IMPACT OF GENDER ON THE METABOLISM OF APOLIPOPROTEIN-A-I IN HDL SUBCLASSES LPAI AND LPAI-AII IN OLDER SUBJECTS

The behavior of apolipoprotein (apo) A-I in lipoprotein (Lp) AI and Lp AI:AII was studied in 11 postmenopausal females and 11 males matched f or plasma triglyceride and total cholesterol levels. Subjects consumed a baseline diet [35% fat (14% saturated, 15% monounsaturated, and 7% polyunsaturated), 15% protein, 49% carbohydrate, and 147 mg cholestero l/1000 kcal] for 6 weeks before the start of the kinetic study. At the end of the diet period, using a primed-constant infusion of [5,5,5-H- 2(3)]leucine. residence times (RT) and secretion rates (SR) of apoA-I were determined in 2 subpopulations of high-density lipoprotein (HDL) particles, LpAI and LpAI:AII. Plasma total cholesterol, low-density li poprotein cholesterol, and triglyceride concentrations were similar in males and females. The mean plasma HDL cholesterol concentration in m ales (1.14+/-0.23 mmol/L mean+/-SD) was lower than in females (1.42+/- 0.18 mmol/L; P=.0034). Similarly, the mean plasma concentration of apo A-I in males (130+/-21 mg/dL) was lower than that in females (150+/-19 mg/dL; P=.0421). The RT of apoA-I in either LpAI or LpAI:AII was simi lar between men and women. Despite the higher plasma apo A-I levels in female compared with male subjects, total apoA-I and apoA-I in LpAI a nd LpAI:AII pool sizes were similar weight of the female subjects. The mean SR of total apoA-I in males (8.5+/-2.7 mg . kg(-1) . d(-1)) was 22% lower than in females (10.9+/-2.3 mg . kg(-1) . d(-1); P=.0389). T he SR of both apoA-I in LpAI and LpAI:AII was lower in males than fema les, although the differences did not reach statistical significance. These data suggest that the difference observed in HDL cholesterol con centration between males and females in attributable to SR of apoA-I a nd not the catabolic rate.