Effects of extended-release niacin on lipoprotein particle size, distribution, and inflammatory markers in patients with coronary artery disease

High-Density Lipoprotein Subclasses and Their Role in the Prevention and Treatment of Cardiovascular Disease: A Narrative Review

The association between high-density lipoprotein cholesterol (HDL-C) and cardiovascular disease (CVD) is controversial. HDL-C is one content type of high-density lipoprotein (HDL). HDL consists of diverse proteins and lipids and can be classified into different subclasses based on size, shape, charge, and density, and can change dynamically in disease states. Therefore, HDL-C levels alone cannot represent HDLs' cardioprotective role. In this review, we summarized the methods for separating HDL subclasses, the studies on the association between HDL subclasses and cardiovascular risk (CVR), and the impact of lipid-modifying medications and nonpharmacological approaches (exercise training, dietary omega fatty acids, and low-density lipoprotein apheresis) on HDL subclasses. As HDL is a natural nanoplatform, recombinant HDLs (rHDLs) have been used as a delivery system in vivo by loading small interfering RNA, drugs, contrast agents, etc. Therefore, we further reviewed the HDL subclasses used in rHDLs and their advantages and disadvantages. This review would provide recommendations and guidance for future studies on HDL subclasses' cardioprotective roles.

ESPEN micronutrient guideline

BACKGROUND

Trace elements and vitamins, named together micronutrients (MNs), are essential for human metabolism. Recent research has shown the importance of MNs in common pathologies, with significant deficiencies impacting the outcome.

OBJECTIVE

This guideline aims to provide information for daily clinical nutrition practice regarding assessment of MN status, monitoring, and prescription. It proposes a consensus terminology, since many words are used imprecisely, resulting in confusion. This is particularly true for the words "deficiency", "repletion", "complement", and "supplement".

METHODS

The expert group attempted to apply the 2015 standard operating procedures (SOP) for ESPEN which focuses on disease. However, this approach could not be applied due to the multiple diseases requiring clinical nutrition resulting in one text for each MN, rather than for diseases. An extensive search of the literature was conducted in the databases Medline, PubMed, Cochrane, Google Scholar, and CINAHL. The search focused on physiological data, historical evidence (published before PubMed release in 1996), and observational and/or randomized trials. For each MN, the main functions, optimal analytical methods, impact of inflammation, potential toxicity, and provision during enteral or parenteral nutrition were addressed. The SOP wording was applied for strength of recommendations.

RESULTS

There was a limited number of interventional trials, preventing meta-analysis and leading to a low level of evidence. The recommendations underwent a consensus process, which resulted in a percentage of agreement (%): strong consensus required of >90% of votes. Altogether the guideline proposes sets of recommendations for 26 MNs, resulting in 170 single recommendations. Critical MNs were identified with deficiencies being present in numerous acute and chronic diseases. Monitoring and management strategies are proposed.

CONCLUSION

This guideline should enable addressing suboptimal and deficient status of a bundle of MNs in at-risk diseases. In particular, it offers practical advice on MN provision and monitoring during nutritional support.

Influence of lipid-lowering drugs on inflammation: what is yet to be done?

Atherosclerosis is a chronic inflammatory disease that is associated with risk of cardiovascular events. The best-characterised and well-standardised clinical indicator of inflammation is C-reactive protein. Current evidence-based drug therapies for prevention and treatment of cardiovascular diseases are mainly focused on reduction of low-density lipoprotein cholesterol. However, these drugs do not provide sufficient protection against recurrent cardiovascular events. One of the possible mechanisms behind this recurrence might be the persistence of residual inflammation. For the most commonly used lipid-lowering drugs, the statins, their reduction of cardiovascular events goes beyond lowering of low-density lipoprotein cholesterol. Here, we review the effects of these lipid-lowering drugs on inflammation, considering statins, ezetimibe, fibrates, niacin, proprotein convertase subtilisin/kexin type 9 inhibitors, bempedoic acid, ethyl eicosapentaenoic acid and antisense oligonucleotides. We focus in particular on C-reactive protein, and discuss how the effects of the statins might be related to reduced rates of cardiovascular events.

Subpopulations of High-Density Lipoprotein: Friends or Foes in Cardiovascular Disease Risk in Chronic Kidney Disease?

Dyslipidemia is a major traditional risk factor for cardiovascular disease (CVD) in chronic kidney disease (CKD) patients, although the altered lipid profile does not explain the number and severity of CVD events. High-density lipoprotein (HDL) is a heterogeneous (size, composition, and functionality) population of particles with different atherogenic or atheroprotective properties. HDL-cholesterol concentrations per se may not entirely reflect a beneficial or a risk profile for CVD. Large HDL in CKD patients may have a unique proteome and lipid composition, impairing their cholesterol efflux capacity. This lack of HDL functionality may contribute to the paradoxical coexistence of increased large HDL and enhanced risk for CVD events. Moreover, CKD is associated with inflammation, oxidative stress, diabetes, and/or hypertension that are able to interfere with the anti-inflammatory, antioxidative, and antithrombotic properties of HDL subpopulations. How these changes interfere with HDL functions in CKD is still poorly understood. Further studies are warranted to fully clarify if different HDL subpopulations present different functionalities and/or atheroprotective effects. To achieve this goal, the standardization of techniques would be valuable.

The Relationship Between Nutrition and Atherosclerosis

Atherosclerosis is the basic pathological process of many diseases, such as coronary atherosclerosis and stroke. Nutrients can affect the occurrence and development of atherosclerosis. At present, in nutrition science, the research on atherosclerosis focuses on which nutrients play an important role in its prevention strategy, and what are the possible mechanisms of its action. In the current study, the process of atherosclerosis can be affected by adjusting the proportion of nutrients in the diet. In this review, we pay attention to the effects of phytosterols, omega-3-polyunsaturated fatty acids, polyphenol, vitamin, and other nutrients on atherosclerosis, pay attention to their current epidemiological status, current nutritional research results, and prevention or a possible mechanism to reduce the risk of development of atherosclerosis. So that more personalized nutritional approaches may be more effective in terms of nutritional intervention responses to atherosclerosis.

Evaluation of Dietary Niacin and New-Onset Hypertension Among Chinese Adults

IMPORTANCE

The relationship of dietary niacin intake with the risk of hypertension remains unknown.

OBJECTIVE

To determine the prospective association between dietary niacin intake and new-onset hypertension, and examine factors that may modify the association among Chinese adults.

DESIGN, SETTING, AND PARTICIPANTS

This nationwide cohort study of 12 243 Chinese adults used dietary intake data from 7 rounds of the China Health and Nutrition Survey. Dietary intake was measured by 3 consecutive 24-hour dietary recalls from participants in combination with a weighing inventory taken over the same 3 days at the household level. Statistical analysis was conducted from May 2020 to August 2020.

EXPOSURES

Dietary intake.

MAIN OUTCOMES AND MEASURES

The study outcome was new-onset hypertension, defined as systolic blood pressure 140 mm Hg or greater and/or diastolic blood pressure 90 mm Hg or greater, diagnosis by physician, or current antihypertensive treatment during the follow-up.

