Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL

Joint effects of paraoxonase 1 rs662 polymorphism and vitamins C/E intake on coronary artery disease severity (Gensini and SYNTAX scores) and lipid profile in patients undergoing coronary angiography

Introduction

Considering the emergence of the concept of personalized nutrition in recent years and its importance in the treatment of diseases, the purpose of this study was to investigate the interaction of paraoxonase (PON)1 rs662 polymorphism and vitamin C/E intake on coronary artery disease (CAD) severity and lipid profile in patients undergoing diagnostic angiography.

Methods

This cross-sectional study was carried out on 428 patients undergoing angiography. The PON-1 genotypes were detected by the polymerase chain reaction-restriction fragment length polymorphism technique. Dietary intake was obtained using a valid questionnaire.

Results

After adjustment for potential confounders, R allele carriers (RR + RQ) have lower HDL-C levels than non-carriers (QQ) (P ≤ 0.05). On the other hand, higher consumption of vitamin C was associated with a reduced risk of high total cholesterol (OR: 0.42, 95% CI 0.23-0.75, P = 0.003) and low-density lipoprotein cholesterol (OR: 0.49, 95% CI 0.25-0.96, P = 0.038) and an increased risk of low high-density lipoprotein cholesterol (OR: 1.88, 95% CI 1.03-3.42, P = 0.037). Furthermore, a significant interaction was observed between vitamin C intake and genotypes of rs66 polymorphism on LDL-C (P = 0.050). In detail, the R-allele carriers with lower vitamin C intake had higher LDL-C levels than QQ genotype carriers. No significant interaction was found between vitamin E intake and rs662 polymorphism genotypes on the Gensini and SYNTAX scores and lipid profile (P > 0.05).

Conclusion

The novel finding of the present study was the existence of a significant interaction between rs662 polymorphism and vitamin C intake on LDL-C. More specifically, R allele carriers with lower vitamin C intake were susceptible to higher LDL-C.

Optimal Nutrition in the Older Adult: Beneficial Versus Ineffective Supplements

PURPOSE OF REVIEW

Proper nutrition in older adults is essential, as nutritional deficiencies are common in this population. This review aims to summarize the benefits and risks of nutritional supplementation in the older adult population including the efficacy of various supplements, their risks, and common drug interactions with frequently prescribed medications.

RECENT FINDINGS

In recent years, a growing percentage of older adults have been found to take multiple daily nutritional supplements. This population has complex nutritional needs due to the physiology of aging and the presence of comorbidities. However, many primary care providers are unaware of the benefits and drawbacks of nutritional supplementation in the elderly. This review summarizes the current literature to provide more clarity to providers on how to support this population's nutritional needs. Nutritional supplementation is essential for elderly populations who may not be able to obtain adequate nutrition from dietary sources. Supplements vary widely in efficacy and safety. As such, supplementation should be individualized and guided by a qualified healthcare provider to ensure patients receive effective, beneficial nutrition.

Serum Cholesterol Differences Between Statin Users Who Take Dietary Supplements and Those Who Do Not: NHANES 2013-2018

Background

Cardiovascular disease (CVD) is the leading cause of mortality in the United States and statins are the most commonly prescribed medication. It is important to understand the potential impact supplements may have when taken in combination with statins on serum lipid outcomes.

Objectives

To evaluate the differences in the concentrations of cholesterol, triacylglycerol (TAG), and HbA1c between adults who use statins alone and those who combine statins and dietary supplements.

Methods

A cross-sectional analysis using data from US adults aged ≥20 years who participated in the NHANES (2013-2018). The serum concentrations of lipids and the HbA1c levels were compared using independent sample t-tests. All analyses were adjusted for the complex survey design and used appropriate sample weights.

Results

Of 16,327 participants included in this analysis, 13% reported the use of statins alone, and 8.8% used statins and dietary supplements. Statin users who used dietary supplements tended to be women (50.5%), aged 65.8 ± 0.4 years, and were more likely to be White (77.4%). Participants who used statins in combination with dietary supplements were less likely to have higher levels of total cholesterol (5.1% ± 1.4% vs. 15.6% ± 2.7%, P < 0.001), HbA1c (6.0% ± 0.1% vs. 6.3% ± 0.1%, P < 0.05), and HDL cholesterol (50 ± 1.3 vs. 47 ± 0.8 mg/dL, P < 0.05) than those who used statins alone. No significant differences were identified between the two groups for LDL cholesterol and TAG concentrations.

Conclusions

Statin users who coingested dietary supplements were less likely to have high levels of total cholesterol and HbA1c and greater HDL levels than statin users who did not take dietary supplements. Dietary intake, lifestyle choices, and other confounders may have influenced the observed outcome differences for those who took dietary supplements with statins and those who did not.

Molecular Mechanisms Underlying the Therapeutic Role of Vitamin E in Age-Related Macular Degeneration

The eye is particularly susceptible to oxidative stress and disruption of the delicate balance between oxygen-derived free radicals and antioxidants leading to many degenerative diseases. Attention has been called to all isoforms of vitamin E, with α-tocopherol being the most common form. Though similar in structure, each is diverse in antioxidant activity. Preclinical reports highlight vitamin E’s influence on cell physiology and survival through several signaling pathways by activating kinases and transcription factors relevant for uptake, transport, metabolism, and cellular action to promote neuroprotective effects. In the clinical setting, population-based studies on vitamin E supplementation have been inconsistent at times and follow-up studies are needed. Nonetheless, vitamin E’s health benefits outweigh the controversies. The goal of this review is to recognize the importance of vitamin E’s role in guarding against gradual central vision loss observed in age-related macular degeneration (AMD). The therapeutic role and molecular mechanisms of vitamin E’s function in the retina, clinical implications, and possible toxicity are collectively described in the present review.

Food supplement vitamins, minerals, amino-acids, fatty acids, phenolic and alkaloid-based substances: An overview of their interaction with drugs

Food supplements are a widespread group of products ingested as a diet complement, whose consumption has recently skyrocketed due to the consumers' concern with their well-being. Among food supplements, vitamin- and mineral-based ones are the top sellers, and the demand of others, such as those containing polyphenols, is increasing. Owing to their alleged natural characteristics, consumers take the safety of food supplements for granted, and use them even when taking medicines. Thus, their potential interactions with drugs have been sparsely evaluated. This manuscript aims to bring forth an up-to-date overview of the most important knowledge involving the interactions between food supplements and drugs, relevant to be aware by nutritionists and other healthcare professionals. To this end, an extensive bibliographic review was conducted focusing on peer reviewed data from experimental in vivo evidence and clinical studies whenever major clinical interactions have been reported. Elder people and polymedicated or chronic patients are especially vulnerable to the therapeutic ineffectiveness and toxicity caused by these types of interactions. Drugs used to treat cardiovascular, autoimmune, nervous, and oncological diseases are commonly involved in important clinical interactions with food supplements, many with a narrow therapeutic margin.

