Is cholesterol a risk factor for stroke?: Yes

The effects of melatonin against atherosclerosis-induced endothelial dysfunction and inflammation in hypercholesterolemic rats

The aim of this study was to investigate the effects of melatonin on the serum asymmetric dimethylarginine (ADMA) levels and the expressions of vaspin, visfatin, dimethylarginine dimethylaminohydrolase (DDAH), and signal transducer and activator of transcription-3 (STAT-3) for evaluation of endothelial function and inflammation in the hypercholesterolemic rats. Rats were divided into 5 groups: (1) control, (2) hypercholesterolaemia, (3) melatonin administrated concurrently with cholesterol diet, (4) melatonin administrated only last 2 weeks and fed with cholesterol diet, (5) atorvastatin administered only last 2 weeks fed with cholesterol diet. Although an increase was observed in the expressions of visfatin and STAT-3 and the serum ADMA levels, the vaspin and DDAH protein expressions were found to decrease with hypercholesterolemic diets. Melatonin was determined to restore all the parameters to the normal levels. In conclusion, melatonin may have protective and therapeutic effects on hypercholesterolaemia by regulating vaspin, STAT-3, DDAH, and ADMA signalling pathways and create similar effects with atorvastatin.

PPAR-γ activator induces neuroprotection in hypercholesterolemic rats subjected to global cerebral ischemia/reperfusion injury: in vivo and in vitro inhibition of oxidative stress

Hypercholesterolemia (HC) and aging combine to increase the incidence of cerebrovascular disease through oxidative stress. Our investigation examined the effects of diet-induced hypercholesterolemia (2% for 8weeks) on the extent of brain injury in response to global cerebral ischemia/reperfusion (GCI/R) and the neuroprotective potentials of rosiglitazone in relation to oxidative stress. HC exacerbated the decline in the brain levels of GSH and the increase in MPO, proinflammatory markers and hippocampal lesions in response to GCI/R. HC rats receiving rosiglitazone, PPAR-γ agonist, demonstrated preservation of cell viability of CA1 hippocampal region and attenuation of brain edema. They also showed elevated levels of GSH and low levels of the other parameters similar to non-HC rats subjected to GCI/R. In vitro, rosiglitazone dose-dependently inhibited ROS generation by neutrophils. The results suggest exacerbation of brain lesions by HC in response to GCI/R. The neuroprotective therapeutic potentials of rosiglitazone are comparable to non-HC animals. Mechanisms of protection are possibly due to anti-oxidant, anti-inflammatory effects and scavenging properties of rosiglitazone. These results add to the beneficial therapeutic effects of rosiglitazone and its significance for age-associated diseases including hypercholesterolemia.

Effect of lipid profile upon prognosis in ischemic and haemorrhagic cerebrovascular stroke

Stroke is the third major cause of death worldwide. Elevated plasma concentration of low density lipoproteins and low plasma concentration of high density lipoprotein concentration are associated with an increased risk of atherosclerosis and coronary heart disease but the relation between serum lipids, and cerebrovascular disease is less clear. The aim of this study was to investigate the reliability and accuracy of serum lipid profile in assessing the prognosis/neurological worsening in patients with ischemic and hemorrhagic cerebrovascular stroke. The subjects in the present study comprised of 101 healthy controls and 150 cerebrovascular stroke patients (including 90 with ischemic stroke and 60 with intracerebral hemorrhagic stroke). In both the groups fasting lipid profile was determined within 72 h of the stroke. A statistically significant association was observed (p < 0.001) between the parameters of lipid profile of cases and healthy controls, and also with the prognosis of the stroke.

Hyperlipidemia disrupts cerebrovascular reflexes and worsens ischemic perfusion defect

Hyperlipidemia is a highly prevalent risk factor for coronary and cervical atherosclerosis and stroke. However, even in the absence of overt atherosclerosis, hyperlipidemia disrupts endothelial and smooth muscle function. We investigated the impact of hyperlipidemia on resting-brain perfusion, fundamental cerebrovascular reflexes, and dynamic perfusion defect during acute focal ischemia in hyperlipidemic apolipoprotein E knockout mice before the development of flow-limiting atherosclerotic stenoses. Despite elevated blood pressures, absolute resting cerebral blood flow was reduced by 20% in apolipoprotein E knockout compared with wild type when measured by [(14)C]-iodoamphetamine technique. Noninvasive, high spatiotemporal resolution laser speckle flow imaging revealed that the lower autoregulatory limit was elevated in apolipoprotein E knockout mice (60 vs. 40 mm Hg), and cortical hyperemic responses to hypercapnia and functional activation were attenuated by 30% and 64%, respectively. Distal middle cerebral artery occlusion caused significantly larger perfusion defects and infarct volumes in apolipoprotein E knockout compared with wild type. Cerebrovascular dysfunction showed a direct relationship to the duration of high-fat diet. These data suggest that hyperlipidemia disrupts cerebral blood flow regulation and diminishes collateral perfusion in acute stroke in the absence of hemodynamically significant atherosclerosis.

Correlative study between neuron-specific enolase and blood sugar level in ischemic stroke patients

Background:

A study to investigate the level of the neurobiochemical marker, Neuron-Specific Enolase (NSE), at the time of admission and its correlation with the blood sugar level in ischemic stroke patients.

