👤 Carlos Lahoz

The effect of a common apolipoprotein (apo) A-IV polymorphism (substitution of histidine for glutamine at position 360) on plasma lipid, lipoprotein cholesterol and lipoprotein(a) (Lp(a)) levels, and on low-density lipoprotein (LDL) particle size was examined by genotyping in 2322 Caucasian men and women (mean age: 48.9+/-10.1 years) participating in the Framingham Offspring Study (FOS). The relative frequencies of the apo A-IV-Gln (apo A-IV-1) and the apo A-IV-His (apo A-IV-2) alleles were 0.932 and 0.068, respectively, and were in Hardy-Weinberg equilibrium. No effect of the apo A-IV-2 genotype was observed on plasma triglyceride, total and lipoprotein cholesterol, and LDL particle size in either men or women after adjustment for age and body mass index. To avoid a possible interaction between the apo E genotype and the apo A-IV genotype, subgroup analyses were undertaken in 1,414 male and female subjects with the apo E3/3 genotype. Among women in this group there was a significant effect of the apo A-IV-2 allele on triglyceride levels (p=0.046). This effect was no longer significant after adjustment for age and BMI (p=0.074). No significant allele effect on other lipoprotein levels, including Lp(a), was noted in apo E3/3 men or women. We have also conducted a meta-analysis of our own data and of other studies found in the literature, indicating a significant lowering effect of apo A-IV-2 on plasma triglycerides, but no effects on other parameters. In conclusion, the apo A-IV-2 allele is associated with a modest reduction in plasma triglyceride levels in the general population. Show less

Apolipoprotein (apo) CIII participates in the regulation of the metabolism of triglyceride-rich lipoproteins and it is a major component of chylomicrons and VLDL. The APOC3 gene is on chromosome 11q23 and is highly polymorphic. The less common allele (S2) of the SstI polymorphism on the 3' untranslated region of the APOC3 gene has been previously associated with increased triglycerides, total cholesterol (TC), and apoCIII levels and cardiovascular risk on several, but not all, studies. The aim of this study was to examine the association of this polymorphism with plasma lipid levels, lipoprotein subfractions and coronary heart disease (CHD) risk in a population-based study: The Framingham Offspring Study. The frequency of the S2 allele was 0.086, consistent with previous reports in Caucasian populations. In men, the S2 allele was associated with lower concentrations of high-density lipoprotein cholesterol (HDL-C; P<0.04) and HDL2-C (P<0.02) and a significant increase in apoCIII non-HDL (P<0.05). TG levels were higher in men carriers of the S2 allele, but this association did not reach statistical significance (P=0.30). Conversely, in women, the S2 allele was associated with increased TC (P<0.03), low-density lipoprotein cholesterol (LDL-C; P<0.03), and ApoB levels (P<0.04). Lipoproteins subfractions were also examined using nuclear magnetic resonance (NMR) spectroscopy. S2 male carriers had significantly lower concentrations of large LDL and a significant reduction in LDL particle size (P<0.04). In women, there was a significant increase in intermediate LDL particles (P<0.05) with no significant effect on lipoprotein diameters. We also examined the associations between the S2 allele and biochemical markers of glucose metabolism. In men, the S2 allele was associated with elevated fasting insulin concentrations (P<0.04), whereas no significant associations were observed in women. Despite the described associations with lipid and glucose metabolism related risk factors, we did not find any significant increase in CHD risk associated with the S2 allele in this population. Show less