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Reduction of Insulin Resistance With Effective Clearance of Hepatitis C Infection: Results From the HALT-C Trial

Published:February 15, 2010DOI:https://doi.org/10.1016/j.cgh.2010.01.022

      Background & Aims

      Hepatitis C virus (HCV) infection is associated with an increased prevalence of diabetes and insulin resistance (IR); whether this is a causal relationship has not been established.

      Methods

      We performed a longitudinal study within the lead-in phase of the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (HALT-C) Trial to evaluate whether suppression of hepatitis C is associated with improvement in IR. Participants had advanced hepatic fibrosis and carried non-3 HCV genotypes (n = 96). Patients underwent 24 weeks of pegylated interferon and ribavirin therapy and were categorized into HCV clearance groups at week 20 on the basis of HCV RNA levels; null responders had <1 log10 decline (n = 38), partial responders had ≥1 log10 decline (n = 37) but detectable HCV RNA, and complete responders had no detectable HCV RNA (n = 21). The primary outcome was change (week 20 minus week 0) in IR by using the homeostasis model assessment (HOMA2-IR).

      Results

      Adjusting only for baseline HOMA2-IR, mean HOMA2-IR differences were −2.23 (complete responders), −0.90 (partial responders), and +0.18 (null responders) (P = .036). The observed differences in mean HOMA2-IR scores were ordered in a linear fashion across response groups (P = .01). The association between HCV clearance and improvement in HOMA2-IR could not be accounted for by adiponectin or tumor necrosis factor–alpha and was independent of potential confounders including age, gender, ethnicity, body mass index, duration of infection, medications used, and fibrosis.

      Conclusions

      HCV suppression correlates with improvement in IR. These data provide further support for a role of HCV in the development of insulin resistance.

      Keywords

      Abbreviations used in this paper:

      AN (adiponectin), BMI (body mass index), HALT-C (Hepatitis C Antiviral Long-Term Treatment against Cirrhosis), HOMA2-IR (homeostasis model assessment), IR (insulin resistance), TMA (transcription-mediated amplification), TNF-α (tumor necrosis factor–α)
      A number of studies have demonstrated a strong association between HCV infection and insulin resistance (IR),
      • Narita R.
      • Abe S.
      • Kihara Y.
      • Akiyama T.
      • et al.
      Insulin resistance and insulin secretion in chronic hepatitis C virus infection.
      • Delgado-Borrego A.
      • Casson D.
      • Schoenfeld D.
      • et al.
      Hepatitis C virus is independently associated with increased insulin resistance after liver transplantation.
      • White D.L.
      • Ratziu V.
      • El-Serag H.B.
      Hepatitis C infection and risk of diabetes: a systematic review and meta-analysis.
      providing a possible link between this infection and diabetes mellitus. Indeed, findings of a correlation between increasing HCV RNA levels and greater IR have suggested that HCV might directly or indirectly induce IR.
      • Hui J.M.
      • Sud A.
      • Farrell G.C.
      • et al.
      Insulin resistance is associated with chronic hepatitis C and virus infection fibrosis progression.
      • Delgado-Borrego A.
      • Liu Y.S.
      • Jordan S.H.
      • et al.
      Prospective study of liver transplant recipients with HCV infection: evidence for a causal relationship between HCV and insulin resistance.
      • Kawaguchi T.
      • Yoshida T.
      • Harada M.
      • et al.
      Hepatitis C virus down-regulates insulin receptor substrates 1 and 2 through up-regulation of suppressor of cytokine signaling 3.
      • Shintani Y.
      • Fujie H.
      • Miyoshi H.
      • et al.
      Hepatitis C virus infection and diabetes: direct involvement of the virus in the development of insulin resistance.
      Despite the evidence for relatively higher than expected levels of IR in HCV infection, causality remains to be established. The cross-sectional nature of most of the relevant literature and the presence of multiple confounders have precluded accurate interpretations regarding cause and effect. With a mouse model, Shintani et al
      • Shintani Y.
      • Fujie H.
      • Miyoshi H.
      • et al.
      Hepatitis C virus infection and diabetes: direct involvement of the virus in the development of insulin resistance.
      demonstrated a contribution of HCV to the development of IR. However, the question of whether HCV directly contributes to IR in a human cohort remains unanswered.
      The study of IR in the setting of de novo HCV infection might be most informative. However, given the limited number of acute infections, a much more practical means of addressing causality in a clinical study is to determine whether IR improves with clearance of HCV infection. If HCV is a causal factor, then clearance of viremia should be associated with reduced IR.
      Thus, the question of whether IR improves with clearance of HCV infection merits further investigation. To address this question, we performed a nested study within the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (HALT-C) Trial comparing complete responders with partial responders and null responders to antiviral therapy during the lead-in phase of treatment. Furthermore, the possible role of adipocytokines as mediators in the association between HCV and IR was explored.