Vitamin E beyond Its Antioxidant Label

Vitamin E, comprising tocopherols and tocotrienols, is mainly known as an antioxidant. The aim of this review is to summarize the molecular mechanisms and signaling pathways linked to inflammation and malignancy modulated by its vitamers. Preclinical reports highlighted a myriad of cellular effects like modulating the synthesis of pro-inflammatory molecules and oxidative stress response, inhibiting the NF-κB pathway, regulating cell cycle, and apoptosis. Furthermore, animal-based models have shown that these molecules affect the activity of various enzymes and signaling pathways, such as MAPK, PI3K/Akt/mTOR, JAK/STAT, and NF-κB, acting as the underlying mechanisms of their reported anti-inflammatory, neuroprotective, and anti-cancer effects. In clinical settings, not all of these were proven, with reports varying considerably. Nonetheless, vitamin E was shown to improve redox and inflammatory status in healthy, diabetic, and metabolic syndrome subjects. The anti-cancer effects were inconsistent, with both pro- and anti-malignant being reported. Regarding its neuroprotective properties, several studies have shown protective effects suggesting vitamin E as a potential prevention and therapeutic (as adjuvant) tool. However, source and dosage greatly influence the observed effects, with bioavailability seemingly a key factor in obtaining the preferred outcome. We conclude that this group of molecules presents exciting potential for the prevention and treatment of diseases with an inflammatory, redox, or malignant component.

Study of Cardiovascular Risk Factors in Adolescents: Association between Intake of Vitamins A and E and Lipid Profile

Background:

The diet of Brazilian adolescents is characterized by high intake of fats and sugars and low consumption of antioxidant micronutrients, particularly vitamins A and E. In addition to dietary inadequacies, a significant number of these adolescents present changes in plasma lipoproteins, which may be caused by environmental and lifestyle factors.

Objective:

To investigate the association between inadequate intake of vitamins A and E and changes in plasma lipoprotein concentrations in Brazilian adolescents.

Methods:

Cross-sectional, descriptive, multicenter, school-based, nationwide study with 37,023 Brazilian adolescents aged 12 to 17 years were included. Data on sociodemographic characteristics, vitamin A and E intake, and lipid and anthropometric profile were collected. The Student’s t-test was used to compare means and a logistic regression to verify associations; analyses were conducted in the STATA software version 14.0. The study was approved by the Ethics Committees of the participating institutions and all participants signed an Assent Form.

Results:

The average vitamin A intake was higher among boys, but consumption below recommendation was found in both sexes. Inadequate intake of vitamins A and E was associated with a higher risk of low HDL-c levels in male and public school adolescents. Low vitamin E intake was associated with a higher risk of hypercholesterolemia and hypertriglyceridemia in Brazilian adolescents.

Conclusion:

This study showed a high prevalence of inadequate intake of vitamins A and E among Brazilian adolescents and data suggesting associations between low intake of these micronutrients and changes in plasma lipoprotein concentrations in this public.

Demystifying Oxidative Stress

The hypothesis that reactive oxygen species (ROS) can be not just associated with but causally implicated in disease was first made in 1956, but so far, the oxidative stress theory of disease has not led to major therapeutic breakthrough, and the use of antioxidant is now confined to the field of complementary medicine. This chapter reviews the lack of high-level clinical evidence for the effectiveness of antioxidants in preventing disease and the epistemological problems of the oxidative stress theory of disease. We conclude on possible ways forward to test this hypothesis with approaches that take into account personalized medicine. The previous oxidative stress model has helped neither to diagnose nor to treat possibly ROS-related or ROS-dependent diseases. The redox balance concept that low ROS levels are beneficial or tolerable and high levels are disease triggers and best reduced is apparently wrong. Physiological ROS signalling may become dysfunctional or a disease trigger by at least five mechanisms: a physiological source may appear at an unphysiological site, a physiological source may be underactivated (less common) or overactivated (more common), a new source may appear, a physiological source may be overactivated or underactivated, and a toxifying enzyme may convert an ROS signal molecule into a more reactive molecule. The latter three mechanisms may reach a physiological or nonphysiological target. All of these dysregulations may be the direct and essential cause of a disease (rarely the case) or just a secondary epiphenomenon, which will disappear once the non-ROS-related cause of the disease is cured (much more common). Importantly, these mechanisms are the same for almost every signalling system. Causal target validation (sources, toxifiers and targets) is essential in order to identify effective drugs and therapies for ROSopathies.

Association between HDL Cholesterol Levels and the Consumption of Vitamin A in Metabolically Healthy Obese Lebanese: A Cross-Sectional Study among Adults in Lebanon

OBJECTIVES

Previous studies show the association between vitamin A and elevation of plasma triglyceride concentrations. However, limited information exists on the association between vitamin A and plasma HDL cholesterol concentrations. The aim of this study is to investigate the association between plasma HDL cholesterol levels and vitamin A intake in 57 metabolically healthy obese (MHO) Lebanese.

METHODS

Out of the 112 adult obese participants who had completed anthropometric and biochemical data, 57 (22 males and 35 females) aged 18-62 years old are metabolically healthy and their data are included in this study. A valid semiquantitative food frequency questionnaire (SQFFQ) was used to test vitamin A intake among other antioxidants. The participants were recruited from the database of three dietary clinics across Lebanon.

RESULTS

Pearson's correlation coefficient was used to measure the strength of the relationship between vitamin A and plasma HDL cholesterol levels. There was a significant positive correlation (P value = 0.0225) between vitamin A consumption and HDL cholesterol serum levels in obese participants; when vitamin A levels decrease, HDL levels decrease more in female than in male participants.

CONCLUSION

The association between dietary vitamin A, a powerful antioxidant, and high HDL levels is shown in MHO but should be further exploited in future studies.

Metoprolol induces oxidative damage in common carp (Cyprinus carpio)

During the last decade, β-blockers such as metoprolol (MTP) have been frequently detected in surface water, aquatic systems and municipal water at concentrations of ng/L to μg/L. Only a small number of studies exist on the toxic effects induced by this group of pharmaceuticals on aquatic organisms. Therefore, the present study aimed to evaluate the oxidative damage induced by MTP in the common carp Cyprinus carpio, using oxidative stress biomarkers. To this end, indicators of cellular oxidation such as hydroperoxide content (HPC), lipid peroxidation (LPX) and protein carbonyl content (PCC) were determined, as well as the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Also, concentrations of MTP and its metabolite O-desmethyl metoprolol were determined in water as well as carp gill, liver, kidney, brain and blood, along with the partial uptake pattern of these compounds. Results show that carp takes up MTP and its metabolite in the different organs evaluated, particularly liver and gill. The oxidative stress biomarkers, HPC, LPX, and PCC, as well as SOD and CAT activity all increased significantly at most exposure times in all organs evaluated. Results indicate that MTP and its metabolite induce oxidative stress on the teleost C. carpio and that the presence of these compounds may constitute a risk in water bodies for aquatic species.

The effect of selenium supplementation on coronary heart disease: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Selenium is a crucial mineral with antioxidant and immune functions, and selenium deficiency may increase the risk of coronary heart disease (CHD). However, the effect of selenium supplementation on CHD is still controversial according to numerous randomized controlled trials (RCTs). The aim of our meta-analysis study was to investigate the impact of selenium on CHD.

METHODS

PUBMED, EMBASE, MEDLINE, and the Cochrane Central Register of Controlled Trials databases were systematically searched to identify RCTs evaluating the effect of selenium supplementation on CHD mortality, blood lipid profile (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol), serum C-reactive protein (CRP), and the level of glutathione peroxidase (GSH-PX) from inception until September 20, 2016. Odds ratio of CHD mortality and the associated 95% confidence intervals (CIs) were calculated using the fixed effect model. Weighted mean difference or standardized mean difference (SMD) and 95% confidence intervals (CIs) were calculated to determine the lipid profile, serum CRP, and GSH-PX using fixed effect or random effect models depending on the observed heterogeneity.

