INSULIN THERAPY IN BURN PATIENTS DOES NOT CONTRIBUTE TO HEPATIC TRIGLYCERIDE PRODUCTION

Lipid kinetics were studied in six severely burned patients who were t reated with a high dose of exogenous insulin plus glucose to promote p rotein metabolism. The patients were 20+/-2-yr-old (SD) with 63+/-8% t otal body surface area burned. They were studied in a randomized order (a) in the fed state on the seventh day of a control period (C) of co ntinuous high-carbohydrate enteral feeding alone, and (b) on the seven th day of enteral feeding plus exogenous insulin (200 pmol/h = 28 U/h) with extra glucose given as needed to avoid hypoglycemia (I + G). Des pite a glucose delivery rate similar to 100% in excess of energy requi rements, the following lipid parameters were unchanged: (a) total hepa tic VLDL triglyceride (TG) secretion rate (0.165+/-0.138 [C] vs. 0.154 +/- 0.138 mmol/kg.d(-1) [I+G]), (b) plasma TG concentration (1.58+/-0. 66 [C] vs. 1.36+/-0.41 mmol/liter [I+G]), and (c) plasma VLDL TG conce ntration (0.68+/-0.79 [C] vs. 0.67+/- 0.63 mmol/liter [I+G]), Instead, the high-carbohydrate delivery in conjunction with insulin therapy in creased the proportion of de novo-synthesized palmitate in VLDL TG fro nt 13+/-5% (C) to 34+/-14% (I+G), with a corresponding decreased amoun t of palmitate from lipolysis, In association with the doubling of the secretion rate of de novo-synthesized fatty acid (FA) in VLDL TG duri ng insulin therapy (P > 0.5), the relative amount of palmitate and ste arate increased from 35+/-5 to 44+/-8% and 4+/-1 to 7+/-2%, respective ly, in VLDL TG, while the relative concentration of oleate and linolea te decreased from 43+/-5 to 37+/-6% and 8+/-4% to 2+/-2%, respectively . A 15-fold increase in plasma insulin concentration did not change th e rate of release of FA into plasma (8.22+/-2.86 [C] vs. 8.72+/-6.68 m mol/kg.d(-1) [I+G]. The peripheral release of FA represents a far grea ter potential for hepatic lipid accumulation in burn patients than the endogenous hepatic fat synthesis, even during excessive carbohydrate intake in conjunction with insulin therapy.