Significance of small dense low-density lipoproteins and other risk factors in patients with various types of coronary heart disease

Association of Lipoprotein Subfractions With Presence and Severity of Coronary Artery Disease in Patients Referred for Coronary Angiography

Lipoprotein subfractions (LS) can be used for better risk stratification in subjects deemed not at high risk for coronary artery disease (CAD). In this study, we evaluated the correlation between LS with CAD presence and severity. This is a prospective case-control study of 157 patients referred for coronary angiography who were not on lipid-lowering therapy and had LS measured by nuclear magnetic resonance spectroscopy. Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) scores were calculated to estimate CAD severity. Univariate and multivariable regression analysis was performed to determine correlation of LS with CAD presence and severity and acute coronary syndrome (ACS). There was significant association of certain LS (positive for total low-density lipoprotein particle [LDL-P], small LDL-P and apolipoprotein B, negative for large high-density lipoprotein particle [HDL-P] and apolipoprotein A1 [ApoA1]) with the presence of obstructive CAD and CAD severity. Small LDL-P and HDL-P were still predictive for obstructive CAD after adjusting for traditional risk factors, 10-year atherosclerotic cardiovascular disease risk score and in those with low-density lipoprotein cholesterol <100 mg/100 ml. Total LDL-P and ApoA1 were predictive of CAD severity on multivariable analysis. Higher small LDL-P and lower large HDL-P were associated with ACS presence, although only large HDL-P had a significant inverse correlation with ACS on adjusted analysis (odds ratio 0.74 95% confidence interval 0.58, 0.95) In conclusion, in our cohort of patients referred for coronary angiography, total LDL-P, small LDL-P, and apolipoprotein B had significant direct correlation, and large HDL-P and ApoA1 had significant inverse correlation with obstructive CAD and CAD severity.

Associations between leukocyte count and lipid-related indices: Effect of age and confounding by habits of smoking and alcohol drinking

Leukocyte count in peripheral blood is an acute-phase reactant and is associated with the risk of atherosclerotic diseases. Blood lipid profile, a major risk factor of cardiovascular disease, is known to be associated with leukocyte count, but it remains to be determined how this association is affected by other factors including lifestyle and age. The subjects were 11261 Japanese middle-aged men (30~65 years old) who had received health checkup examinations. The relationships of leukocyte count with lipid-related indices (ratio of LDL cholesterol to HDL cholesterol [LDL-C/HDL-C], ratio of triglycerides to HDL cholesterol [TG/HDL-C] and cardiometabolic index [CMI]) were investigated. Leukocyte count, LDL-C/HDL-C, TG/HDL-C and CMI were significantly higher in smokers than in nonsmokers, while leukocyte count and LDL-C/HDL-C were significantly lower in regular drinkers than in nondrinkers. Both in overall subjects and subjects without habits of smoking and drinking, LDL-C/HDL-C, TG/HDL-C and CMI were significantly higher in the 2nd and 3rd tertiles for leukocyte count than in the 1st tertile and tended to be higher with an increase of the tertile. Odds ratios for high TG/HDL-C and high CMI of the 3rd vs. 1st tertiles for leukocyte count tended to be lower with an increase of age, and odds ratios for high TG/HDL-C and high CMI of the interaction term, consisting of age (60~65 vs. 30~39 years) and tertile (3rd vs. 1st tertiles for leukocyte count), were significantly lower than the reference level. In conclusion, leukocyte count is associated with lipid-related indices, and the associations are independent of smoking and alcohol drinking and tend to be weaker with an increase of age in Japanese middle-aged men.

Effects of Alirocumab on Triglyceride Metabolism: A Fat-Tolerance Test and Nuclear Magnetic Resonance Spectroscopy Study

Background: PCSK9 antibodies strongly reduce LDL cholesterol. The effects of PCSK9 antibodies on triglyceride metabolism are less pronounced. The present study aimed to investigate in detail the effects of alirocumab on triglycerides, triglyceride-rich lipoproteins, and lipase regulators. Methods: A total of 24 patients with an indication for treatment with PCSK9 antibodies were recruited. There were two visits at the study site: the first before initiation of treatment with alirocumab and the second after 10 weeks of treatment. Fat-tolerance tests, nuclear magnetic resonance spectroscopy, and enzyme-linked immunosorbent assays were performed to analyze lipid metabolism. Results: A total of 21 participants underwent the first and second investigation. Among these, two participants only received alirocumab twice and 19 patients completed the trial per protocol. All of them had atherosclerotic vascular disease. There was no significant effect of alirocumab treatment on fasting triglycerides, post-prandial triglycerides, or lipoprotein-lipase regulating proteins. Total, large, and small LDL particle concentrations decreased, while the HDL particle concentration increased (all p < 0.001). Mean total circulating PCSK9 markedly increased in response to alirocumab treatment (p < 0.001). Whereas PCSK9 increased more than three-fold in all 19 compliant patients, it remained unchanged in those two patients with two injections only. Conclusion: Significant effects of alirocumab on triglyceride metabolism were not detectable in the ALIROCKS trial. The total circulating PCSK9 concentration might be a useful biomarker to differentiate non-adherence from non-response to PCSK9 antibodies.

Triglyceride and Small Dense LDL-Cholesterol in Patients with Acute Coronary Syndrome

BACKGROUND

Small dense LDL-cholesterol is an established risk factor for atherosclerosis but is not routinely measured in daily practice. The association between small dense LDL-cholesterol and triglyceride, which in turn is routinely measured, in patients with acute coronary syndrome remains unknown.

METHODS

Consecutive patients with acute coronary syndrome who were admitted to our institute were prospectively included, and serum samples were obtained on admission. The association between small dense LDL-cholesterol and triglyceride was investigated.

RESULTS

Among 55 patients (median 71 years old, 64% men), median (interquartile range) small dense LDL-cholesterol was 23.6 (17.0, 36.0) and triglyceride was 101 (60, 134) mg/dL. Triglyceride level correlated with small dense LDL-cholesterol (r = 0.67, p < 0.001) and was an independent determinant of small dense LDL-cholesterol together with body mass index (p = 0.010 and p = 0.008, respectively). Those with high triglyceride and high body mass index had a 3-fold level of small dense LDL-cholesterol compared with those with low triglyceride and low body mass index (45.8 [35.0, 54.0] mg/dL versus 15.0 [11.6, 23.7] mg/dL, p = 0.001).

CONCLUSIONS

Triglyceride level was a major determinant of small dense LDL-cholesterol in patients with acute coronary syndrome. Triglyceride level might be a useful and practical biomarker for risk stratification for patients with acute coronary syndrome together with body mass index.

Non-Fasting Hypertriglyceridemia as an Independent Risk Factor for Coronary In-Stent Restenosis after Primary Bare Metal Stent Implantation in Patients with Coronary Artery Disease

After a percutaneous coronary intervention (PCI) in patients with coronary artery disease (CAD), in-stent neoatherosclerosis may pose a risk of in-stent restenosis (ISR). To clarify whether non-fasting hypertriglyceridemia contributes to ISR, we examined the relationship between non-fasting hypertriglyceridemia (i.e., triglyceride (TG) level ≥ 200 mg/dL) and ISR after stenting with a bare metal stent (BMS) post-primary PCI in patients with CAD by means of a single-site retrospective analysis. A total of 1,039 patients with CAD were enrolled, and 86 patients (112 lesions) were evaluated for BMS-ISR 3-6 months post-primary PCI. The percentage of patients with non-fasting hypertriglyceridemia was significantly higher in the ISR (+) group than in the ISR (-) group (P < 0.009). The follow-up period and number of patients in the ISR (+) group were significantly smaller than those in the ISR (-) group (P < 0.001). There were no significant between-group differences in the other baseline patient characteristics before the primary PCI or at the time of the follow-up coronary angiography. However, at the follow-up period, the ISR (+) group had significantly lower diastolic blood pressure and high-density lipoprotein cholesterol levels (P = 0.015) and significantly higher TG levels (P = 0.012) than the ISR (-) group. A multiple logistic regression analysis demonstrated that non-fasting hypertriglyceridemia and a follow-up period of ≥ 6 months were independent risk factors for ISR after primary PCI in patients with BMS implantation for stenotic CAD (P = 0.006), with an adjusted odds ratio of 8.232 (1.201-56.410) and 0.006 (95% confidence interval < 0.001-0.045), respectively. Non-fasting hypertriglyceridemia may be an additional independent risk factor for BMS-ISR after primary PCI in patients with CAD.

