Insulin Resistance Affects Early Virologic Response in HIV-Infected Subjects Treated for Hepatitis C Infection

Use of HOMA-IR in hepatitis C

Chronic infection with hepatitis C virus (HCV) can induce insulin resistance (IR) in a genotype-dependent manner and contributes to steatosis, progression of fibrosis and resistance to interferon plus ribavirin therapy. Our understanding of HCV-induced IR has improved considerably over the years, but certain aspects concerning its evaluation still remain elusive to clinical researchers. One of the most important issues is elucidating the ideal method for assessment of IR in the setting of hepatitis C. The hyperinsulinaemic euglycaemic clamp is the gold standard method for determining insulin sensitivity, but is impractical as it is labour intensive and time-consuming. To date, all human studies except for four where IR was evaluated in the HCV setting, an estimation of IR has been used rather than direct measurements of insulin-mediated glucose uptake. The most commonly used estimation in the HCV population is the homeostasis model assessment of insulin resistance (HOMA-IR) which is calculated from a single measurement of fasting insulin and glucose. In this article, we review the use and reporting of HOMA in the literature and provide guidance on its appropriate as well as inappropriate use in the hepatitis setting.

Current understanding of insulin resistance in hepatitis C

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

Insulin resistance impairs response to interferon plus ribavirin in patients coinfected with HIV and hepatitis C virus

BACKGROUND/AIMS

Controversy exists about whether insulin resistance (IR) affects response to treatment of hepatitis C. We evaluated the effect of IR on sustained virologic response (SVR) in HIV/hepatitis C virus (HCV)-coinfected patients treated with interferon plus ribavirin.

METHODS

We reviewed the clinical records of HIV/HCV-coinfected patients who received interferon plus ribavirin at our institution between July 2000 and March 2007. IR was defined as a homeostasis model assessment ≥ 3.8. SVR was defined as an undetectable HCV RNA at 24 weeks after the end of treatment. Efficacy was evaluated using an on-treatment (OT) analysis. Multivariate logistic regression analysis was used to evaluate factors associated with SVR.

RESULTS

During the study period, 218 patients were treated with interferon plus ribavirin; IR at baseline was available for 162 patients, and 134 were included in the OT analysis; HCV genotype (G) 1/4, 67%; F3-F4 fibrosis, 36%; IR 31%. SVR was achieved in 67 patients (50%) (79% in G 2/3 vs. 38% in G 1/4). IR was associated with a lower SVR [odds ratio (OR), 0.33; 95% confidence interval (CI): 0.15-0.72; P = 0.006). The independent variables related to SVR were genotype 2/3 (OR, 6.7; 95% CI: 2.71-16.98; P < 0.001), absence of IR at baseline (OR, 3.3; 95% CI: 1.36-8.26; P = 0.008), and nadir CD4 T-cell count (OR, 1.002; 95% CI: 1.00-1.00; P = 0.047).

CONCLUSIONS

Our data suggest that IR is an important determinant of SVR in HIV/HCV-coinfected patients treated with interferon plus ribavirin. Strategies to modify IR should be explored to enhance SVR during anti-HCV therapy.

Impact of obesity, steatosis and insulin resistance on progression and response to therapy of hepatitis C

Clinical progression of chronic hepatitis C depends on several cofactors, which also have a negative affect on the rate of response to interferon-alpha-based therapy. Given the current worldwide prevalence of the metabolic syndrome, the impact of obesity and insulin resistance, and of their histopathological correlate, hepatic steatosis, on the natural history and management of chronic hepatitis C is undoubtedly very important. We will review some of the current knowledge on the clinical consequences of overweight/obesity, steatosis and insulin resistance on chronic hepatitis C, and discuss how this issue may be dealt with in clinical practice.

Hepatitis C virus and type 2 diabetes

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