Factors influencing the formation of small dense low-density lipoprotein particles in dependence on the presence of the metabolic syndrome and on the degree of glucose intolerance

New Perspectives on Atherogenic Dyslipidaemia and Cardiovascular Disease

Over the past few decades, atherogenic dyslipidaemia has become one of the most common phenotypic presentations of lipid abnormalities, being strongly and unequivocally associated with an increased risk of cardiovascular (CV) disease. Despite the excellent results achieved from statin and non-statin management of LDL cholesterol and CV events prevention, there still remains a significant residual risk, associated with the prevalence of non-LDL cholesterol lipid patterns characterised by elevated triglyceride levels, low HDL cholesterol, a preponderance of small and dense LDL particles, accumulation of remnant lipoproteins and postprandial hyperlipidaemia. These qualitative and quantitative lipid modifications are largely associated with insulin resistance, type 2 diabetes and obesity, the prevalence of which has grown to epidemic proportions throughout the world. In this review, we analyse the pathophysiology of this particular dyslipidaemia, its relationship with the development of atherosclerotic CV disease and, finally, briefly describe the therapeutic approaches, including changes in lifestyle and current pharmacological interventions to manage these lipid alterations aimed at preventing CV events.

Apolipoprotein B discordance with low-density lipoprotein cholesterol and non-high-density lipoprotein cholesterol in relation to coronary artery calcification in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Discordant levels of apolipoprotein B (apo B) relative to low-density lipoprotein cholesterol (LDL-C) or non-high-density lipoprotein cholesterol (non-HDL-C) may be associated with subclinical atherosclerotic cardiovascular disease (ASCVD).

OBJECTIVE

The present study investigated whether discordance between apo B and LDL-C or non-HDL-C levels was associated with subclinical ASCVD measured by coronary artery calcium (CAC).

METHODS

This study was conducted in a subpopulation of the Multi-Ethnic Study of Atherosclerosis (MESA) cohort, aged 45 to 84 years, free of ASCVD, and not taking lipid-lowering medications at the baseline (2000-2002) (prevalence analytic N = 4623; incidence analytic N = 2216; progression analytic N = 3947). Apo B discordance relative to LDL-C and non-HDL-C was defined using residuals and percentile rankings (>5/10/15 percentile). Associations with prevalent and incident CAC (CAC > 0 vs CAC = 0) were assessed using prevalence ratio/relative risk regression and CAC progression (absolute increase/year) using multinomial logistic regression.

RESULTS

Higher apo B levels were associated with CAC prevalence, incidence, and progression. Apo B discordance relative to LDL-C or non-HDL-C was inconsistently associated with CAC prevalence and progression. Discordantly high apo B relative to LDL-C and non-HDL-C was associated with CAC progression. Associations for apo B discordance with non-HDL-C remained after further adjustment for metabolic syndrome components.

CONCLUSION

Apo B was associated with CAC among adults aged ≥45 years not taking statins, but provided only modest additional predictive value of apo B for CAC prevalence, incidence, or progression beyond LDL-C or non-HDL-C. Apo B discordance may still be important for ASCVD risk assessment and further research is needed to confirm findings.

Metabolic Syndrome as a Multifaceted Risk Factor for Oxidative Stress

SIGNIFICANCE

Metabolic syndrome (MetS) is associated with a greater risk of diabetes and cardiovascular diseases. It is estimated that this multifactorial condition affects 20%-30% of the world's population. A detailed understanding of MetS mechanisms is crucial for the development of effective prevention strategies and adequate intervention tools that could curb its increasing prevalence and limit its comorbidities, particularly in younger age groups. With advances in basic redox biology, oxidative stress (OxS) involvement in the complex pathophysiology of MetS has become widely accepted. Nevertheless, its clear association with and causative effects on MetS require further elucidation. Recent Advances: Although a better understanding of the causes, risks, and effects of MetS is essential, studies suggest that oxidant/antioxidant imbalance is a key contributor to this condition. OxS is now understood to be a major underlying mechanism for mitochondrial dysfunction, ectopic lipid accumulation, and gut microbiota impairment.

CRITICAL ISSUES

Further studies, particularly in the field of translational research, are clearly required to understand and control the production of reactive oxygen species (ROS) levels, especially in the mitochondria, since the various therapeutic trials conducted to date have not targeted this major ROS-generating system, aimed to delay MetS onset, or prevent its progression.

FUTURE DIRECTIONS

Multiple relevant markers need to be identified to clarify the role of ROS in the etiology of MetS. Future clinical trials should provide important proof of concept for the effectiveness of antioxidants as useful therapeutic approaches to simultaneously counteract mitochondrial OxS, alleviate MetS symptoms, and prevent complications. Antioxid. Redox Signal. 26, 445-461.