RESULTS

The mean (SD) age of the study population was 41.2 (14.2) years, and 5728 (46.8%) of participants were men. The mean (SD) dietary niacin intake level was 14.8 (4.1) mg/d. A total of 4306 participants developed new-onset hypertension during a median (interquartile range) follow-up duration of 6.1 (3.6-11.3) years. When dietary niacin was assessed in quartiles, the lowest risk of new-onset hypertension was found in participants in quartile 3 (14.3 to <16.7 mg/d; adjusted hazard ratio, 0.83; 95% CI, 0.75-0.90) compared with those in quartile 1 (<12.4 mg/d). Consistently in the threshold analysis, for every 1 mg/d increase in dietary niacin, there was a 2% decrease in new-onset hypertension (adjusted HR, 0.98; 95% CI, 0.96-1.00) in those with dietary niacin intake less than 15.6 mg/d, and a 3% increase in new-onset hypertension (adjusted HR, 1.03; 95% CI, 1.02-1.04) in participants with dietary niacin 15.6 mg/d or greater. Based on these results, there was a J-shaped association between dietary niacin intake and new-onset hypertension in the general population of Chinese adults, with an inflection point at 15.6 mg/d and a minimal risk at 14.3 to 16.7 mg/d (quartile 3) of dietary niacin intake.

CONCLUSIONS AND RELEVANCE

The results of this study provide some evidence for maintaining the optimal dietary niacin intake levels for the primary prevention of hypertension.

Niacin Attenuates Pulmonary Hypertension Through H-PGDS in Macrophages

RATIONALE

Pulmonary arterial hypertension (PAH) is characterized by progressive pulmonary vascular remodeling, accompanied by varying degrees of perivascular inflammation. Niacin, a commonly used lipid-lowering drug, possesses vasodilating and proresolution effects by promoting the release of prostaglandin D₂ (PGD₂). However, whether or not niacin confers protection against PAH pathogenesis is still unknown.

OBJECTIVE

This study aimed to determine whether or not niacin attenuates the development of PAH and, if so, to elucidate the molecular mechanisms underlying its effects.

METHODS AND RESULTS

Vascular endothelial growth factor receptor inhibitor SU5416 and hypoxic exposure were used to induce pulmonary hypertension (PH) in rodents. We found that niacin attenuated the development of this hypoxia/SU5416-induced PH in mice and suppressed progression of monocrotaline-induced and hypoxia/SU5416-induced PH in rats through the reduction of pulmonary artery remodeling. Niacin boosted PGD₂ generation in lung tissue, mainly through H-PGDS (hematopoietic PGD₂ synthases). Deletion of H-PGDS, but not lipocalin-type PGDS, exacerbated the hypoxia/SU5416-induced PH in mice and abolished the protective effects of niacin against PAH. Moreover, H-PGDS was expressed dominantly in infiltrated macrophages in lungs of PH mice and patients with idiopathic PAH. Macrophage-specific deletion of H-PGDS markedly decreased PGD₂ generation in lungs, aggravated hypoxia/SU5416-induced PH in mice, and attenuated the therapeutic effect of niacin on PAH.

CONCLUSIONS

Niacin treatment ameliorates the progression of PAH through the suppression of vascular remodeling by stimulating H-PGDS-derived PGD₂ release from macrophages.

Deficiency of metabolite sensing receptor HCA2 impairs the salutary effect of niacin in hemorrhagic shock

Inflammation and cellular energetics play critical roles in organ dysfunction following hemorrhagic shock. Recent studies suggest a putative role for sirtuin 1 (SIRT1) in potentiating mitochondrial function and improving organ function following hemorrhagic shock in animal models. SIRT1 is an NAD⁺ dependent protein deacetylase and increased availability of NAD⁺ has been shown to augment SIRT1 activity. As niacin is a precursor of NAD⁺, in this study, we tested whether niacin can improve survival following hemorrhagic shock. However niacin also mediates its biological action by binding to its receptor, hydroxyl-carboxylic acid receptor 2 (HCA2 or Gpr109a); so we examined whether the effect of niacin is mediated by binding to Gpr109a or by increasing NAD⁺ availability. We found that niacin administered intravenously to rats subjected to hemorrhagic injury (HI) in the absence of fluid resuscitation resulted in a significantly prolonged duration of survival. However, treatment of rats with similar doses of nicotinamide mononucleotide (NMN), a precursor to NAD⁺ that does not bind Gpr109a, did not extend survival following HI. The duration of survival due to niacin treatment was significantly reduced in Gpr109a^-/- mice subjected to HI. These experiments demonstrated that the Gpr109a receptor-mediated pathway contributed significantly to niacin mediated salutary effect. Further studies showed improvement in markers of cellular energetics and attenuation of inflammatory response with niacin treatment. In conclusion, we report that Gpr109a-dependent signalling is important in restoring cellular energetics and immunometabolism following hemorrhagic shock.

Current Therapies Focused on High-Density Lipoproteins Associated with Cardiovascular Disease

High-density lipoproteins (HDL) comprise a heterogeneous family of lipoprotein particles divided into subclasses that are determined by density, size and surface charge as well as protein composition. Epidemiological studies have suggested an inverse correlation between High-density lipoprotein-cholesterol (HDL-C) levels and the risk of cardiovascular diseases and atherosclerosis. HDLs promote reverse cholesterol transport (RCT) and have several atheroprotective functions such as anti-inflammation, anti-thrombosis, and anti-oxidation. HDLs are considered to be atheroprotective because they are associated in serum with paraoxonases (PONs) which protect HDL from oxidation. Polyphenol consumption reduces the risk of chronic diseases in humans. Polyphenols increase the binding of HDL to PON1, increasing the catalytic activity of PON1. This review summarizes the evidence currently available regarding pharmacological and alternative treatments aimed at improving the functionality of HDL-C. Information on the effectiveness of the treatments has contributed to the understanding of the molecular mechanisms that regulate plasma levels of HDL-C, thereby promoting the development of more effective treatment of cardiovascular diseases. For that purpose, Scopus and Medline databases were searched to identify the publications investigating the impact of current therapies focused on high-density lipoproteins.

Consumption of a defined, plant-based diet reduces lipoprotein(a), inflammation, and other atherogenic lipoproteins and particles within 4 weeks

BACKGROUND

Lipoprotein(a) [Lp(a)] is a highly atherogenic lipoprotein and is minimally effected by lifestyle changes. While some drugs can reduce Lp(a), diet has not consistently shown definitive reduction of this biomarker. The effect of consuming a plant-based diet on serum Lp(a) concentrations have not been previously evaluated.

HYPOTHESIS

Consumption of a defined, plant-based for 4 weeks reduces Lp(a).

METHODS

Secondary analysis of a previous trial was conducted, in which overweight and obese individuals (n = 31) with low-density lipoprotein cholesterol concentrations >100 mg/dL consumed a defined, plant-based diet for 4 weeks. Baseline and 4-week labs were collected. Data were analyzed using a paired samples t-test.

RESULTS

Significant reductions were observed for serum Lp(a) (-32.0 ± 52.3 nmol/L, P = 0.003), apolipoprotein B (-13.2 ± 18.3 mg/dL, P < 0.0005), low-density lipoprotein (LDL) particles (-304.8 ± 363.0 nmol/L, P < 0.0005) and small-dense LDL cholesterol (-10.0 ± 9.2 mg/dL, P < 0.0005). Additionally, serum interleukin-6 (IL-6), total white blood cells, lipoprotein-associated phospholipase A2 (Lp-PLA2), high-sensitivity c-reactive protein (hs-CRP), and fibrinogen were significantly reduced (P ≤ 0.004).

