Fate of intravenously administered squalene and plant sterols in human subjects

We have studied metabolism of plant sterols and squalene administered intra venously in the form of lipid emulsion mimicking chylomicrons (CM). The CM- like Lipid emulsion was prepared by dissolving squalene in commercially ava ilable Intralipid (R). The emulsion was given as an intravenous bolus injec tion of 30 ml containing 6.3 mg of cholesterol, 1.9 mg of campesterol, 5.7 mg of sitosterol, 1.6 mg of stigmasterol, 18.1 mg of squalene, and 6 g of t riglycerides in six healthy volunteers. Blood samples were drawn from the o pposite arm before and serially 2.5-180 min after the injections. The decay of CM squalene, plant sterols, and triglycerides was monoexponential. The half-life of CM squalene was 74 +/- 8 min, that of campesterol was 37 +/- 5 min (P < 0.01 from squalene), and those of sitosterol, stigmasterol, and t riglycerides were 17 +/- 2, 15 +/- 1, and 17 +/- 2 min, respectively (P < 0 .01 from squalene and campesterol). The Chf squalene concentration still ex ceeded the baseline level 180 min after injection (P = 0.02), whereas plant sterols and triglycerides returned to the baseline level between 45 and 12 0 min after injection. The half-lives of squalene and campesterol were posi tively correlated with their fasting CM concentrations. In addition, VLDL s qualene, campesterol, and triglyceride concentrations, VLDL, LDL, and HDL s itosterol concentrations, as well as VLDL and LDL stigmasterol concentratio ns were increased significantly Cholesterol concentrations increased in VLD L (P < 0.05), but were unchanged in CM after injection. These data suggest that squalene clearance occurs more slowly than that of plant sterols and t riglycerides from CM, and that squalene is more tightly associated with tri glyceride-rich lipoproteins than are plant sterols in injected CM-like emul sions. - Relas, H., H. Gylling, and T. A. Miettinen. Fate of intravenously administered squalene and plant sterols in human subjects.