Figure 3

Effects of resistin on GLUT4 activity and expression. Adipocytes transduced with the LacZ gene (Control) or with the resistin gene were incubated for 12 days until fully-differentiated. (A) Resistin overexpressing adipocytes show an inhibition of insulin-stimulated glucose transport activity. Control cells (Bars 1 and 2) and cells over-expressing resistin (Bars 3 and 4), were incubated in the absence (Bars 1 and 3) or presence (Bars 2 and 4) of 100 nM insulin for 30 min at 37°C to induce maximal rates of glucose uptake. Double asterisk, P < 0.01 for (Resistin + Insulin) versus (Control + Insulin). (B) Conditioned medium from resistin transduced adipocytes inhibits the activity of insulin-stimulated glucose transport. 3T3-L1 adipocytes treated with conditioned control medium from LacZ transduced cells (control) (Bars 1 and 2) and conditioned medium from resistin transduced cells (Bars 3 and 4), were incubated in the absence (Bars 1 and 3) or presence (Bars 2 and 4) of 100 nM insulin for 30 min at 37°C to induce maximal rates of glucose uptake. Asterisk, P < 0.05 for (Resistin medium + Insulin) versus (Control medium + Insulin). (C) Resistin decreases the gene expression of GLUT4. Expression of glucose transporter GLUT4 gene was examined using a quantitative PCR assay in resistin transduced adipocytes and LacZ transduced adipocytes during their differentiation process as described in the Fig. 2. Results represent the mean ± SE from three separate experiments. Double asterisk, P < 0.01 for resistin versus control at Day 9.