Drug treatment of lipid disorders

Statins: effective antiatherosclerotic therapy

BACKGROUND

Statins are the most effective agents currently available for lowering plasma levels of low-density lipoprotein cholesterol (LDL-C) and are the mainstay of therapy for hyperlipidemia. The statins are highly liver-selective, inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a key enzyme in the synthesis of cholesterol. Several large, controlled clinical trials have confirmed significant reductions in rates of coronary heart disease morbidity and death with long-term statin therapy in patients with mild to severe hypercholesterolemia.

METHODS AND RESULTS

This review article is based on a literature search of more than 60 relevant articles from peer-reviewed journals. Search engines included Medline and Embase. In surveying clinical and angiographic evidence, we found that statins appear to reduce the incidence of coronary events by slowing the progression of atherosclerosis and preventing atheromatous lesion formation. We found that the 6 statins currently marketed-atorvastatin, cerivastatin, fluvastatin, lovastatin, pravastatin, and simvastatin-differ in their inhibitory action on the HMG-CoA reductase enzyme.

CONCLUSIONS

The use of more potent statins such as atorvastatin and simvastatin affords greater lowering of LDL-C and triglyceride levels, allowing more patients to achieve target goals. The question of how low LDL-C levels should be lowered will be answered by ongoing clinical trials.

Use of statins and blood pressure control in treated hypertensive patients with hypercholesterolemia

High serum cholesterol has been frequently reported in patients with arterial hypertension in whom it might influence the blood pressure control. The aim of this study was to compare the extent of blood pressure changes in 41 patients with hypertension and hypercholesterolemia, taking antihypertensive drugs and treated for 3 months with statins (HC-S; pravastatin or simvastatin) and compared with matched controls with high (HC-D; 44) or normal serum cholesterol (NC-D; 45) undergoing antihypertensive treatment combined with dietary treatment alone. After 3 months of follow-up, a greater reduction of systolic (SBP) and diastolic (DBP) blood pressure values was observed in HC-S patients (ASBP/DBP, -11.3 +/-3/-10.6 +/- 2%) when compared with both HC-D (deltaSBP/DBP, -6.6 +/- 2/-6.1 +/- 2%; p < 0.05) and NC-D (deltaSBP/DBP, -6.9 +/- 2/-6.8 +/- 1.5%; p < 0.05). In statin-treated patients, a slight linear relation has been found between the percentage changes in DBP and those in plasma total cholesterol (R = 0.37, p = 0.043), whereas no relation was found with SBP changes (R =0.11; p = 0.35). In conclusion, the results of this study demonstrate that the use of statins in combination with antihypertensive drugs can improve blood pressure control in patients with uncontrolled hypertension and high serum cholesterol levels. The additional blood pressure reduction observed in patients treated with statins is clinically relevant and only partially related to the lipid-lowering effect.

Cardiovascular risk in diabetes: a brief review

Cardiovascular disease (CVD) is the major cause of the morbidity and mortality associated with diabetes in the US. A 2- to 3-fold incidence of CVD occurs in both type 1 and type 2 diabetic individuals over that in age- and gender-matched non-diabetic persons. Recent encouraging data demonstrating a decline in CVD mortality in the general US population do not reflect such a decline in the diabetic population, particularly in women. Increased risk for CVD is related to duration of diabetes and hyperglycemia, as well as hypertension, dyslipidemia, insulin resistance, gender, coagulation abnormalities, and other factors. Health care providers need to advocate for an uncompromising, multi-component attack on all modifiable risk factors for CVD, including glucose control, in the person with diabetes mellitus. This review focuses on known modifiable risk factors for CVD associated with diabetes, potential targets for primary and secondary prevention.

ABC1: the gene for Tangier disease and beyond

Coronary heart disease (CHD) is the leading cause of death in America. CHD is multifactorial, and low plasma high-density lipoprotein cholesterol (HDL-C) levels are among the most common biochemical abnormalities observed in CHD patients. The mechanisms controlling plasma HDL-C levels are poorly understood. However, several groups recently reported that mutations at the ATP-binding cassette transporter 1 gene (ABC1) are responsible for a rare disorder known as Tangier disease, which is characterized in the homozygous state by the virtual absence of circulating plasma HDL. This new finding represents a major breakthrough in our knowledge of lipoprotein metabolism and, more specifically, the reverse cholesterol transport. This information could lead to a more precise assessment of the genetic predisposition to CHD as well as to new therapeutic tools to prevent and treat CHD.