RESULTS

A total of 16 eligible RCTs with 43998 participants were included. Significant effects were observed for serum CRP (SMD=-0.48; 95% CI, -0.96 to 0; p=0.049) and GSH-PX (SMD=0.5; 95% CI, 0.36-0.64; p<0.001) after selenium supplementation. However, selenium supplementation was not statistically associated with CHD mortality and an aberrant lipid profile.

CONCLUSION

Selenium supplementation decreased serum CRP and increased the GSH-PX level, suggesting a positive effect on reducing oxidative stress and inflammation in CHD. However, selenium supplementation is not sufficient to reduce mortality and to improve the lipid status.

Niacin for primary and secondary prevention of cardiovascular events

BACKGROUND

Nicotinic acid (niacin) is known to decrease LDL-cholesterol, and triglycerides, and increase HDL-cholesterol levels. The evidence of benefits with niacin monotherapy or add-on to statin-based therapy is controversial.

OBJECTIVES

To assess the effectiveness of niacin therapy versus placebo, administered as monotherapy or add-on to statin-based therapy in people with or at risk of cardiovascular disease (CVD) in terms of mortality, CVD events, and side effects.

SEARCH METHODS

Two reviewers independently and in duplicate screened records and potentially eligible full texts identified through electronic searches of CENTRAL, MEDLINE, Embase, Web of Science, two trial registries, and reference lists of relevant articles (latest search in August 2016).

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) that either compared niacin monotherapy to placebo/usual care or niacin in combination with other component versus other component alone. We considered RCTs that administered niacin for at least six months, reported a clinical outcome, and included adults with or without established CVD.

DATA COLLECTION AND ANALYSIS

Two reviewers used pre-piloted forms to independently and in duplicate extract trials characteristics, risk of bias items, and outcomes data. Disagreements were resolved by consensus or third party arbitration. We conducted random-effects meta-analyses, sensitivity analyses based on risk of bias and different assumptions for missing data, and used meta-regression analyses to investigate potential relationships between treatment effects and duration of treatment, proportion of participants with established coronary heart disease and proportion of participants receiving background statin therapy. We used GRADE to assess the quality of evidence.

MAIN RESULTS

We included 23 RCTs that were published between 1968 and 2015 and included 39,195 participants in total. The mean age ranged from 33 to 71 years. The median duration of treatment was 11.5 months, and the median dose of niacin was 2 g/day. The proportion of participants with prior myocardial infarction ranged from 0% (4 trials) to 100% (2 trials, median proportion 48%); the proportion of participants taking statin ranged from 0% (4 trials) to 100% (12 trials, median proportion 100%).Using available cases, niacin did not reduce overall mortality (risk ratio (RR) 1.05, 95% confidence interval (CI) 0.97 to 1.12; participants = 35,543; studies = 12; I2 = 0%; high-quality evidence), cardiovascular mortality (RR 1.02, 95% CI 0.93 to 1.12; participants = 32,966; studies = 5; I2 = 0%; moderate-quality evidence), non-cardiovascular mortality (RR 1.12, 95% CI 0.98 to 1.28; participants = 32,966; studies = 5; I2 = 0%; high-quality evidence), the number of fatal or non-fatal myocardial infarctions (RR 0.93, 95% CI 0.87 to 1.00; participants = 34,829; studies = 9; I2 = 0%; moderate-quality evidence), nor the number of fatal or non-fatal strokes (RR 0.95, 95% CI 0.74 to 1.22; participants = 33,661; studies = 7; I2 = 42%; low-quality evidence). Participants randomised to niacin were more likely to discontinue treatment due to side effects than participants randomised to control group (RR 2.17, 95% CI 1.70 to 2.77; participants = 33,539; studies = 17; I2 = 77%; moderate-quality evidence). The results were robust to sensitivity analyses using different assumptions for missing data.

AUTHORS' CONCLUSIONS

Moderate- to high-quality evidence suggests that niacin does not reduce mortality, cardiovascular mortality, non-cardiovascular mortality, the number of fatal or non-fatal myocardial infarctions, nor the number of fatal or non-fatal strokes but is associated with side effects. Benefits from niacin therapy in the prevention of cardiovascular disease events are unlikely.

Natural Health Product Interactions with Medication

Natural health products (or dietary supplements) refer to those products found in oral dosage forms, containing 1 or more active ingredients considered to be a nutrient, an herbal product, or any other nonnutrient/nonherbal substance. Their use continues to increase in the general population and in patients seen by nutrition support clinicians. Aside from an appraisal of product safety and effectiveness, attention should be paid to the potential for these product ingredients to interact with medication. Estimates are that at least 15 million adults in the United States are at risk for supplement-drug interactions. These can occur through both pharmacokinetic and pharmacodynamic mechanisms. This review describes the influence of dietary supplements on both the disposition and the effect of medication and provides numerous examples. Patients at greatest risk for interactions are those with chronic disease, who use multiple medications-particularly those with a narrow therapeutic range-have genetic variants in drug metabolism, impaired organ function, and are at either end of the age spectrum. Knowledge of the specific effects on drug absorption, metabolism, and effect is still incomplete. Relative to the large number of possible interactions between supplements and medication, only a small number of combinations have been examined or reported. The greatest limiting factor remains the quality or reliability of the existing evidence, as many widely accepted interactions are only theoretical based either on in vitro data or known pharmacology. A distinction needs to be clearly drawn between "documented" interactions and "potential" interactions. Although drug-drug interactions have been widely recognized, supplement-drug interactions may be as important to recognize, report, and manage.

Complexity of vitamin E metabolism

Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e., when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their side-chain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a supplement or nutrient. To evaluate individual vitamin E status, the analytical procedures used for detecting and quantifying vitamin E and its metabolites are crucial. The latest methods in analytics are presented.

Metabolic response to selenium supplementation in women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

We are aware of no study examining the effects of selenium supplementation on metabolic profiles of patients with polycystic ovary syndrome (PCOS). This study was conducted to evaluate the effects of selenium supplementation on glucose homeostasis parameters and lipid concentrations in women with PCOS.

DESIGN, PATIENTS AND MEASUREMENTS

This randomized, double-blind, placebo-controlled trial was conducted among 70 women diagnosed with PCOS and aged 18-40 years old. Participants were randomly divided into two groups to receive 200 μg per day selenium supplements (N = 35) or placebo (N = 35) for 8 weeks. Fasting blood samples were taken at baseline and after 8 weeks intervention to quantify glucose, insulin and lipid concentrations.

RESULTS

After 8 weeks of intervention, subjects who received selenium supplements had significantly decreased serum insulin levels (-29·83 ± 47·29 vs +9·07 ± 77·12 pmol/l, P = 0·013), homeostasis model of assessment-insulin resistance (HOMA-IR) (-1·15 ± 1·81 vs +0·42 ± 3·09, P = 0·011), homeostatic model assessment-beta-cell function (HOMA-B) (-19·06 ± 30·95 vs +4·55 ± 47·99, P = 0·017) and increased quantitative insulin sensitivity check index (QUICKI) (+0·03 ± 0·04 vs +0·0009 ± 0·05, P = 0·032) compared with placebo. In addition, supplementation with selenium resulted in a significant reduction in serum triglycerides (-0·14 ± 0·55 vs +0·11 ± 0·30 mmol/l, P = 0·025) and VLDL-C concentrations (-0·03 ± 0·11 vs +0·02 ± 0·06 mmol/l, P = 0·025) compared with placebo.

CONCLUSIONS

In conclusion, 200 microgram per day selenium supplementation for 8 weeks among PCOS women had beneficial effects on insulin metabolism parameters, triglycerides and VLDL-C levels; however, it did not affect FPG and other lipid profiles.