CONCLUSIONS

A defined, plant-based diet has a favorable impact on Lp(a), inflammatory indicators, and other atherogenic lipoproteins and particles. Lp(a) concentration was previously thought to be only minimally altered by dietary interventions. In this protocol however, a defined plant-based diet was shown to substantially reduce this biomarker. Further investigation is required to elucidate the specific mechanisms that contribute to the reductions in Lp(a) concentrations, which may include alterations in gene expression.

Relations of GlycA and lipoprotein particle subspecies with cardiovascular events and mortality: A post hoc analysis of the AIM-HIGH trial

BACKGROUND

The Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes trial showed no incremental benefit of extended-release niacin (ERN) therapy added to simvastatin in subjects with cardiovascular disease (CVD).

OBJECTIVES

To examine the effects of ERN treatment on lipoprotein particles and GlycA, a new marker of systemic inflammation, and their relations with incident CVD events including mortality.

METHODS

GlycA and very low-density lipoprotein, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) particle subclasses were quantified by nuclear magnetic resonance spectroscopy using available stored baseline (n = 2754) and 1-year in-trial (n = 2581) samples. Associations with CVD events and all-cause mortality were assessed using multivariable Cox proportional hazards regression adjusted for age, sex, diabetes, treatment assignment, and lipoproteins.

RESULTS

Compared to placebo, ERN treatment lowered very low-density lipoprotein and LDL and increased HDL particle concentrations, increased LDL and HDL particle sizes (all P < .0001), but did not affect GlycA. Baseline and in-trial GlycA levels were associated with increased risk of CVD events: hazard ratio (HR) per SD increment, 1.17 (95% confidence interval [CI], 1.06-1.28) and 1.13 (1.02-1.26), respectively. However, none of the lipoprotein particle classes or subclasses was associated with incident CVD. By contrast, all-cause mortality was significantly associated with both GlycA (baseline HR: 1.46 [1.22-1.75]; in-trial HR: 1.41 [1.24-1.60]) and low levels of small HDL particles (baseline HR: 0.69 [0.56-0.86]; in-trial HR: 0.69 [0.56-0.86]).

CONCLUSIONS

This Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes trial post hoc substudy indicates that inflammation, as indexed by GlycA, is unaffected by ERN treatment but is significantly associated with the residual risk of CVD and death in patients treated to low levels of LDL cholesterol.

Niacin ameliorates ulcerative colitis via prostaglandin D2-mediated D prostanoid receptor 1 activation

Niacin, as an antidyslipidemic drug, elicits a strong flushing response by release of prostaglandin (PG) D₂. However, whether niacin is beneficial for inflammatory bowel disease (IBD) remains unclear. Here, we observed niacin administration‐enhanced PGD₂ production in colon tissues in dextran sulfate sodium (DSS)‐challenged mice, and protected mice against DSS or 2,4,6‐trinitrobenzene sulfonic acid (TNBS)‐induced colitis in D prostanoid receptor 1 (DP1)‐dependent manner. Specific ablation of DP1 receptor in vascular endothelial cells, colonic epithelium, and myeloid cells augmented DSS/TNBS‐induced colitis in mice through increasing vascular permeability, promoting apoptosis of epithelial cells, and stimulating pro‐inflammatory cytokine secretion of macrophages, respectively. Niacin treatment improved vascular permeability, reduced apoptotic epithelial cells, promoted epithelial cell update, and suppressed pro‐inflammatory gene expression of macrophages. Moreover, treatment with niacin‐containing retention enema effectively promoted UC clinical remission and mucosal healing in patients with moderately active disease. Therefore, niacin displayed multiple beneficial effects on DSS/TNBS‐induced colitis in mice by activation of PGD₂/DP1 axis. The potential efficacy of niacin in management of IBD warrants further investigation.

Nicotinamide riboside is uniquely and orally bioavailable in mice and humans

Nicotinamide riboside (NR) is in wide use as an NAD+ precursor vitamin. Here we determine the time and dose-dependent effects of NR on blood NAD+ metabolism in humans. We report that human blood NAD+ can rise as much as 2.7-fold with a single oral dose of NR in a pilot study of one individual, and that oral NR elevates mouse hepatic NAD+ with distinct and superior pharmacokinetics to those of nicotinic acid and nicotinamide. We further show that single doses of 100, 300 and 1,000 mg of NR produce dose-dependent increases in the blood NAD+ metabolome in the first clinical trial of NR pharmacokinetics in humans. We also report that nicotinic acid adenine dinucleotide (NAAD), which was not thought to be en route for the conversion of NR to NAD+, is formed from NR and discover that the rise in NAAD is a highly sensitive biomarker of effective NAD+ repletion.

Niacin and its metabolites as master regulators of macrophage activation

Niacin is a broad-spectrum lipid-regulating drug used for clinical therapy of chronic high-grade inflammatory diseases. However, the mechanisms by which either niacin or the byproducts of its catabolism ameliorate these inflammatory diseases are not clear yet. Human circulating monocytes and mature macrophages were used to analyze the effects of niacin and its metabolites (NAM, NUA and 2-Pyr) on oxidative stress, plasticity and inflammatory response by using biochemical, flow cytometry, quantitative real-time PCR and Western blot technologies. Niacin, NAM and 2-Pyr significantly decreased ROS, NO and NOS2 expression in LPS-treated human mature macrophages. Niacin and NAM skewed macrophage polarization toward antiinflammatory M2 macrophage whereas a trend toward proinflammatory M1 macrophage was noted following treatment with NUA. Niacin and NAM also reduced the inflammatory competence of LPS-treated human mature macrophages and promoted bias toward antiinflammatory CD14⁺CD16⁺⁺ nonclassical human primary monocytes. This study reveals for the first time that niacin and its metabolites possess antioxidant, reprogramming and antiinflammatory properties on human primary monocytes and monocyte-derived macrophages. Our findings imply a new understanding of the mechanisms by which niacin and its metabolites favor a continuous and gradual plasticity process in the human monocyte/macrophage system.

An evaluation of RVX-208 for the treatment of atherosclerosis

INTRODUCTION

RVX-208 is a first-in-class, orally active, novel small molecule in development by Resverlogix Corporation (Calgary, AB, Canada). It acts through an epigenetic mechanism by inhibiting the bromodomain and extraterminal (BET) family of proteins, increasing apolipoprotein A-I (apoA-I) and targeting high-density lipoprotein (HDL) metabolism, including generating of nascent HDL and increased larger HDL particles, resulting in the stimulation of reverse cholesterol transport. RVX-208 also has a beneficial effect on inflammatory factors known to be involved in atherosclerosis and plaque stability. New therapeutic strategies are needed for patients with atherosclerosis.

AREAS COVERED

In this review, the authors evaluate the use of RVX-208 as an agent for the treatment of atherosclerosis. The article is based on a literature search considering both animal and human studies available on PubMed as well as Media Releases from the Resverlogix Corporation.

EXPERT OPINION

The current evidence suggests promising beneficial effects of this novel drug in the prevention and treatment of atherosclerosis and other metabolic disorders. Its unique mechanism of action is encouraging; it affects several pathways and has a modest effect on HDL levels. There is also a shift in particle size to larger HDL particles, which may have potent atheroprotective effects. Future clinical development is needed, including safety assessment.

