Apolipoprotein E polymorphism, serum lipids and occurrence of "double pre-betalipoproteinemia' (DPBL) in subjects from two different populations

Prevalence of double pre-beta lipoproteinemia in hyperlipidemic patients is influenced by gender, menopausal status, and ApoE phenotype

Double pre-beta lipoproteinemia (DPBL) is a plasma lipoprotein phenotype characterized by the presence of two agarose gel electrophoretic populations of very low density lipoproteins (VLDLs, d < 1.006 g/mL), i.e., normal pre-beta-migrating VLDL and slow pre-beta VLDL. Slow pre-beta VLDL represents remnant lipoproteins derived from the hydrolysis of triglyceride (TG)-rich lipoproteins (TRLs), and thus DPBL is a characteristic of plasma remnant lipoprotein accumulation. To determine the prevalence of DPBL in our lipid clinic population, patients (n = 2501) were selected who (1) had an unambiguous VLDL electrophoretic phenotype and could be classified as having either DPBL (DPBL+), beta-migrating VLDL (beta-VLDL +), or an absence of both (DPBL/beta-VLDL-/-) and (2) had hypercholesterolemia (HC: plasma cholesterol > or = 6.2 mmol/L, n = 1017), hypertriglyceridemia (HTG: plasma TG > or = 2.3 mmol/L but < 15 mmol/L, n = 554) or combined hyperlipidemia (HC + HTG, n = 930). Patients with TG < 2.3 mmol/L and cholesterol < 5.2 mmol/L acted as control subjects (n = 343). Using a commercially available agarose gel electrophoresis system, we identified 220 hyperlipidemic patients (8.8%) with DPBL (versus < 1% of control). The prevalence of DPBL was higher in (1) male than in female patients (10.7% versus 6.7%), (2) postmenopausal than in premenopausal females (7.3% versus 4.1%), and (3) patients with HC + HTG than in those with HTG or HC alone (15.8% versus 8.3% versus 2.7%, respectively). Patients with an epsilon 2 allele had a higher prevalence of DPBL; i.e., 26.9% of apoE 3/2 and 26.2% of apoE 4/2 patients had DPBL compared with 6.5%, 6.8%, and 7.4% of apoE 3/3, 4/3, and 4/4 patients, respectively. DPBL patients consistently had increased levels of VLDL-C and (LDL + HDL)-TG and decreased levels of LDL-C, and their plasma lipid profiles were intermediate between those of beta-VLDL+ and DPBL/beta-VLDL -/- patients. These results demonstrate that male sex, postmenopausal status in women, and the presence of an apoE 3/2 or apoE 4/2 phenotype are associated with an increased incidence of DPBL in hyperlipidemic patients.

Prolonged postprandial responses of lipids and apolipoproteins in triglyceride-rich lipoproteins of individuals expressing an apolipoprotein epsilon 4 allele

The postprandial responses of apo B48, B100, E and lipids in triglyceride-rich lipoproteins (TRL) to a meal containing one-third of daily energy (39% fat calories) were compared in normolipidemic young men with apo E3/3 and apo E4/3 phenotypes. After the two groups consumed a diet rich in polyunsaturated fat for 15-29 d, their postabsorptive concentrations of TRL triglycerides, apo B48, and apo B100 were virtually identical, but their postprandial responses differed. In both groups, TRL apo B48 increased at 3 h but returned to postabsorptive values at 6 h only in the apo E3/3 group; in the apo E4/3 group the concentration of apo B48 at 6 h was 80% higher than postabsorptive values. TRL apo B100 also increased at 3 h in the two groups and fell to post-absorptive values at 6 h in the apo E3/3 group but remained 51% higher than postabsorptive concentrations in the apo E4/3 group; this response was closely coupled to that of TRL cholesterol and apo E. These observations suggest that clearance of intestinal and hepatogenous TRL remnants is impaired in young men with an apo E4/3 phenotype.

Apolipoprotein E polymorphism and plasma lipid, lipoprotein, and apolipoprotein levels in Italian children

We have investigated the effect of apolipoprotein (apo) E polymorphism on serum lipid, lipoprotein, and apolipoprotein levels in a sample of 195 children, aged 8-11 years, from Sezze, Central Italy. The relative frequencies of e2, e3, and e4 alleles were 0.062, 0.867, and 0.072, respectively. Variation at the apo E gene locus explained 5.1% of the sample variance in serum total cholesterol levels, 7.6% in low-density lipoprotein (LDL) cholesterol levels, 7.3% in apo B levels, and 14.1% in high-density lipoprotein-apo E (HDL-E) levels. The effect of the e2 allele was to lower levels of total cholesterol, LDL-cholesterol, and apo B and to raise levels of HDL-E, while the effect of the e4 allele was the opposite. Variation at the apo E gene locus was not associated with differences in serum triglyceride, HDL-cholesterol, or apo AI levels. The effects of common apo E polymorphisms and genetic variation associated with the PvuII RFLP of the apo B gene on serum apo B levels were additive, explaining 11.3% of the phenotypic variance in this sample. When the effect of apo E polymorphism on serum lipid traits was estimated in boys and girls separately, variation at the apo E gene locus explained 10.4, 13.3, 13.3, and 13.5% of the phenotypic variance in serum total cholesterol, LDL-cholesterol, apo B, and HDL-E levels, respectively, in boys, while in girls only the effect on HDL-E levels (19.3%) reached statistical significance. This study has demonstrated that genetic variations at the apo E locus contribute to the determination of serum lipid, lipoprotein, and apolipoprotein levels in youths and that the effects are gender specific.