Effects of formulation design on niacin therapeutics: mechanism of action, metabolism, and drug delivery

Niacin is a highly effective, lipid regulating drug associated with a number of metabolically induced side effects such as prostaglandin (PG) mediated flushing and hepatic toxicity. In an attempt to reduce the development of these adverse effects, scientists have investigated differing methods of niacin delivery designed to control drug release and alter metabolism. However, despite successful formulation of various orally based capsule and tablet delivery systems, patient adherence to niacin therapy is still compromised by adverse events such as PG-induced flushing. While the primary advantage of orally dosed formulations is ease of use, alternative delivery options such as transdermal delivery or polymeric micro/nanoparticle encapsulation for oral administration have shown promise in niacin reformulation. However, the effectiveness of these alternative delivery options in reducing inimical effects of niacin and maintaining drug efficacy is still largely unknown and requires more in-depth investigation. In this paper, we present an overview of niacin applications, its metabolic pathways, and current drug delivery formulations. Focus is placed on oral immediate, sustained, and extended release niacin delivery as well as combined statin and/or prostaglandin antagonist niacin formulation. We also examine and discuss current findings involving transdermal niacin formulations and polymeric micro/nanoparticle encapsulated niacin delivery.

The effect of nutritional supplements on serum high-density lipoprotein cholesterol and apolipoprotein A-I

One of the factors contributing to the increased risk of developing premature atherosclerosis is low plasma concentrations of high-density lipoprotein (HDL) cholesterol. Multiple potential mechanisms account for the cardioprotective effects of HDL and its main protein apolipoprotein A-I (apo A-I). Diet has an important role in modulating HDL cholesterol level. The widespread use of nutritional supplements may also alter the biology of HDL. In this review, we discuss the effect of select nutritional supplements on serum HDL cholesterol and apo A-I levels. Some nutritional supplements, such as phytosterols, soy proteins, and black seed extracts, may increase HDL cholesterol levels, while others such as cholic acid and high doses of commonly used antioxidant vitamins may downregulate HDL cholesterol levels and reduce its cardioprotection. Multiple mechanisms are involved in the regulation of HDL levels, so changes in production and clearance of HDL may have different clinical implications. The clinical relevance of the changes in HDL and apo A-I caused by nutrient supplementation needs to be tested in controlled clinical trials.

Hypercholesterolemia: its impact on ischemia-reperfusion injury

Ischemic diseases are a leading cause of death worldwide. It is becoming increasingly appreciated that atherosclerosis is a major cause of ischemia reperfusion. Hypercholesterolemia is a major risk factor for the development of atherosclerosis, and is associated with an increased incidence of ischemia reperfusion. Furthermore, elevated cholesterol levels exacerbate the vascular responses to ischemia-reperfusion, which intensifies the resulting organ dysfunction. One of the underlying features of both ischemia-reperfusion injury and hypercholesterolemia is the proinflammatory and prothrombogenic phenotype invoked in the microvasculature. This is manifested as an endothelial dysfunction, characterized by leukocyte and platelet recruitment, oxidative stress and angiotensin II receptor Type 1a activation. These common pathways of inflammation offer attractive targets for the development of drugs to combat cardiovascular disease and the associated ischemic disorders.

Mechanisms for the prevention of vitamin E excess

The liver is at the nexus of the regulation of lipoprotein uptake, synthesis, and secretion, and it is the site of xenobiotic detoxification by cytochrome P450 oxidation systems (phase I), conjugation systems (phase II), and transporters (phase III). These two major liver systems control vitamin E status. The mechanisms for the preference for α-tocopherol relative to the eight naturally occurring vitamin E forms largely depend upon the liver and include both a preferential secretion of α-tocopherol from the liver into the plasma for its transport in circulating lipoproteins for subsequent uptake by tissues, as well as the preferential hepatic metabolism of non-α-tocopherol forms. These mechanisms are the focus of this review.

Adherence, Persistence, and Predictors Associated with Early Niacin Termination

Background:

Niacin is the most effective therapy currently available to increase high-density lipoprotein cholesterol. However, adherence to niacin may be limited by a number of factors and it is important to characterize who is likely to discontinue the medicine.

Objective:

To measure adherence and persistence to niacin, estimate the influence of niacin dose on adherence, and identify factors associated with early termination of niacin.

Methods:

This retrospective study estimated adherence to niacin by calculating the medication possession ratio, persistence, number of refills, and termination proportion in a large, deidentified US health claims database consisting of 42,685 insurance-carrying adults who were new users of niacin.

Results:

We identified 29,801 new users of niacin who were not taking statins or fibric acid, 12,298 new users of niacin plus statin, 441 new users of niacin plus fibric acid, and 145 new users who initiated all 3 agents. Persistence was lowest among individuals taking less than 1 g/day and was highest among those taking niacin plus fibric acid plus statin (5.10 vs 7.17 months, respectively). However, lower niacin dose was associated with greater adherence, regardless of statin use. Termination of niacin within 1 year of initiation was significantly associated with being female or having 1 of the following conditions: peripheral vascular disease, chronic pulmonary disease, diabetes mellitus, rheumatic disease, or liver disease. Increased age, taking niacin in combination with a statin, or taking drugs from 2 or more concomitant prescription medication classes were significantly associated with a reduced likelihood of termination within 1 year.

Conclusions:

We observed relatively high adherence rates to niacin; however, most patients failed to persist with use of the drug beyond 7 months.

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.

Differing Relations to Early Atherosclerosis between Vitamin C from Supplements vs. Food in the Los Angeles Atherosclerosis Study: A Prospective Cohort Study

OBJECTIVE

To determine the relationship of vitamin c intake from supplements vs food on early atherosclerosis detected by carotid intima media thickness (IMT).

BACKGROUND

Oxidative stress and endothelial dysfunction play a critical role in the pathogenesis of atherosclerosis. Dietary vitamin C appears to have anti-oxidant properties and beneficial relations to endothelial function, yet vitamin C taken as a vitamin supplement does not appear to protect from cardiovascular events. The impact of vitamin c intake from supplements vs food on progression of atherosclerosis is unknown.

METHODS

We examined 3-year progression of carotid IMT in a randomly sampled cohort of 573 healthy women and men aged 40-60 years. Progression of carotid IMT was determined bilaterally with B-mode ultrasound at 3 examinations (1.5-year intervals). Intake of dietary vitamin C was measured by six, 24-hour recall interviews. Intake of vitamin C from vitamin supplements was measured by questionnaire in quartiles of supplement intake and no supplement. Vitamin C wasmeasured in plasma as ascorbic acid.

RESULTS

Carotid IMT progressed 10.0±16.5 μm/year (mean±SD) among all those with follow-up (n=500; 87%). For those who took vitamin C supplements, carotid IMT progression increased with dose (p-trend=0.0009). Among persons in the highest quartile (857-5000 mg/day) of vitamin C supplement intake compared to those not consuming any vitamin C supplements, carotid IMT progression increased three-fold (20.3±2.6 versus 7.6±1.8 μm/year (mean±SD); p<0.001). The adverse association of vitamin C supplement intake with carotid IMT was two-fold greater in the upper tertile of serum cholesterol compared to the lower two tertiles (p=0.01). In contrast to the adverse association of vitamin C supplements, vitamin C intake from food had a weak protective relationship on carotid IMT progression (reduced progression -5.0±1.9 μm/year; p=0.008).

