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

Fibrates: where are we now?

Cardiovascular disease remains a leading cause of mortality worldwide. As dyslipidemia increases cardiovascular disease risk, proper management of dyslipidemia is one means by which to decrease cardiovascular disease risk. This review focuses on dyslipidemia treatment utilizing fibrate therapy, which targets high trigylcerides, low HDL, and high small, dense LDL, while contrasting fibrate therapy with statin therapy and combined therapy. Studies were obtained using electronic search strategies, such as Medline and Cochrane Library. Sources selected were limited to those that discussed fibrates, statins, and combined therapy, with specific emphasis placed on sources that focused on fibrates. Selected studies were then assessed for quality via analysis of the study's methodology, results, and data.

RESULTS

of selected studies were then stratified using a rating system devised to determine the quality of results using the scientific evidence provided for them. Combination fibrate and statin therapy can be more effective in achieving optimal lipid levels than just fibrate or statin therapy alone without significant side effects as long as gemfibrozil is not used in therapy.

Lipid and lipoprotein profiles in youth with and without type 1 diabetes: the SEARCH for Diabetes in Youth case-control study

OBJECTIVE

The purpose of this study was to compare the lipid profile and the prevalence of lipid abnormalities in youth with and without type 1 diabetes and explore the role of glycemic control on the hypothesized altered lipid profile in youth with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a cross-sectional analysis of 512 youth with type 1 diabetes (mean duration 4.22 years) and 188 healthy control subjects aged 10-22 years in Colorado and South Carolina. SEARCH for Diabetes in Youth (SEARCH) participants with type 1 diabetes and healthy control subjects recruited from primary care offices in the same geographic regions were invited to attend a research visit. Fasting lipid profiles were compared between youth with type 1 diabetes (stratified according to categories of optimal [A1C <7.5%] and suboptimal [A1C >or=7.5%] glycemic control) and healthy nondiabetic youth, using multiple linear and logistic regression.

RESULTS

Youth with type 1 diabetes and optimal A1C had lipid concentrations that were similar (total cholesterol, LDL cholesterol, and LDL particle size) or even less atherogenic (HDL cholesterol, non-HDL cholesterol, triglyceride, and triglyceride-to-HDL cholesterol ratio) than those observed in nondiabetic youth, whereas youth with suboptimal glycemic control had elevated standard lipid levels (total cholesterol, LDL cholesterol, and non-HDL cholesterol). Youth with type 1 diabetes also had significantly elevated apolipoprotein B levels and more small, dense LDL particles than nondiabetic youth, regardless of glycemic control.

CONCLUSIONS

Youth with type 1 diabetes have abnormal lipid levels and atherogenic changes in lipoprotein composition, even after a relatively short disease duration. As in adults, glycemic control is an important mediator of these abnormalities.

Interpreting clinical trials of diabetic dyslipidaemia: new insights

Current treatment guidelines highlight the importance of aggressive lipid-modifying therapy in reducing cardiovascular risk in patients with type 2 diabetes. Statins are established as the cornerstone of dyslipidaemia management in diabetic patients, based on their efficacy in lowering levels of low-density lipoprotein cholesterol (LDL-C). However, statins fail to address the high residual cardiovascular risk in treated patients, some of which may be attributable to low HDL cholesterol (HDL-C) and elevated triglycerides and to a preponderance of small, dense LDL particles, indicating the need for further intervention. Fibrates are effective against all components of atherogenic dyslipidaemia associated with type 2 diabetes. Clinical studies, most notably the Fenofibrate Intervention and Event Lowering in Diabetes, indicate that fibrates, most likely in combination with a statin, have a secondary role in reducing cardiovascular risk in patients with type 2 diabetes, particularly in those without prior cardiovascular disease or patients with low HDL-C. Results are awaited from the ongoing Action to Control Cardiovascular Risk in Diabetes trial to fully evaluate the outcome benefits of this combination strategy.

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.

Advanced lipoprotein testing: recommendations based on current evidence

Low-density lipoprotein cholesterol (LDL-C) level currently is used as the major determinant of lipid- and lipoprotein-associated risk for ischemic cardiovascular disease, and varying levels have become the standard goals of lipid-altering treatment. The predictive value of the LDL-C cholesterol level, however, often is less than that provided by other variables such as non-high-density lipoprotein cholesterol (non-HDL-C), apolipoprotein B (apoB), and the number of LDL particles measured by nuclear magnetic resonance spectroscopy. This article reviews studies that compare these different lipoprotein variables, describes advanced methodologies of lipoprotein testing, and suggests goals of treatment and clinical situations in which these tests might be ordered.

Apolipoprotein B and Cardiovascular Disease Risk: Position Statement from the AACC Lipoproteins and Vascular Diseases Division Working Group on Best Practices

Background: Low-density lipoprotein cholesterol (LDL-C) has been the cornerstone measurement for assessing cardiovascular risk for nearly 20 years.

Content: Recent data demonstrate that apolipoprotein B (apo B) is a better measure of circulating LDL particle number (LDL-P) concentration and is a more reliable indicator of risk than LDL-C, and there is growing support for the idea that addition of apo B measurement to the routine lipid panel for assessing and monitoring patients at risk for cardiovascular disease (CVD) would enhance patient management. In this report, we review the studies of apo B and LDL-P reported to date, discuss potential advantages of their measurement over that of LDL-C, and present information related to standardization.

Conclusions: In line with recently adopted Canadian guidelines, the addition of apo B represents a logical next step to National Cholesterol Education Program Adult Treatment Panel III (NCEP ATPIII) and other guidelines in the US. Considering that it has taken years to educate physicians and patients regarding the use of LDL-C, changing perceptions and practices will not be easy. Thus, it appears prudent to consider using apo B along with LDL-C to assess LDL-related risk for an interim period until the superiority of apo B is generally recognized.