The Effects of Niacin on Inflammation in Patients with Non-ST Elevated Acute Coronary Syndrome

BACKGROUND

In this study, we aimed to evaluate the effects of niacin on high sensitivity C reactive protein (hs-CRP) and cholesterol levels in non-ST elevated acute coronary syndrome (NSTE-ACS) patients.

METHODS

In this prospective, open label study, 48 NSTE-ACS were randomized to niacin or control group. Patients continued their optimal medical therapy in the control group. In the niacin group patients were assigned to receive extended-release niacin 500 mg/day. Patients were contacted 1 month later to assess compliance and side effects. Blood samples for hs-CRP were obtained upon admittance to the coronary care unit, in the third day and in the first month of the treatment. Fasting blood samples for cholesterol levels were obtained before and 30 days after the treatment. The primary end point of the study was to evaluate changes in hs-CRP, cholesterol levels, short-term cardiovascular events, and the safety of niacin in NSTE-ACS.

RESULTS

Baseline demographic, clinical and laboratory characteristics were similar between the two groups. Logarithmic transformation of baseline and 3(rd) day hs-CRP levels were similar between the groups; but 1 month later, logarithmic transformation of hs-CRP level was significantly lower in the niacin group (0.43 ± 0.39 to 0.83 ± 0.91, p = 0.04). HDL-C level was significantly increased in the niacin group during follow-up. Drug related side effects were seen in 7 patients in the niacin group but no patients discontinued niacin.

CONCLUSIONS

Our findings demonstrate that lower dose extended release niacin can be used safely and decreases hs-CRP and lipid parameters successfully in NSTE-ACS patients.

KEY WORDS

Acute coronary syndrome; hs-CRP; Inflammation; Niacin.

B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review

The B-vitamins comprise a group of eight water soluble vitamins that perform essential, closely inter-related roles in cellular functioning, acting as co-enzymes in a vast array of catabolic and anabolic enzymatic reactions. Their collective effects are particularly prevalent to numerous aspects of brain function, including energy production, DNA/RNA synthesis/repair, genomic and non-genomic methylation, and the synthesis of numerous neurochemicals and signaling molecules. However, human epidemiological and controlled trial investigations, and the resultant scientific commentary, have focused almost exclusively on the small sub-set of vitamins (B9/B12/B6) that are the most prominent (but not the exclusive) B-vitamins involved in homocysteine metabolism. Scant regard has been paid to the other B vitamins. This review describes the closely inter-related functions of the eight B-vitamins and marshals evidence suggesting that adequate levels of all members of this group of micronutrients are essential for optimal physiological and neurological functioning. Furthermore, evidence from human research clearly shows both that a significant proportion of the populations of developed countries suffer from deficiencies or insufficiencies in one or more of this group of vitamins, and that, in the absence of an optimal diet, administration of the entire B-vitamin group, rather than a small sub-set, at doses greatly in excess of the current governmental recommendations, would be a rational approach for preserving brain health.

[Lp-PLA2, a biomarker of vascular inflammation and vulnerability of atherosclerosis plaques]

A chronic inflammation is involved in various stages of development of the atherosclerotic plaques. Among the emerging biomarkers of atherogenesis, the lipoprotein-associated phospholipase A2 (Lp-PLA2), formerly known as PAF-acetylhydrolase (McIntyre et al., 2009), hydrolyses the oxidized short chain phospholipids of low-density lipoproteins (LDL), thereby releasing pro-inflammatory mediators (lysophospholipids and oxidized fatty acids). Lp-PLA2, produced by monocytes/macrophages and T-lymphocytes, and mainly associated with LDL (Gazi et al., 2005), is predominantly expressed in the necrotic center of the atherosclerotic plaques and in the macrophage-rich areas (Kolodgie et al., 2006). It would have a predictive role of cardiovascular (CV) events in relation to the vulnerability of atherosclerotic plaques. Determination of Lp-PLA2 has been proposed in the assessment of the CV risk, to ensure a better stratification of populations at intermediate risk for targeted therapy (Davidson et al., 2008). Its proatherogenic role suggested that inhibition of its activity could ensure a better vascular protection in combination with cholesterol-lowering agents. Nevertheless, Lp-PLA2 is not yet a fully validated marker for use in daily clinical practice, especially since the studies using an inhibitor of Lp-PLA2 (darapladib) (STABILITY Investigators et al., 2014; O'Donoghue et al., 2014) did not show any reduction in coronary events. Lp-PLA2 could have a site-specific role in plaque inflammation and development (Fenning et al., 2015). High Lp-PLA2 activity could reflect a response to pro-inflammatory stress characteristic of atherosclerosis (Marathe et al., 2014). This presentation aims at clarifying the involvement of Lp-PLA2 in the pathophysiology of atherosclerosis, and at assessing its interest both as a biomarker for the onset of CV events and as a therapeutic target.

HDL particle number and size as predictors of cardiovascular disease

Previous studies indicate that reduced concentrations of circulating high-density lipoprotein (HDL) particles can be superior to HDL-cholesterol (HDL-C) levels as a predictor of cardiovascular disease. Measurements of HDL particle numbers, therefore, bear a potential for the improved assessment of cardiovascular risk. Furthermore, such measurement can be relevant for the evaluation of novel therapeutic approaches targeting HDL. Modern in-depth analyses of HDL particle profile may further improve evaluation of cardiovascular risk. Although clinical relevance of circulating concentrations of HDL subpopulations to cardiovascular disease remains controversial, the negative relationship between the number of large HDL particles and cardiovascular disease suggests that assessment of HDL particle profile can be clinically useful. Reduced mean HDL size is equally associated with cardiovascular disease in large-scale clinical studies. Since HDL-C is primarily carried in the circulation by large, lipid-rich HDL particles, the inverse relationship between HDL size and cardiovascular risk can be secondary to those established for plasma levels of HDL particles, HDL-C, and large HDL. The epidemiological data thereby suggest that HDL particle number may represent a more relevant therapeutic target as compared to HDL-C.

Effect of Extended-Release Niacin on High-Density Lipoprotein (HDL) Functionality, Lipoprotein Metabolism, and Mediators of Vascular Inflammation in Statin-Treated Patients

Background

The aim of this study was to explore the influence of extended-release niacin/laropiprant (ERN/LRP) versus placebo on high-density lipoprotein (HDL) antioxidant function, cholesterol efflux, apolipoprotein B100 (apoB)-containing lipoproteins, and mediators of vascular inflammation associated with 15% increase in high-density lipoprotein cholesterol (HDL-C). Study patients had persistent dyslipidemia despite receiving high-dose statin treatment.

