Seminars in vascular medicine最新文献

Current scientific evidence indicates that dietary fat plays a role in weight loss and maintenance. Meta-analyses of intervention trials find that fat-reduced diets cause a 3-4-kg larger weight loss than normal-fat diets. A 10% reduction in dietary fat can cause a 4-5-kg weight loss in individuals with initial body mass index of 30 kg m (-2). Short-term trials show that nonfat dietary components are equally important. Sugar-sweetened beverages promote weight gain, and replacement of energy from fat by sugar-sweetened beverages is counterproductive in diets aimed at weight loss. Protein has been shown to be more satiating than carbohydrate, and fat-reduced diets with a high protein content (20-25% of energy) may increase weight loss significantly. There is little evidence that low-glycemic index foods facilitate weight control. Evidence linking certain fatty acids to body fatness is weak. Monounsaturated fatty acids may even be more fattening than polyunsaturated and saturated fats. No ad libitum dietary intervention study has shown that a normal-fat, high-monounsaturated fatty acid diet is comparable to a low-fat diet in preventing weight gain. Current evidence indicates that the best diet for prevention of weight gain, obesity, type 2 diabetes, and cardiovascular disease is low in fat and sugar-rich beverages and high in carbohydrates, fiber, grains, and protein.

Clinical studies have shown that hydroxy-methyl glutaryl coenzyme A reductase inhibitors (statins) may favorably affect atherothrombosis. In addition to their potent cholesterol-lowering properties, statins reduce atheroma progression as well as the incidence of acute thrombosis-related vascular events and their dreadful clinical consequences. Available data indicate that statins exert significant antithrombotic effects in clinical practice by reducing the occurrence of vascular atherothrombotic events, with a more prominent effect in high-risk patients. The mechanisms by which statins inhibit thrombosis have been extensively investigated, and several pathways appear to be involved. In particular, statins have been proposed to reduce platelet activation and to exert favorable effects on fibrinolysis, but no clear-cut conclusion can be drawn from available studies. Moreover, statins do not consistently influence fibrinogen or factor VII levels in plasma. In contrast, in vitro and in vivo data indicate that these compounds profoundly affect thrombin generation driven by tissue factor/factor VII pathway. In vitro studies indicate that this effect is not dependent on plasma cholesterol lowering but, rather, on the inhibition of isoprenoid biosynthesis. The relative contribution of reduced levels of prenylated proteins and of cholesterol pathway to the modulation of tissue factor expression is, however, hardly to be established in clinical settings.

The endothelium integrates and modulates critical functions of the arterial wall. As well as regulating vasomotion, it controls inflammation, coagulation, and thrombosis. Many of these actions are mediated through the release of nitric oxide. Endothelial dysfunction is associated with atherosclerosis and its risk factors. It is independently correlated to adverse cardiovascular events, including myocardial infarction, coronary death, and the need for revascularization. 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) protect against cardiovascular death, myocardial ischemia, myocardial infarction, and stroke. Although cholesterol reduction accounts for some of these benefits, others appear to be independent of cholesterol lowering. The endothelium mediates many of these "lipid-dependent" and "lipid-independent" actions of statins. This chapter reviews the effects of statins on endothelial dysfunction. To do so, a brief outline of the biology of the endothelium is a prerequisite. This will be followed by a summary of the advances in vascular research on cholesterol-dependent and cholesterol-independent effects of statins, with a focus on the endothelium. Ultimately, clinical relevance of observations derived from basic biology will be discussed.

Dyslipidemia plays critical roles in the pathogenesis of coronary atherosclerosis, a chronic inflammatory disease. Vascular inflammation also triggers the onset of acute complications of atherosclerosis, such as myocardial infarction. Advances in cardiovascular medicine demonstrate that lipid-lowering therapy by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) likely prevents acute coronary complications by limiting vascular inflammation. In particular, recent clinical evidence indicates aggressive lipid-lowering treatment for patients at risk. Preclinical studies also support the concept of anti-inflammatory properties of lipid lowering by either diet or statins. Therefore, dyslipidemia is the primary target of therapy for the prevention of coronary atherosclerosis and its acute thrombotic complications. Nevertheless, even aggressive statin therapy does not forestall many adverse events. Thus, current cardiovascular medicine also seeks mechanisms to mitigate vascular inflammation and atherosclerosis other than addressing low-density lipoprotein, and new therapeutic strategies beyond lipid lowering.

Coronary artery disease in the transplanted heart, also known as cardiac allograft vasculopathy, is one of the major causes of mortality late after heart transplantation. There are multiple immune and nonimmune risk factors associated with this disease process, one of which is hyperlipidemia. Use of lipid-lowering agents, specifically 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) was initially reported to have outcomes benefit and possibly immunosuppressive effects in a single-center study of heart transplant recipients. Other subsequent studies have supported this beneficial effect. Hyperlipidemia is associated with immune activity, particularly with respect to oxidation-sensitive signaling pathways. By lowering lipids, statins can ameliorate this immune activity, but it has been a matter of contention as to whether statins have cholesterol-independent immune-modulating effects. In two recent papers, cholesterol-independent immune effects of statins have been reported, including repressed induction of major histocompatibility complex class II by interferon-gamma, and selective blocking of leukocyte function antigen 1, both of which reduce the activation of T lymphocytes. The clinical reports demonstrating outcomes benefits in heart transplant recipients and recent laboratory publications that report an immunomodulatory effect of statins provide a firm scientific rationale to support the routine use of statins in heart transplant patients.

