Obesity favors apolipoprotein E- and C-III-containing high density lipoprotein subfractions associated with risk of heart disease

Human HDLs have highly heterogeneous composition. Plasma concentrations of HDL with apoC-III and of apoE in HDL predict higher incidence of coronary heart disease (CHD). The concentrations of HDL-apoA-I containing apoE, apoC-III, or both and their distribution across HDL sizes are unknown. We studied 20 normal weight and 20 obese subjects matched by age, gender, and race. Plasma HDL was separated by sequential immunoaffinity chromatography (anti-apoA-I, anti-apoC-III, anti-apoE), followed by nondenaturing-gel electrophoresis. Mean HDL-cholesterol concentrations in normal weight and obese subjects were 65 and 50 mg/dl (P = 0.009), and total apoA-I concentrations were 119 and 118 mg/dl, respectively. HDL without apoE or apoC-III was the most prevalent HDL type representing 89% of apoA-I concentration in normal weight and 77% in obese (P = 0.01) individuals; HDL with apoE-only was 5% versus 8% (P = 0.1); HDL with apoC-III-only was 4% versus 10% (P = 0.009); and HDL with apoE and apoC-III was 1.5% versus 4.6% (P = 0.004). Concentrations of apoE and apoC-III in HDL were 1.5-2× higher in obese subjects (P ≤ 0.004). HDL with apoE or apoC-III occurred in all sizes among groups. Obese subjects had higher prevalence of HDL containing apoE or apoC-III, subfractions associated with CHD, whereas normal weight subjects had higher prevalence of HDL without apoE or apoC-III, subfractions with protective association against CHD.

Methylation at CPT1A locus is associated with lipoprotein subfraction profiles

Lipoprotein subfractions help discriminate cardiometabolic disease risk. Genetic loci validated as associating with lipoprotein measures do not account for a large proportion of the individual variation in lipoprotein measures. We hypothesized that DNA methylation levels across the genome contribute to interindividual variation in lipoprotein measures. Using data from participants of the Genetics of Lipid Lowering Drugs and Diet Network (n = 663 for discovery and n = 331 for replication stages, respectively), we conducted the first systematic screen of the genome to determine associations between methylation status at ∼470,000 cytosine-guanine dinucleotide (CpG) sites in CD4(+) T cells and 14 lipoprotein subfraction measures. We modeled associations between methylation at each CpG site and each lipoprotein measure separately using linear mixed models, adjusted for age, sex, study site, cell purity, and family structure. We identified two CpGs, both in the carnitine palmitoyltransferase-1A (CPT1A) gene, which reached significant levels of association with VLDL and LDL subfraction parameters in both discovery and replication phases (P < 1.1 × 10(-7) in the discovery phase, P < .004 in the replication phase, and P < 1.1 × 10(-12) in the full sample). CPT1A is regulated by PPARα, a ligand for drugs used to reduce CVD. Our associations between methylation in CPT1A and lipoprotein measures highlight the epigenetic role of this gene in metabolic dysfunction.

Associations between high density lipoprotein mean particle size and serum paraoxonase-1 activity

BACKGROUND

High density lipoprotein (HDL) particles are heterogeneous in composition, structure, size, and may differ in conferring protection against cardiovascular disease. HDL associated enzyme, paraoxonase-1 (PON1), has an important role in attenuation of atherogenic low density lipoprotein (LDL) oxidation. The aim of this study was to investigate the associations between HDL particle size and PON1 activity in relation to serum HDL cholesterol (HDL-C) levels.

MATERIALS AND METHODS

One hundred and forty healthy subjects contributed to this study. HDL was separated by sequential ultracentrifugation and its size was estimated by dynamic light scattering. Paraoxonase activity was measured spectrophotometrically using paraoxon as substrate.

RESULTS

Results of this study showed that PON1 activity had negative correlations with HDL mean particle size (r = -0.22, P < 01), HDL2/HDL3 ratio, and serum HDL-C levels (r = -0.25, P < 0.01). HDL mean particle size and HDL2/HDL3 ratio had negative correlation with body mass index (BMI), waist hip ratio (WHR), and serum triglyceride (TG) levels, and positive correlation with serum HDL-C levels. Serum HDL-C levels had significant positive correlations with age, total cholesterol (TC), and apolipoprotein A-I (apo A-I) and significant negative correlation with BMI, WHR, and TG.

CONCLUSION

Based on the results of this study, determination of HDL mean particle size beside the serum PON1 activity may help to better understand the CAD risks, pathogenesis, and prognosis, and may also help to design therapeutic protocols toward beneficial modifications of HDL characteristics.