Sex differences in stroke

Sex differences in stroke: the contribution of coagulation

Stroke is now the leading cause of adult disability in the United States. Women are disproportionately affected by stroke. Women increasingly outnumber men in the elderly population, the period of highest risk for stroke. However, there is also a growing recognition that fundamental sex differences are present that contribute to differential ischemic sensitivity. In addition, gonadal hormone exposure can impact coagulation and fibrinolysis, key factors in the initiation of thrombosis. In this review we will discuss sex differences in stroke, with a focus on platelets, vascular reactivity and coagulation.

Clinical, lifestyle, socioeconomic determinants and rate of asymptomatic intracranial atherosclerosis in stroke free Pakistanis

BACKGROUND

Intracranial Atherosclerotic Disease (ICAD) is the most frequent etiology of stroke with high prevalence among Asians. Despite this, early determinants of ICAD have not been described from this region.

METHODS

The study is an analytical prospective cross-sectional study of 200 adults from Radiology Departments of two diagnostic centers in Karachi. Eligible participants confirmed the absence of stroke symptoms via the Questionnaire for Verifying Stroke Free Status (QVSFS) and underwent an interview covering medical, socio demographic, lifestyle and anthropometric evaluation using locally validated and standardized definitions. Magnetic Resonance Images (MRI) were centrally reviewed to detect ICAD using the criterion used in the Warfarin-Aspirin Symptomatic Intracranial Disease study. The risk factors associated with asymptomatic ICAD are reported along with prevalence ratios.

RESULTS

Of the 200 participants, ICAD was found in 34.5% (n = 69) of the participants. Mean age was 37.1 (S.D 15.1) years with 62% younger than 45 years. Self-reported hypertension was found in 26.5% subjects, diabetes in 9%, dyslipidemia in 5% and depression in 60%. Smokeless tobacco (Adjusted PR 3.27 (1.07-6.05)), Western diet, high socioeconomic status (Adjusted PR 2.26 (1.99-5.62)) and dyslipidemia (Adjusted PR 1.88 (1.25-2.21)) had significant associations with ICAD after multivariable analysis. Age, gender, diabetes, hypertension, depression and physical activity did not have a significant association.

CONCLUSION

ICAD was found on MRI in one in three asymptomatic Pakistanis and was associated with modifiable risks. Initiatives targeting primary prevention may be able to decrease the burden of disease caused by stroke due to ICAD.

STUDY REGISTRATION NUMBER

NCT02072876 2/25/2014.

Phenotypic changes in immune cell subsets reflect increased infarct volume in male vs. female mice

Inflammatory responses in the brain after cerebral ischemia have been studied extensively in male mice, but not female mice, thus potentially giving a less-than-accurate view of gender associated pathological processes. In humans, cerebral infarcts are typically smaller in premenopausal females than in age-matched males. In the current study, we confirmed smaller infarcts in female vs. male mice after middle cerebral artery occlusion and 96 h of reperfusion. Moreover, we explored immunological alterations related to this difference and found that the percentage of CD4+ T lymphocytes was significantly higher in spleens in males than females, with increased expression of the activation markers, CD69 and CD44. In contrast, the percentage of CD8+ T lymphocytes was significantly higher in spleens of females than males, leading to the identification of a small but distinct population of IL-10-secreting CD8+CD122+ suppressor T cells that were also increased in females. Finally, we observed that males have a greater percentage of activated macrophages/microglia in the brain than females, as well as increased expression of the VLA-4 adhesion molecule in both brain and spleen. This new information suggesting gender-dependent immunological mechanisms in stroke implies that effective treatments for human stroke may also be gender specific.

Impact of BDNF -196 G>A and BDNF -270 C>T polymorphisms on stroke rehabilitation outcome: sex and age differences

BACKGROUND

Genetic factors, including gene polymorphisms, are promising in determining stroke rehabilitation outcome. Brain-derived neurotrophic factor (BDNF) is one of the most attractive because of its role in neuroplasticity and brain repair.

OBJECTIVE

The aim of present study was to assess the role of BDNF -196 G≯A (val66met) and -270 C≯T on clinical parameters and functional outcome in patients with ischemic and hemorrhagic stroke. Additional analyses according to sex and age (≤55 and ≯55 years) were performed.

