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/m(2)) 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 <or= r <or= 0.65, P<0.05) and OM (0.36 <or= r <or= 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 <or= 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.