Effect of chronic glucagon administration on the metabolism of triacylglycerol-rich lipoproteins in rats fed a high sucrose diet.

Male adult Wistar rats were fed a semipurified diet rich in sucrose (53 g/100 g diet). The effects of chronic glucagon administration (20 micrograms.day-1.rat-1, for 21 d) were studied on plasma lipid levels, triacylglycerol secretion rates and fractional catabolic rates determined by the intravenous fat tolerance test. Triacylglycerol secretion rates of plasma, chylomicron and very low density lipoprotein (VLDL) were measured by using the Triton WR 1339 method. In both fasting and postprandial states, the different rates were not significantly modified by glucagon treatment. However, in the treated animals, significantly decreased triacylglycerol concentrations were observed in plasma and VLDL during fasting (-41 and -46%, respectively) and also in chylomicrons in the postprandial state (-37%) relative to control animals. These data could be accounted for by an increased removal rate of triacylglycerol-rich lipoprotein. The estimated values of fractional rate constants (Triton WR 1339 experiment) were increased for VLDL (+62%) in the fasting state and for chylomicrons (+104%) in the postprandial state. Similarly, the fractional catabolic rate determined with the intravenous fat tolerance test (Intralipid, Kabivitrum, Sweden) was increased 49% by glucagon treatment, suggesting an effect of glucagon on the catabolism of triacylglycerol-rich lipoproteins. Glucagon treatment did not modify the composition of VLDL obtained 60 min after Triton WR 1339 injection, except that in the fasting state apo B100 proportions and concentrations increased, suggesting a specific effect on the hepatic secretion of apo B100 VLDL.