infected mice. In patients with COVID-19, plasma GP73 levels are elevated and positively correlate with blood glucose levels. Our data suggest that GP73 is a glucogenic hormone that likely contributes to SARS-CoV-2-induced abnormalities in systemic glucose metabolism.

Virus-induced FoxO factor facilitates replication of human cytomegalovirus

Recently, it was reported that the forkhead box O (FoxO) transcription factor promotes human cytomegalovirus (HCMV) replication via direct binding to the promoters of the major immediate-early (MIE) genes, but how the FoxO factor impacts HCMV replication remains unknown. Here, it is reported that FoxO1 expression is strongly induced by HCMV infection in cells of fibroblast origin. Suppression of the FoxO1 gene by specific RNA interference significantly inhibited HCMV growth and replication, but viral DNA synthesis was not affected considerably. Interestingly, depletion or overexpression of FoxO1 had a significant effect on the expression of viral early/late transcripts. FoxO1 was found to colocalize with the pUL44 protein subunit of viral replication compartments without direct association with DNA. This study highlights how FoxO enhances HCMV gene transcription and viral replication to promote infection.

Effect of different direct-acting antiviral regimens for treatment of nondiabetic hepatitis C virus–infected Egyptian patients on insulin resistance and sensitivity

Background

The association between hepatitis C virus (HCV), insulin resistance (IR), and metabolic syndrome has been extensively investigated. Direct-acting antivirals (DAAs) have a high sustained virologic response (SVR) rate, reaching > 90%. The effect of SVR after DAA treatment on metabolic parameters and IR in nondiabetic patients could be an important factor in the patient’s long-term outcome. The aim of the study is to evaluate the impact of different DAA regimens on IR and sensitivity in naïve chronic HCV-infected nondiabetic patients (before and after 12 weeks of treatment).

Methods

This prospective cohort study was conducted on 100 HCV-infected Child A nondiabetic patients eligible for DAA treatment in the Department of Gastroenterology and Hepatology, Ain Shams University, and Kobry El-Kobba Military Hospital among patients attending the outpatient clinic.

Patients were categorized into four groups according to the HCV regimens they received for 12 weeks.

All patient were subjected to the following tests before and 12 weeks after treatment: HCV quantitative PCR, Fibroscan, fasting insulin level (using insulin quantitative test kit), fasting and postprandial blood glucose (PPG), lipid profile, liver enzymes, BMI, and waist circumference.

Results

All patients achieved SVR at 12 weeks. In all treatment groups, lab was assessed before and after treatment, the 2-h PPG, high-density lipoprotein, and low-density lipoprotein levels showed statistically significant increases, whereas triglyceride, fasting glucose, hemoglobin A1C, and fasting plasma insulin levels showed statistically significant decreases. The homeostasis model assessment of insulin resistance (HOMA-IR) exhibited statistically significant decreases, whereas the quantitative insulin sensitivity check index (QUICKI) and Matsuda index showed statistically significant increases, across the four groups.

Conclusions

DAA treatment in naïve nondiabetic HCV-infected patients affects metabolic profile and insulin resistance/sensitivity, with similar effect among different DAA regimens.

Garcinol promotes hepatic gluconeogenesis by inhibiting P300/CBP-associated factor in late-pregnant sows

Disorder of hepatic glucose metabolism is the characteristic of late-pregnant sows. The purpose of our study was to look into the mechanism of garcinol on the improvement of hepatic gluconeogenic enzyme in late-pregnant sows. Thirty second- and third-parity sows (Duroc × Yorkshire × Landrace, n 10/diet) were fed a basal diet (control) or that diet supplemented with 100 mg/kg (Low Gar) or 500 mg/kg (High Gar) garcinol from day 90 of gestation to the end of farrowing. The livers were processed to measure enzymatic activity. Hepatocytes from pregnant sows were transfected with P300/CBP-associating factor (PCAF) small interfering RNA (siRNA) or treated with garcinol. Dietary garcinol had no effect on average daily feed intake, body weight (BW), backfat and BW gain of late-pregnant sows. Garcinol promoted plasma glucose levels in pregnant sows and newborn piglets. Garcinol up-regulated hepatic gluconeogenic enzyme expression and decreased PCAF activity. Garcinol had no effect on the expression of PPAR-γ co-activator 1α (PGC-1α) and Forkhead box O1 (FOXO1) but significantly increased their activity and decreased their acetylation in late-pregnant sows. Transfection of PCAF siRNA to hepatocytes of pregnant sows increased PGC-1α and FOXO1 activities. Furthermore, in hepatocytes of pregnant sows, garcinol treatment also up-regulated the activities of PGC-1α and FOXO1 and inhibited the acetylation of PGC-1α and FOXO1. Garcinol improves hepatic gluconeogenic enzyme expression in late-pregnant sows, and this may be due to the mechanism of down-regulating the acetylation of PGC-1α and FOXO1 induced by PCAF in isolated hepatocytes.

The anti-rotavirus effect of baicalin via the gluconeogenesis-related p-JNK-PDK1-AKT-SIK2 signaling pathway

Rotavirus (RV) infection is a leading cause of severe, dehydrating gastroenteritis in children < 5 years of age, and by now, the prevention and treatment of RV are still the major public health problems due to a lack of specific clinical drugs. Thus, the aims of this study are to explore the anti-RV effect of baicalin and its influence on glucose metabolism. Here, we demonstrated for the first time that baicalin had an anti-RV attachment effect with the strongest effect at a concentration of 100 μM, and also inhibited the replication of RV at concentrations of 100, 125, 150, 175, and 200 μM. Moreover, baicalin helped to overcome the weight loss and reduced the diarrhea rate and score with the best therapeutic effect at a concentration of 0.3 mg/g in RV-infected neonatal mice. Interestingly, baicalin decreased glucose consumption in RV-infected Caco-2 cells with the optimal concentration of 125 μM. Next, metabolomic analysis indicated that there were 68 differentially expressed metabolites, including an increase in pyruvic acid, asparagine, histidine and serine, and a decrease in dihydroxyacetone phosphate, which suggested that the underlying signaling pathway was gluconeogenesis. Further studies demonstrated that baicalin inhibited gluconeogenesis via improving glucose 6-phosphatase (G-6-Pase) and phosphoenolpyruvate carboxylase (PEPCK). Moreover, baicalin upregulated the potential gluconeogenesis proteins named salt inducible kinase 2, pyruvate dehydrogenase kinase 1, AKT serine/threonine kinase 1 and down-regulated phosphorylated c-Jun NH2-terminal kinase, which are associated with G-6-Pase and PEPCK expressions. Therefore, baicalin improved the gluconeogenesis disruption caused by RV.