Patients and Methods:

We investigated 90 patients with complete stroke who were admitted to the Stroke Unit of the Department of Neurology at Sri Aurobindo Institute of Medical Sciences. NSE was measured with commercially available quantitative ‘sandwich’ enzyme-linked immunosorbent assay kits obtained from R and D Systems. Hyperglycemia was defined as blood glucose concentration ≥ 7 mmol / L, and measured using the glucose oxidase method immediately.

Results:

Significantly increased NSE and lipid profile levels were found in ischemic stroke patients as compared to the control. Hyperglycemic ischemic stroke patients had increased levels of NSE, lipid profile, and National Institute of Health stroke scale scores (NIHSS score) compared to normoglycemic ischemic stroke patients. In addition the serum NSE level of hyperglycemic stroke patients was also positively correlated with the blood sugar level (r = 0.734 P < 0.001).

Conclusions:

Hyperglycemia predicts an increased risk of poor outcome after ischemic stroke and it is reflected by a significantly increased level of Neuron-Specific Enolase.

Doppler study of cerebral arteries in hypercholesterolemia

Background:

Hypercholesterolemia is one of the major modifiable risk factors for atherosclerosis of the coronary and carotid arteries. Although transcranial Doppler (TCD) studies of the cerebral arteries are indicative of decreased cerebral blood flow velocities in patients with hypercholesterolemia, the number of these studies has been limited. The aim of this study was to assess the hemodynamic status of the cerebral arteries in patients with hypercholesterolemia using TCD.

Methods:

In a case-control study, 60 individuals, including 30 hypercholesterolemic cases (low-density lipoprotein [LDL] > 160 mg/dL) and 30 healthy controls were enrolled. Other arterial risk factors, including diabetes mellitus, hypertension, smoking, and obesity (body mass index > 30), were evaluated and matched as well. TCD was used to assess the hemodynamics of the intracranial arteries as well as the internal carotid arteries. The mean blood flow velocity, pulsatility index, and resistance index were recorded in all the arteries.

Results:

The mean blood flow velocity, pulsatility index, and resistance index of the intracranial arteries and internal carotid arteries were not significantly different between the two groups (P > 0.05). However, those with higher levels of LDL (>180 mg/dL) showed significantly lower mean blood flow velocity and resistance index of the internal carotid arteries than the healthy controls. In addition, individuals with high-density lipoprotein (HDL) <35 mg/dL had significantly lower mean blood flow velocity in the internal carotid arteries.

Conclusion:

Hypercholesterolemia (LDL >160 mg/dL) does not seem to have a detrimental effect on the hemodynamic status of the intracranial arteries and internal carotid arteries. However, in cases of higher LDL (>180 mg/dL) and lower HDL, decreased TCD parameters in the internal carotid arteries, as a surrogate of the peripheral arteries, are prominent.

Augmented superoxide production by Nox2-containing NADPH oxidase causes cerebral artery dysfunction during hypercholesterolemia

BACKGROUND AND PURPOSE

We tested the hypothesis that elevated superoxide production by Nox2-NADPH oxidase occurs in cerebral arteries during hypercholesterolemia and causes decreased nitric oxide function.

METHODS

Wild-type (WT), apolipoprotein E-deficient (ApoE(-/-)) and Nox2(-/-)/ApoE(-/-) mice were fed a high-fat diet for 7 to 14 weeks. Basal superoxide production by cerebral arteries was measured using L-012 (100 micromol/L)-enhanced chemiluminescence. Nitric oxide function was assessed in isolated middle cerebral arteries through the constrictor response to N(omega)-nitro-L-arginine methyl ester (L-NAME; 100 micromol/L). Western blotting was used to measure protein expression of Nox2, p47phox, endothelial nitric oxide synthase, and superoxide dismutases (1-3).

RESULTS

Morphology of cerebral arteries was similar in WT and ApoE(-/-) mice. In ApoE(-/-), but not Nox2(-/-)/ApoE(-/-) mice, superoxide production by cerebral arteries was approximately 50% greater than in WT mice (P<0.05). Moreover, the magnitude of L-NAME-induced contractions of isolated middle cerebral arteries from ApoE(-/-) mice was <50% of that in WT mice (P<0.05), whereas in Nox2(-/-)/ApoE(-/-) mice, the contractile response was comparable to WT responses. In the presence of the superoxide scavenger, tempol (1 mmol/L), L-NAME-induced contractions of middle cerebral arteries were similar between WT and ApoE(-/-) mice. Expression of p47phox was approximately 2-fold higher in ApoE(-/-) versus WT mice, whereas Nox2, endothelial nitric oxide synthase, and superoxide dismutase isoforms were unchanged.

CONCLUSIONS

Elevated superoxide production and reduced basal nitric oxide-mediated relaxation occur in cerebral arteries of hypercholesterolemic mice even in the absence of lesions. These changes appear to be exclusively due to increased activity of Nox2-NADPH oxidase, possibly through increased expression of its regulatory subunit p47phox.

