Niacin therapy in atherosclerosis

Recent advances in niacin and lipid metabolism

PURPOSE OF REVIEW

This review focuses on the current understanding of the physiological mechanisms of action of niacin on lipid metabolism and atherosclerosis.

RECENT FINDINGS

Emerging findings indicate that niacin decreases hepatic triglyceride synthesis and subsequent VLDL/LDL secretion by directly and noncompetitively inhibiting hepatocyte diacylglycerol acyltransferase 2. Recent studies in mice lacking niacin receptor GPR109A and human clinical trials with GPR109A agonists disproved the long believed hypothesis of adipocyte triglyceride lipolysis as the mechanism for niacin's effect on serum lipids. Niacin, through inhibiting hepatocyte surface expression of β-chain ATP synthase, inhibits the removal of HDL-apolipoprotein (apo) AI resulting in increased apoAI-containing HDL particles. Additional recent findings suggest that niacin by increasing hepatic ATP-binding cassette transporter A1-mediated apoAI lipidation increases HDL biogenesis, thus stabilizing circulation of newly secreted apoAI. New concepts have also emerged on lipid-independent actions of niacin on vascular endothelial oxidative and inflammatory events, myeloperoxidase release from neutrophils and its impact on HDL function, and GPR109A-mediated macrophage inflammatory events involved in atherosclerosis.

SUMMARY

Recent advances have provided physiological mechanisms of action of niacin on lipid metabolism and atherosclerosis. Better understanding of niacin's actions on multiple tissues and targets may be helpful in designing combination therapy and new treatment strategies for atherosclerosis.

Protection of nicotinic acid against oxidative stress-induced cell death in hepatocytes contributes to its beneficial effect on alcohol-induced liver injury in mice

Oxidative stress plays a pathological role in the development of alcoholic liver disease. In this study, we investigated the effects of nicotinic acid (NA) supplementation on H2O2-induced cell death in hepatocytes and alcohol-induced liver injury in mice. Hepatocytes were exposed to H2O2 (0-0.4 mM) for 16 h after a 2-h pretreatment with NA (0-100 μM). Cell viability, intracellular glutathione and total NAD contents were determined. In animal experiments, male C57BL/6 mice were exposed to Lieber-De Carli liquid diet [+/- ethanol with/without NA supplementation (0.5%, w/v) for 4 weeks]. Nicotinic acid phosphoribosyltransferase (NaPRT) is the first enzyme participated in the NA metabolism, converting NA to nicotinic acid mononucleotide (NaMN). In NaPRT-expressing Hep3B cells, H2O2-induced cell death was attenuated by NA, whereas in NaPRT-lost HepG2 cells, only NaMN conferred protective effect, suggesting that NA metabolism is required for its protective action against H2O2. In Hep3B cells, NA supplementation prevented H2O2-inudced declines in intracellular total NAD and GSH/GSSG ratios. Further mechanistic investigations revealed that conservation of Akt activity contributed to NA's protective effect against H2O2-inudced cell death. In alcohol-fed mice, NA supplementation attenuated liver injury induced by chronic alcohol exposure, which was associated with alleviated hepatic lipid peroxidation and increased liver GSH concentrations. In conclusion, our findings indicate that exogenous NA supplementation may be an ideal choice for the treatment of liver diseases that involve oxidative stress.

Herbal, vitamin, and mineral supplement use in patients enrolled in a cardiac rehabilitation program

PURPOSE

The use of complementary and alternative medicine is common and continues to rise each year, both in the general population and among those with cardiovascular disease. While some supplements may incur risk, particularly when used concomitantly with cardiovascular medications, others have proven benefits. However, supplements such as antioxidants and many herbs can have significant interactions with cardiovascular medications. This study aimed to identify the percentage of patients enrolled in a cardiac rehabilitation program taking herbal, vitamin, and mineral supplements.

METHODS

Electronic and paper charts of 235 patients enrolled in a phase 3 cardiac rehabilitation program were reviewed. Their demographics, medical history, and medications were stratified in an Excel chart, using a large matrix from which data were imported into Matlab for analysis. Custom Matlab programs were created and compiled to determine variables of interest, including percentages of patients with a specific medical condition taking certain supplements.

RESULTS

Sixty-seven percent of patients enrolled in the cardiac rehabilitation program were taking vitamins, with or without minerals (67%, 158 of 235). Multivitamin is the most common form of supplement (51%, 119 of 235), followed by fish oil/omega-3 polyunsaturated fatty acids (27%, 64 of 235).

CONCLUSION

The majority of patients in a phase 3 cardiac rehabilitation program are taking some form of herbal, vitamin, or mineral supplement. Given frequent, complicated patient medication regimens, it is important to educate patients on the potential benefits as well as lack of evidence and possible dangers of supplements.

Effects of low-dose niacin on dyslipidemia and serum phosphorus in patients with chronic kidney disease

BACKGROUND

Niacin supplementation improves dyslipidemia and lowers serum phosphorus levels in patients with chronic kidney disease (CKD). We evaluated whether low-dose niacin supplementation can improve dyslipidemia, lower serum phosphorus levels, and be administered with a low frequency of adverse effects in patients with CKD.

METHODS

We retrospectively analyzed the clinical records of patients with CKD who had taken niacin from January 2009 to June 2011. We excluded patients with CKD stage 1 and 5. We then enrolled 31 patients with CKD who had taken niacin at a fixed dose of 500 mg/day for 6 months. We also randomly selected 30 patients with CKD who had been taking statin for 9 months as a control group.

RESULTS

Among the 34 patients with CKD who were prescribed niacin, five (14%) complained of adverse effects, and three (8%) discontinued niacin. The proportion of patients in the niacin group who had been taking a statin or omega-3 fatty acids was 67.7% and 48.8%, respectively. In the niacin group, high-density lipoprotein cholesterol level was significantly increased and triglyceride level was significantly decreased at 12 and 24 weeks compared with baseline levels (P<0.05). In the niacin group, phosphorous level (P<0.05) was significantly decreased, and glomerular filtration rate (GFR) was significantly increased (P<0.05) at 24 weeks compared with baseline values.

CONCLUSION

Low-dose niacin had a low frequency of adverse effects and also improved dyslipidemia, lowered serum phosphorus level, and increased GFR in patients with CKD. Further studies are needed to evaluate the long-term effects of low-dose niacin for renal progression of CKD.

