Smaller, denser LDL particles are not a risk factor for cardiovascular disease in healthy nonagenarian women of the Cremona Population Study

LDL particle heterogeneity, and its association with other established cardiovascular risk factors in a young Indian industrial population

OBJECTIVE

Low density lipoprotein (LDL) particles are heterogeneous in terms of size, density, chemical composition and electric charge with certain particle of LDL being more atherogenic than the others. The present study aimed to look at the LDL particle heterogeneity, particle size and association with other cardiovascular disease (CVD) risk factors in young Indian industrial population.

METHODOLOGY

600 employees of an industry of Delhi, aged 20-39 years were selected for the study. Data on demographics, individual characteristics associated with major risk factors of CVD, past medical history, clinical and anthropometric profile was collected. Fasting glucose, lipid profile, apolipoprotein (A1, B, and E), lipoprotein (a), high sensitive C-reactive protein (hsCRP) and insulin were estimated. LDL particle size was determined in ethylenediamminetetraacetate (EDTA) plasma by 3% polyacrylamide gel electrophoresis.

RESULT

We found a prevalence of small dense LDL phenotype (LDL size ≤ 26.3) in 27.4% of males and 24.0% of females. The mean waist circumference, blood pressure, triglycerides (TAG), cholesterol, hsCRP, apolipoprotein (A1, B and E) and insulin were higher in males whereas mean high density lipoprotein was higher in females. Females also had a significantly higher mean LDL particle diameter as compared to males.

CONCLUSION

TAG, physical activity and lipoprotein (a) correlated with small dense LDL in this young Indian population.

Small dense LDL and VLDL predict common carotid artery IMT and elicit an inflammatory response in peripheral blood mononuclear and endothelial cells

OBJECTIVE

The presence of small dense LDL has been associated with increased cardiovascular risk and with the progression of coronary and carotid atherosclerosis in case-control and prospective studies. The aim of this study was to investigate the relation between different lipoprotein subfractions with intima-media thickness of the common carotid artery in a free-living, healthy population, and to evaluate whether in patients with comparable LDL-C, the different lipoprotein subclasses differently affected the expression of chemokines, cytokines and adhesion molecules in peripheral blood mononuclear and endothelial cells.

METHODS AND RESULTS

The lipoprotein cholesterol profile and the LDL buoyancy (LDL-RF) were evaluated in a cohort of 156 healthy subjects randomly selected from the PLIC (Progressione Lesione Intimale Carotidea) study. The LDL-RF was directly and significantly correlated to weight, body mass index, waist, hip, waist/hip ratio, triglycerides, fasting glycemia and intima media thickness (IMT) of the common carotid artery and inversely related to HDL-C. After multivariate statistical analysis, IMT was independently associated with age, LDL-RF and HDL-C and among the lipoprotein subclasses, only those corresponding to triglyceride-rich lipoproteins (TGRL) and small dense LDL (sdLDL) independently predicted IMT variance. Peripheral blood mononuclear cells (PBMC) isolated from patients with the predominance of sdLDL (pattern B) had an increased mRNA expression of pro-inflammatory molecules compared to PBMC from patients with the predominance of large LDL (pattern A); in endothelial cells TGRL from pattern B subjects and much less those from pattern A induced the expression of pro-inflammatory genes while sdLDL from either pattern A or B subjects were less effective and showed comparable effects.

CONCLUSION

LDL-relative flotation rate significantly correlates with several cardiometabolic parameters. Furthermore cholesterol levels lipoprotein subfractions within the TGRL and sdLDL density range are independent predictors of IMT variance and are associated with a pro-inflammatory activation of PBMC and endothelial cells.

