Apolipoproteins C-III and E in apoB- and non-apoB-containing lipoproteins in two populations at contrasting risk for myocardial infarction: the ECTIM study. Etude Cas Témoins sur 'Infarctus du Myocarde

A novel mouse model of familial combined hyperlipidemia and atherosclerosis

Within the context of residual cardiovascular risk in post-statin era, emerging evidence from epidemiologic and human genetic studies have demonstrated that triglyceride (TG)-rich lipoproteins and their remnants are causally related to cardiovascular risk. While, carriers of loss-of-function mutations of ApoC3 have low TG levels and are protected from cardiovascular disease (CVD). Of translational significance, siRNAs/antisense oligonucleotide (ASO) targeting ApoC3 is beneficial for patients with atherosclerotic CVD. Therefore, animal models of atherosclerosis with both hypercholesterolemia and hypertriglyceridemia are important for the discovery of novel therapeutic strategies targeting TG-lowering on top of traditional cholesterol-lowering. In this study, we constructed a novel mouse model of familial combined hyperlipidemia through inserting a human ApoC3 transgene (hApoC3-Tg) into C57BL/6 J mice and injecting a gain-of-function variant of adeno-associated virus-proprotein convertase subtilisin/kexin type 9 (AAV-PCSK9)-D377Y concurrently with high cholesterol diet (HCD) feeding for 16 weeks. In the last 10 weeks, hApoC3-Tg mice were orally treated with a combination of atorvastatin (10 mg·kg-1·d-1) and fenofibrate (100 mg·kg-1·d-1). HCD-treated hApoC3-Tg mice demonstrated elevated levels of serum TG, total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C). Oral administration of atorvastatin and fenofibrate significantly decreased the plaque sizes of en face aorta, aortic sinus and innominate artery accompanied by improved lipid profile and distribution. In summary, this novel mouse model is of considerable clinical relevance for evaluation of anti-atherosclerotic drugs by targeting both hypercholesterolemia and hypertriglyceridemia.

Hypertriglyceridemia, a causal risk factor for atherosclerosis, and its laboratory assessment

Epidemiological and clinical studies show a causal association between serum triglyceride (TG) level, the number of triglyceride-rich lipoproteins (TRLs) and their remnants, and the increased risk of atherosclerosis and cardiovascular disease (CVD) development. In light of current guidelines for dyslipidemia management, the laboratory parameters reflecting TRL content are recommended as part of the routine lipid analysis process and used for CVD risk assessment, especially in people with hypertriglyceridemia (HTG), diabetes mellitus, obesity and low levels of low-density lipoprotein cholesterol (LDL-C), in which high residual CVD risk is observed. The basic routinely available laboratory parameters related with TRL are serum TG and non-high-density lipoprotein cholesterol (non-HDL-C) levels, but there are also other biomarkers related to TRL metabolism, the determination of which can be helpful in identifying the basis of HTG development or assessing CVD risk or can be the target of pharmacological intervention. In this review, we present the currently available laboratory parameters related to HTG. We summarise their link with TRL metabolism and HTG development, the determination methods as well as their clinical significance, the target values and interpretation of the results in relation to the current dyslipidemia guidelines.

Apolipoprotein CIII Is an Important Piece in the Type-1 Diabetes Jigsaw Puzzle

It is well known that type-2 diabetes mellitus (T2D) is increasing worldwide, but also the autoimmune form, type-1 diabetes (T1D), is affecting more people. The latest estimation from the International Diabetes Federation (IDF) is that 1.1 million children and adolescents below 20 years of age have T1D. At present, we have no primary, secondary or tertiary prevention or treatment available, although many efforts testing different strategies have been made. This review is based on the findings that apolipoprotein CIII (apoCIII) is increased in T1D and that in vitro studies revealed that healthy β-cells exposed to apoCIII became apoptotic, together with the observation that humans with higher levels of the apolipoprotein, due to mutations in the gene, are more susceptible to developing T1D. We have summarized what is known about apoCIII in relation to inflammation and autoimmunity in in vitro and in vivo studies of T1D. The aim is to highlight the need for exploring this field as we still are only seeing the top of the iceberg.

Lipid-Lowering Agents

Several new or emerging drugs for dyslipidemia owe their existence, in part, to human genetic evidence, such as observations in families with rare genetic disorders or in Mendelian randomization studies. Much effort has been directed to agents that reduce LDL (low-density lipoprotein) cholesterol, triglyceride, and Lp[a] (lipoprotein[a]), with some sustained programs on agents to raise HDL (high-density lipoprotein) cholesterol. Lomitapide, mipomersen, AAV8.TBG.hLDLR, inclisiran, bempedoic acid, and gemcabene primarily target LDL cholesterol. Alipogene tiparvovec, pradigastat, and volanesorsen primarily target elevated triglycerides, whereas evinacumab and IONIS-ANGPTL3-L_Rx target both LDL cholesterol and triglyceride. IONIS-APO(a)-L_Rx targets Lp(a).

Effect of milk fat on LDL cholesterol and other cardiovascular risk markers in healthy humans: the INNOVALAIT project

BACKGROUND

Milk has a specific saturated fatty acid profile and its calcium content may change the kinetics of fat absorption.

OBJECTIVE

The goal of this study was to compare the effect on LDL Cholesterol and other risk markers of four isolipidic diets differing by their fat food source, vegetable fat, spring milk fat, winter milk fat or winter milk fat supplemented with calcium, in healthy moderately hypercholesterolemic humans.

INDIVIDUALS AND METHODS

This double-blind, randomized trial with four parallel arms included 172 healthy adults with plasma LDL cholesterol (LDL-C) from 130 to 220 mg/dL and triglycerides below 300 mg/dL. Individual meal plans ensured a stable energy intake. In the three diets containing milk fat, milk fat provided 38% of energy. Vegetable fat and spring milk fat diets provided the same amount of saturated fatty acids while the winter milk fat diets were slightly richer in saturated fatty acids. Vegetable fat diet and winter milk fat diets provided the same amount of palmitic acid (7.0% EI), while the spring milk fat diet was slightly poorer in this fatty acid (5.1% EI). Cardiovascular risk markers were analyzed after 8 weeks of dietary intervention.

RESULTS

There was no significant difference in LDL-C and other markers, except total cholesterol (TC), apo C3 and CRP. TC was significantly higher with spring milk fat than with vegetable fat.

CONCLUSIONS

In this trial, the chosen vegetable fat did not have a significant beneficial effect on LDL-C compared to dairy fat. However, sub-group analysis showed differences in TC, apo C3 and CRP. These results need confirmation and long-term studies aiming at cardiovascular endpoints are warranted.

Tackling Residual Atherosclerotic Risk in Statin-Treated Adults: Focus on Emerging Drugs

Epidemiological studies and meta-analyses have consistently suggested the importance of lowering low-density lipoprotein cholesterol (LDL-C) to reduce cardiovascular (CV) events. However, these studies and mechanistic studies using intracoronary imaging modalities have reported patients who continue to experience CV events or disease progression despite optimal LDL-C levels on statins. These findings, including statin intolerance, have highlighted the importance of exploring additional potential therapeutic targets to reduce CV risk. Genomic insights have presented a number of additional novel targets in lipid metabolism. In particular, proprotein convertase subtilisin/kexin type 9 inhibitors have rapidly developed and recently demonstrated their beneficial impact on CV outcomes. Triglyceride (TG)-rich lipoproteins have been recently reported as a causal factor of atherosclerotic cardiovascular disease (ASCVD). Indeed, several promising TG-targeting therapies are being tested at various clinical stages. In this review, we present the evidence to support targeting atherogenic lipoproteins to target residual ASCVD risk in statin-treated patients.

Effect of omega-3 supplements on plasma apolipoprotein C-III concentrations: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Apolipoprotein C-III (apo C-III) is a key regulator of triglycerides metabolism. The aim of this meta-analysis was to assess the effect of fish omega-3 polyunsaturated fatty acids (PUFAs) on apo C-III levels.

METHODS

Randomized placebo-controlled trials investigating the impact of omega-3 on apo C-III levels were searched in PubMed-Medline, SCOPUS, Web of Science and Google Scholar. A random-effects model and generic inverse variance method were used for quantitative data synthesis. Sensitivity analysis was conducted using the leave-one-out method. A weighted random-effects meta-regression was performed to evaluate the impact of potential confounders on glycemic parameters.

RESULTS

This meta-analysis comprising 2062 subjects showed a significant reduction of apo C-III concentrations following treatment with omega-3 (WMD: -22.18 mg/L, 95% confidence interval: -31.61, -12.75, p < .001; I²: 88.24%). Subgroup analysis showed a significant reduction of plasma apo C-III concentrations by eicosapentaenoic acid (EPA) ethyl esters but not omega-3 carboxylic acids or omega-3 ethyl esters. There was a greater apo C-III reduction with only EPA as compared with supplements containing EPA and docosahexaenoic acid (DHA) or only DHA. A positive association between the apo C-III-lowering effect of omega-3 with baseline apo C-III concentrations and treatment duration was found.

