The Anticancer Potential of Peroxisome Proliferator-Activated Receptor Antagonists

The effects on cancer-cell proliferation and differentiation mediated by peroxisome proliferator-activated receptors (PPARs) have been widely studied, and pleiotropic outcomes in different cancer models and under different experimental conditions have been obtained. Interestingly, few studies report and little preclinical evidence supports the potential antitumor activity of PPAR antagonists. This review focuses on recent findings on the antitumor in vitro and in vivo effects observed for compounds able to inhibit the three PPAR subtypes in different tumor models, providing a rationale for the use of PPAR antagonists in the treatment of tumors expressing the corresponding receptors.

Pharmacological Evaluation of Novel Isonicotinic Carboxamide Derivatives as Potential Anti-Hyperlipidemic and Antioxidant Agents

Hyperlipidemia and oxidative stress have been implicated as contributing factors to the development of atherosclerosis and cardiovascular diseases (CVDs). Currently, a large number of antihyperlipidemic medications are conveniently available in the market. Nonetheless, the majority of antihyperlipidemics lack the desired safety and efficacy. Thus, the present study was undertaken to evaluate the potential effect of novel N-(benzoylphenyl)pyridine-4-carboxamide and N-(9,10-dioxo-9,10-dihydroanthracenyl)pyridine-4-carboxamide derivatives in controlling hyperlipidemia and oxidative stress using the Triton WR-1339-induced hyperlipidemic rat model for antihyperlipidemic activity and the DPPH radical scavenging assay for antioxidant activity. This study revealed the antihyperlipidemic activities of some of the newly synthesized, novel carboxamide derivatives, mainly C4 and C12 (p < 0.05). The majority of the compounds displayed a relatively low or no DPPH radical scavenging effect, with C20 possessing the best radical scavenging effect (22%) among all. This research opens the door for new potential antihyperlipidemic compounds derived from isonicotinic acid. N-(3-Benzoylphenyl)pyridine-4-carboxamide (C4) was found to have promising lipid-lowering and antioxidant effects, which may create a protective effect against CVDs, by reducing the LDL-C levels and diminishing the generation of reactive oxygen species.

Lipid lowering activity of novel N-(benzoylphenyl)pyridine-3-carboxamide derivatives in Triton WR-1339-induced hyperlipidemic rats

CONTEXT

Dyslipidemia is a major risk factor for the development of cardiovascular diseases. Many dyslipidemic patients do not achieve their target lipid levels with the currently available medications, and most of them may experience many side effects.

OBJECTIVE

The present work aimed toward identifying a new class of novel nicotinic acid-carboxamide derivatives as promising antihyperlipidemic compounds.

MATERIALS AND METHODS

Six novel N-(benzoylphenyl)pyridine-3-carboxamide derivatives were synthesized using acid chloride pathways. All structures were confirmed using ¹H-NMR, ¹³C-NMR, IR, and HRMS. The evaluation of biological activity was conducted using Triton WR-1339-induced hyperlipidemic rats model.

RESULTS

This study revealed that some of the newly synthesized novel N-(benzoylphenyl)pyridine-3-carboxamide derivatives mainly C4 and C6 possessed significant antihyperlipidemic activities on lipid components TG and TC (p value <0.05).

DISCUSSION AND CONCLUSION

This research opens the door for new potential antihyperlipidemic compounds derived from nicotinic acid that need further optimization of their biological activities.

Management of Hypertriglyceridemia for Prevention of Atherosclerotic Cardiovascular Disease

Mendelian randomization data strongly suggest that hypertriglyceridemia (HTG) causes atherosclerotic cardiovascular disease (ASCVD), and so triglyceride (TG) level-lowering treatment in HTG is now more strongly recommended to address the residual ASCVD risk than has been the case in (generally earlier) published guidelines. Fibrates are the best-established agents for TG level lowering and are generally used as first-line treatment of TG levels greater than 500 mg/dL. Statins are the best-established agents for ASCVD prevention, and so are usually used as first-line treatment of TG levels less than 500 mg/dL.

