OMENTAL AND EPIGASTRIC ADIPOSE-TISSUE LIPOLYTIC-ACTIVITY IN HUMAN OBESITY - EFFECT OF ABDOMINAL FAT DISTRIBUTION AND RELATIONSHIP WITH HYPERINSULINEMIA

It has been shown that visceral obesity is associated with an increase d incidence of hyperinsulinemia. In such a condition, hyperinsulinemia could be due to an increased lipolytic activity of omental adipose ti ssue (AT), through an enhanced portal flux of FFA. The purpose of our study was to evaluate the lipolytic activity of omental and epigastric AT obtained from morbid obese patients either with prevalently viscer al or subcutaneous abdominal fat accumulation, evaluated by computeriz ed tomography. The relationship between plasma insulin values and in v itro lipolytic activity in both tissues was studied. Thirteen visceral (VO) and 13 subcutaneous (SO) obese patients, matched for sex and bod y mass index, undergoing vertical banded gastroplasty, were studied. B efore surgery, in each patient an OGTT was performed. During surgery, samples of epigastric subcutaneous and omental AT were obtained for ev aluation of fat cell weight (FCW) and basal, noradrenaline 10(-5) M an d isoprenaline 10(-5) M induced lipolytic activities. No significant d ifferences in basal lipolysis were found between the two types of obes ity, both in omental and in epigastric AT. In omental AT, a higher nor adrenaline and isoprenaline induced lipolysis was observed in VO than in SO. Isoprenaline induced lipolysis of omental AT (expressed per cel l surface area) correlated directly with FCW VO patients showed plasma insulin values after OGTT significantly higher than SO patients. In t he whole group of patients, independently from fat distribution, signi ficant correlations were found between the incremental areas of the pl asma insulin curve during OGTT and the noradrenaline and isoprenaline induced lipolytic activities both in omental and epigastric adipose ti ssue. In omental adipose tissue, these correlations were found only in VO and not in SO patients. In conclusion, VO patients showed a higher noradrenaline induced lipolytic activity of omental AT than SO patien ts. This increased catecholamine stimulated lipolysis is related to th e higher omental fat cell size characteristic of the visceral obese pa tients. A relationship exists between hyperinsulinemia and lipolytic a ctivity of epigastric AT in the obese patients, independently from fat distribution, while in omental AT, such a relationship was found only in VO patients.