CONCLUSIONS

This meta-analysis has shown that omega-3 PUFAs might significantly decrease apo C-III. Key messages Omega-3 PUFA supplements significantly reduce apo C-III plasma levels, particularly in hypertriglyceridemic patients when applied in appropriate dose (more than 2 g/day) Triglyceride (TG)-lowering effect is achieved via peroxisome proliferator-activated receptors α Further studies should address the effect of omega-3 PUFAs alone or with other lipid-lowering drugs in order to provide a final answer whether apo C-III could be an important target for prevention of cardiovascular disease New apo C-III antisense oligonucleotide drug (Volanesorsen) showed to be promising in decreasing elevated TGs by reducing levels of apo C-III mRNA.

New medications targeting triglyceride-rich lipoproteins: Can inhibition of ANGPTL3 or apoC-III reduce the residual cardiovascular risk?

Remarkably good results have been achieved in the treatment of atherosclerotic cardiovascular diseases (CVD) by using statin, ezetimibe, antihypertensive, antithrombotic, and PCSK9 inhibitor therapies and their proper combinations. However, despite this success, the remaining CVD risk is still high. To target this residual risk and to treat patients who are statin-intolerant or have an exceptionally high CVD risk for instance due to familial hypercholesterolemia (FH), new therapies are intensively sought. One pathway of drug development is targeting the circulating triglyceride-rich lipoproteins (TRL) and their lipolytic remnants, which, according to the current view, confer a major CVD risk. Angiopoietin-like protein 3 (ANGPTL3) and apolipoprotein C-III (apoC-III) are at present the central molecular targets for therapies designed to reduce TRL, and there are new drugs emerging that suppress their expression or inhibit the function of these two key proteins. The medications targeting these components are biological, either human monoclonal antibodies or antisense oligonucleotides. In this article, we briefly review the mechanisms of action of ANGPTL3 and apoC-III, the reasons why they have been considered promising targets of novel therapies for CVD, as well as the current status and the most important results of their clinical trials.

Effect of statin therapy on plasma apolipoprotein CIII concentrations: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Statins are well-established low-density lipoprotein cholesterol-lowering drugs. Elevated apolipoprotein CIII (Apo CIII) levels are associated with elevated triglyceride-rich particles, which are also considered to be a possible risk factor for cardiovascular disease.

OBJECTIVE

The aim of this meta-analysis of randomized placebo-controlled clinical trials was to assess the effect of statins on Apo CIII concentrations.

METHODS

Randomized placebo-controlled trials investigating the impact of statin treatment on cholesterol lowering that include lipoprotein measurement were searched in PubMed, MEDLINE, Scopus, Web of Science, and Google Scholar databases (up to July 31, 2017). A random-effects model and generic inverse variance method were used for quantitative data synthesis. Sensitivity analysis was conducted using the leave-one-out method. A weighted random-effects meta-regression was performed to evaluate the impact of potential confounders on Apo CIII concentrations.

RESULTS

This meta-analysis of data from 6 randomized placebo-controlled clinical trials (10 statin arms) involving 802 subjects showed that statin therapy significantly decreased circulating Apo CIII concentrations (weighted mean difference [WMD]: -2.71, 95% confidence interval [CI]: -3.74 to -1.68, P < .001; I²: 73.83%). The effect size was robust in the leave-one-out sensitivity analysis and not driven by any single study. Subgroup analysis showed a reduction of Apo CIII concentrations by atorvastatin (WMD: -4.74, 95% CI: -3.74 to -1.68, P = .002; I²: 84.02%), rosuvastatin (WMD: -2.68, 95% CI: -4.52 to -0.84, P = .004; I²: 0%), and lovastatin (WMD: -1.64, 95% CI: -2.22 to -1.07, P < .001; I²: 0%).

CONCLUSION

This meta-analysis suggests that statin treatment significantly reduces plasma Apo CIII levels.

Why Is Apolipoprotein CIII Emerging as a Novel Therapeutic Target to Reduce the Burden of Cardiovascular Disease?

ApoC-III was discovered almost 50 years ago, but for many years, it did not attract much attention. However, as epidemiological and Mendelian randomization studies have associated apoC-III with low levels of triglycerides and decreased incidence of cardiovascular disease (CVD), it has emerged as a novel and potentially powerful therapeutic approach to managing dyslipidemia and CVD risk. The atherogenicity of apoC-III has been attributed to both direct lipoprotein lipase-mediated mechanisms and indirect mechanisms, such as promoting secretion of triglyceride-rich lipoproteins (TRLs), provoking proinflammatory responses in vascular cells and impairing LPL-independent hepatic clearance of TRL remnants. Encouraging results from clinical trials using antisense oligonucleotide, which selectively inhibits apoC-III, indicate that modulating apoC-III may be a potent therapeutic approach to managing dyslipidemia and cardiovascular disease risk.

Aggravated restenosis and atherogenesis in ApoCIII transgenic mice but lack of protection in ApoCIII knockouts: the effect of authentic triglyceride-rich lipoproteins with and without ApoCIII

AIM

Previously, our group and others have demonstrated a causative relationship between severe hypertriglyceridaemia and atherogenesis in mice. Furthermore, clinical investigations have shown high levels of plasma Apolipoprotein C-III (ApoCIII) associated with hypertriglyceridaemia and even cardiovascular disease. However, it remains unclear whether ApoCIII affects restenosis in vivo, and whether such an effect is mediated by ApoCIII alone, or in combination with hypertriglyceridaemia. We sought to investigate ApoCIII in restenosis and clarify how smooth muscle cells (SMCs) respond to authentic triglyceride-rich lipoproteins (TRLs) with or without ApoCIII (TRLs ± ApoCIII).

METHODS AND RESULTS

ApoCIII transgenic (ApoCIIItg) and knockout (ApoCIII-/-) mice underwent endothelial denudation to model restenosis. Here, ApoCIIItg mice displayed severe hypertriglyceridaemia and increased neointimal formation compared with wild-type (WT) or ApoCIII-/- mice. Furthermore, increased proliferating cell nuclear antigen (PCNA)-positive cells, Mac-3, and vascular cell adhesion protein-1 (VCAM-1) expression, and 4-hydroxynonenal (4HNE) production were found in lesion sites. ApoCIIItg and ApoCIII-/- mice were then crossed to low-density lipoprotein receptor-deficient (Ldlr-/-) mice and fed an atherogenic diet. ApoCIIItg/Ldlr-/- mice had significantly increased atherosclerotic lesions. However, there was no statistical difference in restenosis between ApoCIII-/- and WT mice, and in atherosclerosis between ApoCIII/Ldlr double knockout and Ldlr-/- mice. SMCs were then incubated in vitro with authentic TRLs ± ApoCIII isolated from extreme hypertriglyceridaemia glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1-deficient (GPIHBP1-/-) mice crossed with ApoCIIItg or ApoCIII-/- mice. It was shown that TRLs + ApoCIII promoted SMC proliferation, VCAM-1 expression, and reactive oxygen species (ROS) production, and activated the Akt pathway. Scavenging ROS significantly reduced SMC activation caused by TRLs + ApoCIII.

CONCLUSIONS

Severe hypertriglyceridaemia resulting from ApoCIII overexpression promotes restenosis and atherosclerosis. Furthermore, we demonstrated that TRLs + ApoCIII promotes SMC proliferation.

The risk of cardiovascular events with increased apolipoprotein CIII: A systematic review and meta-analysis

BACKGROUND

Apolipoprotein CIII (apoC-III) is an atherogenic protein found on HDL, VLDL and LDL.

OBJECTIVE

The objective of this study is to review the literature on the association of blood apoC-III level with cardiovascular events and the dose-response relationship for this association.

METHODS AND RESULTS

MEDLINE, EMBASE, BIOSIS, CINAHL, Clinicaltrials.gov, grey-literature sources, contact with investigators, and reference lists of studies, without language restrictions, were reviewed. Twelve studies (5 retrospective and 7 prospective) with a total of 3163 cases of cardiovascular events met inclusion criteria for this systematic review. The pooled standardized mean difference showed significantly higher levels of apoC-III in the non-HDL fraction of plasma (representing apoC-III in VLDL and LDL) in those with cardiovascular disease compared with controls; no difference for apoC-III levels in HDL; and, a trend toward higher total plasma apoC-III in the cases. Pooled risk estimates from the meta-analysis were 2.48 (1.48-4.32; non-HDL apoC-III), 1.09 (0.65-1.82; HDL apoC-III), and 1.33 (1.07-1.66; total apoC-III) for a cardiovascular event with a 5-mg/dL increase in apoC-III.

CONCLUSIONS

The current body of literature includes several methodologically sound studies that together provide consistent evidence for an association of cardiovascular events with blood apoC-III level in total plasma or in VLDL and LDL. More data are needed to determine importance of levels of apoC-III in specific lipoproteins for cardiovascular risk assessment and management and to elucidate the interaction between triglycerides and apoC-III in relation to risk of cardiovascular disease.

Apolipoprotein C-III: a potent modulator of hypertriglyceridemia and cardiovascular disease

PURPOSE OF REVIEW

The purpose of this article is to summarize the recent epidemiological, basic science, and pharmaceutical research linking apolipoprotein C-III (apoC-III) with the development and treatment of cardiovascular disease (CVD).

