Relationship between visceral fat and adipocyte insulin resistance in caucasian and african-american women

A previous study (Dowling HJ, Metabolism 1995) indicated that upper body obesity, as assessed by waist to hip ratio (WMR), was associated with adipocyte insulin resistance, in Caucasian (W), but not AfricanAmerican (B), women. However, the relationship of visceral adiposity and WHR differs between B and W women. We reassessed the relationship of visceral adiposity and adipocyte insulin resistance in 23 B and 21 W weight-stable, obese, premenopausal, nondiabetic women with a wider range of body fat distribution by WHR than previously studied. Visceral adipose tissue (VAT) was determined by magnetic resonance imaging and ranged from 32.5-239.2 cm² in B. 24.7-258.1 cm² in W. Coilagenase-isolated abdominal subcutaneous adipocytes were incubated with adenosine deaminase (ADA) to stimulate lipolysis, and with a range of insulin concentrations (0, 25, 50, 100, 400 pM) to inhibit lipolysis. B and W groups were not different with regard to BMI (34.8±4.6 vs. 36.0±4.9), WHR (0.84±0.08 vs. 0.80±0.06), VAT (111.1±49.9 vs. 133.1159.3 cm2), or visceral to subcutaneous adipose tissue area (VAT/SCAT) ratio (0.27±0.12 vs. 0.29±0.11). Sensitivity to the antilipolytic effect of insulin (ED50) was related to WHR alone and to VAT/SCAT ratio, after adjusting for total fat mass, similarly in B and W women. However, ED50 was not significantly correlated with VAT, both with and without adjusting for total fat mass, in both groups combined (p=0.16) or separately. We conclude that B and W women with comparably high levels of relative visceral adiposity, as defined by either WHR or VAT/SCAT ratio, are equally resistant to the antilipolytic effect of insulin.