Concentrations and compositions of plasma lipoprotein subfractions of Lpb5-Lpu1 homozygous and heterozygous swine with hypercholesterolemia.

Pigs with two mutant epitopes, Lpb5 of apolipoprotein B (apoB) and Lpu1 of a yet undefined apolipoprotein, specified by a haplotype Lpb5-Lpu1 and fed a cholesterol-free low fat diet show hypercholesterolemia. The purpose of this study was to establish whether a direct relationship exists between the swine lipoprotein concentration/composition and the genotype for the Lpb5-Lpu1 haplotype; i.e., homozygote versus heterozygote. Lipoproteins of fasted plasma from hypercholesterolemic swine, homozygous (HmHC) and heterozygous (HtHC) for Lpb5-Lpu1, and from normolipidemic (NL) pigs of other Lpb-Lpu haplotypes were separated into five layers by density gradient ultracentrifugation. Layer 1 contained particles of d less than 1.019 g/ml and layer 5 particles of d greater than 1.073 g/ml. Layers 2, 3, and 4 represented subfractions of low density lipoproteins (LDL). The plasma total cholesterol (TC) of the HmHC group (300 +/- 84 mg/dl) was different (P less than 0.05) from the HtHC group (200 +/- 80 mg/dl) and in both HmHC and HtHC, TC was significantly higher (P less than 0.0005 and P less than 0.005, respectively) than that of the NL group (69 +/- 14 mg/dl). The elevation in plasma TC was due to the increased TC in layers 2 and 3: a 13- and 7-fold increase in HmHC and a 7- and 4-fold increase in HtHC in layers 2 and 3, respectively. Parallel increases in unesterified cholesterol were observed in these two layers. Marked increases in apoB were also observed in layers 2 and 3 of HmHC and intermediate increases in apoB in the same two layers of HtHC.(ABSTRACT TRUNCATED AT 250 WORDS)