Actions of Novel Antidiabetic Agent Englitazone in Hyperglycemic Hyperinsulinemic ob/ob Mice

The effects of CP 68722 (racemic englitazone) were examined in ob/ob mice, in adipocytes and soleus muscles from ob/ob mice, and in 3T3-L1 adipocytes. Administration of englitazone at 5–50 mg · kg⁻¹ · day⁻¹ lowered plasma glucose and insulin dose dependently without producing frank hypoglycemia in either the diabetic or nondiabetic lean animals. The glucoselowering effect in ob/ob mice preceded the reduction in hyperinsulinemia. On cessation of drug, plasma insulin returned to untreated levels within 48 h, whereas plasma glucose rose slowly over 5 days. Englitazone (50 mg/kg) for 11 days lowered plasma glucose (22.2 ± 1.4 to 14.0 ± 1.9 mM), insulin (7.57 ± 0.67 to 1.64 ± 0.60 nM), nonesterified fatty acids (1813 ± 86 to 914 ± 88 μM), glycerol (9.20 ± 0.98 to 4.94 ± 0.03 mM), triglycerides (1.99 ± 0.25 to 1.03 ± 0.11 g/L), and cholesterol (6.27 ± 0.96 to 3.87 ± 0.57 mM), but no effects were observed 3 h after a single dose. Basal and insulin-stimulated lipogenesis were enhanced in adipocytes from ob/ob mice treated with 50 mg/kg englitazone for 11 days compared with lipogenesis in cells from vehicle-treated controls. Treatment of ob/ob mice with 50 mg/kg englitazone reversed the defects in insulin-stimulated glycolysis (from [3-³H]glucose) and glycogenesis and basal glucose oxidation (from [1-¹⁴C]glucose) in isolated soleus muscles. Englitazone (30 μM) stimulated 2- deoxy-D-glucose transport in 3T3-L1 adipocytes from 0.37 ± 0.03 to 0.65 ± 0.06 and 1.53 nmol · min⁻¹ · mg⁻¹ protein at 24 and 48 h, respectively. Thus, englitazone has 1) insulinomimetic and insulin-enhancing actions in vitro and 2) glucose-, insulin-, triglyceride-, and cholesterol-lowering properties in an animal model of non-insulin-dependent diabetes mellitus (NIDDM) in which sulfonylureas have little or no effect. Thus, this new agent may have beneficial effects including a reduced risk of hypoglycemia in patients with NIDDM.