Testing lipid markers as predictors of all-cause morbidity, cardiac disease, and mortality risk in captive western lowland gorillas (Gorilla gorilla gorilla)

Great apes and humans develop many of the same health conditions, including cardiac disease as a leading cause of death. In humans, lipid markers are strong predictors of morbidity and mortality risk. To determine if they similarly predict risk in gorillas, we measured five serum lipid markers and calculated three lipoprotein ratios from zoo-housed western lowland gorillas (aged 6-52 years, n = 61 , subset with routine immobilizations only: n = 47 ): total cholesterol (TC), triglycerides (TGs), high-density lipoprotein (HDL), low-density lipoprotein (LDL), apolipoprotein A1 (apoA1), TC / HDL , LDL / HDL , and TG / HDL . We examined each in relation to age and sex, then analyzed whether they predicted all-cause morbidity, cardiac disease, and mortality using generalized linear models (GLMs). Older age was significantly associated with higher TG, TC / HDL , LDL / HDL , and TG / HDL , and lower HDL and apoA1. With all ages combined, compared to females, males had significantly lower TG, TC / HDL , LDL / HDL , and TG / HDL , and higher HDL. Using GLMs, age, sex, and lower LDL / HDL were significant predictors of all-cause morbidity; this is consistent with research demonstrating lower LDL in humans with arthritis, which was the second most prevalent condition in this sample. In contrast to humans, lipid markers were not better predictors of cardiac disease and mortality risk in gorillas, with cardiac disease best predicted by age and sex alone, and mortality risk only by age. Similar results were observed when multimodel inference was used as an alternative analysis strategy, suggesting it can be used in place of or in addition to traditional methods for predicting risk.

Association of small, dense LDL-cholesterol concentration and lipoprotein particle characteristics with coronary heart disease: A systematic review and meta-analysis

OBJECTIVES

The aim of this study was to systematically collate and appraise the available evidence regarding the associations between small, dense low-density lipoprotein (sdLDL) and incident coronary heart disease (CHD), focusing on cholesterol concentration (sdLDL-C) and sdLDL particle characteristics (presence, density, and size).

BACKGROUND

Coronary heart disease (CHD) is the leading cause of death worldwide. Small, dense low-density lipoprotein (sdLDL) has been hypothesized to induce atherosclerosis and subsequent coronary heart disease (CHD). However, the etiological relevance of lipoprotein particle size (sdLDL) versus cholesterol content (sdLDL-C) remains unclear.

METHODS

PubMed, MEDLINE, Web of Science, and EMBASE were systematically searched for studies published before February 2020. CHD associations were based on quartile comparisons in eight studies of sdLDL-C and were based on binary categorization in fourteen studies of sdLDL particle size. Reported hazards ratios (HR) and odds ratios (OR) with 95% confidence interval (CI) were standardized and pooled using a random-effects meta-analysis model.

RESULTS

Data were collated from 21 studies with a total of 30,628 subjects and 5,693 incident CHD events. The average age was 67 years, and 53% were men. Higher sdLDL and sdLDL-C levels were both significantly associated with higher risk of CHD. The pooled estimate for the high vs. low categorization of sdLDL was 1.36 (95% CI: 1.21, 1.52) and 1.07 (95% CI: 1.01, 1.12) for comparing the top quartiles versus the bottom of sdLDL-C. Several studies suggested a dose response relationship.

CONCLUSIONS

The findings show a positive association between sdLDL or sdLDL-C levels and CHD, which is supported by an increasing body of genetic evidence in favor of its causality as an etiological risk factor. Thus, the results support sdLDL and sdLDL-C as a risk marker, but further research is required to establish sdLDL or sdLDL-C as a potential therapeutic marker for incident CHD risk reduction.

Non-HDL as a Valid Surrogate Marker of Small Dense LDL in a Young Indian Population

Small dense (sd) LDL is a significant independent risk factor for premature coronary artery disease (CAD). Unfortunately, its estimation is not popular, due to the limited availability of specialized equipment, high cost and time-consuming technique. Non-HDL is a calculated, single index measure of all atherogenic apolipoprotein-B containing lipoproteins. This study aimed at identifying non-HDL as a superior surrogate marker of sdLDL cholesterol in a young Indian population. 161 healthy subjects < 45 years were tested for lipid profile, apolipoproteins A1 and B, and sdLDL particle size. sdLDL particles showed negative correlation with non-HDL (r = - 0.283, p < 0.001), LDL (r = - 0.195, p = 0.013) and apoB/apo A1 (r = - 0.175, p = 0.026), the significance being greatest with non-HDL. ROC showed AUC for non-HDL, LDL and apoB/apo A1 as 0.704, 0.686, and 0.596 respectively. For LDL < 130 mg/dL, sdLDL showed a more significant negative correlation with non-HDL (r = - 0.291, p < 0.001) as compared with apoB/apoA1 (r = - 0.172, p = 0.037). For triglycerides < 200 mg/dL, sdLDL particle size showed higher significant negative correlation with non-HDL (r = - 0.213, p = 0.015) than with LDL (r = - 0.176, p = 0.045) while for triglycerides between 200 and 400 mg/dL, significant negative correlation was observed only with non-HDL (r = - 0.372, p = 0.043). Hence, our study suggested that non-HDL is a superior surrogate marker of sdLDL particle size as compared to LDL and apoB/A1 ratio in a young healthy Indian population and should be used for optimum assessment of dyslipidemias and CAD risk.

Is Lipid Accumulation Product Associated with an Atherogenic Lipoprotein Profile in Brazilian Subjects?

Background

Lipid accumulation product (LAP), a simple and low-cost tool, is a novel biomarker of central lipid accumulation and represents a potential surrogate marker for atherogenic lipoprotein profile. However, its association with lipoprotein subfractions has not been described in the literature.

Objective

To determine whether LAP index could be used as a marker of low- and high-density lipoprotein (LDL and HDL) size in Brazilian individuals.

Methods

This cross-sectional study included patients (n = 351) of both sexes and age between 30-74 years. Clinical and sociodemographic data and family history of diseases were evaluated. Lipoprotein size, and levels of total cholesterol (TC), lipoproteins, apolipoprotein AI and B (APO AI/APO B), glucose, insulin, insulin resistance index (HOMA-IR) and non-esterified fatty acids (NEFA) were assessed in blood samples. LAP was calculated by the formulas [(waist circumference_[cm]-58) × (triglycerides_[mmol/L]) for women and (waist circumference _[cm]-65) × (triglycerides _[mmol/L]) for men]. The association between LAP and metabolic parameters were tested by linear trend (general linear model, GLM test) before and after multiple adjustments for potential confounders (sex, age, smoking, statin, fibrate, and hypoglycemic drugs) at significant level p < 0.05.

Results

LAP was positively associated with TC, APO B, NEFA, glucose, insulin and HOMA-IR values, and negatively associated with HDL-C. Higher central lipid accumulation was corelated with higher percentage of intermediate HDL and of small LDL and HDL and less amount of large HDL. LDL size was also reduced in greater LAP index values. The negative impact of LAP was maintained after adjustment for multiple variables.

Conclusion

LAP was robustly associated with atherogenic profile of lipoprotein subfractions, independently of multiple confounders.

N-3 polyunsaturated fatty acids improve lipoprotein particle size and concentration in Japanese patients with type 2 diabetes and hypertriglyceridemia: a pilot study

Background

Patients with type 2 diabetes are at high risk for cardiovascular disease. Although hydroxymethylglutaryl-CoA reductase inhibitors (statins) can reduce cardiovascular events, residual risk remains even after target low-density lipoprotein cholesterol (LDL-C) levels have been achieved. Lipoprotein particle size and fraction changes are thought to contribute to such risks. The purpose of this study was to evaluate the effects of n-3 polyunsaturated fatty acids (n-3 PUFAs), predominantly eicosapentaenoic acid and docosahexaenoic acid, on lipoprotein particle size, concentration, and glycemic control in Japanese patients with type 2 diabetes and hypertriglyceridemia.

