FIG. 5.

Differential effects of M1 and M2a macrophages on adipocyte insulin sensitivity and adipogenesis. A: Conditioned medium (CM) from M1 but not M2a macrophages blocks insulin-stimulated glucose uptake. Differentiated 3T3-L1 adipocytes were treated with conditioned media from macrophages treated with vehicle, LPS (10 ng/ml), or IL-4 (10 ng/ml) for 12 h and assayed for insulin-stimulated 2-DG uptake, demonstrating selective inhibition with LPS conditioned medium. No effects on glucose uptake were seen with LPS or IL-4 treatment alone. n = 3 per group. Values are expressed as means ± SE. *P < 0.05. B: Conditioned medium from M1 but not M2a macrophages blocks adipogenesis. Conditioned medium from treated macrophages was added during differentiation of 3T3-L1 adipocytes at different percentages by volume, and cells were stained with Oil-Red-O, demonstrating that M2a macrophages are permissive toward adipogenesis in contrast to M1 macrophages. Similar results were from three experiments, and a representative experiment is shown. C: Downregulation of GLUT4 and insulin receptor (IR) expression with M1 conditioned medium but not M2a or unstimulated macrophage conditioned medium during adipogenesis. Immunoblots of lysates from 3T3-L1 cells treated with conditioned media during differentiation. (Please see http://dx.doi.org/10.2337/db08-0872 for a high-quality digital representation of this figure.)