The novel hypoglycemic agent YM440 improves hepatic insulin resistance in obese Zucker fatty rats

The novel hypoglycemic agent YM440 ((Z)-1,4-bis{4-[(3,5-dioxo-1,2,4-oxadiazolidin-2-yl)methyl] phenoxy}but-2-ene) is a ligand of the peroxisome proliferator-activated receptor (PPAR) gamma. YM440 has unique pharmacological profiles both in vitro and in vivo, but, it is not clear whether the compound has a significant effect on hepatic or peripheral insulin response throughout the body. The aim of this study is to examine the effects of YM440 on hepatic and peripheral insulin resistance in Zucker fatty (ZF) rats using the euglycemic-hyperinsulinaemic clamp technique. Treatment of ZF rats with YM440 (300 mg/kg per day) for 2 weeks significantly decreased plasma concentrations of glucose and insulin without inducing obesity. YM440 caused a 2-fold increase in the glucose infusion rate during euglycemic clamping compared with the vehicle control. YM440 also decreased the percent change in hepatic glucose production rate caused by intravenous insulin infusion in ZF rats. YM440 had no significant effect on the glucose disposal rate. These results indicate that YM440 ameliorates hepatic, but not peripheral insulin resistance in ZF rats. These findings strongly suggest that the main target organ of YM440 is the liver, unlike other PPARgamma agonist.