Methods

This was a multicenter, prospective, open-label, single arm study. We enrolled 14 patients with type 2 diabetes and hypertriglyceridemia treated with statins and dipeptidyl peptidase-4 inhibitors with glycated hemoglobin (HbA1c) < 8.0%, LDL-C < 120 mg/dL, and fasting triglyceride ≥150 mg/dL. After a 12-week observation period, they were treated with 4 g/day n-3 PUFAs for 12 weeks. Lipoprotein particle sizes, concentrations, lipoprotein insulin resistance (LPIR) scores, lipid profiles, HbA1c, and fasting plasma glucose (FPG) were measured before and after treatment. Lipoprotein profiles were measured by nuclear magnetic resonance spectroscopy. Data were analyzed using Wilcoxon signed-rank tests.

Results

Concentrations of total cholesterol (P < 0.001), LDL-C (P = 0.003), and triglyceride (P < 0.001) decreased following n-3 PUFA administration. N-3 PUFAs decreased the size of very low-density lipoprotein (VLDL; P < 0.001) particles, but did not affect LDL or high-density lipoprotein (HDL) particles. The concentration of large LDL increased, whereas small LDL decreased, causing the large to small LDL ratio to increase significantly (P = 0.042). Large VLDL and chylomicron concentrations significantly decreased, as did the large to small VLDL ratio (all P < 0.001). FPG levels unchanged, whereas HbA1c levels slightly increased. LPIR scores improved significantly (P = 0.001).

Conclusions

N-3 PUFAs partly improved atherogenic lipoprotein particle size and concentration, and produced less atherogenic lipoprotein subclass ratios in patients that achieved target LDL-C levels and glycemic control. These results suggest that n-3 PUFAs may reduce residual cardiovascular risk factors in statin-treated patients with type 2 diabetes and hypertriglyceridemia.

Trial registration

The study was registered at UMIN-ID: UMIN000013776.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0706-8) contains supplementary material, which is available to authorized users.

Method for estimating high sdLDL-C by measuring triglyceride and apolipoprotein B levels

Background

We previously developed an assay to directly measure small dense (sd) low-density lipoprotein cholesterol (LDL-C) levels, which is not widely used in general clinical practice. Therefore, we propose a simpler method, “LDL window,” that uses conventional methods for estimating high sdLDL-C levels.

Methods

We analyzed our previous studies (2006–2008) on healthy subjects and patients with type 2 diabetes and coronary artery disease (CAD). The sdLDL-C level was measured using the precipitation method, and LDL size was determined using gradient gel electrophoresis. The “LDL window” comprises the estimation of LDL particle number and size. We adopted apolipoprotein B (apoB) for the estimation of the LDL particle number and used 110 mg/dL as the cutoff value for hyper-apoB. Triglycerides (TGs) are a powerful inverse determinant of LDL particle size. Therefore, we adopted TG for the estimation of the LDL particle size and used 150 mg/dL as the cutoff value for hyper-TG. Subjects were stratified into the following four subgroups: normal, hyper-TG, hyper-apoB, and hyper-TG/-apoB. Non-high-density lipoprotein cholesterol (non-HDL-C) is a surrogate marker for apoB; therefore, the “alternative LDL window” comprised non-HDL-C (cutoff, 170 mg/dL) and TG.

Results

The top quartile (Q4) of sdLDL-C (>31 mg/dL) doubled in patients with diabetes and CAD. The hyper-TG/-apoB group in the “LDL window” represented >90% Q4 and <4% Q1 and Q2, irrespective of the subjects. The sdLDL-C levels in the hyper-TG/-apoB group were 50% higher in patients with diabetes and CAD than those in controls. Similar results were obtained using the “alternative LDL window.”

Conclusions

Our proposed “LDL window” may help identify patients at high risk of CAD independent of LDL-C.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0417-6) contains supplementary material, which is available to authorized users.

Apolipoprotein B Is Related to Metabolic Syndrome Independently of Low Density Lipoprotein Cholesterol in Patients with Type 2 Diabetes

BACKGROUND

Increased low density lipoprotein cholesterol (LDL-C) level and the presence of metabolic syndrome (MetS) are important risk factors for cardiovascular disease (CVD) in type 2 diabetes mellitus (T2DM). Recent studies demonstrated apolipoprotein B (apoB), a protein mainly located in LDL-C, was an independent predictor of the development of CVD especially in patients with T2DM. The aim of this study was to investigate the relationship between apoB and MetS in T2DM patients.

METHODS

We analyzed 912 patients with T2DM. Fasting blood samples were taken for glycated hemoglobin, high-sensitivity C-reactive protein, total cholesterol, triglyceride (TG), high density lipoprotein cholesterol, LDL-C, and apoB. MetS was defined by the modified National Cholesterol Education Program Adult Treatment Panel III criteria. We performed a hierarchical regression analysis with apoB as the dependent variable. Age, sex, the number of components of MetS and LDL-C were entered at model 1, the use of lipid-lowering medications at model 2, and the individual components of MetS were added at model 3.

RESULTS

Seventy percent of total subjects had MetS. ApoB level was higher in subjects with than those without MetS (104.5±53.3 mg/dL vs. 87.7±33.7 mg/dL, P<0.01) even after adjusting for LDL-C. ApoB and LDL-C were positively correlated to the number of MetS components. The hierarchical regression analysis showed that the increasing number of MetS components was associated with higher level of apoB at step 1 and step 2 (β=0.120, P<0.001 and β=0.110, P<0.001, respectively). At step 3, TG (β=0.116, P<0.001) and systolic blood pressure (β=0.099, P<0.05) were found to significantly contribute to apoB.

CONCLUSION

In patients with T2DM, apoB is significantly related to MetS independently of LDL-C level. Of the components of MetS, TG, and systolic blood pressure appeared to be determinants of apoB.

Markers of inflammation associated with plaque progression and instability in patients with carotid atherosclerosis

Atherosclerosis is the focal expression of a systemic disease affecting medium- and large-sized arteries, in which traditional cardiovascular risk factor and immune factors play a key role. It is well accepted that circulating biomarkers, including C-reactive protein and interleukin-6, reliably predict major cardiovascular events, including myocardial infarction or death. However, the relevance of biomarkers of systemic inflammation to atherosclerosis progression in the carotid artery is less established. The large majority of clinical studies focused on the association between biomarkers and subclinical atherosclerosis, that is, carotid intima-media thickening (cIMT), which represents an earlier stage of the disease. The aim of this work is to review inflammatory biomarkers that were associated with a higher atherosclerotic burden, a faster disease progression, and features of plaque instability, such as inflammation or neovascularization, in patients with carotid atherosclerotic plaque, which represents an advanced stage of disease compared with cIMT. The association of biomarkers with the occurrence of cerebrovascular events, secondary to carotid plaque rupture, will also be presented. Currently, the degree of carotid artery stenosis is used to predict the risk of future cerebrovascular events in patients affected by carotid atherosclerosis. However, this strategy appears suboptimal. The identification of suitable biomarkers could provide a useful adjunctive criterion to ensure better risk stratification and optimize management.

Association of plasma small dense LDL cholesterol with PCSK9 levels in patients with angiographically proven coronary artery disease

BACKGROUND AND AIMS

Proprotein convertase subtilisin-kexin type 9 (PCSK9) is a novel regulator of low-density lipoprotein (LDL) metabolism. Recently, small dense LDL (sdLDL) particles have been suggested to be a very atherogenic subspecies of LDL. To date, the association of sdLDL with PCSK9 is still unclear. The aim of the present study is to determine the association of sdLDL, as assayed by sdLDL-cholesterol (sdLDL-C), with PCSK9 in a cohort of subjects undergoing coronary angiography.

METHODS AND RESULTS

Four hundred and ninety consecutive subjects were enrolled and classified into stable coronary artery disease (CAD) and non-CAD group. LDL separation was performed by Lipoprint System: 7 LDL subfractions were obtained and LDL score (% sdLDL) was calculated. The plasma PCSK9 levels were measured by ELISA. The data indicated that PCSK9 levels were significantly increased by sdLDL-C quartiles (p = 0.028). In age- and sex-adjusted analysis plasma sdLDL-C was positively correlated with PCSK9 levels (r = 0.157, p < 0.01). To rule out the confounding effect of dyslipidemia, we performed the analysis in subjects with and without dyslipidemia separately. Interestingly, the positive correlation of sdLDL-C with PCSK9 was only significant in patients with dyslipidemia and stable CAD (r = 0.177, p < 0.01). In a model adjusting for traditional risk factors including dyslipidemia, PCSK9 was an independent predictor of high sdLDL-C in CAD group (OR = 12.919, 95% CI 1.427-116.952) but not in non-CAD group.