Capillary injury in the ischemic brain of hyperlipidemic, apolipoprotein B-100 transgenic mice

AIMS

Apolipoprotein B-100 (apoB-100) has been implicated in hyperlipidemia, which contributes to the pathogenesis of vascular disorders. Our aim was to investigate whether the expression of human apoB-100 in transgenic mice and/or a high-cholesterol diet cause cerebral microvascular lesions, and whether these conditions augment ischemia-related capillary damage.

MAIN METHODS

Human apoB-100 overexpressing transgenic (Tg(apoB-100), n=23) and wild-type mice (C5/B6, Wt, n=26) were supplied with standard or 2% cholesterol-enriched diet for 17-19 weeks. Cerebral ischemia was induced by unilateral common carotid artery occlusion. Cortical samples were embedded for electron microscopy. Microvascular density (number of microvascular profiles/examined area), lumen diameter, the swelling of astrocytic endfeet, the occurrence of endothelial microvilli (affected capillaries expressed as ratio of all capillaries encountered), and the ratio of intact capillaries (devoid of all the above pathology) were calculated.

KEY FINDINGS

The expression of apoB-100 coincided with decreased cortical microvascular density (195+/-7 vs. 223+/-8 vessels/mm(2), vs. Wt; P<0.008) and increased capillary lumen diameter (3.16+/-0.5 vs. 2.88+/-0.6 microm, vs. Wt; P<0.001). Cerebral ischemia promoted the swelling of perivascular astrocytes (62.1+/-4.2 vs. 36.5+/-4.0%, vs. contralateral, Wt; P<0.001), and reduced the ratio of intact capillaries (32.1+/-5.6 vs. 65.2+/-3.7%, vs. contralateral, Wt; P<0.001). Hyperlipidemia did not exacerbate the injury.

SIGNIFICANCE

The overexpression of human apoB-100 alters the density of the microvascular network and the diameter of capillaries, which may compromise cerebrovascular reactivity during ischemia.

Fibrinogen independently predicts the development of ischemic stroke in a Taiwanese population: CVDFACTS study

BACKGROUND AND PURPOSE

Of few prospective studies that have focused on the relationship between fibrinogen and ischemic stroke (IS) in Asian populations, the findings were inconsistent with those conducted in Western countries. Therefore, we aimed to investigate the temporal relationship between fibrinogen levels (plus several related parameters) and IS in a community-based study in Taiwan.

METHODS

Baseline data from 3281 adults (>or=20 years of age) in the Cardiovascular Diseases Risk Factor Two-Township Study were linked to incidental IS status derived from insurance claims and death certificate records. Hazard ratios and 95% CIs of clotting factors (fibrinogen, factor VII, factor VIII, and antithrombin-III) for IS events were estimated using Cox proportional hazard models.

RESULTS

With 10.4 years (average) follow-up, 128 persons developed IS (3.75 per 1000 person-years). As expected, elevated blood pressure and diabetes were independent predictors of IS events. A dose-response relationship was found in univariate analysis between IS risk and tertiles of fibrinogen (hazard ratio, 3.73; 2.19 to 1.00), factor VII (hazard ratio, 1.86; 1.35 to 1.00), and factor VIII (2.97; 1.70 to 1.00), respectively, but not for antithrombin-III. After adjusting for confounding and known risk factors, fibrinogen independently predicted IS events. A 72% increase (hazard ratio, 1.72; 1.02 to 2.90) in IS risk was observed for individuals with fibrinogen >or=8.79 mumol/L compared with those <7.03 micromol/L.

CONCLUSIONS

In addition to hypertension and diabetes, fibrinogen independently predicted future IS risk. We suggest that fibrinogen may be considered in the risk assessment model for IS in the Taiwanese population.

Caffeine blocks disruption of blood brain barrier in a rabbit model of Alzheimer's disease

High levels of serum cholesterol and disruptions of the blood brain barrier (BBB) have all been implicated as underlying mechanisms in the pathogenesis of Alzheimer's disease. Results from studies conducted in animals and humans suggest that caffeine might be protective against Alzheimer's disease but by poorly understood mechanisms. Using rabbits fed a cholesterol-enriched diet, we tested our hypothesis that chronic ingestion of caffeine protects against high cholesterol diet-induced disruptions of the BBB. New Zealand rabbits were fed a 2% cholesterol-enriched diet, and 3 mg caffeine was administered daily in drinking water for 12 weeks. Total cholesterol and caffeine concentrations from blood were measured. Olfactory bulbs (and for some studies hippocampus and cerebral cortex as well) were evaluated for BBB leakage, BBB tight junction protein expression levels, activation of astrocytes, and microglia density using histological, immunostaining and immunoblotting techniques. We found that caffeine blocked high cholesterol diet-induced increases in extravasation of IgG and fibrinogen, increases in leakage of Evan's blue dye, decreases in levels of the tight junction proteins occludin and ZO-1, increases in astrocytes activation and microglia density where IgG extravasation was present. Chronic ingestion of caffeine protects against high cholesterol diet-induced increases in disruptions of the BBB, and caffeine and drugs similar to caffeine might be useful in the treatment of Alzheimer's disease.

Cerebral vascular dysfunction during hypercholesterolemia

BACKGROUND AND PURPOSE

Studies of peripheral arteries in hypercholesterolemic animals suggest that increased generation of superoxide contributes to endothelial dysfunction, especially in the presence of atherosclerotic lesions. We tested the hypothesis that vasomotor function is impaired in cerebral arterioles during hypercholesterolemia through a mechanism that involves oxidative stress.

