Prospective associations of fasting insulin, body fat distribution, and diabetes with risk of ischemic stroke. The Atherosclerosis Risk in Communities (ARIC) Study Investigators

The importance of blood pressure control in the patient with diabetes

In individuals with diabetes mellitus, higher risk for renal and cardiovascular disease is seen with blood pressure levels >130/80 mm Hg. Findings of several studies, as well as new guidelines, indicate that individuals with diabetes will benefit from more aggressive treatment of hypertension. Angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, diuretics, beta-adrenoceptor blockers, and calcium-channel blockers are effective antihypertensive agents in type 2 diabetes. Moreover, combinations of these agents are frequently required to reach the target blood pressure of <130/80 mm Hg and reduce risk for renal and cardiovascular events. All of these agents have demonstrated benefits in treating patients. Clinical evidence also indicates that the new vasodilating beta-blockers offer advantages beyond blood pressure control, including cardiovascular risk reduction without exacerbating metabolic parameters. With increased awareness of the need for aggressive treatment of hypertension, clinicians can provide significant benefit to their patients with diabetes. The new beta-blockers may play an important role in achieving blood pressure goals.

Profilin acts downstream of LDL to mediate diabetic endothelial cell dysfunction

The changes occurring at the luminal surface of endothelial cells in diabetes and their relevance to endothelial dysfunction are poorly characterized in vivo. In this study, we developed an integrated strategy to discover cell surface proteins associated with diabetes and to test their role in endothelial dysfunction. First, a peptide phage display library was screened over the endothelial surface of the intact aorta or in retinal endothelial cells from diabetic and control rats. Then, we purified profilin-1 as a binding partner for one of the diabetic aorta-specific phage. Profilin was increased in the aortic endothelium of human diabetic individuals and streptozotocin-diabetic rats. Furthermore, overexpressing profilin in rat aortic endothelial cells triggered 3 indicators of endothelial dysfunction: increased apoptosis, elevated expression of ICAM-1, and decreased phosphorylation of the vasodilator-stimulated phosphoprotein, a marker for nitric oxide signaling. The changes in ICAM-1 and vasodilator-stimulated phosphoprotein were recapitulated in the diabetic aorta in vivo. LDL and oxysterols elevated profilin in cultured aortic endothelial cells. Interference with the de novo synthesis of profilin abrogated the LDL-mediated increase in ICAM-1 expression. Finally, profilin expression was markedly elevated in atherosclerotic plaques. These data indicate that profilin contributes to endothelial dysfunction in a pathway that is downstream of LDL.

Cardiovascular events in diabetic and nondiabetic adults with or without history of myocardial infarction

BACKGROUND

Whether diabetic patients without a history of myocardial infarction (MI) have the same risk of coronary heart disease (CHD) events as nondiabetic patients with a history of MI remains controversial. We compared risks of CHD and stroke events and mortality from cardiovascular disease (CVD) in diabetic and nondiabetic men and women with and without a history of MI.

METHODS AND RESULTS

We followed a total of 13 790 African American and white men and women ages 45 to 64 years who participated in the Atherosclerosis Risk in Communities study, beginning in 1987 to 1989. There were 634 fatal CHD or nonfatal MI events, 312 fatal or nonfatal strokes, and 358 deaths from CVD during an average of 9 years of follow-up (125 998 person-years). After adjustment for age, sex, race, Atherosclerosis Risk in Communities field center, and multiple baseline risk factors, patients who had a history of MI without diabetes at baseline had 1.9 times the risk of fatal CHD or nonfatal MI (95% CI, 1.35 to 2.56; P<0.001) compared with diabetic patients without a prior history of MI. The nondiabetic patients with MI also had 1.8 times the risk of CVD mortality compared with diabetic patients without MI (95% CI, 1.22 to 2.72; P=0.003). However, stroke risk was similar between diabetic patients without MI and nondiabetic patients with MI (RR, 1.05; 95% CI, 0.61 to 1.79; P=0.87). We also observed that nondiabetic patients with MI had a carotid artery wall thickness similar to diabetic patients without MI (P=0.77).