Lipid profile, plasma apolipoproteins, and risk of a first myocardial infarction among Asians: an analysis from the INTERHEART Study

OBJECTIVES

This study sought to determine the prevalence of lipid and lipoprotein abnormalities and their association with the risk of a first acute myocardial infarction (AMI) among Asians.

BACKGROUND

Patterns of lipid abnormalities among Asians and their relative impact on cardiovascular risk have not been well characterized.

METHODS

In a case-control study, 65 centers in Asia recruited 5,731 cases of a first AMI and 6,459 control subjects. Plasma levels of lipids and apolipoproteins in the different Asian subgroups (South Asians, Chinese, Southeast Asians, and Japanese) were determined and correlated with the risk of AMI.

RESULTS

Among both cases and controls, mean low-density lipoprotein cholesterol (LDL-C) levels were about 10 mg/dl lower in Asians compared with non-Asians. A greater proportion of Asian cases and controls had LDL-C </=100 mg/dl (25.5% and 32.3% in Asians vs. 19.4% and 25.3% in non-Asians, respectively). High-density lipoprotein cholesterol (HDL-C) levels were slightly lower among Asians compared with non-Asians. There was a preponderance of people with low HDL-C among South Asians (South Asia vs. rest of Asia: cases 82.3% vs. 57.4%; controls 81% vs. 51.6%; p < 0.0001 for both comparisons). However, despite these differences in absolute levels, the risk of AMI associated with increases in LDL-C and decreases in HDL-C was similar for Asians and non-Asians. Among South Asians, changes in apolipoprotein (Apo)A1 predicted risk better than HDL-C. ApoB/ApoA1 showed the strongest association with the risk of AMI.

CONCLUSIONS

The preserved association of LDL-C with risk of AMI among Asians, despite the lower baseline levels, suggests the need to rethink treatment thresholds and targets in this population. The low HDL-C level among South Asians requires further study and targeted intervention.

Combination statin-fibrate therapy: safety aspects

Patients with type 2 diabetes or metabolic syndrome remain at high residual risk of cardiovascular events even after intensive statin therapy. While treatment guidelines recommend the addition of a fibrate to statin therapy in this setting, concerns about the potential for myopathy may limit the use of this combination in clinical practice. These concerns are certainly justified for gemfibrozil, which interferes with statin glucuronidation, leading to elevation in statin plasma concentrations and an increased risk of myotoxicity in combination with a range of commonly prescribed statins. However, the available evidence refutes suggestions that this is a class effect for fibrates. Fenofibrate does not adversely influence the metabolism or pharmacokinetics of any of the commonly prescribed statins. This in turn translates to a reduced potential for myotoxicity in combination with a statin. Data are awaited from the ongoing Action to Control Cardiovascular Risk in Diabetes (ACCORD) study to evaluate the efficacy and safety of fenofibrate plus simvastatin combination therapy in type 2 diabetes patients.

The SLIM Study: Slo-Niacin® and Atorvastatin Treatment of Lipoproteins and Inflammatory Markers in Combined Hyperlipidemia

BACKGROUND: The combination of niacin and statin has proven value in hyperlipidemia management and heart disease prevention. However, the efficacy of the non-prescription time-release niacin, Slo-Niacin®, is little studied alone and not at all with atorvastatin. We gave Slo-Niacin® and atorvastatin, singly and together to determine efficacy on the combined abnormalities of triglyceride, LDL and HDL. METHODS: 42 men and women with LDL-C>130mg/dL HDL-C <45 (men or 55mg/dL (women) were randomized to 3 months of atorvastatin 10 mg/day or incremental doses of Slo-Niacin® to 1500 mg/day. The alternate drug was added in the next 3-month segment. Lipid profiles and transaminases were measured monthly and other measures at baseline and the end of each treatment sequence. RESULTS: Mean entry lipids (mg/dL) were: TG 187, LDL-C 171, and HDL-C 39. Mean BMI was 32.6 Kg/m(2). Monotherapy with Slo-Niacin® decreased median triglyceride 15%, mean LDL-C 12% and non-HDL-C 15% and increased HDL-C 8%. Atorvastatin decreased median triglyceride 26%, and mean LDL-C 36%, non-HDL-C 36% and increased HDL-C 6%. Combined therapy decreased median triglyceride 33% and mean LDL-C and non-HDL-C each 43%. HDL-C increased 10% (all p<0.001). Median remnant-like lipoprotein-C decreased 55%, mean apo-B 40%, median hsCRP 23% (all p<0.05), TNFa 12% and no change in IL-6. Mean LDL buoyancy increased 15%, apo-A-I 5% and median HDL(2)-C 20% (all p<0.05). ALT declined with Slo-Niacin® treatment alone compared to atorvastatin and also decreased when Slo-Niacin® was added to atorvastatin. Six subjects dropped out, 3 for niacin related symptoms. CONCLUSIONS: Slo-Niacin® 1.5g/day with atorvastatin 10 mg/day improved lipoprotein lipids, apoproteins and inflammation markers without hepatotoxicity. Slo-Niacin® deserves further study as a cost-effective treatment of hyperlipidemia.

Estimation of VLDL, IDL, LDL, HDL2, apoA-I, and apoB from the Friedewald inputs--apoB and IDL, but not LDL, are associated with mortality in type 1 diabetes

BACKGROUND

There is an unmet need for a straightforward and cost-effective assessment of multiple lipoprotein risk factors for vascular diseases.

AIMS

1) To study the relation of various lipoprotein lipid and apolipoprotein (apo) measures on the Friedewald inputs, i.e. plasma triglycerides (TG), cholesterol (TC), and high-density lipoprotein cholesterol (HDL-C). 2) To build up regression models for the appropriate measures based solely on the Friedewald inputs.

METHODS

Data were available for 1,775 plasma samples, from which very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and HDL were also isolated by ultracentrifugation. For HDL(2)-C and apolipoproteins, 343 and 247 samples were available, respectively.

