An overview of lipid-lowering drugs

Molecular genetic characterization of a cluster in A. terreus for biosynthesis of the meroterpenoid terretonin

Meroterpenoids are natural products produced from polyketide and terpenoid precursors. A gene targeting system for A. terreus NIH2624 was developed, and a gene cluster for terretonin biosynthesis was characterized. The intermediates and shunt products were isolated from the mutant strains, and a pathway for terretonin biosynthesis is proposed. Analysis of two meroterpenoid pathways corresponding to terretonin in A. terreus and austinol in A. nidulans reveals that they are closely related evolutionarily.

The role of bile acid sequestrants in the management of type 2 diabetes mellitus

The prevalence of type 2 diabetes (T2DM) and cardiovascular disease (CVD) continues to escalate globally. There is now abundant clinical trial evidence that the optimal treatment of CVD risk factors, with lifestyle changes aimed at weight loss in most patients, and pharmacologic management of dyslipidemia and hyperglycemia, can help mitigate the CVD burden. Yet more than 50% of patients are still not achieving glycosylated hemoglobin (HbA1c) and low-density lipoprotein cholesterol (LDL-C) goals. Over the past 15 years, many novel and emerging drugs have made it possible to achieve optimal glycemic control, generally in combination therapy, without untoward effects of weight gain, hypoglycemia, and other adverse effects with traditional agents. Although the long-term efficacy and safety of some of the newer classes of agents are yet to be determined, bile acid sequestrants represent a unique long-standing class of agents. These drugs have the dual efficacy in glycemic control and LDL-C reduction, and an established record of long-term safety. Colesevelam HCl is the only drug approved for this dual indication and is an adjunct in the treatment of both hyperglycemia and hypercholesterolemia that frequently co-exist in adults with T2DM.

Molecular mechanisms of toxicity of simvastatin, widely used cholesterol-lowering drug. A review

Statins are widely used and well tolerated cholesterol-lowering drugs, and when used for therapy purposes reduce morbidity and mortality from coronary heart disease. Simvastatin is one of nine known statins, specific inhibitors of hepatic enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the rate-limiting step of cholesterol biosynthesis, and is believed to reduce plasma cholesterol levels by decreasing the activity of this enzyme. Statin drugs represent the major improvement in the treatment of hypercholesterolemia that constitutes the main origin of atherosclerosis, leading to coronary heart disease. Although statins are generally safe, minor and severe adverse reactions are well known complications of statin use. Adverse events associated with simvastatin therapy are uncommon, but potentially serious. In this review some details about statins including their adverse effects in humans and animals, the effects of simvastatin on various intracellular and mitochondrial processes, and molecular mechanisms underlying simvastatin cytotoxicity are discussed.

Session 4: CVD, diabetes and cancer A dietary portfolio for management and prevention of heart disease

CHD is the leading cause of worldwide mortality. The prevalence of heart disease has been linked to the adoption of a sedentary lifestyle and the increased dietary dependence on saturated fats from animal sources and the intake of refined foods. Elevated blood cholesterol level is one of the major risk factors for CHD. While cholesterol-lowering drug therapy (statins) has been effective in reducing the risk of heart disease, there are those individuals who are unwilling or because of muscle pains or raised levels of liver or muscle enzymes are unable to take cholesterol-lowering medication. Fortunately, there is evidence linking a number of dietary components to CHD risk reduction. The strength of this evidence has prompted various regulatory bodies to advocate diet as the first line of defence for primary prevention of heart disease. It was therefore decided to combine four dietary components that have been shown to lower blood cholesterol concentrations (nuts, plant sterols, viscous fibre and vegetable protein) in a dietary portfolio in order to determine whether the combined effect is additive. In a metabolically-controlled setting this dietary portfolio has proved to be as effective as a starting dose of a first-generation statin cholesterol-lowering medication in reducing the risk of CHD. The dietary portfolio has also been shown to be effective in sustaining a clinically-significant effect in the long term under a ‘real-world’ scenario. However, success of the diet depends on compliance and despite the accessibility of the foods adherence has been found to vary greatly. Overall, the evidence supports the beneficial role of the dietary portfolio in reducing blood cholesterol levels and CHD risk.