CONCLUSIONS

Diabetic patients without MI had lower risk of CHD events and mortality from CVD compared with nondiabetic patients with MI, but stroke risk was similar between these 2 groups.

IGF-I activity may be a key determinant of stroke risk--a cautionary lesson for vegans

IGF-I acts on vascular endothelium to activate nitric oxide synthase, thereby promoting vascular health; there is reason to believe that this protection is especially crucial to the cerebral vasculature, helping to ward off thrombotic strokes. IGF-I may also promote the structural integrity of cerebral arteries, thereby offering protection from hemorrhagic stroke. These considerations may help to explain why tallness is associated with low stroke risk, whereas growth hormone deficiency increases stroke risk--and why age-adjusted stroke mortality has been exceptionally high in rural Asians eating quasi-vegan diets, but has been declining steadily in Asia as diets have become progressively higher in animal products. There is good reason to suspect that low-fat vegan diets tend to down-regulate systemic IGF-I activity; this effect would be expected to increase stroke risk in vegans. Furthermore, epidemiology suggests that low serum cholesterol, and possibly also a low dietary intake of saturated fat--both characteristic of those adopting low-fat vegan diets--may also increase stroke risk. Vegans are thus well advised to adopt practical countermeasures to minimize stroke risk--the most definitive of which may be salt restriction. A high potassium intake, aerobic exercise training, whole grains, moderate alcohol consumption, low-dose aspirin, statin or policosanol therapy, green tea, and supplementation with fish oil, taurine, arginine, and B vitamins--as well as pharmacotherapy of hypertension if warranted--are other practical measures for lowering stroke risk. Although low-fat vegan diets may markedly reduce risk for coronary disease, diabetes, and many common types of cancer, an increased risk for stroke may represent an 'Achilles heel'. Nonetheless, vegans have the potential to achieve a truly exceptional 'healthspan' if they face this problem forthrightly by restricting salt intake and taking other practical measures that promote cerebrovascular health.

Pioglitazone improves insulin sensitivity among nondiabetic patients with a recent transient ischemic attack or ischemic stroke

BACKGROUND AND PURPOSE

The aim of this study was to determine the effectiveness of pioglitazone compared with placebo for improving insulin sensitivity among nondiabetic patients with a recent transient ischemic attack (TIA) or nondisabling ischemic stroke and impaired insulin sensitivity.

METHODS

Eligible subjects were men and women >45 years of age who had no history of diabetes, fasting glucose <7.0 mmol/L, and impaired insulin sensitivity according to an index calculated from insulin and glucose blood levels obtained during an oral glucose tolerance test. Eligible subjects were randomized to pioglitazone 45 mg/d or placebo. After 3 months of therapy, the glucose tolerance test was repeated.

RESULTS

Between July 2000 and June 2001, we performed oral glucose tolerance tests on 75 patients with no history of diabetes, among whom 36 (50%) were found to have impaired insulin sensitivity and fasting glucose <7.0 mmol/L. Among these 36, 20 consented to the trial. Patients assigned to pioglitazone (n=10) and placebo (n=10) were similar in insulin sensitivity, age, obesity, and index event (stroke compared with TIA), but patients assigned to pioglitazone were less likely to be male (4 compared with 9). The mean proportional increase in insulin sensitivity was 62% among patients assigned to pioglitazone compared with a -1% decline among patients assigned to placebo (P=0.0006). Mean C-reactive protein concentration declined from 0.30 to 0.20 mg/L among patients assigned to pioglitazone and increased from 0.41 to 0.45 mg/L among patients assigned to placebo (P=0.06 for comparison of mean change).

CONCLUSIONS

Pioglitazone is effective for improving insulin sensitivity among patients with recent TIA or stroke and impaired insulin sensitivity.