Attenuation of niacin-induced prostaglandin D(2) generation by omega-3 fatty acids in THP-1 macrophages and Langerhans dendritic cells

Niacin, also known as nicotinic acid, is an organic compound that has several cardio-beneficial effects. However, its use is limited due to the induction of a variable flushing response in most individuals. Flushing occurs from a niacin receptor mediated generation of prostaglandins from arachidonic acid metabolism. This study examined the ability of docosahexaenoic acid, eicosapentaenoic acid, and omega-3 polyunsaturated fatty acids (PUFAs), to attenuate niacin-induced prostaglandins in THP-1 macrophages. Niacin induced both PGD₂ and PGE₂ generation in a dose-dependent manner. Niacin also caused an increase in cytosolic calcium and activation of cytosolic phospholipase A₂. The increase in PGD₂ and PGE₂ was reduced by both docosahexaenoic acid and eicosapentaenoic acid, but not by oleic acid. Omega-3 PUFAs efficiently incorporated into cellular phospholipids at the expense of arachidonic acid, whereas oleic acid incorporated to a higher extent but had no effect on arachidonic acid levels. Omega-3 PUFAs also reduced surface expression of GPR109A, a human niacin receptor. Furthermore, omega-3 PUFAs also inhibited the niacin-induced increase in cytosolic calcium. Niacin and/or omega-3 PUFAs minimally affected cyclooxygenase-1 activity and had no effect on cyclooxygenase -2 activity. The effects of niacin on PGD₂ generation were further confirmed using Langerhans dendritic cells. Results of the present study indicate that omega-3 PUFAs reduced niacin-induced prostaglandins formation by diminishing the availability of their substrate, as well as reducing the surface expression of niacin receptors. In conclusion, this study suggests that the regular use of omega-3 PUFAs along with niacin can potentially reduce the niacin-induced flushing response in sensitive patients.

Niacin increases HDL biogenesis by enhancing DR4-dependent transcription of ABCA1 and lipidation of apolipoprotein A-I in HepG2 cells

The lipidation of apoA-I in liver greatly influences HDL biogenesis and plasma HDL levels by stabilizing the secreted apoA-I. Niacin is the most effective lipid-regulating agent clinically available to raise HDL. This study was undertaken to identify regulatory mechanisms of niacin action in hepatic lipidation of apoA-I, a critical event involved in HDL biogenesis. In cultured human hepatocytes (HepG2), niacin increased: association of apoA-I with phospholipids and cholesterol by 46% and 23% respectively, formation of lipid-poor single apoA-I molecule-containing particles up to ~2.4-fold, and pre β 1 and α migrating HDL particles. Niacin dose-dependently stimulated the cell efflux of phospholipid and cholesterol and increased transcription of ABCA1 gene and ABCA1 protein. Mutated DR4, a binding site for nuclear factor liver X receptor alpha (LXR α ) in the ABCA1 promoter, abolished niacin stimulatory effect. Further, knocking down LXR α or ABCA1 by RNA interference eliminated niacin-stimulated apoA-I lipidation. Niacin treatment did not change apoA-I gene expression. The present data indicate that niacin increases apoA-I lipidation by enhancing lipid efflux through a DR4-dependent transcription of ABCA1 gene in HepG2 cells. A stimulatory role of niacin in early hepatic formation of HDL particles suggests a new mechanism that contributes to niacin action to increase the stability of newly synthesized circulating HDL.

Emerging role of mast cells and macrophages in cardiovascular and metabolic diseases

Mast cells are essential in allergic immune responses. Recent discoveries have revealed their direct participation in cardiovascular diseases and metabolic disorders. Although more sophisticated mechanisms are still unknown, data from animal studies suggest that mast cells act similarly to macrophages and other inflammatory cells and contribute to human diseases through cell-cell interactions and the release of proinflammatory cytokines, chemokines, and proteases to induce inflammatory cell recruitment, cell apoptosis, angiogenesis, and matrix protein remodeling. Reduced cardiovascular complications and improved metabolic symptoms in animals receiving over-the-counter antiallergy medications that stabilize mast cells open another era of mast cell biology and bring new hope to human patients suffering from these conditions.

The effects of statin and niacin on plaque stability, plaque regression, inflammation and oxidative stress in patients with mild to moderate coronary artery stenosis

Background and Objectives

The aim of this study was to compare the effects of a combination of niacin and simvastatin to simvastatin alone, on plaque regression and inflammatory makers.

Subjects and Methods

The study had a prospective, randomized design. Subjects were patients with intermediate coronary artery stenosis. A total of 28 patients received a combination of niacin 1,000 mg plus simvastatin 40 mg (N+S group, n=14); the other group received simvastatin 40 mg alone (S group, n=14). All patients had a baseline and a 9-month follow-up coronary angiogram and an intravascular ultrasound procedure. Parameters such as normalized total atheroma volume (nTAV) and percent atheroma volume (PAV) were analyzed before and after treatment as were inflammatory markers such as high sensitivity C-reactive protein (hs-CRP), Matrix me-talloproteinase-9 (MMP-9) and soluble CD40 ligand (sCD40L).

Results

There was no difference in baseline characteristics between the two groups. The nTAV and PAV in the N+S group before and after treatment were not different than those in the S group. But the degree of changes (delta) in nTAV in the N+S group was greater than that in the S group (-21.6±10.68 vs. 5.25±42.19, respectively, p=0.024). Also, the change in PAV in the NS group was higher than that in the S group (-1.2±2.5 vs. -0.6±5, respectively, p=0.047. Changes in hs-CRP, MMP-9, and sCD40L in the NS group were significantly greater than those of the S group (-0.71±1.25, 73.5±64.9, -1,970±1,925 vs. -0.32±0.96, 62.5±30.6, -1,673±2,628, respectively).

Conclusion

The combination of niacin plus simvastatin decreases coronary plaque volume and attenuates the inflammatory response in patients with intermediate coronary artery stenosis.

Adsorption of nicotinic acid on the surface of nanosized hydroxyapatite and structurally modified hydroxyapatite

In the present paper, hydroxyapatite and structurally modified hydroxyapatite were investigated to establish the best material for nicotinic acid adsorption. Structurally modified hydroxyapatite wa prepared by adding sodium silicate in the reaction medium. The influence of silica concentration, presence of small amounts of metal ions, temperature and initial concentrations of nicotinic acid solutions on the adsorption capacity, were studied. Results indicated that structurally modified hydroxyapatite doped with copper adsorbed the highest amount of nicotinic acid. For this material the adsorption capacity was 0.232 mg nicotinic acid / g material, at an initial concentration of 10−4 M nicotinic acid. For all types of materials, best results were obtained at 15°C. The amount of nicotinic acid adsorbed increases with the decrease in temperature and with the increase in the initial concentration of nicotinic acid. Adsorption kinetics data were modeled using pseudo-first and pseudo-second order models while the interference due to diffusion was analyzed with intraparticle diffusion model. The results indicate that pseudo-second order model best describes the adsorption kinetics data, indicating the formation of chemical bonding.

