Association between carotid intima-media thickness and low-density lipoprotein size and susceptibility of low-density lipoprotein to oxidation in asymptomatic members of familial combined hyperlipidemia families

Lipoprotein profile assessed by 1H NMR, BMI and blood pressure are associated with vascular alterations in children with familial hypercholesterolaemia

BACKGROUND AND AIMS

Children with familial hypercholesterolaemia (FH) have elevated low-density lipoprotein cholesterol (LDL-C) concentrations since birth, which increases the risk of cardiovascular disease in adulthood. Arterial injury and stiffness parameters, including carotid intima media thickness (cIMT), pulse wave velocity (PWV) and distensibility (DIST), can be detected early in childhood. We studied the associations between cIMT, PWV and DIST with the lipoprotein profile assessed by proton nuclear magnetic resonance (1H NMR) and with influential variables such as blood pressure (BP) or body mass index (BMI) in children with FH.

METHODS AND RESULTS

In this cross-sectional study, we included 201 children (96 with FH and 105 non-FH controls). Clinical history, physical examination and standard biochemical studies were performed. FH genetic testing was performed when clinically indicated. Carotid ultrasonography and an advanced lipoprotein profile by 1H NMR were performed. Multivariate and classification methods were used. There were no differences between cIMT, PWV and DIST between FH and non-FH children. FH children presented more total LDL and large, medium and small particles. Small LDL particles, BMI and systolic BP determined the presence of pathological IMT in the FH group. LDL size, high-density lipoproteins and very low-density lipoprotein particles together with blood pressure determined the presence of pathological arterial wall elasticity.

CONCLUSIONS

Alterations in lipoprotein parameters assessed by are associated with early structural and functional arterial characteristics in children with FH. BMI and BP act as boosting factors. Cardiovascular prevention should start early in children with FH, encompassing all components of a healthy lifestyle.

Carotid Doppler findings among patients admitted with stroke in two tertiary care facilities in Uganda: A Hospital-based Cross-sectional Study

Background

Carotid Atherosclerotic Disease (CAD) Doppler findings including carotid artery stenosis, thickened intima media thickness, and high-risk atherosclerotic plaques are associated with increased risk of stroke and symptomatic cerebrovascular disease. However, few studies have explored these Doppler characteristics among stroke patients in Africa. This study, therefore, investigates these carotid artery Doppler characteristics among stroke patients in Uganda.

Methods

A hospital-based cross-sectional study of 95 stroke patients attending two national referral hospitals in Uganda between March and July 2022. Following the caption of their sociodemographic and clinical characteristics, they underwent Doppler sonography of the extracranial carotid arteries using a standard carotid Doppler protocol. Multivariate logistic regression was used to determine factors associated with abnormal carotid Doppler parameters (i.e., carotid intima-media thickness, carotid stenosis).

Results

The mean age of the study participants was 61 ± 13 years with 60% (57/95) of the participants being male. Most participants had an ischemic stroke (67%), hypertension (76.4%), and used alcohol (58.9%). The prevalence of significant carotid stenosis in participants with ischemic stroke was 12.5% (8/64) (i.e., 7.8% had severe carotid stenosis and 4.7% had moderate stenosis). The prevalence of high carotid intima media thickness (CIMT) and atherosclerotic plaques were 31.6% (30/95) and 26.3% (25/95), respectively. Most atherosclerotic plaques were echogenic. Age above 60 years (adjusted odds ratio [aOR] = 5.2, 95% Confidence Interval [CI]:1.97-14; p < 0.010), high low-density lipoprotein cholesterol (aOR = 4.2, 95% CI: 1.29-8.79; p = 0.013) increased the likelihood of having abnormal CIMT.

Conclusion

The burden of carotid atherosclerotic disease is increasing among stroke patients in Uganda. Large-scale epidemiological studies are needed to further profile the disease in high risk populations.

Lipoprotein particle number and size predict vascular structure and function better than traditional lipids in adolescents and young adults

BACKGROUND

In adults, dyslipidemia is associated with higher carotid thickness and arterial stiffness, predictors of cardiovascular events. In young subjects, lipid concentrations have not been consistently associated with vascular measures.

OBJECTIVE

The objective of the study was to compare nuclear magnetic resonance (NMR) measures of lipoprotein particle number (low-density lipoprotein [LDL] particle, low-density lipoprotein [HDL] particle, very low-density lipoprotein [VLDL] particle) and size (LDL size, HDL size, and VLDL size) to determine if they were associated with vascular measures more strongly than lipid concentrations (LDL cholesterol, HDL cholesterol, and triglyceride [TG]).

METHODS

We evaluated 214 lean (L), 228 obese (O), and 214 diabetic (T2DM) subjects aged 10 to 24 years (33% male and 39% Caucasian). Cardiovascular risk factors, vascular structure, and arterial stiffness were measured. General linear models were constructed including demographics, risk factors, and traditional or NMR lipid parameters. A composite vascular function score was developed as the outcome in receiver operator characteristic scores for determining which lipid parameter was superior in predicting vascular damage.

RESULTS

Risk factors worsened from L to O to T. However, LDL cholesterol was similar in O and T, whereas LDL size differentiated the 3 groups (T > O > L, P ≤ .0001). Models demonstrated the superiority of NMR values, which entered for all but 1 vascular outcome and explained more of the variance than traditional lipid concentrations. Receiver operator characteristic curves demonstrated that NMR values were superior in predicting vascular outcomes. Models stratified by race were similar but cutpoints predicting vascular outcomes differed by race for TG, TG/HDL, and VLDL.

CONCLUSION

Lipoprotein particle number and size are more strongly related to vascular structure and function than traditional lipid values. NMR lipid measures may be a better indicator of risk for target organ damage than traditional lipid measures in adolescents and young adults.

Impact of menopause and diabetes on atherogenic lipid profile: is it worth to analyse lipoprotein subfractions to assess cardiovascular risk in women?

Cardiovascular disease is the leading cause of death in women at advanced age, who are affected a decade later compared to men. Cardiovascular risk factors in women are not properly investigated nor treated and events are frequently lethal. Both menopause and type 2 diabetes substantially increase cardiovascular risk in the female sex, promoting modifications on lipid metabolism and circulating lipoproteins. Lipoprotein subfractions suffer a shift after menopause towards a more atherogenic lipid profile, consisted of hypertriglyceridemia, lower levels of both total high density lipoprotein (HDL) and its subfraction HDL2, but also higher levels of HDL3 and small low-density lipoprotein particles. This review discusses the impact of diabetes and menopause to the lipid profile, challenges in lipoprotein subfractions determination and their potential contribution to the cardiovascular risk assessment in women. It is still unclear whether lipoprotein subfraction changes are a major driver of cardiometabolic risk and which modifications are predominant. Prospective trials with larger samples, methodological standardizations and pharmacological approaches are needed to clarify the role of lipoprotein subfractions determination on cardiovascular risk prediction and intervention planning in postmenopausal women, with or without DM.