RECENT FINDINGS

ApoC-III is an important emerging target linking hypertriglyceridemia with CVD. ApoC-III is a potent modulator of many established CVD risk factors, and is found on chylomicrons, very-low density lipoprotein, low-density lipoprotein, and high-density lipoprotein particles. Recent studies show that in humans, apoC-III levels are an independent risk factor for CVD, and its presence on lipoproteins may promote their atherogenicity. This year, two large-scale epidemiological studies have linked mutations in apoC-III with increased incidence of CVD and hypertriglyceridemia. ApoC-III raises plasma triglycerides through inhibition of lipoprotein lipase, stimulation of very-low density lipoprotein secretion, and is a novel factor in modulating intestinal triglyceride trafficking. ApoC-III also stimulates inflammatory processes in the vasculature and the pancreas. The combination of raising plasma triglycerides and independently stimulating inflammatory processes makes apoC-III a valuable target for reducing the residual CVD risk in patients already on statin therapy, or for whom triglycerides are poorly controlled. Clinical trials on apoC-III antisense oligonucleotides are in progress.

SUMMARY

ApoC-III is a potent direct modulator of established CVD risk factors: plasma triglycerides and inflammation. Recent findings show that changes in apoC-III levels are directly associated with changes in cardiovascular risk and the atherogenicity of the lipoproteins on which apoC-III resides. Emerging roles of apoC-III include a role in directing the atherogenicity of high-density lipoprotein, intestinal dietary triglyceride trafficking, and modulating pancreatic β-cell survival. The combination of these roles makes apoC-III an important therapeutic target for the management and prevention of CVD.

Racial differences between African-American and white women in insulin resistance and visceral adiposity are associated with differences in apoCIII containing apoAI and apoB lipoproteins

Background

African-Americans have higher HDL, less visceral adipose tissue (VAT) and lower triglyceride (TG) and apoCIII concentrations than whites, despite being more insulin-resistant. We studied in African-American and white women the influences of insulin resistance and VAT on the apoAI concentrations of two HDL subspecies, one that contains apoCIII that is associated with increased risk of coronary heart disease (CHD) and one that does not have apoCIII that is associated with decreased CHD; and on the apoCIII concentrations of HDL and of the apoB lipoproteins.

Methods

The participants were 32 women (14 African-Americans, 18 white) of similar age (39 ± 12 vs. 42 ± 11y). Mean BMI was 34 kg/m² in the African-Americans compared to 30 in the whites. A standard diet (33% fat, 52% carbohydrate, 15% protein) was provided for 7 days followed by a test meal (40% fat, 40% carbohydrate, 20% protein) on Day 8. Insulin sensitivity index (S_I) was calculated from the minimal model.

Results

After controlling for S_I, African-Americans have a higher mean apoAI level in HDL with apoCIII compared with whites (12.9 ± 2.8 and 10.9 ± 2.9 mg/dL, respectively, P = 0.05). S_I was associated with higher apoAI in HDL with apoCIII, whereas VAT was not associated with this HDL subspecies. This pattern of results was reversed for apoCIII concentrations in apoB lipoproteins. After adjusting for S_I, African-Americans had lower apoCIII in apoB lipoproteins. S_I was associated with lower apoCIII in total apoB lipoproteins, whereas VAT was associated with higher apoCIII in all the apoB lipoproteins. Additional adjustment for VAT tended to reduce the difference in apoCIII between the groups.

Conclusions

African-American women have a higher HDL with apoCIII level than whites when controlled for insulin sensitivity. African-Americans have lower insulin sensitivity. Insulin sensitivity is associated with higher levels of HDL with apoCIII. ApoCIII levels in VLDL are lower in African-American women than whites, also affected by insulin sensitivity which is associated with low apoCIII in VLDL. VAT has a strong association with apoCIII in apoB lipoproteins but not with apoAI in HDL with apoCIII.

Trial registration

ClinicalTrials.gov Identifier: NCT00484861

Updates on apolipoprotein CIII: fulfilling promise as a therapeutic target for hypertriglyceridemia and cardiovascular disease

PURPOSE OF REVIEW

The lipid hypothesis of atherosclerosis is mainly predicated on the function of apolipoprotein (apo)B lipoproteins, which promote atherosclerosis, and apoA lipoproteins, which prevent it. However, accumulating evidence suggests causal roles of other apolipoproteins, abundant surface components of apoB and apoA lipoprotein, in promoting atherosclerosis and other metabolic diseases. This article reviews recent literature on one such apolipoprotein: apoCIII.

RECENT FINDINGS

Population studies have consistently demonstrated that plasma apoCIII strongly predicts cardiovascular disease. ApoCIII's atherogenicity was traditionally attributed to hypertriglyceridemia because of its inhibition on the lipolysis of triglyceride-rich lipoproteins. Recent evidence expands this function and reveals apoCIII's key role in hepatic assembly and secretion of triglyceride-rich lipoproteins. In addition to these indirect atherogenic functions mediated through dyslipidemia, recent research discovers that apoCIII directly provoke proinflammatory responses in vascular cells, including monocytes and endothelial cells. These direct atherogenic effects are dependent on apoCIII. ApoCIII is also involved in pancreatic beta-cell biology and contributes to type I diabetes.

SUMMARY

Recent data further strengthen the theory that apoCIII exerts strong atherogenic functions through both indirect and direct mechanisms. Encouraging results from early stage clinical trials demonstrate that modulating apoCIII per se is a novel and potent therapeutic approach to managing dyslipidemia and cardiovascular disease risk.

Factor II activity is similarly increased in patients with elevated apolipoprotein CIII and in carriers of the factor II 20210A allele

Background

Few studies have so far investigated the relationship between apolipoprotein CIII (Apo CIII) and coagulation pathway in subjects with or without coronary artery disease (CAD).

Methods and Results

Serum Apo CIII concentrations and plasma coagulant activities of factor II (FII:c), factor V (FV:c), and factor VIII (FVIII:c), and activated factor VII (FVIIa) were analyzed in a total of 933 subjects, with (n=687) or without (n=246) angiographically demonstrated CAD and not taking anticoagulant drugs. Activated factor X (FXa) generation assay was performed on plasma from subgroups of subjects with low and high levels of Apo CIII. A statistical incremental concentration of FII:c, FV:c, and FVIIa levels was observed through the quartiles of Apo CIII distribution in the population considered as a whole. Significant results were confirmed for FII:c in CAD and CAD‐free subgroup when separately considered. Subjects within the highest Apo CIII quartile (>12.6 mg/dL) had high FII:c levels not statistically different from those of carriers of 20210A allele (n=40; 4.28%). In a multiple linear model, Apo CIII was the best predictor of FII:c variability, after adjustment for age, gender, plasma lipids, CRP, creatinine, diagnosis, and carriership of 20210A allele. FXa generation was increased and its lag time shortened in plasmas with high Apo CIII levels. However, after thrombin inhibition by hirudin, differences between low and high Apo C‐III samples disappeared.

Conclusions

Elevated concentrations of Apo CIII are associated with an increase of thrombin activity to an extent comparable with the carriership of G20210A gene variant and mainly modulating the thrombin generation.

Apolipoprotein-defined and NMR lipoprotein subclasses in the veterans affairs diabetes trial

AIMS

The VADT was a randomized clinical trial designed to assess the effect of intensive vs. standard glucose management on cardiovascular events in Type 2 diabetes. At the end of the study, intensive management failed to improve outcomes. We performed plasma lipoprotein subclass analyses to yield new information on the effects of study randomization on cardiovascular risk.

METHODS

This is a cross-sectional study of a subset of the VADT (740 men: 368 intensive; 372 standard), conducted at least six months (mean±SD: 2.1±0.8years) post-randomization. Conventional lipids, apolipoprotein-defined (ADLS) lipoprotein subclasses, ApoCIII, ApoE, and Nuclear Magnetic Resonance (NMR) lipoprotein subclasses were determined.

RESULTS

In intensive vs. standard groups, conventional lipids and ADLS did not differ significantly. However, with intensive treatment, NMR-determined large and medium VLDL subclasses and VLDL diameter were lower, LDL diameter was higher, medium HDL was higher, and small HDL was lower (all p<0.05). Also, ApoCIII levels were lower (p<0.01).

CONCLUSIONS

In a subset of diabetic men from the VADT, intensive glucose management did not affect conventional lipids or ADLS, but had some beneficial effects on particle characteristics as defined by NMR and on ApoCIII.

Impact of multiple cardiovascular risk factors on carotid intima-media thickness and elasticity

Background

Carotid intima-media thickness (IMT) and elasticity have been shown to be independent predictors of cardiovascular disease (CVD). Cardiovascular risk factors (CVRFs) includes hypertension, dyslipidemia, diabetes, overweight and smoking. The objective was to investigate whether the clustering of three or more components of CVRFs has a greater impact on carotid IMT and elasticity than individual components of CVRFs.