PCSK9 and its modulation

Proprotein convertase subtilisin/kexin type 9 (PCSK9), a newly-recognized protein, plays a key role in regulating cholesterol homeostasis. PCSK9 reduces hepatic low-density lipoprotein receptors (LDLRs) thereby increasing LDL-cholesterol (LDL-C). Recently, biologic and genetic research proposed several approaches to inhibit or reduce PCSK9 to improve lipid profile and cardiovascular performance in patients with dyslipidemia, particularly hypercholesterolemia. Of note, PCSK9 is a secreted protein under tight control by multiple modulators. Therefore, elucidating the factors that influence PCSK9 would enhance our understanding of PCSK9 and potentially day-to-day management of these patients at high cardiovascular risk. This review will focus on genetic variants, physiologic processes, pharmacologic agents and pathologic conditions related to PCSK9 in order to assess current and future therapeutic strategies targeting this molecule.

PCSK9 and lipid lowering drugs

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a novel circulating protein, which plays an important role in the regulation of cholesterol metabolism. Over the past decade, experimental and clinical studies have established that over- or poor expression of PCSK9 had a key impact not only on circulating PCSK9 and low density lipoprotein cholesterol (LDL-C) levels but also on cardiovascular risk and atherosclerotic process. Since the first discovery of PCSK9-related gene in 2003, factors that can influence circulating PCSK9 concentration are of great interest in a variety of medical fields, especially in pharmacology. In this review we focus on the impact of lipid-lowering drugs on circulating PCSK9 concentration and its clinical implications in order to optimal consideration for the current strategies with regard to cholesterol control.

Role of colesevelam in combination lipid-lowering therapy

Hyperlipidemia is associated with an increased risk of cardiovascular events; reducing low-density lipoprotein cholesterol (LDL-C), the primary target for cholesterol-lowering therapy, lowers the risk for such events. Although bile acid sequestrants were the first class of drugs to show a mortality benefit related to LDL-C lowering, statins are now considered first-line pharmacological therapy for reducing LDL-C levels because of their potency and their remarkable record of successful outcomes studies. Nevertheless, a substantial proportion of patients do not achieve LDL-C goals with statin monotherapy. In addition, because of adverse effects (primarily myopathy), some patients may be unwilling to use or unable to tolerate statin therapy at all or may not tolerate a full therapeutic statin dose. Also, statins may increase risk of new-onset diabetes in patients at high risk for diabetes. Thus, there remains a need for other lipid-lowering drugs to be used in combination with or in place of statins. The purpose of this article is to review available data from the literature on the use of colesevelam, a second-generation bile acid sequestrant, in combination with other lipid-lowering agents. Colesevelam has been studied in combination with statins, niacin, fibrates, and ezetimibe (including some three-drug combinations). An additive reduction in LDL-C was seen with all combinations. Other observed effects of colesevelam in combination with other lipid-lowering drugs include reductions in apolipoprotein (apo) B (with statins, fibrates, ezetimibe, statin plus niacin, or statin plus ezetimibe) and high-sensitivity C-reactive protein (with statins), and increases in apo A-I (with statins, ezetimibe, or statins plus niacin). Triglyceride levels remained relatively unchanged when colesevelam was combined with statins, fibrates, ezetimibe, or statin plus ezetimibe, and decreased with the triple combination of colesevelam, statin, and niacin. Colesevelam offset the negative glycemic effects of statins and niacin in subjects with insulin resistance or impaired glucose tolerance. Colesevelam was generally well tolerated when added to other lipid-lowering therapies in clinical trials, with gastrointestinal effects such as constipation being the predominant adverse events. Since colesevelam is not absorbed and works primarily in the intestine, it has a low potential for systemic metabolic drug-drug interactions with other drugs. Colesevelam has been shown to not interact with the lipid-lowering drugs lovastatin and fenofibrate; where interaction may be anticipated, separating dosing times by 4 h reduces the impact of any interaction. Available data confirms that colesevelam has additive cholesterol-lowering effects when used in combination with other lipid-lowering therapies. Furthermore, in some patient populations, the additional glucose-lowering effect of colesevelam may be beneficial in offsetting hyperglycemic effects of other lipid-lowering drugs.