CONCLUSION

This study firstly demonstrated that plasma sdLDL-C was positively related to PCSK9 in patients with stable CAD, suggesting an interaction between sdLDL-C and PCSK9 in atherosclerotic coronary disease.

Elevated small dense low-density lipoprotein cholesterol as a predictor for future cardiovascular events in patients with stable coronary artery disease

AIM

The aim of the present study was to investigate how small dense low-density lipoprotein cholesterol (sdLDL-C) compared with LDL-C affect the long-term prognosis in patients with stable coronary artery disease (CAD).

METHODS

sdLDL-C measured by heparin magnesium precipitation and LDL particle size measured by non-denatured gradient-gel electrophoresis were compared in 190 consecutive CAD patients who underwent coronary arteriography between 2003 and 2004 who did or did not develop cardiovascular events during a seven-year follow-up period. Cardiovascular events were death caused by cardiovascular diseases(CVDs), onset of acute coronary syndrome, need for coronary and peripheral arterial revascularization, hospitalization for heart failure, surgical procedure for any CVDs, and/or hospitalization for stroke.

RESULTS

First-time cardiovascular events were observed in 72 patients. Those who experienced cardiovascular events were older and had higher prevalence rates of hypertension and diabetes; significantly higher Gensini coronary atherosclerotic scores; significantly higher levels of sdLDL-C, sdLDL-C/LDL-C, and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratios; and greater glycated hemoglobin(Hb)A1c and brain natriuretic peptide (BNP) levels. They also had significantly smaller LDL particle sizes, HDL-C, apolipoprotein A-1, and estimated glomerular filtration rate (GFR) compared with patients without cardiovascular events. Conversely, LDL-C, non-HDL-C, apolipoprotein B, remnantlike particle cholesterol, and high-sensitivity C-reactive protein (hs-CRP) levels were similar between the two groups. A Kaplan-Meyer event-free survival curve demonstrated that patients with sdLDL-C≥35 mg/dL (median level) had significantly poorer prognosis compared with those with lower sdLDL-C levels, while patients with LDL-C ≥100 mg/dL had a non-significantly lower survival rate.

CONCLUSION

These results confirm that sdLDL-C is a very promising biomarker to predict future cardiovascular events in the secondary prevention of stable CAD.

The potential of Cystatin C and small dense LDL as biomarkers of coronary artery disease risk in a young Indian population

Coronary artery disease (CAD) affects Indians 5-6 years earlier than in the west, is diffuse and malignant, and poses a heavy burden on India's developing economy. Traditional risk factors have failed to explain this high incidence of premature CAD and hence this study investigated the association of two novel risk biomarkers, cystatin C and small dense LDL (sdLDL) with the presence and severity of CAD. Cystatin C and sdLDL were estimated in 204 CAD patients ≤45 years of age and compared with 161 age-matched healthy controls. The traditional lipid profile parameters, i.e., cholesterol, LDL, HDL, triglycerides, apolipoproteins A1 and B, and Lp(a) were also measured in both groups. Cystatin C was significantly raised and mean LDL particle size significantly reduced in CAD patients as compared to controls. 62.7 % of CAD patients showed pattern B while 37.3 % patients showed pattern A. Of the traditional lipid tests, only HDL and apolipoprotein A1 showed a significant decrease in the CAD group. sdLDL was significantly associated with the severity of CAD, while cystatin C was not. Both cystatin C and sdLDL emerged as independent risk factors, however, of the two, sdLDL was a more sensitive predictor of CAD events. Cystatin C and mean LDL particle size are significantly and independently associated with the presence of CAD events in patients ≤45 years with normal kidney function. Hence, these novel risk biomarkers can be useful tools in reducing the morbidity and mortality associated with CAD in the productive Indian workforce.

Apolipoprotein B/apolipoprotein A-I ratio and apolipoprotein B: long-term predictors of myocardial infarction in initially healthy middle-aged men--a 13-year follow-up

We investigated whether serum concentrations of apolipoprotein (apo) B and apoA-I and the apoB/apoA-I ratio provided predictive information on myocardial infarction (MI) and ischemic stroke during 13 years of follow-up in a group of initially clinically healthy 58-year-old men, free from previous cardiovascular disease, diabetes, other established disease, or treatment with cardiovascular drugs. Multivariate logistic regression analysis showed that the apoB/apoA-I ratio and apoB were significant and independent determinants of MI (exponentiation of the B coefficient [Exp(β)] 3.1, 95% confidence interval [CI] 1.6-6.3, P=.001, Exp(β) 2.8, 95% CI 1.1-7.7, P=.045, respectively). The area under the receiver-operating characteristics curve as a relative measure of test efficiency was highest and significant for both apoB/apoA-I ratio and apoB (area under the curve=0.75, P<.001). In conclusion, the apoB/apoA-I ratio and apoB are independent risk factors for MI and has the highest efficiencies for predicting MI in initially healthy middle-aged men.

Small-dense LDL cholesterol/large-buoyant LDL cholesterol ratio as an excellent marker for indicating lipodystrophy in HIV-infected patients

OBJECTIVES

To examine whether the lipid parameters are predicting factors for human immunodeficiency virus (HIV)-associated lipodystrophy.

METHODS

Whole-body fat compositions of HIV-positive patients receiving stavudine-containing antiretroviral regimens (n = 79) were determined. Lipodystrophy was defined as a ratio of trunk fat mass/lower limb fat mass greater than 2.28. Blood samples were analyzed for total cholesterol (TC), triglycerides, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), small-dense LDL-C (sdLDL-C), apoAI, apoB, lipoprotein(a), and CD4 cell counts. Large-buoyant LDL-C (lbLDL-C) was calculated (LDL-C minus sdLDL-C).

RESULTS

Twenty-six patients were classified as having lipodystrophy. The mean values of triglycerides, HDL-C, sdLDL-C, apoB, TC/HDL-C, apolipoprotein (apo) B/apoAI, and sdLDL-C/lbLDL-C showed significant differences between patients with and without lipodystrophy (P < .02). Using logistic regression analysis, sdLDL-C/lbLDL-C was identified as a significant predictor of lipodystrophy (P < .001). At a ratio of 0.554, the odds ratio was 17.8 with a likelihood ratio of 5.5.

CONCLUSIONS

The sdLDL-C/lbLDL-C ratio is an excellent marker for indicating lipodystrophy in HIV-infected patients.

LOW-DENSITY LIPOPROTEIN SUBFRACTIONS AND VARYING DEGREE OF CORONARY STENOSIS

Aim.To investigate whether low and intermediate density lipoprotein (LDL, IDL) subfractions are associated with a degree of angiographically verified coronary atherosclerosis, as well as with other biochemical risk factors of coronary heart disease (CHD), and hypertriglyceridemia (HTG) in particular.

Material and methods.The study included 129 patients (76 men and 53 women), aged 33–75 years, who were referred for coronary angiography. All participants were divided into three groups by the degree of coronary artery (CA) stenosis: 0–20%, 21–70%, and >70%. LDL and IDL subfractions were measured with the Lipoprint LDL System (electrophoresis in 3% polyacrylamide gel).

Results.All groups were similar by the levels of lipid and apoprotein parameters. The levels of high-sensitive C-reactive protein and glucose, as well as HOMA-IR index, were higher in Group 3 patients. In most cases of severe CA stenosis, small dense LDL particles were detected. In HTG patients, higher levels of small dense LDL3 particles were registered only together with the CA stenosis of at least 21–70%.

Conclusion.The findings on lipoprotein subfractions, obtained with the Lipoprint LDL System, have demonstrated that in patients with verified coronary atherosclerosis, there is a link between the levels of more atherogenic small dense LDL3 particles, the degree of CA stenosis, and blood TG levels. The combination of HTG and high LDL3 levels could be considered an additional marker of severe CA atherosclerosis. 

Estimation of plasma small dense LDL cholesterol from classic lipid measures

Calculated low-density lipoprotein cholesterol (cLDL-C) may differ from direct measurement (dLDL-C), and this difference may depend on presence of small, dense LDL (sdLDL) particles in addition to variation in triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C) concentrations. The presence of such dependence would offer a simple means to estimate sdLDL. We studied dependence of sdLDL on cLDL-C, dLDL-C, and other variables. We measured the levels of glucose, creatinine, total cholesterol, TG, HDL-C, and dLDL-C using standardized methods in 297 samples. For sdLDL cholesterol (sdLDL-C), a novel homogeneous assay was used. The cLDL-C was calculated using the Friedewald formula for 220 subjects after excluding for liver or renal disease. Using stepwise regression analysis identified non-HDL-C, cLDL-C, and dLDL-C as significant variables (P < .001; R(2) = 0.88). The regression equation was as follows: sdLDL-C (mg/dL) = 0.580 (non-HDL-C) + 0.407 (dLDL-C) - 0.719 (cLDL-C) - 12.05. The sdLDL-C concentration can be estimated from non-HDL-C, dLDL-C, and cLDL-C values. Identification of a simple, inexpensive marker for sdLDL particles provides a cost-effective method for screening cardiovascular disease risk.