CONCLUSIONS

Vitamin C supplementation is associated with accelerated early atherosclerosis measured by carotid IMT compared to a protective association with vitamin C from food. Theadverse association of vitamin C supplementation may be greater in patients with higher serum cholesterol levels. The current results provide a potential mechanistic understanding for the observed differences between Vitamin C in supplements vs food in prior studies. Given these observations,vitamin C supplementation does not appear to be currently advisable for prevention or treatment of atherosclerosis.

Supplement Use in the Prevention and Treatment of Cardiovascular Disease in the Aging Population

As the elderly population grows, so does the incidence of cardiovascular disease and the use of medications. Because of the side effects and cost of prescribed medicine, many aging individuals are seeking out alternative treatment options. Complementary and alternative medicine is gaining popularity, with about a third of people older than 60 years currently using one or more of these therapies. Many individuals are using herbs and nutritional supplements to prevent and treat a variety of cardiovascular diseases and their symptoms. Herbs and nutritional supplements are considered food by the Food and Drug Administration and are exempt from mandatory testing for their safety or efficacy. Also, many individuals consider these products as natural and do not recognize the negative impact that these alternative treatments may have on the efficacy of prescribed medications and overall health. To date, research has reported conflicting evidence as to the beneficial effects of these products; health care providers should exercise caution in recommending their use to avoid drug interactions and side effects.

Selenium supplementation in the critically ill

Selenium (Se) is an essential trace element with antioxidant, immunological, and anti-inflammatory properties, which are attributed to its presence in selenoproteins, as the 21st amino acid selenocysteine. These selenoenzymes are involved in redox signaling, antioxidant defense, thyroid hormone metabolism, and immune responses. Dietary intakes differ considerably between geographical regions, due to variability of the Se food content, leading to differences in dietary reference intakes and toxicity cautions. Critical illness with systemic inflammatory response syndrome (SIRS) is characterized by Se depletion with high morbidity and mortality. Se status correlates well with clinical outcome in SIRS and may be useful as an early predictor of survival. Several investigators have evaluated the benefits of Se supplementation for the critically ill, either as monotherapy or in an antioxidant micronutrient combination. Pharmaconutrition, with high-dose Se (from 500-1600 µg/d) involving an initial loading bolus, followed by continuous infusion, appears to be safe and efficacious, with evidence that it can improve clinical outcome by reducing illness severity, infectious complications, and decreasing mortality in the intensive care unit (ICU). We now have a clearer understanding of the pharmacokinetics of the initial and transient pro-oxidant effect of an intravenous bolus of selenite and the antioxidant effect of continuous infusion. Better biomarkers to ascertain optimum Se requirements for individual patients are now needed, and clinical practice guidelines need improvement. Nevertheless, sufficient evidence is available to consider initiating high-dose intravenous Se therapy routinely in critically ill SIRS patients, immediately on admission to the ICU.

Effect of L-arginine and selenium added to a hypocaloric diet enriched with legumes on cardiovascular disease risk factors in women with central obesity: a randomized, double-blind, placebo-controlled trial

BACKGROUND/AIMS

We aimed to discover if L-arginine and selenium alone or together can increase the effect of a hypocaloric diet enriched in legumes (HDEL) on central obesity and cardiovascular risk factors in women with central obesity.

METHODS

This randomized, double-blind, placebo-controlled trial was undertaken in 84 premenopausal women with central obesity. After a 2-week run-in period on an isocaloric diet, participants were randomly assigned to a control diet (HDEL), L-arginine (5 g/day) and HDEL, selenium (200 μg/day) and HDEL or L-arginine, selenium and HDEL for 6 weeks. Cardiovascular risk factors were assessed before intervention and 3 and 6 weeks afterwards.

RESULTS

After 6 weeks, L-arginine had significantly reduced waist circumference (WC); selenium had significantly lowered fasting concentrations of serum insulin and the homeostasis model assessment of insulin resistance index; the interaction between L-arginine and selenium significantly reduced the fasting concentration of nitric oxides (NO(x)), and HDEL lowered triglycerides (TG) and WC and significantly increased the fasting concentration of NO(x). HDEL reduced high-sensitivity C-reactive protein levels in the first half of the study and returned them to basal levels in the second half.

CONCLUSION

These data indicate the beneficial effects of L-arginine on central obesity, selenium on insulin resistance and HDEL on serum concentrations of NO(x) and TG.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Our systematic review has demonstrated that antioxidant supplements may increase mortality. We have now updated this review.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements for prevention of mortality in adults.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index Expanded, and Conference Proceedings Citation Index-Science to February 2011. We scanned bibliographies of relevant publications and asked pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Random-effects and fixed-effect model meta-analyses were conducted. Risk of bias was considered in order to minimise the risk of systematic errors. Trial sequential analyses were conducted to minimise the risk of random errors. Random-effects model meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Seventy-eight randomised trials with 296,707 participants were included. Fifty-six trials including 244,056 participants had low risk of bias. Twenty-six trials included 215,900 healthy participants. Fifty-two trials included 80,807 participants with various diseases in a stable phase. The mean age was 63 years (range 18 to 103 years). The mean proportion of women was 46%. Of the 78 trials, 46 used the parallel-group design, 30 the factorial design, and 2 the cross-over design. All antioxidants were administered orally, either alone or in combination with vitamins, minerals, or other interventions. The duration of supplementation varied from 28 days to 12 years (mean duration 3 years; median duration 2 years). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects model meta-analysis (21,484 dead/183,749 (11.7%) versus 11,479 dead/112,958 (10.2%); 78 trials, relative risk (RR) 1.02, 95% confidence interval (CI) 0.98 to 1.05) but significantly increased mortality in a fixed-effect model (RR 1.03, 95% CI 1.01 to 1.05). Heterogeneity was low with an I(2)- of 12%. In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. Meta-regression analysis did not find a significant difference in the estimated intervention effect in the primary prevention and the secondary prevention trials. In the 56 trials with a low risk of bias, the antioxidant supplements significantly increased mortality (18,833 dead/146,320 (12.9%) versus 10,320 dead/97,736 (10.6%); RR 1.04, 95% CI 1.01 to 1.07). This effect was confirmed by trial sequential analysis. Excluding factorial trials with potential confounding showed that 38 trials with low risk of bias demonstrated a significant increase in mortality (2822 dead/26,903 (10.5%) versus 2473 dead/26,052 (9.5%); RR 1.10, 95% CI 1.05 to 1.15). In trials with low risk of bias, beta-carotene (13,202 dead/96,003 (13.8%) versus 8556 dead/77,003 (11.1%); 26 trials, RR 1.05, 95% CI 1.01 to 1.09) and vitamin E (11,689 dead/97,523 (12.0%) versus 7561 dead/73,721 (10.3%); 46 trials, RR 1.03, 95% CI 1.00 to 1.05) significantly increased mortality, whereas vitamin A (3444 dead/24,596 (14.0%) versus 2249 dead/16,548 (13.6%); 12 trials, RR 1.07, 95% CI 0.97 to 1.18), vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07), and selenium (2670 dead/39,779 (6.7%) versus 1468 dead/22,961 (6.4%); 17 trials, RR 0.97, 95% CI 0.91 to 1.03) did not significantly affect mortality. In univariate meta-regression analysis, the dose of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002 to 1.001, P = 0.002).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.