RESULTS

Accurate models were obtained for VLDL-TG (cross-validation r=0.98), LDL-C (r=0.91), HDL(2)-C (r=0.92), apoA-I (r=0.92), and apoB (r=0.95). A semi-quantitative model was obtained for IDL-C (r=0.78). Due to the anticipated role of IDL-C in atherosclerosis, it was still kept within the accepted models and pursued further. The associations of the estimates with premature deaths were studied in 4,084 patients with type 1 diabetes. The associations of IDL-C and LDL-C were markedly different, the best predictors of mortality being apoB, apoB to apoA-I ratio, and IDL-C.

CONCLUSIONS

The new models allow identification of clinically relevant lipoprotein profiles with no added cost to the conventional Friedewald formula.

Atherogenic lipoprotein phenotype and LDL size and subclasses in women with gestational diabetes

AIMS

Women with gestational diabetes are more likely to develop Type 2 diabetes and cardiovascular disease after pregnancy; however, the exact nature of the lipid alterations present is not clear. In Mediterranean women with gestational diabetes, we measured low-density lipoprotein (LDL) size and all seven subclasses, as well as the 'atherogenic-lipoprotein phenotype'[ALP, e.g. concomitant presence of elevated triglycerides, reduced high-density lipoprotein (HDL)-cholesterol and increased small, dense LDL].

METHODS

In 27 women with gestational diabetes and 23 healthy pregnant women matched for age, weeks of gestation and body mass index, we measured plasma lipids and LDL size and subclasses by gradient gel electrophoresis between 24 and 28 weeks of gestation.

RESULTS

Although no significant differences were found in the concentrations of any of the plasma lipids, compared with control subjects women with gestational diabetes had lower LDL size (P = 0.0007) due to reduced LDL-I (P = 0.0074) and increased LDL-IVA (P = 0.0146) and -IVB (P < 0.0001) subclasses. Correlation analysis revealed that fasting glucose, homeostasis model assessment and glycated haemoglobin were inversely correlated with LDL-I and positively with LDL-IVA and -IVB (all P < 0.05). ALP due to high HDL-cholesterol levels was not seen in either group, whereas elevated small, dense LDL were more common in women with gestational diabetes than control subjects (33% vs. 4%, P = 0.0107).

CONCLUSIONS

Increased levels of small, dense LDL are common in Mediterranean women with gestational diabetes. Whether these findings affect the atherogenic process and clinical end-points in these women remains to be determined by future prospective studies.

A rapid 3% polyacrylamide slab gel electrophoresis method for high through put screening of LDL phenotype

Background

Small dense LDL is reported to be associated with increased coronary artery disease risk by various epidemiological studies. The gold standard for separation and identification of LDL subtypes in plasma is ultracentrifugation which is a lengthy procedure and difficult to perform. Various other methods like NMR, HPLC, gradient gel electrophoresis (GGE) have been reported for LDL sub fractionation all of which require specialized equipments and expertise. We report here a high throughput 3% polyacrylamide slab gel electrophoresis method (PASGE) for sub fractionation of LDL which was compared with GGE, a commonly used method for LDL sub fractionation.

Results

The 3% PASGE method compared well with the GGE method There was a good correlation between LDL particle diameter identified by the PASGE and GGE (Pearson correlation coefficient = 0.950). A 100% concordance was found when samples were classified as per LDL phenotypes in subjects with A and B phenotype by the two methods with the concordance being 66% in subjects with intermediate (I) phenotype. The electrophoresis apparatus was optimized and designed for running twenty eight samples at a time compared to twelve to fourteen by the conventional PASGE and eight to twelve by disc electrophoresis.

Conclusion

The rapid 3% polyacrylamide slab gel electrphoresis method developed is simple to perform, cost-effective and can be used for the identification LDL sub fractionation and phenotyping in large epidemiological studies.

Is it LDL particle size or number that correlates with risk for cardiovascular disease?

The role of low-density lipoprotein cholesterol (LDL-C) in the pathogenesis of cardiovascular disease (CVD) and the clinical benefit of lowering LDL-C in high-risk patients is well established. What remains controversial is whether we are using the best measure(s) of LDL characteristics to identify all individuals who are at CVD risk or if they would benefit from specific therapies. Despite the successful LDL-C reduction trials, substantial numbers of patients continue to have clinical events in the treatment groups. The size of LDL particles and assessment of the number of LDL particles (LDL-Num) have been suggested as a more reliable method of atherogenicity. Each LDL particle has one apoprotein B-100 measure attached; therefore, determination of whole plasma apoprotein B can be considered the best measure of LDL-Num. Because the cholesterol content per LDL particle exhibits large interindividual variation, the information provided by LDL-C and LDL-Num is not equivalent. Individuals with the same level of LDL-C may have higher or lower numbers of LDL particles and, as a result, may differ in terms of absolute CVD risk. LDL particle size and number provide independent measures of atherogenicity and are strong predictors of CVD.

The Residual Risk Reduction Initiative: a call to action to reduce residual vascular risk in dyslipidaemic patient

Despite current standards of care aimed at achieving targets for low-density lipoprotein (LDL) cholesterol, blood pressure and glycaemia, dyslipidaemic patients remain at high residual risk of vascular events. Atherogenic dyslipidaemia, specifically elevated triglycerides and low levels of high-density lipoprotein (HDL) cholesterol, often with elevated apolipoprotein B and non-HDL cholesterol, is common in patients with established cardiovascular disease, type 2 diabetes, obesity or metabolic syndrome and is associated with macrovascular and microvascular residual risk. The Residual Risk Reduction Initiative (R3I) was established to address this important issue. This position paper aims to highlight evidence that atherogenic dyslipidaemia contributes to residual macrovascular risk and microvascular complications despite current standards of care for dyslipidaemia and diabetes, and to recommend therapeutic intervention for reducing this, supported by evidence and expert consensus. Lifestyle modification is an important first step. Additionally, pharmacotherapy is often required. Adding niacin, a fibrate or omega-3 fatty acids to statin therapy improves achievement of all lipid risk factors. Outcomes studies are evaluating whether these strategies translate to greater clinical benefit than statin therapy alone. In conclusion, the R3I highlights the need to address with lifestyle and/or pharmacotherapy the high level of residual vascular risk among dyslipidaemic patients who are treated in accordance with current standards of care.

