Lipids and stroke: the opportunity of lipid-lowering treatment

Lack of the Toll-Like Receptor 4 Gene Polymorphisms Asp299Gly and Thr399ile in a Chinese Population

The toll-like receptor 4 (TLR4), predominantly known for its role as an important mediator of immune reactions, is expressed in atherosclerotic lesions. Atherosclerosis resulting in cerebral or carotid arterial stenosis/occlusion plays the most important role in the occurrence of cerebral infarction (CI), and thus TLR4 polymorphisms may influence formation of atherosclerosis and the development of CI. This study was aimed to detect two commonly reported Asp299Gly and Thr399Ile polymorphisms in TLR4 gene in Hunan Han Chinese and their possible relationship with CI. By using the method of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), the polymorphisms TLR4, Asp299Gly and Thr399Ile, were determined in 366 CI patients and 200 controls from Changsha area of Hunan Province. Carotid intima-media thickness (CIMT) also was detected by Bmode ultrasonography. Our results suggested both the TLR4, Asp299Gly and Thr399Ile, genetic polymorphisms were not observed in all subjects from Hunan Changsha. Therefore, we speculate they might not be an important factor in the development of CI in the Chinese.

Simvastatin improves clinical scores in a rabbit multiple infarct ischemic stroke model: synergism with a ROCK inhibitor but not the thrombolytic tissue plasminogen activator

Statins have pleiotropic neuroprotective effects in the central nervous system. In this study, we assessed the pharmacological effects of simvastatin on measures of behavior in New Zealand white rabbits embolized using a suspension of small-sized blood clots. For these studies, simvastatin was administered up to 3 hours following embolization, and behavior was measured 48 hours following embolization to calculate the dose of emboli (P(50) in mg) that produces neurological deficits in 50% of the rabbits. A treatment is considered neuroprotective if it significantly increases the P(50) compared to control. Simvastatin treatment (20mg/kg, bolus subcutaneous injection) significantly improved clinical function and increased the P(50) by 143% when administered 1 hour following embolization but was ineffective at 3 hours. In combination studies with the thrombolytic, tissue plasminogen activator (tPA) using a standard intravenous dose of 3.3mg/kg (20% bolus, 80% infused), we found that simvastatin could be safely administered with tPA to improve clinical scores; however, the maximum behavioral improvement with the combination treatment was similar to either monotherapy alone, both of which significantly improved behavior (p<0.05). It has been proposed that Simvastatin neuroprotection may be related to a variety of signaling pathways including Rho-kinase (ROCK). To determine if a ROCK mechanism is involved in simvastatin-induced neuroprotection following embolic strokes, we used pharmacological intervention with the ROCK inhibitor, fasudil. When fasudil was administered 30 minutes before simvastatin (given at 1 hour), there was an additional significant (p=0.0217) synergistic increase in behavioral function. However, fasudil as a monotherapy did not affect behavioral function in embolized rabbits. The study suggests that there may be an interaction between simvastatin treatment and the ROCK signaling pathway that should be further explored. Our results suggest that simvastatin treatment may have clinical benefit when used alone or in the presence of tPA, but the therapeutic window using a single-dose regimen is narrow.

Reducing the risk of stroke in type 2 diabetes: pathophysiological and therapeutic perspectives

Reducing the excess cerebrovascular burden in patients with type 2 diabetes remains a major therapeutic challenge, especially with respect to the high risk of recurrent events. Targeting the traditional metabolic risk factors of hypertension, dyslipidemia, and hyperglycemia has failed to remove this excess risk, and agents targeting thrombotic risk (i.e., antiplatelet and anticoagulant drugs) remain poorly studied in the context of stroke in diabetes. This may relate to the accumulation of risk factors in type 2 diabetes as well as to diabetes-specific pathophysiologic factors. Regrettably, there is a lack of prospective evidence to support the efficacy of interventions in the secondary prevention of cerebrovascular events in type 2 diabetes, particularly recurrent stroke events. Overall, there is a need for rigorous evaluations of new therapeutic approaches in both primary and secondary prevention of stroke and management of acute stroke in patients with type 2 diabetes. This systematic review of the published literature summarizes the evidence regarding current therapeutic interventions and their impact on the risk of stroke in people with type 2 diabetes, and highlights potential strategies for improving outcomes.

Statins in stroke prevention: what an internist should know

Historically, the etiological link between hypercholesterolemia and stroke has been less clear than for coronary heart disease. The lack of association between cholesterol levels and stroke in most epidemiological and observational studies has brought about this controversy. Many recent, long-term clinical studies have confirmed that statin therapy results in a reduced risk of strokes, even in so-called "normocholesterolemic" patients. The magnitude of the effect is great. A large-scale analysis of more than 90,000 individuals showed that every 10% reduction in the concentration of LDL-cholesterol reduces the risk of stroke by 15.6%. The positive effect of statins on stroke depends mainly on LDL cholesterol reduction, but other non-lipid mechanisms, so-called "pleiotropic" effects, have been shown to play a role. This review seeks to summarize the role of statins in stroke prevention. Despite the fact that our understanding of the benefits of statins in stroke prevention is still evolving, we find marked room for improvement in stroke risk factor management. Internists must face this challenge and integrate this new knowledge into their daily clinical practice.

Quantitative trait locus analysis of carotid atherosclerosis in an intercross between C57BL/6 and C3H apolipoprotein E-deficient mice

BACKGROUND AND PURPOSE

Inbred mouse strains C57BL/6J (B6) and C3H/HeJ (C3H) exhibit marked differences in atherosclerotic lesion formation in the carotid arteries on the apolipoprotein E-deficient (apoE(-/-)) background when fed a Western diet. Quantitative trait locus analysis was performed on an intercross between B6.apoE(-/-) and C3H.apoE(-/-) mice to determine genetic factors contributing to variation in the phenotype.

