Insulin resistance, hepatic steatosis and hepatitis C: A complex relationship with relevant clinical implications

Hepatitis C Genotype 3 Infection: Pathogenesis and Treatment Horizons

Genotype 3 hepatitis C infection is the second most common genotype worldwide and accounts for most infections in Southeast Asia. It is a particularly ominous genotype because it has been linked to increased mortality, specifically increased late-stage liver events, accelerated development of hepatic fibrosis, and an increased risk of hepatocellular carcinoma. As new treatment regimens for hepatitis C have been emerging, treatment of genotype 3 often requires longer treatment duration with decreased response rates as compared with other genotypes.

Nuclear receptors control pro-viral and antiviral metabolic responses to hepatitis C virus infection

Viruses lack the basic machinery needed to replicate and therefore must hijack the host's metabolism to propagate. Virus-induced metabolic changes have yet to be systematically studied in the context of host transcriptional regulation, and such studies shoul offer insight into host-pathogen metabolic interplay. In this work we identified hepatitis C virus (HCV)-responsive regulators by coupling system-wide metabolic-flux analysis with targeted perturbation of nuclear receptors in primary human hepatocytes. We found HCV-induced upregulation of glycolysis, ketogenesis and drug metabolism, with glycolysis controlled by activation of HNF4α, ketogenesis by PPARα and FXR, and drug metabolism by PXR. Pharmaceutical inhibition of HNF4α reversed HCV-induced glycolysis, blocking viral replication while increasing apoptosis in infected cells showing virus-induced dependence on glycolysis. In contrast, pharmaceutical inhibition of PPARα or FXR reversed HCV-induced ketogenesis but increased viral replication, demonstrating a novel host antiviral response. Our results show that virus-induced changes to a host's metabolism can be detrimental to its life cycle, thus revealing a biologically complex relationship between virus and host.

An outbreak of HCV genotype 6a and 2a infection in South China: Confirmation of iatrogenic transmission by phylogenetic analysis of the NS5B region

An outbreak of hepatitis C virus (HCV) infections, for which the risk factor was unknown, was previously identified in North Guangdong, China. In the present study, a total of 736 local residents were surveyed regarding their lifetime risk factors for HCV infection. Serum anti‑HCV antibodies and HCV RNA were examined to confirm infection. In the HCV‑positive samples, the core and nonstructural protein 5B sequences were amplified, and phylogenetic analysis was performed to determine the association between HCV subtypes and transmission routes. A total of 374 individuals were positive for anti‑HCV antibodies. Blood transfusion, blood product transfusion, people who inject drugs and intravenous injection at a local clinic were identified as independent risk factors for HCV infection. Phylogenetic analysis revealed that the two predominant subtypes of HCV, 2a and 6a, were primarily focused in four homologous clusters. Patients with a history of intravenous injection at a local clinic were more likely to be found in the four clusters, compared with patients exposed to other risk factors. The present emergency retrospective survey showed a specific epidemiological feature of HCV infection in Zijin County and found genetic homology among individuals exposed to intravenous injection at a local clinic. Further evidence is required to confirm the causal association between the outbreak of HCV infection and intravenous injection.

Sustained Virologic Response to a Dual Peginterferon alfa-2a and Ribavirin in Treating Chronic hepatitis C Infection: A Retrospective Cohort Study

In Myanmar, hepatitis C virus (HCV) infection prevalence is 2%. A combination therapy of pegylated interferon alfa-2a and ribavirin (PEG-IFNa/RBV) is a standard treatment, but the effect of this antiviral therapy needs evaluation as to determine the efficacy and safety of dual PEG-IFNa/RBV therapy in treating patients infected with HCV in Myanmar.This was a retrospective analysis of data from a single clinic exclusively for gastrointestinal diseases in Yangon, Myanmar. We assessed treatment responses at the defined time points and stratified by genotypes of HCV. We also determined incidences of adverse events (AEs). We investigated independent predictors of sustained virologic response (SVR) in the participants.A total of 362 HCV-infected cases were included in this study. The majority were females (51.7%) with mean age of 47.12 years (±11.6) and noncirrhosis patients (82%). Rapid virologic response (RVR), early virologic response (EVR), end of treatment response (ETR), and SVR 24 weeks after completion of the dual treatment were 50.3% (178/362), 88% (314/357), 80.1% (286/357), and 85.6% (167/195), respectively. The most frequently reported AEs were nausea/anorexia (72.8%) and flu-like symptoms (62.4%). In multivariate analysis, 4 factors were independently associated with SVR; SVR to genotype 3 (odds ratio [OR] 2.4, 95% CI: 1.24-4.62), EVR (OR 0.54, 95% CI: 0.3-0.95), and duration of treatment (OR 1.52, 95% CI: 1.18-1.98). Study limitations were acknowledged.The efficacy and safety of the dual therapy in treating HCV-infected patient in Myanmar was acceptable. We recommend a prospective randomized control trial looking at duration of therapy and rates of achieving SVR, which could significantly impact the care of HCV-infected patients in Myanmar and perhaps other countries as well.