Identification of an antiviral component from the venom of the scorpion Liocheles australasiae using transcriptomic and mass spectrometric analyses

Scorpion venom contains a variety of biologically active peptides. Among them, neurotoxins are major components in the venom, but it also contains peptides that show antimicrobial activity. Previously, we identified three insecticidal peptides from the venom of the Liocheles australasiae scorpion, but activities and structures of other venom components remained unknown. In this study, we performed a transcriptome analysis of the venom gland of the scorpion L. australasiae to gain a comprehensive understanding of its venom components. The result shows that potassium channel toxin-like peptides were the most diverse, whereas only a limited number of sodium channel toxin-like peptides were observed. In addition to these neurotoxin-like peptides, many non-disulfide-bridged peptides were identified, suggesting that these components have some critical roles in the L. australasiae venom. In this study, we also isolated a component with antiviral activity against hepatitis C virus using a bioassay-guided fractionation approach. By integrating mass spectrometric and transcriptomic data, we successfully identified LaPLA₂-1 as an anti-HCV component. LaPLA₂-1 is a phospholipase A₂ having a heterodimeric structure that is N-glycosylated at the N-terminal region. Since the antiviral activity of LaPLA₂-1 was inhibited by a PLA₂ inhibitor, the enzymatic activity of LaPLA₂-1 is likely to be involved in its antiviral activity.

Hepatitis C: clinical management and debated issues

Hepatitis C virus represents an important global health issue with 71 million of infected people in the word. Direct-acting antivirals are quite new molecules that hit specific Hepatitis C virus proteins useful for viral replication and assembly. Notably, Direct-acting antivirals bring to high sustained virological response rates showing also a great safety profile. This treatment revolution had an impact on transplantation world, in fact the number of liver transplants due to Hepatitis C virus-related cirrhosis and hepatocellular carcinoma is quickly decreasing. Even if this therapy has achieved excellent results in terms of morbility and mortality rates' reduction, there are some debated issues to consider. In the present review the main clinical challenges in every-day management of Hepatitis C virus patients treated with Direct-acting antivirals and the debated effects of viral clearance (metabolic, cardiovascular, immunologic and neoplastic) are discussed. The detection of barriers that can preclude the delivery of Hepatitis C virus care, is the most complex challenge for the scientific community. To obtain the Hepatitis C virus global eradication by 2030, as the World Health Organization has set, will be complex and laborious and will need a further multilevel effort.

Hepatitis C virus associated hepatocellular carcinoma

Liver cancer is a global problem and hepatocellular carcinoma (HCC) accounts for about 85% of this cancer. In the USA, etiologies and risk factors for HCC include chronic hepatitis C virus (HCV) infection, diabetes, non-alcoholic steatohepatitis (NASH), obesity, excessive alcohol drinking, exposure to tobacco smoke, and genetic factors. Chronic HCV infection appears to be associated with about 30% of HCC. Chronic HCV infection induces multistep changes in liver, involving metabolic disorders, steatosis, cirrhosis and HCC. Liver carcinogenesis requires initiation of neoplastic clones, and progression to clinically diagnose malignancy. Tumor progression associates with profound exhaustion of tumor-antigen-specific CD8⁺T cells, and accumulation of PD-1^hi CD8⁺T cells and Tregs. In this chapter, we provide a brief description of HCV and environmental/genetic factors, immune regulation, and highlight mechanisms of HCV associated HCC. We also underscore HCV treatment and recent paradigm of HCC progression, highlighted the current treatment and potential future therapeutic opportunities.

Direct-acting Antiviral in the Treatment of Chronic Hepatitis C: Bonuses and Challenges

Owing to the rapid development and wide clinical application of direct acting antiviral (DAA) drugs in the treatment of hepatitis C virus (HCV) infection, the era of interferon-based therapy has almost come to an end. Cumulative studies show that DAA therapy renders high cure efficiency (>90%) and good safety profile, and may even bring some unexpected benefits to the patients. However, some issues of concern arise, one of which is the resistance mutation of HCV genome leading to failure of treatment. With the aim of providing some meaningful references for the treatment of chronic hepatitis C (CHC), this article summarizes the research progress on benefits of DAA accompanied by viral clearance in the treatment of chronic hepatitis and the drug resistance.

The metabolic regulator small heterodimer partner contributes to the glucose and lipid homeostasis abnormalities induced by hepatitis C virus infection

BACKGROUND

Chronic hepatitis C virus (HCV) infection can predispose the host to metabolic abnormalities. The orphan nuclear receptor small heterodimer partner (SHP; NR0B2) has been identified as a key transcriptional regulatory factor of genes involved in diverse metabolic pathways. The protective effects of SHP against HCV-induced hepatic fibrosis have been reported. However, the exact mechanisms of its role on metabolism are largely unknown. We investigated the role of hepatic SHP in regulating glucose and lipid homeostasis, particularly in the metabolic stress response caused by HCV infection.