      Patients and Methods

       Study Subjects

      Patients who participated in the lead-in phase of the HALT-C Trial were considered for inclusion. HALT-C participants were nonresponders to previous round(s) of interferon treatment (with or without ribavirin) for HCV infection with advanced hepatic fibrosis or cirrhosis. The lead-in phase was a 24-week period of treatment with pegylated interferon-alfa 2a (180 μg/week) and ribavirin (1000–1200 mg/day depending on body weight) and has been described in previous HALT-C publications.
      • Lee W.M.
      • Dienstag J.L.
      • Lindsay K.L.
      • et al.
      Evolution of the HALT-C Trial: pegylated interferon as maintenance therapy for chronic hepatitis C in previous interferon nonresponders.
      Only HALT-C participants who were documented to be fasting at the time of blood sample collections and who were not taking glucose-lowering medications (or who did not have a history of diabetes mellitus) (n = 108) were included. Subjects with HCV genotype 3 and those with undetectable insulin levels at any time point were excluded (n = 12). A total of 96 subjects from the 2 centers with documented fasting status were included (Saint Louis University School of Medicine, n = 55, and Massachusetts General Hospital, n = 41). All patients were followed longitudinally from week 0 until week 20 of the lead-in phase.

       Subject Characteristics

      Baseline demographic characteristics included age, gender, race, and history of diabetes mellitus. Waist circumference, weight, height, and systolic and diastolic blood pressure at week 0 and at week 20 of the study were reviewed. Liver biopsies were evaluated by a team of 12 pathologists. Hepatic steatosis was graded on a scale of 0–4,
      • Lok A.S.
      • Everhart J.E.
      • Chung R.T.
      • et al.
      Hepatic steatosis in hepatitis C: comparison of diabetic and nondiabetic patients in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis trial.
      and fibrosis was staged on the basis of the scale described by Ishak.
      • Ishak K.G.
      Pathologic features of chronic hepatitis: a review and update.
      Patients with a fibrosis stage 5 or 6 were considered as having cirrhosis.

       Laboratory Determinations

      All sample collections were taken after at least an 8-hour fast at week 0 and week 20. Routine chemistries including lipids, glucose, liver enzymes, bilirubin levels, and prothrombin time were obtained in local laboratories within the participating clinical centers by standard assays. HCV RNA testing was performed at the HALT-C central virology laboratory (University of Washington, Seattle, WA) by using commercial assays (quantitative and qualitative COBAS Amplicor Monitor HCV assay version 2.0; Roche Molecular Diagnostics, Pleasanton, CA). The Virology lab subsequently tested all week 20 samples with the VERSANT HCV RNA Qualitative Assay (Bayer Diagnostics, Berkeley, CA), on the basis of transcription-mediated amplification (TMA) technology (lower limit of HCV RNA detection of 10 IU/mL).
      • Hendricks D.A.
      • Friesenhahn M.
      • Tanimoto L.
      • et al.
      Multicenter evaluation of the VERSANT HCV RNA qualitative assay for detection of hepatitis C virus RNA.
      Fasting insulin levels were tested at the University of Michigan, Ann Arbor, MI by a radioimmunoassay.
      • Hayashi M.
      • Floyd Jr, J.C.
      • Pek S.
      • et al.
      Insulin, proinsulin, glucagon and gastrin in pancreatic tumors and in plasma of patients with organic hyperinsulinism.
      Frozen samples were shipped to Massachusetts General Hospital in Boston, MA for measurement of adipocytokines. Adiponectin (AN) levels were quantified by using enzyme-linked immunosorbent assay (Linco Research, St Charles, MO), whereas tumor necrosis factor–alpha (TNF-α) levels were measured by using a highly sensitive enzyme-linked immunosorbent assay (R & D Systems, Minneapolis, MN). Manufacturers' instructions were followed for both adipocytokine measures, and all adipocytokine samples were measured in duplicate.

