Distribution of HDL2 and HDL3 in a random population of healthy French males and females--evaluation by a two-step precipitation procedure

Transgenerational sperm DMRs escape DNA methylation erasure during embryonic development and epigenetic inheritance

Germline transmission of epigenetic information is a critical component of epigenetic inheritance. Previous studies have suggested that an erasure of DNA methylation is required to develop stem cells in the morula embryo. An exception involves imprinted genes that escape this DNA methylation erasure. Transgenerational differential DNA methylation regions (DMRs) have been speculated to be imprinted-like and escape this erasure. The current study was designed to assess if morula embryos escape the erasure of dichlorodiphenyltrichloroethane-induced transgenerational sperm DMR methylation. Observations demonstrate that the majority (98%) of transgenerational sperm DMR sites retain DNA methylation and are not erased, so appearing similar to imprinted-like sites. Interestingly, observations also demonstrate that the majority of low-density CpG genomic sites had a significant increase in DNA methylation in the morula embryo compared to sperm. This is in contrast to the previously observed DNA methylation erasure of higher-density CpG sites. The general erasure of DNA methylation during embryogenesis appears applicable to high-density DNA methylation sites (e.g. CpG islands) but neither to transgenerational DMR methylation sites nor to low-density CpG deserts, which constitute the vast majority of the genome's DNA methylation sites. The role of epigenetics during embryogenesis appears more dynamic than the simple erasure of DNA methylation.

Reference ranges of cholesterol sub-fractions in random healthy adults in Ouagadougou, Burkina Faso

In Burkina Faso, the values that serve as clinical chemistry reference ranges are those provided by European manufacturers' insert sheets based on reference of the Western population. However, studies conducted so far in some African countries reported significant differences in normal laboratory ranges compared with those of the industrialized world. The aim of this study was to determine reference values of cholesterol fractions in apparently normal adults in Burkina Faso that could be used to better assess the risks related to cardiovascular diseases. Study population was 279 healthy subjects aged from 15 to 50 years including 139 men and 140 women recruited at the Regional Center of Blood Transfusion of Ouagadougou, capital city of Burkina Faso (West Africa). Exclusion criteria based on history and clinical examination were used for defining reference individuals. The dual-step precipitation of HDL cholesterol sub-fractions using dextran sulfate was performed according to the procedure described by Hirano. The medians were calculated and reference values were determined at 2.5th and 97.5th percentiles. The median and upper ranges for total cholesterol, LDL cholesterol, total HDL cholesterol and HDL2 cholesterol were observed to be higher in women in comparison to men (p <0.05). These reference ranges were similar to those derived from other African countries but lower than those recorded in France and in USA. This underscores the need for such comprehensible establishment of reference values for limited resources countries. Our study provides the first cholesterol sub-fractions (HDL2 and HDL3) reference ranges for interpretation of laboratory results for cardiovascular risk management in Burkina Faso.

High density lipoprotein subfractions: isolation, composition, and their duplicitous role in oxidation

The plasma HDLs represent a major class of cholesterol-transporting lipoprotein that can be divided into two distinct subfractions, HDL(2) and HDL(3), by ultracentrifugation. Existing methods for the subfractionation of HDL requires lengthy ultracentrifugations, making them unappealing for large-scale studies. We describe a method that subfractionates HDL from plasma in only 6 h, representing a substantial decrease in total isolation time. The subfractions so isolated were assessed for a variety of lipid and protein components, in addition to their susceptibility to oxidation, both alone and in combination with VLDL and LDL. We report for the first time a prooxidant role for HDL during VLDL oxidation, in which HDL donates preformed hydroperoxides to VLDL in a cholesteryl ester transfer protein (CETP)-dependent process. Examination of the participation of HDL in LDL oxidation has reinforced its classic role as a potent antioxidant. Furthermore, we have also implicated the second major HDL-associated enzyme, LCAT, in these processes, whereby it acts as a potent prooxidant during VLDL oxidation but as an antioxidant during LDL oxidation. Thus, we have identified a potentially duplicitous role for HDL in the pathogenesis of atherosclerosis, attributable to both CETP and LCAT.

