Extended-release niacin/laropiprant lipid-altering consistency across patient subgroups

Niacin

Nicotinic acid and nicotinamide, collectively referred to as niacin, are nutritional precursors of the bioactive molecules nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are important cofactors for most cellular redox reactions, and as such are essential to maintain cellular metabolism and respiration. NAD also serves as a cosubstrate for a large number of ADP-ribosylation enzymes with varied functions. Among the NAD-consuming enzymes identified to date are important genetic and epigenetic regulators, e.g., poly(ADP-ribose)polymerases and sirtuins. There is rapidly growing knowledge of the close connection between dietary niacin intake, NAD(P) availability, and the activity of NAD(P)-dependent epigenetic regulator enzymes. It points to an exciting role of dietary niacin intake as a central regulator of physiological processes, e.g., maintenance of genetic stability, and of epigenetic control mechanisms modulating metabolism and aging. Insight into the role of niacin and various NAD-related diseases ranging from cancer, aging, and metabolic diseases to cardiovascular problems has shifted our view of niacin as a vitamin to current views that explore its potential as a therapeutic.

Niacin as antidyslipidemic drug

Niacin is an important vitamin (B3) that can be used in gram doses to positively modify pathogenetically relevant lipid disorders: elevated LDL cholesterol, elevated non-HDL cholesterol, elevated triglycerides, elevated lipoprotein(a), and reduced HDL cholesterol. This review reports the latest published findings with respect to niacin's mechanisms of action on these lipids and its anti-inflammatory and anti-atherosclerotic effects. In the pre-statin era, niacin was shown to have beneficial effects on cardiovascular end-points; but in recent years, two major studies performed in patients whose LDL cholesterol levels had been optimized by a statin therapy did not demonstrate an additional significant effect on these end-points in the groups where niacin was administered. Both studies have several drawbacks that suggest that they are not representative for other patients. Thus, niacin still plays a role either as an additive to a statin or as a substitute for a statin in statin-intolerant patients. Moreover, patients with elevated triglyceride and low HDL cholesterol levels and patients with elevated lipoprotein(a) concentrations will possibly benefit from niacin, although currently the study evidence for these indications is rather poor. Niacin may be useful for compliant patients, however possible side effects (flushing, liver damage) and contraindications should be taken into consideration.

Niacin, an old drug with a new twist

Niacin (nicotinic acid) has been used for decades as a lipid-lowering drug. The clinical use of niacin to treat dyslipidemic conditions is limited by its side effects. Niacin, along with fibrates, are the only approved drugs which elevate high density lipoprotein cholesterol (HDLc) along with its effects on low density lipoprotein cholesterol (LDLc) and triglycerides. Whether niacin has a beneficial role in lowering cardiovascular risk on the background of well-controlled LDLc has not been established. In fact, it remains unclear whether niacin, either in the setting of well-controlled LDLc or in combination with other lipid-lowering agents, confers any therapeutic benefit and if so, by which mechanism. The results of recent trials reject the hypothesis that simply raising HDLc is cardioprotective. However, in the case of the clinical trials, structural limitations of trial design complicate their interpretation. This is also true of the most recent Heart Protection Study 2-Treatment of HDLc to Reduce the Incidence of Vascular Events (HPS2-THRIVE) trial in which niacin is combined with an antagonist of the D prostanoid (DP) receptor. Human genetic studies have also questioned the relationship between cardiovascular benefit and HDLc. It remains to be determined whether niacin may have clinical utility in particular subgroups, such as statin intolerant patients with hypercholesterolemia or those who cannot achieve a sufficient reduction in LDLc. It also is unclear whether a potentially beneficial effect of niacin is confounded by DP antagonism in HPS2-THRIVE.

Extended-release niacin/laropiprant improves endothelial function in patients after myocardial infarction

Raising high-density lipoprotein cholesterol (HDL-C) is an important strategy for reducing residual cardiovascular risk. In the present study, we sought to assess the effect of extended-release niacin/laropiprant on endothelial function in patients after a myocardial infarction with target low-density lipoprotein cholesterol (LDL-C). In this double-blind, placebo-controlled trial, 63 men (35-60 years of age) after a myocardial infarction were randomized to either niacin/laropiprant (1000/20 mg daily for 4 weeks and 2000/40 mg daily thereafter) or placebo. Flow-mediated dilation (FMD) and nitroglycerin-induced (GTN) dilation of the brachial artery, total cholesterol (TC), LDL-C, HDL-C, triglycerides (TG), lipoprotein(a) [Lp(a)], and apolipoprotein (Apo) A1/B were measured at baseline and after 12 weeks of intervention. FMD significantly increased (from 3.9 ± 5.1 to 9.8 ± 4.4%, p < 0.001) in the niacin/laropiprant group, but not in the placebo group (4.6 ± 4.4 to 6.1 ± 4.4%, p = 0.16) (p = 0.02 for comparison of interventions). GTN dilation also increased in the niacin/laropiprant group (from 12.5 ± 6.1 to 16.7 ± 4.8%, p = 0.02), but not in the placebo group (13.4 ± 5.0 to 15.1 ± 5.2%, p = 0.18), (p = 0.60 for comparison of interventions). Niacin/laropiprant reduced TC and LDL-C (p = 0.05 for both) and increased HDL-C (p < 0.001) without influencing TG, with no changes in the placebo group. Lp(a) (p = 0.026) and ApoB (p = 0.014) were significantly lower in the niacin/laropiprant group, with no difference in the placebo group. ApoA1 did not change in either of the groups (p = 0.13; p = 0.26). FMD and GTN dilation improvements did not correlate with changes in the lipid profile. Niacin/laropiprant improves endothelium-dependent and endothelium-independent dilation of the brachial artery. This improvement does not correlate with changes in lipid parameters.

