Development of a novel method to determine very low density lipoprotein kinetics

Isotopic tracer methods of determining triglyceride-rich lipoprotein (TRL) kinetics are costly, time-consuming, and labor-intensive. This study aimed to develop a simpler and cost-effective method of obtaining TRL kinetic data, based on the fact that chylomicrons compete with large VLDL (VLDL1; Sf = 60–400) for the same catalytic pathway. Ten healthy subjects [seven men; fasting triglyceride (TG), 44.3–407.6 mg/dl; body mass index, 21–35 kg/m2] were given an intravenous infusion of a chylomicron-like TG emulsion (Intralipid; 0.1 g/kg bolus followed by 0.1 g/kg/h infusion) for 75–120 min to prevent the clearance of VLDL1 by lipoprotein lipase. Multiple blood samples were taken during and after infusion for separation of Intralipid, VLDL1, and VLDL2 by ultracentrifugation. VLDL1-apolipoprotein B (apoB) and TG production rates were calculated from their linear increases in the VLDL1 fraction during the infusion. Intralipid-TG clearance rate was determined from its exponential decay after infusion. The production rates of VLDL1-apoB and VLDL1-TG were (mean ± SEM) 25.4 ± 3.9 and 1,076.7 ± 224.7 mg/h, respectively, and the Intralipid-TG clearance rate was 66.9 ± 11.7 pools/day. Kinetic data obtained from this method agree with values obtained from stable isotope methods and show the expected relationships with indices of body fatness and insulin resistance (all P < 0.05). The protocol is relatively quick, inexpensive, and transferable to nonspecialist laboratories.