The materials used in this study were characterized by the following methods: IR, Coulter Counter analyzer, Scanning Electron Microscope and BET

Combination treatment with low-dose Niaspan and tissue plasminogen activator provides neuroprotection after embolic stroke in rats

INTRODUCTION

Niaspan, an extended-release formulation of niacin (vitamin B3), has been widely used to increase high density lipoprotein (HDL) cholesterol and to prevent cardiovascular diseases and stroke. We have previously demonstrated that Niaspan (40 mg/kg) administered at 2h after stroke induces neuroprotection, while low dose Niaspan (20mg/kg) does not reduce infarct volume. Tissue plasminogen activator (tPA) is an effective therapy for acute stroke, but its use remains limited by a narrow therapeutic window. We have previously demonstrated that intravenous administration of tPA 4h after stroke in rats does not reduce infarct volume. In this study, we tested whether combination treatment with low-dose Niaspan (20mg/kg) and tPA administered 4h after embolic stroke in a rat model reduces infarct volume and provides neuroprotection.

METHODS

Adult male Wistar rats were subjected to embolic middle cerebral artery occlusion (MCAo) and treated with low-dose Niaspan (20mg/kg) alone (n = 7), tPA (10mg/kg) alone (n = 7), combination of low-dose Niaspan and tPA (n = 7), or saline control (n = 9), 4h after stroke. A battery of functional outcome tests was performed. Rats were sacrificed at 7 days after MCAo and lesion volumes were measured. To investigate the underlying mechanism of combination treatment neuroprotective effect, deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), cleaved caspase-3, tumor necrosis factor alpha (TNF-alpha), and toll-like receptor 4 (TLR-4) immunostaining were performed.

RESULTS

Combination treatment with low-dose Niaspan and tPA significantly improved functional outcome compared to the saline control group (p<0.05), while treatment with Niaspan or tPA alone did not significantly improve functional outcome compared to saline control group. Additionally, combination treatment significantly reduced infarct volume compared to saline control group (p = 0.006) and infarct volume was significantly correlated with functional outcome (p = 0.0008; r = 0.63). Monotherapy with Niaspan or tPA did not significantly decrease infarct volume compared to saline control group. Combination treatment reduced apoptosis as measured by significant reduction in the number of TUNEL-positive cells and cleaved caspase-3 expression in the ischemic brain compared to saline control group (p<0.05). Combination treatment also significantly reduced the expression of TNF-alpha and TLR-4 in the ischemic brain compared to Niaspan, tPA and saline treatment groups (p<0.05). A significant interaction between Niaspan and tPA on the TNF-alpha expression was detected (p<0.05), indicating a synergy effect in the combination treatment group.

CONCLUSION

Treatment of stroke with combination of low-dose Niaspan and tPA at 4h after embolic stroke reduces infarct volume, improves neurological outcome and provides neuroprotection. The neuroprotective effects of combination treatment were associated with reduction of apoptosis and attenuation of TNF-alpha and TLR-4 expression.

Association between extended-release niacin treatment and glycemic control in patients with type 2 diabetes mellitus: analysis of an administrative-claims database

The aim of the study was to evaluate trends in antihyperglycemic agents (AHAs) use in patients with type 2 diabetes mellitus (T2DM) newly initiating extended-release niacin (ERN) compared with other lipid-modifying therapy (LMT). United States administrative-claims data identified adults with T2DM on AHAs who received a new prescription for ERN or another LMT between January 2001 and June 2003 (index date), and these adults were followed for 12 months. Inclusion criteria were (1) stable T2DM as defined by International Classification of Diseases, Ninth Revision, codes and also receiving at least 2 AHA prescriptions 12 to 24 months before initiating ERN or LMT treatment and (2) at least 2 prescriptions within 12 months before the onset of ERN or LMT. Trends in AHA prescriptions 12 months before (baseline) and after (follow-up) index date were defined as (1) no change (ie, stable T2DM), (2) increased (ie, worsening T2DM), or (3) reduced (ie, improved T2DM). Among 3799 patients with T2DM, 392 (10.3%) were treated with ERN and 3407 (89.7%) were treated with other LMT. In the ERN cohort, 82.1% of patients experienced no change in AHA prescriptions between baseline and follow-up compared with 79.4% of patients in the LMT cohort (P = .20); 13% of the ERN cohort and 16% of the LMT cohort (P = .17) experienced a dose increase or the addition of another AHA; and 5% of both cohorts were prescribed fewer AHAs or switched to a lower dose (P = .92). Treatment with ERN (vs other types of LMT) did not significantly increase AHA use, implying that T2DM status did not worsen in this cohort.

Diffuse macular edema in niacin-induced maculopathy may resolve with dosage decrease

PURPOSE

To report on a patient with niacin-induced cystic maculopathy that resolved with dosage decrease, not discontinuation, of niacin therapy for dyslipidemia.

METHODS

Retrospective case report. The patient was being followed for vision changes, but his niacin therapy was managed elsewhere.

RESULTS

Results of the decrease in niacin dosage show clear evidence (with optical coherence tomography) of resolution of retinal edema.

CONCLUSION

Our conclusion is that niacin's toxicity has a threshold, and dosage decrease below this threshold allows continuation of therapy at the lower dosage without clinically evident adverse effects on the retina.

International Union of Basic and Clinical Pharmacology. LXXXII: Nomenclature and Classification of Hydroxy-carboxylic Acid Receptors (GPR81, GPR109A, and GPR109B)

The G-protein-coupled receptors GPR81, GPR109A, and GPR109B share significant sequence homology and form a small group of receptors, each of which is encoded by clustered genes. In recent years, endogenous ligands for all three receptors have been described. These endogenous ligands have in common that they are hydroxy-carboxylic acid metabolites, and we therefore have proposed that this receptor family be named hydroxy-carboxylic acid (HCA) receptors. The HCA(1) receptor (GPR81) is activated by 2-hydroxy-propanoic acid (lactate), the HCA(2) receptor (GPR109A) is a receptor for the ketone body 3-hydroxy-butyric acid, and the HCA(3) receptor (GPR109B) is activated by the β-oxidation intermediate 3-hydroxy-octanoic acid. HCA(1) and HCA(2) receptors are found in most mammalian species, whereas the HCA(3) receptor is present only in higher primates. The three receptors have in common that they are expressed in adipocytes and are coupled to G(i)-type G-proteins mediating antilipolytic effects in fat cells. HCA(2) and HCA(3) receptors are also expressed in a variety of immune cells. HCA(2) is a receptor for the antidyslipidemic drug nicotinic acid (niacin) and related compounds, and there is an increasing number of synthetic ligands mainly targeted at HCA(2) and HCA(3) receptors. The aim of this article is to give an overview on the discovery and pharmacological characterization of HCAs, and to introduce an International Union of Basic and Clinical Pharmacology (IUPHAR)-recommended nomenclature. We will also discuss open questions regarding this receptor family as well as their physiological role and therapeutic potential.

