Rosiglitazone modulates insulin-induced plasma membrane area changes in single 3T3-L1 adipocytes

In this study we hypothesized that rosiglitazone, an antidiabetic high-affinity agonist for the peroxisome proliferator–activated receptor γ, affects the plasma membrane (PM) turnover in single 3T3-L1 adipocytes. To study the PM turnover, the patch-clamp electrophysiological method was used to measure changes in membrane capacitance (C m), a parameter linearly related to the PM area. Microscopy results show that the presence of rosiglitazone in the differentiating medium significantly increased the differentiation of 3T3-L1 adipocytes in cell culture, based on oil red O–stained area (11.4 ± 1.2%) vs. controls (3.1 ± 0.5%). Moreover, rosiglitazone treatment significantly reduced the size of single 3T3-L1 adipocytes; their average radius of 21.1 ± 1.1 μm in controls was reduced to 17.5 ± 0.5 μm in rosiglitazone-treated cells. Consistent with this, insulin application increased the rate of C m increase to 2.34 ± 0.10%/min, which was significantly different from controls (0.12 ± 0.08%/min). However, pretreatment of cells with rosiglitazone prior to the treatment with insulin resulted in an attenuated rate of C m increase. These data support the involvement of insulin in the modulation of membrane area and show that treatment by rosiglitazone reduced the insulin-mediated membrane area increase in 3T3-L1 adipocytes.