Type 2 diabetes mellitus in adolescence: lipid and cardiovascular risk factors

This review discusses the important consequences of dyslipidemia and arteriosclerosis in type 2 diabetes as documented in studies in adults. It then examines the relatively recent upsurge in type 2 diabetes in children and adolescents, its characteristics, and its importance in directing our attention to cardiovascular risk factors in this age group. The discussion concludes with an examination of the information available about arteriosclerosis in the young and about the treatment of hypercholesterolemia in children and adolescents.

Plasma lipid profile and incident ischemic stroke: the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND AND PURPOSE

The role of circulating lipids and lipoproteins in the pathogenesis of ischemic stroke remains uncertain despite 3 decades of research. We examined this issue in a large population-based cohort.

METHODS

Between 1987 and 1989, 14 175 middle-aged men and women, free of clinical cardiovascular disease, took part in the first examination of the Atherosclerosis Risk in Communities (ARIC) study cohort. Baseline measurements included plasma levels of LDL cholesterol, HDL cholesterol, apolipoprotein B, apolipoprotein A-1, and triglycerides and myriad risk factors for cardiovascular disease. The cohort was followed for cardiovascular disease end points.

RESULTS

Over an average follow-up of 10 years (142 704 person-years at risk), we documented clinical ischemic stroke in 305 participants (161 men and 144 women). After multivariable adjustment for stroke risk factors, categorical and spline regression analyses of the entire sample, as well as the sample of men alone, revealed weak and inconsistent associations between ischemic stroke and each of the 5 lipid factors. Among women, the most consistent findings were decreasing risk of ischemic stroke within the top half of the distribution of HDL cholesterol and increasing risk within the lower range of the triglyceride distribution.

CONCLUSIONS

The relation of circulating cholesterol to ischemic stroke does not resemble its well-known relation to coronary heart disease. Either the pathogenesis of a substantial proportion of ischemic strokes does not involve classic atherosclerotic mechanisms, or the effect of plasma lipids on atherogenesis is substantially different in the intracranial vascular bed.

Atherosclerotic Risk Factors in Patients with Ischemic Cerebrovascular Disease

Aggressive treatment of atherosclerotic risk factors can substantially reduce stroke risk in patients with a history of stroke or transient ischemic attack. Data from several recent large clinical trials provide convincing evidence of benefit for a number of specific therapies directed at this population. The authors recommend treatment with ramipril alone or perindopril plus indapamide regardless of blood pressure, provided there is no contraindication. For patients already taking a different angiotensin- converting enzyme (ACE) inhibitor, the authors do not routinely switch agents. The authors recommend use of simvastatin 40 mg per day in patients with a total cholesterol level of 135 mg/dL or greater, provided no contraindication exists. The authors also recommend consideration of gemfibrozil in patients with isolated low high- density lipoprotein levels. In patients with diabetes mellitus, tight glycemic control has not been shown to reduce macrovascular complications such as stroke, but does reduce microvascular complications. However, diabetics should receive especially aggressive treatment of other vascular risk factors. There is no role for post-menopausal hormone replacement therapy in prevention of stroke. Weight loss for overweight patients, regular exercise, and a diet rich in fruits, vegetables, cereals, and fish, as well as low in fat and cholesterol, should be a standard recommendation for this group of patients. Treatment with folic acid, B(6), and B(12) for patients with elevated homocysteine appears rational, though this is unproven. However, there is no benefit to vitamin E, vitamin C, or beta-carotene supplementation. Smokers should stop. For every 43 smokers who quit, one stroke is prevented. Moderate consumption of alcohol (one to two drinks a day) may be beneficial, but heavy alcohol use (more than five drinks a day) increases stroke risk.