Effects of nicotinic acid on endothelial cells and platelets

BACKGROUND

Interactions between platelets and endothelial cells under inflammatory conditions lead to an increased expression of various activity markers of atherosclerosis in the vessel wall. The purpose of this study was to investigate possible protective effects of nicotinic acid in an in vitro endothelial cell model.

METHODS

After a 24-hour incubation period with nicotinic acid (1 mmol/l), human umbilical vein endothelial cells were stimulated for 1 h with lipopolysaccharide and were then incubated in direct contact with activated platelets. Following this incubation, the expression of CD40L and CD62P on platelets and the expression of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, uPAR, and MT1-MMP on endothelial cells were measured by flow cytometry. Supernatants were analyzed by ELISA for soluble MCP-1 and MMP-1.

RESULTS

The increased expression of VCAM-1 on endothelial cells by proinflammatory stimulation with activated platelets was significantly reduced through preincubation with nicotinic acid (P<.05). Furthermore, platelets in direct contact with preincubated endothelial cells showed a significant reduction in their CD62P and CD40L expression when compared to platelets incubated with untreated endothelial cells (P<.05). Treatment with nicotinic acid did not have a significant effect on ICAM-1, uPAR, and MT1-MMP expression on endothelial cells. Levels of soluble MCP-1 and MMP-1 in supernatants were lower after preincubation with nicotinic acid.

CONCLUSION

Nicotinic acid inhibits platelet activation after platelets contacted nicotinic acid treated endothelial cells and inhibits VCAM-1 expression on human endothelial cells under inflammatory conditions. These findings suggest a possible pleiotropic therapeutic relevance of nicotinic acid in atherosclerosis.

Niacin attenuates lung inflammation and improves survival during sepsis by downregulating the nuclear factor-κB pathway

OBJECTIVES

To examine whether niacin attenuates lung inflammation and improves survival during sepsis and to determine whether the beneficial effects of niacin are associated with downregulation of the nuclear factor (NF)-κB pathway.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Male Sprague-Dawley rats (n = 119).

INTERVENTIONS

To induce endotoxemia in rats, lipopolysaccharide (Escherichia coli, O26:B6) at a dosage of 10 mg/kg was injected into a tail vein and 10 mins later, vehicle, a low dose of niacin (360 mg/kg), or a high dose of niacin (1180 mg/kg) was administered once through an orogastric tube, respectively.

MEASUREMENTS AND MAIN RESULTS

We observed the survival of the subjects for 72 hrs. At 6 hrs postlipopolysaccharide, we euthanized animals and measured cytoplasmic phosphorylated inhibitor κB-α and inhibitor κB-α expressions, nuclear NF-κB p65 expression, NF-κB p65 DNA-binding activity, tumor necrosis factor-α, and interleukin-6 gene expressions and histologic damages in lung tissues. We also measured nicotinamide adenine dinucleotide, reduced nicotinamide adenine dinucleotide phosphate, reduced glutathione, and malondialdehyde levels in lung tissues. High dose of niacin suppressed NF-κB activation and proinflammatory cytokine gene expressions in lung tissues, reduced histologic lung damages, and improved survival in endotoxemic rats. Furthermore, it increased nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, and glutathione levels and decreased malondialdehyde level in lung tissues.

CONCLUSIONS

High dose of niacin attenuated lung inflammation, reduced histologic lung damages, and improved survival during sepsis in rats. These therapeutic benefits were associated with downregulation of the NF-κB pathway.

Nicotinic acid inhibits progression of atherosclerosis in mice through its receptor GPR109A expressed by immune cells

Nicotinic acid (niacin) is a drug used to reduce the progression of atherosclerosis. Its antiatherosclerotic activity is believed to result from lipid-modifying effects, including its ability to decrease LDL cholesterol and increase HDL cholesterol levels in plasma. Here, we report that in a mouse model of atherosclerosis, we found that nicotinic acid inhibited disease progression under conditions that left total cholesterol and HDL cholesterol plasma levels unaffected. The antiatherosclerotic effect was not seen in mice lacking the receptor for nicotinic acid GPR109A. Surprisingly, transplantation of bone marrow from GPR109A-deficient mice into atherosclerosis-prone animals also abrogated the beneficial effect of nicotinic acid. We detected expression of GPR109A in macrophages in atherosclerotic plaques. In macrophages from WT mice, but not from GPR109A-deficient animals, nicotinic acid induced expression of the cholesterol transporter ABCG1 and promoted cholesterol efflux. Furthermore, activation of GPR109A by nicotinic acid inhibited MCP-1-induced recruitment of macrophages into the peritoneal cavity and impaired macrophage recruitment to atherosclerotic plaques. In contrast with current models, our data show that nicotinic acid can reduce the progression of atherosclerosis independently of its lipid-modifying effects through the activation of GPR109A on immune cells. We conclude therefore that GPR109A mediates antiinflammatory effects, which may be useful for treating atherosclerosis and other diseases.

Combined effects of niacin and chromium treatment on heart of hyperlipidemic rats

The present study was undertaken to investigate the effects of the combination of niacin and chromium(III)-chloride on heart glutathione (GSH), lipid peroxidation (LPO) levels, serum paraoxonase (PON), gamma-glutamyl transferase (GGT) activities and protein carbonyl contents (PCC) of hyperlipidemic rats. In this study, female Swiss albino rats were used. They were divided into four groups. The animals of the first group (group I) were fed with pellet chow. The rats (group II) were fed with a lipogenic diet consisting of 2% cholesterol, 0.5% cholic acid and 20% sunflower oil added to the pellet chow, and given 3% alcoholic water for 60 days. The rats (group III) were fed with the same lipogenic diet and treated by gavage technique with CrCl(3) 6H(2)O to a dose of 250 µg/kg and 100 mg/kg niacin for 45 days, 15 days after experimental animals were done hyperlipidemic. Group IV was fed with pellet chow and treated with 250 µg/kg CrCl(3) 6H(2)O and 100 mg/kg niacin for 45 days. On the 60th day, the heart tissue and blood samples were taken from animals. As a result, heart LPO, serum GGT activity and serum PCC were increased; serum PON activity and heart GSH levels were decreased in hyperlipidemic rats. Treatment with combined niacin and chromium reversed these effects. In conclusion, the combined treatment with niacin and chromium might induce a protective effect on heart tissue.