MATERIALS AND METHODS

Gluconeogenesis and lipogenesis levels and SHP expression were measured in HCV-infected cells, as well as in liver samples from HCV-infected patients and persistently HCV-infected mice.

RESULTS

We demonstrated that SHP is involved in gluconeogenesis via the acetylation of the Forkhead box O (FoxO) family transcription factor FoxO1, which is mediated by histone deacetylase 9 (HDAC9). Meanwhile, SHP regulates lipogenesis in the liver via suppressing the induction of sterol regulatory element-binding protein-1c (SREBP-1c) expression by the SUMOylation of Liver X receptor α (LXRα) at the SREBP-1c promoter. In particular, SHP can be strongly reduced upon stimulation, such as by HCV infection. The SHP expression levels were decreased in the livers from the CHC patients and persistently HCV-infected mice, and a negative correlation was observed between the SHP expression levels and gluconeogenic or lipogenic activities, emphasizing the clinical relevance of these results.

CONCLUSIONS

Our results suggest that SHP is involved in HCV-induced abnormal glucose and lipid homeostasis and that SHP could be a major target for therapeutic interventions targeting HCV-associated metabolic diseases.

Viral hijacking of cellular metabolism

This review discusses the current state of the viral metabolism field and gaps in knowledge that will be important for future studies to investigate. We discuss metabolic rewiring caused by viruses, the influence of oncogenic viruses on host cell metabolism, and the use of viruses as guides to identify critical metabolic nodes for cancer anabolism. We also discuss the need for more mechanistic studies identifying viral proteins responsible for metabolic hijacking and for in vivo studies of viral-induced metabolic rewiring. Improved technologies for detailed metabolic measurements and genetic manipulation will lead to important discoveries over the next decade.

'Beauty and the beast' in infection: How immune-endocrine interactions regulate systemic metabolism in the context of infection

The immune and endocrine systems ensure two vital functions in the body. The immune system protects us from lethal pathogens, whereas the endocrine system ensures proper metabolic function of peripheral organs by regulating systemic homeostasis. These two systems were long thought to operate independently. The immune system uses cytokines and immune receptors, whereas the endocrine system uses hormones to regulate metabolism. However, recent findings show that the immune and endocrine systems closely interact, especially regarding regulation of glucose metabolism. In response to pathogen encounter, cytokines modify responsiveness of peripheral organs to endocrine signals, resulting in altered levels of blood hormones such as insulin, which promotes the ability of the body to fight infection. Here we provide an overview of recent literature describing various mechanisms, which the immune system utilizes to modify endocrine regulation of systemic metabolism. Moreover, we will describe how these immune-endocrine interactions derail in the context of obesity. From a clinical perspective we will elaborate how infection and obesity aggravate the development of metabolic diseases such as diabetes mellitus type 2 in humans. In summary, this review provides a comprehensive overview of immune-induced changes in systemic metabolism following infection, with a focus on regulation of glucose metabolism.

Hepatitis C Virus Manipulates Humans as its Favorite Host for a Long-Term Relationship

Chronic hepatitis C virus (HCV) infection-associated liver disease is a global health problem. HCV often causes silent disease, and eventually progresses to end-stage liver disease. HCV infects hepatocytes; however, initial manifestation of liver disease is mostly displayed in hepatic stellate cells (HSCs), causing fibrosis/cirrhosis, and is believed to occur from inflammation in the liver. It remains unclear why HCV is not spontaneously cleared from infected liver in the majority of individuals and develops chronic infection with progressive liver disease. Direct-acting antivirals (DAAs) show excellent results in controlling viremia, although beneficial consequence in advanced liver disease remains to be understood. In this review, we highlight the current knowledge that has contributed to our understanding of the role of HCV in inflammation, immune evasion, metabolic disorders, liver pathogeneses, and efforts in vaccine development.

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.

Understanding Oxidative Stress in Aedes during Chikungunya and Dengue Virus Infections Using Integromics Analysis

Arboviral infection causes dysregulation of cascade of events involving numerous biomolecules affecting fitness of mosquito to combat virus. In response of the viral infection mosquito’s defense mechanism get initiated. Oxidative stress is among the first host responses triggered by the vector. Significant number of information is available showing changes in the transcripts and/or proteins upon Chikungunya virus and Dengue virus mono-infections and as co-infections. In the present study, we collected different -omics data available in the public database along with the data generated in our laboratory related to mono-infections or co-infections of these viruses. We analyzed the data and classified them into their respective pathways to study the role of oxidative stress in combating arboviral infection in Aedes mosquito. The analysis revealed that the oxidative stress related pathways functions in harmonized manner.

Broad-spectrum antiviral agents: secreted phospholipase A2 targets viral envelope lipid bilayers derived from the endoplasmic reticulum membrane

Hepatitis C virus (HCV), dengue virus (DENV) and Japanese encephalitis virus (JEV) belong to the family Flaviviridae. Their viral particles have the envelope composed of viral proteins and a lipid bilayer acquired from budding through the endoplasmic reticulum (ER). The phospholipid content of the ER membrane differs from that of the plasma membrane (PM). The phospholipase A2 (PLA2) superfamily consists of a large number of members that specifically catalyse the hydrolysis of phospholipids at a particular position. Here we show that the CM-II isoform of secreted PLA2 obtained from Naja mossambica mossambica snake venom (CM-II-sPLA2) possesses potent virucidal (neutralising) activity against HCV, DENV and JEV, with 50% inhibitory concentrations (IC50) of 0.036, 0.31 and 1.34 ng/ml, respectively. In contrast, the IC50 values of CM-II-sPLA2 against viruses that bud through the PM (Sindbis virus, influenza virus and Sendai virus) or trans-Golgi network (TGN) (herpes simplex virus) were >10,000 ng/ml. Moreover, the 50% cytotoxic (CC50) and haemolytic (HC50) concentrations of CM-II-sPLA2 were >10,000 ng/ml, implying that CM-II-sPLA2 did not significantly damage the PM. These results suggest that CM-II-sPLA2 and its derivatives are good candidates for the development of broad-spectrum antiviral drugs that target viral envelope lipid bilayers derived from the ER membrane.