Risk factor groupings related to insulin resistance and their synergistic effects on subclinical atherosclerosis: the atherosclerosis risk in communities study

The extent to which groupings of insulin resistance-related cardiovascular risk factors synergize to produce atherosclerosis beyond what is expected from their additive effects is uncertain. The objective of this study was to measure interactions among groupings of the features of the insulin resistance syndrome (IRS) on carotid intimal-medial thickness (IMT). This cross-sectional study used baseline data from the Atherosclerosis Risk in Communities Study on 11,790 adults aged 45-64 years without diagnosed diabetes, treated dyslipidemia, or coronary heart disease. The main outcome was carotid IMT, assessed using B-mode ultrasound. The excess carotid IMT attributable to each IRS grouping was determined using multiple linear regression models. There were 57 possible combinations of six IRS components (hypertension, hyperinsulinemia, obesity, hypertriglyceridemia, low HDL cholesterol, and hyperglycemia). In multivariate analysis, 29 of the 57 groupings were associated with excess carotid IMT. Individuals with all six IRS components had the greatest excess IMT compared with those without this grouping (71 micro m; 95% CI 40-102 micro m). The groupings most strongly associated with excess carotid IMT included hypertension and hypertriglyceridemia. Interventions aimed at ameliorating the IRS may produce reductions in atherosclerotic risk beyond that predicted by treatment of individual IRS-related risk factors.

Analysis of obesity and hyperinsulinemia in the development of metabolic syndrome: San Antonio Heart Study

OBJECTIVE

To use standardized cut-offs of body mass index (BMI), waist circumference, waist-to-hip ratio, and fasting insulin levels to predict the development of metabolic disorders and metabolic syndrome.

RESEARCH METHODS AND PROCEDURES

We performed an 8-year follow-up study of 628 non-Hispanic whites and 1340 Mexican Americans, ages 25 to 64 years, from the second cohort of the San Antonio Heart Study. We defined metabolic disorders as dyslipidemia (triglycerides > or =2.26 mM or high-density lipoprotein <0.91 mM in men and <1.17 mM in women), hypertension (blood pressure > or =140 or >=90 mm Hg, or receiving antihypertensive medications), and type 2 diabetes (fasting glucose > or =7.0 mM, 2-hour test glucose > or =11.1 mM, or receiving anti-diabetic medications). People with at least two metabolic disorders were defined as having metabolic syndrome.

RESULTS

High waist-to-hip ratio and fasting insulin levels were significant predictors of developing metabolic syndrome. High anthropometric indices remained significant predictors of metabolic syndrome after adjusting for fasting insulin. Waist circumference, BMI, and insulin had similar areas under the receiver operating characteristic curves (0.74 to 0.76). Further multivariate analyses combining these indices showed minimal increase in prediction. Of subjects who had a combination of high BMI (> or =30 kg/m(2)) and high waist circumference (above "Action Level 2"), 32% developed metabolic syndrome, compared with 10% of subjects with both low BMI and low waist circumference.

DISCUSSION

These findings support the National Institutes of Health recommendations for reducing the risk of metabolic syndrome. Adjustment for baseline fasting insulin levels had only a small effect on the ability of anthropometric indices to predict the metabolic syndrome.

UKPDS 60: risk of stroke in type 2 diabetes estimated by the UK Prospective Diabetes Study risk engine

BACKGROUND AND PURPOSE

People with type 2 diabetes are at elevated risk of stroke compared with those without diabetes. Relative risks have been examined in earlier work, but there is no readily available method for predicting the absolute risk of stroke in a diabetic individual. We developed mathematical models to estimate the risk of a first stroke using data from 4549 newly diagnosed type 2 diabetic patients enrolled in the UK Prospective Diabetes Study.

METHODS

During 30 700 person-years of follow-up, 188 first strokes (52 fatal) occurred. Model fitting was carried out by maximum likelihood estimation using the Newton-Raphson method. Diagnostic plots were used to compare survival probabilities calculated by the model with those calculated using nonparametric methods.

RESULTS

Variables included in the final model were duration of diabetes, age, sex, smoking, systolic blood pressure, total cholesterol to high-density lipoprotein cholesterol ratio and presence of atrial fibrillation. Not included in the model were body mass index, hemoglobin A1c, ethnicity, and ex-smoking status. The use of the model is illustrated with a hypothetical study power calculation.

CONCLUSIONS

This model forecasts the absolute risk of a first stroke in people with type 2 diabetes using variables readily available in routine clinical practice.