Multiplatform serum metabolic phenotyping combined with pathway mapping to identify biochemical differences in smokers

Aim: Determining perturbed biochemical functions associated with tobacco smoking should be helpful for establishing causal relationships between exposure and adverse events. Results: A multiplatform comparison of serum of smokers (n = 55) and never-smokers (n = 57) using nuclear magnetic resonance spectroscopy, UPLC–MS and statistical modeling revealed clustering of the classes, distinguished by metabolic biomarkers. The identified metabolites were subjected to metabolic pathway enrichment, modeling adverse biological events using available databases. Perturbation of metabolites involved in chronic obstructive pulmonary disease, cardiovascular diseases and cancer were identified and discussed. Conclusion: Combining multiplatform metabolic phenotyping with knowledge-based mapping gives mechanistic insights into disease development, which can be applied to next-generation tobacco and nicotine products for comparative risk assessment.

Relationship between carotid artery intima-media thickness and small dense low-density lipoprotein cholesterol concentrations measured by homogenous assay in Japanese subjects

BACKGROUND

Small dense low-density lipoprotein cholesterol (sdLDL-C) concentrations correlate more strongly with coronary heart disease than other LDL-C and large LDL particle concentrations. We investigated the association between carotid artery intima-media thickness (IMT) and sdLDL-C concentrations in Japanese subjects.

METHODS

Carotid artery IMT, blood pressure (BP), fasting plasma sdLDL-C, glucose metabolism, lipid, and C-reactive protein concentrations were measured in 97 native Japanese subjects. Carotid artery IMT was assessed by ultrasonography, and sdLDL-C concentrations were measured by a homogenous assay. Pearson's correlation coefficient analyses and multiple regression analyses were used to examine the relationships between carotid artery IMT values, sdLDL-C values, and other clinical variables.

RESULTS

After multiple regression analysis, including age, sex, body mass index, systolic BP, diastolic BP, fasting plasma glucose, HbA1c, estimated glomerular filtration rate (eGFR), total-C, high-density lipoprotein (HDL)-C, triglyceride, LDL-C, non-HDL-C, large buoyant LDL-C, and sdLDL-C, carotid artery IMT remained significantly associated with age, systolic BP, diastolic BP, and sdLDL-C, whereas sdLDL-C remained significantly associated with age, total-C, HDL-C, triglycerides, and carotid artery IMT.

CONCLUSIONS

When measured by a homogenous assay, carotid artery IMT may have a closer relationship with sdLDL-C concentrations than other lipid parameters in Japanese subjects. sdLDL-C may be a potentially useful risk marker when assessing carotid artery IMT in Japanese subjects.

Modified low density lipoprotein and lipoprotein-containing circulating immune complexes as diagnostic and prognostic biomarkers of atherosclerosis and type 1 diabetes macrovascular disease

In atherosclerosis; blood low-density lipoproteins (LDL) are subjected to multiple enzymatic and non-enzymatic modifications that increase their atherogenicity and induce immunogenicity. Modified LDL are capable of inducing vascular inflammation through activation of innate immunity; thus, contributing to the progression of atherogenesis. The immunogenicity of modified LDL results in induction of self-antibodies specific to a certain type of modified LDL. The antibodies react with modified LDL forming circulating immune complexes. Circulating immune complexes exhibit prominent immunomodulatory properties that influence atherosclerotic inflammation. Compared to freely circulating modified LDL; modified LDL associated with the immune complexes have a more robust atherogenic and proinflammatory potential. Various lipid components of the immune complexes may serve not only as diagnostic but also as essential predictive markers of cardiovascular events in atherosclerosis. Accumulating evidence indicates that LDL-containing immune complexes can also serve as biomarker for macrovascular disease in type 1 diabetes.

Influence of metabolic syndrome superposition on familial combined hyperlipoproteinemia cardiovascular complication rate

INTRODUCTION

Familial combined hyperlipoproteinemia (FCHL) is a very common and aggressive genetic mixed hyperlipoproteinemia, with many features similar to that of the metabolic syndrome (MS). We aimed to evaluate whether the presence of the MS per se could account for a significant part of the elevated cardiovascular disease (CVD) risk associated with FCHL.

MATERIAL AND METHODS

A retrospective cross-sectional evaluation of MS features' influence on CVD prevalence in a large sample of adult Italian FCHL affected patients (64 familial clusters; 867 subjects) was carried out.

RESULTS

Age is associated with early cardiovascular complications, both in men (OR 1.08, 95% CI: 1.05-1.11, p < 0.0001) and in women (OR 1.09, 95% CI: 1.04-1.13, p = 0.0001). No MS component appears to be related to cardiovascular complications in men, whilst only low plasma high-density lipoprotein cholesterol (HDL-C) shows such a relation in women. Among non-MS parameters, only low-density lipoprotein cholesterol (LDL-C) and lipoprotein(a) (Lp(a)) plasma levels are significantly associated with early cardiovascular complications in male FCHL patients (LDL-C: OR 2.24, 95% CI: 1.02-4.91, p = 0.04; Lp(a): OR 4.64, 95% CI: 1.85-11.62, p = 0.001), but not in women (LDL-C: OR 1.83, 95% CI 0.53-6.34, p = 0.34; Lp(a): OR 3.65, 95% CI: 0.89-14.97, p = 0.07).

CONCLUSIONS

Our data support the hypothesis that MS is not associated with a higher prevalence of cardiovascular complications in FCHL affected subjects, probably because of the strongest risk increase associated with the FCHL itself.

Serum uric acid: marker for atherosclerosis as it is positively associated with "atherogenic index of plasma"

CONTEXT

Serum uric acid (SUA) has been known to be associated with cardiovascular diseases. "Atherogenic index of plasma" (AIP) is considered a very sensitive predictor of future cardiovascular events.

OBJECTIVES

This study was conducted to analyse the association of AIP with SUA and various other lipid parameters.

METHODS

Parameters were measured on a fully automated analyser using standard reagent kits in a retrospective study involving 248 male Indian subjects between 40 to 59 years of age.

RESULTS

AIP correlates: moderately with TC/HDL-C (r = 0.47, p < 0.0001); to a lesser extent but comparably (r = 0.2, p < 0.01) with SUA, LDL-C/HDL-C and TC; negligibly with LDL-C and age.

DISCUSSION AND CONCLUSION

As SUA is positively associated with AIP it can be used as a supplementary marker for atherosclerosis/CVD in upper-middle-aged men.

Carotid atherosclerosis and lipoprotein particle subclasses in familial hypercholesterolaemia and familial combined hyperlipidaemia

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) and familial combined hyperlipidaemia (FCH) are common atherogenic disorders with great variability in cardiovascular disease (CVD). No direct atherosclerosis burden comparisons have been performed between FH and FCH in relation to lipoprotein particle distribution.