METHODS

Three hundred thirty-eight patients (287 with ischemic and 51 with hemorrhagic stroke) were evaluated in terms of neurological deficit (National Institute of Heath Stroke Scale [NIHSS]), activities of daily living (Barthel Index [BI]), and everyday functionality (Rankin score [RS]) before and after rehabilitation. BDNF polymorphism genotyping was performed by polymerase chain reaction restriction fragment length polymorphism analysis.

RESULTS

In multivariative analysis, unfavorable outcome of stroke rehabilitation (RS ≥2) was associated with independent factors: ischemic stroke (odds ratio [OR], 2.59; 95% CI, 1.03-6.47), female gender (OR, 2.80; 95% CI, 1.39-5.64), depression (OR, 4.24; 95% CI, 1.45-12.35), falls (OR, 2.61; 95% CI, 1.16-5.87), and BDNF -196 GG polymorphism (OR, 2.18; 95% CI, 1.09-4.35). The differences of functional parameters measured with BI and RS on admission and at discharge are apparent only for comparisons between patients ≤55 and ≯55 years old carrying BDNF -196 GA+AA genotypes but not in those carrying -196 GG genotype; the differences were evident in women but not in men.

CONCLUSIONS

BDNF -196 G≯A polymorphism might affect functional outcome of stroke rehabilitation, but this hypothesis needs further verification.

Role of aromatase in sex-specific cerebrovascular endothelial function in mice

Stroke risk and outcome are strongly modified by estrogen. In addition to ovaries, estrogen is produced locally in peripheral tissue by the enzyme aromatase, and extragonadal synthesis becomes the major source of estrogen after menopause. Aromatase gene deletion in female mice exacerbates ischemic brain damage after stroke. However, it is not clear which cell type is responsible for this effect, since aromatase is expressed in multiple cell types, including cerebrovascular endothelium. We tested the hypothesis that cerebrovascular aromatase contributes to sex differences in cerebrovascular endothelial function. Cerebrocortical microvascular responses to the endothelium-dependent vasodilator ACh were compared between male and female wild-type (WT) and aromatase knockout (ArKO) mice by measuring laser-Doppler perfusion in vivo through a closed cranial window. Additional studies were performed in WT mice treated with the aromatase inhibitor fadrozole or vehicle. WT female mice had significantly greater responses to ACh compared with WT males (P < 0.001), which was associated with higher aromatase expression in female compared with male cerebral vessels (P < 0.05). ACh responses were significantly lower in ArKO compared with WT females (P < 0.05) and in WT females treated with fadrozole versus vehicle (P < 0.001). Conversely, ACh responses were significantly higher in ArKO versus WT males (P < 0.05). Levels of phosphorylated endothelial nitric oxide synthase (eNOS) were lower in ArKO versus WT female brains, but were not altered by aromatase deletion in males. We conclude that cerebrovascular endothelial aromatase plays an important and sexually dimorphic role in cerebrovascular function and that aromatase inhibitors in clinical use may have cardiovascular consequences in both males and females.

Guidelines for the prevention of stroke in women: a statement for healthcare professionals from the American Heart Association/American Stroke Association

PURPOSE

The aim of this statement is to summarize data on stroke risk factors that are unique to and more common in women than men and to expand on the data provided in prior stroke guidelines and cardiovascular prevention guidelines for women. This guideline focuses on the risk factors unique to women, such as reproductive factors, and those that are more common in women, including migraine with aura, obesity, metabolic syndrome, and atrial fibrillation.

METHODS

Writing group members were nominated by the committee chair on the basis of their previous work in relevant topic areas and were approved by the American Heart Association (AHA) Stroke Council's Scientific Statement Oversight Committee and the AHA's Manuscript Oversight Committee. The panel reviewed relevant articles on adults using computerized searches of the medical literature through May 15, 2013. The evidence is organized within the context of the AHA framework and is classified according to the joint AHA/American College of Cardiology and supplementary AHA Stroke Council methods of classifying the level of certainty and the class and level of evidence. The document underwent extensive AHA internal peer review, Stroke Council Leadership review, and Scientific Statements Oversight Committee review before consideration and approval by the AHA Science Advisory and Coordinating Committee.

