Seminars in vascular medicine最新文献

Lipid abnormalities play an important part in raising the cardiovascular risk in diabetic subjects. The main components of diabetic dyslipidemia are increased plasma triglycerides, low concentration of high-density lipoprotein cholesterol, preponderance of small, dense low-density lipoprotein, and excessive postprandial lipemia. Small, dense low-density lipoprotein, the elevation in remnant triglyceride-rich lipoprotein particles, and the low high-density lipoprotein are the most powerful atherogenic components. The coexistence of these three factors strongly aggravates the lipid accumulation in the arterial wall and the formation of atherosclerotic plaques. The position of diabetes in cardiovascular risk assessment has been recently reviewed in the Harmonized Clinical Guidelines on Prevention of Atherosclerotic Vascular Disease. In general, patients with diabetes carry a high risk for cardiovascular disease, but the absolute risk varies depending on the type of diabetes, age, and population baseline risk. The Adult Treatment Program III (ATP III) and the American Heart Association have designated diabetes as a high-risk condition and recommended intensive risk-factor management. Concerning therapeutic targets, both ATP III and the American Diabetes Association (ADA) guidelines have identified low-density lipoprotein cholesterol as the first priority of lipid lowering, and the optimal level was set at less than 2.6 mmol/L (100 mg/dL). There is strong evidence, coming from landmark secondary prevention studies, that LDL lowering in people with diabetes is associated with significant clinical benefits. The benefits of statin therapy in type 2 diabetics can no longer be questioned. Ongoing clinical trials will help clarify the question of whether increasing high-density lipoprotein cholesterol with fibrates in the presence of low low-density lipoprotein levels (lower than 3.4 mmol/L, or 130 mg/dL) will be more beneficial than statin therapy alone. The new paradigms in risk-reduction therapies for type 2 diabetic subjects are focused on cardiovascular disease prevention, rather than only on glucose or lipid control. Therapeutic lifestyle changes are considered primary therapies for hyperglycemia and coexisting metabolic syndrome, which can be diagnosed in more than half of type 2 diabetes subjects. New perspectives of lipid management in type 2 diabetes should take into account that insulin resistance, increased lipolysis, and overproduction of large, buoyant, very low density lipoprotein particles are at the base of diabetic dyslipidemia. Accordingly, drugs acting in the regulatory steps of very low density lipoprotein assembly should be developed. Activation of peroxisome proliferator activated receptor alpha (PPARalpha), as occurs with fibrates, lowers free fatty acids (FFAs) and triglyceride levels. PPARgamma agonism, as demonstrated by the thiazolidinediones, increases triglyceride lipolysis, FFA transport, and conversion of FFAs to trigly

The recommended therapy of hypercholesterolemia in children consists of dietary modification and bile acid-binding resins. Unfortunately, the lipid-lowering efficacy of bile acid-binding resins is modest, and moreover, long-term compliance is poor because of side effects. In contrast, hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) are widely used in adults and are considered to be the first choice in the treatment of hypercholesterolemia in that age category. In the last few years, several randomized trials have been conducted to evaluate the efficacy, safety, and tolerability of statin therapy in both children and adolescents. In this article, we review statin therapy in hypercholesterolemic children in terms of efficacy, safety, pharmacokinetics, and psychosocial functioning. Statins are not only effective in reducing low-density lipoprotein cholesterol levels in children with familial hypercholesterolemia but also improve endothelial function and reduce the progressive thickening of the intima media complex of the carotid arteries. Statins seem safe at the longer term in children in terms of plasma levels of liver enzymes and liver function, creatine kinase levels, and muscle function, as well as growth and sexual development. Long-term follow-up studies are needed to assess whether statin treatment started early in children with familial hypercholesterolemia can prevent future cardiovascular events.

Clinical studies indicate that 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) therapy has a cardiovascular protective activity that may result from an improvement in endothelial function. Experimental studies have shown that statins protect against ischaemia-reperfusion injury of the heart and stimulate the growth of new blood vessels in ischemic limbs of normocholesterolemic animals. The mechanisms underlying these serum lipid-independent effects of statins are not completely understood, but there is increasing evidence that they improve endothelial function through molecular mechanisms that mediate an increase in endothelium-derived nitric oxide. Recent research has revealed a link between statins and the serine/threonine protein kinase Akt that regulates multiple angiogenic processes in endothelial cells, including the generation of nitrous oxide. In contrast to these data, it has also been reported that higher doses of statins inhibit endothelial cell migration and angiogenesis. Thus, further studies on the actions of statins may lead to the identification of new pharmacological targets for the control of blood vessel growth.