Re-emergence of fibrates in the management of dyslipidemia and cardiovascular risk

It is now widely accepted that low-density lipoprotein (LDL) is not the only atherogenic component of the lipid profile and that abnormalities in the metabolism and plasma levels of triglycerides and high-density lipoprotein (HDL) may lead to accelerated growth of atherosclerotic lesions. Fibrates are the drugs of first choice in the management of hypertriglyceridemia, and are also able to substantially raise HDL. The recently published Veterans Administration-High-density Lipoprotein Intervention Trial (VA-HIT) trial showed that fibrate treatment in patients with coronary heart disease (CHD), low HDL, modestly elevated triglycerides, and normal LDL reduces the risk of a recurrent coronary event by 25%. A reasonable approach to the dyslipidemic patient with high CHD risk is to tailor the intervention to the specific lipoprotein abnormality. Under these assumptions fibrate therapy should become widespread, considering that the most common lipid alteration in CHD and patients with diabetes is low HDL and high triglycerides.

Niacin dosing: relationship to benefits and adverse effects

Because of the original observation by Altschul et al., that nicotinic acid (niacin), not nicotinamide, in pharmacologic doses lowered human serum cholesterol levels, an avalanche of reports have been published over the past 45 years on the plasma lipid-regulating properties of this drug and its beneficial cardiovascular effects. A myriad of studies that have examined efficacy, safety, adverse effects, and pharmacologic properties of niacin rendered convincing evidence that niacin, used alone or combined with other agents, has favorable effects on serum lipoprotein regulation and on containment of atherothrombotic cardiovascular diseases. However, because of the unusual side effect profile of niacin and the availability of various formulations of this drug, niacin must be used prudently and with careful instruction and monitoring of patients. This review summarizes the pertinent and recent literature on niacin that impacts its therapeutic use. We also discuss some controversial issues and personal clinical experience and opinions on this topic.

Fibrates, dyslipoproteinaemia and cardiovascular disease

Recent epidemiological data have reaffirmed that elevated plasma triglyceride and low HDL-cholesterol levels are important risk factors for atherosclerotic vascular disease. The rationale for the clinical use of fibric acid derivatives, which are designed to correct this metabolic nexus, is now on firmer ground. The mechanism of action of fibrates on lipoprotein metabolism has recently been elucidated at the molecular level and involves the activation of peroxisome proliferator-activated receptor-alpha 1 in the liver, with the net effect of improving the plasma transport rates of several lipoproteins. Other potential anti-atherothrombotic effects include the inhibition of coagulation and enhancement of fibrinolysis, as well as the inhibition of inflammatory mediators involved in atherogenesis. These consequences probably underpin the favourable effects of fibrates seen in recent angiographic and clinical trials. Two important clinical trials on the effect of gemfibrozil (Veterans Administration-HDL-Cholesterol Intervention Trial) and bezafibrate (Bezafibrate Infarction Prevention Study) have recently been completed in subjects with elevated triglyceride, low HDL and normal or near-normal LDL-cholesterol levels. The results testify to the efficacy of these agents in decreasing the incidence of cardiovascular events, particularly in patients with multiple risk factors and plasma triglyceride levels of over 2.2 mmol/l. The findings of these trials are compared with the statin-based Air Force/Texas Coronary Atherosclerosis Prevention Study, with a recommendation that future studies in appropriately selected patients should examine the synergistic effect of the fibrate/statin combination. The absolute risk reduction in the incidence of coronary events in the Veterans Administration-HDL-Cholesterol Intervention Trial compares favourably with the statin trials. The therapeutic aspects of the efficacy and safety of fibrates are reviewed. Besides primary mixed hyperlipidaemias, particular indications for the clinical use of fibrates include type 2 diabetes, the metabolic syndrome and renal insufficiency. The St Mary's, Ealing, Northwick Park Diabetes Cardiovascular Disease Prevention Study has suggested that fibrates may decrease the incidence of coronary events in type 2 diabetes, but this hypothesis will be more extensively tested in the Diabetes Atherosclerosis Intervention Study, Fenofibrate in Event Lowering in Diabetes Study and Lipids in Diabetes Study projects. Although significant new knowledge has accrued over the past few years concerning the fundamental and clinical aspects of fibrates, the success of these agents in clinical practice depends on the availability of methods for assessing cardiovascular risk as well as on treatment guidelines, which as presently designed and recommended may be inaccurate and suboptimal.