Significance of small dense low-density lipoproteins as coronary risk factor in diabetic and non-diabetic Korean populations

Small dense low-density lipoproteins (LDLs) have been associated with coronary heart disease (CHD) and type 2 diabetes in previous studies. However, the significance of small dense LDLs as a coronary risk factor for subjects with type 2 diabetes remains unclear. We measured mean LDL particle diameter by gradient gel electrophoresis (Quantimetrix Lipoprint™ LDL System) in 44 type 2 diabetes patients, 100 CHD patients, 35 CHD patients with type 2 diabetes and 88 age-matched control subjects. Mean LDL particle sizes were significantly smaller (p<0.05, Mann-Whitney test) in diabetes mellitus-only patients (25.7±0.8nm), CHD-only patients (25.2±1.4nm), and CHD patients with diabetes mellitus (24.9±1.6nm) than in controls (26.2±1.4nm). As for the mean LDL particle size, the prevalence of small dense LDLs (mean diameter ≤25.5nm) was higher (p<0.05, χ

Low-density lipoprotein subfractions and the long-term risk of ischemic heart disease in men: 13-year follow-up data from the Québec Cardiovascular Study

OBJECTIVE

The objective of the present study was to investigate the association between large and small low-density lipoprotein (LDL) and long-term ischemic heart disease (IHD) risk in men of the Quebec Cardiovascular Study.

METHODS AND RESULTS

Cholesterol levels in the large and small LDL subfractions (termed LDL-C> or =260A and LDL-C<255A, respectively) were estimated from polyacrylamide gradient gel electrophoresis of whole plasma in the cohort of 2072 men of the population-based Quebec Cardiovascular Study. All men were free of IHD at the baseline examination and followed-up for a period of 13 years, during which 262 first IHD events (coronary death, nonfatal myocardial infarction, and unstable angina pectoris) were recorded. Our study confirmed the strong and independent association between LDL-C<255A levels as a proxy of the small dense LDL phenotype and the risk of IHD in men, particularly over the first 7 years of follow-up. However, elevated LDL-C> or =260A levels (third versus first tertile) were not associated with an increased risk of IHD over the 13-year follow-up (RR=0.76; P=0.07).

CONCLUSIONS

These results indicated that estimated cholesterol levels in the large LDL subfraction were not associated with an increased risk of IHD in men and that the cardiovascular risk attributable to variations in the LDL size phenotype was largely related to markers of a preferential accumulation of small dense LDL particles.

Genetics of LDL particle heterogeneity

Substantial evidence exists suggesting that small, dense LDL particles are associated with an increased risk of coronary heart disease. This disease-related risk factor is recognized to be under both genetic and environmental influences. Several studies have been conducted to elucidate the genetic architecture underlying this trait, and a review of this literature seems timely. The methods and strategies used to determine its genetic component and to identify the genes have greatly changed throughout the years owing to the progress made in genetic epidemiology and the influence of the Human Genome Project. Heritability studies, complex segregation analyses, candidate gene linkage and association studies, genome-wide linkage scans, and animal models are all part of the arsenal to determine the susceptibility genes. The compilation of these studies clearly revealed the complex genetic nature of LDL particles. This work is an attempt to summarize the growing evidence of genetic control on LDL particle heterogeneity with the aim of providing a concise overview in one read.

Low-density-lipoprotein peak particle size in a Mediterranean population

BACKGROUND

The predominance of small, dense low-density lipoprotein (LDL) particles ('LDL phenotype B') has been associated with a three-fold increased risk of myocardial infarction, but the feasibility of the identification of small, dense LDL as independent predictors of coronary artery disease risk in population studies remains questioned. Design We evaluated the LDL peak particle size and its relation with other established risk factors for coronary heart disease in a group of 156 randomized subjects living on the Mediterranean island of Ustica (71 males and 85 women, range of age 20-69 years), representing approximately 30% of the total population.

RESULTS

The prevalence of LDL phenotype B subjects was low (approximately 15% in both men and women) and there was a clear trend for both genders in reducing the LDL peak particle size with age. Moreover, LDL phenotype B subjects had higher BMI values, prevalence of diabetes and plasma triglyceride (TG) levels and lower plasma HDL-C concentrations in comparison with LDL phenotype A individuals; in a multivariate analysis, plasma TG levels were the only variable independently associated with LDL peak particle size.

CONCLUSIONS

In this population, which appears to be somewhat protected by premature coronary artery disease, a low prevalence of the LDL pattern B was found in both men and women, and plasma TG could have a key role in regulating the LDL peak particle size. The follow up, still ongoing, will provide useful information on the predictive role of LDL peak particle size on cardiovascular risk, at least in a low-risk population.

