EFFECTS OF WEIGHT-REDUCTION ON THE REGULATION OF LIPOLYSIS IN ADIPOCYTES OF WOMEN WITH UPPER-BODY OBESITY

1. The regulation of lipolysis was studied in 14 upper-body obese wome n aged 26-55 years. Isolated subcutaneous adipocytes from the abdomina l region were examined before and after an 8 to 12-week-long weight re duction programme, during which the mean body mass index (kg/m(2)) of the group was reduced from 36.4 +/- 0.9 to 30.3 +/- 1.0. 2. Fat cell v olume was reduced from 891 +/- 39 to 655 +/- 45 pl, The sensitivity to noradrenaline stimulation of lipolysis in vitro increased fivefold af ter weight reduction, A corresponding increase in sensitivity was foun d with the beta(2)-selective adrenoceptor agonist terbutaline. However , the number of beta(2)-adrenoceptor binding sites as assessed by radi oligand binding with I-125-labelled cyanopindolol was not changed, No changes were observed when dobutamine (a beta(1)-selective adrenocepto r agonist) and clonidine (an alpha(2)-adrenoceptor agonist) were used, 3, The basal lipolysis rates decreased by about 50% after weight redu ction and the maximum enzyme activity of hormone-sensitive lipase was also reduced by almost 50%. 4, Plasma concentrations of insulin, norad renaline and total testosterone decreased and sex hormone-binding glob ulin increased after weight reduction, Calculated apparent free testos terone levels decreased by more than 40% after weight reduction. 5. In conclusion, weight reduction leads to increased efficiency of adipocy te lipolysis with decreased resting lipolysis rate but increased sensi tivity to stimulation by catecholamines, which may be attributed to a decreased activity of hormone-sensitive lipase and an increased sensit ivity of beta(2)-adrenoceptors. Changes in circulating levels of catec holamines, insulin and testosterone may play a role in these modificat ions of adipocyte function, The increased lipolytic efficiency may be of importance for amelioration of the metabolic complications of obesi ty that are observed after weight reduction.