VARIATION IN ADRENERGIC REGULATION OF LIPOLYSIS BETWEEN OMENTAL AND SUBCUTANEOUS ADIPOCYTES FROM OBESE AND NONOBESE MEN

Regional variations in adipocyte lipolysis between subcutaneous and vi sceral fat may be important for obesity complications. In the present study, we compared adrenergic regulation of lipolysis in omental and s ubcutaneous adipocytes from obese (n = 15) and non-obese (n = 14) male subjects. Waist-to-hip ratio, blood pressure, plasma insulin, and pla sma triglycerides were increased in obesity. No regional differences i n adrenoceptor lipolytic function were observed in non-obese subjects with the exception of a slight increase in noradrenaline sensitivity i n omental adipocytes (P < 0.05), because of increased beta(1)-adrenoce ptor sensitivity (P < 0.05). In the obese subjects, the rate of noradr enaline-induced glycerol release was 2-fold higher (P < 0.005) and the noradrenaline sensitivity was 3-fold higher (P < 0.05) in omental ver sus subcutaneous adipocytes. These findings were mainly due to a 50-fo ld increase in omental beta(3)-adrenoceptor sensitivity (P < 0.002) an d to a smaller 6-fold increase in omental beta(1)-adrenoceptor sensiti vity (P < 0.02), accompanied by increased Pb as well as beta(1)-adreno ceptor 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-o bese males. In contrast, catecholamine-induced lipolysis is markedly i ncreased in omental as compared to subcutaneous adipocytes in obese ma les, mainly due to an increase in beta(3)-adrenoceptor function of vis ceral fat cells, in combination with a smaller increase in beta(1)-adr enoceptor function.