Metabolism of chylomicron-like emulsions in carriers of the S447X lipoprotein lipase polymorphism

Background: Lipoprotein lipase catalyzes the hydrolysis of the triglycerides contained in both very-low-density lipoproteins and chylomicrons for storage in the adipose tissue and muscle of fats of both hepatic and dietary origin. The S447X-Stop lipoprotein lipase is the most common polymorphism of the enzyme, affecting roughly 20% of the population and is accompanied by normal or diminished fasting triglycerides and perhaps lower incidence of coronary artery disease (CAD). Delay in the removal of chylomicron and remnant is now an established risk factor for CAD. Methods: Currently, the chylomicron metabolism has been evaluated in 12 normolipidemic subjects with the S447X-Stop and in 13 age- and sex-paired control subjects with no mutation. The doubly labeled chylomicron-like emulsion method was used to evaluate chylomicron metabolism. The emulsions labeled with cholesteryl-oleate ( 14C-CE) and tri[9,10- 3H]oleate ( 3H-Tg) were injected intravenously and the decay curves of the labels were determined by blood sampling over 60 min followed by radioactive counting. Results: The fractional clearance rate (FCR, min −1) of the labels was not different in the S447X carriers compared with the noncarriers (FCR 3H-Tg 0.035±0.019 and 0.030±0.009 ; FCR 14C-CE 0.008±0.007 and 0.009±0.007, respectively). Conclusions: The chylomicron intravascular lipolysis monitored by the 3H-Tg emulsion and the remnant removal monitored by the 14C-CE emulsion were not altered by the presence of this polymorphism of great populational impact.