       Definitions and Calculations

      Final AN and TNF-α levels represented an average of the duplicate values obtained per sample. Body mass index (BMI) was calculated as weight (kg) divided by height squared (m2). IR was calculated by using the homeostasis model assessment 2 (HOMA2) from the publicly available software provided by its original authors (http://www.dtu.ox.ac.uk/homa).
      • Wallace T.M.
      • Levy J.C.
      • Matthews D.R.
      Use and abuse of HOMA modeling.
      We did not exclude or truncate any insulin or glucose values in this IR cohort.
      • Lok A.S.
      • Everhart J.E.
      • Chung R.T.
      • et al.
      Hepatic steatosis in hepatitis C: comparison of diabetic and nondiabetic patients in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis trial.
      Eradication of viremia was represented as a categorical variable in which subjects were classified as complete responders (no detectable HCV RNA at week 20), partial responders (drop in HCV RNA of ≥1 log10 from week 0), or null responders (decline in HCV RNA <1 log10). Complete responders were further evaluated to confirm their status by using the more sensitive TMA assay.
      • Morishima C.
      • Morgan T.R.
      • Everhart J.E.
      • et al.
      HCV RNA detection by TMA during the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) trial.
      Among complete responders, only one was positive by TMA assay. This subject was then recategorized as a partial responder.

       Statistical Analysis

      To evaluate the association between response to HCV therapy and change in IR over time, a multiple linear regression model was constructed in which change in HOMA2-IR (week 20 minus week 0) was the dependent and response to therapy categories the independent effect. To avoid confounding from baseline IR, ln HOMA2-IR at week 0 (because of lack of normality) was included in the initial model. In the second part of the analysis, the potential role of AN and TNF-α in the association between HCV and IR was explored in univariate and multivariate models. Correlations between each of these adipocytokines and HCV infection were evaluated. Baseline AN and TNF-α entered into the regression model. Then a more comprehensive model was built for identification of potential confounders by analysis of clinically relevant variables. Variables associated with the outcome at a significance level (P value) of ≤.1 were selected for inclusion in the more parsimonious final model. Finally, center and a center by HCV treatment response interaction were evaluated in the final model to exclude the possibility of confounding on the basis of participating institution. JMP Statistical Software version 7 (SAS Institute, Cary, NC) was used for all statistical analyses. All analyses were performed at the University of Miami by using a dataset provided by the HALT-C data coordinating center (New England Research Institutes).

      Results

       Baseline Characteristics

      As mentioned previously, our cohort represents a subgroup within the HALT-C Trial. Descriptive statistics for the cohort are presented in Table 1. The median age was 49 years, and the majority of participants were white men. The median duration of infection for our group was 29 years. Mean BMI was 30.4 kg/m2. The majority of subjects had advanced fibrosis or cirrhosis, and 34% had moderate or advanced steatosis. Mean baseline glucose was 107.3 mg/dL, and mean HOMA 2-IR at week 0 was 4.8. Potential differences between the 2 centers were evaluated. No statistically significant differences between the centers were noted in any of the variables except for triglyceride levels at week 0 (mean, 147 [Saint Louis University School of Medicine] vs 100 [Massachusetts General Hospital] mg/dL, P = .0025).
      Table 1Baseline Characteristics of Cohort
      VariableFrequency n (%), median (range), or mean (SD) (n = 96)
      Age (y)49 (33–73)
      Male gender73 (76%)
      Race
       White87 (91%)
       Black9 (9%)
      Estimated duration of infection (y)29 (7–49)
      Mean systolic/mean diastolic blood pressure (mm Hg)133 (16.7)/81 (9.0)
      Waist circumference (cm)99 (13.4)
      BMI (kg/m2)30.4 (5.3)
      Log HCV RNA6.5 (0.4)
      Fibrosis (Ishak score)
       2–452 (54%)
       5–644 (46%)
      Steatosis (Brunt scale)
       0–163 (66%)
       2–333 (34%)
      Glucose (mg/dL)107.3 (32.1)
      Insulin (μIU/mL)42.5 (41.5)
      HOMA2-IR4.8 (3.2)
      AN (ng/mL)42.5 (15.6)
      TNF-α (pg/mL)3.0 (2.1)
      SD, standard deviation.