Methods and Results

In a randomized double-blind, placebo-controlled, crossover trial, we compared the effect of ERN/LRP with placebo in 27 statin-treated dyslipidemic patients who had not achieved National Cholesterol Education Program-ATP III targets for low-density lipoprotein cholesterol (LDL-C). We measured fasting lipid profile, apolipoproteins, cholesteryl ester transfer protein (CETP) activity, paraoxonase 1 (PON1) activity, small dense LDL apoB (sdLDL-apoB), oxidized LDL (oxLDL), glycated apoB (glyc-apoB), lipoprotein phospholipase A2 (Lp-PLA2), lysophosphatidyl choline (lyso-PC), macrophage chemoattractant protein (MCP1), serum amyloid A (SAA) and myeloperoxidase (MPO). We also examined the capacity of HDL to protect LDL from in vitro oxidation and the percentage cholesterol efflux mediated by apoB depleted serum. ERN/LRP was associated with an 18% increase in HDL-C levels compared to placebo (1.55 versus 1.31 mmol/L, P<0.0001). There were significant reductions in total cholesterol, triglycerides, LDL cholesterol, total serum apoB, lipoprotein (a), CETP activity, oxLDL, Lp-PLA2, lyso-PC, MCP1, and SAA, but no significant changes in glyc-apoB or sdLDL-apoB concentration. There was a modest increase in cholesterol efflux function of HDL (19.5%, P=0.045), but no change in the antioxidant capacity of HDL in vitro or PON1 activity.

Conclusions

ERN/LRP reduces LDL-associated mediators of vascular inflammation, but has varied effects on HDL functionality and LDL quality, which may counter its HDL-C-raising effect.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01054508.

Effects of established hypolipidemic drugs on HDL concentration, subclass distribution, and function

The knowledge of an inverse relationship between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and rates of cardiovascular disease has led to the concept that increasing plasma HDL-C levels would be protective against cardiovascular events. Therapeutic interventions presently available to correct the plasma lipid profile have not been designed to specifically act on HDL, but have modest to moderate effects on plasma HDL-C concentrations. Statins, the first-line lipid-lowering drug therapy in primary and secondary cardiovascular prevention, have quite modest effects on plasma HDL-C concentrations (2-10%). Fibrates, primarily used to reduce plasma triglyceride levels, also moderately increase HDL-C levels (5-15%). Niacin is the most potent available drug in increasing HDL-C levels (up to 30%), but its use is limited by side effects, especially flushing.The present chapter reviews the effects of established hypolipidemic drugs (statins, fibrates, and niacin) on plasma HDL-C levels and HDL subclass distribution, and on HDL functions, including cholesterol efflux capacity, endothelial protection, and antioxidant properties.

Paraoxonase responses to exercise and niacin therapy in men with metabolic syndrome

Our purpose was to characterize changes in paraoxonase 1 (PON1) activity and concentration after single aerobic exercise sessions conducted before and after 6 weeks of niacin therapy in men with metabolic syndrome (MetS). Twelve men with MetS expended 500 kcal by walking at 65% of VO2max before and after a 6-week regimen of niacin. Niacin doses were titrated by 500 mg/week from 500 to 1500 mg/day and maintained at 1500 mg/day for the last 4 weeks. Fasting blood samples were collected before and 24 hours after each exercise session and analyzed for PON1 activity, PON1 concentration, myeloperoxidase (MPO), apolipoprotein A1, oxidized low-density lipoprotein (oLDL), lipoprotein particle sizes and concentrations. PON1 activity, PON1 concentration, MPO, and oLDL were unaltered following the independent effects of exercise and niacin (P > 0.05 for all). High-density lipoprotein particle size decreased by 3% (P = 0.040) and concentrations of small very low-density lipoprotein increased (P = 0.016) following exercise. PON1 activity increased 6.1% (P = 0.037) and PON1 concentrations increased 11.3% (P = 0.015) with the combination of exercise and niacin. Exercise and niacin works synergistically to increase PON1 activity and concentration with little or no changes in lipoproteins or markers of lipid oxidation.

Niacin inhibits vascular inflammation via downregulating nuclear transcription factor-κB signaling pathway

The study aimed to investigate the effect of niacin on vascular inflammatory lesions in vivo and in vitro as well as its lipid-regulating mechanism. In vivo study revealed that niacin downregulated the levels of inflammatory factors (IL-6 and TNF-α) in plasma, suppressed protein expression of CD68 and NF-κB p65 in arterial wall, and attenuated oxidative stress in guinea pigs that have been fed high fat diet. In vitro study further confirmed that niacin decreased the secretion of IL-6 and TNF-α and inhibited NF-κB p65 and notch1 protein expression in oxLDL-stimulated HUVECs and THP-1 macrophages. Moreover, niacin attenuated oxLDL-induced apoptosis of HUVECs as well. In addition, niacin significantly lessened lipid deposition in arterial wall, increased HDL-C and apoA levels and decreased TG and non-HDL-C levels in plasma, and upregulated the mRNA amount of cholesterol 7α-hydroxylase A1 in liver of guinea pigs. These data suggest for the first time that niacin inhibits vascular inflammation in vivo and in vitro via downregulating NF-κB signaling pathway. Furthermore, niacin also modulates plasma lipid by upregulating the expression of factors involved in the process of reverse cholesterol transport.

Intensive lifestyle modification reduces Lp-PLA2 in dyslipidemic HIV/HAART patients

PURPOSE

Patients with dyslipidemia associated with HIV-1 infection and highly active antiretroviral therapy (HAART) have elevated levels of Lp-PLA2 and CCL5/regulated on activation, normal T-cell expressed and secreted (RANTES), which may increase the risk of cardiovascular disease.

PURPOSE

This study aimed to determine whether an intensive diet and exercise (D/E) program, independently or combined with fenofibrate or niacin, could reduce Lp-PLA2 or RANTES.

METHODS

Patients with hypertriglyceridemic HIV on stable HAART (n = 107) were randomized to one of five interventions: 1) usual care, 2) D/E with placebos, 3) D/E with fenofibrate and placebo, 4) D/E with niacin and placebo, or 5) D/E with fenofibrate and niacin for 24 wk. Lp-PLA2 and RANTES concentrations were measured in fasting plasma samples at baseline and postintervention. General linear models were used to compare Lp-PLA2 and RANTES levels between the five groups postintervention, controlling for baseline levels, age, body mass index, CD4 T-cell count, viral load, duration of infection, and HAART.

RESULTS

At baseline, fasting plasma Lp-PLA2 (388.5 ± 127.5 ng·mL) and RANTES (43.8 ± 25.5 ng·mL) levels were elevated when compared with healthy controls. Posttreatment Lp-PLA2 mass was lower in patients who received D/E only (323.0 ± 27.2 ng·mL), D/E plus fenofibrate (327.2 ± 25.9 ng·mL), and D/E plus niacin (311.1 ± 27.8 ng·mL) when compared with patients receiving usual care (402.2 ± 25.3 ng·mL). RANTES concentrations were not significantly affected by any intervention.

CONCLUSIONS

Elevated plasma Lp-PLA2 mass can be reduced by an intensive D/E program in patients with HIV/HAART-associated dyslipidemia. RANTES is elevated but is not reduced by lifestyle modification, fenofibrate, or niacin.

