Hepatoprotective effect of oleuropein in mice: Mechanisms uncovered by gene expression profiling

Oleuropein, an active constituent of olive leaf, has a variety of pharmacological activities associated with its capacity to scavenge reactive oxygen species. Oleuropein is also reported to have protective effects against non-alcoholic fatty liver disease (NAFLD) in vivo. In this study, gene expression profiling of hepatic tissues was examined, and transcription factors (TFs) with target genes that were modulated by oleuropein were identified to gain insights into the molecular mechanisms for the hepatoprotective action of this compound. C57BL/6N mice were fed either a high-fat diet (HFD) or 0.03% oleuropein-supplemented HFD for 10 weeks, after which their livers were subjected to oligo DNA microarray analysis. The oleuropein with which the HFD was supplemented reduced the hepatic mRNA level of the genes that encoded the key regulators of the hepatic fatty acid uptake and transport. In addition, the oleuropein reduced the expression of a number of hepatic genes involved in the oxidative stress responses and detoxification of lipid peroxidation products and proinflammatory cytokine genes. The (putative) candidate TFs that bound to the promoters of the genes regulated at least threefold (both up and down) by oleuropein were implicated in the lipogenesis, inflammation, insulin resistance, fibrosis, and cell proliferation and differentiation, which implies that the mechanisms that underlie the beneficial effects of oleuropein on NAFLD may be multifactorial.