Sex differences in insulin action on glucose transport and transporters in human omental adipocytes

We examined the effects of insulin on glucose transport and subcellular glucose transporter distribution in isolated omental adipose cells from men and women. 3-O-Methylglucose transport was measured in intact cells, and the number of glucose transporters in plasma membranes and low density microsomal membranes was determined using the cytochalasin B binding assay. Compared to adipocytes from women, omental adipocytes from men were characterized by 1) 2-fold larger cell volume; 2) 4- to 5- and 2.5-fold higher glucose transport rates when calculated per cell or per cell surface area, respectively, in either basal or insulin-stimulated cells; 3) similar 2-fold insulin stimulating effect per se; and 4) equal concentrations of transporters in both fractions examined, but a 2-fold increase in their total number per cell. Additionally, although not directly measured, the calculated glucose transporter activity in basal plasma membranes prepared from adipocytes from men was 2.7-fold higher than that in women, and insulin further induced a 30% increase in that activity. Thus, a sex-related difference was found between the number of glucose transporters per cell and the resultant glucose transport activity of the intact cells. Together with the increased specific activity of glucose transporters in men compared to women, our findings indicate a sex-related difference in adipocyte glucose transport, mainly due to an increase in the number and modulation of the intrinsic activity of glucose transporters in the plasma membrane.