METHODS

Apolipoprotein E-deficient (apoE(-/-)) mice were fed a normal or a high-fat diet for >6 months. ApoE(+/-) mice fed a normal diet were used as normocholesterolemic controls. Responses of cerebral arterioles were examined in open cranial windows in vivo in anesthetized mice.

RESULTS

In apoE(-/-) mice, intimal area was increased only in the proximal aorta on the normal diet and also markedly increased in the distal aorta on the high-fat diet. There were no increases in intimal area in the aortas of control mice or in the cerebral arterioles in any group. The dilator response of cerebral arterioles to ACh (10 micromol/L) in control mice (26+/-4% increase in diameter) was reduced in apoE(-/-) mice on either the normal (13+/-2%) or the high-fat (13+/-3%) diet (P<0.05 vs control). NADPH (10 micromol/L), a substrate for NADPH oxidase, produced dilator responses in control mice (8+/-4%) that were significantly increased in apoE(-/-) mice on the high-fat diet (16+/-2%, P<0.05 vs control). Tempol, a superoxide scavenger, and apocynin, an inhibitor of NADPH oxidase, significantly increased vasodilator responses to ACh and decreased vasodilation to NADPH in apoE(-/-) mice on the high-fat diet. Nitroprusside produced a similar dilatation in the cerebral arterioles of all groups.

CONCLUSIONS

Hypercholesterolemia is associated with oxidative stress and endothelial dysfunction in cerebral arterioles, despite the absence of atherosclerotic lesions.

Statins in stroke: prevention, protection and recovery

Stroke is the third most common cause of death and the leading cause of neurological disability in the USA. While some risk factors for stroke, such as hypertension and cigarette smoking, are well defined, the role of cholesterol in stroke pathogenesis is debated. However, numerous studies in the past decade have shown that medications that reduce cholesterol via 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibition (statins) reduce the incidence of ischemic stroke in patients who are known to have, or be at high risk of, coronary artery disease. In addition, statins may have benefits in neuroprotection and recovery after stroke. The mechanisms by which statins protect against, and improve outcome after, stroke probably extend beyond lipid lowering.

Lipids and stroke: the opportunity of lipid-lowering treatment

Dyslipemia is a clear risk factor (RF) for ischemic heart disease and peripheral artery disease, but its relation with ischemic stroke (IS) is not so clear. HMG-CoA reductase inhibitor drugs or statins (simvastatin, atorvastatin, pravastatin) reduce the relative risk of IS by between 18 and 51% in patients with IHD, in patients with high vascular disease risk and in hypertensive patients with other RFs, acute coronary syndrome, and type 2 diabetes mellitus. According to the guidelines for use, statins are indicated in the majority of patients with IS since the risk is equivalent to that of IHD or high vascular disease risk. In view of the existing clinical evidence of benefit, it would not seem unreasonable to proceed with treatment of patients using statins while awaiting specific studies justifying their use. The non-lipid-lowering mechanisms of the statins and results of studies, such as the Heart Protection Study, provide evidence for widening the indications of statins beyond the prevention of dyslipemia, as a new therapeutic approach in the prevention of IS in patients with plasma levels of total cholesterol or low density lipoproteins currently considered within the normal distribution. The neuroprotective role, which these drugs may play in the acute phase of cerebral ischemia, remains to be clarified, but very recent evidence suggests that such patients may also benefit.

Statins and stroke prevention

Data from studies on the benefits of statins in coronary artery disease patients in preventing recurrent primary and secondary cardiac endpoints, as well as ischemic strokes, imply the potential value of statins in recurrent ischemic stroke prevention without coronary artery disease symptoms or, by extension, primary ischemic stroke prevention. However, data on the latter are lacking, although the ongoing Stroke Prevention by Aggressive Reduction in Cholesterol Levels (SPARCL) study is designed to answer that question. Until these data become available, clinicians are justified in using statins to avert recurrent ischemic strokes due to atherosclerosis, especially if elevated total cholesterol, increased low-density lipoprotein cholesterol, and/or reduced high-density lipoprotein cholesterol, as specified in the National Cholesterol Education Program Third Adult Treatment Panel, are present. This article reviews the pathophysiology of atherosclerosis, particularly the major components of atheromas of cholesterol, smooth muscle cells, inflammation, "foam cells," and connective tissue elements. Emphasis is placed on the first three and the results of statin trials in coronary artery disease, as well as the beneficial pleiotrophic effects of statins in ischemic strokes.

[Statins and prevention of strokes]

Statins have become a leading prescription drug in France. Indications have been greatly extended over the last five years subsequent to publication of many multicentric prospective trials. Besides their preventive properties for coronary artery disease, their efficacy for the prevention of stroke also appears to be demonstrated in coronary patients (CARE and LIPID studies) and in subjects at risk (HPS and ASCOT-LLA studies) irrespective of the serum cholesterol level, the relative risk of stroke being decreased by 30 percent compared with placebo. This preventive capacity would involve pathways other than cholesterol and/or LDL-cholesterol lowering mechanisms, and would probably involve a direct effect on inflammation, coagulation, modulation of certain atherogenic processes, and endothelial function. There remains however certain questions concerning the exact role of statins on secondary prevention of stroke (SPARCL study), their real usefulness in the elderly subject (PROSPER study), and the relative superiority of individual statins.