Effect of L-carnitine on the serum lipoproteins and HDL-C subclasses in hemodialysis patients

AIMS

Following carnitine administration a decrease in plasma levels of triglyceride (TG) and increase in total high-density lipoprotein cholesterol (HDL-C) has been reported. Our hypothesis was that it also improves the HDL2/HDL3 ratio, symptomatic intradialytic hypotension, and anemia in hemodialysis (HD) patients.

METHODS

Forty HD patients with a mean (+/- SD) age of 53 +/- 13 years were treated with 500 mg/day carnitine taken orally for 2 months. Patients were used as their own controls (before treatment). Lipid and lipoproteins were determined by Alcyon Abbott autoanalyzer. HDL subclasses were measured by magnesium precipitation after fractionation with dextran sulfate. Hemoglobin, hematocrit and serum albumin were measured by standard methods. The results were analyzed by SPSS 11.05.

RESULTS

We found a significant decrease in serum TG (2.22 +/- 0.99 vs. 1.93 +/- 1.07 mmol/l, p < 0.01) and VLDL-C (0.93 +/- 0.36 vs. 0.81 +/- 0.34 mmol/l, p = 0.01) and a marked increase in HDL-C (0.9 +/- 0.16 vs. 1.06 +/- 0.24 mmol/l, p < 0.05), HDL2-C (0.17 +/- 0.06 vs. 0.27 +/- 0.14 mmol/l, p < 0.05) and albumin (37 +/- 4 vs. 42 +/- 5 g/l, p = 0.01) levels. The serum levels of total cholesterol (4.61 +/- 0.89 vs. 4.5 +/- 0.95 mmol/l, p = 0.1), LDL-C (2.78 +/- 0.85 vs. 2.6 +/- 0.89 mmol/l, p > 0.05), HDL3-C (0.73 +/- 0.1 vs. 0.79 +/- 0.17 mmol/l, p > 0.05), hemoglobin, hematocrit, and intradialytic blood pressure did not change after the treatment.

CONCLUSION

Treatment with 500 mg/day carnitine taken orally for 2 months reduces serum levels of TG and VLDL-C, and increases HDL-C, HDL2-C and albumin in HD patients.

Postprandial reverse cholesterol transport in type 2 diabetic patients: effect of a lipid lowering treatment

Deterioration of reverse cholesterol transport (RCT), an important anti-atherogenic process, may contribute to the largely unexplained severity of cardiovascular risk in type 2 diabetic patients. Among other relevant metabolic perturbations is the impairment in type 2 patients of the postprandial increase in RCT which, in normal subjects, is associated with the transfer to HDL of PL from lipolyzed chylomicrons. We have explored the possibility that improvement of postprandial lipolysis by bezafibrate might also restore the stimulated level of postprandial RCT. Twelve male patients (HbA1c 7.6 +/- 1.6% triglycerides (TG) 4.5 +/- 2.4 mmol/l) were treated for 4 weeks with 400 mg bezafibrate and compared with seven age-matched controls. Lipoproteins were analyzed over 8 h after a 1000 Kcal fat load (80% lipid), serum mediated cholesterol efflux was evaluated using 3H-cholesterol labelled Fu5AH cells. Fasting efflux was lower in patients (17.9 +/- 3.3 vs 19.9 +/- 3.0 a. units, P < 0.05) and decreased postprandially in most instead of increasing, so that area under the time-curve (AUC) was 23% lower than in controls (140 +/- 23 vs 170 +/- 25 units x h, P < 0.001) The patients' HDL failed to acquire PL and gained TG in proportion to lipemia (r = 0.660, P < 0.001). Bezafibrate restored fasting efflux (19.6 +/- 3.6 units, P < 0.005 vs pretreatment) but not postprandial increase of efflux or HDL-PL. AUC of efflux was however improved to 155 +/- 23 units h (P < 0.02). Postprandial efflux related mainly to HDL-PL in controls and patients before treatment. HDL-TG emerged as a significant negative correlate common to all groups (r = -0.674, P < 0.001 8 h after the meal). Impairment of reverse cholesterol transport in diabetic patients might therefore be due to combined postprandial deficit of PL transfer and excess accumulation of TG in HDL. The significant improvement due to fibrate treatment might thus be related to the reduction of HDL-TG contents associated with the improvement of postprandial hyperlipemia.