Plant sterols, marine-derived omega-3 fatty acids and other functional ingredients: a new frontier for treating hyperlipidemia

As hyperlipidemia, including hypercholesterolemia (HC) and hypertriglyceridemia (HTN), continue to challenge North America's healthcare systems, patients continue to seek efficacious and safe natural therapies that complement pharmaceutical interventions. However, despite the ever-growing body of research supporting the use of functional foods and nutraceuticals (FFN) for the prevention and treatment of hyperlipidemia, reception amongst the medical community regarding the implementation of FFN into clinical guidelines continues to lag. Research demonstrates that specific FFN target and modulate molecular processes that perpetuate hyperlipidemia. In addition, studies consistently demonstrate that combining certain FFN such as marine-derived omega-3 fatty acids or plant sterols/stanols with statins enhances triglyceride and cholesterol-lowering efficacy, respectively. Thus, the purpose of this commentary is to contend that efficacious FFN not only reduce HC and HTG but also boost the lipid-lowering effects of pharmaceutical hypolipidemic medications. Finally, this editorial aims to challenge current medical guidelines to emphasize efficacious FFN during all stages of treatment of hyperlipidemias as adjuncts to pharmacotherapy.

Independent and additive predictive value of total cholesterol content of erythrocyte membranes with regard to coronary artery disease clinical presentation

BACKGROUND

A new mechanism for clinical instability in coronary artery disease (CAD) has been proposed where erythrocytes could play an active role in atherosclerotic plaque growth and rupture. Clinical studies showed increased total cholesterol levels in the membrane of circulating erythrocytes (CEM) in acute coronary syndrome (ACS) patients compared to patients with chronic stable angina (CSA). We investigated the independent and incremental discriminating value of CEM along with N-terminal propeptide of BNP (NT-proBNP), high sensitivity C-reactive protein (hs CRP), myeloperoxidase (MPO) and apolipoprotein B (apoB) with regard to CAD clinical presentation.

METHODS

519 consecutive angina patients were assessed; 252 had CSA (195 men, 62 ± 9 years) and 267 had ACS (213 men, 62 ± 10 years).CEM levels and serum concentrations of NT-proBNP, hs CRP, MPO and apoB were measured upon study admission.

RESULTS

Simple logistic regression models showed that all biomarkers could distinguish ACS, nevertheless CEM with greater potency (OR 9.26 95%CI 6.31-13.59, p<0.001). Multiple logistic regression models after adjustment for all the variables that were different between the 2 groups as well as for other biomarkers showed that CEM continued to be a significant and an independent predictor of ACS (OR 22.27 95%CI 10.63-46.67, p<0.001). An increment of the C-statistic was also shown when CEM levels were incorporated in the predictive model (including traditional vascular risk factors and new well established biomarkers i.e. hs CRP, MPO, apoB and NT-proBNP).

CONCLUSIONS

The present study showed that CEM levels are associated with clinical instability in CAD patients in an independent and incremental manner.

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.

Combined effects of small apolipoprotein (a) isoforms and small, dense LDL on coronary artery disease risk

BACKGROUND AND AIMS

Lipoprotein (a) [Lp(a)] consists of low-density lipoprotein (LDL) and apolipoprotein (a) [apo(a)]. Both Lp(a) constituents are well-recognized risk factors for coronary artery disease (CAD). This study investigates the interrelationship of apo(a) and LDL size, as well as their possible synergistic effect on the increase of CAD risk.

METHODS

One hundred nine CAD patients and 102 apparently healthy subjects were included in the study. Lp(a) concentration was measured using immunoturbidimetry. The sizes of apo(a) isoforms were determined by SDS-agarose gel electrophoresis followed by immunoblotting. LDL particle size was determined by gradient gel electrophoresis.

RESULTS

We found an inverse correlation between apo(a) size and Lp(a) concentration (r(2) = 31%, p <0.001 in the control group and r(2) = 35%, p <0.001 in the CAD group). Individuals with smaller apo(a) isoforms and small, dense LDL (sdLDL) >50% had the highest risk of CAD development (OR = 4.23, p = 0.017). The synergy index (SIM) for the combination of smaller apo(a) isoforms and sdLDL >50% was 1.2. Adjustment for Lp(a) and triacylglycerol concentrations eliminated smaller apo(a)/sdLDL >50% related risk (p = 0.233 and p = 0.09, respectively).

CONCLUSIONS

Smaller apo(a) isoforms appear to be superior to sdLDL for the assessment of CAD risk. Their combined effect is synergistic.

Effects of increasing particle size of low-density lipoprotein on restenosis after coronary stent implantation

BACKGROUND

Small dense low-density lipoprotein (LDL) has emerged as an important risk factor in coronary atherosclerosis and vascular inflammation, which is related to neointimal hyperplasia. Therefore, the aim of the present study was to investigate whether changes in LDL particle size are related to in-stent restenosis (ISR).

METHODS AND RESULTS

The LDL subfraction and lipid profiles were measured in 274 patients (412 stents) at both baseline and follow-up coronary angiography (CAG). The incidence of ISR (80 lesions, 19.4%) was lower in the patients with increased LDL particle size than in those with no change or decrease (14.2% vs 25.8%, p=0.004). Logistic multivariate analysis revealed that stent length (>or=24 mm) (odds ratio (OR) =1.913, p=0.027), post minimal luminal diameter (>3 mm) (OR =0.528, p=0.028), acute coronary syndrome (OR =2.294, p=0.005), decrease in high-density lipoprotein-cholesterol (OR =1.028, p=0.047) and increase in LDL particle size (OR =0.528, p=0.031) were independent predictors for ISR.

CONCLUSIONS

In the present study, an increase in the LDL particle size between baseline and follow-up CAG was associated with reduced incidence of ISR. Therefore, modification of LDL particle size may have a beneficial effect on the risk of ISR.

Does simultaneous determination of LDL and HDL particle size improve prediction of coronary artery disease risk?

BACKGROUND

Alterations in plasma lipoprotein subclass distribution affect the risk for coronary artery disease (CAD). However, it is unclear whether the determination of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) phenotypes may or may not improve the ability to predict CAD development.

METHODS

Polyacrylamide gradient (3-31%) gel electrophoresis was used to simultaneously determine size and distribution of lipoprotein subclasses in 181 CAD patients and 178 controls.

RESULTS

Mean LDL and HDL subclass sizes were significantly smaller in patients than in controls (p < 0.001). Multivariate logistic regression analysis showed that small dense LDL particles were independent CAD risk predictors (OR = 2.867, p < 0.01), even when adjusted for other traditional risk factors, while small HDL particles lost their significance after adjustment (OR = 2.071, p = 0.054). The area under the ROC curve for LDL (0.671) and HDL (0.643) particle size measurement demonstrated low clinical accuracy when compared to the combination of traditional lipid risk factor measurements.

CONCLUSIONS

CAD is associated with the predominance of smaller LDL and HDL particles. However, simultaneous determination of these two lipoprotein phenotypes provides no additional power in discriminating CAD and non-CAD subjects, beyond that obtained by the traditional risk factors.

Cardiovascular disease in obesity: A review of related risk factors and risk-reduction strategies

Cardiovascular disease (CVD) is the number one cause of mortality in men and women. Currently, two thirds of US adults are overweight or obese. CVD and obesity are closely linked and together take a substantial toll on the health of individuals and the community. It is creating a growing burden on public health and financial difficulties in both personal and institutional funding of health care. A review of recent scientific literature reveals that modest weight loss of 5% to 10% ameliorates cardiometabolic risk factors and improves health outcomes. To date, successful weight-loss interventions have been elusive. The choice of weight-loss medications is limited, and the risks of surgical intervention demand that this option be reserved for those patients with extreme obesity. Research has elucidated an improved understanding of the mechanisms leading to obesity and disease. The potential role of hormones, such as leptin and adiponectin, in altering metabolism and vascular disease is better understood. The endocannabinoid system is now recognized as a potentially viable pathway to modulate appetite and energy, lipid, and glucose metabolism.

