Although the human liver diseases that are associated with MDB formation are clearly defined,1,19
the significance of MDBs and whether they represent a benign epiphenomenon of hepatocyte injury or a modifier of liver disease progression is not known. Animal models indicate that MDB formation has a strong genetic component and is associated with oxidative stress, resulting in sequestration of misfolded proteins.1–4
Several human studies have suggested that MDBs relate to disease severity and poor outcomes in other chronic liver diseases such as alcoholic liver disease and nonalcoholic steatohepatitis.20–22
In evaluation of >1000 patients with chronic hepatitis C, this study furthers our knowledge by demonstrating that MDBs are independently associated with fibrosis progression and that development of MDBs over time is highly associated with clinical decompensation and progression to cirrhosis.
Interestingly, insulin resistance was significantly associated with presence of MDBs and development of MDBs over time. Specifically, MDBs on baseline biopsy were associated with the presence of diabetes as well as higher BMI, HOMA-IR, steatosis grade, and zone-3 pericellular fibrosis stage. Moreover, the presence of diabetes was associated with MDB gain (OR 2.28, p=0.006), whilst the absence of diabetes was associated with MDB loss (OR 5.21, p=0.024). In light of these associations, CHC patients with MDBs may have also had concurrent nonalcoholic steatohepatitis (NASH). However, after controlling for several of the histologic features of NASH such as steatosis and fibrosis, the presence of MDBs remained associated with histological progression, suggesting that MDBs may offer additional prognostic information independent of its association with NASH.
The prevalence of NASH in patients with CHC is reported to be 9–18%,23,24
which corresponds to the 15% prevalence of MDBs on baseline biopsy found in our study. Similar to our findings, CHC with concurrent NASH has been associated with higher fibrosis stages, suggesting that NASH may hasten fibrosis progression in patients with CHC.24
Using the HALT-C cohort, Everhart et al. showed that factors associated with insulin resistance were associated with clinical and histological outcomes.16
Our study expands upon this with a longer duration of follow-up (from 3.8 to 8.7 years), thereby allowing a greater number of clinical outcomes. Additionally, our analysis assessed clinical and histological outcomes as separate primary endpoints, with clinical outcomes further evaluated with and without HCC. Taken together, our findings further support the growing evidence that CHC with concomitant NASH features is associated with worse outcomes compared to CHC alone.
In longitudinal analysis, MDB gain was associated with clinical and histological outcomes. The converse, however, was not found to be true (i.e. those with MDB loss did not have improved outcomes). This may be due to smaller numbers or may reflect that the MDBs seen on initial biopsy heralded the coexistence of NASH in these patients. Although MDBs were no longer present on follow-up biopsy, it is unlikely that NASH had regressed and therefore may explain the lack of improved outcomes seen in this group. Other potential explanations include a liver biopsy sampling error or hitherto unknown environmental/genetic factors that might lead to MDB resolution.
Though not significantly associated with MDB presence on baseline biopsy, female gender was associated with MDB gain, suggesting that factors such as genetics4
are likely important. Multivariate analysis showed that Hispanics are more likely to demonstrate MDB gain (), though the small number of Hispanics and the known association between Hispanic ethnicity and metabolic factors warrants independent verification.
In evaluating the prognostic role of MDBs, the HALT-C trial offered several advantages including a prospective follow-up of a large cohort of patients, a range of races/ethnicities, and longitudinal data on alcohol consumption and metabolic factors. Most importantly, serial biopsies were available, all reviewed by expert hepatopathologists. However, the HALT-C cohort does have some limitations with regard to assessing MDBs. First, it is possible that MDBs that were present but not prominent may have been scored as absent. Though immunohistochemical (ubiquitin or K8/18) staining would have improved detection and reproducibility of finding MDBs, such staining was not part of the initial HALT-C analysis due to time and cost constraints. Sampling error of smaller biopsies may have influenced analysis of MDBs over time, as evidenced by smaller baseline biopsies in subjects with MDB gain and smaller follow-up biopsies in those with MDB loss. However, the overall differences in biopsy size are small despite being statistically different. The longitudinal analysis of histological outcome in patients with MDB loss may have been limited due to small numbers (n=53), with 5 patients showing no MDB loss () though all other analyses are largely robust with much larger sample sizes. The HALT-C trial enrolled only patients with advanced histological disease (Ishak fibrosis stage ≥3), therefore our findings may not apply to patients with early-stage fibrosis. Similarly, all patients were previous non-responders to interferon therapy and half of the patients underwent maintenance interferon treatment, which may restrict generalization of the results to all patients with CHC. The large proportion of patients with high BMI (mean=29.9±5.5) and diabetes (24.1%) may also have contributed to our findings, though this trend reflects the known association between non-response to CHC treatment and traits such as obesity and diabetes.
In conclusion, MDBs were highly associated with markers of insulin resistance as well as independently associated with fibrosis progression in patients with CHC, which could be attributed to hastened fibrosis progression from coexistent NASH. In longitudinal analysis, patients with underlying diabetes appear to be at greatest risk of developing MDBs on follow-up biopsy, which was found to be associated with clinical outcomes as well as fibrosis progression. Therefore, assessment of MDBs in liver biopsies of patients with CHC appears to offer prognostic significance. Further studies with a broader spectrum of disease severity and in patients with other chronic liver diseases are warranted to further delineate the potential pathogenic factors and clinical implications of MDB assessment.