Blocking the peroxisome proliferator-activated receptor (PPAR): an overview

Peroxisome proliferator-activated receptors (PPARs) have been studied extensively over the last few decades and have been assessed as molecular targets for the development of drugs against metabolic disorders. A rapid increase in understanding of the physiology and pharmacology of these receptors has occurred, together with the identification of novel chemical structures that are able to activate the various PPAR subtypes. More recent evidence suggests that moderate activation of these receptors could be favorable in pathological situations due to a decrease in the side effects brought about by PPAR agonists. PPAR partial agonists and antagonists are interesting tools that are currently used to better elucidate the biological processes modulated by this family of nuclear receptors. Herein we present an overview of the various molecular structures that are able to block each of the PPAR subtypes, with a focus on promising therapeutic applications.

Pravastatin and fenofibrate in combination (Pravafenix(®)) for the treatment of high-risk patients with mixed hyperlipidemia

Pravafenix(®) is a fixed-dose combination of pravastatin 40 mg and fenofibrate 160 mg. The rationale for the use of Pravafenix is based on the increased residual cardiovascular risk observed for high-risk patients with either increased triglycerides or low HDL cholesterol levels despite statin monotherapy. This article reviews the current available information on the pharmacology, clinical efficacy and safety of Pravafenix. Pravafenix is recommended to be taken with food in the evening. In clinical trials, Pravafenix consistently produces complementary benefits on the overall atherogenic lipid profile of high-risk patients with mixed hyperlipidemia not controlled by either pravastatin 40 mg or simvastatin 20 mg. Within the limitations of the database, Pravafenix seems to be well tolerated up to 64 weeks, with an overall tolerability and safety profile consistent with findings generally observed with fenofibrate treatment. In particular, no myopathy or rhabdomyolysis has been reported. The actual European indication is restricted to high-risk patients with mixed hyperlipidemia whose LDL cholesterol levels are adequately controlled on pravastatin 40 mg monotherapy. Whether Pravafenix confers additional cardiovascular benefits in high-risk patients treated with a statin remains to be determined.

Fenofibrate: a review of its use in dyslipidaemia

Fenofibrate is a fibric acid derivative indicated for the treatment of severe hypertriglyceridaemia and mixed dyslipidaemia in patients who have not responded to nonpharmacological therapies. The lipid-modifying effects of fenofibrate are mediated by the activation of peroxisome proliferator-activated receptor-α. Fenofibrate also has nonlipid, pleiotropic effects (e.g. reducing levels of fibrinogen, C-reactive protein and various pro-inflammatory markers, and improving flow-mediated dilatation) that may contribute to its clinical efficacy, particularly in terms of improving microvascular outcomes. Fenofibrate improves the lipid profile (particularly triglyceride [TG] and high-density lipoprotein-cholesterol [HDL-C] levels) in patients with dyslipidaemia. Compared with statin monotherapy, fenofibrate monotherapy tends to improve TG and HDL-C levels to a significantly greater extent, whereas statins improve low-density lipoprotein-cholesterol (LDL-C) and total cholesterol levels to a significantly greater extent. Fenofibrate is also associated with promoting a shift from small, dense, atherogenic LDL particles to larger, less dense LDL particles. Combination therapy with a statin plus fenofibrate generally improves the lipid profile to a greater extent than monotherapy with either agent in patients with dyslipidaemia and/or type 2 diabetes mellitus or the metabolic syndrome. In the pivotal FIELD and ACCORD trials in patients with type 2 diabetes, fenofibrate did not significantly reduce the risk of coronary heart disease events to a greater extent than placebo, and simvastatin plus fenofibrate did not significantly reduce the risk of major cardiovascular (CV) events to a greater extent than simvastatin plus placebo. However, the risk of some nonfatal macrovascular events and the incidence of certain microvascular outcomes were reduced significantly more with fenofibrate than with placebo in the FIELD trial, and in the ACCORD trial, patients receiving simvastatin plus fenofibrate were less likely to experience progression of diabetic retinopathy than those receiving simvastatin plus placebo. Subgroup analyses in the FIELD and ACCORD Lipid trials indicate that fenofibrate is of the greatest benefit in decreasing CV events in patients with atherogenic dyslipidaemia. Fenofibrate is generally well tolerated when administered alone or in combination with a statin. Thus, in patients with dyslipidaemia, particularly atherogenic dyslipidaemia, fenofibrate is a useful treatment option either alone or in combination with a statin.