Methods

One hundred and seventy-three participants without clinical CVD were classified as the multiple CVRFs patients with three or more CVRFs (n  = 55) and control group with two or less CVRFs (n  = 118). Carotid IMT and elastic modulus were measured by B-mode ultrasound and vessel texture matching method (VTMM), respectively.

Results

The multiple CVRFs conferred a disproportionate increase in carotid IMT (43%, p<0.0001) and elastic modulus (60%, p<0.0001), compared with control group. Multiple regression models, which included age, gender, as well as each individual component of CVRFs as continuous variables, showed that multiple CVRFs was an independent determinant of both IMT (p  = 0.042) and elasticity (p  = 0.008). In the analysis of variance adjusted with age, subjects with single, double, and multiple CVRFs, increased by 8.1%, 42.2%, and 66% for IMT, 54.6%, 94.3%, and 125.2% for elastic modulus, respectively, compared to subjects without CVRFs.

Conclusions

The clustering of multiple CVRFs has a greater impact on carotid IMT and elasticity than individual components of CVRFs. This suggests that the components of CVRFs interact to synergistically impact carotid IMT and elasticity.

Two novel mutations in apolipoprotein C3 underlie atheroprotective lipid profiles in families

Apolipoprotein C3 (APOC3) mutations carriers typically display high plasma high-density lipoprotein cholesterol (HDL-C) and low triglycerides (TGs). We set out to investigate the prevalence and clinical consequences of APOC3 mutations in individuals with hyperalphalipoproteinemia. Two novel mutations (c.-13-2A>G and c.55+1G>A) and one known mutation (c.127G>A;p.Ala43Thr) were found. Lipid profiles and apoCIII isoform distributions were measured. c.55+1G>A mutation carriers displayed higher HDL-C percentiles (35.6 ± 35.8 vs 99.0 ± 0, p = 0.002) and lower TGs (0.51 (0.37-0.61) vs 1.42 (1.12-1.81) mmol/l, p = 0.007) and apoCIII levels (4.24 ± 1.57 vs 7.33 ± 3.61 mg/dl, p = 0.18). c.-13-2A>G mutation carriers did not display significantly different HDL-C levels (84.0 ± 30.0 vs 63.7 ± 45.7, p = 0.50), a trend towards lower TGs [0.71 (0.54 to 0.78) vs 0.85 (0.85 to -) mmol/l, p = 0.06] and significantly lower apoCIII levels (3.09 ± 1.08 vs 11.45 ± 1.06 mg/dl, p = 0.003). p.Ala43Thr mutation carriers displayed a trend towards higher HDL-C percentiles (91.2 ± 31.8 vs 41.0 ± 29.7 mmol/l, p = 0.06) and significantly lower TGs [0.58 (0.36-0.63) vs 0.95 (0.71-1.20) mmol/l, p = 0.02] and apoCIII levels (4.92 ± 2.33 vs 6.60 ± 1.60, p = 0.25). Heterozygosity for APOC3 mutations results in high HDL-C and low TGs and apoCIII levels. This favourable lipid profile in patients with genetically low apoCIII levels holds promise for current studies investigating the potential of apoCIII inhibition as a novel therapeutic in cardiovascular disease prevention.

Apolipoprotein E in VLDL and LDL with apolipoprotein C-III is associated with a lower risk of coronary heart disease

BACKGROUND

Low-density lipoprotein (LDL) with apolipoprotein C-III (apoC-III) is the lipoprotein species that most strongly predicts initial and recurring coronary heart disease (CHD) events in several cohorts. Thus, a large portion of the CHD risk conferred by LDL may be attributable to LDL that contains apoC-III. Very-low-density lipoprotein (VLDL) and LDL with apoC-III have varying amounts of apoE. We hypothesized that a high content of apoE lessens the adverse influence of apoC-III on the risk of CHD because it promotes the clearance of VLDL and LDL from plasma.

METHODS AND RESULTS

We studied 2 independent cohorts, the Nurses' Health Study, composed of women, and the Health Professionals Follow-up Study, composed of men. These cohorts contributed to this study 322 women and 418 men initially free of CVD who developed a fatal or nonfatal myocardial infarction during 10 to 14 years of follow-up and matched controls who remained free of CHD. The apoE content of LDL with apoC-III was inversely associated with CHD after multivariable adjustment (relative risk for top versus bottom quintile 0.53, 95% CI 0.35 to 0.80). The apoE content of VLDL with apoC-III had a similar inverse association with CHD. The highest risks were associated with a high apoB concentration and a low apoE content of LDL with apoC-III or of VLDL+LDL with apoC-III. The observed associations were in both male and female cohorts and independent of traditional CHD risk factors and of C-reactive protein.

CONCLUSIONS

An increased apoE content in VLDL and LDL with apoC-III was associated with a lower risk of CHD. Strategies to enrich VLDL and LDL in apoE are worth exploring for the prevention of CHD.

Levels of cholesterol in small LDL particles predict atherosclerosis progression and incident CHD in the HDL-Atherosclerosis Treatment Study (HATS)

Objective

Test whether angiographically-documented changes in percent stenosis and clinical endpoints (coronary-related deaths, myocardial infarctions, stroke, revascularization for worsening ischemia) in the HDL-Atherosclerosis Treatment Study (HATS) were attributable to specific LDL-subclasses.

Methods

Gradient gel electrophoresis of on-study LDL-subclass cholesterol concentrations were measured in 32 placebo, 33 simvastatin-niacin, 38 antioxidant, and 39 simvastatin-niacin & antioxidant treated participants. The prespecified primary end point was the mean change per patient from the initial arteriogram to the final arteriogram in the percent stenosis caused by the most severe lesion in each of the nine proximal coronary segments.

Results

The change in the percent stenosis of the most severe proximal lesions increased in association with higher concentrations of the small LDL subfractions LDL-IIIb (24.2–24.6 nm) and LDL-IVa (23.3–24.1 nm) before (both P = 0.002) and after (P = 0.01 and P = 0.03 respectively) adjustment for treatment group and on-study HDL-cholesterol, LDL-cholesterol, and triglyceride concentrations. The associations appeared specific to lesions with <30% baseline stenosis. When adjusted for age, sex, baseline BMI and cigarette use, the odds for primary clinical endpoints (death from coronary causes, nonfatal myocardial infarction, stroke, or revascularization for worsening ischemia) were significantly greater in subjects with higher on-study LDL-IIIb levels both before (P = 0.01) and after (P = 0.03) adjustment for treatment group and the standard lipid values.

Conclusions

Plasma LDL-IIIb cholesterol concentrations were related to changes in coronary artery stenosis and cardiovascular events in patients with coronary artery disease and low HDL-cholesterol.

Trial Registration

ClinicalTrials.gov NCT00000553

Identification of the HDL-ApoCIII to VLDL-ApoCIII ratio as a predictor of coronary artery disease in the general population: the Chin-Shan Community Cardiovascular Cohort (CCCC) study in Taiwan

Background

Apolipoprotein (Apo) levels are considered more reliable than plasma lipoprotein levels for predicting coronary artery disease (CAD). However, a unanimous Apo marker for CAD has not been identified. In the Chin-Shan Community Cardiovascular Cohort (CCCC), we sought to identify a common Apo marker for predicting CAD in the general population.

Methods

We examined the cross-sectional association between Apo markers and CAD in the CCCC from 1990 to 2001. Among 3,602 subjects, 90 had angiographically proven CAD (>50% stenosis in ≥1 vessel), and 200 did not have CAD. These subjects were divided into the following 4 groups for analysis: normolipidemic (total cholesterol [TC] <200 mg/dL, triglyceride [TG] <150 mg/dL), hypertriglyceridemic (TC <200 mg/dL, TG ≥150 mg/dL), hypercholesterolemic (TC ≥200 mg/dL, TG <150 mg/dL), and hyperlipidemic (TC ≥200 mg/dL, TG ≥150 mg/dL).

Results

Compatible with findings in other populations, our results showed that CAD patients in the CCCC had higher ApoB and lower high-density lipoprotein (HDL) cholesterol and ApoAI concentrations than non-CAD subjects, but the differences were not significant in all groups. Plasma concentrations of ApoE and lipoprotein (a) were not consistently correlated with CAD. In contrast, the ratio of HDL-ApoCIII to very-low-density lipoprotein (VLDL)-ApoCIII was the only universal determinant for CAD in the normolipidemic group (P=0.0018), the hypertriglyceridemic group (P=0.0001), the hypercholesterolemic group (P=0.0001), and the hyperlipidemic group (P=0.0001). Overall, a high HDL-ApoCIII/VLDL-ApoCIII ratio was observed in all CAD patients, including those with a normal lipid profile. In multivariate analyses, the HDL-ApoCIII/VLDL-ApoCIII ratio was the strongest predictor for CAD among all lipid factors investigated (odds ratio, 2.04; 95% confidence interval, 1.46–2.84; P<0.0001).

Conclusions

A high HDL-ApoCIII to VLDL-ApoCIII ratio is a better marker for predicting CAD than are the conventional lipid markers or ApoAI and ApoB. High HDL-ApoCIII and low VLDL-ApoCIII values in CAD, irrespective of lipid variations, suggest that ApoCIII is markedly transported from VLDL to HDL in this disease. Measurement of plasma ApoCIII may improve CAD prediction in the general population.

