Lipid metabolism in omental adipose tissue during operative surgery

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.

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.

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.

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.