Plasma glucose lowering action of stevioside and hon-chi in Wistar rats

• Main Authors: Chang, Jui-Chang, 張瑞璋
• Other Authors: Wu, Ming-Chang, Ph.D.
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/11204929803370616223

博士 === 國立屏東科技大學 === 食品科學系 === 94 === Stevioside, a glycoside contained in the leaves of Stevia rebaudiana Bertoni (Compositae) used as popular sweetner, was employed to screen the effect on insulin resistance of rats induced by a diet containing 60 % fructose. Oral administration of stevioside decreased the plasma glucose concentration in a dose-dependent manner in rats received 4-week fructose-rich chow. In addition, insulin action on glucose disposal rate was measured using the glucose-insulin index, the product of the areas under the curve of glucose and insu- lin during the intraperitoneal glucose tolerance test. Oral administration of stevioside (5.0 mg/kg) into fructose fed rats for 90 min reversed the value of glucose-insulin index, indicating stevioside has the ability to improve insulin sensitivity in this insulin resistant animal model. Time for the loss of plasma glucose lowering response to tolbutamide (10.0 mg/kg, i.p.) in fructose fed rats was also markedly delayed by the repeated oral intake of stevioside three times daily, as compared to the vehicle-treated group. The plasma glucose lowering activity of tolbutamide is introduced to depend on the secretion of endogenous insulin and this is widely used as an indicator of insulin resistance formation. Thus, it provided the supportive data that repeated oral administration of stevioside delayed the development of insulin resistance in high fructose feeding rats. Increase of insulin sensitivity by stevioside was further identified using the plasma glucose lowering action of exogenous insulin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Oral administration of stevioside at 0.2 mg/kg three times daily into STZ-diabetic rats for 10 days made an increase of the responses to exogenous insulin. Taken together, it showed that oral administration of stevioside improves insulin sensitivity and it seems suitable to use as an adjuvant for diabetic patients and/or the subject who consumed large amounts of fructose. In an attempt to develop new substances for handling diabetes, Hon-Chi was employed to screen the antihyperglycemic action in STZ-diabetic rats. The mandarin Hon-Chi is the red yeast rice fermented with Monascus pilous and Monascus purpureus. Oral administration of Hon-Chi decreased the plasma glucose of STZ-diabetic rats in a dose-dependent manner from 50 mg/kg to 350 mg/kg. Similar treatment of Hon-Chi also lowered the plasma glucose in normal rats as effective as that produced in STZ-diabetic rats. In addition, oral administration of Hon-Chi at the highest dose (350 mg/kg) attenuated the elevation of plasma glucose induced by an intravenous glucose challenge test in normal rats. Moreover, the mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) in the liver from STZ-diabetic rats were reversed in a dose-dependent manner by the repeated oral intake of Hon-Chi three times daily for 2 weeks. Otherwise, hyperphagia in STZ-diabetic rats was markedly reversed by similar repeated treatment of Hon-Chi. The obtained results suggest that oral administration of Hon-Chi could decrease hepatic gluconeogenesis to lower plasma glucose in diabetic rats lacking insulin. Thus, it also is suitable to use as an adjuvant for diabetic patients.