Influence of trauma on plasma elimination of exogenous fat and on lipoprotein lipase activity and mass

Background: Trauma is followed by an increased plasma clearance and oxidation of exogenous fat but the underlying mechanism is not fully understood. Aim: To examine the influence of a surgical trauma on the plasma elimination of exogenous triglycerides (TG) and its relationship with lipoprotein lipase (LPL) activity and LPL mass. Methods: Nine patients underwent a hypertriglyceridaemic clamp and a lipolytic capacity test before and after open abdominal surgery. The infusion rate was adjusted to maintain a stable TG concentration of 4 mmol×l−1 during 180 min. The lipolytic capacity was determined as the change in LPL activity and mass following a bolus dose of 100 IU×kg BW−1 heparin sodium. Results: Postoperatively, the plasma elimination rate of fat was 2.6 times higher (P<0.001). Infusion of lipids in the postoperative state was followed by a smaller rise in free fatty acids (P<0.05) in comparison with the preoperative situation. The postoperative basal fasting LPL activity was half of that in the preoperative state and the LPL activity rose almost two-fold during the clamp. The heparin-induced rises in LPL activity and LPL mass were similar (n.s.) before and after surgery. Conclusions: A moderate surgical trauma is accompanied by a greater than two-fold rise in plasma elimination rate of exogenous fat despite a lower basal LPL activity and a virtually unchanged LPL pattern during infusion of lipids. Our study demonstrates that although trauma may substantially enhance the fat elimination capacity a significant proportion of the infused fat is not utilized for metabolic purposes.