Homeostasis model assessment of insulin resistance in relation to the incidence of cardiovascular disease: the San Antonio Heart Study

OBJECTIVE

The prospective association between insulin levels and risk of cardiovascular disease (CVD) is controversial. The objective of the present study was to investigate the relationship of the homeostasis model assessment of insulin resistance (HOMA-IR), as well as insulin levels, with risk of nonfatal and fatal CVD over the 8-year follow-up of the San Antonio Heart Study.

RESEARCH DESIGN AND METHODS

Between 1984 and 1988, randomly selected Mexican-American and non-Hispanic white residents of San Antonio participated in baseline examinations that included fasting blood samples for glucose, insulin, and lipids, a glucose tolerance test, anthropometric measurements, and a lifestyle questionnaire. Between 1991 and 1996, 2,569 subjects who were free of diabetes at baseline were reexamined using the same protocol.

RESULTS

Over the follow-up period, 187 subjects experienced an incident cardiovascular event (heart attack, stroke, heart surgery, angina, or CVD death). Logistic regression analysis indicated that risk of a CVD event increased across quintiles of HOMA-IR after adjustment for age, sex, and ethnicity (P for trend <0.0001; quintile 5 vs. quintile 1, odds ratio [OR] 2.52, 95% CI 1.46-4.36). Additional adjustment for LDL, triglyceride, HDL, systolic blood pressure, smoking, alcohol consumption, exercise, and waist circumference only modestly reduced the magnitude of these associations (P for trend 0.02; quintile 5 vs. quintile 1, OR 1.94, 95% CI 1.05-3.59). Furthermore, there were no significant interactions between HOMA-IR and ethnicity, sex, hypertension, dyslipidemia, glucose tolerance (impaired glucose tolerance versus normal glucose tolerance), or obesity. The magnitude and direction of the relationship between insulin concentration and incident CVD were similar.

CONCLUSIONS

We found a significant association between HOMA-IR and risk of CVD after adjustment for multiple covariates. The topic remains controversial, however, and additional studies are required, particularly among women and minority populations.

LPL polymorphism predicts stroke risk in men

Variation in lipid levels has been associated with atherosclerotic vascular disease, including stroke. Genes contributing to interindividual variation in lipid levels may play a role in the etiology of stroke, either through their effects on lipid synthesis and metabolism or through separate pathways. For this reason, we sought to examine the association between polymorphisms in the lipoprotein lipase (LPL) and apolipoprotein E (APOE) genes and subclinical and clinical stroke in the Atherosclerosis Risk in Communities (ARIC) Study. Subclinical stroke was determined by cerebral magnetic resonance imaging (MRI). Subclinical cerebral infarct cases (n = 197) were compared to a stratified random sample identified from individuals participating in the MRI examination (n = 200). Incidence of clinical ischemic stroke was determined by following the ARIC cohort for an average of 7.5 years for potential cerebrovascular events; 218 validated clinical ischemic strokes were identified. A stratified random sample of the ARIC cohort (CRS, n = 964) was used as the comparison group for clinical cases. The LPL S291-carrying genotypes and APOE epsilon2- and epsilon4-carrying genotypes were not significantly associated with subclinical or clinical stroke. The LPL X447-containing genotypes were significantly associated with subclinical (odds ratio [OR], 4.32; 95% confidence interval [CI], 1.23-15.15; P = 0.020) and clinical stroke (hazard rate ratio [HRR], 2.57; 95% CI, 1.24-5.34; P = 0.01) in men, both by themselves and after adjustment for multiple stroke risk factors. The LPL S447X polymorphism is significantly associated with subclinical cerebral infarction and incident clinical ischemic stroke in men from a middle-aged American population. This association does not appear to be mediated by triglyceride, high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)-cholesterol levels, or additional stroke risk factors.