Usefulness of the LDL-C/apoB ratio in the overall evaluation of atherogenicity of lipid profile

CONTEXT

The ratio of low-density lipoprotein cholesterol to apolipoprotein-B (LDL-C/apoB) conventionally represents an alternative index of LDL particle size.

OBJECTIVE

This study was undertaken to determine the importance of LDL-C/apoB ratio in the overall evaluation of atherogenicity of lipid profile.

METHODS

The plasma levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), apolipoprotein (apo) A-I, apoB and apoE were measured in 186 apparently healthy men using enzymatic and immunoturbidimetric methods.

RESULTS

The subjects with low values of the LDL-C/apoB ratio, indicating a predominance of small dense LDL (sd-LDL) particles in plasma, were characterized by higher TG levels and lower apoE levels.

CONCLUSION

Low levels of apoE are most likely a cause of reduced clearance of TG-rich lipoproteins, which promotes the formation of sd-LDL. Determination of the LDL-C/apoB ratio can be used for monitoring qualitative changes in lipid profile, in addition to traditional lipid variables indicating quantitative changes.

Beneficial effects of rosuvastatin treatment in patients with metabolic syndrome

We determined the effect of 6-month rosuvastatin treatment on blood lipids, oxidative parameters, apolipoproteins, high-sensitivity C-reactive protein, lipoprotein(a), homocysteine, and glycated hemoglobin (HbA1c) in patients with metabolic syndrome (MetS). Healthy individuals (men aged >40 years and postmenopausal women) with a body mass index ≥ 30 (n = 100) who fulfilled the National Cholesterol Education Program Adult Treatment Panel III diagnostic criteria for MetS were included. Total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels decreased (P < .0001). The change in LDL 1 to 3 subgroups was significant (P = .0007, P < .0001, and P = .006, respectively). Changes in LDL 4 to 7 subgroups were not significant. There was a beneficial effect on oxidized LDL, fibrinogen, homocysteine, and HbA1c. Rosuvastatin significantly increased high-density lipoprotein levels (P = .0003). The oxidant/antioxidant status and subclinical inflammatory state were also beneficially changed. Rosuvastatin had a significant beneficial effect on atherogenic dyslipidemia as well as on oxidative stress and inflammatory biomarkers in patients with MetS.

New automated assay of small dense low-density lipoprotein cholesterol identifies risk of coronary heart disease: the Multi-ethnic Study of Atherosclerosis

OBJECTIVE

Coronary heart disease (CHD) is the leading cause of death in the United States, yet assessing risk of its development remains challenging. The present study evaluates a new automated assay of small dense low-density lipoprotein cholesterol content (sdLDL-C) and whether sdLDL-C is a risk factor for CHD compared with LDL-C or small LDL particle concentrations derived from nuclear magnetic resonance spectroscopy.

APPROACH AND RESULTS

sdLDL-C was measured using a new automated enzymatic method, and small LDL concentrations were obtained by nuclear magnetic resonance in 4387 Multi-Ethnic Study of Atherosclerosis participants. Cox regression analysis estimated hazard ratios for developing CHD for 8.5 years after adjustments for age, race, sex, systolic blood pressure, hypertension medication use, high-density lipoprotein cholesterol, and triglycerides. Elevated sdLDL-C was a risk factor for CHD in normoglycemic individuals. Those in the top sdLDL-C quartile showed higher risk of incident CHD (hazard ratio, 2.41; P=0.0037) compared with those in the bottom quartile and indicated greater CHD risk than the corresponding quartile of LDL-C (hazard ratio, 1.75; P=0.019). The association of sdLDL-C with CHD risk remained significant when LDL-C (<2.57 mmol/L) was included in a multivariate model (hazard ratio, 2.37; P=0.012). Nuclear magnetic resonance-derived small LDL concentrations did not convey a significant risk of CHD. Those with impaired fasting glucose or diabetes mellitus showed higher sdLDL-C and small LDL concentrations but neither was associated with higher CHD risk in these individuals.

CONCLUSIONS

This new automated method for sdLDL-C identifies risk for CHD that would remain undetected using standard lipid measures, but only in normoglycemic, nondiabetic individuals.