Antioxidant-induced stress

Antioxidants are among the most popular health-protecting products, sold worldwide without prescription. Indeed, there are many reports showing the benefits of antioxidants but only a few questioning the possible harmful effects of these "drugs". The normal balance between antioxidants and free radicals in the body is offset when either of these forces prevails. The available evidence on the harmful effects of antioxidants is analyzed in this review. In summary, a hypothesis is presented that "antioxidant-induced stress" results when antioxidants overwhelm the body's free radicals.

Vitamins C and E: beneficial effects from a mechanistic perspective

The mechanistic properties of two dietary antioxidants that are required by humans, vitamins C and E, are discussed relative to their biological effects. Vitamin C (ascorbic acid) is an essential cofactor for α-ketoglutarate-dependent dioxygenases. Examples are prolyl hydroxylases, which play a role in the biosynthesis of collagen and in down-regulation of hypoxia-inducible factor (HIF)-1, a transcription factor that regulates many genes responsible for tumor growth, energy metabolism, and neutrophil function and apoptosis. Vitamin C-dependent inhibition of the HIF pathway may provide alternative or additional approaches for controlling tumor progression, infections, and inflammation. Vitamin E (α-tocopherol) functions as an essential lipid-soluble antioxidant, scavenging hydroperoxyl radicals in a lipid milieu. Human symptoms of vitamin E deficiency suggest that its antioxidant properties play a major role in protecting erythrocyte membranes and nervous tissues. As an antioxidant, vitamin C provides protection against oxidative stress-induced cellular damage by scavenging of reactive oxygen species, by vitamin E-dependent neutralization of lipid hydroperoxyl radicals, and by protecting proteins from alkylation by electrophilic lipid peroxidation products. These bioactivities bear relevance to inflammatory disorders. Vitamin C also plays a role in the function of endothelial nitric oxide synthase (eNOS) by recycling the eNOS cofactor, tetrahydrobiopterin, which is relevant to arterial elasticity and blood pressure regulation. Evidence from plants supports a role for vitamin C in the formation of covalent adducts with electrophilic secondary metabolites. Mechanism-based effects of vitamin C and E supplementation on biomarkers and on clinical outcomes from randomized, placebo-controlled trials are emphasized in this review.

Cholesterol esterification and atherogenic index of plasma correlate with lipoprotein size and findings on coronary angiography

We examined the association between rate of cholesterol esterification in plasma depleted of apolipoprotein B-containing lipoproteins (FER(HDL)), atherogenic index of plasma (AIP) [(log (TG/HDL-C)], concentrations, and size of lipoproteins and changes in coronary artery stenosis in participants in the HDL-Atherosclerosis Treatment Study. A total of 160 patients was treated with simvastatin (S), niacin (N), antioxidants (A) and placebo (P) in four regimens. FER(HDL) was measured using a radioassay; the size and concentration of lipoprotein subclasses were determined by nuclear magnetic resonance spectroscopy. The S+N and S+N+A therapy decreased AIP and FER(HDL), reduced total VLDL (mostly the large and medium size particles), decreased total LDL particles (mostly the small size), and increased total HDL particles (mostly the large size). FER(HDL) and AIP correlated negatively with particle sizes of HDL and LDL, positively with VLDL particle size, and closely with each other (r = 0.729). Changes in the proportions of small and large lipoprotein particles, which were reflected by FER(HDL) and AIP, corresponded with findings on coronary angiography. Logistic regression analysis of the changes in the coronary stenosis showed that probability of progression was best explained by FER(HDL) (P = 0.005). FER(HDL) and AIP reflect the actual composition of the lipoprotein spectrum and thus predict both the cardiovascular risk and effectiveness of therapy. AIP is already available for use in clinical practice as it can be readily calculated from the routine lipid profile.

The Role of Antioxidant Vitamins in Cardiovascular Disease

Objective:

To review the current data on the role of antioxidant vitamins in cardiovascular disease.

Data Sources:

Articles were obtained from a MEDLINE search covering all years. Terms used in the search included combinations of antioxidant, vitamin, vitamin E, vitamin C, beta-carotene, and cardiovascular disease. Reference lists from articles were examined for additional references.

Study Selection and Data Extraction:

Randomized clinical trials were selected and evaluated for study design and data obtained. Observational studies, meta-analyses, and basic science articles were also reviewed for background.

Data Synthesis:

The use of dietary supplements, including vitamins, minerals, and herbal products, is common among patients in the US. Vitamin E, vitamin C, and beta-carotene are all supplements with reported antioxidant activity. Because oxidative stress has been implicated in the development of cardiovascular disease, there has been significant research at the basic science level as well as observational studies and randomized placebo-controlled trials examining the potential impact of vitamin E, vitamin C, and beta-carotene in the prevention and treatment of cardiovascular disease. While basic science data and data from observational studies have identified benefit from antioxidant vitamin supplementation, randomized clinical trials have failed to support a role for antioxidant vitamin supplementation in the prevention or treatment of cardiovascular disease.

Conclusions:

Data from randomized clinical trials do not support the use of antioxidant vitamins in cardiovascular disease. Therefore, antioxidant vitamins should not be recommended to patients for prevention or treatment of cardiovascular disease.

What should medical practitioners know about the role of alternative medicines in cardiovascular disease management?

Alternative medications as a term call up many different meanings, significance, and perceptions to various medical practitioners. Some are good; others are bad. A wide range of alternative medications with relevance or connection to cardiovascular (CV) disease have been considered. While many are worthless, others have definite benefit, and at least one, chelation therapy, is associated with definite harm, significant risk, no benefit, and enrichment of the practitioners who prescribe it. The issues concerning alternative therapies will likely never be studied with randomized clinical trials due to the lack of a profit motive on the part of pharmaceutical companies--only rarely do other institutions, such as the National Institutes of Health, support medicinal studies. Basic knowledge of alternative therapies is essential for the CV specialist and other practicing physicians and other practitioners, since at least a few of their patients will take these medications regardless of medical advice. The result is that a number of these alternative medications will then interact with conventional CV medications, many times unfavorably.

Vitamin E decreases endogenous cholesterol synthesis and apo-AI-mediated cholesterol secretion in Caco-2 cells

Intestine is the gateway for newly absorbed tocopherols. This organ also plays a crucial role in cholesterol metabolism. Because tocopherols are known to impact cholesterol metabolism in the liver, we hypothesized that tocopherols could also modulate cholesterol metabolism in the intestine. This study aimed to verify this hypothesis and to unveil the mechanisms involved, using Caco-2 cells as a model of the human intestinal cell. Both α- and γ-tocopherol significantly (P<.05) decreased endogenous cholesterol synthesis and apo-AI-mediated cholesterol secretion in Caco-2 cells. Tocopherols down-regulated (P<.05) up to half of the genes involved in the cholesterol synthesis pathway, together with CYP27A1, which is involved in oxysterol production. The activity of this enzyme, as well as the levels of intracellular oxysterols, was significantly diminished by tocopherols. Finally, tocopherols significantly reduced ABCA1 mRNA levels in Caco-2 cells. We conclude that tocopherols impair the endogenous synthesis and apo-AI-mediated secretion of cholesterol in Caco-2 cells. This effect involves a down-regulation of genes involved in the cholesterol synthesis pathway, resulting in down-regulation of CYP27A1 which, in turn, diminishes oxysterol concentrations. The outcome is a decrease of LXR activity, resulting in down-regulation of ABCA1. These data reinforce the effect of α- and γ-tocopherol on cholesterol metabolism via gene expression regulation.

