Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites produced by 
cytochrome P450 epoxygenases which are highly expressed in hepatocytes. The 
functions of EETs in hepatocytes are not well understood. In this study, we 
investigated the effects of 14,15-EETs treatment on the insulin signal 
transduction pathway in hepatocytes. We report that chronic treatment, not acute 
treatment, with 30 μM 14,15-EETs prevents palmitate induced insulin resistance 
and potentiates insulin action in cultured HepG2 hepatocytes. 14,15-EETs 
increase Akt phosphorylation at S473, activating Akt, in an insulin dependent 
manner in HepG2 cells. Under insulin resistant conditions induced by palmitate, 
14,15-EETs restore the insulin response by increasing S473-phosphorylated Akt. 
8,9-EETs and 11,12-EETs demonstrated similar effects to 14,15-EETs. Furthermore, 
14,15-EETs potentiate insulin-suppression of gluconeogenesis in cultured H4IIE 
hepatocytes. To elucidate the mechanism of EETs function, we analyzed the 
insulin signaling factors upstream of Akt. Inhibition of phosphatidylinositol 
3-kinase (PI3K) with LY294002 attenuated the 14,15-EETs-induced activating 
phosphorylation of Akt. 14,15-EETs reduced palmitate-stimulated phosphorylation 
of IRS-1 on S312 and phosphorylation of c-Jun N-terminal kinase (JNK) at 
threonine 183 and tyrosine 185 residues. The regulation of insulin sensitivity 
in cultured hepatocytes by chronic 14,15-EETs treatment appears to involve the 
JNK-IRS-PI3K pathway. The requirement of chronic treatment with EETs suggests 
that the effects of EETs on insulin response may be indirect.