Effect of branched-chain amino acid supplementation on insulin resistance and quality of life in chronic hepatitis C patients

The incidence rate of insulin resistance (IR) in patients with chronic hepatitis C (CHC) is high. Recently, branched-chain amino acids (BCAA) have been shown to attenuate IR in CHC patients; however, their effect on patient quality of life remains unclear. Therefore, the aim of the current prospective study was to determine the effects of BCAA supplement on IR and health-related quality of life (HR-QoL) in patients with CHC. In the study, 20 non-diabetic patients with CHC, who were non-responders to peginterferon-α and ribavirin, were recruited. Patients took a BCAA supplement once a day (30 g, after a minimum 10-h overnight fast) for 3 months. Serum levels of glucose, insulin, albumin, triglycerides and cholesterol were measured at 0 and 3 months. Additionally, IR was measured using the Homeostasis Model Assessment-IR, HR-QoL was assessed using the 36-item Short Form Health Survey and viral load was measured by reverse transcription polymerase chain reaction using Taqman probes. The Wilcoxon signed-rank test was used to determine statistical significance. The results indicated that 70% of the subjects were positive for IR, which decreased to 50% by the end of the study; furthermore, 85% of the subjects demonstrated some level of improvement. Overall, the BCAA treatment significantly decreased IR (P=0.006) and augmented serum albumin concentration (P=0.008) compared with basal values. Additionally, by the end of the treatment, viral load and triglycerides levels had decreased, though these results were not significant (P=0.084 and P=0.080, respectively). BCAA treatment also improved HR-QoL regarding role limitations due to physical health problems (P=0.017), role limitations due to emotional problems (P=0.026) and social function (P=0.008). In conclusion, BCAA supplementation reduced IR and improved HR-QoL in patients with CHC. These findings support the application of IR therapy as a possible therapeutic strategy for hepatitis C infection.

Targeting viperin improves diet-induced glucose intolerance but not adipose tissue inflammation

Viperin is an interferon-inducible antiviral protein, responsible for antiviral response to a variety of viral infections. Here, we show that silencing viperin by antisense oligonucleotides (ASO) protects against diet-induced glucose intolerance, and yet exacerbates adipose tissue inflammation. In high-fat diet-fed mice, viperin ASO improves glucose homeostasis, reduces plasma triglyceride concentrations and ameliorates diet-induced hepatic steatosis. Peripheral delivery of viperin by adeno-associated virus elevates fasting plasma glucose and insulin concentrations and reduces insulin-stimulated glucose uptake in skeletal muscle. Viperin overexpression reduces epinephrine- stimulated lipolysis in white adipose tissue, whereas viperin ASO increases expression of lipolytic genes. Targeting viperin by antisense oligonucleotides promotes reciprocal regulation of hepatic and adipose lipogenesis by reducing hepatic lipid content and increasing triacylglycerol content in adipose tissue. These findings reveal viperin as an important target to improve glucose metabolism, and suggest that suppressing antiviral potential may improve the metabolic adaptability to high-fat diet.

Role of HDAC9-FoxO1 Axis in the Transcriptional Program Associated with Hepatic Gluconeogenesis

Histone deacetylase 9 (HDAC9) regulates hepatic gluconeogenesis by deacetylating Forkhead box O 1 (FoxO1). HDAC9 upregulation is involved in hepatitis C virus (HCV)-associated exaggerated gluconeogenesis. Herein, we found in addition to FoxO1, HDAC9 also regulates other gluconeogenic transcription factors, including peroxisomeproliferator-activated receptor-γ coactivator-1α (PGC-1α), cyclic AMP-responsive element-binding protein (CREB), and glucocorticoid receptor (GR). Unlike FoxO1, which is regulated by post-translational modification responses to HDAC9, HDAC9 regulates PGC-1α, CREB and GR by altering gene expression. Similar to PGC-1α, CREB and GR were found to be novel regulatory targets of FoxO1 by examination of the FoxO1 binding site in their promoter. PGC-1α, CREB and GR were upregulated in response to HDAC9 via FoxO1 deacetylation. These findings indicate that HDAC9-FoxO1 signalling contributes to gluconeogenesis by modulating the expression of gluconeogenic transcription factors. In particular, metabolic profiling demonstrated a clear shift towards gluconeogenesis metabolism, and HDAC9-FoxO1 signalling can be strongly induced to upregulate gluconeogenic transcription factors following HCV infection. The positive correlation between HDAC9 and gluconeogenic transcription factor expression levels in the livers of both HCV-infected patients and normal individuals further emphasizes the clinical relevance of these results. Thus, HDAC9-FoxO1 signalling axis is involved in regulating gluconeogenic transcription factors, gluconeogenesis, and HCV-induced type 2 diabetes.

Hepatitis C virus induces a prediabetic state by directly impairing hepatic glucose metabolism in mice

Virus-related type 2 diabetes is commonly observed in individuals infected with the hepatitis C virus (HCV); however, the underlying molecular mechanisms remain unknown. Our aim was to unravel these mechanisms using FL-N/35 transgenic mice expressing the full HCV ORF. We observed that these mice displayed glucose intolerance and insulin resistance. We also found that Glut-2 membrane expression was reduced in FL-N/35 mice and that hepatocyte glucose uptake was perturbed, partly accounting for the HCV-induced glucose intolerance in these mice. Early steps of the hepatic insulin signaling pathway, from IRS2 to PDK1 phosphorylation, were constitutively impaired in FL-N/35 primary hepatocytes via deregulation of TNFα/SOCS3. Higher hepatic glucose production was observed in the HCV mice, despite higher fasting insulinemia, concomitant with decreased expression of hepatic gluconeogenic genes. Akt kinase activity was higher in HCV mice than in WT mice, but Akt-dependent phosphorylation of the forkhead transcription factor FoxO1 at serine 256, which triggers its nuclear exclusion, was lower in HCV mouse livers. These findings indicate an uncoupling of the canonical Akt/FoxO1 pathway in HCV protein-expressing hepatocytes. Thus, the expression of HCV proteins in the liver is sufficient to induce insulin resistance by impairing insulin signaling and glucose uptake. In conclusion, we observed a complete set of events leading to a prediabetic state in HCV-transgenic mice, providing a valuable mechanistic explanation for HCV-induced diabetes in humans.

