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 increased incidence of hyperinsulinemia. In such a condition, hyperinsulinemia could be due to an increased lipolytic activity of omental adipose tissue (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 visceral or subcutaneous abdominal fat accumulation, evaluated by computerized tomography. The relationship between plasma insulin values and in vitro lipolytic activity in both tissues was studied. Thirteen visceral (VO) and 13 subcutaneous (SO) obese patients, matched for sex and body mass index, undergoing vertical banded gastroplasty, were studied. Before surgery, in each patient an OGTT was performed. During surgery, samples of epigastric subcutaneous and omental AT were obtained for evaluation of fat cell weight (FCW) and basal, noradrenaline 10(-5)M and isoprenaline 10(-5) M induced lipolytic activities. No significant differences in basal lipolysis were found between the two types of obesity, both in omental and in epigastric AT. In omental AT, a higher noradrenaline and isoprenaline induced lipolysis was observed in VO than in SO. Isoprenaline induced lipolysis of omental AT (expressed per cell surface area) correlated directly with FCW. VO patients showed plasma insulin values after OGTT significantly higher than SO patients. In the whole group of patients, independently from fat distribution, significant correlations were found between the incremental areas of the plasma insulin curve during OGTT and the noradrenaline an isoprenaline induced lipolytic activities both in omental and epigastric adipose tissue.