Arterial stiffness and stroke in hypertension: therapeutic implications for stroke prevention

Stroke is the second leading cause of mortality worldwide, and the leading cause of death in China and Japan. Its prevention represents a major goal. Identification of primary stroke risk, particularly through newly individualised risk factors including biomarkers of large artery damage such as arterial stiffening, is necessary for determining the appropriate level of intervention. The purpose of this review is to focus on the pathophysiology of arterial stiffness, its predictive value for stroke and the therapeutic implications of this risk factor for stroke prevention. The predictive value of arterial stiffness for stroke was demonstrated in a longitudinal study that included 1715 patients with essential hypertension and measurements of carotid-femoral pulse wave velocity (PWV) [an indicator of arterial stiffness] at entry. Over a mean follow-up period of 7.9 years, during which 25 fatal strokes occurred, PWV significantly predicted stroke (relative risk = 1.39 [(95% CI 1.08, 1.72]; p = 0.02 for each 4 m/sec increase) independently of classical cardiovascular risk factors, including age, cholesterol level, diabetes mellitus, smoking and mean blood pressure. Additional longitudinal studies are needed to confirm the predictive value of aortic stiffness on primary and secondary events, in low- and high-risk populations, in various countries, and using different methodologies of arterial stiffness measurement. Drug treatment could prevent stroke through a reduction in arterial stiffness in parallel with correction of cardiovascular risk factors such as hypertension, dyslipidaemia, diabetes mellitus and smoking, all of which are associated with arterial stiffening. In view of the important local actions of angiotensin II on arterial stiffening, drugs interfering with the renin-angiotensin-aldosterone system should be particularly effective. Promising therapeutic strategies to reduce arterial stiffness include taking advantage of the non-lipid-lowering effects of statins and directly targeting the molecular events leading to arterial stiffening, such as formation of advanced glycation end products.

Risk factors for first-ever acute ischemic non-embolic stroke in elderly individuals

BACKGROUND

Stroke is a leading cause of mortality and subsequent serious long-term physical and mental disability among survivors. In the elderly, ischemic stroke accounts for more than 80% of all strokes.

OBJECTIVES

To identify major risk factors for a first-ever acute ischemic/non-embolic stroke in individuals older than 70 years.

METHODS

A population-based case-control study of patients admitted to the University Hospital of Ioannina, Epirus, Greece, due to first-ever ischemic/non-embolic stroke from March 1997 to January 2002. All patients were subjected to brain CT and had their serum lipids and biochemical metabolic parameters determined within 24 h from the onset of symptoms.

RESULTS

A total of 163 (aged>70 years) consecutive stroke patients and 166 apparently healthy volunteers were studied. An atherogenic lipid profile and metabolic disturbances were more prevalent in the patient group than in stroke-free controls. Multivariate logistic regression analysis identified diabetes mellitus (odds ratio (OR), 1.92; 95% CI, 1.02-3.63), triglycerides (TG) (OR, 1.16; 95% CI, 1.09-1.22), HDL-cholesterol (OR, 0.57; 95% CI, 0.43-0.76), apo A-I (OR, 0.80; 95% CI, 0.70-0.92), lipoprotein(a) [LP(a)] (OR, 1.51; 95% CI, 1.25-1.79), uric acid (OR, 1.30; 95% CI, 1.06-1.59) albumin (OR, 0.38; 95% CI, 0.20-0.70) fibrinogen (OR, 1.10; 95% CI, 1.05-1.13) and the metabolic syndrome (OR 2.48, 95% CI, 1.16-5.29) as significantly associated with ischemic/non-embolic stroke.

CONCLUSION

Ischemic non-embolic stroke in the elderly is associated with dyslipidemia and several predictor metabolic factors, which could be substantially modified by lifestyle changes and therapeutic intervention.

Cholesterol in neurologic disorders of the elderly: stroke and Alzheimer’s disease

Mechanisms for the regulation of intracellular cholesterol levels in various types of brain and vascular cells are of considerable importance in our understanding of the pathogenesis of a variety of diseases, particularly atherosclerosis and Alzheimer's disease (AD). It is increasingly clear that conversion of brain cholesterol into 24-hydroxycholesterol and its subsequent release into the periphery is important for the maintenance of brain cholesterol homeostasis. Recent studies have shown elevated plasma concentrations of 24-hydroxycholesterol in patients with AD and vascular dementia, suggesting increased brain cholesterol turnover during neurodegeneration. The oxygenases involved in the degradation and excretion of cholesterol, including the cholesterol 24-hydroxylase and the 27-hydroxylase, are enzymes of the cytochrome P-450 family. This review focuses on the newly recognized importance of cholesterol and its oxygenated metabolites in the pathogenesis of ischemic stroke and AD. The reduction in stroke and AD risk in patients treated with cholesterol-lowering statins is also discussed.

Recent trends in (under)treatment of hypercholesterolaemia in the Netherlands

AIM

To assess recent trends in undertreatment of hypercholesterolaemia (1998-2002).