Hepatitis C virus NS5A protein interacts with lysine methyltransferase SET and MYND domain-containing 3 and induces activator protein 1 activation

Hepatitis C virus (HCV) non-structural protein 5A (NS5A) is a multifunctional protein that is involved in the HCV life cycle and pathogenesis. In this study, a host protein(s) interacting with NS5A by tandem affinity purification were searched for with the aim of elucidating the role of NS5A. An NS5A-interacting protein, SET and MYND domain-containing 3 (SMYD3), a lysine methyltransferase reportedly involved in the development of cancer, was identified. The interaction between NS5A and SMYD3 was confirmed in ectopically expressing, HCV RNA replicon-harboring and HCV-infected cells. The other HCV proteins did not bind to SMYD3. SMYD3 bound to NS5A of HCV genotypes 1b and 2a. Deletion mutational analysis revealed that domains II and III of NS5A (amino acids [aa] 250 to 447) and the MYND and N-SET domains of SMYD3 (aa 1 to 87) are involved in the full extent of NS5A-SMYD3 interaction. NS5A co-localized with SMYD3 exclusively in the cytoplasm, thereby inhibiting nuclear localization of SMYD3. Moreover, NS5A formed a complex with SMYD3 and heat shock protein 90 (HSP90), which is a positive regulator of SMYD3. The intensity of binding between SMYD3 and HSP90 was enhanced by NS5A. Luciferase reporter assay demonstrated that NS5A significantly induces activator protein 1 (AP-1) activity, this being potentiated by co-expression of SMYD3 with NS5A. Taken together, the present results suggest that NS5A interacts with SMYD3 and induces AP-1 activation, possibly by facilitating binding between HSP90 and SMYD3. This may be a novel mechanism of AP-1 activation in HCV-infected cells.

Hepatitis C virus-induced glucose metabolic disorder

Hepatitis C virus (HCV) infection often causes intrahepatic diseases, such as chronic hepatitis, liver chirrohsis, and hepatocellular carcinoma (HCC). Moreover, HCV infection exhibits various extrahepatic manifestations, such as thyroiditis, glucose and lipid metabolic disorder, and iron metabolic disorder. HCV infection is often associated with type 2 diabetes, involving hepatic fibrosis and poor prognosis. Type 2 diabetes increases the risk of HCC. We have been investigating molecular mechanisms of HCV-induced glucose metabolic disorder and we reported that HCV infection promotes hepatic gluconeogenesis through forkhead box O1 (FoxO1)-dependent pathway and that HCV infection suppresses the cell surface expression of glucose transporter 2 (GLUT2), resulting in suppression of glucose uptake. We have found that HCV NS5A protein plays important roles in these two independent pathways. Here we discuss the roles of HCV NS5A in HCV-induced glucose metabolic disorder.

TGF-β1/Smad3 Pathway Targets PP2A-AMPK-FoxO1 Signaling to Regulate Hepatic Gluconeogenesis

Maintenance of glucose homeostasis is essential for normal physiology. Deviation from normal glucose levels, in either direction, increases susceptibility to serious medical complications such as hypoglycemia and diabetes. Maintenance of glucose homeostasis is achieved via functional interactions among various organs: liver, skeletal muscle, adipose tissue, brain, and the endocrine pancreas. The liver is the primary site of endogenous glucose production, especially during states of prolonged fasting. However, enhanced gluconeogenesis is also a signature feature of type 2 diabetes (T2D). Thus, elucidating the signaling pathways that regulate hepatic gluconeogenesis would allow better insight into the process of normal endogenous glucose production as well as how this process is impaired in T2D. Here we demonstrate that the TGF-β1/Smad3 signaling pathway promotes hepatic gluconeogenesis, both upon prolonged fasting and during T2D. In contrast, genetic and pharmacological inhibition of TGF-β1/Smad3 signals suppressed endogenous glucose production. TGF-β1 and Smad3 signals achieved this effect via the targeting of key regulators of hepatic gluconeogenesis, protein phosphatase 2A (PP2A), AMP-activated protein kinase (AMPK), and FoxO1 proteins. Specifically, TGF-β1 signaling suppressed the LKB1-AMPK axis, thereby facilitating the nuclear translocation of FoxO1 and activation of key gluconeogenic genes, glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. These findings underscore an important role of TGF-β1/Smad3 signaling in hepatic gluconeogenesis, both in normal physiology and in the pathophysiology of metabolic diseases such as diabetes, and are thus of significant medical relevance.

Implications of oxidative stress on viral pathogenesis

Reactive species are frequently formed after viral infections. Antioxidant defences, including enzymatic and non-enzymatic components, protect against reactive species, but sometimes these defences are not completely adequate. An imbalance in the production of reactive species and the body's inability to detoxify these reactive species is referred to as oxidative stress. The aim of this review is to analyse the role of oxidative stress in the pathogenesis of viral infections and highlight some major therapeutic approaches that have gained importance, with regards to controlling virus-induced oxidative injury. Attention will be focused on DNA viruses (papillomaviruses, hepadnaviruses), RNA viruses (flaviviruses, orthomyxoviruses, paramyxoviruses, togaviruses) and retroviruses (human immunodeficiency virus). In general, viruses cause an imbalance in the cellular redox environment, which depending on the virus and the cell can result in different responses, e.g. cell signaling, antioxidant defences, reactive species, and other processes. Therefore, the modulation of reactive species production and oxidative stress potentially represents a novel pharmacological approach for reducing the consequences of viral pathogenesis.