RESULTS

We provide current evidence, research gaps, and recommendations on risk of stroke related to preeclampsia, oral contraceptives, menopause, and hormone replacement, as well as those risk factors more common in women, such as obesity/metabolic syndrome, atrial fibrillation, and migraine with aura.

CONCLUSIONS

To more accurately reflect the risk of stroke in women across the lifespan, as well as the clear gaps in current risk scores, we believe a female-specific stroke risk score is warranted.

Nationwide incidence of clinically diagnosed retinal vein occlusion in Korea, 2008 through 2011: preponderance of women and the impact of aging

OBJECTIVE

This study aimed at defining the incidence and demographics of clinically diagnosed retinal vein occlusion (RVO) in Korea.

DESIGN

Nationwide population-based retrospective study using data entered into the Korean national health claims database from 2007 through 2011.

PARTICIPANTS

Data of the entire population of Korea (n = 47,990,761, based on the 2010 census) were analyzed.

METHODS

The Korean national health claims database was analyzed to identify patients with RVO. Incident cases included individuals with no RVO claims in 2007, but with RVO claims in the years 2008 through 2011. The incidence rate of RVO was estimated for the entire Korean population.

MAIN OUTCOME MEASURES

The person-time incidence rates of clinically diagnosed RVO in Korea, including the age- and gender-specific incidence rates, were estimated.

RESULTS

A total of 92 730 RVO cases (56.4% in women) were identified. The incidence rate of clinically diagnosed RVO during the study period was 48.31 per 100,000 person-years (95% confidence interval [CI], 48.00-48.62). The incidence rate among men and women was 42.40 (95% CI, 41.99-42.81) and 54.14 (95% CI, 53.67-54.60) per 100,000 person-years, respectively (P < 0.001). The highest incidence of 214.92 per 100,000 person-years (95% CI, 211.29-218.56) was observed in the age group of 70 to 74 years (186.62 [95% CI, 181.46-191.78] and 236.25 [95% CI, 231.21-241.29] per 100,000 person-years for men and women aged 70 to 74 years, respectively). The incidence rate of RVO increased as the age of the population increased-more than doubling approximately every 10 years from the second to the seventh decade of life. Retinal vein occlusion occurred more often in men 30 to 54 years of age and in men older than 85 years, but was more common in women 55 to 84 years of age.

CONCLUSIONS

This study reports the population-based RVO incidence in Korea. The RVO incidence increased exponentially as the age of the population increased, and the RVO incidence in women was 1.28 times higher than that in men.

SDF1-a facilitates Lin-/Sca1+ cell homing following murine experimental cerebral ischemia

BACKGROUND

Hematopoietic stem cells mobilize to the peripheral circulation in response to stroke. However, the mechanism by which the brain initiates this mobilization is uncharacterized.

METHODS

Animals underwent a murine intraluminal filament model of focal cerebral ischemia and the SDF1-A pathway was evaluated in a blinded manner via serum and brain SDF1-A level assessment, Lin-/Sca1+ cell mobilization quantification, and exogenous cell migration confirmation; all with or without SDF1-A blockade.

RESULTS

Bone marrow demonstrated a significant increase in Lin-/Sca1+ cell counts at 24 hrs (272 ± 60%; P<0.05 vs sham). Mobilization of Lin-/Sca1+ cells to blood was significantly elevated at 24 hrs (607 ± 159%; P<0.05). Serum SDF1-A levels were significant at 24 hrs (Sham (103 ± 14), 4 hrs (94 ± 20%, p = NS) and 24 hrs (130 ± 17; p<0.05)). Brain SDF1-A levels were significantly elevated at both 4 hrs and 24 hrs (113 ± 7 pg/ml and 112 ± 10 pg/ml, respectively; p<0.05 versus sham 76 ± 11 pg/ml). Following administration of an SDF1-A antibody, Lin-/Sca1+ cells failed to mobilize to peripheral blood following stroke, despite continued up regulation in bone marrow (stroke bone marrow cell count: 536 ± 65, blood cell count: 127 ± 24; p<0.05 versus placebo). Exogenously administered Lin-/Sca1+ cells resulted in a significant reduction in infarct volume: 42 ± 5% (stroke alone), versus 21 ± 15% (Stroke+Lin-/Sca1+ cells), and administration of an SDF1-A antibody concomitant to exogenous administration of the Lin-/Sca1+ cells prevented this reduction. Following stroke, exogenously administered Lin-/Sca1+ FISH positive cells were significantly reduced when administered concomitant to an SDF1-A antibody as compared to without SDF1-A antibody (10 ± 4 vs 0.7 ± 1, p<0.05).