A Mediterranean-style, low-glycemic-load diet decreases atherogenic lipoproteins and reduces lipoprotein (a) and oxidized low-density lipoprotein in women with metabolic syndrome

The objective was to assess the impact of a Mediterranean-style, low-glycemic-load diet (control group, n = 41) and the same diet plus a medical food (MF) containing phytosterols, soy protein, and extracts from hops and Acacia (MF group, n = 42) on lipoprotein atherogenicity in women with metabolic syndrome. Plasma lipids, apolipoproteins (apos), lipoprotein subfractions and particle size, low-density lipoprotein (LDL) oxidation, and lipoprotein (a) were measured at baseline, week 8, and week 12 of the intervention. Three-day dietary records were collected at the same time points to assess compliance. Compared with baseline, women decreased energy intake from carbohydrate (P < .001) and fat (P < .001), whereas they increased energy intake from protein (P < .001). A significant increase in energy from monounsaturated fatty acids was also observed as well as increases in eicosapentaenoic acid and docosahexaenoic acid, whereas trans-fatty acid intake was reduced (P < .00001). The atherogenic lipoproteins, large very low-density lipoprotein (P < .0001) and small LDL (P < .0001), were reduced, whereas the ratio of large high-density lipoprotein to smaller high-density lipoprotein particles was increased (P < .0001). Apolipoprotein B was reduced for all women (P < .0001), with a greater reduction in the MF group (P < .025). Oxidized LDL (P < .05) and lipoprotein (a) (P < .001) were reduced in both groups at the end of the intervention. Consumption of a Mediterranean-style diet reduces the risk for cardiovascular disease by decreasing atherogenic lipoproteins, oxidized LDL, and apo B. Inclusion of an MF may have an additional effect in reducing apo B.

Plasma kinetics of an LDL-like nanoemulsion and lipid transfer to HDL in subjects with glucose intolerance

OBJECTIVE

Glucose intolerance is frequently associated with an altered plasma lipid profile and increased cardiovascular disease risk. Nonetheless, lipid metabolism is scarcely studied in normolipidemic glucose-intolerant patients. The aim of this study was to investigate whether important lipid metabolic parameters, such as the kinetics of LDL free and esterified cholesterol and the transfer of lipids to HDL, are altered in glucose-intolerant patients with normal plasma lipids.

METHODS

Fourteen glucose-intolerant patients and 15 control patients were studied; none of the patients had cardiovascular disease manifestations, and they were paired for age, sex, race and co-morbidities. A nanoemulsion resembling a LDL lipid composition (LDE) labeled with 14C-cholesteryl ester and ³H-free cholesterol was intravenously injected, and blood samples were collected over a 24-h period to determine the fractional clearance rate of the labels by compartmental analysis. The transfer of free and esterified cholesterol, triglycerides and phospholipids from the LDE to HDL was measured by the incubation of the LDE with plasma and radioactivity counting of the supernatant after chemical precipitation of non-HDL fractions.

RESULTS

The levels of LDL, non-HDL and HDL cholesterol, triglycerides, apo A1 and apo B were equal in both groups. The 14C-esterified cholesterol fractional clearance rate was not different between glucose-intolerant and control patients, but the ³H-free-cholesterol fractional clearance rate was greater in glucose-intolerant patients than in control patients. The lipid transfer to HDL was equal in both groups.

CONCLUSION

In these glucose-intolerant patients with normal plasma lipids, a faster removal of LDE free cholesterol was the only lipid metabolic alteration detected in our study. This finding suggests that the dissociation of free cholesterol from lipoprotein particles occurs in normolipidemic glucose intolerance and may participate in atherogenic signaling.

Observational study of lipid profile and LDL particle size in patients with metabolic syndrome

Background

The atherogenic lipoprotein phenotype is characterized by an increase in plasma triglycerides, a decrease in high-density lipoprotein cholesterol (HDLc), and the prevalence of small, dense-low density lipoprotein cholesterol (LDLc) particles. The aim of this study was to establish the importance of LDL particle size measurement by gender in a group of patients with Metabolic Syndrome (MS) attending at a Cardiovascular Risk Unit in Primary Care and their classification into phenotypes.

Subjects and methods

One hundred eighty-five patients (93 men and 92 women) from several areas in the South of Spain, for a period of one year in a health centre were studied. Laboratory parameters included plasma lipids, lipoproteins, low-density lipoprotein size and several atherogenic rates were determinated.

Results

We found differences by gender between anthropometric parameters, blood pressure and glucose measures by MS status. Lipid profile was different in our two study groups, and gender differences in these parameters within each group were also remarkable, in HDLc and Apo A-I values. According to LDL particle size, we found males had smaller size than females, and patients with MS had also smaller than those without MS. We observed inverse relationship between LDL particle size and triglycerides in patients with and without MS, and the same relationship between all atherogenic rates in non-MS patients. When we considered our population in two classes of phenotypes, lipid profile was worse in phenotype B.