Cerebrovascular risk represents a progressive and evolving concept owing to the particular distribution of risk factors in patients with ischemic stroke and in light of the newest stroke subtype classifications that account for pathophysiological, instrumental, and clinical criteria. Age represents the strongest nonmodifiable risk factor associated with ischemic stroke, while hypertension constitutes the most important modifiable cerebrovascular risk factor, confirmed by a host of epidemiological data and by more recent intervention trials of primary (HOT, Syst-Eur, LIFE) and secondary (PROGRESS) prevention of stroke in hypertensive patients. To be sure, a curious relationship exists between stroke and diabetes. Although the Framingham Study, The Honolulu Heart Program, and a series of Finnish studies reported a linear relationship between improved glucose metabolism and cerebral ischemia, the clinical and prognostic profile of diabetic patients with ischemic stroke remains to be fully understood. Our group, on the basis of TOAST classification--a diagnostic classification of ischemic stroke developed in 1993 that distinguishes five different clinical subtypes of ischemic stroke: large-artery atherosclerosis (LAAS), cardioembolic infarct (CEI), lacunar infarct (LAC), stroke of other determined origin (ODE), and stroke of undetermined origin (UDE), and now extensively used in clinical and scientific context--analysed the prevalence of cerebrovascular risk factors and the distribution of TOAST subtypes in more 300 patients with acute ischemic stroke in two consecutives studies that reported the significant association between diabetes and the lacunar subtype and a better clinical outcome for diabetic patients, most likely related to the higher prevalence of the lacunar subtype. Well-confirmed are the roles of cigarette smoking, atrial fibrillation, and asymptomatic carotid stenosis as cerebrovascular risk factors. Particularly interesting seems to be the function of inflammation markers (CRP, TNF-alpha, IL-1 beta, ISPs) as potential risk factors. Still elusive remains the association between cholesterol serum levels and stroke, on the basis of the epidemiological data regarding this causative relationship, confirmed only by the results of intervention trials (4S, LIPID, CARE, HPS, ASCOT). Ultimately, cerebrovascular risk appears peculiar owing to the unique relationship between some modifiable risk factors (mainly diabetes and cholesterol) and the possible preferential association with stroke subtypes and specific cerebrovascular risks.

The treatment of dyslipidemia is beyond doubt one of the cornerstones of cardiovascular prevention. If we want to touch and comment on at least the principal news in this broad field, we must simplify and pay attention to only a few selected areas. The focus of this article is on hypercholesterolemia and the treatment options for elevated low-density lipoprotein (LDL)-cholesterol; it also addresses the questions of low high-density lipoprotein (HDL)-cholesterol levels and the treatment of dyslipidemia of the metabolic syndrome. In particular, statins have had accumulation of new evidence resulting in novel indications and new target groups. Modern, even more potent drugs lowering total and LDL-cholesterol levels are available (new statins, e.g., rosuvastatin, pitavastatin, cholesterol absorption inhibitor ezetimibe) More and more attention of the medical public is being paid to dyslipidemia of the metabolic syndrome (so-called lipid triad), which seems to be the greatest rival of LDL-cholesterol among lipid risk factors for cardiovascular disease. In the treatment of this dyslipidemia especially the nuclear peroxisome proliferator-activated receptor (PPAR) agonists play an important role. In particular fibrates but also glithasones are noteworthy in this respect. There are fewer data for fibrates than for statins, but nevertheless evidence documenting benefit of this therapy is growing. A statin and fibrate combination is a promising future approach not only to the treatment of metabolic syndrome. Moreover, niacin, particularly in combination with a statin, might experience a renaissance. HDL-cholesterol level modification attracts more and more discussions; on the horizon there are new therapies of low HDL, for example, cholesterol-ester transfer protein inhibitors, which have been shown to have a potency for increasing HDL by more than 50%.

Apolipoprotein E (apoE) is a major constituent of lipoproteins in the plasma and in the brain. There are three common apoE isoforms, termed E2, E3, and E4. By virtue of its ability to bind to lipoprotein receptors, apoE plays a key role in the metabolism of triglyceride-rich lipoproteins in the plasma. Homozygous carriers of apoE2 have an increased risk to develop type III hyperlipoproteinemia, whereas apoE4 is associated with elevated levels of low-density lipoprotein cholesterol. In the brain, apoE is associated with cholesterol-rich lipoproteins and is involved in the transport of cholesterol to neurons. The genetic polymorphism of apoE is among the strongest determinants of the risk and mean age of onset of Alzheimer's disease. The mechanism by which apoE isoforms differentially contribute to disease expression is not known.