METHODS

Data were obtained from the third cross-sectional examination of the Monitoring Project on Risk Factors for Chronic Diseases (n = 4878; age 31-70 years), conducted in the Netherlands. Treatment eligibility was established according to Dutch guidelines. Data from the second examination (1993-1997) were used to assess time trends. The association between demographic variables, cardiovascular disease risk factors, drug use and lipid-lowering medication was assessed using multivariable logistic regression.

RESULTS

Overall, 45.9%[95% confidence interval (CI) 41.4, 50.4] of respondents eligible for treatment were treated, and 17.4% (95% CI 13.9, 20.9) were both treated and controlled (1998-2002). Treatment increased significantly after 1995, showed a slight decrease in subsequent years until 2000, when treatment increased again. Subgroups less frequently treated for primary prevention included among others males [odds ratio (OR) = 0.08; 95% CI 0.03, 0.21], younger patients (OR = 0.93 per year; 95% CI 0.88, 0.98), diabetics (OR = 0.19; 95% CI 0.07, 0.56), untreated hypertensives (OR = 0.21; 95% CI 0.09, 0.49) and current smokers (OR = 0.09; 95% CI 0.03, 0.25). In secondary prevention, patients with a history of stroke were less likely to receive treatment (OR = 0.41; 95% CI 0.18, 0.94) compared with patients with a history of ischaemic heart disease.

CONCLUSIONS

Treatment of hypercholesterolaemia has steadily increased over the past 10 years in the Netherlands. However, at present still less than one out of two eligible for treatment is treated, and only about one out of six is both treated and controlled.

Cerebral microvascular responses to hypercholesterolemia: roles of NADPH oxidase and P-selectin

Although hypercholesterolemia is widely accepted as a major risk factor for coronary artery and peripheral vascular diseases, its role in the pathogenesis of stroke is controversial. The objectives of this study were to determine how hypercholesterolemia affects the cerebral microcirculation under resting conditions and after ischemia-reperfusion (I/R). Platelet- and leukocyte-endothelial cell interactions and oxidant production (using the oxidant-sensitive fluorochrome dihydrorhodamine-123) were monitored by intravital videomicroscopy in the cerebral microvasculature of mice placed on either a normal (ND) or cholesterol-enriched diet (HCD). Platelets labeled with carboxyfluorescein diacetate succinimidyl ester (CFDASE) and leukocytes labeled with rhodamine 6G were seen to roll and firmly adhere, with a corresponding increase in oxidant production, in venules of mice on HCD, but not ND. Immunoneutralization of P-selectin attenuated the platelet- and leukocyte-endothelial cell interactions and the enhanced oxidant production associated with HCD. A GPIIb/IIIa blocking antibody did not alter the blood cell-vessel wall interactions to HCD. Mice deficient in the NADPH oxidase subunit gp91(phox) exhibited significantly blunted platelet and leukocyte recruitment responses to HCD. Focal I/R also elicited inflammatory and prothrombogenic responses in cerebral venules and these were exaggerated in mice on HCD. These results implicate an oxidant-dependent, P-selectin-mediated mechanism in the blood cell-vessel wall interactions induced by hypercholesterolemia in the brain and demonstrate that the deleterious effects of I/R on the brain are exacerbated by this cardiovascular risk factor.

Cholesterol and the risk of ischemic stroke

BACKGROUND AND PURPOSE

Large epidemiological studies have not established cholesterol levels as a risk factor for ischemic stroke, but recent clinical trials have demonstrated a reduction in the ischemic stroke rate for patients taking HMG-CoA reductase inhibitors ("statins"). The goal of this study was to evaluate whether total cholesterol (TC), high-density lipoprotein (HDL), triglycerides, and the TC:HDL ratio are risk factors for ischemic stroke in apparently healthy men enrolled in the Physicians' Health Study.

METHODS

We used a nested case-control study design and matched 296 ischemic stroke cases with an equal number of controls on age, tobacco use, and follow-up time. At baseline, TC, HDL, and triglyceride levels were measured. We calculated odds ratios (ORs) and their 95% confidence intervals (CIs) using conditional logistic regression, adjusting for major risk factors for ischemic stroke.

RESULTS

Compared with the reference lowest quartile, the highest quartile for TC had an adjusted OR of 1.56 (95% CI, 0.84 to 2.92), the highest quartile of HDL had an adjusted OR of 0.75 (95% CI, 0.43 to 1.30), and the highest quartile of triglycerides had an adjusted OR of 1.07 (95% CI, 0.63 to 1.82). Although the highest quartile of the TC:HDL ratio had an adjusted OR of 1.62 (95% CI, 0.93 to 2.82), the risk of ischemic stroke was not a linear relationship.

CONCLUSIONS

After adjustment, TC, HDL, and triglycerides were not significantly associated with ischemic stroke risk, and for the TC:HDL ratio, a suggestion of increased risk of ischemic stroke was limited to those with the highest levels.

Effects of cholesterol and inflammation-sensitive plasma proteins on incidence of myocardial infarction and stroke in men

BACKGROUND

Although cholesterol is a major cardiovascular risk factor, its association with stroke remains controversial. This study explored whether the cholesterol-related incidence of stroke and myocardial infarction is modified by plasma markers of inflammation in a large, population-based cohort with a long follow-up.