Lipoprotein(a) and LDL Particle Size Are Related to the Severity of Coronary Artery Disease

BACKGROUND

The pathophysiological role and metabolic pathway of Lp(a) have not been clearly defined. An association between Lp(a) and oxidative low-density lipoprotein (LDL) were recently reported. And small dense LDL (sd-LDL) were associated with circulating malondialdehyde-modified LDL. We investigated the relationships between serum Lp(a) level and LDL particle size in coronary artery disease (CAD) patients. Further, we investigated the relationships of sd-LDL and Lp(a) with the extent and severity of CAD.

METHODS

A total of 490 patients (mean: 60.5 +/- 11.5 years old) who underwent coronary angiography to evaluate chest pain were investigated. Patients were classified into two groups, a CAD group (n = 256), who had significant stenosis observed by coronary angiogram, and a control group (n = 234), who had normal, or minimal coronary arteries. CAD severity was measured by Gensini scores. The distribution of the LDL subfraction was analyzed using a Quantimetrix Lipoprint LDL System.

RESULTS

The serum Lp(a) concentration was correlated with the fraction of sd-LDL (r = 0.193, p < 0.001) and mean LDL size (r = 0.160, p = 0.003). The Lp(a) level and mean LDL particle size were significantly correlated with a high Gensini score. LDL particle size in the CAD group was smaller than in the control group (26.74 +/- 0.64 vs. 26.43 +/- 0.93 nm, p < 0.001). The Gensini score was significantly higher in small LDL with high Lp(a) level groups.

CONCLUSION

The positive correlation of the level of Lp(a) and sd-LDL fraction were demonstrated. The mechanism of this association is not clearly defined; we can suggest that it may stem from the individual atherogenic condition that linked to increased oxidative stress. Both increased Lp(a) and sd-LDL fraction were correlated with the severity of CAD.

The Effects of Statin and Fibrate on Lowering Small Dense LDL- Cholesterol in Hyperlipidemic Patients with Type 2 Diabetes

AIM

Small dense (sd)-low-density lipoprotein (LDL) is a potent atherogenic lipoprotein. The overall atherogenicity of this lipoprotein can be precisely assessed by quantifying sd-LDL rather than by measuring the LDL size. We studied the effects of representative lipid-lowering agents (statin and fibrate) on sd-LDL-cholesterol (C) in patients with type 2 diabetes.

METHODS

Sd-LDL-C was measured by the precipitation method established by Hirano and Ito. Large buoyant (lb)-LDL-C was calculated by subtracting sd-LDL-C from LDL-C. Type 2 diabetes patients (n=72) were administered lipid-lowering agents for three months: patients with hypercholesterolemia received 1 mg of pitavastatin and those with hypertriglyceridemia received 100 mg of micronized fenofibrate.

RESULTS

Pitavastatin reduced LDL-C by 25% and reduced TG by 8%. The statin decreased sd-LDL-C by 26%, and lb-LDL-C by 22%. Fenofibrate reduced TG by 38% and increased HDL-C by 14%. The fibrate decreased sd-LDL-C by 23% without changing LDL-C. The pitavastatin-induced reduction of sd-LDL-C was significantly correlated with the reduction of LDL-C and apo B, whereas the fenofibrate-induced reduction of sd-LDL-C was correlated with the reduction of TG.

CONCLUSION

Both statin and fibrate reduce the potency of atherogenic sd-LDL particles, but via different mechanisms: the former decreases total-LDL including sd-LDL, while the latter decreases sd-LDL specifically.

Electronegative LDLs from familial hypercholesterolemic patients are physicochemically heterogeneous but uniformly proapoptotic

A highly electronegative fraction of human plasma LDLs, designated L5, has distinctive biological activity that includes induction of apoptosis in bovine aortic endothelial cells (BAECs). This study was performed to identify a relationship between LDL density, electronegativity, and biological activity, namely, the induction of apoptosis in BAECs. Plasma LDLs from normolipidemic subjects and homozygotic familial hypercholesterolemia subjects were separated into five subfractions, with increasing electronegativity from L1 to L5, and into seven subfractions according to increasing density, D1 to D7. L1 to L5 were also separated according to density, and D1 to D7 were separated according to charge. The density profiles of L1 to L5 were similar (maximum density = 1.030 +/- 0.002 g/ml). Induction of apoptosis by all seven density subfractions was confined to the highly electronegative fraction, L5, and within each density subfraction the magnitude of apoptosis correlated with the L5 content. Electronegative LDL is heterogeneous with respect to density and composition, and induction of apoptosis is more strongly associated with LDL electronegativity than with LDL size or density.

Metabolism of phytol to phytanic acid in the mouse, and the role of PPARα in its regulation

Phytol, a branched-chain fatty alcohol, is the naturally occurring precursor of phytanic and pristanic acid, branched-chain fatty acids that are both ligands for the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARalpha). To investigate the metabolism of phytol and the role of PPARalpha in its regulation, wild-type and PPARalpha knockout (PPARalpha-/-) mice were fed a phytol-enriched diet or, for comparison, a diet enriched with Wy-14,643, a synthetic PPARalpha agonist. After the phytol-enriched diet, phytol could only be detected in small intestine, the site of uptake, and liver. Upon longer duration of the diet, the level of the (E)-isomer of phytol increased significantly in the liver of PPARalpha-/- mice compared with wild-type mice. Activity measurements of the enzymes involved in phytol metabolism showed that treatment with a PPARalpha agonist resulted in a PPARalpha-dependent induction of at least two steps of the phytol degradation pathway in liver. Furthermore, the enzymes involved showed a higher activity toward the (E)-isomer than the (Z)-isomer of their respective substrates, indicating a stereospecificity toward the metabolism of (E)-phytol. In conclusion, the results described here show that the conversion of phytol to phytanic acid is regulated via PPARalpha and is specific for the breakdown of (E)-phytol.

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.

Significance of small dense low-density lipoprotein as a risk factor for coronary artery disease and acute coronary syndrome

Small dense LDL (sd-LDL) has recently emerged as an important coronary artery disease (CAD) risk factor. This study was performed to investigate how LDL particle size is related to CAD and acute coronary syndrome (ACS). Blood samples were collected from 504 patients that underwent coronary angiography to evaluate chest pain. The LDL particle size of these samples was measured. The mean LDL particle size was smaller in patients with angiographically proven CAD than in the controls (26.41 +/- 0.95 vs 26.73 +/- 0.64 nm, p < 0.001), and was negatively correlated with the Framingham risk score (r=-0.121, p=0.007). Patients with more extensive CAD had smaller LDL particles. LDL particle size was also smaller in patients with acute coronary syndrome as compared to non-ACS patients (26.09 +/- 1.42 vs 26.54 +/- 0.63 nm, p=0.011). These results suggest that sd-LDL is independently associated with the incidence and extent of CAD, and can be a risk factor for the development of ACS in the Korean population.

Significance of small dense low-density lipoprotein-cholesterol concentrations in relation to the severity of coronary heart diseases

We have investigated the clinical significance of small dense low-density lipoprotein-cholesterol (sd-LDL-C) concentrations in coronary heart disease (CHD). We measured the LDL size by gradient gel electrophoresis and quantified sd-LDL-C concentrations by a newly developed rapid assay using heparin-magnesium precipitation in 225 consecutive CHD patients without any lipid-lowering medication and 142 healthy middle-aged subjects as controls. The LDL size was markedly smaller and sd-LDL-C levels were significantly higher in CHD patients than in controls of both sexes, whereas LDL-C levels were comparable between CHD and controls. The LDL-C levels were significantly higher in a subpopulation of 84 patients with acute coronary syndrome than in other patients groups, while LDL size and high-density lipoprotein-cholesterol (HDL-C) were not found to vary among the patients. The sd-LDL-C increased as the number of diseased vessels or Gensini atherosclerosis score increased. Among the 123 stable CHD patients, multiple logistic regression analysis revealed that sd-LDL-C levels were significantly associated with the clinically severe cases requiring coronary revascularization independently of LDL-C, HDL-C and apolipoprotein B. The sd-LDL mass plays a more important role in the progression of CHD than the LDL size, and the sd-LDL-C concentration serves as a powerful surrogate marker for the prevention of CHD.