The effects of ezetimibe on LDL-cholesterol: quantitative or qualitative changes?

Ezetimibe represents the first of a new class of agents, the cholesterol absorption inhibitors, able to reduce low-density lipoproteins (LDL)-cholesterol by 15-25% from baseline in monotherapy and on top of statins and fibrates. To-date all the data regarding the efficacy of ezetimibe comes from the studies of its lipid-lowering power. Yet, recent findings from the ENHANCE study on atherosclerosis progression showed that the addition of ezetimibe to simvastatin in patients with heterozygous familial hypercholesterolemia did not affect the mean change in carotid intima-media thickness, although a significant reduction in LDL-cholesterol levels was present. Therefore, we cannot exclude that ezetimibe is treating mainly LDL-cholesterol and not the underlying dyslipidemia. Reviewing all available evidences on the effects on atherogenic small, dense LDL, it seems that ezetimibe produce quantitative rather than qualitative changes in LDL, with small net effects on LDL subclass distribution. Yet, we cannot exclude that clinical and laboratory factors influenced this result. We found important differences in the methodology used to measure LDL size and subfractions and this represents a crucial point, since these methods cannot be fully used interchangeably. In addition, it is reasonable to imagine that ezetimibe may be more effective on small, dense LDL in subjects with hypertriglyceridemia. Further formal cardiovascular event outcome trials are underway and this will provide additional insights into the long-term effects of ezetimibe. Future prospective studies are also needed to clarify to which extent ezetimibe is able to reduce atherogenic dyslipidemia, beyond LDL-cholesterol levels.

Implications of the obesity epidemic for lipid-lowering therapy: non-HDL cholesterol should replace LDL cholesterol as the primary therapeutic target

Obesity, metabolic syndrome and diabetes are conditions with increasing prevalence around the world. Cardiovascular risk in diabetics is often so high as to overlap with event rates observed in those with established coronary disease and this has lead to diabetes being classified as a coronary risk equivalent. However, despite the elevated risk of cardiovascular events associated with diabetes and the metabolic syndrome, these patients often have normal low density lipoprotein (LDL) cholesterol despite frequent increases in apolipoprotein B, triglycerides and nonhigh density lipoprotein (HDL) cholesterol. In contrast to LDL cholesterol, non-HDL cholesterol represents cardiovascular risk across all patient populations but is currently only recommended as a secondary target of therapy by the ATP III report for patients with hypertriglyceridemia. This article provides an overview of the studies that shown non-HDL cholesterol to be superior to LDL cholesterol in predicting cardiovascular events and presents the case for non-HDL cholesterol being the more appropriate primary target of therapy in the context of the obesity pandemic. Adopting non-HDL cholesterol as the primary therapeutic target for all patients will conceivably lead to an appropriate intensification of therapy for high risk patients with low LDL cholesterol.

Effects of sibutramine plus verapamil sustained release/trandolapril combination on blood pressure and metabolic variables in obese hypertensive patients

OBJECTIVE

The management of obese hypertensive subjects may require the administration of anti-obesity and antihypertensive drugs. Sibutramine use has raised concerns regarding a potential increase in subjects' blood pressure and heart rate. The primary end-points of this study were an evaluation of the effect of sibutramine together with a verapamil sustained release/trandolapril combination tablet versus verapamil sustained release/trandolapril alone on the blood pressure and heart rate in obese hypertensive patients.

RESEARCH DESIGN/METHODS

Patients received a low-fat low-calorie diet and were randomly allocated to open-label verapamil sustained release/trandolapril 180/2 mg (n = 26) or sibutramine 10 mg together with verapamil sustained release/trandolapril 180/2 mg (n = 28) daily for 6 months.

RESULTS

Significant reductions in the subjects' systolic blood pressure and diastolic blood pressure were observed in both groups (p < 0.01 versus baseline). At 6 months a greater fall in blood pressure was observed in the sibutramine/verapamil sustained release/trandolapril group compared with the verapamil sustained release/trandolapril group (systolic blood pressure 21.9 +/- 8.1 versus 15.9 +/- 12.3 mmHg and diastolic blood pressure 15.7 +/- 8.1 versus 9.1 +/- 9.9 mmHg) but this was only significant (p = 0.03) for diastolic blood pressure. The subjects' heart rate did not change significantly in any group. No significant sibutramine-associated attenuation of blood pressure reduction was observed during the study. The sibutramine/verapamil sustained release/trandolapril treatment resulted in significantly greater improvement in the subjects' anthropometric variables, homeostasis model assessment and lipid profiles compared with verapamil sustained release/trandolapril administration. The subjects' small dense low-density lipoprotein cholesterol, high-sensitivity C-reactive protein and visfatin plasma levels were only measured in the sibutramine/verapamil sustained release/trandolapril group (all decreased by p < 0.05 versus baseline).

CONCLUSIONS

The sibutramine/verapamil sustained release/trandolapril combination in obese hypertensive patients significantly reduced their blood pressure and improved their anthropometric and metabolic variables without affecting the heart rate.

Review: Does lowering cholesterol have an impact on the progression of aortic stenosis?

