EFFECT OF METFORMIN ON INSULIN-STIMULATED TYROSINE KINASE-ACTIVITY OFERYTHROCYTES FROM OBESE WOMEN WITH NORMAL GLUCOSE-TOLERANCE

The purpose of this study was to document the possible effect of solub ilised erythrocytes on insulin-receptor binding and tyrosine kinase ac tivity after 12 weeks of metformin administration to 13 healthy obese women with no history of diabetes and normal glucose as evaluated by c onventional criteria. Subjects were given metformin 850 mg twice a day for 12 weeks. The results showed that plasma glucose response to an o ral glucose challenge did not change following metformin, but that ins ulin response was significantly lower (p < 0.0001). In addition, both the number of insulin receptors and the tyrosine kinase activity per r eceptor of solubilised erythrocytes were significantly greater followi ng metformin administration. Since both body weight and plasma glucose concentrations were similar before and after treatment, the effect of metformin on insulin-receptor binding and tyrosine kinase activity ap peared to be independent of either of these variables. In summary, ora l administration of metformin led to an increase in tyrosine kinase ac tivity or erythrocyte insulin receptors, suggesting that such action o ccurs in the absence of any significant change in plasma glucose conce ntration.