METHODS AND RESULTS

Risk factors and three measures of carotid intima-media thickness (IMT) in both sides were determined in 572 FH, 250 FCH and 200 controls. Lipoproteins were assessed by nuclear magnetic resonance (NMR) spectroscopy. Compared with controls, IMT measures were increased in FH and FCH. FCH had the highest adjusted mean-maximum IMT. FH had twice low-density lipoprotein (LDL) particles than controls, but similar LDL subclass size and distribution. FCH subjects also had increased LDL particles and the highest number of small LDL (1519 ± 731 nmol l(-1) vs. 887 ± 784 nmol l(-1) in FH and 545 ± 409 nmol l(-1) in controls). Age, gender, cholesterol/high-density lipoprotein (HDL) ratio, smoking and systolic blood pressure were independently associated with IMT in FH (r(2) = 0.38). The same variables, except cholesterol/HDL ratio, were associated with IMT in FCH (r(2) = 0.40). Among NMR lipoproteins, only VLDL and chylomicrons increased IMT prediction in FCH by 0.8%.

CONCLUSION

FH and FCH subjects show increased carotid atherosclerosis in relation to classical risk factors. Lipoprotein subclasses do not substantially contribute to IMT variability.

Impact of low-and high-density lipoprotein cholesterol levels on carotid intima-media thickness differs by smoking status in middle-aged men

AIM

Cigarette smoking is a strong risk factor for atherosclerotic disease; however, it remains unclear whether the impact of other risk factors differs by smoking status. The aim of this study was to investigate this issue, especially with regard to low-density and high-density lipoprotein (LDL/HDL) levels.

METHODS

In total, 448 healthy, middle-aged men (aged 37 to 61) participated in this study. Smoking habits were recorded, carotid intima-media thickness (IMT) was measured by B-mode ultrasound, and serum lipids and other biochemical parameters were determined from fasted blood samples.

RESULTS

Among the overall subjects, multivariate regression analyses showed that IMT was significantly associated with age (p < 0.0001 for mean IMT, p= 0.002 for max IMT), body mass index (BMI, mean IMT, p= 0.028), LDL-C levels (mean/max IMT, p= 0.001), HDL-C levels (max IMT, p= 0.022) and current smoking habit (mean IMT, p=0.012). Subgroup analyses according to smoking status revealed that LDL-C levels were significantly associated with mean/max IMT in current smokers (p=0.001) but not in ex- or nonsmokers (never smoked subjects). After adjusting for age, BMI, systolic blood pressure, hemoglobin A1c and serum lipids, mean IMT respectively increased and decreased progressively across LDL-C and HDL-C quartiles (p= 0.004 and 0.045) in the overall subjects. These associations were observed in current smokers (p= 0.01) but not in ex- or nonsmokers for LDL-C, and were observed in ex- and nonsmokers (p= 0.025, 0.017, respectively) but not in current smokers for HDL-C.

CONCLUSION

The impact of LDL-C/HDL-C levels on carotid IMT differs by smoking status. These observations imply that distinct mechanisms are involved in the (anti) atherogenesis of LDL/HDL according to smoking status.

Low-density lipoprotein particle number predicts coronary artery calcification in asymptomatic adults at intermediate risk of cardiovascular disease

BACKGROUND

Clinicians require more discriminating measures of cardiovascular risk than those currently used in most clinical settings. A promising avenue of research concerns the relationship of low-density lipoprotein (LDL) subfractions to subclinical atherosclerosis.

OBJECTIVE

To assess cross-sectional associations between subfractions of LDL cholesterol and coronary artery calcification (CAC).

METHODS

The study sample comprised 284 asymptomatic clinic patients who were at intermediate risk of cardiovascular disease, aged 40-69 years, who were not taking a statin or niacin. Lipoprotein subclass measures were obtained by the use of proton nuclear magnetic resonance spectroscopy. CAC was assessed with computed tomography angiography (CTA). The analyses modeled the presence or absence of CAC.

RESULTS

Total LDL particle number (LDL-P) had a stronger association with CAC than the traditional lipoprotein measures. Patients in the highest tercile of total LDL-P (1935-3560 nmol/L) were 3.7 times more likely to exhibit coronary artery calcification as those in the lowest tercile (620-1530 nmol/L). The independent effects of small LDL-P remained significant after adjustment for LDL-cholesterol, high-density lipoprotein (HDL), triglycerides, non-HDL, and large LDL-P. HDL and non-HDL were not significant, independent predictors of CAC.

CONCLUSION

Small LDL-P was a strong, independent predictor of the presence of CAC. Large prospective studies are needed to examine the effect of LDL particle number and size on coronary artery calcification.

Relation among lipoprotein subfractions and carotid atherosclerosis in Alaskan Eskimos (from the GOCADAN Study)

Studies have been inconsistent regarding whether lipoprotein particle subfraction measures are useful indicators of cardiovascular risk. The present study evaluated the relation between lipoprotein particle concentrations and size, analyzed using nuclear magnetic resonance spectroscopy and measures of carotid atherosclerosis in a population with high cardiovascular risk but little hyperlipidemia. In this cross-sectional, population-based sample of Alaska Eskimos >or=35 years old (n = 656), a greater carotid intimal medial thickness was associated with greater low-density lipoprotein (LDL) cholesterol (p = 0.03) and total LDL particle concentration (p = 0.04), independently of other traditional risk factors. The effects of LDL cholesterol and LDL particle concentration on intimal medial thickness were additive (p = 0.015). Carotid plaque was associated with greater levels of LDL cholesterol (p = 0.01), greater concentrations of large LDL particles (p = 0.003), and a reduction in the size of the very-low-density lipoprotein particles (p = 0.03). The effects of LDL cholesterol and large LDL particles on the plaque score were additive. In conclusion, the carotid intimal medial thickness was associated with greater LDL particle concentrations. The association was strongest in those with greater LDL cholesterol levels. Plaque was associated with greater concentrations of LDL cholesterol, large LDL particles, and smaller very-low-density lipoprotein particles. It might be beneficial to determine the lipoprotein subfractions in populations with little hyperlipidemia.

Atherogenic dyslipidemia and oxidative stress: a new look

Although results from in vitro studies and clinical trials demonstrate strong associations between oxidative stress and cardiovascular risk, to date still no convincing data are available to suggest that treatment with antioxidants might reduce vascular events. Oxidative modifications of low-density lipoproteins (LDL) represent an early stage of atherosclerosis, and small, dense LDL are more susceptible to oxidation than larger, more buoyant particles. Oxidized LDL are independent predictors of subclinical and clinical atherosclerosis. Recent studies suggested that novel therapeutic strategies may take into account the removal of such particles from circulation. Future research is required to explore the potential synergistic impact of markers of oxidative stress and atherogenic dyslipidemia, particularly small dense LDL, on cardiovascular risk.

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.

