The measurement of apolipoprotein in vivo kinetics will be carried out using a primed-constant infusion of [D3]L-leucine. This protocol allows for the determination of the kinetics of all apolipoproteins simultaneously. Kinetics studies will be conducted in the constantly fed state where participants receive 1/30th of their daily energy requirements every half-hour for the whole duration of the test (15 hours). These methods are described in detail in previous publications from our group. Briefly, at 7am on the morning of the study, after a 12-hour overnight fast, participants will be admitted to the Toronto General Hospital Clinical Investigation Unit and two intravenous catheters (IV's) will be inserted, one into each forearm vein. One IV will be for infusion of the stable isotope described below and one for withdrawal of blood samples. After achieving a steady state (3hrs after the small half-hourly meals), subjects will first receive a bolus injection of 10 µmol/kg of body weight of [D3]L-leucine ([D3]L-leucine 98%, C/D/N Isotopes) dissolved in physiological saline (0.9% NaCl) and then a constant infusion of 10 µmol/kg/h of [D3]L-leucine for 12 hours via an intravenous line inserted into a left forearm vein. Blood samples will be collected at regular intervals (0, 1/2, 1, 2, 4, 6, 8, 10, 11, 12hrs). All lipoprotein subfractions will be separated by sequential ultracentrifugation and frozen thereafter at -80oC until they are processed for analysis.