Interaction of the hepatitis B virus X protein with the lysine methyltransferase SET and MYND domain-containing 3 induces activator protein 1 activation

Hepatitis B virus (HBV) is a widespread human pathogen that often causes chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. The detailed mechanisms underlying HBV pathogenesis remain poorly understood. The HBV X protein (HBx) is a multifunctional regulator that modulates viral replication and host cell functions, such as cell cycle progression, apoptosis and protein degradation through interaction with a variety of host factors. Recently, the nonstructural protein 5A (NS5A) of hepatitis C virus has been reported to interact with methyltransferase SET and MYND domain-containing 3 (SMYD3), which is implicated in chromatin modification and development of cancer. Because HBx shares fundamental regulatory functions concerning viral replication and pathogenesis with NS5A, it was decided to examine whether HBx interacts with SMYD3. In the present study, it was demonstrated by co-immunoprecipitation analysis that HBx interacts with both ectopically and endogenously expressed SMYD3 in Huh-7.5 cells. Deletion mutation analysis revealed that the C-terminal region of HBx (amino acids [aa] 131-154) and an internal region of SMYD3 (aa 269-288) are responsible for their interaction. Immunofluorescence and proximity ligation assays showed that HBx and SMYD3 co-localize predominantly in the cytoplasm. Luciferase reporter assay demonstrated that the interaction between HBx and SMYD3 activates activator protein 1 (AP-1) signaling, but not that of nuclear factor-kappa B (NF-κB). On the other hand, neither overexpression nor knockdown of SMYD3 altered production of HBV transcripts and HBV surface antigen (HBsAg). In conclusion, a novel HBx-interacting protein, SMYD3, was identified, leading to proposal of a novel mechanism of AP-1 activation in HBV-infected cells.

Benzylglucosinolate Derived Isothiocyanate from Tropaeolum majus Reduces Gluconeogenic Gene and Protein Expression in Human Cells

Nasturtium (Tropaeolum majus L.) contains high concentrations of benzylglcosinolate. We found that a hydrolysis product of benzyl glucosinolate-the benzyl isothiocyanate (BITC)-modulates the intracellular localization of the transcription factor Forkhead box O 1 (FOXO1). FoxO transcription factors can antagonize insulin effects and trigger a variety of cellular processes involved in tumor suppression, longevity, development and metabolism. The current study evaluated the ability of BITC-extracted as intact glucosinolate from nasturtium and hydrolyzed with myrosinase-to modulate i) the insulin-signaling pathway, ii) the intracellular localization of FOXO1 and, iii) the expression of proteins involved in gluconeogenesis, antioxidant response and detoxification. Stably transfected human osteosarcoma cells (U-2 OS) with constitutive expression of FOXO1 protein labeled with GFP (green fluorescent protein) were used to evaluate the effect of BITC on FOXO1. Human hepatoma HepG2 cell cultures were selected to evaluate the effect on gluconeogenic, antioxidant and detoxification genes and protein expression. BITC reduced the phosphorylation of protein kinase B (AKT/PKB) and FOXO1; promoted FOXO1 translocation from cytoplasm into the nucleus antagonizing the insulin effect; was able to down-regulate the gene and protein expression of gluconeogenic enzymes; and induced the gene expression of antioxidant and detoxification enzymes. Knockdown analyses with specific siRNAs showed that the expression of gluconeogenic genes was dependent on nuclear factor (erythroid derived)-like2 (NRF2) and independent of FOXO1, AKT and NAD-dependent deacetylase sirtuin-1 (SIRT1). The current study provides evidence that BITC might have a role in type 2 diabetes T2D by reducing hepatic glucose production and increasing antioxidant resistance.

Classical swine fever virus NS5A protein changed inflammatory cytokine secretion in porcine alveolar macrophages by inhibiting the NF-κB signaling pathway

Background

Classical swine fever (CSF) caused by CSF virus (CSFV) is a highly contagious disease of the pigs. A number of studies have suggested that CSFV non-structural (NS) 5A protein is involved in CSFV-associated pathogenesis, but its mechanism is still uncertain. The aim of this study was to investigate the roles of NS5A protein in CSFV-associated pathogenesis in cultured porcine alveolar macrophages (PAMs).

Methods

After PAMs cultured in vitro were transfected with CSFV NS5A, the alterations in IL-1β, IL-6 and TNF-α expression were determined by ELISA, the RIG-I signaling activity related to inflammatory cytokine secretion was investigated by Western blot and Immunofluorescent staining.

Results

It was suggested that, the stable expressed CSFV NS5A solely had no influence on the expressions of inflammatory cytokines IL-1β, IL-6 and TNF-α in PAMs Moreover, NS5A protein could suppressed IL-1β, IL-6 and TNF-α expression induced by poly(I:C). It was also showed that NS5A protein did not impair the expressions of RIG-I, MDA5, IPS-1, NF-κB and IkBα in cells without poly(I:C) stimulation. Protein expressions of RIG-I, MDA5, IPS-1, NF-κB were not disrupted by NS5A protein in poly(I:C)-stimulated cells, while poly(I:C)-induced NF-κB nuclear translocation and activity was obviously suppressed by this protein. A suppression in poly(I:C)-induced IkBα degradation in NS5A-expressing cells was also observed.

Conclusion

These data indicated that CSFV NS5A protein could inhibit the secretion of inflammatory cytokine induced by poly(I:C) through the suppression of the NF-κB signaling pathway, indicating the participation of CSFV NS5A protein in the pathogenesis of CSFV.