High-density lipoprotein (HDL) cholesterol: leveraging practice-based biobank cohorts to characterize clinical and genetic predictors of treatment outcome

Over the past decade, large multicenter trials have unequivocally demonstrated that decreasing low-density lipoprotein (LDL) cholesterol can reduce both primary and secondary cardiovascular events in patients at risk. However, even in the context of maximal LDL lowering, there remains considerable residual cardiovascular risk. Some of this risk can be attributed to variability in high-density lipoprotein (HDL) cholesterol. As such, there is tremendous interest in defining determinants of HDL homeostasis. Risk prediction models are being constructed based upon (1) clinical contributors, (2) known molecular determinants and (3) the genetic architecture underlying HDL cholesterol levels. To date, however, no single resource has combined these factors within the context of a practice-based data set. Recently, a number of academic medical centers have begun constructing DNA biobanks linked to secure encrypted versions of their respective electronic medical record. As these biobanks combine resources, the clinical community is in a position to characterize lipid-related treatment outcome on an unprecedented scale.

High-density lipoprotein induces proliferation and migration of human prostate androgen-independent cancer cells by an ABCA1-dependent mechanism

Androgen deprivation therapy for prostate cancer leads to a significant increase of high-density lipoprotein (HDL), which is generally viewed as beneficial, particularly for cardiovascular disease, but the effect of HDL on prostate cancer is unknown. In this study, we investigated the effect of HDL on prostate cancer cell proliferation, migration, intracellular cholesterol levels, and the role of cholesterol transporters, namely ABCA1, ABCG1, and SR-BI in these processes. HDL induced cell proliferation and migration of the androgen-independent PC-3 and DU145 cells by a mechanism involving extracellular signal-regulated kinase (ERK) 1/2 and Akt, but had no effect on the androgen-dependent LNCaP cell, which did not express ABCA1 unlike the other cell lines. Treatment with HDL did not significantly alter the cholesterol content of the cell lines. Knockdown of ABCA1 but not ABCG1 or SR-BI by small interfering RNA (siRNA) inhibited HDL-induced cell proliferation, migration, and ERK1/2 and Akt signal transduction in PC-3 cells. Moreover, after treatment of LNCaP cells with charcoal-stripped fetal bovine serum, ABCA1 was induced ∼10-fold, enabling HDL to induce ERK1/2 activation, whereas small interfering RNA knockdown of ABCA1 inhibited HDL-induced ERK1/2 activation. Simvastatin, which inhibited ABCA1 expression in PC-3 and DU145 cells, attenuated HDL-induced PC-3 and DU145 cell proliferation, migration, and ERK1/2 and Akt phosphorylation. In human prostate biopsy samples, ABCA1 mRNA expression was ∼2-fold higher in the androgen deprivation therapy group than in subjects with benign prostatic hyperplasia or pretreatment prostate cancer groups. In summary, these results suggest that HDL by an ABCA1-dependent mechanism can mediate signal transduction, leading to increased proliferation and migration of prostate cancer cells.

Nicotinic acid- and monomethyl fumarate-induced flushing involves GPR109A expressed by keratinocytes and COX-2-dependent prostanoid formation in mice

The antidyslipidemic drug nicotinic acid and the antipsoriatic drug monomethyl fumarate induce cutaneous flushing through activation of G protein-coupled receptor 109A (GPR109A). Flushing is a troublesome side effect of nicotinic acid, but may be a direct reflection of the wanted effects of monomethyl fumarate. Here we analyzed the mechanisms underlying GPR109A-mediated flushing and show that both Langerhans cells and keratinocytes express GPR109A in mice. Using cell ablation approaches and transgenic cell type-specific GPR109A expression in Gpr109a-/- mice, we have provided evidence that the early phase of flushing depends on GPR109A expressed on Langerhans cells, whereas the late phase is mediated by GPR109A expressed on keratinocytes. Interestingly, the first phase of flushing was blocked by a selective cyclooxygenase-1 (COX-1) inhibitor, and the late phase was sensitive to a selective COX-2 inhibitor. Both monomethyl fumarate and nicotinic acid induced PGE2 formation in isolated keratinocytes through activation of GPR109A and COX-2. Thus, the early and late phases of the GPR109A-mediated cutaneous flushing reaction involve different epidermal cell types and prostanoid-forming enzymes. These data will help to guide new efficient approaches to mitigate nicotinic acid-induced flushing and may help to exploit the potential antipsoriatic effects of GPR109A agonists in the skin.

HDL-C and LDL-C: their role in stroke pathogenesis and implications for treatment

Elevated serum low-density lipoprotein cholesterol (LDL-C) and low serum high-density lipoprotein cholesterol (HDL-C) are risk factors for atherosclerotic ischemic stroke. The National Cholesterol Education Panel and the American Heart Association have released guidelines for the treatment of dyslipidemia that stress LDL-C reduction using HMG CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitors (statins) and are applicable to individuals who have had or are at a high risk of having a stroke. Treatment of low HDL-C is a secondary goal of these guidelines and can be best achieved by using extended-release niacin (alone or in combination with statins) and fibrates. Early and aggressive treatment of dyslipidemia is an important component of a multimodality approach to stroke prevention.

Niaspan treatment induces neuroprotection after stroke

INTRODUCTION

Niaspan, an extended-release formulation of Niacin (vitamin B3), has been widely used to increase high density lipoprotein (HDL) cholesterol and to prevent cardiovascular diseases and stroke. In this study, we tested whether Niaspan administered acutely after stroke is neuroprotective.

METHODS

Adult male rats (n=8/group) were subjected to 2h of middle cerebral artery occlusion (MCAo) and treated with or without different doses of Niaspan (20, 40 or 80 mg/kg) at 2 and 24h after MCAo. A battery of functional outcome tests was performed, and serum HDL and triglycerides were measured. Rats were sacrificed at 7 days after MCAo and lesion volumes were measured. The optimal dose of Niaspan treatment of stroke was chosen for immunostaining: deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), cleaved caspase-3, tumor necrosis factor alpha (TNF-alpha), vascular endothelial growth factor (VEGF) and phosphorylated phosphatidylinositol 3-kinase (p-PI3K). Another set of rats (n=4/group) were killed at 7 days after MCAo for Western blot assay.