Fenofibrate: a review of its lipid-modifying effects in dyslipidemia and its vascular effects in type 2 diabetes mellitus

Fenofibrate is a fibric acid derivative with lipid-modifying effects that are mediated by the activation of peroxisome proliferator-activated receptor-α. Fenofibrate also has a number of nonlipid, pleiotropic effects (e.g. reducing levels of fibrinogen, C-reactive protein, and various pro-inflammatory markers, and improving flow-mediated dilatation) that may contribute to its clinical efficacy, particularly in terms of improving microvascular outcomes. The beneficial effects of fenofibrate on the lipid profile have been shown in a number of randomized controlled trials. In primary dyslipidemia, fenofibrate monotherapy consistently decreased triglyceride (TG) levels to a significantly greater extent than placebo; significantly greater increases in high-density lipoprotein cholesterol (HDL-C) levels and significantly greater reductions in low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels were also seen in some trials. Monotherapy with fenofibrate or gemfibrozil had generally similar effects on TG and HDL-C levels, although in one trial, TC and LDL-C levels were reduced to a significantly greater extent with fenofibrate than with gemfibrozil. Fenofibrate monotherapy tended to improve TG and HDL-C levels to a significantly greater extent than statin monotherapy in primary dyslipidemia, whereas statin monotherapy decreased LDL-C and TC levels to a significantly greater extent than fenofibrate monotherapy. Fenofibrate also had a beneficial effect on atherogenic dyslipidemia in patients with the metabolic syndrome or type 2 diabetes mellitus, reducing TG levels, tending to increase HDL-C levels, and promoting a shift to larger low-density lipoprotein particles. In terms of cardiovascular outcomes, fenofibrate did not reduce the risk of coronary heart disease (CHD) events to a greater extent than placebo in patients with type 2 diabetes in the FIELD trial. However, the risk of some nonfatal macrovascular events (e.g. nonfatal myocardial infarction, revascularization) and certain microvascular outcomes (e.g. amputation, first laser therapy for diabetic retinopathy, progression of albuminuria) was reduced to a significantly greater extent with fenofibrate than with placebo. Subgroup analysis revealed a significant reduction in the cardiovascular disease (CVD) event rate among fenofibrate recipients in the subgroup of patients with marked hypertriglyceridemia or marked dyslipidemia at baseline. In the ACCORD Lipid trial, there were no significant differences between patients with type 2 diabetes and a high risk of CVD events who received fenofibrate plus simvastatin and those who received placebo plus simvastatin for any of the primary or secondary cardiovascular outcomes. However, fenofibrate plus simvastatin was of benefit in patients who had markedly high TG levels and markedly low HDL-C levels at baseline. In addition, fenofibrate plus simvastatin slowed the progression of diabetic retinopathy. Fenofibrate is generally well tolerated. Common adverse events included increases in transaminase levels that were usually transient, minor, and asymptomatic, and gastrointestinal signs and symptoms. In conclusion, monotherapy with fenofibrate remains a useful option in patients with dyslipidemia, particularly in atherogenic dyslipidemia characterized by high TG and low HDL-C levels.

Fibrates: old drugs with a new role in type 2 diabetes prevention?

The incidence of type 2 diabetes is increasing throughout the world resulting in a huge growth in demands on health services. Despite advances in treatment, complications still occur. Prevention of type 2 diabetes or delaying its onset is therefore a desirable goal. In trials, lifestyle measures have been partially successful but continuing adherence is difficult. A number of drugs have been tried with varying success. Those people who develop type 2 diabetes have been found to have a more atherogenic lipid profile and to be more insulin resistant, than those who do not, and at increased cardiovascular risk. Fibrates, which are safe and cheap, could help to correct these abnormalities at an early stage and reduce cardiovascular risk. They would seem a suitable option for prevention of type 2 diabetes. Evidence is presented to suggest that the fibrates, in particular bezafibrate, could have a role in prevention of type 2 diabetes in those at high risk and that a randomised trial would seem justified.

