Effect of Mongolian plants on in vivo insulin action in diabetic rats

In the present study, we firstly performed a preliminary investigation on the acute effect of Mongolian medicinal plant extracts (Dryopteris species, Aspidiaceae) on the glucose tolerance in rats, evaluated by an oral glucose tolerance test (OGTT). Then, we investigated the effect of the same extracts on in vivo insulin action in streptozotocin (50 mg kg(-1) BW, i.v.)-induced diabetic rats by means of the euglycemic clamp. In diabetic rats, the glucose metabolic clearance rate (MCR) during 3.0 (low-dose) and 30.0 mU kg(-1)min(-1) (high-dose) insulin infusion was significantly higher in animals administered with plant extracts (500 mg kg(-1) BW, p.o.), compared with saline-administered animals (low-dose--normal control: 16.3+/-0.7 ml kg(-1)min(-1) versus plant extract 1: 15.8+/-0.6 ml kg(-1)min(-1) and plant extract 2: 14.0+/-0.5 ml kg(-1)min(-1), diabetic control: 10.9+/-0.6 ml kg(-1)min(-1) versus plant extract 1: 19.3+/-1.4 ml kg(-1)min(-1) and plant extract 2: 20.5+/-1.5 ml kg(-1)min(-1); high-dose-normal control: 50.9+/-2.6 ml kg(-1)min(-1) versus plant extract 1: 49.8+/-2.6 ml kg(-1)min(-1) and plant extract 2: 48.4+/-2.4 ml kg(-1)min(-1), diabetic control: 26.9+/-1.6 ml kg(-1)min(-1) versus plant extract 1: 33.5+/-1.7 ml kg(-1)min(-1) and plant extract 2: 37.2+/-1.9 ml kg(-1)min(-1); P<0.05, respectively). These results suggest that a single administration of the two Mongolian plant extracts can improve glucose utilization and insulin resistance in diabetic rats.