RESULTS

Niaspan dose-dependently reduced infarct volume and improved functional outcome after stroke. No significant difference in HDL and triglyceride levels was detected between Niaspan treatments and MCAo control groups. Niaspan treatment significantly decreased the number of TUNEL-positive cells (105+/-17) and cleaved caspase-3 expression (381+/-33) in the ischemic brain compared to MCAo control (165+/-18; 650+/-61, respectively; p<or=0.05). Niaspan treatment significantly reduced the expression of TNF-alpha (9.7+/-1.1% vs. 16+/-2.2%; p<or=0.05) and negative correlations were observed between the functional tests and the expression of TNF-alpha (r=-0.71, p<or=0.05). Niaspan treatment also significantly increased the expression of VEGF (5.2+/-0.9%) and PI3K/Akt (0.381+/-0.04%) in the ischemic brain compared with non-treated MCAo control (2.6+/-0.4%; 0.24+/-0.03, respectively; p<or=0.05). The functional outcome was positively correlated with p-PI3K (r=0.7, p<or=0.05).

CONCLUSIONS

Treatment of stroke with Niaspan at 2h after MCAo reduces infarct volume and improves neurological outcome and provides neuroprotection. The neuroprotective effects of Niaspan were associated with reduction of apoptosis and attenuation of TNF-alpha expression. VEGF and the PI3K/Akt pathway may contribute to the Niaspan-induced neuroprotection after stroke.

Evidence that niacin inhibits acute vascular inflammation and improves endothelial dysfunction independent of changes in plasma lipids

OBJECTIVE

To determine if niacin can confer cardiovascular benefit by inhibiting vascular inflammation and improving endothelial function independent of changes in plasma lipid and lipoprotein levels.

METHODS AND RESULTS

New Zealand white rabbits received normal chow or chow supplemented with 0.6% or 1.2% (wt/wt) niacin. This regimen had no effect on plasma cholesterol, triglyceride, or high-density lipoprotein levels. Acute vascular inflammation and endothelial dysfunction were induced in the animals with a periarterial carotid collar. At the 24-hour postcollar implantation, the endothelial expression of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, and monocyte chemotactic protein-1 was markedly decreased in the niacin-supplemented animals compared with controls. Niacin also inhibited intima-media neutrophil recruitment and myeloperoxidase accumulation, enhanced endothelial-dependent vasorelaxation and cyclic guanosine monophosphate production, increased vascular reduced glutathione content, and protected against hypochlorous acid-induced endothelial dysfunction and tumor necrosis factor alpha-induced vascular inflammation.

CONCLUSION

Previous human intervention studies have demonstrated that niacin inhibits coronary artery disease. This benefit is thought to be because of its ability to reduce low-density lipoprotein and plasma triglyceride levels and increase high-density lipoprotein levels. The present study showed that niacin inhibits vascular inflammation and protects against endothelial dysfunction independent of these changes in plasma lipid levels.

Niacin improves renal lipid metabolism and slows progression in chronic kidney disease

BACKGROUND

Mounting evidence points to lipid accumulation in the diseased kidney and its contribution to progression of nephropathy. We recently found heavy lipid accumulation and marked dysregulation of lipid metabolism in the remnant kidneys of rats with chronic renal failure (CRF). Present study sought to determine efficacy of niacin supplementation on renal tissue lipid metabolism in CRF.

METHODS

Kidney function, lipid content, and expression of molecules involved in cholesterol and fatty acid metabolism were determined in untreated CRF (5/6 nephrectomized), niacin-treated CRF (50 mg/kg/day in drinking water for 12 weeks) and control rats.

RESULTS

CRF resulted in hypertension, proteinuria, renal tissue lipid accumulation, up-regulation of scavenger receptor A1 (SR-A1), acyl-CoA cholesterol acyltransferase-1 (ACAT1), carbohydrate-responsive element binding protein (ChREBP), fatty acid synthase (FAS), acyl-CoA carboxylase (ACC), liver X receptor (LXR), ATP binding cassette (ABC) A-1, ABCG-1, and SR-B1 and down-regulation of sterol responsive element binding protein-1 (SREBP-1), SREBP-2, HMG-CoA reductase, PPAR-alpha, fatty acid binding protein (L-FABP), and CPT1A. Niacin therapy attenuated hypertension, proteinuria, and tubulo-interstitial injury, reduced renal tissue lipids, CD36, ChREBP, LXR, ABCA-1, ABCG-1, and SR-B1 abundance and raised PPAR-alpha and L-FABP.

CONCLUSIONS AND GENERAL SIGNIFICANCE

Niacin administration improves renal tissue lipid metabolism and renal function and structure in experimental CRF.

Proteomics of apolipoproteins and associated proteins from plasma high-density lipoproteins

Proteomics studies have extended the list of identified apolipoproteins and associated proteins present in HDL and its subclasses. These proteins appear to cluster around specific functions related to lipid metabolism, inflammation, the immune system, hormone-binding, hemostasis, and antioxidant properties. Small studies suggest that there are substantial differences between the HDL proteome from cardiovascular disease patients and that from controls. Furthermore, dyslipidemia therapy shifts the HDL proteome from patients toward the profile observed in healthy controls. In addition, the proteome of HDL and LDL from patients with insulin resistance and peripheral atherosclerosis show significant differences with that of matched healthy controls. The proteome of HDL and LDL density subclasses have apolipoproteins and associated proteins profiles that suggest subclass-specific functions. However, proteomics studies of lipoproteins are few and small and should be interpreted with caution. Nonetheless rapid technical progress in proteomic platforms suggest that soon analysis time will be reduced and precise measurement of identified proteins will be possible. This, combined with controlled purification steps of HDL and its subclasses should provide further information about proteins involved in the particles postulated spectrum of functions, including those believed to be atheroprotective.

Nicotinic acid and the prevention of coronary artery disease

PURPOSE OF REVIEW

Nicotinic acid is the most potent treatment clinically available for lowering LDL cholesterol and VLDL cholesterol and raising HDL cholesterol. The strong inverse relationship between coronary heart disease risk and HDL cholesterol at all levels of LDL cholesterol has, therefore, given renewed emphasis on the therapeutic potential of niacin. The purpose of this review is to evaluate advances in the elucidation of mechanisms by which nicotinic acid affects the lipoprotein profile and, more recently, emerging evidence of nonlipid-mediated anti-inflammatory effects.