A systematic review of LDL apheresis in the treatment of cardiovascular disease

LDL apheresis is an effective method of lowering low-density lipoprotein (LDL) concentration in patients with familial hypercholesterolemia (FH) who are either refractory to treatment or intolerant of medical therapy. We searched the medical literature through July 2004 using PubMed and Medline and the search terms "LDL apheresis", "cardiovascular", and "disease" to identify apheresis techniques and to evaluate their effects on cardiovascular pathophysiology and clinical outcomes. We conclude that LDL apheresis reduces cardiovascular events in hypercholesterolemic patients and may be an effective treatment for other vascular diseases including cholesterol embolic disease, focal segmental glomerular sclerosis, sudden hearing loss, and age-related macular degeneration.

Assessment of the longer-term effects of a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia

BACKGROUND

Cholesterol-lowering foods may be more effective when consumed as combinations rather than as single foods.

OBJECTIVES

Our aims were to determine the effectiveness of consuming a combination of cholesterol-lowering foods (dietary portfolio) under real-world conditions and to compare these results with published data from the same participants who had undergone 4-wk metabolic studies to compare the same dietary portfolio with the effects of a statin.

DESIGN

For 12 mo, 66 hyperlipidemic participants were prescribed diets high in plant sterols (1.0 g/1000 kcal), soy protein (22.5 g/1000 kcal), viscous fibers (10 g/1000 kcal), and almonds (23 g/1000 kcal). Fifty-five participants completed the 1-y study. The 1-y data were also compared with published results on 29 of the participants who had also undergone separate 1-mo metabolic trials of a diet and a statin.

RESULTS

At 3 mo and 1 y, mean (+/-SE) LDL-cholesterol reductions appeared stable at 14.0 +/- 1.6% (P < 0.001) and 12.8 +/- 2.0% (P < 0.001), respectively (n = 66). These reductions were less than those observed after the 1-mo metabolic diet and statin trials. Nevertheless, 31.8% of the participants (n = 21 of 66) had LDL-cholesterol reductions of >20% at 1 y (x +/- SE: -29.7 +/- 1.6%). The LDL-cholesterol reductions in this group were not significantly different from those seen after their respective metabolically controlled portfolio or statin treatments. A correlation was found between total dietary adherence and LDL-cholesterol change (r = -0.42, P < 0.001). Only 2 of the 26 participants with <55% compliance achieved LDL-cholesterol reductions >20% at 1 y.

CONCLUSIONS

More than 30% of motivated participants who ate the dietary portfolio of cholesterol-lowering foods under real-world conditions were able to lower LDL-cholesterol concentrations >20%, which was not significantly different from their response to a first-generation statin taken under metabolically controlled conditions.

Meta-Analysis of Natural Therapies for Hyperlipidemia: Plant Sterols and Stanols versus Policosanol

STUDY OBJECTIVE

To compare the efficacy and safety of plant sterols and stanols as well as policosanol in the treatment of coronary heart disease, as measured by a reduction in low-density lipoprotein cholesterol (LDL) levels.

DESIGN

Systematic review and meta-analysis of randomized controlled trials.

PATIENTS

A total of 4596 patients from 52 eligible studies.

MEASUREMENTS AND MAIN RESULTS

We searched MEDLINE, EMBASE, the Web of Science, and the Cochrane Library from January 1967-June 2003 to identify pertinent studies. Reduction of LDL levels was the primary end point; effects on other lipid parameters and withdrawal of study patients due to adverse effects were the secondary end points. Weighted estimates of percent change in LDL were -11.0% for plant sterol and stanol esters 3.4 g/day (range 2-9 g/day [893 patients]) versus -2.3% for placebo (769 patients) in 23 eligible studies, compared with -23.7% for policosanol 12 mg/day (range 5-40 mg/day [1528 patients]) versus -0.11% for placebo (1406 patients) in 29 eligible studies. Cumulative p values were significantly different from placebo for both (p<0.0001). The net LDL reduction in the treatment groups minus that in the placebo groups was greater with policosanol than plant sterols and stanols (-24% versus -10%, p<0.0001). Policosanol also affected total cholesterol, high-density lipoprotein cholesterol (HDL), and triglyceride levels more favorably than plant sterols and stanols. Policosanol caused a clinically significant decrease in the LDL:HDL ratio. Pooled withdrawal rate due to adverse effects and combined relative risk for patients who withdrew were 0% and 0.84, respectively (95% confidence interval [CI] 0.36-1.95, p=0.69), for plant sterols and stanols across 20 studies versus 0.86% and 0.31, respectively (95% CI 0.20-0.48, p<0.0001), for policosanol across 28 studies.

CONCLUSION

Plant sterols and stanols and policosanol are well tolerated and safe; however, policosanol is more effective than plant sterols and stanols for LDL level reduction and more favorably alters the lipid profile, approaching antilipemic drug efficacy.