Several studies suggest that atherosclerotic disease is not a focal disease restricted to culprit lesions in the intima of the arterial wall, but seems to act as a general disease affecting the entire cardiovascular system. Evolving research has lately focused on the atherosclerotic component in calcific aortic stenosis (AS) as it seems that the valve is affected in a pattern similar to that of the vasculature. The hope is therefore, that we someday in the management of patients with calcific AS can apply some of the same treatment strategies as in atherosclerotic vascular disease. This article reviews the pathophysiological mechanisms of calcific AS, reviews current clinical trials of statin use in aortic stenosis and reports on on-going trials, evaluating whether cholesterol lowering therapy can slow disease progression in different populations. Finally, we review if computerized tomography, biomarkers, and clinical characteristics such as left ventricular ejection fraction, can be useful in stratifying patients to potential benefit of statin therapy.

Beyond high-density lipoprotein cholesterol levels evaluating high-density lipoprotein function as influenced by novel therapeutic approaches

A number of therapeutic strategies targeting high-density lipoprotein (HDL) cholesterol and reverse cholesterol transport are being developed to halt the progression of atherosclerosis or even induce regression. However, circulating HDL cholesterol levels alone represent an inadequate measure of therapeutic efficacy. Evaluation of the potential effects of HDL-targeted interventions on atherosclerosis requires reliable assays of HDL function and surrogate markers of efficacy. Promotion of macrophage cholesterol efflux and reverse cholesterol transport is thought to be one of the most important mechanisms by which HDL protects against atherosclerosis, and methods to assess this pathway in vivo are being developed. Indexes of monocyte chemotaxis, endothelial inflammation, oxidation, nitric oxide production, and thrombosis reveal other dimensions of HDL functionality. Robust, reproducible assays that can be performed widely are needed to move this field forward and permit effective assessment of the therapeutic potential of HDL-targeted therapies.

The effect of orlistat and ezetimibe, alone or in combination, on serum LDL and small dense LDL cholesterol levels in overweight and obese patients with hypercholesterolaemia

BACKGROUND

Increased concentrations of low density lipoprotein cholesterol (LDL-C), as well as of small dense LDL-C (sdLDL-C), are considered as cardiovascular risk factors.

OBJECTIVE

An assessment of the effects of ezetimibe and orlistat administration, alone or in combination, on LDL-C and sdLDL-C levels (primary endpoint), as well as on anthropometric variables and metabolic parameters (secondary endpoints) in overweight and obese patients [body mass index (BMI)>28 kg/m(2)] with hypercholesterolaemia [total cholesterol>200 mg/dL (5.2 mmol/L)].

METHODS

Eighty six subjects were prescribed a low-fat low-calorie diet and were randomly allocated to receive orlistat 120 mg, 3 times daily (O group), ezetimibe 10 mg/day (E group) or both (OE group) for 6 months.

RESULTS

Significant reductions in LDL-C (-19%, -21%, -32% in groups O, E and OE, respectively, all p<0.01 vs. baseline) and sdLDL-C levels (-45%, -48%, -76% in groups O, E, OE, respectively, all p<0.01 vs. baseline) were observed. Group OE experienced a significantly greater reduction in LDL-C and sdLDL-C levels compared with groups O and E (p<0.05). Furthermore, significant reductions of BMI, homeostasis model assessment (HOMA) index, serum uric acid, transaminase activities and plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) activity were observed in the O and OE groups. Gamma-glutamyl transpeptidase activity and Lp-PLA(2) activity improved significantly more with the combination treatment compared with either orlistat or ezetimibe monotherapy.

CONCLUSIONS

Orlistat and ezetimibe combination had a more favourable effect on LDL-C and sdLDL-C levels in overweight and obese hypercholesterolaemic patients than either drug alone. Furthermore, orlistat, alone or in combination with ezetimibe, additionally improved several anthropometric and metabolic variables.

Direct determination of lipoprotein particle sizes and concentrations by ion mobility analysis

BACKGROUND

Current methods for measuring the concentrations of lipoprotein particles and their distributions in particle subpopulations are not standardized. We describe here and validate a new gas-phase differential electrophoretic macromolecular mobility-based method (ion mobility, or IM) for direct quantification of lipoprotein particles, from small, dense HDL to large, buoyant, very-low-density lipoprotein (VLDL).

METHODS

After an ultracentrifugation step to remove albumin, we determined the size and concentrations of lipoprotein particles in serum samples using IM. Scan time is 2 min and covers a particle range of 17.2-540.0 A. After scanning, data are pooled by totaling the particle number across a predetermined size range that corresponds to particular lipoprotein subclasses. IM results were correlated with those of standard methods for cholesterol and apolipoprotein analysis.

RESULTS

Intra- and interassay coefficients of variation for LDL particle size were <1.0%. The intra- and interassay variation for LDL and HDL particle subfraction measurements was <20%. IM-measured non-HDL correlated well with apolipoprotein B (r = 0.92).

CONCLUSIONS

The IM method provides accurate, reproducible, direct determination of size and concentration for a broad range of lipoprotein particles. Use of this methodology in studies of patients with cardiovascular disease and other pathologic states will permit testing of its clinical utility for risk assessment and management of these conditions.

Ezetimibe: cholesterol lowering and beyond

Ezetimibe is a cholesterol absorption inhibitor that blocks the intestinal absorption of both biliary and dietary cholesterol. It appears to exert its effect by blocking intestinal sterol transporters, specifically Niemann-Pick C1-like 1 proteins, thereby inhibiting the intestinal absorption of cholesterol, phytosterols and certain oxysterols. Ezetimibe monotherapy and in combination with statin therapy is primarily indicated for lowering LDL-cholesterol levels. In addition, it may favorably affect other parameters that could potentially further reduce atherosclerotic coronary heart disease risk, such as raising HDL-cholesterol and lowering levels of triglycerides, non-HDL-cholesterol, apolipoprotein B and remnant-like particle cholesterol. Further effects of ezetimibe include a reduction in circulating phytosterols and oxysterols and, when used in combination with statins, a reduction in high-sensitivity C-reactive protein. The clinical significance of the LDL-cholesterol lowering and other effects of ezetimibe is being evaluated in clinical outcome studies.

