Variation in adrenergic regulation of lipolysis between omental and subcutaneous adipocytes from obese and non-obese men

Regional variations in adipocyte lipolysis between subcutaneous and visceral fat may be important for obesity complications. In the present study, we compared adrenergic regulation of lipolysis in omental and subcutaneous adipocytes from obese (n = 15) and non-obese (n = 14) male subjects. Waist-to-hip ratio, blood pressure, plasma insulin, and plasma triglycerides were increased in obesity. No regional differences in adrenoceptor lipolytic function were observed in non-obese subjects with the exception of a slight increase in noradrenaline sensitivity in omental adipocytes (P < 0.05), because of increased beta(1)-adrenoceptor sensitivity (P < 0.05). In the obese subjects, the rate of noradrenaline-induced glycerol release was 2-fold higher (P < 0.005) and the noradrenaline sensitivity was 3-fold higher (P < 0.05) in omental versus subcutaneous adipocytes. These findings were mainly due to a 50-fold increase in omental beta(3)-adrenoceptor sensitivity (P < 0.002) and to a smaller 6-fold increase in omental beta(1)-adrenoceptor sensitivity (P < 0.02), accompanied by increased beta(3)- as well as beta(1)-adrenoceptor lipolytic rates at approximately 50% receptor subtype occupancy by the agonist (P < 0.05). In conclusion, minor regional differences in adipocyte lipolytic response to catecholamines are present in non-obese males. In contrast, catecholamine-induced lipolysis is markedly increased in omental as compared to subcutaneous adipocytes in obese males, mainly due to an increase in beta(3)-adrenoceptor function of visceral fat cells, in combination with a smaller increase in beta(1)-adrenoceptor function.