Application of network construction to estimate functional changes to insulin receptor substrates 1 and 2 in Huh7 cells following infection with the hepatitis C virus

Hepatitis C virus (HCV) is closely associated with insulin resistance (IS), acting primarily by interfering with insulin signaling pathways, increasing cytokine-mediated (tumor necrosis factor α, interleukin 6) inflammatory responses and enhancing oxidative stress. In the insulin signaling pathways, the insulin receptor substrate (IRS) is one of the key regulatory factors. The present study constructed gene regulatory sub-networks specific for IRS1 and IRS2 in Huh7 cells and HCV-infected Huh7 (HCV-Huh7) cells using linear programming and a decomposition algorithm, and investigated the possible mechanisms underlying the function of IRS1/2 in HCV-induced IS in Huh7 cells. All data were obtained from GSE20948 of the Gene Expression Omnibus database from the National Center for Biotechnology Information. Genes which were significantly differentially expressed between Huh7 and HCV-Huh7 cells were analyzed using the significance analysis of microarray algorithm. The top 50 genes, including IRS1/2, were used as target genes to determine the gene regulatory networks and next the sub-networks of IRS1 and IRS2 in HCV-Huh7 and Huh7 cells using Gene Regulatory Network Inference Tool, an algorithm based on linear programming and the decomposition process. The IRS1/2 sub-networks were divided into upstream/downstream groups and activation/suppression clusters, and were further analyzed using Molecule Annotation System 3.0 and Database for Annotation, Visualization, and Integrated Discovery software, two online platforms for enrichment and clustering analysis and visualization. The results indicated that in Huh7 cells, the downstream network of IRS2 is more complex than that of IRS1, indicating that the insulin metabolism in Huh7 cells may be primarily mediated by IRS2. In HCV-Huh7 cells, the downstream pathway of IRS2 is blocked, suggesting that this may be the underlying mechanism in HCV infection that leads to insulin resistance. The present findings add a further dimension to the understanding of the pathological mechanisms of HCV infection-associated insulin resistance, and provide novel concepts for insulin resistance and glucose metabolism research.

Alcohol, HIV/AIDS, and Liver Disease

Globally, there are over 33 million persons living with HIV/AIDS resulting in 1.8 million deaths annually. While the rate of HIV transmission is slowing, it is estimated that 2.6 million new infections occur yearly [1]. In the United States, there are approximately 1.2 million living with HIV/AIDS, with 50,000 new HIV infections and 17,000 deaths from the disease annually [2]. For those who can obtain effective antiretroviral therapy (ART), HIV/AIDS has become a chronic disease with life expectancies over 30 years [3]. Research in the last 10 years has revealed the importance of alcohol in the HIV/AIDS epidemic. Alcohol use, in moderate or hazardous amounts, has been associated with increased acquisition of HIV infection, progression of HIV infection, deleterious effects on HIV treatment, and acceleration in the comorbidities of HIV infection [4–9]. Yet alcohol remains the “forgotten drug” of the HIV/AIDS epidemic [10].

Insulin resistance is associated with progression to hepatic fibrosis in a cohort of HIV/hepatitis C virus-coinfected patients

OBJECTIVE

Hepatitis C virus (HCV) infection is associated with higher insulin levels and insulin resistance. We evaluated factors associated with insulin resistance in a cohort of HIV/HCV-coinfected patients and determined the effect of insulin resistance on the development of hepatic fibrosis.

METHODS

Data were analysed from 158 nondiabetic participants in a prospective Canadian cohort of HIV/HCV-coinfected patients. Patients were defined as having insulin resistance using the homeostasis model for assessment of insulin resistance (HOMA-IR) index. Factors associated with a high index (HOMA-IR ≥ 2) were identified using multivariate logistic regression. Incidence rates of liver fibrosis [aspartate aminotransferase- to-platelet ratio index (APRI) ≥ 1.5] were calculated, and multivariate time-dependent Cox regression models used to assess the effect of baseline insulin resistance on the risk of developing an APRI score of at least 1.5 during follow-up.

RESULTS

Overall, 56% had baseline HOMA-IR of at least 2. In the adjusted multivariate logistic analysis, only baseline BMI of more than 25 kg/m2 remained associated with insulin resistance [adjusted odds ratio 3.66, 95% confidence interval (CI) 1.70-7.92]. Rates of progression to significant hepatic fibrosis (APRI ≥ 1.5) were higher in those with HOMA-IR of at least 2 (16.32 per 100 person-years, 95% CI 6.68-25.97) compared with those with HOMA-IR less than 2 (7.95 per 100 person-years, 95% CI 0.16-15.75). Baseline HOMA-IR of at least 2 was associated with the development of significant fibrosis (adjusted hazard ratio 7.71, 95% CI 2.55-23.36).