Relationship of abdominal visceral and subcutaneous adipose tissue with lipoprotein particle number and size in type 2 diabetes

OBJECTIVE

Insulin resistance and type 2 diabetes are associated with an atherogenic lipoprotein profile. We examined the role of visceral and subcutaneous fat depots, independent of BMI, on the dyslipidemia associated with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 382 subjects with type 2 diabetes underwent abdominal computed tomography to evaluate subcutaneous (SAT) and visceral adipose tissue (VAT) distribution and had anthropometric measurements to determine BMI and waist and hip circumference. Fasting blood was obtained for lipoprotein particle number and size using nuclear magnetic resonance spectroscopy. The relationship of lipoprotein particle number and size with BMI, SAT, and VAT was examined using multivariable regression models adjusted for age, sex, diabetes therapy, duration of diabetes, smoking, statin use, and A1C levels. The relation of VAT to lipoprotein particle number and size was further evaluated after the addition of BMI, BMI plus SAT, or BMI plus homeostatis is model assessment of insulin resistance (HOMA-IR) to the model.

RESULTS

VAT was positively related to VLDL particle number (P < 0.0001), LDL particle number (P < 0.01), and VLDL size (P < 0.0001) and negatively related to LDL size (P < 0.0001) and HDL size (P < 0.0001). These relationships remained unchanged after addition of BMI and SAT to the model. After addition of HOMA-IR, VAT remained positively related to VLDL particle number (P < 0.0001) and size (P < 0.01) and negatively related to LDL and HDL particle size (P < 0.0001 for both comparisons). Neither BMI nor SAT was independently related to lipoprotein parameters.

CONCLUSIONS

In patients with type 2 diabetes, higher VAT independent of BMI was associated with higher VLDL and LDL particle number, larger VLDL particles, and smaller LDL and HDL particles. This lipoprotein pattern has been associated with increased risk for atherosclerosis and cardiovascular disease.

Small dense low-density lipoprotein cholesterol concentration and carotid atherosclerosis

Low-density lipoprotein cholesterol (LDL-C) and the small dense LDL (SdLDL) phenotype are both predictors for ischemic heart disease. We examined whether cholesterol of SdLDL (SdLDL-C) is more closely associated with carotid artery intima-media thickness (CA-IMT), a surrogate measure of atherosclerosis, than LDL-C and other lipid parameters. The subjects were 326 consecutive participants including those with dyslipidemia, diabetes mellitus, hypertension, chronic kidney disease, and smokers. SdLDL-C was quantified by a newly developed precipitation method, and CA-IMT by high-resolution B-mode ultrasound. In univariate analysis, CA-IMT was most strongly correlated with SdLDL-C (Spearman's r=0.441, P<0.001), followed by apolipoprotein (apo) B, LDL-C, non-high-density lipoprotein cholesterol (Non-HDL-C), and plasma triglycerides (TG). HDL-C and apo A-I correlated inversely with CA-IMT. Non-lipid variables that were associated with CA-IMT were age, sex, presence of diabetes mellitus, presence of hypertension, estimate glomerular filtration rate (eGFR), and C-reactive protein (CRP). Even after adjustment for age, sex, diabetes mellitus, hypertension, smoking, eGFR and CRP, the positive association of CA-IMT with SdLDL-C remained significant, and again stronger than the associations with others lipid parameters. Further analyses revealed that the level of SdLDL-C was elevated in subgroups of the subjects including men, older subjects, smokers, those with higher CRP levels, those with diabetes mellitus, and hypertensive patients. These results indicate that SdLDL-C was the best marker of carotid atherosclerosis among the lipid parameters tested, and suggest that quantitative measurement of SdLDL-C gives useful information in the risk assessment for atherosclerotic disease.

Intima-media thickness of the carotid artery and the distribution of lipoprotein subclasses in men aged 40 to 49 years between whites in the United States and the Japanese in Japan for the ERA JUMP study

In men in the post-World War II birth cohort, that is, men aged 40 to 49 years, whites in the United States had significantly higher levels of intima-media thickness of the carotid arteries (IMT) than the Japanese in Japan (Electron-Beam Tomography and Risk Assessment Among Japanese and US Men in the Post World War II Birth Cohort [ERA JUMP] study). The difference remained after adjusting for traditional risk factors. Primary genetic effects are unlikely, given the degree to which IMT is increased in the Japanese who migrated to the United States. We investigated whether the differences in the distributions of lipoprotein subclasses explain the difference in IMT between the 2 populations. We examined population-based samples of 466 randomly selected men aged 40 to 49 years (215 whites from Allegheny County, Pennsylvania, and 241 Japanese from Kusatsu, Shiga, Japan). Lipoprotein subclasses were determined by nuclear magnetic resonance (NMR) spectroscopy. The whites had significantly higher levels of large very low-density lipoprotein particles and significantly lower levels of large high-density lipoprotein particles than the Japanese, whereas the 2 populations had similar levels of small low-density lipoprotein particles. The 2 populations had similar associations of IMT with NMR lipoproteins. Adjusting for NMR lipoproteins did not attenuate the significant difference in IMT between the 2 populations (0.671 +/- 0.006 mm for the whites and 0.618 +/- 0.006 mm for the Japanese, P = .01, mean +/- SE). Differences in the distributions of NMR lipoproteins between the 2 populations did not explain the higher IMT in the whites.

Who needs to care about small, dense low-density lipoproteins?

BACKGROUND

Increasing evidence suggest that the 'quality' rather than only the 'quantity' of low-density lipoprotein (LDL) exerts a great influence on the cardiovascular risk. Small, dense LDL seem to be an important predictor of cardiovascular events and progression of coronary artery disease (CAD) and their predominance has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III.

DISCUSSION

Some studies showed in past years that small, dense LDL are usually elevated in patients at very high cardiovascular risk, such as those with CAD and type 2 diabetes. More recently elevated levels of these particles have been found in other categories of patients at high cardiovascular risk, such as those with non-coronary forms of atherosclerosis (e.g. with carotid artery disease, aortic abdominal aneurysm and peripheral arterial disease) and metabolic diseases (with polycystic ovary syndrome and growth hormone deficiency); notably, in most of them, the predominance of small, dense LDL characterised their type of dyslipidaemia, alone or in combination with elevated triglycerides and reduced high-density lipoproteins cholesterol concentrations.

CONCLUSIONS

The therapeutical modulation of small, dense LDL have been shown to significantly reduce cardiovascular risk and weight reduction and increased physical activity may constitute first-line therapy. In addition, lipid-lowering drugs are able to favourably alter these particles and fibrates and nicotinic acid seem to be the most effective agents. Promising data are also available with the use of rosuvastatin, the latest statin introduced in the market, and ezetimibe, a cholesterol absorption inhibitor.

LDL particle subclasses, LDL particle size, and carotid atherosclerosis in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Previous studies showing that smaller low-density lipoprotein (LDL) size is associated with greater atherosclerotic risk did not adequately control for small and large LDL particle correlation.

