Changes in insulin receptor tyrosine kinase activity associated with metformin treatment of type 2 diabetes

This study was performed to define the effect of metformin on glycaemic control and erythrocyte insulin receptor tyrosine kinase activity in patients with non-insulin-dependent (Type 2) diabetes mellitus. A case-control study of the effect of metformin treatment in hyperglycaemic patients with Type 2 diabetes was conducted in outpatients of the Diabetes Clinical Center. The study population consisted of 14 patients with Type 2 diabetes (5 males, 9 females) whose hyperglycaemia was uncontrolled by diet. Patients were treated with metformin 850 mg twice daily for 2 1/2 months. Fasting plasma glucose concentrations decreased from 8.9 to 6.4 mmol/L after 10 weeks of metformin treatment (p < 0.001), in association with significantly lower (p < 0.001) plasma glucose and insulin concentrations in response to an oral glucose load. In addition, both fasting plasma triglyceride and cholesterol concentrations were significantly (p < 0.001) lower after metformin treatment. There was no change in erythrocyte insulin receptor binding associated with metformin treatment, but both basal and insulin-stimulated insulin receptor tyrosine kinase activities of solubilized erythrocyte insulin receptors were significantly higher after 10 weeks of metformin treatment. It is concluded that the increase in insulin-stimulated tyrosine kinase activity contributed to the improvement in glucose insulin and lipoprotein metabolism associated with metformin treatment of Type 2 diabetes.