INTERACTIONS AMONG LP(A) PHENOTYPES, LP(A) CONCENTRATIONS AND LIPOPROTEIN RESPONSE TO FAT-MODIFIED DIETS

Lipoprotien(a) (Lp(a)), an LDL-like particle containing apo(a), a high ly glycosylated protein, is a significant genetic risk factor for coro nary heart disease (CHD), Lp(a) phenotypes are characterized into sing le-band and double-band phenotypes according to electrophoretic mobili ty compared to that of apo B-100. The first goal was to assess whether Lp(a) phenotype influences the concentrations and metabolism of other serum lipoproteins. A second focus was to evaluate the effect on Lp(a ) concentrations of substituting medium chain saturated fat for a poly unsaturated, baseline diet. In this two-way cross-over study 18 female s ate a baseline, polyunsaturated fat diet (Poly/Sat en% ratio = 10.5/ 11.9) for 1 week, and then a high saturated fat diet for 4 weeks (Poly /Sat en% ratio = 3.4/19.8) providing either 14 energy % medium chain t riglycerides (MCT) 8:0 + 10:0 or 12:0 whereas monounsaturated fat was held constant. Subjects with double-band Lp(a) phenotypes had higher ( P = 0.000) Lp(a) levels on the baseline diet compared to single-band p henotypes. Both diets decreased serum Lp(a) concentration about 30% (P < 0.05) but raised serum LDL-C about 11%. On the baseline diet, Lp(a) polymorphism did not affect serum LDL-cholesterol levels or receptor- mediated uptake and degradation of LDL. In a two-way ANOVA 8:0 + 10:0 and 12:0 had significantly different effects on change in serum HDL-C concentrations and LDL receptor activity in MNC, but Lp(a) polymorphis m had no effect on the variables measured in this study. These results suggest that the response of LDL and Lp(a) levels to the two saturate d fat diets were independen of each other. Lp(a) polymorphism dod not seem to influence LDL metabolism. (C) Elsevier Science Inc. 1998.