Insulin resistance in adipocytes of obese women: effects of body fat distribution and race.

Upper-body obesity (UBO) in white women is associated with increased fatty acid turnover and resistance to the effects of insulin on systemic glucose metabolism. The present study determined whether the abilities of insulin to stimulate glucose transport and suppress lipolysis are impaired in adipocytes from white UBO (W-UBO) women. Because the clinical risks associated with UBO are attenuated in black women, the effects of race on adipocyte insulin sensitivity were assessed. Forty-two healthy, equally obese women were selected for study on the basis of race (black or white) and body fat distribution (UBO or lower-body obesity [LBO]). In white women, both abdominal and gluteal fat cells from the UBO versus LBO group were less responsive to the stimulatory effects of insulin on glucose uptake and less sensitive to the antilipolytic effects of insulin and the adenosine analog, phenylisopropyladenosine (PIA). In contrast, in black women, fat cells from UBO and LBO groups were equally sensitive to the stimulatory effects of insulin on glucose transport and the suppressive effects of insulin and PIA on lipolysis. These in vitro data correlate well with previous clinical findings that UBO in white women but not in black women is associated with insulin resistance and dyslipidemia. Thus, resistance to the antilipolytic effects of insulin and adenosine at the level of adipose tissue may increase systemic lipolysis and play a role in the development or maintenance of peripheral insulin resistance associated with UBO in white women, but not in black women.