Improvement of insulin resistance by Acanthopanax senticosus root in fructose-rich chow-fed rats.

1. In an attempt to develop new substances for handling insulin resistance, an aqueous extract of the root of Acanthopanax senticosus (Araliaceae) was used to screen the effect on insulin resistance induced by fructose-rich chow in rats. 2. Insulin action on glucose disposal rate was measured using the glucose-insulin index, the product from areas under the curve of glucose and insulin during the intraperitoneal glucose tolerance test. In addition to the modification of feeding behaviour and a marked decrease in bodyweight, oral administration (three times daily for 3 days) of the aqueous extract of A. senticosus root to rats that had received fructose-rich chow for 4 weeks reversed the elevated value of the glucose--insulin index, indicating that this herb has the ability to improve insulin sensitivity. 3. Time for the loss of the plasma glucose-lowering response to tolbutamide (10.0 mg/kg, i.p.) in fructose-rich chow-fed rats was markedly delayed by repeated treatment with the aqueous extract of A. senticosus root compared with the vehicle (saline) -treated group. Thus, an improving effect of A. senticosus root on insulin resistance can be considered. 4. An increase in insulin sensitivity following the administration of this herb was further identified using the plasma glucose-lowering action of exogenous insulin in streptozotocin (STZ)-diabetic rats. Oral administration of the aqueous extract of A. senticosus root at a dose of 150.0 mg/kg three times daily to STZ-diabetic rats increased the responses to exogenous insulin 10 days later. 5. The results obtained suggest that oral administration of the aqueous extract from A. senticosus root has the ability to improve insulin sensitivity and delay the development of insulin resistance in rats and, thus, may be used as an adjuvant therapy for patients with insulin resistance.