Circulating IL-6 concentrations and abdominal adipocyte isoproterenol-stimulated lipolysis in women

Objective: To examine the association of plasma interleukin‐6 (IL‐6) concentrations with adiposity and fat cell metabolism in women. Methods and Procedures: Omental (OM) and subcutaneous (SC) adipose tissue samples were obtained from 48 healthy women (age: 47 ± 5 years, BMI: 26.9 ± 5.3 kg/m²) undergoing gynecological surgeries. Total and visceral adiposity were assessed by dual‐energy X‐ray absorptiometry and computed tomography, respectively. Measures of adipocyte lipolysis (basal, isoproterenol‐, forskolin‐, and cyclic dibutyryl‐adenosine monophosphate (AMP)‐stimulated) and adipose tissue lipoprotein lipase (LPL) activity were obtained. Plasma IL‐6 was measured by radioimmunoassay. Results: Plasma IL‐6 was positively correlated with total body fat mass (r = 0.32, P < 0.05), SC adipose tissue area (r = 0.35, P < 0.05), SC adipocyte diameter (r = 0.30, P < 0.05), and a trend was observed with visceral adipose tissue area (r = 0.20, P < 0.07). Plasma IL‐6 was positively correlated with glycerol released in response to isoproterenol (10^?5 to 10^?8 mol/l) by isolated SC (0.31 ≤ r ≤ 0.65, P < 0.05) and OM (0.36 ≤ r ≤ 0.40, P < 0.02) adipocytes, independent of menopausal status. No correlation was found with LPL activity. A subsample of women with high plasma IL‐6 (n = 10) was matched with women with low plasma IL‐6 (n = 10) for total body fat mass. OM adipocyte glycerol release in response to isoproterenol (10^?5 to 10^?8 mol/l) was higher in the subsample of women with elevated plasma IL‐6 (P ≤ 0.07). Discussion: We observed that OM lipolysis was significantly higher in women with elevated plasma IL‐6 for a similar body fat mass and menopausal status. These results suggest that higher circulating IL‐6 concentrations are associated with increased isoproterenol‐stimulated lipolysis especially in OM abdominal adipocytes in women.