HDL, Atherosclerosis, and Emerging Therapies

This review aims to provide an overview on the properties of high-density lipoproteins (HDLs) and their cardioprotective effects. Emergent HDL therapies will be presented in the context of the current understanding of HDL function, metabolism, and protective antiatherosclerotic properties. The epidemiological association between levels of HDL-C or its major apolipoprotein (apoA-I) is strong, graded, and coherent across populations. HDL particles mediate cellular cholesterol efflux, have antioxidant properties, and modulate vascular inflammation and vasomotor function and thrombosis. A link of causality has been cast into doubt with Mendelian randomization data suggesting that genes causing HDL-C deficiency are not associated with increased cardiovascular risk, nor are genes associated with increased HDL-C, with a protective effect. Despite encouraging data from small studies, drugs that increase HDL-C levels have not shown an effect on major cardiovascular end-points in large-scale clinical trials. It is likely that the cholesterol mass within HDL particles is a poor biomarker of therapeutic efficacy. In the present review, we will focus on novel therapeutic avenues and potential biomarkers of HDL function. A better understanding of HDL antiatherogenic functions including reverse cholesterol transport, vascular protective and antioxidation effects will allow novel insight on novel, emergent therapies for cardiovascular prevention.

Consistency of extended-release niacin/laropiprant effects on Lp(a), ApoB, non-HDL-C, Apo A1, and ApoB/ApoA1 ratio across patient subgroups

BACKGROUND

According to prior analyses, extended-release niacin/laropiprant (ERN/LRPT) consistently reduces low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG) and increases high-density lipoprotein cholesterol (HDL-C) levels across a wide range of dyslipidemic patient subgroups.

OBJECTIVES

This analysis examined ERN/LRPT's consistency across four phase III, randomized, double-blind trials in improving other lipid/lipoprotein parameters associated with cardiovascular risk, across several key dyslipidemic patient subgroups.

METHODS

In three of the studies, the randomized population included patients with primary hypercholesterolemia or mixed hyperlipidemia; in the remaining study, the population included patients with type 2 diabetes mellitus. The lipid-altering consistency of ERN/LRPT's efficacy was evaluated versus the pre-defined comparator (placebo or active control) among key subgroups of sex, race (White, non-White), region (US, ex-US), baseline age (<65 years, ≥65 years), use of statin therapy (yes, no), coronary heart disease (yes, no), risk status (low, multiple, high), and type of hyperlipidemia (primary hypercholesterolemia, mixed dyslipidemia), as well as across baseline LDL-C, HDL-C, and TG levels. The consistency of the treatment effects on lipoprotein(a).[Lp(a)], apolipoprotein B (ApoB), non-HDL-C, ApoA1, and ApoB/ApoA1 ratio was evaluated by examining treatment difference estimates of the percentage change from baseline with 95% confidence intervals.

RESULTS

Treatment with ERN/LRPT produced significantly greater improvements in Lp(a), ApoB, non-HDL-C, ApoA1, and ApoB/ApoA1 ratio compared with placebo/active comparator in each study. These effects were generally consistent across key subgroups within each study.

CONCLUSION

ERN/LRPT produced lipid-altering efficacy on the parameters evaluated in four controlled studies; these effects were generally consistent across all examined subgroups. ERN/LRPT represents an effective and reliable therapeutic option for the treatment of dyslipidemia in a wide range of patient types.

CLINICAL TRIAL REGISTRATION

Registered as Clinicaltrials.gov NCT00269204, NCT00269217, NCT00479388, and NCT00485758.

The role of nutrition and body composition in peripheral arterial disease

Peripheral arterial disease (PAD) has not been as extensively investigated as other cardiovascular diseases. However, the available data suggest that nutrition-based treatment strategies have the potential to reduce the cost-economic burden of PAD substantially. Abdominal obesity is associated with PAD and prospective and cross-sectional studies have shown that a low dietary intake of folate and reduced synthesis of vitamin D are associated with an increased risk of PAD and severe walking impairment in patients who have the disease. However, dietary patterns that are associated with decreased cardiovascular risk might protect against PAD. A small number of clinical trials have provided evidence that increased intakes of niacin and insoluble fiber might be associated with decreased levels of LDL cholesterol and thrombogenic biomarkers, as well as increased serum levels of HDL cholesterol in patients with PAD. However, little evidence that antioxidants, vitamins B(6) and B(12), or essential fatty acid supplements improve clinical outcomes in these patients exists. Overall, data on the effects of nutrition, body composition, and nutritional supplementation on the risk, progression, and prognosis of PAD are scarce. Further research into these areas is required to allow the development of evidence-based nutritional guidelines for the prevention and treatment of the disease.

Niacin: the evidence, clinical use, and future directions

The use of FDA-approved niacin (nicotinic acid or vitamin B3) formulations at therapeutic doses, alone or in combination with statins or other lipid therapies, is safe, improves multiple lipid parameters, and reduces atherosclerosis progression. Niacin is unique as the most potent available lipid therapy to increase high-density lipoprotein (HDL) cholesterol and it significantly reduces lipoprotein(a). Through its action on the GPR109A receptor, niacin may also exert beneficial pleiotropic effects independent of changes in lipid levels, such as improving endothelial function and attenuating vascular inflammation. Studies evaluating the impact of niacin in statin-naïve patients on cardiovascular outcomes, or alone and in combination with statins or other lipid therapies on atherosclerosis progression, have been universally favorable. However, the widespread use of niacin to treat residual lipid abnormalities such as low HDL cholesterol, when used in combination with statins among patients achieving very low (<75 mg/dL) low-density lipoprotein cholesterol levels, is currently not supported by clinical outcome trials.