Hepatotoxicity of hypolipidemic drugs

Dyslipidemic conditions and their cardiovascular related complications are common. Effective primary and secondary prevention strategies include therapies to lower LDL and total cholesterol and to increase HDL. Further, it seems that there is a need for therapeutic reduction in triglycerides as it emerges as an independent risk factor for CVD. Many clinical trials have been designed to evaluate pharmacologic compounds in the treatment of the dyslipidemias and they seem to have shown a safe profile, both in the experiment phases and in post-marketing observation studies. Nevertheless, sporadic reports of hepatotoxicity with statins and niacin still arise (Table 2). Although routine hepatic biochemical test monitoring is recommended, the cost-effectiveness is questionable because often these reactions are idiosyncratic and may not be identified by this routine screening. The risk/benefit ratio is in favor of using these medications in individuals at risk. There is no evidence to suggest intrinsic hepatotoxic activity as such. Drugs that lower triglycerides such as fibrates, have been observed to improve hepatic biochemical tests, although in small series. This leads to speculation whether treatment with fibrates would be beneficial for non-alcoholic fatty liver disease (NAFLD), a condition that is emerging as one of enormous magnitude.

Evaluation of the phototoxic properties of some hypolipidemics in vitro: fenofibrate exhibits a prominent phototoxic potential in the UVA and UVB region

As some fibric acid derivatives have been reported to exhibit photosensitizing effects in vivo, the antilipemic drugs fenofibrate, bezafibrate, clofibrate, and gemfibrozil were tested for their phototoxic potential in vitro by a photohemolysis test using human erythrocytes and different irradiation sources. In this system only fenofibrate revealed strong phototoxic properties, which were dependent both on the drug concentration and the irradiation doses. Above a surface dose of 40 J/cm2 UVA of an UVA (320-400 nm)-rich irradiation source or 1.6 J/cm2 UVB/0.8 J/cm2 UVA of an UVB (280-320 nm)-rich irradiation source human red blood cells were completely photohemolysed in the presence of fenofibrate. Bezafibrate- and gemfibrozil-induced photohemolysis remained beneath 10%, and clofibrate showed no phototoxicity at all. As the phototoxic potential of fenofibrate lies in the UVB and UVA range, this might be of relevance with regard to clinical photosensitivity.

Effect of a synthetic prostaglandin E2 analogue, RS-86505-007, on plasma lipids and lipoproteins in patients with moderate hypercholesterolaemia: efficacy and tolerance of treatment and response in different apolipoprotein polymorphism groups

A double-blind, placebo-controlled ascending dose trial was carried out to evaluate the hypocholesterolaemic efficacy and tolerance of RS-86505-007, a prostaglandin E2 analogue, in moderately hypercholesterolaemic patients. Twenty-four patients received an oral dose of RS-86505-007 3 micrograms t.i.d. and a separate group of 26 patients 6 micrograms t.i.d. for 6 weeks. Plasma total and low-density lipoprotein (LDL) cholesterol concentrations decreased after 2 weeks of treatment, and the reductions were dose dependent. After 6 weeks of treatment (6 micrograms t.i.d.), the reductions from baseline in total and LDL cholesterol concentration were 14.6% and 18.5%, respectively. No changes in the plasma concentration of triglycerides or high-density lipoprotein (HDL) cholesterol were observed. RS-86505-007 tended to reduce total and LDL cholesterol concentrations less in patients with the epsilon 4 allele of the apolipoprotein E than in those with epsilon 3 allele. In contrast, the XbaI or EcoRI polymorphisms of the apolipoprotein B gene seemed to have no effect on the hypocholesterolaemic efficacy of the drug. The drug had no effect on the lipoprotein (a) concentration. Sixty-three percent of patients receiving 3 micrograms t.i.d. and 81% receiving 6 micrograms t.i.d. had adverse events, two-thirds of which related to the gastrointestinal tract. One patient in the 3-micrograms group and three patients in the 6-micrograms group terminated the study prematurely due to adverse effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug treatment of dyslipoproteinemia