Plasma LDL and HDL characteristics and carotenoid content are positively influenced by egg consumption in an elderly population

Background

Approximately 1/3 of individuals have a high plasma response to dietary cholesterol (hyper-responders). Although increases in both LDL and HDL cholesterol have been observed, limited data exist regarding effects of egg consumption on lipoprotein subclasses and circulating carotenoids.

Methods

29 postmenopausal women (50–68 y) and 13 men (60–80 y) were assigned to either 3 eggs (EGG, 640 mg cholesterol/d) or an equal volume of cholesterol-free egg substitute (SUB, 0 mg cholesterol/d) for 30 d. Following a 3 wk wash out, subjects crossed over to the alternate diet. Individuals with a response to dietary cholesterol > 2.2 mg/dL for each additional 100 mg of dietary cholesterol were classified as hyper-responders while hypo-responders were those with a response ≤ to 2.2 mg/dL. Nuclear Magnetic Resonance (NMR) spectroscopy determined LDL and HDL size & particle concentrations. Dietary records were used to evaluate carotenoid consumption.

Results

Hyper-responders had higher concentrations of both LDL (LDL-C) and HDL (HDL-C) cholesterol after EGG. In contrast, the concentrations of plasma LDL-C and HDL-C did not differ between the EGG and SUB for the hypo-responders. After EGG, hyper-responders had larger (≥ 21.2 nm) less atherogenic LDL particle (P < 0.001) and larger HDL particle (> 8.8 nm) (P < 0.01), with no significant difference in the total number of LDL or HDL particles. Regardless of response classification, all individuals had an increase in plasma lutein (from 32.4 ± 15.2 to 46.4 ± 23.3 ng/L) and zeaxanthin (from 8.8 ± 4.8 to 10.7 ± 5.8 ng/L) during EGG, yet hyper-responders displayed higher concentrations of carotenoids when compared to hypo-responders

Conclusion

These findings suggest that the increases in LDL-C and HDL-C due to increased egg consumption in hyper-responders are not related to an increased number of LDL or HDL particles but, to an increase in the less atherogenic lipoprotein subfractions. Also, increases in plasma carotenoids after EGG may provide a valuable dietary source for this population.

Treatment of Hyperlipidemia from Japanese Evidence

The treatment of hyperlipidemia is aimed at preventing cardiovascular disease (CVD) and coronary heart disease (CHD). As the incidence of CHD in Japan is about one-third lower and that of stroke is two-fold higher compared to Western countries, and the doses of lipid-lowering drugs used in foreign randomized controlled clinical trials (RCTs) are much higher than in general use in Japan, it remains unclear whether the results of RCTs conducted in Western countries could be extrapolated to Japanese patients. Recently, two major large-scale, prospective, RCTs in Japanese hypercholesterolmic patients, the Management of Elevated Cholesterol in the Primary Prevention of Adult Japanese (MEGA) study and the Japan EPA Lipid Intervention Study (JELIS), have been reported. Japanese epidemiological studies and Japanese clinical studies are reviewed. The evidence suggests that hypercholesterolemia, hypertriglyceridemia, and low HDL-cholesterol are strongly associated with increased CHD risk. Lipid-lowering medication shows beneficial effects even in low-risk populations; however, the data did not support that lower cholesterol is better. The safety and efficacy of hyperlipidemia treatment in Japanese patients are discussed.

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.

Predominance of Small Dense Low-Density Lipoproteins and Abnormal Glucose Regulation in Patients With Acute Coronary Syndrome

BACKGROUND

Although small dense low-density lipoprotein (sd-LDL) has an established association with diabetic dyslipidemia, previous studies have failed to show an association between sd-LDL and diabetes among coronary heart disease patients. This study investigated the prevalence of sd-LDL and abnormal glucose regulation in acute coronary syndrome (ACS).

METHODS AND RESULTS

LDL size at the onset of ACS was measured by nondenatured gradient gel electrophoresis in 314 of 429 consecutive patients. Sd-LDL was prevalent in 54% of the patients, irrespective of the presence of previously known diabetes (50% vs 60% in nondiabetes and diabetes, respectively). Diabetes was present in 122 (28%) of the patients, and 110 patients without diabetes underwent an oral glucose tolerance test. Impaired glucose tolerance (IGT) and newly detected diabetes were found in as many as 44% and 22% of the patients tested, even though their hemoglobinA1c levels were in the normal range (5.3+/-0.5%). The prevalence of sd-LDL was significantly higher in patients with glucose intolerance than in those with normal glucose tolerance (61% vs 42%).

CONCLUSION

IGT and diabetes were far more common than normal glucose regulation in ACS patients, and the abnormal glycometabolism was closely associated with highly atherogenic sd-LDL.

Effect of plant sterols and endurance training on LDL particle size and distribution in previously sedentary hypercholesterolemic adults

BACKGROUND

Plant sterols and exercise favourably alter lipid profiles in a way that protect against future coronary heart disease (CHD). However, their effects on other indicators of CHD risk, such as LDL particle size, still need further clarification.

OBJECTIVE

This study examined the effect of plant sterols, exercise, and the combination of plant sterols and exercise, on LDL particle size and distribution in previously sedentary, hypercholesterolemic adults.

DESIGN

In an 8-week, placebo-controlled, parallel-arm clinical trial, 84 subjects were randomized to one of four intervention groups: (1) combination of sterols and exercise, (2) exercise, (3) sterol, or (4) control.

RESULTS

Exercise significantly (P < 0.05) reduced post-treatment LDL peak particle size from 255 to 253 A. Additionally, exercise significantly (P < 0.05) decreased the proportion of large LDL particles within plasma. Sterol supplementation significantly (P < 0.05) decreased the estimated cholesterol concentrations within small, medium, and large LDL particles by 13.4, 13.5, and 14.4%, respectively, yet had no effect on the distribution of cholesterol among various LDL particle sizes. Furthermore, decreased body weight post-training was associated with increased cholesterol in small LDL particles (r = -0.52, P < 0.0001). Decrease in body fat percent (BF%) post-training was associated with increased cholesterol concentrations in small LDL particles (r = -0.29, P < 0.01).

CONCLUSION

On the basis of modulating LDL electrophoretic characteristics, the present study demonstrates that plant sterols have no effect on CHD risk, while short-term exercise may potentially increase CHD risk by decreasing LDL peak particle size.

SPONSORSHIP

This study was sponsored by The Heart and Stroke Foundation of Canada.

A potential role of apolipoprotein B in the risk stratification of diabetic patients with dyslipidaemia

Diabetic dyslipidaemia is characterised by retention of atherogenic particles, which are depleted of cholesterol. Therefore, calculating or measuring LDL or VLDL cholesterol may not reflect the actual number of these atherogenic particles. We examined the potential role of apolipoprotein B in the risk stratification of Omani patients with type 2 diabetes and dyslipidaemia. Two hundred and twenty-one subjects with type 2 diabetes and 67 healthy controls were recruited. Diabetic subjects had significantly higher serum levels of triglycerides (P<0.0001), non-HDL cholesterol (P<0.0001), and total/HDL cholesterol ratio (P<0.04) and lower levels of HDL cholesterol (P<0.0001) and lipoprotein(a) compared to nondiabetic subjects. The ratio of apoB/LDL cholesterol ratio was significantly higher (P<0.002) among diabetic compared to nondiabetic subjects. Sixty percent of the diabetic subjects with abnormal apoB of >1.2g/L had an LDL cholesterol of less than 4.2 mmol/L compared to 7% of the nondiabetic subjects (sensitivity; 40% versus 93%, respectively). Furthermore, diabetic subjects with ischaemic heart disease (IHD) had significantly higher (P<0.003) apoB/non-HDL cholesterol ratio compared to those without IHD. These findings suggest that the ratios of apoB/LDL cholesterol and apoB/non-HDL cholesterol may have a role in the risk stratification of diabetic patients with dyslipidaemia.

Association between small dense low-density lipoprotein and postprandial accumulation of triglyceride-rich remnant-like particles in normotriglyceridemic patients with myocardial infarction

BACKGROUND

Although the small dense low-density lipoprotein (sd-LDL) is associated with hypertriglyceridemia, more than 60% of myocardial infarction (MI) patients are normotriglyceridemic in the fasting state. This study was aimed to investigate the relationship between the low-density lipoprotein (LDL) phenotype and postprandial hyperlipemia (PPL) in MI patients.