Functional implications of mitochondrial reactive oxygen species generated by oncogenic viruses

Between 15-20% of human cancers are associated with infection by oncogenic viruses. Oncogenic viruses, including HPV, HBV, HCV and HTLV-1, target mitochondria to influence cell proliferation and survival. Oncogenic viral gene products also trigger the production of reactive oxygen species which can elicit oxidative DNA damage and potentiate oncogenic host signaling pathways. Viral oncogenes may also subvert mitochondria quality control mechanisms such as mitophagy and metabolic adaptation pathways to promote virus replication. Here, we will review recent progress on viral regulation of mitophagy and metabolic adaptation and their roles in viral oncogenesis.

Is alanine aminotransferase associated with osteopenia in middle-aged and elderly Chinese?

OBJECTIVE

To investigate the association between alanine aminotransferase (ALT) levels and risk of osteopenia in middle-aged and elderly Chinese with ALT within the normal range.

METHODS

This was a cross-sectional study. A total of 4,890 men and women (pre- and postmenopausal) aged 40 years or older were randomly recruited from Fujian, China. Each participant was required to complete a questionnaire and then undergo anthropometric, biochemical, and bone mineral density measurements.

RESULTS

The odds ratio of osteopenia decreased significantly with increasing ALT level at baseline. The three groups (men, pre- and postmenopausal women) were divided by ALT quartiles. In multiple logistic regression models using the first quartile as the reference, after adjusting for corresponding confounding factors, the odds ratios of osteopenia across the other ALT quartiles were 0.576 (95% confidence interval [CI], 0.390 to 0.851), 0.654 (95% CI, 0.460 to 0.930), and 0.629 (95% CI, 0.427 to 0.926) for premenopausal women, and 0.949 (95% CI, 0.699 to 1.289), 0.733 (95% CI, 0.540 to 0.995), and 0.692 (95% CI, 0.508 to 0.943) for postmenopausal women (not significant for quartile 2). However, no significantly different results were found in men. Multiple linear regression models showed that serum ALT concentrations were positively associated with the homeostasis model assessment of insulin resistance.

CONCLUSION

Our study of middle-aged and elderly Chinese men and women demonstrates that the prevalence of osteopenia is inversely associated with ALT level when ALT is within the normal range.

Hepatitis C virus dysregulates glucose homeostasis by a dual mechanism involving induction of PGC1α and dephosphorylation of FoxO1

The maintenance of glucose homeostasis is a complex process in which the insulin signalling pathway plays a major role. Disruption of insulin-regulated glucose homeostasis is frequently observed in chronic hepatitis C (CHC) infection and might potentially contribute to type 2 diabetes mellitus (T2DM) development. Presently, the mechanism that links HCV infection to insulin resistance remains unclear. Previously, we have reported that HCV protein expression in HCV transgenic mice (B6HCV) leads to an overexpression of protein phosphatase 2A (PP2A) through an ER stress response. In the present work, we describe an association of FoxO1 hypophosphorylation and upregulation of both PGC-1α and G6Pase to phenotypic hyperglycaemia and insulin resistance in B6HCV mice. In vitro, we observed that PGC1α is concomitantly induced with PP2A. Moreover, we show that the enhanced PP2A expression is sufficient to inhibit insulin-induced FoxO1 phosphorylation via blockade of insulin-mediated Akt activation or/and through direct association and dephosphorylation of pS-FoxO1. Consequently, we found that the gluconeogenic gene glucose-6-phosphatase is upregulated. These observations were confirmed in liver biopsies obtained from CHC patients. In summary, our results show that HCV-mediated upregulation of PP2A catalytic subunit alters signalling pathways that control hepatic glucose homeostasis by inhibiting Akt and dephosphorylation of FoxO1.

HCV and oxidative stress in the liver

Hepatitis C virus (HCV) is the etiological agent accounting for chronic liver disease in approximately 2-3% of the population worldwide. HCV infection often leads to liver fibrosis and cirrhosis, various metabolic alterations including steatosis, insulin and interferon resistance or iron overload, and development of hepatocellular carcinoma or non-Hodgkin lymphoma. Multiple molecular mechanisms that trigger the emergence and development of each of these pathogenic processes have been identified so far. One of these involves marked induction of a reactive oxygen species (ROS) in infected cells leading to oxidative stress. To date, markers of oxidative stress were observed both in chronic hepatitis C patients and in various in vitro systems, including replicons or stable cell lines expressing viral proteins. The search for ROS sources in HCV-infected cells revealed several mechanisms of ROS production and thus a number of cellular proteins have become targets for future studies. Furthermore, during last several years it has been shown that HCV modifies antioxidant defense mechanisms. The aim of this review is to summarize the present state of art in the field and to try to predict directions for future studies.