This article has focused on the appropriate indications for lipid-lowering drugs in adult patients with different lipoprotein disorders, which we have divided into primary hypercholesterolemia, combined hyperlipidemia,and hypertriglyceridemia. The mechanism of action, efficacy, and safety profile of the major drugs have been reviewed, and based on this information, we have presented our views on the appropriate drugs of first choice and appropriate second-choice agents for treatment of adult patients with different dyslipidemias. The rationale for the use of hypolipidemic drugs is strongest in patients with hyperlipidemia who concurrently have evidence for coronary or peripheral vascular disease, in whom the goal of secondary prevention is to retard further progression of atherosclerosis and potentially induce some regression, whereas in selected high-risk patients without evidence of atherosclerosis, the goals of therapy are to prevent the premature development of CAD or, in patients with severe hypertriglyceridemia, prevent the adverse sequelae of hepatomegaly, splenomegaly, and potentially pancreatitis. We have focused on the use of hypolipidemic drugs in adult patients, and the guidelines discussed are not appropriate for use in children with hyperlipidemia, in whom drug therapy should be undertaken selectively and in consultation with a lipid specialist. Many areas of controversy in the use of lipid-lowering drugs remain to be addressed by future studies; these include the use of lipid-lowering drugs in patients with secondary causes of hyperlipidemia (e.g., the nephrotic syndrome), the use of lipid-lowering drugs in women, and recommendations for drug therapy in older patients.

Therapeutic management of triglycerides: an international perspective

Current recommendations from various international expert committees generally concur in their definitions of borderline and high triglyceride levels, with small but important differences between recommendations in the definition of normal levels. However, population-based data on triglyceride levels are poorly developed in most countries, making difficult any international comparisons of prevalences of hypertriglyceridemia using the new definitions. However, it is probable that there should be considerable differences in the prevalence of hypertriglyceridemia, probably due to a mixture of genetic and environmental influences. The management of hypertriglyceridemia must continue to emphasize the detection and correction of secondary causes, even though the specific secondary causes may vary between countries. Dietary and exercise interventions must deal with local customs and resources, including striking international differences in alcohol consumption. Pharmacologic therapies will likely increase in use if they follow the trends in countries with available data. Although various drugs are available, nicotinic acid and fibric acid derivatives remain the drugs of choice. Considerably more research is needed to describe these international differences in etiology, prevalence and management practices of hypertriglyceridemia.

A comparative review of the adverse effects of treatments for hyperlipidaemia

Various lipid-lowering drugs have been shown to reduce serum cholesterol and serum triglycerides effectively. In view of trials indicating that lipid-lowering drugs may reduce cardiac morbidity and mortality but not the overall mortality in the study group, increased attention must be focused on potential harmful side effects during treatment with these agents. The adverse effects of many of the principal drugs in this category are discussed. Gastrointestinal symptoms, usually self-limited and reversible, are the most common side effects. Potential harmful adverse effects include drug interactions (cholestyramine), myopathy and hepatic injury (HMG-CoA reductase inhibitors), and increased gallstone formation and ventricular arrhythmias (clofibrate). Not all lipid-lowering drugs have been studied adequately on a long term basis, so that medications given for an indefinite period must be reevaluated frequently. However, there are several agents that lower serum lipid levels effectively and that have been used for more than 20 years without serious side effects.

Simvastatin. A review of its pharmacological properties and therapeutic potential in hypercholesterolaemia

Simvastatin (epistatin; synvinolin; MK 733), an HMG-CoA reductase inhibitor, acts by decreasing cholesterol synthesis and by increasing low density lipoprotein (LDL) catabolism via increased LDL receptor activity. In patients with heterozygous familial and nonfamilial hypercholesterolaemia, orally administered simvastatin 10 to 40mg once daily reduces plasma total and LDL-cholesterol concentrations by about 30 to 45%. It also produces a beneficial moderate decrease in plasma triglycerides and a small, although significant, increase in high density lipoprotein (HDL)-cholesterol. Like many other hypocholesterolaemic agents simvastatin does not appear useful in patients with homozygous familial hypercholesterolaemia who lack LDL receptors. The hypocholesterolaemic activity of simvastatin is greater than that of the bile acid sequestrants, probucol and the fibrates. Combined administration of simvastatin with bile acid sequestrants results in further reductions in plasma cholesterol levels beyond those seen with either drug alone. Simvastatin appears well tolerated in the short to medium term, but its long term tolerability needs to be confirmed. No comparisons of simvastatin and other HMG-CoA reductase inhibitors have been reported. As yet there have been few investigations to determine the impact of simvastatin or other HMG-CoA reductase inhibitors on cardiovascular events relative to their hypocholesterolaemic effects, but at least one such trial is ongoing. Simvastatin, like other HMG-CoA reductase inhibitors, has considerable potential advantages over other classes of hypocholesterolaemic agents, i.e. the magnitude of its cholesterol-lowering effect and convenience of administration. If further study confirms long term tolerability and an impact on cardiac mortality and morbidity, then simvastatin and others of its class should offer a significant new approach to the treatment of hypercholesterolaemia.