Effect of statins on HDL-C: a complex process unrelated to changes in LDL-C: analysis of the VOYAGER Database

The relationship between statin-induced increases in HDL cholesterol (HDL-C) concentration and statin-induced decreases in LDL cholesterol (LDL-C) is unknown. The effects of different statins on HDL-C levels, relationships between changes in HDL-C and changes in LDL-C, and predictors of statin-induced increases in HDL-C have been investigated in an individual patient meta-analysis of 32,258 dyslipidemic patients included in 37 randomized studies using rosuvastatin, atorvastatin, and simvastatin. The HDL-C raising ability of rosuvastatin, and simvastatin was comparable, with both being superior to atorvastatin. Increases in HDL-C were positively related to statin dose with rosuvastatin and simvastatin but inversely related to dose with atorvastatin. There was no apparent relationship between reduction in LDL-C and increase in HDL-C, whether analyzed overall for all statins (correlation coefficient = 0.005) or for each statin individually. Percentage increase in apolipoprotein A-I was virtually identical to that of HDL-C at all doses of the three statins. Baseline concentrations of HDL-C and triglyceride (TG) and presence of diabetes were strong, independent predictors of statin-induced elevations of HDL-C. Statins vary in their HDL-C raising ability. The HDL-C increase achieved by all three statins was independent of LDL-C decrease. However, baseline HDL-C and TGs and the presence of diabetes were predictors of statin-induced increases in HDL-C.

Niacin: a re-emerging pharmaceutical for the treatment of dyslipidaemia

Dyslipidaemias, particularly those characterized by the 'atherogenic profile' of high low-density lipoprotein-cholesterol and triglycerides and low high-density lipoprotein-cholesterol, are the major modifiable risk factor for atherosclerosis. The search for drugs to favourably alter such lipid profiles, reducing the associated morbidity and mortality, remains a major research focus. Niacin (nicotinic acid) is the most effective agent available for increasing high-density lipoprotein-cholesterol, but its use is associated with side effects that negatively affect patient compliance: these appear to arise largely as a result of production of prostaglandin D(2) and its subsequent activation of the DP(1) receptor. Desire to reduce the side effects (and improve pharmacokinetic parameters) has led to the development of a number of agonists that have differing effects, both in terms of clinical potency and the severity of adverse effects. The recent discovery of the niacin G-protein-coupled receptor HM74A (GPR109A) has clarified the distinction between the mechanism whereby niacin exerts its therapeutic effects and the mechanisms responsible for the generation of side effects. This has allowed the development of new drugs that show great potential for the treatment of dyslipidaemia. However, recent advances in understanding of the contribution of prostaglandin metabolism to vascular wall health suggest that some of the beneficial effects of niacin may well result from activation of the same pathways responsible for the adverse reactions. The purpose of this review is to emphasize that the search for agonists that show higher tolerability must take into account all aspects of signalling through this receptor.

Vitamin E Does Not Regress Hypercholesterolemic Atherosclerosis

Background: Suppression of hypercholesterolemic atherosclerosis with vitamin E is associated with reductions in oxidative stress without reductions in serum lipids. The objectives of this study were to determine if (1) vitamin E regresses hypercholesterolemic atherosclerosis; and (2) regression is associated with reductions in serum lipids and aortic oxidative stress. Methods and Results: The studies were conducted in 4 groups of rabbits: group I, control, regular diet (2 months); group II, 0.25% cholesterol diet (2 months); group III, 0.25% cholesterol diet (2 months) followed by regular diet (2 months); and group IV, 0.25% cholesterol diet (2 months) followed by regular diet with vitamin E (40 mg/kg body weight/day) (2 months). Blood samples were collected monthly for the measurement of serum lipids and oxidative stress (chemiluminescent activity of white blood cells [WBC-CL]). Aortas were removed at the end of the protocol for assessment of atherosclerotic lesions, and oxidative stress (malondialdehyde [MDA] and CL). Increases in serum lipids in group II were associated with an increase in oxidative stress and development of atherosclerosis. Serum lipids decreased to a similar extent in groups III and IV but the atherosclerotic lesions increased by 63% and 141% compared to group II. Acceleration of atherosclerosis in the rabbits on regular diet with or without vitamin E was associated with practically no change in the oxidative stress. Conclusion: These results suggest that (1) regular diet following a high-cholesterol diet decreased oxidative stress but did not induce regression of atherosclerosis; (2) vitamin E did not produce regression; and (3) regular diet with vitamin E following a high-cholesterol diet was not associated with an increase in oxidative stress but produced acceleration of atherosclerosis.

Alpha-tocopherol is ineffective in preventing the decomposition of preformed lipid peroxides and may promote the accumulation of toxic aldehydes: a potential explanation for the failure of antioxidants to affect human atherosclerosis

The decomposition of peroxidized lipids of low-density lipoprotein (LDL) has been suggested to be involved in atherosclerosis. In this study, an in vitro system with 13-hydroperoxylinoleic acid (13-HPODE) was used to determine the effects of antioxidants on its decomposition. Decomposition of 13-HPODE was not affected by alpha-tocopherol, several other antioxidants, or antioxidant enzymes. Moreover, the inclusion of alpha-tocopherol during the decomposition of 13-HPODE resulted in an accumulation of aldehydes. Further oxidation of aldehydes to carboxylic acids by a number of oxidases was prevented by alpha-tocopherol. Conversely, the formation of carboxylic acids may be conducive to plaque stabilization via immunomodulation, rapid degradation, and by calcium sequestration. Thus, the inhibition of formation of carboxylic acids could be a serious deleterious effect of antioxidant treatment. In contrast, alpha-keto acids, like pyruvic acid, promoted the conversion of 13-HPODE to 13-hydroxylinoleic acid (13-HODE) by readily undergoing decarboxylation into acetate. These observations suggest that agents that promote the reduction of lipid peroxides into lipid hydroxides could be far more effective in treating cardiovascular diseases as opposed alpha-tocopherol-like antioxidants that could affect additional steps in the oxidation cascade.

Dyslipidemia in type 2 diabetes mellitus

Dyslipidemia is one of the major risk factors for cardiovascular disease in diabetes mellitus. The characteristic features of diabetic dyslipidemia are a high plasma triglyceride concentration, low HDL cholesterol concentration and increased concentration of small dense LDL-cholesterol particles. The lipid changes associated with diabetes mellitus are attributed to increased free fatty acid flux secondary to insulin resistance. The availability of multiple lipid-lowering drugs and supplements provides new opportunities for patients to achieve target lipid levels. However, the variety of therapeutic options poses a challenge in the prioritization of drug therapy. The prevalence of hypercholesterolemia is not increased in patients with diabetes mellitus, but mortality from coronary heart disease increases exponentially as a function of serum cholesterol levels, and lowering of cholesterol with statins reduces diabetic patients' relative cardiovascular risk. Although drug therapy for dyslipidemia must be individualized, most people with diabetes mellitus are candidates for statin therapy, and often need treatment with multiple agents to achieve therapeutic goals.

Trends in dietary supplement use in a cohort of postmenopausal women from Iowa

Although it is widely known that use of dietary supplements is common in the United States, little is known about use patterns among older Americans. The authors examined trends in dietary supplement use and its contribution to total nutrient intake in the Iowa Women's Health Study cohort in 1986 (baseline) and 2004 (follow-up). The proportion of women who reported using dietary supplements increased substantially between baseline (66%) and follow-up (85%). Moreover, a substantial proportion of women reported using multiple dietary supplements, with 27% using 4 or more products in 2004. Dietary supplements contributed substantially to total intake of many nutrients at baseline, and their contribution became relatively greater at follow-up for most nutrients examined. For most nutrients, no decline in intake was observed, as might have been expected in an aging cohort. Rather, intake of many nutrients increased, primarily because of the rising use of dietary supplements. Use of dietary supplements by older individuals is of particular importance because of the potential benefits of maintaining nutrient intake levels despite potentially declining food intake. However, possible risks from obtaining a large proportion of purified nutrients from dietary supplements rather than deriving them from foods should be studied.