Apolipoproteins: metabolic role and clinical biochemistry applications

Lipoprotein metabolism is dependent on apolipoproteins, multifunctional proteins that serve as templates for the assembly of lipoprotein particles, maintain their structure and direct their metabolism through binding to membrane receptors and regulation of enzyme activity. The three principal functions of lipoproteins are contribution to interorgan fuel (triglyceride) distribution (by means of the fuel transport pathway), to the maintenance of the extracellular cholesterol pool (by means of the overflow pathway) and reverse cholesterol transport. The most important clinical application of apolipoprotein measurements in the plasma is in the assessment of cardiovascular risk. Concentrations of apolipoprotein B and apolipoprotein AI (and their ratio) seem to be better markers of cardiovascular risk than conventional markers such as total cholesterol and LDL-cholesterol. Apolipoprotein measurements are also better standardized than the conventional tests. We suggest that measurements of apolipoprotein AI and apolipoprotein B are included as a part of the specialist lipid profile. We also suggest that lipoprotein (a) should be measured as part of the initial assessment of dyslipidaemias because of its consistent association with cardiovascular risk. Genotyping of apolipoprotein E isoforms remains useful in the investigation of mixed dyslipidaemias. Lastly, the role of postprandial metabolism is increasingly recognized in the context of atherogenesis, obesity and diabetes. This requires better markers of chylomicrons, very-low-density lipoproteins and remnant particles. Measurements of apolipoprotein B48 and remnant lipoprotein cholesterol are currently the key tests in this emerging field.

Low-density lipoproteins containing apolipoprotein C-III and the risk of coronary heart disease

BACKGROUND

Low-density lipoprotein (LDL) that contains apolipoprotein (apo) C-III makes up only 10% to 20% of plasma LDL but has a markedly altered metabolism and proatherogenic effects on vascular cells.

METHODS AND RESULTS

We examined the association between plasma LDL with apoC-III and coronary heart disease in 320 women and 419 men initially free of cardiovascular disease who developed a fatal or nonfatal myocardial infarction during 10 to 14 years of follow-up and matched controls who remained free of coronary heart disease. Concentrations of LDL with apoC-III (measured as apoB in this fraction) were associated with risk of coronary heart disease in multivariable analysis that included the ratio of total cholesterol to high-density lipoprotein cholesterol, LDL cholesterol, apoB, triglycerides, or high-density lipoprotein cholesterol and other risk factors. In all models, the relative risks for the top versus bottom quintile of LDL with apoC-III were greater than those for LDL without apoC-III. When included in the same multivariable-adjusted model, the risk associated with LDL with apoC-III (relative risk for top versus bottom quintile, 2.38; 95% confidence interval, 1.54-3.68; P for trend <0.001) was significantly greater than that associated with LDL without apoC-III (relative risk for top versus bottom quintile, 1.25; 95% confidence interval, 0.76-2.05; P for trend=0.97; P for interaction <0.001). This divergence in association with coronary heart disease persisted even after adjustment for plasma triglycerides.

CONCLUSIONS

The risk of coronary heart disease contributed by LDL appeared to result to a large extent from LDL that contains apoC-III.

Dietary interventions that lower lipoproteins containing apolipoprotein C-III are more effective in whites than in blacks: results of the OmniHeart trial

BACKGROUND

Blacks have lower average triglyceride and LDL cholesterol concentrations than do whites but higher rates of coronary heart disease. Apolipoprotein (apo) C-III in VLDL and LDL stimulates atherogenic processes in vascular cells. In blacks, the concentration of lipoproteins with apo C-III is unknown, and the response to dietary strategies that lower triglyceride and apo C-III has not been investigated

OBJECTIVE

We compared the concentration of and dietary effects on apo C-III-containing lipoproteins in blacks and whites.

DESIGN

In a randomized, 3-period feeding study [OmniHeart (Optimal Macronutrient Intake Trial to Prevent Heart Disease)], we measured lipoprotein concentrations in 89 blacks and 73 whites who consumed self-selected diets (baseline) and after 3 healthful diets emphasizing carbohydrate, unsaturated fat, or protein. Participants had prehypertension or hypertension, and 79% were overweight or obese.

RESULTS

While consuming self-selected diets, blacks had lower apo C-III in total plasma, VLDL, and LDL than did whites. Unsaturated fat and protein diets lowered plasma apo C-III (16% and 18%, respectively) and triglyceride (12% and 21%, respectively) in whites but not in blacks, reducing racial differences. Most important, blacks had a lower concentration of atherogenic LDL with apo C-III at baseline and after study diets (34-41% lower, P < 0.02). The molar ratio of apo E to apo B was higher in blacks than in whites in total plasma and LDL at baseline and after the study diets.

CONCLUSIONS

Blacks have lower concentrations of atherogenic lipoproteins that contain apo C-III than do whites when consuming diverse diets and an attenuated dietary response of triglyceride and apo C-III. Dietary efforts to lower triglyceride and apo C-III may be more effective in whites than in blacks. The OmniHeart Trial was registered at www.clinicaltrials.gov as NCT00051350.

The effects of ezetimibe and/or orlistat on triglyceride-rich lipoprotein metabolism in obese hypercholesterolemic patients

We investigated the factors influencing triglycerides (TG) reduction during ezetimibe, alone or combined with orlistat, administration. Eighty-six obese hypercholesterolemic subjects were prescribed a low-fat diet and were randomized to ezetimibe (E group), orlistat (O group), or both (OE group) for 6 months. Plasma TG and apolipoprotein (apo) C-III reduction was significantly greater in the combination group compared with monotherapy. Multivariate analysis showed that in E group apoC-III reduction and baseline TG levels were independently positively correlated, whereas baseline apoC-II levels were negatively correlated, with TG lowering. In OE group apoC-III reduction was the only independent contributor to TG reduction.

Apolipoprotein C-III predicts cardiovascular mortality in severe coronary artery disease and is associated with an enhanced plasma thrombin generation

BACKGROUND

Apolipopoprotein C-III (apo C-III) plays a pivotal role in controlling plasma triglyceride (TG) and contributes to the atherogenic properties of TG-rich lipoproteins.

OBJECTIVES

(i) To examine the predictive value of serum apo C-III for cardiovascular mortality in the setting of secondary prevention of coronary artery disease (CAD); and (ii) to evaluate possible associations between apolipoprotein levels and the thrombin generation assay, a global test to estimate plasma thrombogenic potential.

METHODS AND RESULTS

A cohort of 633 patients with angiographically proven CAD was prospectively followed for a median follow-up of 57 months. The large majority of them (92%) underwent coronary (endovascular or surgical) revascularization. During the follow-up, 91 (14.3%) out of 633 patients died, with 64 events (10.1%) attributed to cardiovascular causes. After adjustment for all the other predictors of mortality during univariate analysis (i.e. age, statin therapy, myocardial infarction history, diabetes, hs-CRP and creatinine), elevated apo C-III levels (> or = 10.5 mg dL(-1)- the median value) significantly predicted both total and cardiovascular mortality (HR for total mortality 2.22 with 95% CI 1.16-4.24; HR for cardiovascular mortality 2.35 with 95% CI 1.19-4.62). In a subgroup of 225 subjects, apo C-III levels were significantly associated with endogenous thrombin potential in regression models (standardized beta coefficient = 0.207, P = 0.002).

CONCLUSIONS

Basal concentrations of apo C-III levels > or = 10.5 mg dL(-1) in CAD patients independently predicted cardiovascular mortality during the subsequent 5-year period. Such concentrations were associated with an enhanced plasma endogenous thrombin generation, suggesting a complex interplay between TG-rich particles and the coagulation cascade as well as a new 'thrombogenetic' role for apo C-III.

Serum apolipoprotein C-III in high-density lipoprotein: a key diabetogenic risk factor in Turks

AIMS

We studied determinants of serum apolipoprotein C-III (apoC-III) and whether levels of apoC-III or its fractions predict metabolic syndrome (MetS), Type 2 diabetes and coronary heart disease (CHD).

METHODS

The predictive value of apoC-III, measured by immunoturbimetric immunoassay in 802 tracked individuals of a Turkish general population in determining cardiometabolic risk was assessed over 4.4 +/- 1.2 years' follow-up. Patients with MetS, Type 2 diabetes and CHD at baseline were excluded.

RESULTS

Total apoC-III, as well as both fractions, was significantly, linearly and inversely related to smoking status, positively to alcohol usage and to levels of complement C3. Mid and high tertiles of total or non-high density lipoprotein (HDL) apoC-III predicted significantly and independently incident MetS; they predicted CHD with risk ratios of 1.6 [95% confidence intervals (CI) 1.02-2.5], for 1 sd increment, after adjustments that included HDL cholesterol and body mass index (BMI). The highest tertile of HDL apoC-III was a major independent predictor of new-onset diabetes with a 2.5-fold risk ratio for 1 sd increment (95% CI 1.5-4.0) in combined sexes, after adjustment for waist circumference, HDL cholesterol and other confounders and was a better predictor than waist girth.

