Markers of Macrophage Infiltration and Measures of Lipolysis in Human Abdominal Adipose Tissues

Objective: We tested the hypothesis that high lipolytic responsiveness is related to increased expression of ATM genes in human adipose tissues. Design and Methods: Omental (OM) and subcutaneous (SC) fat samples were obtained surgically in 46 women (age: 47.2 +/- 4.7 years, BMI: 26.9 +/- 5.2 kg/m(2)). Body composition and fat distribution were measured using dual energy X-ray absorptiometry and computed tomography. Lipolysis was measured by glycerol release in mature adipocytes isolated by collagenase digestion under basal-, isoproterenol (10(-5) M)-, and forskolin (10(-5) M)-stimulated conditions. Quantification of macrophage gene mRNA expression (CD11b, CD11c, and CD68) in whole adipose tissue was performed using real-time RT-PCR. Results: SC CD68 mRNA abundance was positively associated with isoproterenol-stimulated lipolysis (r=0.36, P<0.05). This association remained significant after adjustment for total body fat mass (r=0.34, P <= 0.05). In the OM depot, CD11b mRNA abundance was positively associated with isoproterenol-stimulated lipolysis (r=0.42, P <= 0.005). This association remained significant after adjustment for total body fat mass (r=0.41, P <= 0.01). In subgroup analyses, high lipolytic rates in SC adipocytes were related to increased whole tissue expression of CD68 and CD11b in this compartment, independent of adiposity and fat cell size (P <= 0.001 and P <= 0.05). High lipolytic rates in OM adipocytes were related to increased whole tissue OM expression of CD11b, independent of adiposity and fat cell size (P <= 0.05). Conclusions: High adipocyte lipolytic responsiveness is related to increased expression of ATM markers in the corresponding compartment, independent of adiposity and fat cell size.