Evolving epidemiology of hepatitis C virus in the United States

The impact of hepatitis C virus (HCV) infection on health and medical care in the United States is a major problem for infectious disease physicians. Although the incidence of HCV infection has declined markedly in the past 2 decades, chronic infection in 3 million or more residents now accounts for more disease and death in the United States than does human immunodeficiency virus (HIV)/AIDS. Current trends in the epidemiology of HCV infection include an apparent increase in young, often suburban heroin injection drug users who initiate use with oral prescription opioid drugs; infections in nonhospital healthcare (clinic) settings; and sexual transmission among HIV-infected persons. Infectious disease physicians will increasingly have the responsibility of diagnosing and treating HCV patients. An understanding of how these patients were infected is important for determining whom to screen and treat.

Differentially expressed microRNAs in Huh-7 cells expressing HCV core genotypes 3a or 1b: potential functions and downstream pathways

microRNA (miRNA) dysfunction is believed to play important roles in human diseases, including viral infectious diseases. Hepatitis C virus (HCV) infection promotes the development of steatosis, cirrhosis and hepatocellular carcinoma, which is genotype-specific. In order to characterize the miRNA expression profile of Huh-7 cells expressing the HCV core 3a vs. 1b, microarrays and real-time PCR were performed. Consequently, 16 miRNAs (5 miRNAs upregulated and 11 miRNAs downregulated) were found to be dysregulated. In addition, we generated the predicted and validated targets of the differentially expressed miRNAs and explored potential downstream function categories and pathways of target genes using databases of Gene Ontology (GO) and PANTHER and the database for annotation, visualization and integrated discovery (David). The computational results indicated that the dysregulated miRNAs might perform the functions of cellular metabolism and cellular growth. Finally, these biological effects were preliminarily validated. This study identifies a specific miRNA expression profile in cells expressing HCV core proteins of different genotypes (genotype 3a and 1b), which may account for the variable pathophysiological manifestation associated with HCV infection.

Association of hepatitis C with insulin resistance and type 2 diabetes in US general population: the impact of the epidemic of obesity

Studies from tertiary care medical centres have linked hepatitis C virus (HCV) to the development of insulin resistance (IR) and type 2 diabetes. The aim of the study is to assess the relationship between HCV positivity and insulin resistance/diabetes in the US population. Three cycles of the National Health and Nutrition Examination Survey (NHANES) conducted between 1988 and 2008 were used. HCV infection was diagnosed using a positive serologic anti-HCV test. Additionally, diabetes was diagnosed as fasting blood glucose ≥126 mg/dL and/or the use of hypoglycaemic medications. Insulin resistance was defined as a homeostasis of model assessment (HOMA) score of >3.0. Logistic regression was used to estimate the odds ratios (ORs) of each of the potential risk factors for diabetes mellitus (DM). The SUDAAN 10.0 was used to run descriptive and regression analyses. A total of 39 506 individuals from three NHANES cycles (1988-1994, 1999-2004 and 2005-2008) with complete demographic and relevant clinical data were included. Over these three NHANES cycles, prevalence of hepatitis C did not significantly change. During the first NHANES cycle (1988-1994), insulin and diabetes were independently associated with hepatitis C. However, during the later study cycles (1998-2008), these associations were no longer significant. In contrast, other important known risk factors for diabetes and IR (male gender, non-Caucasian race, age and obesity) remained significant over all three NHANES cycles. Although HCV infection was independently associated with an increased risk of diabetes and IR in the US population over a decade ago, assessment of the later NHANES cycles shows that this relationship may have become diluted by the rapid rise of other risks for diabetes, specifically, the prevalence of obesity.

The association between Helicobacter pylori infection and insulin resistance: a systematic review

BACKGROUND

Helicobacter pylori infection has been associated with diverse extradigestive morbidity, including insulin resistance (IR) syndrome. The aim of this systematic review was to summarize the epidemiologic evidence concerning the association between H. pylori infection and IR quantitative indexes.

MATERIALS AND METHODS

A computerized literature search in PubMed electronic databases and Cochrane Central Register of Controlled Trials was performed.

RESULTS

Nine studies reporting data on 2120 participants were finally eligible for this systematic review. Seven of them were cross-sectional studies and two were nonrandomized, open-label, controlled trials investigating the effect of H. pylori eradication on IR. Homeostatic model of assessment insulin resistance (HOMA-IR) was used in all studies to quantify IR. There seems to be a trend toward a positive association between H. pylori infection and HOMA-IR, strengthened by regression analysis in one study. However, there was significant heterogeneity between studies regarding the method(s) of H. pylori infection diagnosis based on and the study populations. The studies for the effect of H. pylori eradication on HOMA-IR revealed conflicting results.

CONCLUSIONS

Although data seem to indicate a potential association between H. pylori infection and IR, further studies are needed to strengthen this association and to clarify whether there is a causative link between them. If a causal link is confirmed in the future, this may have a major impact on the pathophysiology and management of IR syndrome, including type 2 diabetes mellitus and nonalcoholic fatty liver disease.