METHODS AND RESULTS

Plasma cholesterol and 5 inflammation-sensitive plasma proteins (ISP) (fibrinogen, alpha1-antitrypsin, haptoglobin, ceruloplasmin, and orosomucoid) were determined in 6063 healthy men, 28 to 61 years of age. The incidence of stroke, cardiac events (fatal and nonfatal), and cardiovascular deaths was compared between groups defined by levels of cholesterol and ISP. Mean follow-up was 18.7 years. High ISP level was defined as 2 to 5 ISP in the top quartile. High cholesterol was associated with higher levels of ISP. Hypercholesterolemia (> or =6.5 mmol/L, 251 mg/dL) was associated with an increased incidence of ischemic stroke and cardiac events and with a reduced incidence of intracerebral hemorrhage. The ISP levels modified these associations. After risk factor adjustment, men with hypercholesterolemia and high ISP levels had a significantly higher risk of cardiovascular death (relative risk [RR]=2.4; CI, 1.8 to 3.3), cardiac events (RR=2.3; CI, 1.8 to 3.0), and ischemic stroke (RR=2.1; CI, 1.4 to 3.3) than men with normal cholesterol and low ISP levels. In the absence of high ISP levels, hypercholesterolemia was associated with a moderately higher risk of cardiovascular death (RR=1.4; CI, 1.0 to 2.0) and cardiac events (RR=1.5; CI, 1.2 to 1.9) but not significantly with ischemic stroke (RR=1.25; CI, 0.8 to 2.0).

CONCLUSIONS

Hypercholesterolemia is associated with high plasma levels of ISP. These proteins increase the cholesterol-related incidence of cardiovascular diseases. In the absence of elevated ISP levels, no statistically confirmed association was found between hypercholesterolemia and ischemic stroke.

Stroke prevention therapy beyond antithrombotics: unifying mechanisms in ischemic stroke pathogenesis and implications for therapy: an invited review

BACKGROUND

It is estimated that about half of cardiovascular disease risk is explained by conventional risk factors. The realization that atherosclerosis is an inflammatory disease has led to a search for new stroke and cardiovascular disease risk factors and treatments. As such, the vulnerable atherosclerotic plaque has become the main focus for new medical strategies for plaque stabilization and stroke prevention.

SUMMARY OF REVIEW

In this invited review, I discuss inflammation as a possible risk factor for stroke, unifying mechanisms in ischemic stroke pathogenesis, and new avenues for stroke prevention---statin agents, angiotensin-converting enzyme inhibitors, and vitamins. These new stroke prevention therapies may help to reduce inflammation, serve to stabilize the atherosclerotic plaque, or act by other protective mechanisms.

CONCLUSION

Beyond the traditional antithrombotic agents, statin agents, angiotensin-converting enzyme inhibitors, and vitamins may prove to be important additions to our armamentarium for stroke prevention.

Lowering lipids after a stroke or transient ischaemic attack

There is a lot of clinical uncertainty about how to aggressively pursue elevated cholesterol levels in patients following stroke or transient ischaemic attack. This article reviews the evidence linking cholesterol level with stroke and looks at whether treatment with lipid-lowering drugs can be justified.

Polymorphism of the lipoprotein lipase gene and risk of atherothrombotic cerebral infarction in the Japanese

BACKGROUND AND PURPOSE

Lipid and lipoprotein abnormalities have been implicated in the pathogenesis of ischemic cerebrovascular disease and atherosclerosis. Lipoprotein lipase (LPL) plays an important role in plasma lipoprotein metabolism. Several studies have recently reported the presence of a relationship between Ser447Stop mutation of LPL and coronary artery disease. Other polymorphisms (HindIII and PvuII) of the LPL gene have already been shown to correlate significantly with dyslipidemia. We investigated whether these polymorphisms are associated with increased risk of ischemic cerebrovascular disease (CVD).

METHODS

We recruited 177 CVD patients (atherothrombotic infarction, n=71; cardioembolic infarction, n=30; lacunar infarction, n=76) and 177 healthy control subjects. Subjects were genotyped for the Ser447Stop mutation and for HindIII/PvuII restriction fragment length polymorphisms of the LPL gene, and the findings were investigated for associations with the clinical subtypes of CVD and with lipid levels.

RESULTS

The Ser447Stop mutation correlated significantly with CVD (0.107 versus 0.158; P=0.035). For the CG+GG versus CC genotype, the odds ratio between control subjects and CVD patients with atherothrombotic infarction was 0.42 (95% CI, 0.18 to 0.99) (P=0.046). Serum HDL cholesterol and triglyceride levels did not correlate significantly with the Ser447Stop genotype. HindIII polymorphism correlated significantly with CVD (0.234 versus 0.169; P=0.031), but the frequency of PvuII polymorphism was not significantly different between groups.

CONCLUSIONS

Our results suggest that the Ser447Stop mutation of the LPL gene is a novel genetic marker for low risk of atherothrombotic cerebral infarction.

