Effect of Various Radical Generators on Insulin-Dependent Regulation of Hepatic Gene Expression

Oxidative stress is recognized to be associated with the development of insulin resistance. Although free radicals are generated in various ways in vivo, very few radical generators have been used to investigate the effect of oxidative stress on cellular insulin signaling. In order to compare the effect of radical generators with different sites and durations of radical formation on liver insulin action, primary cultured rat hepatocytes were incubated with radical generators and insulin-dependent regulation of gene expression was examined. The hydrophobic 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) radical and H2O2 increased plasma membrane damage, and the hydrophilic 2-2'-azobis(2-amidinopropane) dihydrochloride (AAPH) radical and buthionine sulfoxyimine (BSO) increased oxidation of intracellular substances. Paraquat (PQ) and H2O2 inhibited insulin-dependent repression of insulin-like growth factor-binding protein-1 (IGFBP-1) and phosphoenolpyruvate carboxykinase (PEPCK) gene expression. These results indicate that PQ and H2O2 impair insulin action effectively and are suitable for examining crosstalk between oxidative stress and insulin signaling in liver-cell culture systems.