The Therapeutic Role of Niacin in Dyslipidemia Management

There is abundant epidemiologic evidence to support the independent, inverse relationship between low levels of high-density lipoprotein cholesterol (HDL-C) and incident cardiovascular (CV) risk, the clinical importance of which is underscored by the high prevalence of low HDL-C in populations with coronary heart disease (CHD), with or without elevated levels of low-density lipoprotein cholesterol (LDL-C). The National Cholesterol Education Program recommended that optimal treatment for high-risk patients includes both lowering LDL-C and non-HDL-C to risk stratified levels and raising HDL-C when it is <40 mg/dL, although no target level for the latter lipoprotein was suggested. Niacin is the most powerful agent currently available for raising low levels of HDL-C. It also induces significant reductions in triglycerides, lipoprotein(a), and LDL-C levels while also favorably altering LDL particle size and number. In the Coronary Drug Project, niacin treatment was associated with significant reductions in CV events and long-term mortality, similar to the reductions seen in the statin monotherapy trials. In combination trials, niacin plus a statin or bile acid sequestrant produces additive reductions in CHD morbidity and mortality and promotes regression of coronary atherosclerosis. Recently, 2 clinical outcome trials (Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides and Impact on Global Health Outcomes [AIM-HIGH] and Second Heart Protection Study [HPS-2 THRIVE]) failed to show a reduction in CV events in patients treated to optimally low levels of LDL-C. Despite favorable effects on HDL-C and triglycerides, these studies did not demonstrate incremental clinical benefit with niacin when added to simvastatin, although notable limitations were identified in each of these trials. Thus, there is insufficient evidence from clinical trials to recommend HDL-targeted therapy for additional event reduction at the present time. However, niacin should continue to be used as an adjuvant therapy for reducing atherogenic lipoprotein burden in patients who have not reached their risk stratified LDL-C and non-HDL-C targets.

Vascular endothelial function and oxidative stress are related to dietary niacin intake among healthy middle-aged and older adults

We tested the hypothesis that vascular endothelial function and oxidative stress are related to dietary niacin intake among healthy middle-aged and older adults. In 127 men and women aged 48-77 yr, brachial artery flow-mediated dilation (FMD) was positively related to dietary niacin intake [%change (Δ): r = 0.20, P < 0.05; mmΔ: r = 0.25, P < 0.01]. In subjects with above-average dietary niacin intake (≥ 22 mg/day, NHANES III), FMD was 25% greater than in subjects with below-average intake (P < 0.05). Stepwise linear regression revealed that dietary niacin intake (above vs. below average) was an independent predictor of FMD (%Δ: β = 1.8; mmΔ: β = 0.05, both P < 0.05). Plasma oxidized low-density lipoprotein, a marker of systemic oxidative stress, was inversely related to niacin intake (r = -0.23, P < 0.05) and was lower in subjects with above- vs. below-average niacin intake (48 ± 2 vs. 57 ± 2 mg/dl, P < 0.01). Intravenous infusion of the antioxidant vitamin C improved brachial FMD in subjects with below-average niacin intake (P < 0.001, n = 33), but not above-average (P > 0.05, n = 20). In endothelial cells sampled from the brachial artery of a subgroup, dietary niacin intake was inversely related to nitrotyrosine, a marker of peroxynitrite-mediated oxidative damage (r = -0.30, P < 0.05, n = 55), and expression of the prooxidant enzyme, NADPH oxidase (r = -0.44, P < 0.01, n = 37), and these markers were lower in subjects with above- vs. below-average niacin intake [nitrotyrosine: 0.39 ± 0.05 vs. 0.56 ± 0.07; NADPH oxidase: 0.38 ± 0.05 vs. 0.53 ± 0.05 (ratio to human umbilical vein endothelial cell control), both P < 0.05]. Our findings support the hypothesis that higher dietary niacin intake is associated with greater vascular endothelial function related to lower systemic and vascular oxidative stress among healthy middle-aged and older adults.

Lp-PLA2 Inhibitors for the Reduction of Cardiovascular Events

Evidence suggests that inflammation plays a central role in the pathogenesis of atherosclerosis (Libby, Nature 420:868–874, 2002). Inflammation is a physiologic process with highly regulated and often redundant mechanisms to balance pro-inflammatory and anti-inflammatory responses. The complexity of these networks has made it challenging to identify those specific pathways or key enzymes that contribute directly to atherogenesis and could act as a valuable therapeutic target. Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a member of the phospholipase A₂ family of enzymes and is believed to contribute to atherosclerotic plaque progression and instability by promoting inflammation. A large number of epidemiologic studies have demonstrated that elevated levels of Lp-PLA₂ are associated with an increased risk of cardiovascular events across diverse patient populations, independent of established risk factors including low-density lipoprotein cholesterol. Further, a growing number of preclinical and genetic studies support a causal role for Lp-PLA₂ in atherosclerosis. The development of a novel therapeutic agent that directly inhibits the Lp-PLA₂ enzyme has provided a unique opportunity to directly test the hypothesis that inhibition of this inflammatory enzyme will translate into improved clinical outcomes. In this article, we will review the evidence to support the notion that Lp-PLA₂ is causally implicated in the pathobiology of atherogenesis and discuss the potential utility of inhibiting this enzyme as a therapeutic target.

High density lipoprotein: a therapeutic target in type 2 diabetes

High density lipoproteins (HDLs) have a number of properties that have the potential to inhibit the development of atherosclerosis and thus reduce the risk of having a cardiovascular event. These protective effects of HDLs may be reduced in patients with type 2 diabetes, a condition in which the concentration of HDL cholesterol is frequently low. In addition to their potential cardioprotective properties, HDLs also increase the uptake of glucose by skeletal muscle and stimulate the synthesis and secretion of insulin from pancreatic β cells and may thus have a beneficial effect on glycemic control. This raises the possibility that a low HDL concentration in type 2 diabetes may contribute to a worsening of diabetic control. Thus, there is a double case for targeting HDLs in patients with type 2 diabetes: to reduce cardiovascular risk and also to improve glycemic control. Approaches to raising HDL levels include lifestyle factors such as weight reduction, increased physical activity and stopping smoking. There is an ongoing search for HDL-raising drugs as agents to use in patients with type 2 diabetes in whom the HDL level remains low despite lifestyle interventions.

Effect of hypolipidemic treatment on emerging risk factors in mixed dyslipidemia: a randomized pilot trial

BACKGROUND

The effects of different hypolipidemic treatment strategies on emerging atherosclerosis risk factors remain unknown.

MATERIALS AND METHODS

This is a prespecified analysis of a prospective, randomized, open-label, blinded end point (PROBE) study (ClinicalTrials.gov identifier: NCT01010516). Patients (n = 100) with mixed dyslipidaemia on a standard statin dose who had not achieved lipid targets were randomized to switch to the highest dose of rosuvastatin (40 mg/day) or to add-on-statin extended release nicotinic acid (ER-NA)/laropiprant (LRPT) or to add-on-statin micronized fenofibrate for a total of 3 months.

RESULTS

Following 3 months of treatment, low-density lipoprotein (LDL) particle size increased equally in all groups. Similarly, all treatments were associated with comparable small dense LDL cholesterol reduction. Apolipoprotein B levels decreased by 15%, 7% and 4% in the rosuvastatin, add-on ER-NA/LRPT and add-on fenofibrate group, respectively (P < 0.01 for all compared with baseline, P < 0.01 for all comparisons between groups). Only add-on ER-NA/LRPT was associated with lipoprotein (a) reduction (26%, P < 0.01 compared with baseline). Rosuvastatin monotherapy and add-on ER-NA/LRPT groups were associated with 56% and 24% reduction in high-sensitivity C-reactive protein levels (hsCRP), respectively (P < 0.01 compared with baseline), while add-on fenofibrate was not associated with changes in hsCRP concentration. Lipoprotein-associated phospholipase A2 (Lp-PLA2) activity decreased similarly in both rosuvastatin and add-on fenofibrate groups, while add-on ER-NA/LRPT was associated with a more pronounced Lp-PLA2 activity reduction. ER-NA/LRPT was associated with more side effects compared with rosuvastatin and add-on fenofibrate.