CONCLUSIONS

Serum total apoC-III or its fractions are linearly and inversely associated with smoking, positively with alcohol usage and serum complement C3. The presumably dysfunctional HDL apoC-III is a stronger predictor of Type 2 diabetes than waist girth in Turks. Non-HDL apoC-III predicts strongly the development of MetS as well as incident CHD, independent of HDL cholesterol, BMI and non-lipid factors. The atherogenicity of apoC-III and dysfunctionality of HDL apoC-III carry huge public health implications in Turks.

Parallel increase of plasma apoproteins C-II and C-III in Type 2 diabetic patients

AIMS

To determine plasma levels of apoprotein (apo) C-II and apoprotein C-III in Type 2 diabetic patients and to examine the clinical and biological factors that are associated with elevated apoC concentrations.

METHODS

We measured apoC-II and apoC-III in total plasma and in non-high-density lipoprotein fractions by an immunoturbidimetric assay in 88 Caucasian Type 2 diabetic patients and in 138 healthy control subjects.

RESULTS

Plasma levels of both apoC-II and apoC-III were increased in Type 2 diabetic patients. The clinical conditions associated with an increase of plasma apoC-II and apoC-III were abdominal obesity, body mass index, poor glycaemic control and lack of insulin treatment. However, when multivariate analysis was used, plasma apoCs levels correlated with triglyceride levels only. The apoC-III/apoC-II ratio was similar in the Type 2 diabetic and control subjects.

CONCLUSIONS

Our study shows the parallel increase of apoC-II and C-III in Type 2 diabetic patients. This parallel increase is related to hypertriglyceridaemia only.

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.

Analysis of 6-month effect of orlistat administration, alone or in combination with fenofibrate, on triglyceride-rich lipoprotein metabolism in overweight and obese patients with metabolic syndrome

BACKGROUND

Orlistat significantly reduced serum triglycerides (TG) in most clinical trials. Orlistat-induced TG reduction has not been studied to determine the factors contributing to TG alterations in clinical settings.

OBJECTIVE

We examined the factors influencing TG reduction during orlistat administration, alone or in combination with fenofibrate, and we investigated the effects of these treatments on apolipoprotein C-II (ApoC-II) and C-III (ApoC-III) levels.

METHODS

Patients with the metabolic syndrome were randomly allocated to receive orlistat 120 mg three times daily (n = 28, O group), micronized fenofibrate 200 mg/day (n = 28, F group), or both (n = 27, OF group) for 6 months. Plasma ApoC-II and ApoC-III were determined by an immunoturbidimetric assay.

RESULTS

In the O group, we observed reductions of plasma ApoC-III (P < 0.05) and ApoC-II (P = NS) levels. Fenofibrate administration significantly reduced concentrations of ApoC-II and ApoC-III, whereas the combination of orlistat and fenofibrate had an additive effect on these apolipoproteins. There were significant in-group reductions in serum TG levels in all treatment groups. Multivariate analysis showed that in O group's baseline TG levels were independently positively correlated, whereas the baseline ApoC-II levels were negatively correlated with TG-lowering. In the F group, baseline TG levels and ApoC-III reduction were significantly and independently correlated with TG reduction. OF group's baseline TG levels and ApoC-III reduction were independently positively correlated and baseline ApoC-II levels were negatively correlated with TG-lowering.

CONCLUSIONS

Orlistat-mediated TG-lowering is independently associated with baseline TG and ApoC-II levels. When orlistat is combined with fenofibrate, ApoC-III reduction is another independent contributor to TG alterations.

Apolipoprotein C-III: understanding an emerging cardiovascular risk factor

The concurrence of visceral obesity, insulin resistance and dyslipidaemia comprises the concept of the metabolic syndrome. The metabolic syndrome is an escalating problem in developed and developing societies that tracks with the obesity epidemic. Dyslipidaemia in the metabolic syndrome is potently atherogenic and, hence, is a major risk factor for CVD (cardiovascular disease) in these subjects. It is globally characterized by hypertriglyceridaemia, near normal LDL (low-density lipoprotein)-cholesterol and low plasma HDL (high-density lipoprotein)-cholesterol. ApoC-III (apolipoprotein C-III), an important regulator of lipoprotein metabolism, is strongly associated with hypertriglyceridaemia and the progression of CVD. ApoC-III impairs the lipolysis of TRLs [triacylglycerol (triglyceride)-rich lipoproteins] by inhibiting lipoprotein lipase and the hepatic uptake of TRLs by remnant receptors. In the circulation, apoC-III is associated with TRLs and HDL, and freely exchanges among these lipoprotein particle systems. However, to fully understand the complex physiology and pathophysiology requires the application of tracer methodology and mathematical modelling. In addition, experimental evidence shows that apoC-III may also have a direct role in atherosclerosis. In the metabolic syndrome, increased apoC-III concentration, resulting from hepatic overproduction of VLDL (very-LDL) apoC-III, is strongly associated with delayed catabolism of triacylglycerols and TRLs. Several therapies pertinent to the metabolic syndrome, such as PPAR (peroxisome-proliferator-activated receptor) agonists and statins, can regulate apoC-III transport in the metabolic syndrome. Regulating apoC-III metabolism may be an important new therapeutic approach to managing dyslipidaemia and CVD risk in the metabolic syndrome.

The effects of adrenocorticotrophic hormone and an equivalent dose of cortisol on the serum concentrations of lipids, lipoproteins, and apolipoproteins

Previous studies have shown a strong lipid-lowering effect of adrenocorticotrophic hormone (ACTH) in healthy individuals and in patients with different kinds of dyslipoproteinemia. The mechanism behind this effect has not been established and its direct ACTH-specific nature has been questioned. Therefore, the present study was performed. Thirty healthy young males were randomized into 3 groups of equal size: one group received ACTH1-24 1 mg IM, daily for 4 days, another group was treated with cortisol 150 mg ID (50 mg tid) daily for 4 days, whereas a control group was observed for 4 days. Fasting blood samples were collected before and after treatment or observation. The serum concentrations of cholesterol (12%, P < .05), low-density lipoprotein cholesterol (24%, P < .01), and apolipoprotein (apo) B (31%, P < .01) decreased significantly in the ACTH group but not in the cortisol and control groups. The statistical workup confirmed that only ACTH had a lowering effect on the apo B-containing lipoproteins. In contrast, the results indicated conformity between the treatment groups with respect to increases in the serum apo E concentrations. There were inconsistent changes in the serum concentrations of the triglycerides, high-density lipoprotein cholesterol, apo A, and lipoprotein(a). The main results were clear: the lowering effect of ACTH on the serum concentration of apo B-containing lipoproteins could not be ascribed to cortisol. These, in combination with previous in vitro results, indicated an ACTH-specific effect.

Antiretroviral Therapy in HIV-Positive Women Is Associated With Increased Apolipoproteins and Total Cholesterol

OBJECTIVES

Dyslipidemia has become a common problem in HIV disease, especially in patients on combination antiretroviral (ARV) therapy. However, little data are available to evaluate lipid abnormalities in women on ARV therapy.

METHODS

Using a cross-sectional design, the prevalence of abnormal plasma lipid and lipoprotein concentrations as well as other biomarkers for vascular disease was determined in 184 HIV-positive women from 2 HIV clinics in Atlanta during 2002.

RESULTS

Most of the women were African American (89%), with median age of 41 years (range 21-72); 6% were diabetic, 44% smoked, and 67% were overweight. ARV therapy defined the comparison groups that included treatment with a protease inhibitor (PI)-based regimen for more than 3 months in 76 (41%), treatment with a nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimen for more than 3 months in 38 (20%), and no ARV therapy for the past 3 months in 70 (38%). Women being treated with a PI or NNRTI had higher total cholesterol and triglyceride levels than patients on no therapy (P < 0.05 for each). Women treated with either PIs or NNRTIs had significantly higher apolipoprotein B and apolipoprotein C-III levels than patients on no therapy (P < 0.01 for each).

CONCLUSIONS

In this cross-sectional study of HIV-infected women, either PI or NNRTI therapy elevated levels of total cholesterol and specific apolipoproteins. These findings, on a background of an older population with additional risk factors of smoking, obesity, and diabetes, may lead to future atherosclerotic events in these patients.

Dietary intake of n-6 fatty acids modulates effect of apolipoprotein A5 gene on plasma fasting triglycerides, remnant lipoprotein concentrations, and lipoprotein particle size: the Framingham Heart Study

BACKGROUND

Apolipoprotein A5 gene (APOA5) variation is associated with plasma triglycerides (TGs). However, little is known about whether dietary fat modulates this association.

