JTT-608 controls blood glucose by enhancement of glucose-stimulated insulin secretion in normal and diabetes mellitus rats

We investigated the pharmacological effects of a new anti-hyperglycemic agent, JTT-608 [ trans-4-(4-methylcyclohexyl)-4-oxobutyric acid], in normal and neonatally streptozotocin-treated rats. In normal rats, JTT-608 improved glucose tolerance at 3–30 mg/kg, doses that did not cause a decrease in fasting blood glucose levels. In contrast, tolbutamide (10–100 mg/kg) and glibenclamide (1–3 mg/kg) caused a persistent decrease in fasting blood glucose levels, and tolbutamide only improved glucose tolerance at 10–100 mg/kg. Furthermore, JTT-608 (3–30 mg/kg) enhanced insulin secretion only with glucose stimulation, but tolbutamide (10–100 mg/kg) enhanced it both with and without glucose stimulation. In neonatally streptozotocin-treated rats, JTT-608 (10–100 mg/kg) improved glucose tolerance with enhanced insulin secretion in the oral glucose tolerance test and meal tolerance test. Additionally, JTT-608 improved glucose tolerance dose dependently, but the effect of tolbutamide reached a plateau. We conclude that JTT-608 is an enhancer of glucose-stimulated insulin secretion.