Metabolic impairment is one of the characteristics of chronic hepatitis C virus (HCV) infection. Patients frequently develop diabetes mellitus through insulin resistance and altered glucose regulation, possibly as a sequel to abnormal lipid accumulation in cells and ongoing liver inflammation. Successful clinical treatment reverses all three conditions. This has been well documented previously through serum biochemistry and sequential histopathology of liver biopsies during recovery.
Babudieri et al.1 present a case study following a 28-year-old woman through treatment and clinical recovery from chronic HCV infection. Proteins were extracted from formalin-fixed, paraffin-embedded (FFPE) biopsies taken pre- and post-treatment. Proteomic analysis showed “real time” recovery of enzyme pathways coinciding with treatment and resulting eradication of the HCV infection.
Following numerous relapses and inflammatory flare-ups, the patient started antivirals, insulin and oral hypoglycaemic therapy, along with clinical/psychological support for alcoholism. Liver biopsies and serum samples taken before treatment confirmed active HCV infection with its attendant metabolic impairments and hepatic tissue damage. Within four weeks, HCV-RNA was not detected and glycaemic control had improved. After seven months, biochemical markers had returned to normal. With treatment, hepatic tissue structure normalized, as shown in a liver biopsy at three months post-treatment. These improvements were mirrored by changes in tissue proteomics.
Using liver biopsies obtained before and after treatment, researchers extracted full-length proteins from FFPE samples. Protein extracts were separated by 4–20% gradient polyacrylamide gel electrophoresis, then extracted by in-gel trypsin digest before analysis by LC-MS/MS on a Q-TOF hybrid mass spectrometer coupled on-line with a capillary chromatography system. Protein abundance was measured using label-free quantification by spectral counting, then analyzed qualitatively and quantitatively using Proteome Discoverer (version 1.3, Thermo Scientific). The differences in concentration between samples were calculated using the spectral counts log ratio for proteins that were the same, and the Normalized Spectral Abundance Factor for different proteins.
Forty of the 404 proteins identified in the tissue extracts changed levels with treatment, and included 16 enzymes. Enzymes involved in amino acid synthesis decreased with treatment, whereas those involved with lysosomal pathways increased. Other proteins showing changes in concentration pre- and post-treatment were those associated with amino acid, lipid and glucose metabolic pathways, all of which improved clinically during therapy. Another finding that correlated well with clinical recovery and HCV eradication was upregulation of proteins associated with protecting cells from oxidative stress.
Although monitoring metabolic recovery with treatment is not new for HCV infection, the authors suggest that use of their wider proteomic analysis shows the overall picture of recovery rather than changes in single metabolic pathways. They acknowledge the limitations of studying only one subject, but note that proteomic analysis during recovery from HCV has not previously been investigated. Their results illustrate how enzymatic pathways and hepatic function normalize with HCV eradication and are consistent with biochemical indicators of returning health.
1. Babudieri, S., et al. (2013) “Proteomic characterization of hepatitis C eradication: Enzyme switch in the healing liver,” Journal of Clinical Virology, 57 (pp. 274–278).
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