CONCLUSIONS

SDF1-A appears to play a critical role in modulating Lin-/Sca1+ cell migration to ischemic brain.

PPARγ activation rescues mitochondrial function from inhibition of complex I and loss of PINK1

Parkinson's disease has long been associated with impaired mitochondrial complex I activity, while several gene defects associated with familial Parkinson's involve defects in mitochondrial function or 'quality control' pathways, causing an imbalance between mitochondrial biogenesis and removal of dysfunctional mitochondria by autophagy. Amongst these are mutations of the gene for PTEN-induced kinase 1 (PINK1) in which mitochondrial function is abnormal. Peroxisome proliferator-activated receptor gamma (PPARγ), a nuclear receptor and ligand-dependent transcription factor, regulates pathways of inflammation, lipid and carbohydrate metabolism, antioxidant defences and mitochondrial biogenesis. We have found that inhibition of complex I in human differentiated SHSY-5Y cells by the complex I inhibitor rotenone irreversibly decrease mitochondrial mass, membrane potential and oxygen consumption, while increasing free radical generation and autophagy. Similar changes are seen in PINK1 knockdown cells, in which potential, oxygen consumption and mitochondrial mass are all decreased. In both models, all these changes were reversed by pre-treatment of the cells with the PPARγ agonist, rosiglitazone, which increased mitochondrial biogenesis, increased oxygen consumption and suppressed free radical generation and autophagy. Thus, rosiglitazone is neuroprotective in two different models of mitochondrial dysfunction associated with Parkinson's disease through a direct impact on mitochondrial function.

Poststroke hip fracture: prevalence, clinical characteristics, mineral-bone metabolism, outcomes, and gaps in prevention

Objective. To assess the prevalence, clinical and laboratory characteristics, and short-term outcomes of poststroke hip fracture (HF). Methods. A cross-sectional study of 761 consecutive patients aged ≥60 years (82.3 ± 8.8 years; 75% females) with osteoporotic HF. Results. The prevalence of poststroke HF was 13.1% occurring on average 2.4 years after the stroke. The poststroke group compared to the rest of the cohort had a higher proportion of women, subjects with dementia, history of TIA, hypertension, coronary artery disease, secondary hyperparathyroidism, higher serum vitamin B12 levels (>350 pmol/L), walking aid users, and living in residential care facilities. The majority of poststroke HF patients had vitamin D insufficiency (68%) and excess bone resorption (90%). This group had a 3-fold higher incidence of postoperative myocardial injury and need for institutionalisation. In multivariate analysis, independent indicators of poststroke HF were female sex (OR 3.6), history of TIA (OR 5.2), dementia (OR 4.1), hypertension (OR 3.2), use of walking aid (OR 2.5), and higher vitamin B12 level (OR 2.3). Only 15% of poststroke patients received antiosteoporotic therapy prior to HF. Conclusions. Approximately one in seven HFs occurs in older stroke survivors and are associated with poorer outcomes. Early implementation of fracture prevention strategies is needed.

Stroke: understanding the differences between males and females

Stroke is a significant cause of death and long-term disability in the USA. The incidence, mortality, and outcomes of stroke are significantly different between men and women. As with many diseases that affect men and women differently, an understanding on the reasons underlying those differences is critical to effective diagnosis and treatment. This review will examine the sex differences in stroke in both humans and animal models of stroke and review what is known about potential mechanisms underlying these differences. It is clear that there is a complex interaction between hormonal, genetic, and unknown factors at play in generating the sex differences in stroke.