Relationship of the phenotypic expression of the A-IMilano apoprotein with plasma lipid and lipoprotein patterns.

The plasma lipoprotein and apolipoprotein profile of 29 adult A-IMilano (A-IM) carriers and 29 age- and sex-matched non-affected subjects of the same kindred was examined, in order to investigate linkages between the lipid and apoprotein abnormalities and the phenotypic expression of the biochemical disorder. Carriers (A-IM+) showed a higher prevalence of hypertriglyceridemia (12 out of 29); they also had lower plasma total cholesterol, esterified cholesterol and phospholipids, compared to non-carriers. Lipoproteins were characterized by a significant enrichment of triglycerides in low and high density fractions (LDL and HDL), and by the expected striking reduction of HDL mass and cholesterolemia. Conversely, no significant alterations of the major circulating apolipoprotein levels, except for apo A-I and apo A-II, were noted in the A-IM+. The increased free cholesterol/esterified cholesterol ratio in plasma (most marked in HDL), was accompanied by a significant reduction of the lecithin cholesterol acyl transferase molar activity. Several correlations pertaining to lipids, lipoproteins and apoproteins were examined: cholesterol and triglycerides in HDL and, more remarkably, apoprotein A-I and C-III levels in plasma were significantly correlated in the A-IM+. While there was no significant prevalence of specific apo E phenotypes, plasma triglycerides and apo C-II levels were highly correlated in the carriers. The A-IM subjects, while in the presence of severe lipoprotein risk factors, may have alternative mechanisms of cholesterol disposal, potentially responsible for the apparently low prevalence of atherosclerosis.