METHODS AND RESULTS

We studied the association of lipoproteins measured by proton nuclear magnetic resonance spectroscopy with carotid intima-media thickness (IMT) in apparently healthy individuals (N = 5538, 38% White, 28% African American, 22% Hispanic, 12% Chinese). Small and large LDL particle concentrations (LDL-p) were inversely correlated (r = /-0.63, P < 0.0001). Controlling for risk factors but not for LDL subclass correlation, LDL size and small LDL-p separately were associated with IMT (-20.9 and 31.7 microm change in IMT per 1-S.D., respectively, both P < 0.001), but large LDL-p was not (4.9 microm, P = 0.27). When LDL subclasses were included in the same model, large and small LDL-p were both associated with IMT (36.6 and 52.2 microm higher IMT per 1-S.D., respectively, both P < 0.001; 17.7 and 11.6 microm per 100 nmol/L, respectively). LDL size was not significant after accounting for LDL subclasses and risk factors (P = 0.10).

CONCLUSION

Both LDL subclasses were significantly associated with subclinical atherosclerosis, with small LDL confounding the association of large LDL with atherosclerosis. Future studies of LDL size should account for the strong inverse correlation of LDL subclasses.

Increased plasma levels of oxysterols, in vivo markers of oxidative stress, in patients with familial combined hyperlipidemia: reduction during atorvastatin and fenofibrate therapy

Familial combined hyperlipidemia (FCHL), the most common inherited disorder of lipid metabolism, is associated with an increased risk of atherosclerosis that is not fully explained by the metabolic disturbances of these patients. Oxidative damage to lipid components accumulating in the plasma of FCHL patients might contribute to explaining this lack of evidence. Cholesterol is one of the preferential targets of oxidation in LDL and this may contribute to setting a proatherogenetic phenotype in FCHL. We investigated plasma oxysterols (7-ketocholesterol and 7beta-hydroxycholesterol) and alpha-tocopherol as in vivo hallmarks of lipid-related oxidative stress. Oxidative stress hallmarks were measured in 45 FCHL patients and 54 sex- and age-matched healthy controls; in FCHL patients, oxidative stress and lipid profile parameters were also assessed in response to lipid-lowering drugs in a 24-week randomized, open-label trial with atorvastatin or fenofibrate. FCHL patients showed markedly increased levels of oxysterols (p < 0.001) and reduced alpha-tocopherol/total lipids (p < 0.001) compared to controls. These differences were independent of the presence of clinical atherosclerosis and persisted after correction for hyperlipidemia. Atorvastatin and fenofibrate significantly improved the lipid profile and caused a comparable decrease in plasma oxysterols, with the normalization of 7-ketocholesterol and a significant reduction of 7beta-hydroxycholesterol (p < 0.001). These drugs also decreased the ratio of alpha-tocopherol/total lipids by more than 30% (p < 0.001). In conclusion, FCHL patients showed increased hallmarks of cholesterol oxidation and decreased levels of alpha-tocopherol/total lipids. Atorvastatin and fenofibrate displayed comparable efficiency in decreasing oxysterols, but they further decreased lipid-corrected alpha-tocopherol levels in plasma. More research work is needed to understand the clinical meaning of these findings, which may help to understand the role of oxidative stress in FCHL and lipid-lowering therapy.

Small, dense low-density-lipoproteins and the metabolic syndrome

Small, dense low-density-lipoproteins (LDL) are associated with increased risk for cardiovascular diseases and diabetes mellitus and a reduction in LDL size has been reported in patients with coronary and non-coronary forms of atherosclerosis. LDL size has been accepted as an important predictor of cardiovascular events and progression of coronary artery disease as well as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. Small, dense LDL, with elevated triglyceride levels and low HDL-cholesterol concentrations, constitute the 'atherogenic lipoprotein phenotype (ALP)', a form of atherogenic dyslipidemia that is a feature of type 2 diabetes and the metabolic syndrome. LDL size and subclasses show specific alterations in patients with the metabolic syndrome that probably significantly increase their cardiovascular risk; however, so far it has not been recommended to incorporate LDL size measurements in treatment plans, when hypolipidemic therapies are installed. Patients with type 2 diabetes are at high cardiovascular risk and it is still on debate if the treatment goals may be identical or whether there are distinct groups with different cardiovascular risks and hence with different treatment goals. Measurements beyond traditional lipids, such as measurements on the presence of small, dense LDL in patients with the metabolic syndrome, may help to identify cardiovascular risk subgroups. In addition, it might be possible in the future to individualize hypolipidemic treatments if more than the traditional lipids are taken into account. LDL size measurement may potentially help to assess cardiovascular risk within the metabolic syndrome and adapt the treatment goals thereafter.

Technology Insight: ultrasound measurement of carotid plaque--patient management, genetic research, and therapy evaluation

Various methods have been used to quantify atherosclerosis, beginning in the mid-1980s with ultrasound measurement of carotid intima-media thickness (IMT), and going on to coronary calcification assessed by electron-beam CT, measurement of carotid plaque by ultrasound, and measurement of carotid wall thickness by MRI. In recent years, it has become clear that carotid IMT, coronary calcification and carotid plaque reflect biologically and genetically different aspects of the atherosclerotic process, and will respond differentially to therapy. IMT represents mainly hypertensive medial hypertrophy; this measure is more predictive of stroke than of myocardial infarction, and is only weakly associated with traditional coronary risk factors. Carotid plaque area, on the other hand, is more strongly associated with traditional risk factors, and is more predictive of myocardial infarction than of stroke. A quantitative trait, called 'unexplained atherosclerosis', expresses the extent to which an individual has excess carotid plaque not explained by traditional risk factors, or the extent to which an individual is protected from traditional risk factors. Unexplained progression of plaque is an even more powerful tool for genetic research, because age, which accounts for the greatest proportion of baseline plaque, has much less influence on the rate of progression. Compared with IMT, measurement of carotid plaque volume by three-dimensional ultrasound reduces by two orders of magnitude the sample size and duration of treatment needed to evaluate new therapies. Measurement of carotid plaque is, therefore, an important tool for patient management, genetic research and evaluation of new therapies for stroke prevention.

Clinical importance and therapeutic modulation of small dense low-density lipoprotein particles

The National Cholesterol Education Programme Adult Treatment Panel III accepted the predominance of small dense low-density lipoprotein (sdLDL) as an emerging cardiovascular disease (CVD) risk factor. Most studies suggest that measuring low-density lipoprotein (LDL) particle size, sdLDL cholesterol content and LDL particle number provides additional assessment of CVD risk. Therapeutic modulation of small LDL size, number and distribution may decrease CVD risk; however, no definitive causal relationship is established, probably due to the close association between sdLDL and triglycerides and other risk factors (e.g., high-density lipoprotein, insulin resistance and diabetes). This review addresses the formation and measurement of sdLDL, as well as the relationship between sdLDL particles and CVD. The effect of hypolipidaemic (statins, fibrates and ezetimibe) and hypoglycaemic (glitazones) agents on LDL size and distribution is also discussed.