Hepatitis C Virus Infection Induces Autophagy as a Prosurvival Mechanism to Alleviate Hepatic ER-Stress Response

Hepatitis C virus (HCV) infection frequently leads to chronic liver disease, liver cirrhosis and hepatocellular carcinoma (HCC). The molecular mechanisms by which HCV infection leads to chronic liver disease and HCC are not well understood. The infection cycle of HCV is initiated by the attachment and entry of virus particles into a hepatocyte. Replication of the HCV genome inside hepatocytes leads to accumulation of large amounts of viral proteins and RNA replication intermediates in the endoplasmic reticulum (ER), resulting in production of thousands of new virus particles. HCV-infected hepatocytes mount a substantial stress response. How the infected hepatocyte integrates the viral-induced stress response with chronic infection is unknown. The unfolded protein response (UPR), an ER-associated cellular transcriptional response, is activated in HCV infected hepatocytes. Over the past several years, research performed by a number of laboratories, including ours, has shown that HCV induced UPR robustly activates autophagy to sustain viral replication in the infected hepatocyte. Induction of the cellular autophagy response is required to improve survival of infected cells by inhibition of cellular apoptosis. The autophagy response also inhibits the cellular innate antiviral program that usually inhibits HCV replication. In this review, we discuss the physiological implications of the HCV-induced chronic ER-stress response in the liver disease progression.

Physical and functional interaction between hepatitis C virus NS5A protein and ovarian tumor protein deubiquitinase 7B

Hepatitis C virus (HCV) NS5A protein plays crucial roles in viral RNA replication, virus assembly, and viral pathogenesis. Although NS5A has no known enzymatic activity, it modulates various cellular pathways through interaction with cellular proteins. HCV NS5A (and other HCV proteins) are reportedly degraded through the ubiquitin-proteasome pathway; however, the physiological roles of ubiquitylation and deubiquitylation in HCV infection are largely unknown. To elucidate the role of deubiquitylation in HCV infection, an attempt was made to identify a deubiquitinase (DUB) that can interact with NS5A protein. An ovarian tumor protein (OTU), deubiquitinase 7B (OTUD7B), was identified as a novel NS5A-binding protein. Co-immunoprecipitation analyses showed that NS5A interacts with OTUD7B in both Huh-7 and HCV RNA replicon cells. Immunofluorescence staining revealed that HCV NS5A protein colocalizes with OTUD7B in the cytoplasm. Moreover, HCV infection was found to enhance the nuclear localization of OTUD7B. The OTUD7B-binding domain on NS5A was mapped using a series of NS5A deletion mutants. The present findings suggest that the domain I of NS5A is important and the region from amino acid 121 to 126 of NS5A essential for the interaction. Either V121A or V124A mutation in NS5A disrupts the NS5A-OTUD7B interaction. The results of this in vivo ubiquitylation assay suggest that HCV NS5A enhances OTUD7B DUB activity. Taken together, these results suggest that HCV NS5A protein interacts with OTUD7B, thereby modulating its DUB activity.

Sulforaphane Suppresses Hepatitis C Virus Replication by Up-Regulating Heme Oxygenase-1 Expression through PI3K/Nrf2 Pathway

Hepatitis C virus (HCV) infection-induced oxidative stress is a major risk factor for the development of HCV-associated liver disease. Sulforaphane (SFN) is an antioxidant phytocompound that acts against cellular oxidative stress and tumorigenesis. However, there is little known about its anti-viral activity. In this study, we demonstrated that SFN significantly suppressed HCV protein and RNA levels in HCV replicon cells and infectious system, with an IC50 value of 5.7 ± 0.2 μM. Moreover, combination of SFN with anti-viral drugs displayed synergistic effects in the suppression of HCV replication. In addition, we found nuclear factor erythroid 2-related factor 2 (Nrf2)/HO-1 induction in response to SFN and determined the signaling pathways involved in this process, including inhibition of NS3 protease activity and induction of IFN response. In contrast, the anti-viral activities were attenuated by knockdown of HO-1 with specific inhibitor (SnPP) and shRNA, suggesting that anti-HCV activity of SFN is dependent on HO-1 expression. Otherwise, SFN stimulated the phosphorylation of phosphoinositide 3-kinase (PI3K) leading Nrf2-mediated HO-1 expression against HCV replication. Overall, our results indicated that HO-1 is essential in SFN-mediated anti-HCV activity and provide new insights in the molecular mechanism of SFN in HCV replication.

The Metabolic Regulator Histone Deacetylase 9 Contributes to Glucose Homeostasis Abnormality Induced by Hepatitis C Virus Infection

Class IIa histone deacetylases (HDACs), such as HDAC4, HDAC5, and HDAC7, provide critical mechanisms for regulating glucose homeostasis. Here we report that HDAC9, another class IIa HDAC, regulates hepatic gluconeogenesis via deacetylation of a Forkhead box O (FoxO) family transcription factor, FoxO1, together with HDAC3. Specifically, HDAC9 expression can be strongly induced upon hepatitis C virus (HCV) infection. HCV-induced HDAC9 upregulation enhances gluconeogenesis by promoting the expression of gluconeogenic genes, including phosphoenolpyruvate carboxykinase and glucose-6-phosphatase, indicating a major role for HDAC9 in the development of HCV-associated exaggerated gluconeogenic responses. Moreover, HDAC9 expression levels and gluconeogenic activities were elevated in livers from HCV-infected patients and persistent HCV-infected mice, emphasizing the clinical relevance of these results. Our results suggest HDAC9 is involved in glucose metabolism, HCV-induced abnormal glucose homeostasis, and type 2 diabetes.

Insulin resistance and prediabetes in hepatitis C virus patients

BACKGROUND

Egypt has the highest prevalence of hepatitis C virus (HCV) infection in the world and is facing an epidemic of type 2 diabetes mellitus. The objective of this study was to assess the prevalence of insulin resistance (IR) and prediabetes among HCV patients.