METHODS

Female B6.apoE(-/-) mice were crossed with male C3H.apoE(-/-) mice to generate F(1) hybrids, which were intercrossed to generate 241 female F(2) progeny. At 6 weeks of age, F(2) mice were started on a Western diet. After being fed the diet for 12 weeks, F(2) mice were analyzed for phenotypes such as lesion size in the left carotid arteries and plasma lipid levels and typed for 154 genetic markers spanning the mouse genome.

RESULTS

One significant quantitative trait locus, named CAth1 (25 cM, log of the odds score: 4.5), on chromosome 12 and 4 suggestive quantitative trait loci, on chromosomes 1, 5, 6, and 11, respectively, were identified to influence carotid lesion size. One significant quantitative trait locus on distal chromosome 1 accounted for major variations in plasma low-density lipoprotein/very-low-density lipoprotein, high-density lipoprotein cholesterol, and triglyceride levels. Carotid lesion size was not significantly correlated with plasma low-density lipoprotein/very-low-density lipoprotein or high-density lipoprotein cholesterol levels.

CONCLUSIONS

These data indicate that the loci for carotid lesions do not overlap with those for aortic lesions as identified in a previous cross derived from the same parental strains, and carotid atherosclerosis and plasma lipids are controlled by separate genetic factors in the B6 and C3H mouse model.

Action on vascular risk factors: importance of blood pressure and lipid lowering in stroke secondary prevention

INTRODUCTION

Secondary stroke prevention comprises a broad spectrum of therapeutic actions that includes the appropriate management of risk factors and the action on blood pressure and serum lipids that are of great importance to decrease stroke recurrences.

METHODS

We conducted a review of the published studies analyzing the relevance of the treatment of blood pressure and serum lipids, with special attention to recent findings of clinical trials and current guidelines on stroke secondary prevention.

RESULTS

The relationship between blood pressure and stroke has been widely demonstrated; however, the role of serum lipids has been discussed for a long time. Recent results from epidemiological studies and clinical trials have demonstrated its role as modifiable risk factor for stroke. Blood pressure and lipid lowering are associated with significant reductions in recurrent strokes as well as in other vascular events in transient ischemic attack (TIA) or stroke patients. The PROGRESS and MOSES trials suggest that diuretics, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers could confer additional benefits in stroke patients, and the SPARCL study did so for statins. These drugs are not only efficacious in the reduction of stroke recurrences, but also in other cardiovascular events.

CONCLUSIONS

Blood pressure and serum lipids are two important and modifiable vascular risk factors that should be taken into consideration when planning secondary stroke prevention measures. This approach should include hypotensive drugs (mainly the combination of diuretics and ACE inhibitors) with the objective to maintain normal blood pressure, avoiding levels >130/80 mm Hg in all stroke patients, and statins (atorvastatin 80 mg) in patients with noncardioembolic TIA or stroke.

Advances in hemorrhagic stroke therapy: conventional and novel approaches

Treatments for spontaneous intracerebral, thrombolytic-induced and intraventricular hemorrhages (IVH) are still at the preclinical or early clinical investigational stages. There has been some renewed interest in the use of surgical evacuation surgery or thrombolytics to remove hematomas, but these techniques can be used only for specific types of brain bleeding. The STICH (Surgical Trial in Intracerebral Haemorrhage) clinical trials should provide some insight into the potential for such techniques to counteract hematoma-induced damage and subsequently, morbidity and mortality. More recently, clinical trials (ATACH [Antihypertensive Treatment in Acute Cerebral Hemorrhage] and INTERACT [Intensive Blood Pressure Reduction in Acute Cerebral Hemorrhage Trial]) have begun testing whether or not regulating blood pressure affects the well-being of hemorrhage patients, but the findings thus far have not conclusively demonstrated a positive result. More promising trials, such as the early stage CHANT (Cerebral Hemorrhagic And NXY-059 Treatment) and the late stage FAST (Factor VIIa for Acute Hemorrhagic Stroke Treatment), have addressed whether or not manipulating oxidative stress and components of the blood coagulation cascade can achieve an improved prognosis following spontaneous hemorrhages. However, CHANT was halted prematurely because although it showed that the spin trap agent NXY-059 was safe, it also demonstrated that the drug was ineffective in treating acute ischemic stroke. In addition, the recombinant activated factor VII FAST trial recently concluded with only modestly positive results. Despite a beneficial effect on the primary end point of reducing hemorrhage volume, controlling the coagulation cascade with recombinant factor VIIa did not decrease the mortality rate. Consequently, Novo Nordisk has abandoned further development of the drug for the treatment of intracerebral hemorrhaging. Even though progress in hemorrhage therapy that successfully reduces the escalating morbidity and mortality rate associated with brain bleeding is slow, perseverance and applied translational drug development will eventually be productive. The urgent need for such therapy becomes more evident in light of concerns related to uncontrolled high blood pressure in the general population, increased use of blood thinners by the elderly (e.g., warfarin) and thrombolytics by acute ischemic stroke patients, respectively. The future of drug development for hemorrhage may require a multifaceted approach, such as combining drugs with diverse mechanisms of action. Because of the substantial benefit of factor VIIa in reducing hemorrhage volume, it should be considered as a prime drug candidate included in combination therapy as an off-label use if the FAST trial proves that the risk of thromboembolic events is not increased with drug administration. Other promising drugs that may be considered in combination include uncompetitive NMDA receptor antagonists (such as memantine), antioxidants, metalloprotease inhibitors, statins and erythropoietin analogs, all of which have been shown to reduce hemorrhage and behavioral deficits in one or more animal models.