The oxidative modification hypothesis of atherosclerosis: The comparison of atherogenic effects on oxidized LDL and remnant lipoproteins in plasma

A tremendous number of articles on oxidized LDL (Ox-LDL) and scavenger receptor in macrophage have been published since Steinberg proposed Ox-LDL hypothesis as the major cause of atherosclerosis. This hypothesis has provided strong support for the efficacy of LDL lowering drugs, indicating that lowering LDL means lowering Ox-LDL in vivo. This manuscript proposed a new oxidative modification hypothesis that remnant lipoproteins determined as remnant-like lipoprotein particles (RLP), not LDL are the major oxidized lipoproteins in plasma, resulting from the plasma concentration of these oxidized lipoproteins. Remnant lipoproteins may play a pivotal role for the initiation of atherosclerosis via lectin-like oxidized LDL receptor-1 (LOX-1) in endothelial cells. Isolated remnant lipoproteins were found to be oxidized or susceptible to be oxidized in plasma, not necessary to be further oxidized in vitro as Ox-LDL. High similarity of proatherogenic and proinflammatory properties of isolated Ox-LDL and remnant lipoporteins have been reported and predicted the presence of similar oxidized phospholipids in both lipoproteins as bioactive components. These results suggest the possibility that reducing plasma remnant lipoproteins rather than LDL should be the target for hyperlipidemic therapy especially in patients with metabolic syndrome for the prevention of endothelial dysfunction in the initiation of atherosclerosis.

Low-density lipoprotein size and cardiovascular prevention

Low-density lipoprotein (LDL) size appears to be an important predictor of cardiovascular events and progression of coronary artery disease, and the predominance of small, dense LDL has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. Yet, other authors have suggested that LDL subclass measurement does not add independent information to that conferred generically by LDL concentration and other standard risk factors. Therefore, the debate continues as to whether to measure LDL particle size for cardiovascular prevention and, if so, in which categories of patients. Since the therapeutic modulation of distinct LDL subspecies is of great benefit in reducing the risk of cardiovascular events, LDL size measurement should be extended as much as possible to patients at high risk of cardiovascular diseases.

Low-density lipoprotein size and cardiovascular risk assessment

A predominance of small, dense low-density lipoproteins (LDL) has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. LDL size seems to be an important predictor of cardiovascular events and progression of coronary heart disease and evidences suggests that both quality (particularly small, dense LDL) and quantity may increase cardiovascular risk. However, other authors have suggested that LDL size measurement does not add information beyond that obtained by measuring LDL concentration, triglyceride levels and HDL concentrations. Therefore, it remains debatable whether to measure LDL particle size in cardiovascular risk assessment and, if so, in which categories of patient. Therapeutic modulation of LDL particle size or number appears beneficial in reducing the risk of cardiovascular events, but no clear causal relationship has been shown, because of confounding factors, including lipid and non-lipid variables. Studies are needed to investigate the clinical significance of LDL size measurements in patients with coronary and non-coronary forms of atherosclerosis; in particular, to test whether LDL size is associated with even higher vascular risk, and whether LDL size modification may contribute to secondary prevention in such patients.

Small low-density lipoprotein and small low-density lipoprotein/total low-density lipoprotein are closely associated with intima-media thickness of the carotid artery in Type 2 diabetic patients

BACKGROUND

The intima-media thickness (IMT) of the carotid artery, as determined by ultrasonography, is useful for reflecting the extent of subclinical atherosclerosis. We investigated the relationship between IMT and the serum concentrations of small low-density lipoprotein (LDL) in diabetic patients.

METHODS

The study was conducted with 27 Type 2 diabetic patients (14 males and 13 females; mean age=62.6+/-8.3 years) and 12 age-matched healthy controls. The LDL subfraction was measured using a polyacrylamide gel electrophoresis method. Vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) concentrations were measured by an enzyme immunoassay. The IMT was expressed as the maximum IMT (Max-IMT) and average IMT (Ave-IMT) of the carotid artery, measured by ultrasonography.

RESULTS

Both the IMT and the small LDL concentrations were significantly increased in the diabetic patients compared with the healthy participants. The IMTs were significantly correlated with small LDL concentration and small LDL/total LDL more than LDL concentrations by multivariate analysis. The IMTs were not significantly correlated with the serum VEGF or PDGF concentrations. The patients with a larger IMT had a significantly higher prevalence of hypertension or ischemic heart disease than did the patients with a normal IMT.

CONCLUSIONS

The increased small LDL concentrations and small LDL/total LDL, in addition to total LDL concentrations, in Type 2 diabetic patients are closely associated with increased IMT of the carotid artery.

Pomegranate juice consumption for 3 years by patients with carotid artery stenosis reduces common carotid intima-media thickness, blood pressure and LDL oxidation

Dietary supplementation with polyphenolic antioxidants to animals was shown to be associated with inhibition of LDL oxidation and macrophage foam cell formation, and attenuation of atherosclerosis development. We investigated the effects of pomegranate juice (PJ, which contains potent tannins and anthocyanins) consumption by atherosclerotic patients with carotid artery stenosis (CAS) on the progression of carotid lesions and changes in oxidative stress and blood pressure. Ten patients were supplemented with PJ for 1 year and five of them continued for up to 3 years. Blood samples were collected before treatment and during PJ consumption. In the control group that did not consume PJ, common carotid intima-media thickness (IMT) increased by 9% during 1 year, whereas, PJ consumption resulted in a significant IMT reduction, by up to 30%, after 1 year. The patients' serum paraoxonase 1 (PON 1) activity was increased by 83%, whereas serum LDL basal oxidative state and LDL susceptibility to copper ion-induced oxidation were both significantly reduced, by 90% and 59%, respectively, after 12 months of PJ consumption, compared to values obtained before PJ consumption. Furthermore, serum levels of antibodies against oxidized LDL were decreased by 19%, and in parallel serum total antioxidant status (TAS) was increased by 130% after 1 year of PJ consumption. Systolic blood pressure was reduced after 1 year of PJ consumption by 12% [corrected] and was not further reduced along 3 years of PJ consumption. For all studied parameters, the maximal effects were observed after 1 year of PJ consumption. Further consumption of PJ, for up to 3 years, had no additional beneficial effects on IMT and serum PON1 activity, whereas serum lipid peroxidation was further reduced by up to 16% after 3 years of PJ consumption. The results of the present study thus suggest that PJ consumption by patients with CAS decreases carotid IMT and systolic blood pressure and these effects could be related to the potent antioxidant characteristics of PJ polyphenols.

Circulating Oxidized Low-Density Lipoprotein and Its Association With Carotid Intima-Media Thickness in Asymptomatic Members of Familial Combined Hyperlipidemia Families

OBJECTIVE

Oxidized low-density lipoprotein (Ox-LDL)is implicated in the pathogenesis of atherosclerosis. Circulating oxidation-specific epitopes on plasma Ox-LDL has been linked with coronary artery disease, but its determinants and its association with early development of atherosclerosis in familial combined hyperlipidemia (FCHL) has not been very well studied. This study aimed to investigate the determinants of the circulating Ox-LDL and the association between Ox-LDL and carotid intima-media thickness (IMT) in asymptomatic members of FCHL families.