CONCLUSIONS

Add-on ER-NA/LRPT followed by switch to the highest dose rosuvastatin were associated with more pronounced beneficial modifications in emerging cardiovascular risk factors compared with add-on fenofibrate in patients with mixed dyslipidaemia.

Cardioprotective functions of HDLs

Multiple human population studies have established the concentration of high density lipoprotein (HDL) cholesterol as an independent, inverse predictor of the risk of having a cardiovascular event. Furthermore, HDLs have several well-documented functions with the potential to protect against cardiovascular disease. These include an ability to promote the efflux of cholesterol from macrophages in the artery wall, inhibit the oxidative modification of low density lipoproteins (LDLs), inhibit vascular inflammation, inhibit thrombosis, promote endothelial repair, promote angiogenesis, enhance endothelial function, improve diabetic control, and inhibit hematopoietic stem cell proliferation. There are undoubtedly other beneficial functions of HDLs yet to be identified. The HDL fraction in human plasma is heterogeneous, consisting of several subpopulations of particles of varying size, density, and composition. The functions of the different HDL subpopulations remain largely unknown. Given that therapies that increase the concentration of HDL cholesterol have varying effects on the levels of specific HDL subpopulations, it is of great importance to understand how distribution of different HDL subpopulations contribute to the potentially cardioprotective functions of this lipoprotein fraction. This review summarizes current understanding of the relationship of HDL subpopulations to their cardioprotective properties and highlights the gaps in current knowledge regarding this important aspect of HDL biology.

Metabolic syndrome: clinical perspective for best practice

PURPOSE

To explore current studies on metabolic syndrome (MetS), including its complex pathophysiology and to describe the unique role of the advanced practice nurse including management and ethical decision making utilizing a case study to exemplify salient points.

DATA SOURCES

From original research articles extracted from nursing and medical databases.

CONCLUSIONS

MetS is a constellation of characteristics that increases the risk for the development of diabetes and cardiovascular disease. The pathophysiology of MetS is not completely understood, but is thought to involve a complex interaction between the environment, genetic susceptibility, insulin resistance, and abnormal adipose tissue function.

IMPLICATIONS FOR PRACTICE

The role of the advanced practice nurse is appropriate for early intervention and counseling of patients with MetS and those who are at risk, as well as addressing the ethical challenges that accompany their care.

The current state of niacin in cardiovascular disease prevention: a systematic review and meta-regression

OBJECTIVES

This study sought to assess the efficacy of niacin for reducing cardiovascular disease (CVD) events, as indicated by the aggregate body of clinical trial evidence including data from the recently published AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides: Impact on Global Health Outcomes) trial.

BACKGROUND

Previously available randomized clinical trial data assessing the clinical efficacy of niacin has been challenged by results from AIM-HIGH, which failed to demonstrate a reduction in CVD event incidence in patients with established CVD treated with niacin as an adjunct to intensive simvastatin therapy.

METHODS

Clinical trials of niacin, alone or combined with other lipid-altering therapy, were identified via MEDLINE. Odds ratios (ORs) for CVD endpoints were calculated with a random-effects meta-analyses. Meta-regression modeled the relationship of differences in on-treatment high-density lipoprotein cholesterol with the magnitude of effect of niacin on CVD events.

RESULTS

Eleven eligible trials including 9,959 subjects were identified. Niacin use was associated with a significant reduction in the composite endpoints of any CVD event (OR: 0.66; 95% confidence interval [CI]: 0.49 to 0.89; p = 0.007) and major coronary heart disease event (OR: 0.75; 95% CI: 0.59 to 0.96; p = 0.02). No significant association was observed between niacin therapy and stroke incidence (OR: 0.88; 95% CI: 0.5 to 1.54; p = 0.65). The magnitude of on-treatment high-density lipoprotein cholesterol difference between treatment arms was not significantly associated with the magnitude of the effect of niacin on outcomes.

CONCLUSIONS

The consensus perspective derived from available clinical data supports that niacin reduces CVD events and, further, that this may occur through a mechanism not reflected by changes in high-density lipoprotein cholesterol concentration.

Niacin: another look at an underutilized lipid-lowering medication

Niacin, or water-soluble vitamin B(3), when given at pharmacologic doses, is a powerful lipid-altering agent. This drug, which lowers the levels of atherogenic, apolipoprotein-B-containing lipoproteins, is one of few medications that can raise the levels of atheroprotective HDL cholesterol. Niacin also has beneficial effects on other cardiovascular risk factors, including lipoprotein(a), C-reactive protein, platelet-activating factor acetylhydrolase, plasminogen activator inhibitor 1 and fibrinogen. Many clinical trials have confirmed the lipid effects of niacin treatment; however, its effects on cardiovascular outcomes have been called into question owing to the AIM-HIGH trial, which showed no benefit of niacin therapy on cardiovascular endpoints. Furthermore, use of niacin has historically been limited by tolerability issues. In addition to flushing, worsened hyperglycaemia among patients with diabetes mellitus has also been a concern with niacin therapy. This article reviews the utility of niacin including its mechanism of action, clinical trial data regarding cardiovascular outcomes, adverse effect profile and strategies to address these effects and improve compliance.

Nicotinic acid inhibits hepatic APOA gene expression: studies in humans and in transgenic mice

Elevated plasma lipoprotein(a) (LPA) levels are recognized as an independent risk factor for cardiovascular diseases. Our knowledge on LPA metabolism is incomplete, which makes it difficult to develop LPA-lowering medications. Nicotinic acid (NA) is the main drug recommended for the treatment of patients with increased plasma LPA concentrations. The mechanism of NA in lowering LPA is virtually unknown. To study this mechanism, we treated transgenic (tg) APOA mice with NA and measured plasma APOA and hepatic mRNA levels. In addition, mouse and human primary hepatocytes were incubated with NA, and the expression of APOA was followed. Feeding 1% NA reduced plasma APOA and hepatic expression of APOA in tg-APOA mice. Experiments with cultured human and mouse primary hepatocytes in addition to reporter assays performed in HepG2 cells revealed that NA suppresses APOA transcription. The region between -1446 and -857 of the human APOA promoter harboring several cAMP response element binding sites conferred the negative effect of NA. In accordance, cAMP stimulated APOA transcription, and NA reduced hepatic cAMP levels. It is suggested that cAMP signaling might be involved in reducing APOA transcription, which leads to the lowering of plasma LPA.

