Insulin resistance and hepatitis C.
Insulin resistance is the major feature of the metabolic syndrome and depends on insulin secretion and insulin sensitivity. In chronic hepatitis C, insulin resistance and type 2 diabetes mellitus are more often seen than in healthy controls or chronic hepatitis B patients. Hepatitis C virus (HCV) infection promotes insulin resistance, mainly by increased TNF production together with enhancement of suppressor of cytokine (SOC-3); both events block PI3K and Akt phosphorylation. Two types of insulin resistance could be found in chronic hepatitis C patients: "viral" and "metabolic" insulin resistance. Insulin resistance in chronic hepatitis C is relevant because it promotes steatosis and fibrosis. The mechanisms by which insulin resistance promotes fibrosis progression include: (1) steatosis, (2) hyperleptinemia, (3) increased TNF production, (4) impaired expression of PPARgamma receptors. Lastly, insulin resistance has been found as a common denominator in patients difficult-to-treat like cirrhotics, overweight, HIV coinfected and Afro-American. Insulin resistance together with fibrosis and genotype has been found to be independently associated with impaired response rate to peginterferon plus ribavirin. Indeed, in genotype 1, the sustained response rate was twice (60%) in patients with HOMA < or = 2 than patients with HOMA > 2. In experiments carried out on Huh-7 cells transfected by full length HCVRNA, interferon alpha blocks HCV replication. However, when insulin (at doses of 128 microU/mL, similar that seen in the hyperinsulinemic state) was added to interferon, the ability to block HCV replication disappeared, and the PKR synthesis was abolished. In summary, hepatitis C promotes insulin resistance and insulin resistance induces interferon resistance, steatosis and fibrosis progression.
Romero-Gómez
Manuel
M
Unit for The Clinical Management of Digestive Diseases. Hospital Universitario de Valme. Ctra de Cadiz s/n. Sevilla 41014, Spain. mromerog@supercable.es
D000998:Antiviral Agents / Q000627:therapeutic use; D019698:Hepatitis C, Chronic / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D007328:Insulin / Q000502:physiology*; D007333:Insulin Resistance / Q000502:physiology*; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000627:therapeutic use; D011092:Polyethylene Glycols / Q000627:therapeutic use; D011994:Recombinant Proteins; D012254:Ribavirin / Q000627:therapeutic use
D000998:Antiviral Agents; D007328:Insulin; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D011994:Recombinant Proteins; D011092:Polyethylene Glycols; D012254:Ribavirin; C100416:peginterferon alfa-2a