Fig. 1.
Macrophage infiltration of skeletal muscle in obesity and its association to body mass index (BMI) and insulin sensitivity (SI). A: CD68 staining of skeletal muscle from a representative obese subject. B: CD68 staining of skeletal muscle from a representative lean subject. Human skeletal samples were sectioned and stained with antibody to CD68 as described in materials and methods. Positive cells are indicated by arrows. C: quantification of macrophage CD68 staining in the lean (n = 8) and obese (n = 8) groups, normalized to the number of fibers and expressed as macrophage content in muscle biopsy (% of muscle fibers, left) and also as macrophages per mm2 cross-sectional area of muscle (right). Data are means ± SE. *P < 0.01 vs. lean. D and E: correlations between macrophage content in muscle biopsy (% of muscle fibers) and BMI (D) and SI (E). SI was determined by the frequently sampled intravenous glucose tolerance test method as described in materials and methods. Macrophage content in muscle biopsy is plotted against BMI (n = 16) and against the natural log of SI (n = 16).