Advantages of lipid-lowering therapy in cerebral ischemia: role of HMG-CoA reductase inhibitors

Dyslipemia as a risk factor for ischemic stroke and indications for statins in the prevention of ischemic stroke are revised. The role of cholesterol levels as a risk factor for ischemic stroke is controversial. This could be due to failures in the design of early epidemiological studies. Recent studies, however, do suggest a clearer risk relationship between cholesterol levels and ischemic stroke. Studies conducted on the prevention of ischemic heart disease (IHD) with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), using pravastatin and simvastatin, unequivocally show reductions in overall mortality, cardiovascular mortality, acute myocardial infarction and other coronary events. These studies show a reduction in the risk of ischemic stroke, and although relative risk reduction is great, absolute risk reduction is low; the reasons for this are analyzed. Apart from lipid mechanisms, statins act on the atheroma plaque; they have antithrombotic and possibly neuroprotecting properties. Statins reduce the number of strokes due to the decrease of atherothrombotic strokes, cardioembolic strokes secondary to IHD, and lacunar strokes related to atherothrombosis and probably to microatheromas. Although there are currently no specific studies available on the secondary prevention of stroke with statins, which are required to clarify certain points, according to European and American guidelines for prevention, statins would be indicated in the secondary prevention of atherothrombotic stroke, and in cardioembolic and lacunar stroke associated with clinical or silent atherosclerosis (IHD, peripheral artery disease). Patients with ischemic stroke of other etiologies, except for stroke in the young or other unusual causes, are patients with a high vascular risk (cardiac and cerebral) owing to the stroke itself, age and other vascular risk factors, and they should also be treated with statins, at least from the point of view of primary prevention of IHD. Natural statins (pravastatin and simvastatin) play an essential part in secondary prevention of ischemic stroke, together with antiaggregants, anticoagulants, angiotensin-converting enzyme inhibitors and the treatment of other vascular risk factors.

Nutritional and medical therapy for dyslipidemia in patients with cardiovascular disease

Dyslipidemia is a significant risk factor for the progression of cardiovascular disease, particularly when associated with other risk factors. An understanding of the pathophysiology and risks for patients with atherosclerotic diseases of undertreated dyslipidemia is essential for the healthcare provider. In this article, a review of epidemiologic data regarding the role of lipid levels in cardiovascular disease prognosis is presented. A familiarity with current dietary and drug treatment of lipid disorders is at the core of an evidence-based approach to dyslipidemia management in the patient with established cardiovascular diseases.

Primary stroke prevention

Stroke is one of the leading causes of death and disability worldwide. Although important advances in therapeutic approaches have been made, treatment is still far from satisfactory. Thus, major efforts should be made on stroke prevention. We present evidence-based recommendations for primary stroke prevention. Changes to modifiable risk factors, the role of drugs and surgery are discussed. New markers may help identification of subjects at high risk.

Preventing ischemic stroke. Current approaches to primary and secondary prevention

Preventing stroke is the most important strategy for reducing the cost of this disease. Management of modifiable risk factors, especially hypertension and Oral anticoagulation with warfarin for selected high-risk patients with nonvalvular atrial fibrillation. Carotid endarterectomy for selected patients with carotid artery stenosis greater than 60%. Regular physical exercise. Treatment with statin medications for patients who have coronary artery disease with or without hyperlipidemia. Routine use of antiplatelet medication has no proven role in primary stroke prevention, although aspirin is often prescribed for patients with vascular risk factors who have not yet had symptoms of either stroke or ischemic heart disease. The major strategies for secondary stroke prevention are: Appropriate evaluation to identify the mechanism of the initial stroke. Carotid endarterectomy for patients with symptomatic carotid artery stenosis of 50% or more. Oral anticoagulation with warfarin for patients with nonvalvular atrial fibrillation. Use of various antiplatelet agents, including aspirin, ticlopidine, clopidogrel, and the combination of aspirin and slow-release dipyridamole. Whether treatment of risk factors reduces the risk of secondary stroke is currently being evaluated in clinical trials.

The role of lipoprotein[a] in atherosclerosis

Recent studies confirm and extend previous evidence that lipoprotein (Lp) plays a significant role in atherosclerosis and is one of the top five or six risk factors for cardiovascular disease. In Japanese patients, Lp levels and apo phenotypes are significant predictors for myocardial infarction. Lp levels are significantly higher in ischemic stroke patients than in controls. However, plasma concentrations of Lp are not predictive of ischemic cerebral infarction in either men or women. Serum Lp levels are significantly higher in patients with carotid plaques or measurable intima-media thickness than in controls without. Despite these associations, there is no significant relationship between Lp level and arterial endothelial function, smooth muscle response, or carotid wall thickness, even though other lipid risk factors like low-density lipoprotein cholesterol (LDL-C) and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio are correlated with abnormal arterial function and structure. There is new evidence that the association of Lp with extracellular matrix (ECM) secreted by arterial smooth muscle cells increases two- to threefold the subsequent specific binding of LDL. Alpha-defensins released from activated or senescent neutrophils stimulate the binding of Lp to ECM of endothelial cells. Several factors that affect the accumulation of Lp and oxidized LDL in the arterial intima have been identified. Several recent studies have provided new insights into the physiologic role that Lp might play in compromising fibrinolysis. The interaction of Lp with cells is clearly distinct from that with ECM and with fibrinogen; the regulation sites within Lp and plasminogen for these regulatory molecules are not identical. These recent advances bring us significantly closer to understanding how Lp exerts its atherogenic and thrombogenic properties.