OVEREXPRESSION OF GLUCOSE TRANSPORTERS IN RAT MESANGIAL CELLS CULTURED IN A NORMAL GLUCOSE MILIEU MIMICS THE DIABETIC PHENOTYPE

An environment of high glucose concentration stimulates the synthesis of extracellular matrix (ECM) in mesangial cell (MC) cultures, This ma y result from a similar increase in intracellular glucose concentratio n, We theorized that increased uptake, rather than glucose concentrati on per se is the major determinant of exaggerated ECM formation, To te st this, we compared the effects of 35 mM glucose on ECM synthesis in normal MCs with those of 8 mM glucose in the same cells overexpressing the glucose transporter GLUT1 (MCGT1). Increasing medium glucose from 8 to 35 mM caused normal MCs to increase total collagen synthesis and catabolism, with a net 81-90% increase in accumulation, MCs transduce d with the human GLUT1 gene (MCGT1) grown in 8 mM glucose had a 10-fol d greater GLUT1 protein expression and a 1.9, 2.1, and 2.5-fold increa se in cell myo-inositol, lactate production, and cell sorbitol content , respectively, as compared to control MCs transduced with bacterial b eta-galactosidase (MCLacZ). MCGT1 also demonstrated increased glucose uptake (5-fold) and increased net utilization (43-fold), and greater s ynthesis of individual ECM components than MCLacZ. In addition, total collagen synthesis and catabolism were also enhanced with a net collag en accumulation 111-118% greater than controls, Thus, glucose transpor t activity is an important modulator of ECM formation by MCs; the pres ence of high extracellular glucose concentrations is not necessarily r equired for the stimulation of matrix synthesis.