Hypothyroidism results in small dense LDL independent of IRS traits and hypertriglyceridemia

There is evidence of an association between hypothyroidism and coronary heart disease. We decided to look at the relationship between hypothyroidism and LDL subclasses' pattern including small, dense LDL to define a biochemical basis for better management of the CHD risk of these patients. We utilized a case-control design to evaluate differences in lipid parameters between cases and controls. Univariate analysis revealed that many factors were associated with LDL particle size. Binary logistic regression however revealed that only thyroid status and serum triglyceride (TG) levels were independently associated with LDL particle size. Results from this study support an independent association between LDL particle size phenotype and both plasma TG concentrations and thyroid status. After adjusting for TG levels, other insulin resistance syndrome (IRS) traits were not associated with LDL size phenotype, suggesting that the IRS related sdLDL is linked most strongly to alterations in TG levels.

Combination therapy in the management of mixed dyslipidaemia

Whilst statin monotherapy is often sufficient to reach LDL-C goals, treatment may not reach all lipid goals in individuals with mixed dyslipidaemia typically associated with metabolic syndrome or type 2 diabetes. Double or triple combination therapy, which provides the opportunity to address multiple lipid abnormalities simultaneously, may be required to achieve targets in some patients. Addition of fenofibrate or niacin (nicotinic acid) to statin therapy is likely to be the first option, as recommended by national treatment guidelines; omega-3 fatty acids may also be useful. Careful monitoring is required when adding additional agents given the increased potential for drug interactions and side effects.

Dyslipidemia in children with type 2 diabetes vs. obesity

OBJECTIVE

To compare the frequency and severity of dyslipidemia between subjects with type 2 diabetes (T2DM) and non-diabetic obese group (OB) subjects, followed in a pediatric subspecialty clinic.

RESEARCH DESIGN AND METHODS

One hundred and four OB subjects seen consecutively by one physician and 67 pediatric subjects diagnosed with T2DM (negative antibodies) were screened from an institutional review board-approved database. Fifty-two T2DM and 75 OB subjects with fasting lipid profiles measured at one hospital's laboratory were included.

RESULTS

Both OB and T2DM subjects were predominantly Mexican American. Comparing T2DM at diagnosis or uncontrolled (UC) and OB, mean +/- SD age was 14.3 +/- 2.3 and 11.4 +/- 3.7 with body mass index-Z score of 2.02 +/- 0.67 and 2.46 +/- 0.45, respectively (both p < 0.01). Comparing lipid levels in T2DM to OB and National Health and Nutrition Examination Survey III, the percentage of subjects, respectively, with cholesterol >200 mg/dL (5.17 mmol/L) were 55.8, 22.7, and 10%; with low-density lipoprotein >130 mg/dL (3.36 mmol/L) were 39.4, 12.5, and 10%; with triglycerides >150 mg/dL (1.68 mmol/L) were 65.1, 38.7, and 12.5%; and with high-density lipoprotein <35 mg/dL (0.91 mmol/L) were 40, 22.2, and 10%. Over 80% of the T2DM subjects improved their lipid profile with improved glycemic control as hemoglobin A1c decreased from 10.85 +/- 2.17 to 7.6 +/- 2%.

CONCLUSIONS

Dyslipidemia is a frequent comorbidity of obesity and T2DM, starting in childhood, and poses a major public health risk. Dyslipidemia in pediatric subjects with UC T2DM is significantly worse than in OB subjects but is similar to OB subjects when diabetes was better controlled. Earlier use of lipid-lowering drugs should be considered in pediatric T2DM patients who achieve tight glycemic control, yet their dyslipidemia persists.

Hypertriglyceridaemic waist phenotype criteria and prevalent metabolic triad in women

BACKGROUND

To assess the metabolic profile and the prevalence of the metabolic triad (i.e. hyperinsulinaemia, hyperapobetalipoproteinaemia, and decreased low-density lipoprotein particle size) in women characterized by the hypertriglyceridaemic waist (HTGW) phenotype and to identify cut-off values for triglycerides and waist circumference, effectively discriminating women with the metabolic triad.

METHODS

Two hundred and twenty-eight female subjects without any history of vascular disease or diabetes mellitus attending an Outpatient Lipid Clinic setting at the University Hospital of Ioannina, Greece were studied.

RESULTS

Currently available HTGW criteria for women were unable to detect any significant differences in the metabolic profile either in the pre- or post-menopausal women, and proved similar in terms of sensitivity and specificity in identifying women with the metabolic triad. A cut-off value of 1.26 mmol/L for triglycerides and 84.5 cm for waist circumference were determined by Receiver-operating Curve evaluation. Women with both triglycerides and waist circumference above these thresholds had four-fold higher odds of presenting with the metabolic triad compared with women with non-HTGW phenotype.

CONCLUSIONS

A HTGW phenotype definition of 1.26 mmol/L for triglycerides and 84.5 cm for waist circumference may effectively identify Mediterranean women with the atherogenic metabolic triad. Whether these criteria are also associated with a higher incidence of vascular disease and/or new-onset diabetes in women remains to be investigated.

Prevalence and determinants of elevated apolipoprotein B and dense low-density lipoprotein in youths with type 1 and type 2 diabetes

OBJECTIVE

The objective of the study was to assess the prevalence and determinants of elevated apolipoprotein B (apoB) and dense low-density lipoprotein (LDL) in United States youth with type 1 or type 2 diabetes.

METHODS

We conducted cross-sectional analyses of apoB concentrations, LDL density, and prevalence of elevated apoB levels and dense LDL from the SEARCH for Diabetes in Youth study, a six-center U.S.-based study of youth with diabetes onset younger than 20 years of age (2657 with type 1 and 345 with type 2).