       Clearance of Hepatitis C Virus Correlates With Improvement of Insulin Resistance

      Clearance of HCV was established on the basis of week 20 HCV response categories. In our cohort, there were 21 complete responders, 37 partial responders, and 38 nonresponders to HCV therapy. Our initial model evaluated the correlation between eradication of the virus (represented by HCV clearance categories) and change in HOMA2-IR (week 20 – week 0) while controlling for baseline HOMA2-IR. A 10% increase in baseline HOMA2 was associated with a reduction in HOMA2 by 0.4 units (P < .01). The adjusted mean HOMA2-IR differences (week 20 – week 0) across the 3 virologic clearance categories were −2.23 for complete responders, −0.90 for partial responders, and 0.18 for nonresponders (P = .036). The observed mean HOMA2-IR difference scores were ordered in a linear fashion across response groups, and this linear trend was statistically significant (F1,92 = 6.8, P = .01) (Figure 1). The linear trend accounted for virtually all of the variation observed in the HOMA2-IR difference scores.
      Figure thumbnail gr1
      Figure 1Side-by-side quartile box and whisker plots of difference in HOMA2-IR by HCV clearance categories. Box plots represent median (center line in boxes), means (open circles), 25th to 75th percentiles (box ends), and 5th to 95th percentiles (whisker ends) of HOMA2-IR difference scores, n = 96. Mean HOMA2-IR differences are −2.23 (complete responders), −0.90 (partial responders), and +0.18 (null responders) (P = .036), adjusted for natural log of baseline HOMA2-IR. HOMA2-IR difference scores were ordered in a linear fashion across response groups, and this linear trend was statistically significant (F1,92 = 6.8, P = .01).

       Association Between Hepatitis C Virus Clearance and Improvement in Insulin Resistance Appears to Be Independent of Serum Adiponectin and/or Tumor Necrosis Factor–α

      Analyses were conducted to evaluate whether the association between HCV and IR could be explained, at least in part, by respective changes in AN and/or TNF-α. We found no significant association in our cohort between HCV clearance or change in HCV RNA levels (week 20 – week 0) and change in AN. A trend toward a negative correlation between change in AN and change in HOMA2-IR (week 20 – week 0) was noted, but this did not achieve statistical significance (r = –0.14, P = .19) (Figure 2). Baseline AN and change in AN were entered into the regression model described above, and we found that a 1-unit increase in baseline AN correlated with a reduction in IR of 0.05 HOMA2-IR units (P = .02), whereas a 1-unit change in AN (week 20 – week 0) did not have a statistically significant correlation with change in IR (r = –0.05, P = .07). We found that men (n = 71) had statistically lower mean baseline AN levels (40.1 ng/mL) than women (n = 21, 50.4 ng/mL), but entering gender in muiltivariate models did not change our findings. No significant correlations were noted between TNF-α and HCV clearance or change in HOMA2-IR in our cohort. Evaluating TNF-α in the regression model did not change the previous results because only HCV clearance, baseline HOMA2-IR, and baseline AN were significantly associated with improvement in HOMA2-IR. Thus, the association between HCV clearance and improvement in HOMA2-IR was independent of AN and TNF-α in our cohort.
      Figure thumbnail gr2
      Figure 2Plot of change in AN (x-axis) versus change in HOMA2-IR (y-axis) (week 20 – week 0). A trend toward decreasing HOMA2-IR with increasing AN level is noted (R2 = –0.14), but this did not achieve statistical significance (P = .19).

       Correlation Between HCV Clearance and Reduction in Insulin Resistance Is Not Explained by Confounders

      A number of additional variables were then thoroughly evaluated in an effort to address potential confounding. Initially, univariate associations between HCV clearance and change (week 20 – week 0) in BMI, chemistries, AN, and TNF-α were analyzed, and none achieved statistical significance in our cohort (data not shown). This suggested that these factors were not likely to account for the association between HCV clearance and HOMA2-IR. As expected from our study design with relatively uniform histology, the correlation between degree of fibrosis and HCV clearance was not significant because most had advanced fibrosis. Similarly, the correlation between steatosis at baseline and HCV clearance was not significant. Thus, changes in HOMA2-IR were not attributable to differences in baseline histology. To further reduce the likelihood of confounding, a multivariate model was constructed. On the basis of well-established clinical associations, a model was built in which change in HOMA2-IR (week 20 minus week 0) was predicted from HCV clearance categories while controlling for age, gender, baseline BMI, BMI difference (week 20 – week 0), duration of infection, steatosis, fibrosis, as well as AN and baseline HOMA2-IR. From this model, the variables selected (P ≤ .1) were HCV clearance, baseline HOMA2-IR, baseline AN, and baseline BMI. A final model with only the selected variables showed that, once again, HCV clearance, baseline HOMA2-IR, and baseline AN correlated statistically with change in IR, whereas BMI did not achieve statistical significance in our model. Once the final model was selected, center and center by HCV clearance interaction were entered into the model, but the results remained unchanged because these last 2 variables did not achieve statistical significance. Results from the final multivariate model are summarized in Table 2.
      Table 2Multivariate Regression Model
      VariableEffect on change in HOMA2-IR (week 20 – week 0)P value
      HCV clearanceComplete responders: −2.42.02
      Partial responders: −0.88
      Nonresponders: +0.03
      Baseline HOMA2-IR (10% increment)−0.49<.01
      Baseline AN−0.05.05
      Baseline BMI0.11.14

