TRL, IDL, and LDL apolipoprotein B-100 and HDL apolipoprotein A-I kinetics as a function of age and menopausal status

Objective - To determine mechanisms contributing to the altered lipoprotein profile associated with aging and menopause, apolipoprotein B- 100 ( apoB- 100) and apoA- I kinetic behavior was assessed. Methods and Results - Eight premenopausal ( 25 +/- 3 years) and 16 postmenopausal ( 65 +/- 6 years) women consumed for 6 weeks a standardized Western diet, at the end of which a primed- constant infusion of deuterated leucine was administered in the fed state to determine the kinetic behavior of triglyceride- rich lipoprotein ( TRL), intermediate-density lipoprotein ( IDL), and low- density lipoprotein ( LDL) apoB- 100, and high- density lipoprotein ( HDL) apoA- I. Data were fit to a multicompartmental model using SAAM II to calculate fractional catabolic rate ( FCR) and production rate ( PR). Total cholesterol, LDL cholesterol ( LDL- C), TRL- C, and triglyceride levels were higher ( 50%, 55%, 130%, and 232%, respectively) in the postmenopausal compared with the premenopausal women, whereas HDL- C levels were similar. Plasma TRL, IDL, and LDL - apoB- 100 levels and pool sizes ( PS) were significantly higher in the postmenopausal than premenopausal women. These differences were accounted for by lower TRL, IDL, and LDL apoB- 100 FCR ( P < 0.05), with no difference in PR. There was no significant difference between groups in HDL- C levels or apoA- I kinetic parameters. Plasma TRL- C concentrations were negatively correlated with TRL apoB- 100 FCR ( r = - 0.46; P < 0.05) and positively correlated with PR ( r = 0.62; P < 0.01). Plasma LDL- C concentrations were negatively correlated with LDL apoB- 100 FCR ( r = - 0.70; P < 0.001) but not PR. Conclusions - The mechanism for the increase in TRL and LDL apoB- 100 PS observed in the postmenopausal women was determined predominantly by decreased TRL and LDL catabolism rather than increased production. No differences were observed in HDL apoA- I kinetics between groups.