Conclusion

In conclusion, we consider worthy the measurement of LDL particle size due to its relationship with lipid profile and cardiovascular risk.

Small dense LDL cholesterol is a robust therapeutic marker of statin treatment in patients with acute coronary syndrome and metabolic syndrome

BACKGROUND

Small dense low-density lipoprotein (sd-LDL) is an atherogenic LDL subfraction and often increased in metabolic syndrome (MetS). This study aimed to determine whether sd-LDL cholesterol (sd-LDL-C) is a therapeutic marker of statin treatment in patients with acute coronary syndrome (ACS) and MetS.

METHODS

We examined 71 patients with ACS and 50 non-ACS subjects with normal coronary arteries (controls). The patients with ACS were treated with life-style modifications (n=36) or those plus 20mg atorvastatin daily (n=35) for 6 months. We measured sd-LDL-C by a novel detergent-based homogenous assay and calculated buoyant LDL-C (b-LDL-C).

RESULTS

The patients with ACS had higher sd-LDL-C than did the controls (30±14 vs. 22±8 mg/dl, p<0.001). Furthermore, sd-LDL-C was higher in the patients with ACS and MetS (n=31) than in those without MetS (n=40) (35±17 vs. 27±11 mg/dl, p<0.05). Atorvastatin reduced LDL-C and sd-LDL-C by 31% (102±23 to 70±28 mg/dl, p<0.0001) and 24% (29±15 to 22±13 mg/dl, p<0.01). The reduction in sd-LDL-C by atorvastatin was 5.5-fold greater in the patients with ACS and MetS than in those without MetS (p<0.001). Contrary, that in b-LDL-C was similar between the groups.

CONCLUSIONS

sd-LDL-C is a superior therapeutic marker of statin treatment in patients with ACS and MetS.

Dyslipidaemia in the metabolic syndrome and type 2 diabetes: pathogenesis, priorities, pharmacotherapies

IMPORTANCE OF THE FIELD

Dyslipoproteinaemia is a cardinal feature of the metabolic syndrome that accelerates atherosclerosis. It is usually characterized by high plasma concentrations of triglyceride-rich and apolipoprotein B (apoB)-containing lipoproteins, with depressed concentrations of high-density lipoprotein (HDL). Drug interventions are essential for normalizing metabolic dyslipidaemia.

AREAS COVERED IN THIS REVIEW

This review discusses the mechanisms and treatment for dyslipidaemia in the metabolic syndrome and type 2 diabetes.

WHAT THE READER WILL GAIN

A comprehensive understanding of the pathophysiology and pharmacotherapy of dyslipidaemia in the metabolic syndrome and diabetes.

TAKE HOME MESSAGE

Dysregulation of lipoprotein metabolism may be due to a combination of overproduction of triglyceride-rich lipoproteins, decreased catabolism of apoB-containing particles, and increased catabolism of HDL particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance and an excess of both visceral and hepatic fat. Lifestyle modifications may favourably alter lipoprotein transport in the metabolic syndrome. Patients with dyslipidaemia and established cardiovascular disease should receive a statin as first-line therapy. Combination with other lipid-regulating agents, such as ezetimibe, fibrates, niacins and fish oils may optimize the benefit of statin on atherogenic dyslipidaemia.

Long-term use of rosuvastatin: a critical risk benefit appraisal and comparison with other antihyperlipidemics

Rosuvastatin represents the latest inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase introduced in clinical practice for the treatment of hypercholesterolemia. In comparative trials, across dose ranges this statin reduced low-density lipoprotein (LDL) cholesterol and total cholesterol significantly more than atorvastatin, simvastatin, and pravastatin, and triglycerides significantly more than simvastatin and pravastatin. In healthy subjects with normal LDL cholesterol and elevated C-reactive protein, rosuvastatin treatment significantly decreased the incidence of cardiovascular events. Its chemical and pharmacokinetic properties (with a low lipophilicity and poor capacity to inhibit cytochrome P450 enzymes) suggest a very limited penetration in extrahepatic tissues with a lower risk of muscle toxicity and unlike metabolically mediated drug–drug interactions. This article reviews the most recent data on the pharmacologic and clinical properties of rosuvastatin, in order to enable the correct use of this statin for the treatment of hypercholesterolemia.