Population frequency distributions of HDL, HDL(2), and HDL(3) cholesterol and apolipoproteins A-I and B in healthy men and women and associations with age, gender, hormonal status, and sex hormone use: the Stanford Five City Project

BACKGROUND

The purpose of this study is to present population-based frequency distribution data for several lipoprotein-related variables and to examine their associations with gender, age, menopausal status, and sex hormone use.

METHODS

High-density lipoprotein cholesterol (HDL-C), HDL(2)-C, HDL(3)-C, apolipoprotein (Apo) A-I, and Apo B were measured in a population-based sample of 1, 027 healthy adults from four California cities who participated in the 1989-1990 survey of the Stanford Five City Project. These data were examined cross-sectionally with sociodemographic and other related variables.

RESULTS

Relative to men, all of the HDL-related parameters-HDL-C, HDL(2)-C, HDL(3)-C, Apo A-I-were significantly higher and Apo B levels were significantly lower among women (P < 0. 001). Menopausal status was not associated with HDL-related parameters, but Apo B levels were higher in post- versus premenopausal women (P < 0.001). Among women, HDL-C and Apo A-I levels were higher in oral contraceptive and estrogen replacement therapy users (P = 0.003). Most of the significant findings remained statistically significant after adjusting for age, body mass index, smoking, energy expenditure, and alcohol intake.

CONCLUSIONS

These population-based data indicate that gender, menopausal status, and the use of sex hormones among women are associated with differential levels of one or more of HDL-C, HDL(2)-C, HDL(3)-C, Apo A-I, and Apo B, independent of age and a broad set of lifestyle factors.

A new liquid homogeneous assay for HDL cholesterol determination evaluated in seven laboratories in Europe and the United States

We evaluated a new liquid homogeneous assay for the direct measurement of high density lipoprotein cholesterol (HDL-C Plus) in seven laboratories. The assay includes two reagents which can be readily used in most available clinical chemistry analyzers. The total CVs of the new method were below 4.6% and the bias in relation to the designated comparison method was below 3.9%. The total error ranged between 4 to 7%. HDL-C values determined by this method were in good agreement with those obtained by the old homogeneous assay using lyophilized reagents, and other homogeneous and precipitation assays (0.944 < r < 0.996). The assay was linear up to at least 3.89 mmol/l HDL-C. Hemoglobin did not interfere, whereas in icteric samples slight deviations were observed. Lipemia up to 11.3 to 22.6 mmol/l triglycerides did not interfere with this homogeneous HDL-C assay. In samples of patients with paraproteinemia, discrepant results were seen. This liquid homogeneous HDL-C assay was easy to handle and produced similar results in all laboratories participating in this study. This method will enable clinical laboratories to reliably measure HDL-C for risk assessment of coronary heart disease.

Long-term variability of serum lipoprotein(a) concentrations in healthy fertile women

Lipoprotein(a) is a unique lipoprotein with atherothrombogenic properties. Although its blood concentration is mainly genetically determined, various factors exist which may cause variability. These may influence the clinical use of the results. We studied lipoprotein(a) biological variation by a rate nephelometric assay over a period of two years in a population of healthy fertile women. The study was performed in 12 volunteers, healthy subjects with various lipoprotein(a) concentrations, by monthly determinations during one year and a single determination one year later, together with measurements of total, high density lipoprotein and high density lipoprotein2 cholesterol, triglycerides and apolipoproteins A1 and B. The intra-individual variability of lipoprotein(a) ranged between 4 to 20%, with three subjects showing a coefficient of biological variation higher than 15%. In absolute terms, the difference between two determinations could represent 0.44 g/l or 50% of the mean value. This study suggests that physiological lipoprotein(a) variations should be taken into account for clinical purposes, especially in patients in need of thorough risk evaluation.