Vitamins and cardiovascular disease

CVD is a major cause of mortality and morbidity in the Western world. In recent years its importance has expanded internationally and it is believed that by 2020 it will be the biggest cause of mortality in the world, emphasising the importance to prevent or minimise this increase. A beneficial role for vitamins in CVD has long been explored but the data are still inconsistent. While being supported by observational studies, randomised controlled trials have not yet supported a role for vitamins in primary or secondary prevention of CVD and have in some cases even indicated increased mortality in those with pre-existing late-stage atherosclerosis. The superiority of combination therapy over single supplementation has been suggested but this has not been confirmed in trials. Studies have indicated that beta-carotene mediates pro-oxidant effects and it has been suggested that its negative effects may diminish the beneficial effects mediated by the other vitamins in the supplementation cocktail. The trials that used a combination of vitamins that include beta-carotene have been disappointing. However, vitamin E and vitamin C have in combination shown long-term anti-atherogenic effects but their combined effect on clinical endpoints has been inconsistent. Studies also suggest that vitamins would be beneficial to individuals who are antioxidant-deficient or exposed to increased levels of oxidative stress, for example, smokers, diabetics and elderly patients, emphasising the importance of subgroup targeting. Through defining the right population group and the optimal vitamin combination we could potentially find a future role for vitamins in CVD.

Obesity-related changes in high-density lipoprotein metabolism

Obesity is associated with a 3-or-more-fold increase in the risk of fatal and nonfatal myocardial infarction (1,2,3,4,5,6). The American Heart Association has reclassified obesity as a major, modifiable risk factor for coronary heart disease (7). The increased prevalence of premature coronary heart disease in obesity is attributed to multiple factors (8,9,10). A principal contributor to this serious morbidity is the alterations in plasma lipid and lipoprotein levels. The dyslipidemia of obesity is commonly manifested as high plasma triglyceride levels, low high-density lipoprotein cholesterol (HDLc), and normal low-density lipoprotein cholesterol (LDLc) with preponderance of small dense LDL particles (7,8,9,10). However, there is a considerable heterogeneity of plasma lipid profile in overweight and obese people. The precise cause of this heterogeneity is not entirely clear but has been partly attributed to the degree of visceral adiposity and insulin resistance. The emergence of glucose intolerance or a genetic predisposition to familial combined hyperlipidemia will further modify the plasma lipid phenotype in obese people (11,12,13,14,15).

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Animal and physiological research as well as observational studies suggest that antioxidant supplements may improve survival.

OBJECTIVES

To assess the effect of antioxidant supplements on mortality in primary or secondary prevention randomised clinical trials.

SEARCH STRATEGY

We searched The Cochrane Library (Issue 3, 2005), MEDLINE (1966 to October 2005), EMBASE (1985 to October 2005), and the Science Citation Index Expanded (1945 to October 2005). We scanned bibliographies of relevant publications and wrote to pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention. Included participants were either healthy (primary prevention trials) or had any disease (secondary prevention trials).

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Trials with adequate randomisation, blinding, and follow-up were classified as having a low risk of bias. Random-effects and fixed-effect meta-analyses were performed. Random-effects meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Sixty-seven randomised trials with 232,550 participants were included. Forty-seven trials including 180,938 participants had low risk of bias. Twenty-one trials included 164,439 healthy participants. Forty-six trials included 68111 participants with various diseases (gastrointestinal, cardiovascular, neurological, ocular, dermatological, rheumatoid, renal, endocrinological, or unspecified). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects meta-analysis (relative risk [RR] 1.02, 95% confidence interval [CI] 0.99 to 1.06), but significantly increased mortality in a fixed-effect model (RR 1.04, 95% CI 1.02 to 1.06). In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. In the trials with a low risk of bias, the antioxidant supplements significantly increased mortality (RR 1.05, 95% CI 1.02 to 1.08). When the different antioxidants were assessed separately, analyses including trials with a low risk of bias and excluding selenium trials found significantly increased mortality by vitamin A (RR 1.16, 95% CI 1.10 to 1.24), beta-carotene (RR 1.07, 95% CI 1.02 to 1.11), and vitamin E (RR 1.04, 95% CI 1.01 to 1.07), but no significant detrimental effect of vitamin C (RR 1.06, 95% CI 0.94 to 1.20). Low-bias risk trials on selenium found no significant effect on mortality (RR 0.91, 95% CI 0.76 to 1.09).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Vitamin A, beta-carotene, and vitamin E may increase mortality. Future randomised trials could evaluate the potential effects of vitamin C and selenium for primary and secondary prevention. Such trials should be closely monitored for potential harmful effects. Antioxidant supplements need to be considered medicinal products and should undergo sufficient evaluation before marketing.

Atherosclerosis and oxidant stress: the end of the road for antioxidant vitamin treatment?

Extensive experimental data have revealed a central role for oxidative stress in atherogenesis and suggested a potential role for 'antioxidant' treatment in cardiovascular disease (CVD) [1-11]. Experimental data, however, have not translated into clinical benefit: most antioxidant vitamin trials have failed to reduce cardiovascular morbidity and mortality [12]. Moreover, recent clinical trials have suggested that mono-therapy with certain antioxidant vitamins like vitamin E may, in fact, be detrimental [13]. As a result of the disappointing outcome of 'antioxidant' vitamin trials, some authors have questioned both the utility of 'antioxidant' treatment in CVD and the supposedly central role of oxidative stress in atherogenesis [14-19]. Other investigators, however, sustain that the beneficial effects of lipid lowering and anti-hypertensive treatment are at least, in part, due to their 'antioxidant' properties, in addition to their specific pharmacological properties [20, 21]. Oxidant stress plays a pivotal role in atherogenesis, however, the clinical promise of antioxidant vitamins has failed to translate into clinical benefit. Increasing evidence suggests that more rigorous clinical trial designs are necessary to effectively divulge antioxidant utility and that a multifaceted antioxidant approach to atherosclerosis may yield the most clinical reward. This article reviews currently available evidence on the role of oxidant stress in atherosclerosis, analyzes the results of large anti-oxidant trials, and suggests ways to investigate the true role of antioxidant treatment in the clinical setting.

Vitamin E Regulatory Mechanisms

Dietary and supplemental vitamin E is absorbed and delivered to the liver, but of the various antioxidants with vitamin E activity, only alpha-tocopherol is preferentially recognized by the alpha-tocopherol transfer protein (alpha-TTP) and is transferred to plasma, while the other vitamin E forms (e.g., gamma-tocopherol or tocotrienols) are removed from the circulation. Hepatic alpha-TTP is required to maintain plasma and tissue alpha-tocopherol concentrations. The liver is the master regulator of the body's vitamin E levels in that it not only controls alpha-tocopherol concentrations, but also appears to be the major site of vitamin E metabolism and excretion. Vitamin Es are metabolized similarly to xenobiotics; they are initially omega-oxidized by cytochrome P450s, undergo several rounds of beta-oxidation, and then are conjugated and excreted. As a result of these various mechanisms, liver alpha-tocopherol and other vitamin E concentrations are closely regulated; thus, any potential adverse vitamin E effects are limited.