      Discussion

      Most clinical studies published on the association between HCV and IR have been cross-sectional in nature and confounded by a number of factors. Potential confounders have not been evaluated thoroughly in the literature, and multifactorial models simultaneously analyzing their independent effects have been lacking.
      In this study we found that IR improves with clearance of hepatitis C viremia. Overall, nonresponders exhibited negligible change in HOMA2-IR during the course of HCV therapy, whereas partial and complete responders experienced a reduction in HOMA2-IR levels. An important result of our study was the linear trend noted, whereby HOMA2-IR decreased gradually across the 3 HCV clearance categories. Detailed multivariate analyses did not reveal confounders in the association between HCV and IR. Our findings provide support for a causal role of HCV in the induction of IR. Although this evidence is indirect, it represents the most direct human data to date to address the relationship between HCV and IR.
      In 2005, Romero-Gomez et al
      • Romero-Gomez M.
      • Del Mar Viloria M.
      • Andrade R.J.
      • et al.
      Insulin resistance impairs sustained response rate to peginterferon plus ribavirin in chronic hepatitis C patients.
      found that among 50 patients, HOMA IR decreased during the first 6 months of therapy in those who achieved HCV RNA clearance at 6 months but remained unchanged in patients who did not eradicate viremia. This study included subjects with heterogeneous liver histologies and more than 1 HCV genotype. Kawaguchi et al
      • Kawaguchi T.
      • Ide T.
      • Taniguchi E.
      • et al.
      Clearance of HCV improves insulin resistance, beta-cell function, and hepatic expression of insulin receptor substrate 1 and 2.
      found that HCV clearance improved IR among 89 subjects. Although this was an interesting study, there were a number of limitations. Subjects had mild to moderate fibrosis, and responders had statistically lower levels of fibrosis than relapsers or nonresponders. In addition, baseline IR was not considered in the analysis, subjects underwent different treatment modalities, and change in IR was not evaluated in a single statistical model. Nevertheless, our results are consistent with those of Kawaguchi et al.
      In our cohort we did not find evidence to support a role for AN or TNF-α as possible mediators in the effect of HCV on IR. However, the significant fibrosis of our cohort might have impaired hepatic clearance of adipocytokines,
      • Tietge U.J.
      • Boker K.H.
      • Manns M.P.
      • et al.
      Elevated circulating adiponectin levels in liver cirrhosis are associated with reduced liver function and altered hepatic hemodynamics.
      • Kaser S.
      • Moschen A.
      • Kaser A.
      • et al.
      Circulating adiponectin reflects severity of liver disease but not insulin sensitivity in liver cirrhosis.
      which limits possible interpretability. In addition, the lower AN levels observed among men who represented the majority of our subjects might also limit our findings. Our results suggest that higher baseline AN correlates with improvement in IR independently of HCV clearance. A trend toward an inverse correlation between change in AN and change in IR raises the possibility of a lack of power for this particular analysis. We believe the role of adipocytokines in mediating the effect of HCV on IR merits additional study.
      One potential limitation of our findings is that the effects noted on IR across the different response categories could be interpreted as a result of varying levels of response to the medications themselves. However, it is unlikely that the improvement in IR noted with higher degrees of response to therapy could be secondary to the use of interferon, which would be expected to cause the opposite effect.
      • Kanai F.
      • Omata M.
      Glucose intolerance caused by interferon therapy.
      • Sasaoka T.
      Glucose intolerance induced by interferon therapy.
      The concept that HCV might induce IR in vivo has important clinical consequences. IR and diabetes mellitus lead to a number of serious systemic complications and adversely impact the natural history of HCV and its response to antiviral therapy. On the basis of our findings, improvement of IR might be an added benefit of treatment of HCV infection. In addition, early identification and management of IR should have beneficial health effects overall and would be expected to have a positive impact on HCV liver disease, although further prospective studies will be required to support this premise.
      In summary, our results demonstrate a correlation between clearance of HCV RNA levels and improvement of IR. These findings provide additional in vivo support for a causal role of HCV in the development of IR. Further study will be necessary to clarify the mechanisms of HCV-associated IR and to evaluate the effects of early identification and management of IR in HCV infection.

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