RECENT FINDINGS

Niacin treatment reduces cardiovascular events and the progression of atherosclerosis. Identification of G-protein-coupled receptor 109A as the receptor for nicotinic acid has provided insights into how treatment with this compound leads to a favourable alteration in HDL cholesterol. In addition, evidence of nonlipid-mediated anti-inflammatory effects of nicotinic acid such as direct enhancement of adiponectin secretion demonstrates a novel atheroprotective role.

SUMMARY

Whether nicotinic acid use becomes routine in the treatment of atherosclerosis is likely to be determined by the results of two ongoing clinical outcome trials. In addition, further research is required to explore the 'pleiotropic' effects of nicotinic acid and will ultimately provide a platform for the development of newer molecules that are potentially beneficial but without the well known side-effects.

Reverse cholesterol transport in type 2 diabetes mellitus

High-density lipoprotein (HDL) plays an important protective role against atherosclerosis, and the anti-atherogenic properties of HDL include the promotion of cellular cholesterol efflux and reverse cholesterol transport (RCT), as well as antioxidant, anti-inflammatory and anticoagulant effects. RCT is a complex pathway, which transports cholesterol from peripheral cells and tissues to the liver for its metabolism and biliary excretion. The major steps in the RCT pathway include the efflux of free cholesterol mediated by cholesterol transporters from cells to the main extracellular acceptor HDL, the conversion of free cholesterol to cholesteryl esters and the subsequent removal of cholesteryl ester in HDL by the liver. The efficiency of RCT is influenced by the mobilization of cellular lipids for efflux and the intravascular remodelling and kinetics of HDL metabolism. Despite the increased cardiovascular risk in people with type 2 diabetes, current knowledge on RCT in diabetes is limited. In this article, abnormalities in RCT in type 2 diabetes mellitus and therapeutic strategies targeting HDL and RCT will be reviewed.

Nicotinic acid: a new look at an old drug

Dyslipidemia is central to the process of atherosclerosis. Modification of the lipid profile by diet, exercise, or pharmacologic therapy has been demonstrated to reduce the risk from atherosclerosis in clinical studies in primary and secondary prevention. Nicotinic acid has been in clinical use for over 50 years. The administration of nicotinic acid has been demonstrated to reduce apolipoprotein B-containing lipoproteins (very low-density lipoprotein, intermediate-density lipoprotein, low-density lipoprotein and lipoprotein (a)). Nicotinic acid also exerts significant effects on high-density lipoprotein. In addition to improving dyslipidemia, nicotinic acid has been demonstrated to induce a number of nonlipid or pleiotropic effects. The recent discovery of the nicotinic acid receptor has improved knowledge relative to the mechanism of action and the adverse effect profile of nicotinic acid. Clinical trials utilizing clinical or angiographic end points demonstrated efficacy for the use of nicotinic acid in monotherapy or in combination with bile acid resins or statins.

Four additional mouse crosses improve the lipid QTL landscape and identify Lipg as a QTL gene

To identify genes controlling plasma HDL and triglyceride levels, quantitative trait locus (QTL) analysis was performed in one backcross, (NZO/H1Lt x NON/LtJ) x NON/LtJ, and three intercrosses, C57BL/6J x DBA/2J, C57BL/6J x C3H/HeJ, and NZB/B1NJ x NZW/LacJ. HDL concentrations were affected by 25 QTL distributed on most chromosomes (Chrs); those on Chrs 1, 8, 12, and 16 were newly identified, and the remainder were replications of previously identified QTL. Triglyceride concentrations were controlled by nine loci; those on Chrs 1, 2, 3, 7, 16, and 18 were newly identified QTL, and the remainder were replications. Combining mouse crosses with haplotype analysis for the HDL QTL on Chr 18 reduced the list of candidates to six genes. Further expression analysis, sequencing, and quantitative complementation testing of these six genes identified Lipg as the HDL QTL gene on distal Chr 18. The data from these crosses further increase the ability to perform haplotype analyses that can lead to the identification of causal lipid genes.

Niacin ameliorates oxidative stress, inflammation, proteinuria, and hypertension in rats with chronic renal failure

Significant reduction of renal mass causes progressive deterioration of renal function and structure which is mediated by systemic and glomerular hypertension, hyperfiltration, oxidative stress, inflammation, and dyslipidemia. Niacin is known to improve lipid metabolism and exert antioxidant/anti-inflammatory actions. Therefore, we considered that niacin supplementation may attenuate oxidative stress, inflammation, and tissue injury in the remnant kidney. To this end, 56 nephrectomized [chronic kidney disease (CKD)] rats were randomly assigned to niacin-treated (50 mg x kg(-1) x day(-1) in the drinking water for 12 wk) and untreated groups. Sham-operated rats served as controls. The untreated CKD rats exhibited azotemia, hypertension, hypertriglyceridemia, proteinuria, glomerulosclerosis, tubulointerstitial damage, upregulation of MCP-1, plasminogen activator inhibitor-1 (PAI-1), transforming growth factor (TGF)-beta, cyclooxygenase (COX)-1, COX-2, and NAD(P)H oxidase (NOX-4, gp91(phox), p47(phox) and p22(phox) subunits) and activation of NF-kappaB (IkappaB phosphorylation). Niacin administration reduced MCP-1, PAI-1, TGF-beta, p47(phox), p22(phox), COX-1, and NF-kappaB activation, ameliorated hypertension, proteinuria, glomerulosclerosis, and tubulointerstitial injury. Although niacin lowered serum creatinine and raised creatinine clearance, the differences did not reach statistical significance. Thus niacin supplementation helps to attenuate histological injury and mitigate upregulation of oxidative and inflammatory systems in the remnant kidney.

Fixed-dose combination of extended-release niacin plus simvastatin for lipid disorders

Coronary heart disease (CHD) carries significant morbidity and mortality worldwide. Elevated LDL-cholesterol and reduced HDL-cholesterol levels are well-recognized CHD risk factors. Despite guideline recommendations for intensive therapy among patients at high risk for CHD to lower LDL-cholesterol, such lowering has failed to prevent approximately two-thirds of cardiovascular events. As a result of new data, guidelines have begun to focus on non-HDL-cholesterol, HDL-cholesterol and triglycerides as treatment targets, with the end result being a recommendation for combination therapy, such as niacin plus statin for the treatment of dyslipidemia. Compared with statin monotherapy, a combination of niacin and statin therapy provides beneficial effects on a broad range of lipid particles and some evidence suggests a further reduction in CHD risk. Recent studies have shown that the combination of a fixed dose of extended-release niacin plus simvastatin reduces non-HDL-cholesterol, LDL-cholesterol, triglycerides and total cholesterol:HDL-cholesterol ratio by approximately 50% while increasing HDL-cholesterol by 25%. The safety of this combination is consistent with the safety profiles of each individual component and is well tolerated. A long-term study is currently being conducted to evaluate whether this combination therapy confers an additive impact on clinical end points.

