Insulin regulates the expression of adiponectin and adiponectin receptors in porcine adipocytes

Adiponectin is an adipocyte-derived hormone that can improve insulin sensitivity. Its functions in regulating glucose utilization and fatty acid metabolism in mammals are mediated by two subtypes of adiponectin receptors (AdipoR1 and AdipoR2). This study was conducted to determine the effect of insulin on the expression of adiponectin and its receptors. We demonstrated that in the presence of 10nM insulin, addition of 1 mu M of insulin or rosiglitazone (a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist) had no effect on the expression of adiponectin and AdipoR genes in differentiated porcine adipocytes. However, the addition of 1 mu M insulin plus 1 mu M rosiglitazone significantly increased the AdipoR2 mRNA in differentiated porcine adipocytes. Using the phosphatidylinositol 3-kinase inhibitor (PI3K inhibitor, LY 294002), we found that insulin inhibited the expression of AdipoR2 through the PI3K pathway and this inhibition was blocked by addition of rosiglitazone. When porcine adipocytes were cultured without insulin, supplementation with 10 nM insulin inhibited the expression of AdipoR2 and this inhibition effect was also blocked by addition of rosiglitazone. Therefore, these data suggest that a PPAR-gamma agonist increases expression of AdipoR2 and that insulin inhibits the expression of AdipoR2 through the PI3K pathway. (c) 2007 Elsevier Inc. All rights reserved.