Improvement of insulin resistance by Hon-Chi in fructose-rich chow-fed rats

In an attempt to develop new substances for handling insulin resistance, the effect Hon-Chi was examined on insulin resistance induced by fructose-rich chow in rats. Mandarin Hon-Chi is red yeast rice fermented with Monascus pilous and Monascus purpureus. Single oral administration of Hon-Chi for 90 min decreased the plasma glucose in a dose-dependent manner in rats, which had received four-week fructose-rich chow. The insulin action on glucose disposal rate using the glucose-insulin index, and the value of the areas under the curve of glucose and insulin during the intraperitoneal glucose tolerance test were measured. Oral administration (three times daily for three-days) of Hon-Chi into rats, which received four-week fructose-rich chow, reversed the elevated value of glucose-insulin index, indicating Hon-Chi has an ability to improve insulin resistance. The time for the loss of plasma glucose lowering response to tolbutamide in fructose-rich chow-fed rats was markedly delayed by the repeated treatment of Hon-Chi, as compared to the vehicle-treated group. This provided the supportive data that oral administration of Hon-Chi could delay the development of insulin resistance in rats. Increase of insulin sensitivity by Hon-Chi was further identified using the plasma glucose lowering action of exogenous insulin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Oral administration of Hon-Chi at 150 mg/kg three times daily into STZ-diabetic rats caused an increase in the responses to exogenous insulin 15-days later. The obtained results suggest that oral administration of Hon-Chi has the ability to improve insulin sensitivity and delay the development of insulin resistance in rats, which may be used as an adjuvant therapy to patients with insulin resistance.