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.