Effect of the treatment of Type II diabetes mellitus on the development of cognitive impairment and dementia

BACKGROUND

There is increasing interest in preventing cognitive impairment and dementia in later life. Epidemiological evidence shows a relationship between cognitive impairment and Type II diabetes. This association is stronger in patients who have been diagnosed for longer periods of time and in those who are on insulin therapy. There is little information on the short- and long-term influence of type of treatment and level of metabolic control on cognitive function of people with diabetes.

OBJECTIVES

To assess the effects of different types and intensities of treatments for Type II diabetes on cognitive function.

SEARCH STRATEGY

The Cochrane Control Trials Register, MEDLINE, EMBASE, PsycINFO, SIGLE LILACS and CINAHL as well as a number of ongoing trials databases were searched on 11 June 2002 using appropriate strategies.

SELECTION CRITERIA

Randomized controlled trials in which different treatments for Type II diabetes have been compared and in which measures of cognitive function were made at entry and after the treatment.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality. Five trials were identified for possible inclusion but none of them could be included. In one, cognitive function was assessed before and after intensive or conventional diabetic treatment, but the comparison was not double-blind. The three other studies explored the effect of different treatments on QOL but did not include appropriate evaluation of cognitive function. The fifth did not report baseline data on cognitive function in the trial groups.

MAIN RESULTS

No studies were found to be appropriate for inclusion in meta-analysis.

REVIEWER'S CONCLUSIONS

There is no convincing evidence relating type or intensity of diabetic treatment to the prevention or management of cognitive impairment in Type II diabetes. Future research on treatments for diabetes should include standardized assessments of cognitive function as outcome measures.

Body fat distribution, obesity, overweight and stroke incidence in women and men: the NHANES I Epidemiologic Follow-up Study

OBJECTIVE

To test the hypothesis that an elevated ratio of subscapular to triceps skinfold thickness (SFR), a measure of truncal obesity, is associated with increased incidence of stroke independent of overweight.

DESIGN

Data from the NHANES I Epidemiologic Follow-up Study were analyzed.

SUBJECTS

A cohort of 3652 women and 3284 men with complete data who had no history of stroke at baseline in 1971-1975.

MEASUREMENTS

Incidence of stroke diagnosed at hospital discharge or death during the follow-up period through 1992; triceps and subscapular skinfold thickness (SSF) and body mass index (BMI) at baseline.

RESULTS

In a complex relationship, higher SFR was associated with a mildly but significantly increased incidence of stroke only in white male former smokers. In white men, SSF showed a U-shaped association with stroke risk. In white men, stroke risk was elevated in the top quartile of BMI only in never smokers. In black women, stroke risk was significantly elevated in the bottom compared to the top quartile of BMI. No significant associations were seen in white women or black men.

CONCLUSIONS

In white men, SSF showed a U-shaped association with stroke risk, which was elevated in the top quartile of BMI only in never smokers. Surprisingly, stroke risk was elevated in black women with the lowest BMI. More studies of these associations are needed, especially in black women.

New insights into insulin resistance pathophysiology: how it affects glucose and lipid metabolism

Insulin resistance is a metabolic state encountered in many physiological and physiopathological conditions. Its pivotal effect on glucose and lipid metabolism is increasingly recognised. Over the last few years, numerous molecular/intracellular pathways affected by this condition have been elucidated. The author reviews some recent findings underlying several major metabolic abnormalities. An overview of current and future therapeutics is also provided.

Whole grain intake and risk of ischemic stroke in women

In a recent prospective study, whole grain intake was associated with a reduced risk of ischemic stroke. Refined grain, however, did not elicit such protection. Given the potential health benefits associated with whole grain diets, further exploration on the effects of whole grains on health and risk of chronic disease is warranted.

G-protein beta3 subunit and alpha-adducin polymorphisms and risk of subclinical and clinical stroke

BACKGROUND AND PURPOSE

Essential hypertension is a significant risk factor for stroke. Genes contributing to interindividual variation in blood pressure levels and essential hypertension status may play a role in the etiology of stroke either through their effects on blood pressure levels or through separate pathways. For this reason, we sought to examine the association between the alpha-adducin (ADD1) G/W460 and G-protein beta3 subunit (GNbeta3) 825C/T polymorphisms and subclinical and clinical stroke in the Atherosclerosis Risk in Communities (ARIC) Study.

