Cellular glucose transport and glucotransporter 4 expression as a therapeutic target: clinical and experimental studies

Abstract

The normalization of cellular glucose assimilation is the basic aim of metabolic therapy in type 2 diabetes mellitus (T2DM). It requires parallel changes in the process of cellular glucose transport (CGT). Therefore the level of CGT could be regarded as a therapeutic target for oral hypoglycemic drugs in T2DM. To explore this hypothesis, CGT levels before and after sulfonylurea therapy were investigated. Peripheral blood lymphocytes were used as a cell model for testing CGT. CGT was assessed by experimental in vitro tests allowing timed comparative observation of the transport process during the incubation of lymphocytes with 2-[(3)H(G)] glucose under basal conditions and after the addition of sulfonylurea or sulfonylurea plus insulin. The incubation tests were performed at baseline in 28 persons with newly diagnosed, therapy-naive T2DM and in 20 control subjects. In the diabetic patients the tests for CGT were repeated after 3 months of sulfonylurea therapy. The level of glucotransporter 4 (GLUT4) expression was also assessed by flow cytometry before and after the therapy. Before treatment, CGT was significantly lower in the subjects with T2DM. The cells responded to the addition of sulfonylurea by a moderate increase in CGT. This response was augmented by the addition of insulin to sulfonylurea in the culture medium. The three-month therapy with sulfonylurea resulted in a significant increase in CGT in all types of culture tests. This sulfonylurea-related improvement in CGT was associated with a near normalization of GLUT4 expression in the cells.