METHODS AND RESULTS

Ox-LDL, susceptibility of LDL to oxidation in vitro, plasma 8-isoprostane and antioxidants, lipids and lipoproteins, LDL particle size, and carotid IMT were measured in 150 asymptomatic FCHL family members. Affected FCHL family members had reduced LDL particle size and lag time for LDL oxidation, increased plasma levels of Ox-LDL, increased plasma urate and alpha-tocopherol, and a trend for the increase of 8-isoprostane as compared with nonaffected FCHL. Ox-LDL was independently associated with serum LDL cholesterol, apoB, and 8-isoprostane in multivariate analysis but only univariately correlated with LDL particle size and lag time for LDL oxidation. In addition, Ox-LDL was significantly associated with carotid mean IMT independently of other clinical and biochemical variables in a multivariate model.

CONCLUSIONS

Serum LDL cholesterol, apoB levels, and 8-isoprostane were the most important determinants of Ox-LDL. Ox-LDL is independently associated with carotid IMT in asymptomatic FCHL family members and can be used as a marker of early atherosclerosis in FCHL.

Atherogenic Lipoprotein Particles in Atherosclerosis

The importance of low-density lipoprotein (LDL) cholesterol in the development of atherosclerosis has long been recognized, and LDL cholesterol remains the primary target of therapy for the prevention of coronary heart disease. Nevertheless, increasing research attention over the past decade has been devoted to the heterogeneity of LDL particles and the atherogenicity of lipids and lipoproteins other than LDL. Particularly atherogenic forms of LDL include small, dense LDL particles and oxidized LDL. All lipoproteins that contain apolipoprotein B, such as LDL, very-low-density lipoprotein, and intermediate-density lipoprotein, tend to promote atherosclerosis; however, these particles differ in their apolipoprotein and triglyceride content. High levels of plasma triglycerides increase the risk of acute coronary events. Lipoprotein(a) is now considered an independent risk factor in both men and women. Ultimately, better understanding of the roles of these lipid particles and subfractions in the initiation and progression of atherosclerosis may affect treatment decisions.

Small dense low-density lipoprotein and carotid atherosclerosis in relation to vascular dementia

Vascular dementia (VaD) and Alzheimer's disease (AD) are the most common causes of dementia in the elderly. The aim of this study was to investigate carotid atherosclerosis, serum lipid profiles, and atherogenic hormone levels in nondiabetic Japanese men with VaD or AD. Carotid artery intima-media thickness (IMT) and plaque, serum lipid and lipoprotein profiles, including low-density lipoprotein (LDL) particle size, as well as insulin-like growth factor-I (IGF-I, somatomedin C) and testosterone levels, were determined in 34 patients with AD, 37 patients with VaD, and 63 healthy male controls. Age, body mass index, systolic and diastolic blood pressure, and fasting plasma glucose, hemoglobin A(1c) (HbA(1c)), triglyceride, high-density lipoprotein (HDL)-cholesterol, and apolipoproteins (apo) A-I, B, and E levels did not differ significantly among the 3 groups. However, the mean value of carotid IMT, the frequency of atherosclerotic plaque deposition, the serum levels of LDL-cholesterol, lipoprotein(a), and lipid peroxides, and the incidence of small dense LDL (particle diameter </= 25.5 nm) were increased significantly in VaD patients compared with AD patients or controls. VaD patients had a close reverse correlation between carotid IMT and LDL particle diameter, which were statistically proven independent risk factors for VaD. In contrast, AD patients had significantly lower serum levels of IGF-I and testosterone than either VaD patients or controls. Our results indicate that VaD is associated with atherogenic dyslipidemia, in particular, small dense LDL and carotid atherosclerosis, whereas AD is associated with hyposomatomedinemia and hypogonadism rather than atherosclerosis.

An omega-3 polyunsaturated fatty acid concentrate increases plasma high-density lipoprotein 2 cholesterol and paraoxonase levels in patients with familial combined hyperlipidemia

A remarkable reduction of plasma concentrations of high-density lipoproteins (HDL), especially of the HDL(2) subfraction, is one of the typical lipoprotein alterations found in patients with familial combined hyperlipidemia (FCHL). Fourteen FCHL patients received 4 capsules daily of Omacor (an omega-3 polyunsaturated fatty acid [omega3 FA] concentrate providing 1.88 g of eicosapentaenoic acid [EPA] and 1.48 g of docosahexaenoic acid [DHA] per day; Pronova Biocare, Oslo, Norway) or placebo for 8 weeks in a randomized, double-blind, crossover study. Plasma triglycerides were 44% lower, and LDL cholesterol and apoliporpotein (apo)B were 25% and 7% higher after Omacor than placebo. HDL cholesterol was higher (+8%) after Omacor than placebo, but this difference did not achieve statistical significance. Omacor caused a selective increase of the more buoyant HDL(2) subfraction; plasma HDL(2) cholesterol and total mass increased by 40% and 26%, respectively, whereas HDL(3) cholesterol and total mass decreased by 4% and 6%. Both HDL(2) and HDL(3) were enriched in cholesteryl esters and depleted of triglycerides after Omacor. No changes were observed in the plasma concentration of major HDL apolipoproteins, LpA-I and LpA-I:A-II particles, lecithin:cholesterol acyltransferase (LCAT), and cholesteryl ester transfer protein (CETP). The plasma concentration of the HDL-bound antioxidant enzyme paraoxonase increased by 10% after Omacor. Omacor may be helpful in correcting multiple lipoprotein abnormalities and reducing cardiovascular risk in FCHL patients.

Associations of LDL size with in vitro oxidizability and plasma levels of in vivo oxidized LDL in Type 2 diabetic patients

AIMS

Oxidative modification of low-density lipoprotein (LDL) is believed to be a key step in the genesis of atherosclerotic lesions. The presence of small, dense LDL is associated with accelerated atherosclerosis and is common in diabetic patients. The aim of this study was to investigate the relationship of in vitro LDL oxidizability and circulating in vivo oxidized LDL with LDL particle size in Type 2 diabetic patients and healthy control subjects.

SUBJECTS AND METHODS

The study group consisted of 58 elderly well controlled Type 2 diabetic patients and 58 control subjects with normal glucose metabolism. LDL particle size was measured by high-performance gel-filtration chromatography. In vitro oxidizability of LDL was measured by monitoring conjugated diene formation and plasma levels of circulating oxidized LDL were determined by ELISA.

RESULTS

In vitro susceptibility of LDL to oxidation was not related to plasma levels of in vivo oxidized LDL, nor to LDL particle size. In the diabetic patients, but not in the control group, an inverse relation between LDL size and in vivo oxidized LDL was observed (r=-0.35, P=0.007). This relation was strengthened after controlling for LDL-cholesterol concentration (r=-0.52, P<0.001).

CONCLUSIONS

In agreement with the view that small, dense LDL accelerates atherosclerosis, an inverse relationship was observed between LDL size and circulating in vivo oxidized LDL in Type 2 diabetic patients. Our results also suggest that in vitro susceptibility to oxidation is not a suitable surrogate measure for in vivo LDL oxidation.

