Effects of Long-Term Administration of Gymnema sylvestre Watery-Extract on Variations of Body Weight, Plasma Glucose, Serum Triglyceride, Total Cholesterol and Insulin in Wistar Fatty Rats

Hikari Terasawa, Michio Miyoshi and Toshiaki Imoto

First Department of Physiology, Faculty of Medicine, Tottori University, Yonago 683, Japan

Gymnemic acid compounds suppress the sweet taste sensation in man. Recently, this substance has been found to inhibit glucose absorption in the small intestines of rats, and to reduce the plasma glucose increment in oral sucrose tolerance test (OSTT). Most of these reports, however, were based on short-term observation results. In the present study, the long-term application of watery-extract substances from Gymnema sylvestre leaves (GSW) was performed over a 21-week period. The effect on body weight, glucose absorption and lipid metabolism was examined by using Wistar fatty rats with genetic obese-hyperglycemia. Body weight at 30 weeks of age had dropped by 4.21% and 6.13% in fatty and lean rats fed with a high-carbohydrate low-fat (HCLF) diet plus GSW (experiment), as compared with rats fed with an HCLF diet (control). The plasma glucose level of 162.5 mg/dL (control) at 30 weeks of age dropped to a level of 133.5 mg/dL (experiment). Plasma glucose increase in OSTT was almost normalized in the experimental group without alteration of serum insulin levels. Although hypertriglyceridemia was also improved in the experimental group, Iittle change in hypercholesteremia was observed.

Key words: genetic obesity; Gymnema sylvestre watery-extract; gymnemic acid; oral sucrose tolerance test; Wistar fatty rat

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