Insulin and oleic acid increase PPARγ2 expression in cultured mouse hepatocytes

Hepatic PPARγ expression is increased in several animal models of diabetes and obesity, and liver-specific overexpression of PPARγ induces liver steatosis. The aim of this study was to investigate the regulation of PPARγ expression in primary mouse hepatocytes. PPARγ2, but not PPARγ1, was up-regulated by insulin and to a lesser extent by oleic acid. Insulin increased transcription of the PPARγ2 gene via phosphatidylinositol 3-kinase activation. The PPARγ agonist, rosiglitazone, increased PPARγ2 expression, but not PPARγ1, only in the presence of insulin. Also aP2 mRNA expression was induced by rosiglitazone to a higher degree in the presence of insulin, while acyl-CoA oxidase was increased independently of insulin. In summary, PPARγ2 is increased in hepatocytes by oleic acid and insulin. These results may help to understand the regulation of PPARγ expression in liver, which possibly plays a role in the development of liver steatosis.