METHODS

Subclinical stroke was determined by cerebral MRI. Subclinical cerebral infarct cases (n=202) were compared with a stratified random sample (MRI-CRS) identified from individuals participating in the MRI examination (n=211). Incidence of clinical ischemic stroke was determined by following the ARIC cohort for an average of 7.2 years for potential cerebrovascular events; 231 validated clinical ischemic strokes were identified. A stratified random sample of the ARIC cohort (CRS) (n=984) was used as the comparison group for the clinical cases.

RESULTS

The frequency of the ADD1 W460 allele was determined for the subclinical cases (0.12), MRI-CRS (0.16), clinical cases (0.14), and CRS (0.17). The frequency of the GNbeta3 825T allele was determined in whites and blacks, respectively, for the subclinical cases (0.26, 0.73), MRI-CRS (0.31, 0.75), clinical cases (0.36, 0.72), and CRS (0.30, 0.72). The ADD1 W460 and GNbeta3 825T alleles were not significantly associated with subclinical stroke. The ADD1 W460 allele was also not a significant predictor of clinical stroke. The GNbeta3 825T allele was significantly associated with clinical stroke in whites after adjustment for age and sex (hazard rate ratio, 1.45; 95% CI, 1.05 to 2.00) and after further adjustment for multiple stroke risk factors (hazard rate ratio, 1.68; 95% CI, 1.18 to 2.41). The GNbeta3 825T allele was not significantly associated with clinical stroke in blacks for either adjustment model.

CONCLUSIONS

The GNbeta3 gene 825C/T polymorphism is significantly associated with incident clinical ischemic stroke in a white middle-aged American population, but not in blacks. This association does not appear to be mediated by established stroke risk factors, specifically blood pressure levels or hypertension status.

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.

High proinsulin levels precede first-ever stroke in a nondiabetic population

BACKGROUND AND PURPOSE

Diabetic subjects have a 3- to 6-fold increased risk for stroke compared with nondiabetic subjects, and hyperinsulinemia shows strong and consistent associations with a cluster of cardiovascular risk factors. Methods separating proinsulin from (true) insulin have demonstrated proinsulin to be more strongly associated with cardiovascular disease than insulin. The present study evaluates the associations between first-ever stroke, proinsulin, and insulin.

METHODS

In this incident case-referent study of a nondiabetic population, 94 cases of first-ever stroke (59 men and 35 women) were individually age- and sex-matched to 178 referents. Blood sampling was collected before the stroke event. Proinsulin and insulin were measured with highly sensitive 2-site sandwich enzyme-linked immunosorbent assays.

RESULTS

In the study population, high proinsulin concentration more than tripled the risk for first-ever stroke after adjustments for total cholesterol, systolic blood pressure, smoking, body mass index, and insulin, with an odds ratio of 3.4 (95% CI, 1.4 to 8.4). In women the risk was even more pronounced, with an odds ratio of 13.7 (95% CI, 1.3 to 146). Synergy was found between proinsulin and systolic blood pressure. In women, synergy was also found between proinsulin and diastolic blood pressure as well as between insulin and both blood pressures.

CONCLUSIONS

High levels of proinsulin may predict later occurrence of first-ever stroke in a nondiabetic population.

Up-regulation of endothelial nitric oxide activity as a central strategy for prevention of ischemic stroke - just say NO to stroke!