METHODS AND RESULTS

Oral fat tolerance tests were performed in 71 patients with acute MI and fasting triglyceride concentrations below 200 mg/dl. Postprandial changes in the LDL particle diameter (LDL-PD) and lipids over a 6-h period after a meal were compared among 4 groups of patients classified according to fasting triglyceride levels (A, B as <150, and C, D as > or =150) and postprandial triglyceride levels (A, C as <230 and B, D as > or =230). Although fasting concentrations of triglyceride and remnant-like particle (RLP)-triglyceride were significantly higher in group C than in group B, the areas under the curves of the RLPs were significantly higher in group B. The triglyceride-to-cholesterol ratio in the RLPs was significantly higher in the PPL group than in the nonPPL group postprandially. The prevalence of sd-LDL (LDL-PD < or =25.5 nm) was significantly higher in group D but similar between groups B and C (23%, 42%, 50% and 83% in groups A, B, C and D, respectively).

CONCLUSION

These results suggest that postprandial accumulation of triglyceride-rich lipoproteins is strongly associated with sd-LDL in MI patients without hypertriglyceridemia.

Postprandial changes in LDL phenotypes in patients with myocardial infarction

BACKGROUND

Low-density lipoprotein (LDL) particle size is strongly affected by both fasting and postprandial triglyceride levels. We report here that the LDL phenotype shifts toward the smaller phenotype during oral fat tolerance tests (OFTTs) in some patients with myocardial infarction (MI); a condition closely associated with postprandial increases of triglyceride and remnant-like particles (RLPs).

METHODS

Oral fat tolerance tests were performed on 63 MI patients with fasting serum triglyceride levels of less than 2.25 mmol L-1 (= 200 mg dL-1). Remnant-like particles and other serum lipids were compared among patients characterized by three LDL phenotypes based on nondenaturing gradient gel electrophoresis: pattern A (large LDLs, peak LDL particle size > or = 260 A), pattern I (intermediate-sized LDLs, LDL size > 255 A, < 260 A), and pattern B (small, dense LDLs, LDL size < or = 255 A).

RESULTS

The LDL size decreased significantly in patients with the highest tertile of areas under the incremental curves (AUICs) of triglycerides above the fasting levels. The LDL phenotype shifted toward the smaller phenotype after a fat load in three of eight patients with pattern A and in seven of 35 patients with pattern I. The AUICs of triglyceride-rich lipoproteins were significantly higher in these patients than in the patients exhibiting little change in LDL size, whereas the fasting metabolic parameters were similar among the patients of the same LDL phenotype in the fasting state.

CONCLUSION

These results suggest that alimentary lipaemia plays an important role in the remodeling of LDL particles into the more atherogenic small, dense LDLs in patients with MI.

Relationship between low-density lipoprotein subclasses and asymptomatic atherosclerosis in subjects from the Atherosclerosis Risk in Communities (ARIC) Study

Low-density lipoprotein (LDL) particle size has been associated with coronary heart disease, but an association between LDL size and preclinical atherosclerosis is less well established. Using gradient gel electrophoresis, large (A), intermediate (I) and small (B) LDL size subclasses were determined in 198 cases with asymptomatic carotid artery atherosclerosis (determined by B-mode ultrasonography) and 318 controls from the Atherosclerosis Risk in Communities (ARIC) Study. In Caucasians, a smaller LDL size was more prevalent in men and associated with a higher body mass index, hypertension prevalence, and plasma total- and LDL-cholesterol and triglycerides, but lower HDL-cholesterol. In African-Americans, a smaller LDL size was associated with higher triglycerides and lower HDL-cholesterol and hypertension prevalence. In Caucasians, Subclass B prevalence was 29.1% among cases and 14.8% among controls. The odds ratio (95% confidence interval) for Subclass B rather than Subclass A in Caucasian cases was 2.94 (1.67-5.17); the association remained significant after controlling for age, body mass index, smoking, and either plasma triglycerides or HDL-cholesterol. In African-Americans, however, there was no significant association between LDL subclass and case status. A predominance of smaller LDL particles is associated with asymptomatic carotid artery atherosclerosis in Caucasians, through mechanisms that remain to be elucidated.

Ethnic differences in the formation of small LDL particles in Asians: a comparison of Koreans, Japanese and Mongolians

BACKGROUND

The presence of small, dense LDL particles has been recognized as an independent risk factor for coronary heart disease (CHD) but is not directly representative of CHD mortality rate beyond any given population. We investigated whether such inconsistency between three Asian ethnic groups might have arisen from anthropometric and metabolic factors.

DESIGN

We conducted a cross-sectional survey among adult Koreans (412), Japanese (453) and Mongolians (253).

RESULTS

The prevalence of small LDL particles was 36% in the Koreans, 21% in the Japanese and 7% in the Mongolians. Multiple logistic regression analysis revealed plasma triglyceride (TG) levels to be the strongest determinant of small LDL particle size in all three groups, with sex, HDL-cholesterol and non-HDL-C being other ethnic-specific significant determinants. Body mass index (BMI), FFA and insulin resistance were not significant factors in the regression analysis. Of the subjects with low TG levels (< 133 mg dL(-1)), 25% of the Koreans and 10% of the Japanese, but no Mongolians, had small LDL particles.

CONCLUSIONS

Results of the present study suggest that traditionally, high-carbohydrate diets in Korea and Japan possibly contribute to higher TG-levels compared with BMI-matched Mongolians, and to the formation of small LDL particles, even in instances of low TG levels.

Low-density lipoprotein particle number and risk for cardiovascular disease

The key role played by low-density lipoprotein (LDL) particles in the pathogenesis of coronary heart disease (CHD) is well accepted, as is the benefit of lowering LDL in high-risk patients. What remains controversial is whether we are using the best measure(s) of LDL to identify all individuals who would benefit from therapy. Many studies have shown that, at a given level of LDL cholesterol, individuals with predominantly small LDL particles (pattern B) experience greater CHD risk than those with larger-size LDL. However, it is not clear from this observation that small LDL particles are inherently more atherogenic than large ones because, at a given level of LDL cholesterol, individuals with small LDL have more LDL particles in total. The phenotype of small LDL particle size co-segregates with a cluster of metabolic factors, including elevated triglycerides and reduced HDL cholesterol, and in multivariate analyses has generally been found not to be independently associated with CHD risk. In contrast, LDL particle number measured by nuclear magnetic resonance has consistently been shown to be a strong, independent predictor of CHD.

Cardiovascular risk factors in males with hypertriglycemic waist (Tehran Lipid and Glucose Study)

BACKGROUND

Many studies performed on nontraditional risk factors have proposed a metabolic triad including increased serum level of apolipoprotein B, hyperinsulinemia and high small, dense LDL-C as a risk factor of cardiovascular diseases. Hypertriglycemic waist (increased waist circumference as well as high fasting triglyceride level) can be used as a simple criterion to predict the metabolic triad. The aim of this study was to investigate the prevalence of hypertriglycemic waist and the frequency of cardiovascular risk factors in the affected population.

MATERIALS AND METHODS

The study was performed on 4169, 18-70 y-old male subjects of the population of Tehran Lipid and Glucose Study (TLGS). The subjects fell into four groups with respect to serum level of fasting triglycerides (Tg) and waist circumference (WC). Subjects of group 1 had serum Tg > or =1.8 mmol/l as well as WC > or =95 cm, while those of group 2 had Tg > or =1.8 mmol/l and WC <95 cm. The triglycerides level was less than 1.8 mmol/l in groups 3 and 4, whereas WC was > or =95 cm and lower than 95 cm, respectively. Cardiovascular risk factors, anthropometric and laboratory variables were compared between the groups.

RESULTS

In total, 784 subjects had high serum levels of Tg as well as increased WC. The mean age of subjects was significantly higher in groups 1 and 3 compared to others (37+/-15, 48+/-14, 41+13 and 46+/-13 y of age in groups 4, 3, 2 and 1, respectively, P<0.001). The prevalence of cardiovascular risk factors was significantly higher in group 1 as compared with others. Systolic and diastolic blood pressure, body mass index and WC were significantly higher in group 1 than in the others. Serum total cholesterol, Tg and LDL-C were significantly higher in group 1 compared to others, whereas HDL-C was significantly lower in this group. The prevalence of subjects who had at least four risk factors was 75 and 8% in groups 1 and 4, respectively.

CONCLUSION

Hypertriglycemic waist can be used as a simple criterion to predict cardiovascular risk factors.