Predicting the Risk of Cardiovascular Disease

Although an atherogenic lipoprotein phenotype has been well recognized as an important predictor of cardiovascular disease, recent studies have demonstrated a number of additional lipid-related markers as emerging biomarkers to identify patients at risk for future coronary heart disease. Among them, lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), seems to be a promising candidate that might be added to the clinical armamentarium for improved prediction of cardiovascular disease in the future. Of particular note, Lp-PLA(2) is the only enzyme that cleaves oxidized low-density lipoprotein (oxLDL) in the subendothelial space, with further generation of proinflammatory mediators such as lysophosphatidylcholine (LysoPC) and oxidized fatty acid (oxFA), thereby probably linking two important features of atherogenesis, namely oxidation of LDL and local inflammatory processes within the atherosclerotic plaque. This overview aims to summarize our current knowledge based on observations from recent experimental and clinical studies. Emphasis has been put on potential pathophysiological mechanisms of action and on the clinical relevance of Lp-PLA(2) in a wide variety of clinical settings, including apparently healthy individuals, patients with stable angina or acute coronary syndromes, after myocardial infarction, and with subclinical disease. Although a growing body of evidence from epidemiological and clinical studies suggests that Lp-PLA(2) may represent an independent and clinically relevant long-term risk marker for coronary heart disease and, probably, also for stroke, the role of this enzyme in the setting of the acute coronary syndrome remains to be established.

Effects of prescription niacin and omega-3 fatty acids on lipids and vascular function in metabolic syndrome: a randomized controlled trial

The metabolic syndrome includes both dyslipidemia and impaired vascular function. Because extended-release niacin (ERN) and prescription omega-3 acid ethyl-esters (P-OM3) independently improve these characteristics, we tested their effects in combination. Sixty metabolic syndrome subjects were randomized to 16 weeks of treatment on dual placebo, P-OM3 (4g/day), ERN (2 g/day), or combination in a double-blind trial. Lipoprotein subfractions and vascular endpoints were measured and tested using ANCOVA. ERN increased HDL cholesterol by 5.4 mg/dl from baseline (P = 0.04), decreased triglycerides (TG) by 39 mg/dl (−21%, P = 0.003), and decreased the augmentation index, which is a measure of vascular stiffness, by 3.5 units (P = 0.04). P-OM3 reduced TG by 26 mg/dl (−13%, P = 0.04). Combination treatment increased HDL cholesterol by 7.8 mg/dl (P = 002) and decreased TG by 72 mg/dl (−34%) but there was no improvement in vascular stiffness. Detailed analysis of lipoprotein subfractions revealed increased large, bouyant HDL₂ (3.3 mg/dl; P = 0.002) and decreased VLDL₁₊₂ (−32%; P < 0.0001), among subjects treated with combination therapy, that were not present with either therapy alone. ERN and P-OM3 alone improved characteristics of metabolic syndrome; however, whereas subjects on combination therapy did not have improved vascular stiffness, TG and HDL levels improved as did certain lipoprotein subfractions.

Niacin in cardiovascular disease: recent preclinical and clinical developments

Niacin has been used for more than 50 years in the treatment of cardiovascular disease, although its use has largely been superseded by better-tolerated lipid-modulating interventions. There has been a renewed interest in the HDL-cholesterol raising properties of niacin, with the appreciation that substantial cardiovascular risk remains despite effective treatment of LDL-cholesterol. This coincides with increasing evidence that the complex functional properties of HDL are not well reflected by measurement of HDL-cholesterol alone. In addition to favorable actions on lipoproteins, it is becoming apparent that niacin may also possess lipoprotein independent or pleiotropic effects including the inhibition of inflammatory pathways mediated by its receptor GPR109A, which is expressed by adipocytes and some leukocytes. In this article we consider emerging and prior clinical trial data relating to niacin. We review recent data in respect of mechanisms of action on lipoproteins, which remain complex and incompletely understood. We discuss the recent reports of anti-inflammatory effects of niacin in adipocytes and through bone marrow derived cells and vascular endothelium. These novel observations come at an interesting time, with current imaging and outcome studies leaving outstanding questions on niacin efficacy in statin-treated patients.

Niacin extended-release therapy in phase III clinical trials is associated with relatively low rates of drug discontinuation due to flushing and treatment-related adverse events: a pooled analysis

BACKGROUND AND OBJECTIVE

Niacin is a highly effective agent for increasing low high-density lipoprotein cholesterol (HDL-C) levels. It also has beneficial effects on key pro-atherogenic lipoprotein parameters. However, the side effect of flushing can challenge patient adherence to treatment. In this study, we pooled safety data from available trials of at least 16 weeks' duration to evaluate the impact of flushing on patient adherence to niacin extended-release (NER) therapy.

METHODS

Data were pooled from eight NER studies (administered as NER with a maximum dosage of 1000, 1500, and 2000 mg/day, either as monotherapy or in combination with simvastatin 20 or 40 mg/day [NER/S], or lovastatin 20 or 40 mg/day [NER/L]) to evaluate rates of study discontinuation due to flushing or any treatment-related adverse events.

RESULTS

While 66.6% of patients experienced flushing, only 5.2% of patients discontinued treatment due to flushing. Of the total number of patients treated with NER (n = 307), NER/S (n = 912), or NER/L (n = 928), 34 (11%), 105 (11%), and 127 (14%) patients discontinued due to any treatment-related adverse event, respectively, while 14 (5%), 43 (5%), and 55 (6%) discontinued due to flushing. Discontinuation for flushing did not differ with regard to maximum dose, or to the presence or type of statin combined with NER.

CONCLUSION

Although flushing was common with NER treatment, discontinuation due to flushing occurred in only 5-6% of patients in this pooled analysis. This could be due to several factors, including the fact that all patients in the NER trials were educated about flushing and its management. Translation of methodology employed in these trials into clinical practice may improve long-term adherence to NER therapy, which would enhance the therapeutic benefit of NER for reducing cardiovascular risk.

Clinical implications of discordance between low-density lipoprotein cholesterol and particle number

BACKGROUND

The amount of cholesterol per low-density lipoprotein (LDL) particle is variable and related in part to particle size, with smaller particles carrying less cholesterol. This variability causes concentrations of LDL cholesterol (LDL-C) and LDL particles (LDL-P) to be discordant in many individuals.

METHODS

LDL-P measured by nuclear magnetic resonance spectroscopy, calculated LDL-C, and carotid intima-media thickness (IMT) were assessed at baseline in the Multi-Ethnic Study of Atherosclerosis, a community-based cohort of 6814 persons free of clinical cardiovascular disease (CVD) at entry and followed for CVD events (n = 319 during 5.5-year follow-up). Discordance, defined as values of LDL-P and LDL-C differing by ≥ 12 percentile units to give equal-sized concordant and discordant subgroups, was related to CVD events and to carotid IMT in models predicting outcomes for a 1 SD difference in LDL-C or LDL-P, adjusted for age, gender, and race.

RESULTS

LDL-C and LDL-P were associated with incident CVD overall: hazard ratios (HR 1.20, 95% CI [CI] 1.08-1.34; and 1.32, 95% CI 1.19-1.47, respectively, but for those with discordant levels, only LDL-P was associated with incident CVD (HR 1.45, 95% CI 1.19-1.78; LDL-C HR 1.07, 95% CI 0.88-1.30). IMT also tracked with LDL-P rather than LDL-C, ie, adjusted mean IMT of 958, 932, and 917 microm in the LDL-P > LDL-C discordant, concordant, and LDL-P < LDL-C discordant subgroups, respectively, with the difference persisting after adjustment for LDL-C (P = .002) but not LDL-P (P = .60).

CONCLUSIONS

For individuals with discordant LDL-C and LDL-P levels, the LDL-attributable atherosclerotic risk is better indicated by LDL-P.