Hepatic lipase: a marker for cardiovascular disease risk and response to therapy

PURPOSE OF REVIEW

Hepatic lipase plays a key role in the metabolism of pro-atherogenic and anti-atherogenic lipoproteins affecting their plasma level as well as their physico-chemical properties. However, controversial evidence exists concerning whether hepatic lipase is pro or anti-atherogenic. The goal of this review is to summarize recent evidence that connects the enzyme to cardiovascular disease. The potential impact of genetic determinants of hepatic lipase activity in modulating both the development of coronary and carotid atherosclerosis will be discussed based on hepatic lipase proposed roles in lipoprotein metabolism.

RECENT FINDINGS

Twenty to 30% of individual variation of hepatic lipase activity is accounted for by the presence of a common polymorphism in the promoter region (-514 C to T) of the hepatic lipase gene (LIPC). This polymorphism, via its impact on hepatic lipase synthesis and activity, appears to contribute to (1) individual susceptibility to cardiovascular disease: the presence of the T allele (low hepatic lipase activity) may carry a marginally increased risk of atherosclerosis; (2) carotid plaque composition and individual susceptibility to cerebrovascular events: the presence of the C allele (high hepatic lipase activity) is associated with increased carotid intima-media thickness and abundance of macrophages in the carotid plaque (unstable plaque); and (3) response of cardiovascular disease patients to lipid-lowering therapy: patients with the CC genotype have the greatest clinical benefit from intensive lipid-lowering therapy.

SUMMARY

Convincing evidence shows that hepatic lipase plays a key role in remnant lipoprotein catabolism as well as in remodeling of LDL and HDL particles. The anti or pro-atherogenic role of hepatic lipase is likely to be modulated by the concurrent presence of other lipid abnormalities (i.e. increased LDL cholesterol levels) as well as by the genetic regulation of other enzymes involved in lipoprotein metabolism. Characterization of patients by their LIPC genotype will contribute to a better definition of individual risk of coronary and cerebrovascular events, specifically in patients with qualitative (small, atherogenic LDL and low HDL2 cholesterol) rather than quantitative lipid abnormalities for whom the routine lipid profile may underestimate the risk of coronary and cerebrovascular disease.

Familial combined hyperlipidemia plasma stimulates protein secretion by HepG2 cells: identification of fibronectin in the differential secretion proteome

The aim of this study was to evaluate whether soluble factors in plasma of familial combined hyperlipidemia (FCHL) patients affect hepatic protein secretion. Cultured human hepatocytes, i.e., HepG2 cells, were incubated with fasting plasma (20%, v/v, in DMEM) from untreated FCHL patients or normolipidemic controls. Overall protein secretion was 10-15% higher after incubation with FCHL plasma. This was specifically caused by an increase in four secreted proteins, with estimated sizes of 240, 180, 120, and <40 kD (P < 0.001, P < 0.006, P < 0.002, P < 0.02, respectively). The 240 kD protein in the secretion proteome was identified as fibronectin by mass spectrometry. Plasma fibronectin concentrations were elevated in FCHL patients, confirming biological relevance of these data. Overall protein secretion by HepG2 cells correlated with concentrations of triglycerides (r = 0.61, P < 0.001) in the applied plasma samples. VLDL+IDL isolated from FCHL patients, induced a higher protein secretion than lipoproteins isolated from controls (P < 0.001). Remarkably, secretion of apoB, the structural protein of VLDL, was stimulated to a similar extent by FCHL and control plasma. FCHL plasma did not induce excess secretion of apoB by HepG2 cells compared with control plasma. FCHL plasma did stimulate secretion of several distinct hepatic proteins, among which fibronectin was identified.

Clinical relevance of the biochemical, metabolic, and genetic factors that influence low-density lipoprotein heterogeneity

Traditional risk factors for coronary artery disease (CAD) predict about 50% of the risk of developing CAD. The Adult Treatment Panel (ATP) III has defined emerging risk factors for CAD, including small, dense low-density lipoprotein (LDL). Small, dense LDL is often accompanied by increased triglycerides (TGs) and low high-density lipoprotein (HDL). An increased number of small, dense LDL particles is often missed when the LDL cholesterol level is normal or borderline elevated. Small, dense LDL particles are present in families with premature CAD and hyperapobetalipoproteinemia, familial combined hyperlipidemia, LDL subclass pattern B, familial dyslipidemic hypertension, and syndrome X. The metabolic syndrome, as defined by ATP III, incorporates a number of the components of these syndromes, including insulin resistance and intra-abdominal fat. Subclinical inflammation and elevated procoagulants also appear to be part of this atherogenic syndrome. Overproduction of very low-density lipoproteins (VLDLs) by the liver and increased secretion of large, apolipoprotein (apo) B-100-containing VLDL is the primary metabolic characteristic of most of these patients. The TG in VLDL is hydrolyzed by lipoprotein lipase (LPL) which produces intermediate-density lipoprotein. The TG in intermediate-density lipoprotein is hydrolyzed further, resulting in the generation of LDL. The cholesterol esters in LDL are exchanged for TG in VLDL by the cholesterol ester tranfer proteins, followed by hydrolysis of TG in LDL by hepatic lipase which produces small, dense LDL. Cholesterol ester transfer protein mediates a similar lipid exchange between VLDL and HDL, producing a cholesterol ester-poor HDL. In adipocytes, reduced fatty acid trapping and retention by adipose tissue may result from a primary defect in the incorporation of free fatty acids into TGs. Alternatively, insulin resistance may promote reduced retention of free fatty acids by adipocytes. Both these abnormalities lead to increased levels of free fatty acids in plasma, increased flux of free fatty acids back to the liver, enhanced production of TGs, decreased proteolysis of apo B-100, and increased VLDL production. Decreased removal of postprandial TGs often accompanies these metabolic abnormalities. Genes regulating the expression of the major players in this metabolic cascade, such as LPL, cholesterol ester transfer protein, and hepatic lipase, can modulate the expression of small, dense LDL but these are not the major defects. New candidates for major gene effects have been identified on chromosome 1. Regardless of their fundamental causes, small, dense LDL (compared with normal LDL) particles have a prolonged residence time in plasma, are more susceptible to oxidation because of decreased interaction with the LDL receptor, and enter the arterial wall more easily, where they are retained more readily. Small, dense LDL promotes endothelial dysfunction and enhanced production of procoagulants by endothelial cells. Both in animal models of atherosclerosis and in most human epidemiologic studies and clinical trials, small, dense LDL (particularly when present in increased numbers) appears more atherogenic than normal LDL. Treatment of patients with small, dense LDL particles (particularly when accompanied by low HDL and hypertriglyceridemia) often requires the use of combined lipid-altering drugs to decrease the number of particles and to convert them to larger, more buoyant LDL. The next critical step in further reduction of CAD will be the correct diagnosis and treatment of patients with small, dense LDL and the dyslipidemia that accompanies it.