Effects of currently prescribed LDL-C-lowering drugs on PCSK9 and implications for the next generation of LDL-C-lowering agents

Background

During the past decade, proprotein convertase subtilisin kexin type 9 (PCSK9) has been identified as a key regulator of serum LDL-cholesterol (LDL-C) levels. PCSK9 is secreted by the liver into the plasma and binds the hepatic LDL receptor, causing its subsequent degradation. In humans, gain-of-function mutations in PCSK9 cause a form of familial hypercholesterolemia that manifests with dramatically increased serum levels of LDL-C, while loss-of-function mutations in PCSK9 are associated with significantly decreased LDL-C and cardiovascular risk.

Results

Initial studies in animals and cultured cells demonstrated that statins increased PCSK9 mRNA expression, resulting in many research groups exploring the effect of statins on PCSK9 levels in humans. We first reported that statins increased human PCSK9 circulating protein levels. Additional researchers subsequently confirmed these observations, further prompting many laboratories including our own to examine the effect of other lipid lowering medications on PCSK9 levels. Our observation that fenofibrate (200 mg/day) significantly increased PCSK9 levels was confirmed by another laboratory, and an additional group demonstrated that ezetimibe also increased PCSK9 levels.

Conclusions

It has become clear that the major classes of commonly prescribed lipid-lowering medications increase serum PCSK9 levels. These observations almost certainly explain why these agents are not more effective in lowering LDL-C and suggest that efforts should be made toward the development of new LDL-C lowering medications that either do not increase circulating PCSK9 levels or work through decreasing or inhibiting PCSK9.

Niacin and fibrates in atherogenic dyslipidemia: pharmacotherapy to reduce cardiovascular risk

Although statin therapy represents a cornerstone of cardiovascular disease (CVD) prevention, a major residual CVD risk (60-70% of total relative risk) remains, attributable to both modifiable and non-modifiable risk factors. Among the former, low levels of HDL-C together with elevated triglyceride (TG)-rich lipoproteins and their remnants represent major therapeutic targets. The current pandemic of obesity, metabolic syndrome, and type 2 diabetes is intimately associated with an atherogenic dyslipidemic phenotype featuring low HDL-C combined with elevated TG-rich lipoproteins and small dense LDL. In this context, there is renewed interest in pharmacotherapeutic strategies involving niacin and fibrates in monotherapy and in association with statins. This comprehensive, critical review of available data in dyslipidemic subjects indicates that niacin is more efficacious in raising HDL-C than fibrates, whereas niacin and fibrates reduce TG-rich lipoproteins and LDL comparably. Niacin is distinguished by its unique capacity to effectively lower Lp(a) levels. Several studies have demonstrated anti-atherosclerotic action for both niacin and fibrates. In contrast with statin therapy, the clinical benefit of fibrates appears limited to reduction of nonfatal myocardial infarction, whereas niacin (frequently associated with statins and/or other agents) exerts benefit across a wider range of cardiovascular endpoints in studies involving limited patient numbers. Clearly the future treatment of atherogenic dyslipidemias involving the lipid triad, as exemplified by the occurrence of the mixed dyslipidemic phenotype in metabolic syndrome, type 2 diabetes, renal, and auto-immune diseases, requires integrated pharmacotherapy targeted not only to proatherogenic particles, notably VLDL, IDL, LDL, and Lp(a), but also to atheroprotective HDL.

Ezetimibe plus fenofibrate: a new combination therapy for the management of mixed hyperlipidaemia?

Mixed hyperlipidaemia is an important risk factor for the development of cardiovascular disease. The global management of mixed hyperlipidaemia is often more difficult than the treatment of pure hypercholesterolaemia in terms of goal attainments. Despite the significant clinical benefits provided by statins, many patients with mixed hyperlipidaemia do not achieve their recommended low-density and non-high-density lipoprotein cholesterol target goals with statin monotherapy. The combination of ezetimibe plus fenofibrate is a new alternative to improve the overall atherogenic lipid profile of patients with mixed hyperlipidaemia. However, the absence of comparative data with statin monotherapy and of long-term clinical studies suggests reservation of the combination of ezetimibe plus fenofibrate as a second-line therapy. Nevertheless, this combination therapy of ezetimibe plus fenofibrate seems particularly useful for patients with a poor response or intolerance to statin monotherapy.