Site- and Sex-Related Differences in Adrenoreceptor Status of Human Adipose Tissue*

At equal degrees of absolute adiposity, the risk of associated morbidities such as hypertension, stroke, and ischemic heart disease is greater in individuals with predominantly abdominal as opposed to gluteal fat deposits (high waist to hip circumference ratio). We studied the in vitro status of adrenergic receptors controlling lipolysis (beta 1) and antilipolysis (alpha 2) in small fragments of adipose tissue from abdominal and gluteal sc depots of six obese women and six obese men. Lipolysis rate was measured by a double isotope technique which detects changes in the specific activity of fatty acids esterified to newly synthesized triglycerides. The lipolytic response to the beta-adrenergic agonist isoproterenol was significantly greater in abdominal compared to gluteal adipose tissue in both sexes. There was, however, no significant sex-related difference in response to isoproterenol within sites. When tissue from both sites was exposed to the mixed alpha/beta-adrenergic agonist norepinephrine there was a significantly greater lipolytic response in abdominal tissue. Within-site by sex analysis indicated no significant difference in the lipolytic response of gluteal tissue to norepinephrine, but a greater response of abdominal tissue in women. Given the apparently equal degree of beta responsiveness in abdominal tissue of both sexes, the norepinephrine data suggest that men have more abdominal alpha 2 receptor function (antilipolysis) than women. This difference may partially explain the greater tendency for men to accumulate adipose tissue in the abdominal region.