Cardiac hypertrophy and heart failure are leading causes of morbidity and mortality worldwide. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, have been shown to inhibit cardiac hypertrophy and improve symptoms of heart failure by cholesterol-independent mechanisms. Statins block the isoprenylation and function of members of the Rho GTPase family, such as Rac1 and RhoA. Because Rac1 is a requisite component of NADPH oxidase, which is a major source of reactive oxygen species in cardiovascular cells, the ability of statins to inhibit Rac1-mediated oxidative stress contributes importantly to their inhibitory effects on cardiac hypertrophy. Furthermore, inhibition of RhoA by statins leads to the activation of protein kinase B/Akt and upregulation of Type 3 nitric oxide synthase in the endothelium and the heart. This activation and upregulation results in increased angiogenesis and myocardial perfusion, decreased myocardial apoptosis, and improvement in endothelial and cardiac function. Because these effects of statins occur independent of cholesterol lowering, statins may have therapeutic benefits in nonhyperlipidemic patients with cardiac hypertrophy and heart failure.

Clinical trials have firmly established that 3-hydroxy-3-methylglutaryl-coenzyme-A reductase inhibitors (statins) can induce regression of vascular atherosclerosis as well as reduction of cardiovascular-related morbidity and death in patients with and without coronary artery disease. These beneficial effects of statins are usually assumed to result from their ability to reduce cholesterol synthesis. However, because mevalonic acid is the precursor not only of cholesterol but also of many nonsteroidal isoprenoid compounds, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme-A reductase may result in pleiotropic effects. Indeed, statins can interfere with major events involved in the formation and the evolution of atherosclerotic lesions, such as arterial myocyte migration and proliferation and cholesterol accumulation, independent of their hypolipidemic properties. The aim of this article is to focus on clinical and experimental data that show that statins possess effects beyond cholesterol lowering, particularly on arterial smooth muscle cell proliferation. The contribution of these direct vascular effects to the reduction of cardiovascular events observed in clinical trials with statins represents one of the major challenges for future studies to understand the antiatherosclerotic benefits of these agents.

Statins appear to be potent drugs with a variety of pleiotropic effects with vasculoprotective and cardioprotective activity. The beneficial effects of statins on endothelial cells as well as on endothelial cell function appear to be related to improved nitric oxide bioavailability. Mechanistically, statins induce endothelial nitric oxide synthase mRNA stability in endothelial cells and promote endothelial nitric oxide synthase activity through a PI3K/Akt dependent pathway, which is a common signal transduction pathway shared by growth factors such as vascular endothelial growth factors or fibroblast growth factors (FGFs), estrogens, or statins. Furthermore, statins have potent antiinflammatory capacities by potently interfering with the generation of reactive oxygen species or activating scavenging systems for free radicals such as the thioredoxin system. These mechanisms might all contribute to improved NO bioavailability and confer the beneficial actions of statins. The proangiogenic properties of statins and their effects on reendothelialization following vessel injury include novel actions such as the mobilization, differentiation, and improved survival of endothelial progenitor cells. Statin therapy might reverse the impaired functional regeneration capacities seen in patients with risk factors for coronary artery disease or documented active coronary artery disease by specifically interacting with progenitor cell function. Accordingly, augmentation of functionally active endothelial progenitor cells with improved homing capacity will be a critical step in advancing therapeutic neovascularization as well as reendothelialization in patients with coronary artery disease.

Hypertension and dyslipidemia are frequently associated as risk factors for cardiovascular diseases. Statins are among the most potent drugs to correct hypercholesterolemia, and their use across a wide range of cardiovascular risk levels significantly reduced morbidity and mortality in large intervention trials. Aside from (or in addition to) reducing plasma cholesterol, statins also reduce blood pressure, another effect associated with cardiovascular risk reduction by other antihypertensive drugs. This review examines the proposition that a part of the statins' beneficial effect in cardiovascular diseases may result from direct effects on blood pressure regulation, perhaps independent of lipid lowering. Potential molecular mechanisms are considered (e.g., "pleiotropic" effects on endothelial vasoactive mediators, oxidant stress, or inflammation), all of which may affect the central or peripheral control of blood pressure homeostasis, as well as modulate target organ damage. In particular, potential effects of statins on blood pressure and heart rate variability open new perspectives for a better tailoring of drug treatment in high-cardiovascular risk patients.

Increasing clinical and experimental evidence indicates that some beneficial effects of statins, known as efficient therapeutic agents in cardiovascular disease treatment, may result from their ability to modulate vascular and endothelial cell gene expression by mechanisms independent of cholesterol reduction. It has been shown that statins exhibit direct anti-inflammatory properties via inhibition of proinflammatory cytokine and chemokine secretion, as well as through adhesion molecule expression on leukocytes. Another important mechanism by which statins may modulate the immune response is inhibition of interferon gamma-induced expression of class II major histocompatibility complexes. Class II major histocompatibility complex expression is central to immune regulation in T cell-mediated autoimmune diseases, indicating a potential beneficial role of statins in these pathologies. Indeed, promising new preclinical data indicate that statins might be useful in the treatment of multiple sclerosis and rheumatoid arthritis.