METHODS AND RESULTS

We investigated the interaction between APOA5 gene variation and dietary fat in determining plasma fasting TGs, remnant-like particle (RLP) concentrations, and lipoprotein particle size in 1001 men and 1147 women who were Framingham Heart Study participants. Polymorphisms -1131T>C and 56C>G, representing 2 independent haplotypes, were analyzed. Significant gene-diet interactions between the -1131T>C polymorphism and polyunsaturated fatty acid (PUFA) intake were found (P<0.001) in determining fasting TGs, RLP concentrations, and particle size, but these interactions were not found for the 56C>G polymorphism. The -1131C allele was associated with higher fasting TGs and RLP concentrations (P<0.01) in only the subjects consuming a high-PUFA diet (>6% of total energy). No heterogeneity by sex was found. These interactions showed a dose-response effect when PUFA intake was considered as a continuous variable (P<0.01). Similar interactions were found for the sizes of VLDL and LDL particles. Only in carriers of the -1131C allele did the size of these particles increase (VLDL) or decrease (LDL) as PUFA intake increased (P<0.01). We further analyzed the effects of n-6 and n-3 fatty acids and found that the PUFA-APOA5 interactions were specific for dietary n-6 fatty acids.

CONCLUSIONS

Higher n-6 (but not n-3) PUFA intake increased fasting TGs, RLP concentrations, and VLDL size and decreased LDL size in APOA5 -1131C carriers, suggesting that n-6 PUFA-rich diets are related to a more atherogenic lipid profile in these subjects.

Association of Apolipoproteins C3 and E with Metabolic Changes in HIV-Infected Adults Treated with a Protease-Inhibitor-Containing Antiretroviral Therapy

Objective

To examine the relationship between plasma levels of apolipoproteins C3 (APOC3) and E (APOE) and the presence of lipid and carbohydrate metabolism abnormalities or clinical signs of lipodystrophy in HIV-1-infected patients started with a protease-inhibitor-containing antiretroviral therapy.

Methods

The Aproco (Antiproteases Cohort) Study enrolled 1,181 HIV-1-infected adults in 47 French healthcare centres from May 1997 to June 1998. From December 1998 through July 1999, the APROCO-Metabolic Complications (APROCO-MC) cross-sectional study was performed at the month 20 visit for those patients enrolled in 1997 and at the month 12 visit for those enrolled in 1998. The current analysis presents results from a subset of patients who had undergone additional tests to measure APOC3 and APOE in order to study their relationship with metabolic syndrome ( n=157) and abnormal results in an oral glucose tolerance test ( n=135).

Results

Increases in triglycerides and non-high-density lipoprotein (HDL) cholesterol were associated with significantly higher levels of APOC3, in both Lp B (lipoproteins containing apolipoprotein B) and Lp non-B (lipoproteins free of apolipoprotein B), and a significant higher level of APOE Lp B. APOC3 and APOC3 Lp non-B were increased when glucose metabolism abnormalities were more severe. The presence of a metabolic syndrome was associated with increased plasma APOC3, APOC3 Lp B and APOC3 Lp non-B levels. In a multiple regression analysis, high levels of APOC3 in Lp B and APOC3 Lp non-B were associated with the presence of clinical signs of lipodystrophy, even after adjustment for triglycerides and HDL-cholesterol levels.

Conclusions

Lipid and/or glucose metabolism abnormalities in treated HIV-1-infected patients are associated with increased levels of APOC3 and, to a lesser extent, APOE plasma concentrations. Increased values are also related to clinical signs of insulin resistance and lipodystrophy.

Alterations of lipids and apolipoprotein CIII in very low density lipoprotein subspecies in type 2 diabetes

AIMS/HYPOTHESIS

Very low density lipoprotein (VLDL) particles are heterogeneous, comprising two main subspecies, VLDL 1 (Sf 60-400) and VLDL 2 (Sf 20-60). The aim of the study was to examine the distribution and composition of VLDL subspecies in type 2 diabetes.

SUBJECTS, MATERIALS AND METHODS

We studied the composition and concentration of triglyceride-rich lipoproteins (TRLs) in 217 type 2 diabetic patients and 93 control subjects between 50 and 75 years of age. Lipoprotein subspecies were separated by density-gradient ultracentrifugation. Apolipoprotein (apo) CIII and apo E in plasma and apo CIII in TRL subspecies were measured by nephelometry and apo CII in serum by a commercial kit using a single radial immunodiffusion method.

RESULTS

The concentrations of VLDL 1, VLDL 2 and intermediate density lipoprotein were significantly increased in type 2 diabetes subjects, the change being most marked for VLDL 1. There was a strong linear correlation between VLDL 1 triglycerides and plasma triglycerides in both groups (r = 0.879, p < 0.001 and r = 0.899, p < 0.001). Diabetic subjects had markedly higher plasma ratios of apo CII:apo CIII and apo CIII:apo E. Despite elevated plasma apo CIII, type 2 diabetic subjects had a relative deficiency of apo CIII in all TRL subspecies, suggesting profound disturbances of apo CIII metabolism.

CONCLUSIONS/INTERPRETATION

The elevation of VLDL 1 triglycerides is the major determinant of plasma triglyceride concentration in normal subjects and in type 2 diabetic individuals. Both apo CIII and apo E metabolism are disturbed in type 2 diabetes.

Comparison of the relation of triglyceride-rich lipoproteins and muscular artery compliance in healthy women versus healthy men

To determine whether structural features or concentrations of plasma lipoproteins are predictive of arterial compliance in healthy women versus healthy men, cohorts of 111 men and 112 women with a wide range of 10-year risks for coronary artery disease were selected using assessments based on the Framingham Heart Study. Age ranges were restricted to 35 to 69 years for men and 45 to 79 years for women. Lipid-lowering drugs or any evidence of vascular disease was cause for exclusion. Fasting lipoprotein analysis and arterial compliance measurements in thigh and calf were completed in all patients. Plasma triglyceride levels were the most powerful predictor of compliance in women. Weaker but significant relations were observed between plasma non-high-density lipoprotein cholesterol, apolipoprotein-B, and apolipoprotein-CIII. In contrast, the only significant predictor of compliance in men was body weight. Thus, the major lipid predictors of arterial stiffness in women are concentrations of triglyceride-rich lipoproteins. These results are consistent with previous findings that triglyceride measurements are more strongly related to clinical vascular events in women than in men.

The common insertional polymorphism in the APOC1 promoter is associated with serum apolipoprotein C-I levels in Hispanic children

We examined the effect of APOC1-317insCGTT allele status (HpaI RFLP, deletion [H1] and insertion [H2] alleles) on serum apolipoprotein (apo) C-I level in 362 Hispanic children in the Columbia University BioMarkers Study. The H2 allele was present in 147 subjects (40.6%). Serum apoC-I was 20% lower in the presence of the H2 allele in APOE epsilon3/epsilon3 homozygotes (P=0.003) but did not differ by H2 status in epsilon4 carriers. Insufficient numbers of epsilon2 carriers (N=45) were present for analysis. In multivariate analysis in the epsilon3/epsilon3 context, after adjusting for potential covariate effects and familial aggregation, the mean effect of H2/* versus H1/H1 on apoC-I level, was estimated to be 2.15+/-0.55mg/dl (P<0.0025). Plasma triglyceride level was weakly correlated with serum apoC-I level (Pearson's r=0.17, P<0.001) but was highly correlated with serum apoC-III (Pearson's r=0.74, P<0.0001). Nevertheless, presence of the H2 allele was not significantly associated with serum apoC-III level. Thus, the effect of APOC1 genotype on serum apoC-I level was not due to apoC-I level serving as a surrogate for triglyceride level. The APOC1-317insCGTT allele is a commonly polymorphic genetic marker that is associated with serum apoC-I level in the APOE epsilon3/epsilon3 context. These findings suggest that the mechanism of the previously described association with plasma TG is, at least in part, related to the correlation of the polymorphism with the level of expression of apoC-I.

Apolipoprotein C-III protein concentrations and gene polymorphisms in Type 1 diabetes: associations with microvascular disease complications in the DCCT/EDIC cohort

AIM

We investigated the associations of apolipoprotein C-III (apoCIII) protein and apoCIII gene variation with microvascular disease complications in Type 1 diabetes.

METHODS

The serum apoCIII concentration, and both a T(-455)-->C and a SacI gene polymorphisms were determined in 409 patients in the DCCT/EDIC cohort of patients with Type 1 diabetes. Correlations with albumin excretion rate (AER) and the severity of retinopathy were investigated.

RESULTS

Higher apoCIII concentrations were associated (P<.0001) with increased triglycerides (r=.78), total (r=.61) and LDL (r=.40) cholesterol, apoAI (r=.26), and apoB (r=.50), AER (r=.08), and the severity of retinopathy (ETDRS score, r=.11), and these relationships persisted after controlling for age, gender, body mass index (BMI), and HbA1c level. The apoCIII concentration was significantly higher in the group of patients with macroalbuminuria (AERs 300 mg/24 h) compared to the groups with microalbuminuria (AER 40-299 mg/24 h; P<.0001) or normoalbuminuria (AER <40 mg/24 h) (P<.0001). The apoCIII concentration also was significantly higher in the group of patients with severe retinopathy (ETDRS 10-23) compared to those with moderate (ETDRS 4-9; P<.02) or mild retinopathy (ETDRS 1-3; P<.0001). Neither the T(-455)-->C polymorphism nor a SacI polymorphism in the 3' UTR were associated with circulating apoCIII concentrations, nor the severity of nephropathy or retinopathy.

