Age- and sex-related differences in lipoproteins containing apoprotein A-I

We investigated age- and sex-related differences in the structure and composition of two species of lipoproteins that contain apoprotein (apo) A-I (A-I Lp): lipoproteins containing apo A-I and apo A-II (Lp A-I/A-II), and lipoprotein containing apo A-I but no apo A-II (Lp A-I), which were isolated by immunoaffinity chromatography. Sixty normolipidemic volunteers were assigned to one of three groups based on their ages and sexual maturation (Group A, prepubertal; Group B, puberty; and Group C, postpuberty). In A-I Lp, the levels of total cholesterol, cholesteryl ester, phospholipid, and apo A-I were lower in males during puberty and then remained stable. In Lp A-I/A-II, there were no age- or sex-related changes in lipids or in apo A-II. Levels of apo A-I in the females were lower with advance in age, although significant differences were observed only between pre- and postpubertal subjects. In Lp A-I, the levels of total cholesterol, cholesteryl ester, phospholipid, and apo A-I were lower in males during puberty and remained stable thereafter, as in the case of A-I Lp. Therefore, the age- and sex-related differences observed in A-I Lp appear to be primarily due to the differences in Lp A-I. When we take into account the constancy of Lp A-I/A-II levels in all groups, the physiological function of A-I Lp (high density lipoprotein) in each individual may be limited by the Lp A-I levels.