A quercetin containing supplement reduces niacin-induced flush in humans

Coronary artery disease is associated with increased serum levels of cholesterol, triglycerides and LDL, but low levels of HDL. The most potent agent capable of reversing this trend is the vitamin nicotinic acid (niacin). However, compliance even with extended-release preparations and addition of acetylsalicylic acid (ASA) is hampered by the development of a feeling of erythema and burning ("flush"), especially on the face. We recently showed that the natural flavonoids quercetin and luteolin can eliminate "flush", as well as inhibit both niacin-induced plasma prostaglandin D2 (PGD2) and serotonin increase in an animal model. We conducted a pilot clinical study in humans. Four normal male subjects received (a) 1 g immediate release niacin either alone or after (b) the dietary formulation (Algonot-plus) containing 150 mg quercetin per capsule. Subjects completed a visual scale (1 = no, 5 = worst response) symptom assessment. Erythema and burning sensation scores were both 4.75+/-0.50 and lasted for 3.63+/-1.11 hours. After Algonot-plus administration, both scores were reduced to 2.5+/-0.58 and lasted only for 1.68+/-0.70 hours. Quercetin also inhibited methylnicotinate-induced human mast cell PGD2 release. These preliminary results suggest that quercetin could reduce niacin-induced "flush" in humans.

Adipose tissue as a source of nicotinamide N-methyltransferase and homocysteine

Nicotinamide N-methyltransferase (NNMT) catalyses the conversion of nicotinamide to 1-methylnicotinamide and plays an important role in hepatic detoxification reactions. Here we show that, in addition to the liver, 3T3-L1 adipocytes as well as human and murine adipose tissue explants express high amounts of enzymatically active NNMT. NNMT mRNA levels and enzyme activity increased in 3T3-L1 cells in a differentiation-dependent manner. Homocysteine, the atherogenic product of the NNMT-catalyzed reaction, was secreted from 3T3-L1 cells or adipose tissue cultures. Homocysteine release increased during 3T3-L1 differentiation and was reduced when adipose tissue was treated with the NNMT inhibitor 1-methylnicotinamide. Nicotinic acid (NA), a widely used drug to lower elevated plasma lipid levels, induced NNMT enzyme activity in white adipose tissue of mice. In tissue culture nicotinamide treatment led to an increase in adipose tissue homocysteine secretion. These data support the concept that adipose tissue NNMT contributes to the increased plasma homocysteine levels in patients treated with NA.

Effects of oral niacin on endothelial dysfunction in patients with coronary artery disease: results of the randomized, double-blind, placebo-controlled INEF study

High-density-lipoproteins-cholesterol (HDL-C) is invertedly related to the incidence of cardiovascular events. Recent studies suggest that HDL-C directly improves endothelial function. Nicotinic acid (niacin) effectively raises serum HDL-C. We therefore hypothesized that treatment with niacin improves endothelial dysfunction in patients with coronary artery disease (CAD). One hundred seven patients with CAD were randomly assigned to double-blinded treatment for 12 weeks with extended-release (ER)-niacin 1000 mg/day (N) or placebo (C), respectively. Flow-mediated dilation (FMD) of the brachial artery, nitroglycerin-mediated endothelium-independent dilation (NMD) and serum lipid concentrations were measured before and after treatment. Triglycerides (P=0.013), low-density-lipoprotein-cholesterol (LDL-C) (P=0.013) and HDL-C (P<0.0001) were altered by N compared to C. Niacin treatment was without effect on FMD or NMD, respectively, compared to placebo. However, post-hoc subgroup analysis revealed an improvement in FMD in patients with low HDL-C at baseline (absolute change in FMD (mean+/-S.D.) N: +3.25+/-3.88%, C: +1.03+/-2.71% in low tertile HDL-C <or=45 mg/dl. P=0.047). The present findings indicate that ER-niacin treatment improves endothelial dysfunction in patients with CAD and low HDL-C, but not with normal HDL-C.

Niacin inhibits vascular oxidative stress, redox-sensitive genes, and monocyte adhesion to human aortic endothelial cells

In pharmacological doses, nicotinic acid (niacin) reduces myocardial infarction, stroke and atherosclerosis. The beneficial effects of niacin on lipoproteins are thought to mediate these effects. We hypothesized that niacin inhibits oxidative stress and redox-sensitive inflammatory genes that play a critical role in early atherogenesis. In cultured human aortic endothelial cells (HAEC), niacin increased nicotinamide adenine dinucleotide phosphate (NAD(P)H) levels by 54% and reduced glutathione (GSH) by 98%. Niacin inhibited: (a) angiotensin II (ANG II)-induced reactive oxygen species (ROS) production by 24-86%, (b) low density lipoprotein (LDL) oxidation by 60%, (c) tumor necrosis factor alpha (TNF-alpha)-induced NF-kappaB activation by 46%, vascular cell adhesion molecule-1 (VCAM-1) by 77-93%, monocyte chemotactic protein-1 (MCP-1) secretion by 34-124%, and (d) in a functional assay TNF-alpha-induced monocyte adhesion to HAEC (41-54%). These findings indicate for the first time that niacin inhibits vascular inflammation by decreasing endothelial ROS production and subsequent LDL oxidation and inflammatory cytokine production, key events involved in atherogenesis. Initial data presented herein support the novel concept that niacin has vascular anti-inflammatory and potentially anti-atherosclerotic properties independent of its effects on lipid regulation.

Management of lipids in the prevention of cardiovascular events

Lipid-modifying therapy has been proven to significantly reduce cardiovascular events and total mortality. Most of the data have come from statin trials. Statin therapy is generally well-tolerated and safe, and for patients who are at higher than average risk of cardiovascular disease, the benefit of lipid-modifying therapy far exceeds the risk. Careful risk assessment is a critical component of effective lipid-modifying therapy. In the foreseeable future, low-density lipoprotein cholesterol (LDL-C) will remain the primary therapeutic target, and combination therapy is likely to become the norm. The major questions are how low to treat and how to achieve increasingly aggressive targets in lipid-lowering therapy. Many patients on LDL-lowering therapy continue to have abnormalities of the triglyceride-high-density lipoprotein (TG-HDL) axis, so additional drug therapy is often considered for such patients. In this review, we briefly discuss new developments in cardiovascular risk assessment, then discuss recent developments in treatment to reduce LDL, and finally discuss current concepts regarding therapy targeting the TG-HDL axis.