CONCLUSIONS

Elevated apoCIII levels have been associated with increased macrovascular disease risk. In the DCCT/EDIC cohort of patients, there was an independent positive association of apoCIII level with microvascular complications of Type 1 diabetes.

Apolipoprotein C-III, n-3 polyunsaturated fatty acids, and "insulin-resistant" T-455C APOC3 gene polymorphism in heart disease patients: example of gene-diet interaction

BACKGROUND

Apolipoprotein C-III (apo C-III) is a marker of cardiovascular disease risk associated with triglyceride (TG)-rich lipoproteins. The T-455C polymorphism in the insulin-responsive element of the APOC3 gene influences TG and apo C-III concentrations. Long-chain n-3 polyunsaturated fatty acids (PUFAs) contained in fish have well-known apo C-III-lowering properties.

METHODS

We investigated the possibility of an interactive effect between the APOC3 gene variant and erythrocyte n-3 PUFAs, suitable markers of dietary intake of fatty acids, on apo C-III concentrations in a population of 848 heart disease patients who had coronary angiography.

RESULTS

In the population as a whole, apo C-III concentrations were significantly inversely correlated with total erythrocyte PUFAs, but the correlation was not significant when only -455CC homozygous individuals were taken into account. In the total population and in subgroups with the -455TT and -455CT genotypes, the relative proportions of individuals presenting with increased apo C-III (i.e., above the 75th percentile value calculated on the entire population after exclusion of individuals taking lipids-lowering medications) decreased progressively as the n-3 PUFA and docosahexaenoic acid concentrations increased. The opposite situation was observed in the homozygous -455CC subgroup, in whom increasing erythrocyte n-3 PUFA and docosahexaenoic acid concentrations were associated with higher proportions of individuals with high apo C-III. A formal interactive effect between genotype and n-3 PUFAs was confirmed even after adjustment for possible confounding variables [age, sex, body mass index, smoking, coronary artery disease (CAD)/CAD-free status, or use of lipid-lowering medications] by logistic models.

CONCLUSION

Patients homozygous for the -455C APOC3 variant are poorly responsive to the apo C-III-lowering effects of n-3 PUFAs.

New risk factors for atherosclerosis and patient risk assessment

Advances in our understanding of the ways in which the traditional cardiovascular risk factors, including standard lipid (eg, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol) and nonlipid (eg, hypertension) risk factors, interact to initiate atherosclerosis and promote the development of cardiovascular disease have enhanced our ability to assess risk in the individual patient. In addition, the ongoing identification and understanding of so-called novel risk factors may further improve our ability to predict future risk when these are included along with the classic risk factors in assessing the global risk profile. This review briefly summarizes the evidence that some newer risk factors, including impaired fasting glucose, triglycerides and triglyceride-rich lipoprotein remnants, lipoprotein(a), homocysteine, and high-sensitivity C-reactive protein, contribute to an increased risk of coronary and cardiovascular diseases.

Apolipoprotein C-III protein concentrations and gene polymorphisms in type 1 diabetes: associations with lipoprotein subclasses

Serum apolipoprotein C-III (apoCIII) concentration and apoCIII gene polymorphisms have been shown to be a risk factor for cardiovascular disease; however, the underlying mechanisms remain unclear. In addition, no studies have been performed that address these issues in type 1 diabetes. The current study investigated apoCIII protein and apoCIII gene variation in a normotriglyceridemic (82 +/- 57 mg/dL) population of patients with type 1 diabetes, the Diabetes Control and Complications Trial/Epidemiology of Diabetes Intervention and Complications (DCCT/EDIC) cohort. Blood samples were obtained in 409 patients after an overnight fast. Serum apoCIII concentration was highly correlated with multiple changes in lipids and lipoproteins that resulted in an adverse cardiovascular disease risk profile. Higher apoCIII concentrations were associated (P < .0001) with increased triglycerides (r = 0.78), total (r = 0.61) and low-density lipoprotein (LDL) (r = 0.40) cholesterol, apoA-I (r = 0.26), and apoB (r = 0.50), and these relationships persisted after controlling for age, gender, body mass index (BMI), and hemoglobin A1c (HbA1c). Nuclear magnetic resonance (NMR) lipoprotein subclass analyses demonstrated that apoCIII was correlated with an increase in very-low-density lipoprotein (VLDL) subclasses (P = .0001). There also was a highly significant positive relationship between serum apoCIII concentration and the LDL particle concentration in both men (r = 0.49, P = .001) and women (r = 0.40, P = .001), and a highly significant negative relationship between serum apoCIII levels and average LDL particle size in both men (r = -0.37, P = .001) and women (r = -0.22, P = .001) due primarily to an augmentation in the small L1 subclass (r = 0.42, P = .0001). Neither the T(-455) --> C polymorphism affecting an insulin response element in the apoCIII gene promoter nor a SacI polymorphism in the 3'UTR were associated with any alterations in circulating apoCIII concentrations, serum lipids, apolipoprotein concentrations, lipoprotein composition, or parameters measured by NMR lipoprotein subclass analyses. In summary, elevated apoCIII concentration was associated with risk factors for cardiovascular disease in normolipidemic type 1 diabetic patients through associated changes in lipoprotein subfraction distributions, which were independent of apoCIII genotype.

Enhanced cholesterol efflux promotion in well-trained soccer players

It is widely accepted that aerobic physical activity is associated with a less atherogenic lipid and lipoprotein profile and, consequently, with a reduced cardiovascular risk. Both cross-sectional studies and prospective-interventional trials show that the most frequent modification observed consists of a slight but significant increase in high-density lipoprotein cholesterol (HDL-C) levels. Nevertheless, only few studies made an attempt to elucidate if this quantitative modification was accompanied by an improvement in any of HDL antiatherogenic functions. The purpose of this study was to evaluate the main steps of reverse cholesterol transport, the best known antiatherogenic function performed by HDL, in a group of well-trained soccer players (n = 35) in comparison to sedentary controls (n = 15). Average HDL-C levels were 12.5% higher in the sportsmen, in large part because of greater HDL2-C concentration. No statistically significant differences were observed in the other lipid- and lipoprotein-related parameters. The capacity to promote cholesterol efflux from Fu5AH cells was significantly higher in the soccer players than in the control individuals (20.5% +/- 0.4% v 15.9% +/- 1.2%, respectively, P < .001). However, lecithin:cholesterol acyltransferase (LCAT; 2.6 +/- 0.9 v 1.4 +/- 0.3%/mL.h, respectively) and cholesteryl ester transfer protein (CETP; 69.5 +/- 8.3 v 62.7 +/- 14.8%/mL.h, respectively) activities did not reach statistically significant difference between both groups. Correlation analysis showed that cholesterol efflux induced by serum samples was directly related to HDL-C (r = 0.59, P < .001), HDL2-C (r = 0.37, P < .01), and lipoprotein (Lp)A-I (r = 0.44, P < .05). On the other hand, negative correlations were observed with waist/hip ratio (r = -0.36, P < .05), low-density lipoprotein cholesterol (LDL-C; r = -0.33, P < .05), apolipoprotein B (apo B; r = -0.42, P < .05), and LpA-I;A-II (r = -0.51, P < .005). In conclusion, the well-known cardioprotective benefit of regular exercise could be based, at least in part, on a less atherogenic lipid and lipoprotein profile and an enhanced cellular cholesterol efflux.

Storage of human plasma samples leads to alterations in the lipoprotein distribution of apoC-III and apoE

The effect of frozen storage on lipoprotein distribution of apolipoprotein C-III (apoC-III) and apoE was investigated by measuring apoC-III and apoE by ELISA in HDL and apoB-containing lipoproteins of human plasma samples (n = 16) before and after 2 weeks of frozen storage (-20 degrees C). HDLs were separated by heparin-manganese precipitation (HMP) or by fast-protein liquid chromatography (FPLC). Total plasma apoC-III and apoE levels were not affected by frozen storage. HDL-HMP apoC-III and apoE levels were significantly higher in frozen versus fresh samples: 7.7 +/- 0.7 versus 6.7 +/- 0.7 mg/dl (P < 0.05) and 2.0 +/- 0.1 versus 1.2 +/- 0.1 mg/dl (P < 0.001), respectively. HDL-FPLC apoC-III and apoE, but not triglyceride (TG) or cholesterol, levels were also higher in frozen samples: 12.0 +/- 1.2 versus 7.5 +/- 0.6 mg/dl (P < 0.001) and 2.7 +/- 0.2 versus 1.6 +/- 0.2 mg/dl (P < 0.001), respectively. Frozen storage led to a decrease in apoC-III (-17 +/- 9%) and apoE (-19 +/- 9%) in triglyceride-rich lipoprotein. Redistribution of apoC-III and apoE was most evident in samples with high TG levels. HDL apoC-III and apoE levels were also significantly higher when measured in plasma stored at -80 degrees C. Our results demonstrate that lipoprotein distribution of apoC-III and apoE is affected by storage of human plasma, suggesting that analysis of frozen plasma should be avoided in studies relating lipoprotein levels of apoC-III and/or apoE to the incidence of coronary artery disease.

Atherogenic Lipoprotein Particles in Atherosclerosis

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