Comparison of blood monocytes and adipose tissue macrophages in a mouse model diet-induced weight gain

Diet-induced weight gain causes changes in adipose tissue that alter blood monocytes and adipose tissue macrophages, increasing disease risk. The purpose of this study was to compare the effects of 24 wk of diet-induced weight gain on the percentages of blood monocytes and adipose tissue macrophages as well as the cell-surface expression of toll-like receptors 2 and 4 and leptin receptor, which are associated with inflammation and homing to adipose tissue. Crl:CD1(ICR) male mice were assigned to either a diet-induced weight gain (60% of calories from fat; n = 12) or control (10% of calories from fat; n = 13) group. After 24 wk of dietary treatment, whole blood and bilateral perigonadal fat pads were collected. Whole blood or SVF were separately labeled for monocytes (CD11b⁺CD14-) or macrophages (CD11b⁺F4/80 ⁺) and receptor expression by using 3-color flow cytometry. Data were analyzed by using univariate ANOVA. Compared with control mice, those in the weight-gain group had greater body weight, fat mass, and percentages of monocytes and macrophages compared with CN. Regardless of cell type, monocytes and macrophages from mice in the weight-gain group expressed significantly less toll-like receptor 2 and leptin receptor than did control mice. The present study demonstrates that monocytes and macrophages are similarly affected by diet-induced weight gain. More research is needed to confirm how monocytes might be used as a proxy measure of macrophages.