Prevention of coronary heart disease. Part I. Primary prevention

The first concern in primary prevention is the physician's belief that primary prevention is important for all adults and that intervention can significantly affect risk. Given the coronary plaque burden over many years and the importance of the development of healthy lifestyles early in adulthood to decrease coronary plaque burden, there are excellent reasons to begin prevention even with young adults. At the very least, a patient seen for any reason should provide a smoking history, have knowledge of the presence of early CHD in first-degree relatives and measurements of blood pressure, height, and weight, provide evidence for a cholesterol level within 5 years (after age 20 according to NCEP guidelines or in middle age according to ACP guidelines), and be given an assessment of glucose tolerance or diabetes. Information about alcohol intake and physical activity status are also of some importance. Other than height, weight, and blood pressure, during the physical examination, the physician should initially assess the strength of pulses in the lower extremities, evidence for carotid or femoral bruits, and eyegrounds for retinal arterial changes, and the skin and subcutaneous tissue should be examined for xanthomas and the eyes should be examined for corneal arcus and xanthelesma. These elements should be part of any initial examination by a primary care physician and are not extraordinary. In addition to lipid and blood sugar analyses, other evaluations may include blood urea nitrogen and creatinine and electrolytes in patients with hypertension or diabetes or in patients who are on antihypertensive agents. It may be prudent to obtain an ECG for patients who are older than 40 years. The elements mentioned above are the elements of the history, physical examination, and laboratory examination in subjects without a past history of CHD and with no clinical evidence for CHD. Primary prevention management begins with a discussion of risk factors with the patient. The key interventions aim at the lowering of blood pressure to at least less than 140/90 mm Hg, the complete cessation of smoking, the lowering of lipid levels to less than 130 mg/dL, the lowering of triglycerides to less than 200 mg/dL (or, some would argue, < 150 mg/dL), and the attempt to keep HDL cholesterol above 35 mg/dL (more than 40 to 45 mg/dL is a better goal) with the use of lifestyle modification. For patients with diabetes, strict control of glucose levels is essential to minimize disease of the microvasculature and possibly to minimize progressive renal disease. There are several lifestyle modifications for lipids. For patients with elevated LDL cholesterol, modifications include a less than 30% fat calorie diet and less than 300 mg of cholesterol intake daily, with fat calories approximately equally distributed among saturated fats, polyunsaturated fats, and monounsaturated fats (1/3, 1/3, 1/3; rule of 3s). The assistance of a dietician is extremely helpful in this regard. For patients with a low HDL cholesterol, weight reduction (for overweight patients) by calorie control and increased physical activity and smoking cessation will have some modest effect. For patients with elevated triglycerides, a diet similar to that for lowering of LDL cholesterol with the addition of stricter calorie limitation, avoidance of refined sugars, increase in complex carbohydrates, and avoidance of alcohol will be helpful. A decrease in the percent of fat calories to 20% to 25% will be of assistance to those patients with particularly high triglycerides. The treatment of underlying conditions such as diabetes mellitus, hypothyroidism, liver disease, and some renal conditions may also significantly modify high triglycerides. For patients with hypertension, limitation of sodium to 2 gm/d (6 gm sodium chloride), limitation of alcohol to 1 to 2 drinks a day, increased physical activity, and weight reduction are the key lifestyle modifications. (ABSTRACT TRUNCATED)

Non-pharmacological lowering of low-density lipoprotein by apheresis and surgical techniques

In the past year, new data have appeared on the long-term benefits of low-density lipoprotein apheresis in severely hypercholesterolemic patients who are refractory to lipid-lowering drug therapy. Such data are critical for clinical decision-making, because they confirm the hypothesis that the dramatic reduction in low-density lipoprotein made possible by this technique produces clear-cut clinical benefits. Because of its efficacy and low incidence of side-effects, apheresis for severe drug-refractory hypercholesterolemia has superseded surgical approaches, such as liver transplantation or ileal bypass.

Pathophysiological events during pregnancy influence the development of atherosclerosis in humans

Pathophysiological events occurring during fetal development are increasingly recognized as influencing atherosclerosis throughout childhood and adolescence. Maternal hypercholesterolemia during pregnancy markedly increases fatty streak formation in human fetal arteries. Although fetal fatty streaks partially regress under normocholesterolemic conditions, progression of atherosclerosis in children of hypercholesterolemic mothers is much faster than in children of normocholesterolemic mothers. This cannot be accounted for by conventional risk factors of atherosclerosis or inherited genetic differences. The nature of the persistent changes in the fetal arterial wall responsible for increased atherogenesis in children and the mechanisms by which maternal hypercholesterolemia induces these changes need to be investigated, because they may offer important insights into the pathogenesis of atherosclerosis and because targeted interventions in mothers during pregnancy may yield considerable long-term benefits.