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ENDOCRINE AND DIABETES

Desoxyrhaponticin (3,5-Dihydroxy-4'-methoxystilbene 3-O--D-glucoside) Inhibits Glucose Uptake in the Intestine and Kidney: In Vitro and in Vivo Studies

School of Chinese Medicine (J.M.L., C.T.C.), School of Pharmacy (C.B.S.L.), Department of Physiology (P.S.L.), Department of Biochemistry and Center of Novel Functional Molecules (C.H.K.C.), The Chinese University of Hong Kong, Shatin, Hong Kong, China

Rhubarb extracts have been reported to improve oral glucose tolerance in diabetic animals. In the present study we have investigated the antidiabetic actions of desoxyrhaponticin, a major stilbene in rhubarb, as a glucose uptake inhibitor. Desoxyrhaponticin was demonstrated to inhibit glucose uptake in rabbit intestinal membrane vesicles as well as in rat everted gut sleeves, with IC₅₀ values of 148.3 and 30.9 µM, respectively. Kinetics studies revealed that desoxyrhaponticin is a competitive inhibitor of glucose uptake in both systems. Moreover, desoxyrhaponticin could reduce glucose uptake in the intestinal membrane vesicles of both normal and diabetic rats. In addition, glucose uptake in the renal membrane vesicles of both normal and diabetic rats was reduced by desoxyrhaponticin. Under the inhibition of desoxyrhaponticin, uptake of glucose in both the intestinal and renal membrane vesicles of the normal rats was no different from that of the diabetic rats. The IC₅₀ values of the uptake inhibition in the renal membrane vesicles of normal and diabetic rats were 118.8 and 115.7 µM, respectively. In a type 2 diabetic animal model in which rats have been treated with streptozotocin at the neonatal stage, postprandial hyperglycemia was significantly suppressed by oral administration of this compound (300 mg/kg b.wt.). These results suggest that desoxyrhaponticin is an agent that is potentially effective in controlling postprandial hyperglycemia in diabetes. The in vivo antidiabetic action of this compound can be explained, in part at least, by inhibition of glucose transport in the small intestine and inhibition of glucose reabsorption in the kidney.

Address correspondence to: Dr. Christopher H. K. Cheng, Department of Biochemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong. E-mail: chkcheng{at}cuhk.edu.hk