Smallest LDL particles are most strongly related to coronary disease progression in men

OBJECTIVE

LDLs include particle subclasses that have different mobilities on polyacrylamide gradient gels: LDL-I (27.2 to 28.5 nm), LDL-IIa (26.5 to 27.2 nm), LDL-IIb (25.6 to 26.5 nm), LDL-IIIa (24.7 to 25.6 nm), LDL-IIIb (24.2 to 24.7 nm), LDL-IVa (23.3 to 24.2 nm), and LDL-IVb (22.0 to 23.3 nm in diameter). We hypothesized that the association between smaller LDL particles and coronary artery disease (CAD) risk might involve specific LDL subclasses.

METHODS AND RESULTS

Average 4-year onstudy lipoprotein measurements were compared with annualized rates of stenosis change from baseline to 4 years in 117 men with CAD. The percentages of total LDL and HDL occurring within individual subclasses were measured by gradient gel electrophoresis. Annual rate of stenosis change was related concordantly to onstudy averages of total cholesterol (P=0.04), triglycerides (P=0.05), VLDL mass (P=0.03), total/HDL cholesterol ratio (P=0.04), LDL-IVb (P=0.01), and HDL(3a) (P=0.02) and inversely to HDL(2)-mass (P=0.02) and HDL(2b) (P=0.03). The average annual rate in stenosis change was 6-fold more rapid in the fourth quartile of LDL-IVb (>or=5.2%) than in the first quartile (<2.5%, P=0.03). Stepwise multiple regression analysis showed that LDL-IVb was the single best predictor of stenosis change.

CONCLUSIONS

LDL-IVb was the single best lipoprotein predictor of increased stenosis, an unexpected result, given that LDL-IVb represents only a minor fraction of total LDL.

Understanding the physiological and functional consequences of menopause: the PROSALMEN study. PROgetto SALute MENopausa

BACKGROUND AND AIMS

Women live longer and are more often affected by disability and poor health than men. The mechanism underlying this sex-related "mortality-morbidity" paradox is still unclear but it has been suggested that the physiological and functional changes occurring during the menopausal transition play an important role. The aim of PROSALMEN (PROgetto SALute MENopausa: Health in Menopause Project) is to study in great detail how these changes affect the integrity and function of the physiologic subsystems that are relevant to the maintenance of an active and healthy life-style during the aging process.

METHODS

PROSALMEN is a cross-sectional comparison of age-matched pre- and post-menopausal women. Thirty post-menopausal women, aged 48-58 years, were enrolled in the study together with 30 age-matched pre-menopausal controls. A number of clinical, biological and functional parameters were collected assessing the integrity and level of function of the physiological subsystems that are important for mobility. Furthermore, we collected information on risk factors, medical conditions and symptoms that frequently develop or become clinically evident after menopause, including the most important elements of the classical post-menopausal syndrome.

CONCLUSIONS

This rich dataset will be used to start dissecting the causal pathway leading from menopause to damages in the musculoskeletal system and, in turn, to reduced physical function. The final goal is to understand how and to what extent changes in health behavior and pharmacological treatments in addition to hormone replacement therapy (HRT) may counteract these processes.

Triglyceride, small, dense low-density lipoprotein, and the atherogenic lipoprotein phenotype

This review provides an overview of the recent data evaluating triglyceride and low-density lipoprotein (LDL) size, two highly interrelated, genetically influenced, risk factors for cardiovascular disease (CVD). An examination of new epidemiologic studies continues to demonstrate that plasma triglyceride levels predict CVD. The first prospective study of the familial forms of hypertriglyceridemia has shown that relatives in familial-combined hyperlipidemia families are at increased risk for CVD mortality and that triglyceride levels predicted 20-year, CVD mortality among relatives in familial hypertriglyceridemia families. A meta-analysis of three, large-scale, prospective studies in men, and the first study to examine the correlation of LDL particle size distribution and vascular changes measured by B-mode ultrasound, add to growing evidence that small, dense LDL is atherogenic. Quantitative genetic analysis has recently shown substantial pleiotropic (common) genetic effects on triglyceride and LDL size. At least part of this may be explained by variation at the cholesterol ester transfer protein locus on chromosome 16, possibly through its role in reverse cholesterol transport. Taken together, these data provide new insights into the importance of triglyceride and LDL particle size for understanding genetic susceptibility to cardiovascular disease and its prevention.