RESULTS

Among youth with type 1 diabetes, 11% had elevated apoB (>or=100 mg/dl, 1.95 mm/liter), 8% had dense LDL (relative flotation rateor=130 mg/dl, 3.36 mm/liter). In contrast, among youth with type 2 diabetes, 36% had elevated apoB, 36% had dense LDL, but only 23% had elevated LDL-cholesterol. Dense LDL and apoB each increased with hemoglobin A1c in both types. Among type 1 diabetics in poor glycemic control (hemoglobin A1c>or=9.5%), 28% had elevated apoB, and 18% had dense LDL, whereas 72% of poorly controlled type 2 diabetics had elevated apoB and 62% had dense LDL.

CONCLUSIONS

In youth with type 1 diabetes, elevated apoB and dense LDL were not highly prevalent, whereas elevated apoB and dense LDL were common lipoprotein abnormalities in youth with type 2 diabetes. The prevalence of these risk factors substantially increased with poor glycemic control in both groups, stressing the importance of achieving and maintaining an optimal glucose control.

PAI-1 activity, but not fibrinogen or von Willebrand factor, is inversely related to LDL particle size in type 2 diabetes

BACKGROUND

Levels of fibrinogen, von Willebrand factor (vWF) and plasminogen activator inhibitor-1 (PAI-1) have been associated with small low-density lipoprotein (LDL) particles. However, it is not clear whether these associations are independent of visceral adiposity or other components of the metabolic syndrome such as triglycerides or insulin resistance.

METHODS

Visceral adipose tissue (VAT; CT-scan), fibrinogen, von Willebrand factor antigen (vWF:Ag), PAI-1 activity and different metabolic parameters such as total cholesterol (chol), HDL-chol, triglycerides, insulin resistance (homeostasis model assessment; HOMA-IR) were determined in 41 women and 78 men with type 2 diabetes. LDL particle size was assessed by polyacrylamide gradient gel electrophoresis.

RESULTS

PAI-1 activity was inversely related to LDL particle size after adjustment for age and body mass index (BMI) (r=-0.28; p=0.006) or age and VAT (r=-0.26; p=0.01), but not after adjustment for age and HOMA-IR (r=-0.15; p=0.148) or age and triglycerides (r=-0.04; p=0.679). In multiple regression analysis, LDL particle size did not independently determine PAI-1 activity levels. Fibrinogen and vWF:Ag did not seem to be related to LDL size.

CONCLUSIONS

PAI-1 activity levels, in contrast to fibrinogen and vWF:Ag, seem to be related to the small LDL phenotype in patients with type 2 diabetes. However, this relationship was not independent of insulin resistance or triglycerides.

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

BACKGROUND

Small dense low-density lipoprotein (LDL) particles are known to be especially atherogenic. Several mechanisms are involved in this atherogenicity.

AIMS

We wanted to look for the presence of small dense LDL particles depending on gender, metabolic syndrome (MS) and different degrees of glucose intolerance. Moreover, we looked for anthropometric factors and factors of lipid and carbohydrate metabolism that are associated with changes in the LDL size.

RESULTS

We studied 752 persons (330 males, 422 females; age 40 +/- 17 years). LDL particle size was estimated with polyacrylamide gel electrophoresis. Males had smaller LDL particles than females. Probands with the MS had smaller LDL particles than those without this syndrome. With rising plasma triglyceride (TG) levels more small dense LDL particles were seen. The highest proportion of these small dense LDL particles was observed in the subgroup of type 2 diabetic patients. In the whole material, the mean LDL diameter was correlated negatively with plasma TG and very low-density lipoprotein components (TG, cholesterol and proteins) and positively with high-density lipoprotein cholesterol. In a linear stepwise regression analysis different significant factors influencing the LDL size were found in the whole population, in normoglycaemic probands, in persons with impaired glucose tolerance, in type 2 diabetic patients and in type 2 diabetic patients injecting insulin.

CONCLUSIONS

Our data point to different mechanisms of the formation of small dense LDL particles in dependence on the degree of glucose intolerance. Moreover, the target values for plasma TG should be set lower.

Association between plasma LDL particle size, valvular accumulation of oxidized LDL, and inflammation in patients with aortic stenosis

OBJECTIVE

In patients with severe aortic stenosis (AS), we examine the association between: (1) the content of oxidized LDL (oxLDL) in the aortic valve and the degree of inflammation and remodeling; (2) The proportion of small dense LDL particles in the plasma and the presence of oxLDL in the valve along with hemodynamic progression of valve stenosis.

METHODS AND RESULTS

We have examined 102 explanted AS valves. Tissue remodeling, inflammation, and accumulation of oxLDL were determined. A complete plasma lipid profile including the measurement of the relative proportion of small low-density lipoprotein (%LDL(<255A)) was obtained. Valves with higher oxLDL content had a significantly higher density of inflammatory cells, expression of tumor necrosis factor (TNF)-alpha, and increased tissue remodeling score. The %LDL(<255A) was significantly associated with oxLDL score within the aortic valve. In a subset of 59 patients in whom stenosis progression was measured, the %LDL(<255A) correlated with the annualized peak gradient (r=0.29; P=0.04).

CONCLUSIONS

Increased proportion of circulating small dense LDL particles is associated with faster progression rate of stenosis and greater accumulation of oxLDL in the aortic valve. These findings suggest that therapeutic interventions aimed at lowering the production of small dense LDL particles in patients with AS might represent a potentially interesting therapeutic avenue.

Small, dense low-density lipoprotein and C-reactive protein in obese subjects with and without other criteria for the metabolic syndrome

BACKGROUND

Although obesity is an important cardiovascular risk factor, growing evidence shows that a substantial portion of obese subjects can be considered metabolically healthy but obese (MHO). However the extent to which obese subjects manifest small, dense low-density lipoprotein (LDL) particles without other characteristics of the metabolic syndrome (MS) remains unknown.