Small, dense low-density lipoproteins (LDL) are predictors of cardio- and cerebro-vascular events in subjects with the metabolic syndrome

OBJECTIVE

Small, dense low-density lipoproteins (LDL) are a feature of the metabolic syndrome (MS) but their predictive role still remains to be established. We performed a 2-year follow-up study in 124 subjects with MS (63 +/- 6 years), as defined by the American Heart Association/National Heart, Lung and Blood Institute guidelines, to assess clinical and biochemical predictors of cerebro- and cardio-vascular events.

METHODS AND RESULTS

Beyond traditional cardiovascular risk factors, we measured LDL size and subclasses by gradient gel electrophoresis. Clinical events were registered in the 25% of subjects. At univariate analysis subjects with events had increased prevalence of elevated fasting glucose (P = 0.0117), smoking (P = 0.0015), family history of coronary artery disease (P = 0.0033) and higher levels of total- and LDL-cholesterol (P = 0.0027 and P = 0.0023, respectively); LDL size was lower (P < 0.0001), due to reduced larger subclasses and increased small, dense LDL (all P < 0.0001). At multivariate analysis the following were independent predictors of events (univariate odd ratios were calculated): low HDL-cholesterol (OR 15.4, P = 0.0238), elevated fasting glucose (OR 12.1, P = 0.0102), elevated small, dense LDL (OR 11.7, P = 0.0004), elevated blood pressure (OR 9.2, P = 0.0392), smoking (OR 4.8, P = 0.0054).

CONCLUSIONS

This is the first study that assessed the predictive role of small, dense LDL beyond traditional cardiovascular risk factors in subjects with MS.

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.

Quantitative and qualitative effects of rosuvastatin on LDL-cholesterol: what is the clinical significance?

BACKGROUND

Statins have emerged as the global leader in pharmacologic therapy for dyslipidaemia, and rosuvastatin has demonstrated clinical efficacy as well as safety in several clinical trials and postmarketing analyses.

AIM

The present article reviewed the effects of rosuvastatin on the quantity and the quality of low-density lipoproteins (LDL).

METHODS

We searched for and reviewed all the available evidence in a systematic way. A literature search (by Medline and Scopus) was performed using the following headings: 'LDL-cholesterol', 'LDL size', 'LDL subclasses', 'small dense LDL', 'apolipoprotein B, apo B' and 'rosuvastatin' up to 11 November 2008. The authors also manually reviewed the references of selected articles for any pertinent material.

RESULTS

Rosuvastatin reduces LDL-cholesterol levels to a greater extent than other statins and is able to modulate significantly LDL size and subclasses towards less atherogenic particles as well as the LDL particle number, as indirectly measured by the levels of apo B.

DISCUSSION AND CONCLUSIONS

The recent Justification for the Use of statins in Primary prevention: an Intervention Trial Evaluating Rosuvastatin study provides more evidence about the effectiveness of rosuvastatin therapy in reducing cardiovascular risk, even among persons who would not currently be considered for pharmacotherapy. Further insights on cardiovascular outcomes will be available by the on-going trials included in the GALAXY program that includes subjects with type-2 diabetes, haemodialysis recipients, patients with congestive heart failure and specific ethnic groups, such as African American, Hispanic and South Asian populations.

The therapeutic modulation of atherogenic dyslipidemia and inflammatory markers in the metabolic syndrome: what is the clinical relevance?

The metabolic syndrome consists of a constellation of clinical and biochemical risk factors that cluster together and heighten the risk for atherogenesis, cardiovascular diseases, and diabetes. Established risk cardiovascular factors like hypertension, atherogenic dyslipidaemia, and glucose intolerance occur in the setting of insulin resistance and central adiposity, with genetic and environmental influences modulating the ultimate risk. Chronic insults to the endothelium take its toll in the form of silent as well as clinically evident cardiovascular events. The cellular and vascular accompaniments have shed some light into the underlying pathophysiology. Heightened, low-grade inflammatory processes as well as a continuum of vascular insults ranging from early endothelial derangements to advanced atherosclerosis have been examined. In recent years there has been an explosion of basic and clinical knowledge related to the metabolic syndrome. Although dyslipidaemia is considered a traditional risk component for the syndrome, its qualitative aspects, genetically determined subfractions, and variation in proatherogenic tendency have generated renewed interest and debate. New targets within the dyslipidaemic spectrum that have differing clinical relevance are being evaluated. The effect of heredity, lifestyle changes, pharmacotherapeutic agents, and supplements is being investigated. Further research into the impact of dyslipidemia and inflammation as both pathophysiologic risk factors and objects for targeted therapy in the metabolic syndrome should deepen our understanding and unravel answers to the underlying dynamics in this global epidemic.