METHODS

A cross-sectional case-control study was performed on 188 HCV patients admitted to the Internal Medicine Department in Menoufia University Hospital during the period from May to August 2014. Seventy persons were taken as controls. Body mass index (BMI), serum fasting glucose and fasting insulin were determined. IR was calculated by the Homeostasis Model for Assessment of Insulin Resistance (HOMA-IR), where a value of >2.0 was considered as IR and that >4.0 was considered as prediabetic state.

RESULTS

Prediabetes was significantly higher among HCV group compared with the control group. Serum fasting glucose, fasting insulin and HOMA-IR levels were significantly higher among prediabetic HCV group compared with both non-prediabetic HCV and control groups.

CONCLUSIONS

HCV patients should be assessed for IR and prediabetes in their routine evaluation to avoid the double burden of diabetes mellitus and HCV.

Profiling Kinase Activity during Hepatitis C Virus Replication Using a Wortmannin Probe

To complete its life cycle, the hepatitis C virus (HCV) induces changes to numerous aspects of its host cell. As kinases act as regulators of many pathways utilized by HCV, they are likely enzyme targets for virally induced inhibition or activation. Herein, we used activity-based protein profiling (ABPP), which allows for the identification of active enzymes in complex protein samples and the quantification of their activity, to identify kinases that displayed differential activity in HCV-expressing cells. We utilized an ABPP probe, wortmannin-yne, based on the kinase inhibitor wortmannin, which contains a pendant alkyne group for bioconjugation using bioorthogonal chemistry. We observed changes in the activity of kinases involved in the mitogen-activated protein kinase pathway, apoptosis pathways, and cell cycle control. These results establish changes to the active kinome, as reported by wortmannin-yne, in the proteome of human hepatoma cells actively replicating HCV. The observed changes include kinase activity that affect viral entry, replication, assembly, and secretion, implying that HCV is regulating the pathways that it uses for its life cycle through modulation of the active kinome.

Modulation of Innate Immune Signalling by Lipid-Mediated MAVS Transmembrane Domain Oligomerization

RIG-I-like receptors detect viral RNA in infected cells and promote oligomerization of the outer mitochondrial membrane protein MAVS to induce innate immunity to viral infection through type I interferon production. Mitochondrial reactive oxygen species (mROS) have been shown to enhance anti-viral MAVS signalling, but the mechanisms have remained obscure. Using a biochemical oligomerization-reporter fused to the transmembrane domain of MAVS, we found that mROS inducers promoted lipid-dependent MAVS transmembrane domain oligomerization in the plane of the outer mitochondrial membrane. These events were mirrored by Sendai virus infection, which similarly induced lipid peroxidation and promoted lipid-dependent MAVS transmembrane domain oligomerization. Our observations point to a role for mROS-induced changes in lipid bilayer properties in modulating antiviral innate signalling by favouring the oligomerization of MAVS transmembrane domain in the outer-mitochondrial membrane.

HCV upregulates Bim through the ROS/JNK signalling pathway, leading to Bax-mediated apoptosis

We previously reported that hepatitis C virus (HCV) infection induces Bax-triggered, mitochondrion-mediated apoptosis by using the HCV J6/JFH1 strain and Huh-7.5 cells. However, it was still unclear how HCV-induced Bax activation. In this study, we showed that the HCV-induced activation and mitochondrial accumulation of Bax were significantly attenuated by treatment with a general antioxidant, N-acetyl cysteine (NAC), or a specific c-Jun N-terminal kinase (JNK) inhibitor, SP600125, with the result suggesting that the reactive oxygen species (ROS)/JNK signalling pathway is upstream of Bax activation in HCV-induced apoptosis. We also demonstrated that HCV infection transcriptionally activated the gene for the pro-apoptotic protein Bim and the protein expression of three major splice variants of Bim (BimEL, BimL and BimS). The HCV-induced increase in the Bim mRNA and protein levels was significantly counteracted by treatment with NAC or SP600125, suggesting that the ROS/JNK signalling pathway is involved in Bim upregulation. Moreover, HCV infection led to a marked accumulation of Bim on the mitochondria to facilitate its interaction with Bax. On the other hand, downregulation of Bim by siRNA (small interfering RNA) significantly prevented HCV-mediated activation of Bax and caspase 3. Taken together, these observations suggest that HCV-induced ROS/JNK signalling transcriptionally activates Bim expression, which leads to Bax activation and apoptosis induction.

Predictive roles of intraoperative blood glucose for post-transplant outcomes in liver transplantation

Diabetogenic traits in patients undergoing liver transplantation (LT) are exacerbated intraoperatively by exogenous causes, such as surgical stress, steroids, blood transfusions, and catecholamines, which lead to intraoperative hyperglycemia. In contrast to the strict glucose control performed in the intensive care unit, no systematic protocol has been developed for glucose management during LT. Intraoperative blood glucose concentrations typically exceed 200 mg/dL in LT, and extreme hyperglycemia (> 300 mg/dL) is common during the neohepatic phase. Only a few retrospective studies have examined the relationship between intraoperative hyperglycemia and post-transplant complications, with reports of infectious complications or mortality. However, no prospective studies have been conducted regarding the influence of intraoperative hyperglycemia in LT on post-transplant outcome. In addition to absolute blood glucose values, the temporal patterns in blood glucose levels during LT may serve as prognostic features. Persistent neohepatic hyperglycemia (without a decline) throughout LT is a useful indicator of early graft dysfunction. Moreover, intraoperative variability in glucose levels may predict the need for reoperation for hemorrhage after LT. Thus, there is an urgent need for guidelines for glucose control in these patients, as well as prospective studies on the impact of glucose control on various post-transplant complications. This report highlights some of the recent studies related to perioperative blood glucose management focused on LT and liver disease.