Lipid metabolism in omental adipose tissue during operative surgery

Background. Omental adipose tissue is a pure depot of visceral adipose tissue. We investigated the regulation of lipid metabolism in human omental tissue in vivo by the arterio-venous technique. Materials and methods. Six adults were studied while undergoing elective colonic surgery. Their omental vein was cannulated intraoperatively, and after obtaining the baseline blood samples, 50 ml of 50% dextrose solution was given intravenously and simultaneous arterio-venous samples were taken for the next 2 h. Concentration differences of lipid metabolites, glucose, and lactate were measured across the arterio-venous bed. The rates of action of hormone-sensitive lipase (HSL) and lipoprotein lipase (LPL) were calculated by stoichiometric analysis and the rate of re-esterification of nonesterified fatty acids (NEFA) was determined. Results. After an overnight fast there was a significant release of NEFA and glycerol from the omental adipose tissue (P < 0.05, P < 0.05). Intravenous glucose load caused a significant reduction in the arterial NEFA and glycerol concentrations (P < 0.05, P < 0.05), but only the arterio-venous concentration of NEFA decreased significantly (P < 0.05). There was no significant change in the arterio-venous concentration difference of glycerol, and the relative rate of action of HSL decreased, but not significantly (P = 0.09 at 30 min; P = 0.054 at 120 min). The ratio of release of NEFA to glycerol changed significantly (ANOVA; P < 0.05) from 2.93:1 to 0.1:1. Conclusion. The net release of NEFA by omental adipose tissue is primarily regulated by their local re-esterification. The change in the rate of action of HSL and LPL plays a minor role in the net release of NEFA by omental adipose tissue.