Nitric oxide (NO) produced by the endothelium of cerebral arterioles is an important mediator of endothelium-dependent vasodilation (EDV), and also helps to prevent thrombosis and vascular remodeling. A number of risk factors for ischemic stroke are associated with impaired EDV, and this defect is usually at least partially attributable to a decrease in the production and/or stability of NO. These risk factors include hypertension, high-sodium diets, homocysteine, diabetes, visceral obesity, and aging. Conversely, many measures which may provide protection from ischemic stroke - such as ample dietary intakes of potassium, arginine, fish oil, and selenium - can have a favorable impact on EDV. Protection afforded by exercise training, estrogen replacement, statin drugs, green tea polyphenols, and cruciferous vegetables may reflect increased expression of the endothelial NO synthase. IGF-I activity stimulates endothelial NO production, and conceivably is a mediator of the protection associated with higher-protein diets in Japanese epidemiology and in hypertensive rats. These considerations prompt the conclusion that modulation of NO availability is a crucial determinant of risk for ischemic stroke. Multifactorial strategies for promoting effective cerebrovascular NO activity, complemented by measures that stabilize platelets and moderate blood viscosity, should minimize risk for ischemic stroke and help maintain vigorous cerebral perfusion into ripe old age. The possibility that such measures will also diminish risk for Alzheimer's disease, and slow the normal age-related decline in mental acuity, merits consideration. A limited amount of ecologic epidemiology suggests that both stroke and senile dementia may be extremely rare in cultures still consuming traditional unsalted whole-food diets. Other lines of evidence suggest that promotion of endothelial NO activity may decrease risk for age-related macular degeneration.

Nutritional factors in stroke

Observational studies support the role of modifying lifestyle-related risk factors such as diet, physical activity and alcohol use in stroke prevention. For example, increased Na intake is associated with hypertension, and reduction in salt consumption may significantly lower blood pressure and may reduce stroke mortality. Moderately elevated homocysteine levels may be associated with stroke and are associated with deficiency of dietary intake of folate, vitamin B6 and vitamin B12. Consumption of a diet rich in fruits, vegetables, folate, K, Ca, Mg, dietary fibre, fish and milk may protect against stroke. Regular physical activity may also protect against stroke through its role in controlling various risk factors such as hypertension, diabetes mellitus and obesity. The role of fat intake as a risk factor for stroke remains uncertain, whereas the association between stroke and cholesterol has more convincingly been demonstrated by the recent intervention trials using statins. There is also evidence that a low serum albumin may be causally linked to stroke risk and outcome and that a significant number of stroke patients are undernourished on admission and their nutritional status deteriorates further whilst in hospital. Undernutrition is associated with increasing morbidity and mortality and nutritional supplements may have some beneficial effect on some outcome measures.

Insulin resistance syndrome predicts the risk of coronary heart disease and stroke in healthy middle-aged men: the 22-year follow-up results of the Helsinki Policemen Study

The interpretation of conventional multivariate analyses concerning the relation of insulin to the risk of atherosclerotic disease is complex because of correlations of insulin with other risk factors. Therefore, we applied factor analysis to study the clustering of risk factors in the baseline data of the Helsinki Policemen Study (970 healthy men aged 34 to 64 years) and investigated whether these clusterings predict coronary heart disease (CHD) and stroke risk. Areas under the glucose and insulin response curves (AUC glucose and AUC insulin) were used to reflect glucose and insulin levels during oral glucose tolerance tests. During the 22-year follow-up, 164 men had a CHD event, and 70 men had a stroke. Factor analysis of 10 risk factor variables produced 3 underlying factors: insulin resistance factor (comprising body mass index, subscapular skinfold, AUC insulin, AUC glucose, maximal O(2) uptake, mean blood pressure, and triglycerides), lipid factor (cholesterol and triglycerides), and lifestyle factor (physical activity and smoking). In multivariate Cox models, the age-adjusted hazard ratio for insulin resistance factor during the 22-year follow-up was 1.28 (95% CI 1.10 to 1.50) with regard to CHD risk and 1.64 (95% CI 1.29 to 2.08) with regard to stroke risk. Lipid factor predicted the risk of CHD but not that of stroke, and lifestyle factor predicted a reduced CHD risk. Factor analysis including only 6 risk factor variables proposed to be central components of insulin resistance syndrome (body mass index, subscapular skinfold, AUC insulin, AUC glucose, mean blood pressure, and triglycerides) produced only a single insulin resistance factor that predicted the risk of CHD and stroke independently of other risk factors.