OBJECTIVE

The purpose of this study was to determine the difference between MHO (only meeting the obesity criteria) and obese subjects meeting all the criteria for the MS with regard to LDL size and high-sensitivity C-reactive protein (hs-CRP), as a biomarker of inflammation.

METHODS

Two hundred obese subjects (168 women, mean age 36.5 ± 5 years [range, 20-60]; mean body mass index [BMI; calculated as kg/m(2)] 39 ± 5 [range, 30-80.4]) were studied for LDL particles size and hs-CRP levels.

RESULTS

Of 200 enrolled obese subjects, 55 were defined MHO subjects meeting only obesity criteria. The other 145 met all five criteria and were defined as having MS. Although MHO and MS subjects had similar BMI, MHO subjects had a lower percentage of small LDL particles (8% vs 29%, P < 0.001), higher average LDL diameter (274 ± 5 vs 270 ± 7 Å, P < 0.001), and lower hs-CRP levels (P < 0.05) than MS patients.

CONCLUSION

The major finding of this study is that MHO subjects compared to equally obese subjects meeting the criteria of the MS have statistically significant differences in size of LDL and concentration of hs-CRP. However, the absolute differences are very small and of uncertain clinical significance.

Bovine milk in human nutrition--a review

Milk and milk products are nutritious food items containing numerous essential nutrients, but in the western societies the consumption of milk has decreased partly due to claimed negative health effects. The content of oleic acid, conjugated linoleic acid, omega-3 fatty acids, short- and medium chain fatty acids, vitamins, minerals and bioactive compounds may promote positive health effects. Full-fat milk has been shown to increase the mean gastric emptying time compared to half-skimmed milk, thereby increasing the gastrointestinal transit time. Also the low pH in fermented milk may delay the gastric emptying. Hence, it may be suggested that ingesting full-fat milk or fermented milk might be favourable for glycaemic (and appetite?) regulation. For some persons milk proteins, fat and milk sugar may be of health concern. The interaction between carbohydrates (both natural milk sugar and added sugar) and protein in milk exposed to heat may give products, whose effects on health should be further studied, and the increasing use of sweetened milk products should be questioned. The concentration in milk of several nutrients can be manipulated through feeding regimes. There is no evidence that moderate intake of milk fat gives increased risk of diseases.

Serum concentration of small dense low-density lipoprotein-cholesterol during oral glucose tolerance test and oral fat tolerance test

BACKGROUND

Small dense low-density lipoprotein (sdLDL) is well known as an atherogenic lipoprotein. We developed a new assay to measure serum concentration of sdLDL-cholesterol (sdLDLC). Using this assay, we reported a unique circadian rhythm of sdLDLC. We determined whether a glucose intake and/or a fat intake affects on serum sdLDLC concentration and determined the modulators of serum sdLDLC concentration.

METHODS

Ten healthy volunteers were recruited to perform both a 75 g oral glucose tolerance test (OGTT) and an oral fat tolerance test (OFTT) to determine the effects of glucose and fat ingestion separately. Blood was measured for sdLDLC concentration and other valuables.

RESULTS

Serum concentrations of total cholesterol, LDLC, remnant-like particles-cholesterol (RLPC), and apolipoprotein B significantly decreased during OGTT (p<0.05). SdLDLC also decreased and was a minimum at 2 h after glucose ingestion and increased to the baseline by 3 h. The sdLDLC decrease was seen while serum insulin level was high. The change of sdLDLC during OGTT had greater inverse correlationship with that of serum insulin level (r=-0.74, p<0.01) than that of plasma glucose level (r=-0.69, p=0.04). After fat ingestion, triglyceride and RLPC increased remarkably (p<0.01) but sdLDLC, LDLC, apolipoprotein B, and insulin did not change significantly.

CONCLUSIONS

Serum concentration of sdLDLC was not affected by a fat intake but by a glucose intake. The change of sdLDLC was associated by that of serum insulin level, suggesting that insulin can be one of the key modulator of serum sdLDLC level as well as LDL metabolism.

Combined effect of high low-density lipoprotein cholesterol and metabolic syndrome on subclinical coronary atherosclerosis in white men without clinical evidence of myocardial ischemia

High low-density lipoprotein (LDL) cholesterol and the presence of metabolic syndrome (MS) are established risk factors for clinical and subclinical cardiovascular disease (CVD). However, the relative contribution to CVD risk of MS and high LDL cholesterol is not well defined. Therefore, the aim was assess the relative risk for the presence of coronary artery calcification (CAC) with metabolic syndrome (MS) compared with that of moderate or high LDL cholesterol. A total of 440 consecutive asymptomatic men (mean age 46 +/- 7 years, range 29 to 65) presenting for CVD risk stratification were studied. MS was defined using National Cholesterol Education Program Adult Treatment Panel III criteria (n = 112; 24%). Moderate LDL cholesterol was defined as 130 to 159 mg/dl, and high LDL cholesterol as >/=160 mg/dl (n = 76; 17%). Overall, CAC was observed in 190 men (40%). The prevalence of CAC >0 was lowest in MS-negative men with LDL cholesterol <130 (35%) or 130 to 159 mg/dl (34%) and highest in MS-positive men with LDL cholesterol >/=160 mg/dl (80%). MS-positive men with LDL cholesterol of 130 to 159 mg/dl had CAC prevalence similar to that of MS-negative men with LDL cholesterol >/=160 mg/dl (54% vs 57%, respectively). This relation persisted with additional adjustment for age, smoking status, and cholesterol-lowering medication. In logistic regression analyses, the odds ratio for CAC >0 was highest in MS-positive men combined with high LDL cholesterol. In conclusion, these results suggest that the risk of CAC in asymptomatic men with moderate or high LDL cholesterol is magnified in persons with MS.