Diabetes mellitus as a risk factor for stroke incidence and mortality in Mexican American older adults

Ischemic brain injury in diabetes and endoplasmic reticulum stress

Diabetes is a widespread disease characterized by high blood glucose levels due to abnormal insulin activity, production, or both. Chronic diabetes causes many secondary complications including cardiovascular disease: a life-threatening complication. Cerebral ischemia-related mortality, morbidity, and the extent of brain injury are high in diabetes. However, the mechanism of increase in ischemic brain injury during diabetes is not well understood. Multiple mechanisms mediate diabetic hyperglycemia and hypoglycemia-induced increase in ischemic brain injury. Endoplasmic reticulum (ER) stress mediates both brain injury as well as brain protection after ischemia-reperfusion injury. The pathways of ER stress are modulated during diabetes. Free radical generation and mitochondrial dysfunction, two of the prominent mechanisms that mediate diabetic increase in ischemic brain injury, are known to stimulate the pathways of ER stress. Increased ischemic brain injury in diabetes is accompanied by a further increase in the activation of ER stress. As there are many metabolic changes associated with diabetes, differential activation of the pathways of ER stress may mediate pronounced ischemic brain injury in subjects suffering from diabetes. We presently discuss the literature on the significance of ER stress in mediating increased ischemia-reperfusion injury in diabetes.

Long term Post-Stroke Functional Outcomes: a comparison of diabetics and non-diabetics

INTRODUCTION

Diabetes mellitus (DM) is known to influence outcomes in the short-term following stroke. However, the impact of DM on long-term functional outcomes after stroke is unclear. We compared functional outcomes periodically over 7 years between diabetic and non-diabetic ischemic stroke patients and investigated the impact of DM on the long-term trajectory of post-stroke functional outcomes. We also studied the influence of age on the diabetes-functional outcome association.

METHODS

This is a longitudinal observational cohort study of 802 acute ischemic stroke patients admitted to the Singapore General Hospital from 2005 to 2007. Functional outcomes were assessed using the modified Rankin Scale (mRS) with poor functional outcome defined as mRS≥3. Follow-up data was determined at 6 months and at median follow-up durations of 29 and 86 months.

RESULTS

Among the 802 ischemic stroke patients studied (mean age 64 ± 12 years, male 63%), 42% had DM. In regression analyses adjusting for covariates, diabetic patients were more likely to have poor functional outcomes at 6 months (OR=2.12, 95% CI: 1.23-3.67) and at median follow-up durations of 29 months (OR=1.96, 95% CI: 1.37-2.81) and 86 months (OR=2.27, 95% CI: 1.58-3.25). In addition, age modulated the effect of DM, with younger stroke patients (≤65 years) more likely to have long term poor functional outcome at the 29-month (p=0.0179) and 86-month (p=0.0144) time points.

CONCLUSIONS

DM was associated with poor functional outcomes following ischemic stroke in the long term with the effect remaining consistent throughout the 7-year follow-up period. Age modified the effect of DM in the long term, with an observed increase in risk in the ≤65 age group but not in the >65 age group.

Independent ischemic stroke risk factors in older Americans: a systematic review

The Framingham Stroke Risk Profile (FSRP) is a validated model for predicting 10-year ischemic stroke risk in middle-aged adults, yet has not been demonstrated to consistently translate in older populations. This is a systematic review of independent risk factors measured among > 65 year olds, with subsequent first ischemic stroke, using PRISMA guidelines. We appraised peer-reviewed publications that included participants > 65 years old at risk assessment. Combined with other criteria, results were abstracted from 28 papers reporting six types of stroke risk factors: Serologic/Diagnostic, Conventional, Psychosocial, Genetic, Cognitive, and Antibiotic use. These studies demonstrated levels of serum androgens, C-reactive protein, and advanced glycation endproducts; thrombin generation; left ventricular mass; depressive symptoms; phosphodiesterase 4D single nucleotide polymorphisms; coagulation factor XII gene; peak thrombus generation; and lower cognitive functioning were independent risk factors for ischemic stroke in older adults. Plasma adipokines, free fatty acids and antibiotic use did not predict ischemic stroke. Purpose in life and APOEε2 allele were protective for ischemic stroke. This systematic review provides evidence of risk and protective factors for ischemic stroke in older cohorts that are not included in the FSRP. Further studies are needed to understand whether these factors are important enough to comprise a risk score.

Blockade of Acid-Sensing Ion Channels Attenuates Recurrent Hypoglycemia-Induced Potentiation of Ischemic Brain Damage in Treated Diabetic Rats

Diabetes is a chronic metabolic disease and cerebral ischemia is a serious complication of diabetes. Anti-diabetic therapy mitigates this complication but increases the risk of exposure to recurrent hypoglycemia (RH). We showed previously that RH exposure increases ischemic brain damage in insulin-treated diabetic (ITD) rats. The present study evaluated the hypothesis that increased intra-ischemic acidosis in RH-exposed ITD rats leads to pronounced post-ischemic hypoperfusion via activation of acid-sensing (proton-gated) ion channels (ASICs). Streptozotocin-diabetic rats treated with insulin were considered ITD rats. ITD rats were exposed to RH for 5 days and were randomized into Psalmotoxin1 (PcTx1, ASIC1a inhibitor), APETx2 (ASIC3 inhibitor), or vehicle groups. Transient global cerebral ischemia was induced overnight after RH. Cerebral blood flow was measured using laser Doppler flowmetry. Ischemic brain injury in hippocampus was evaluated using histopathology. Post-ischemic hypoperfusion in RH-exposed rats was of greater extent than that in control rats. Inhibition of ASICs prevented RH-induced increase in the extent of post-ischemic hypoperfusion and ischemic brain injury. Since ASIC activation-induced store-operated calcium entry (SOCE) plays a role in vascular tone, next we tested if acidosis activates SOCE via activating ASICs in vascular smooth muscle cells (VSMCs). We observed that SOCE in VSMCs at lower pH is ASIC3 dependent. The results show the role of ASIC in post-ischemic hypoperfusion and increased ischemic damage in RH-exposed ITD rats. Understanding the pathways mediating exacerbated ischemic brain injury in RH-exposed ITD rats may help lower diabetic aggravation of ischemic brain damage.

Acidosis mediates recurrent hypoglycemia-induced increase in ischemic brain injury in treated diabetic rats

OBJECTIVES

Cerebral ischemia is a serious possible manifestation of diabetic vascular disease. Recurrent hypoglycemia (RH) enhances ischemic brain injury in insulin-treated diabetic (ITD) rats. In the present study, we determined the role of ischemic acidosis in enhanced ischemic brain damage in RH-exposed ITD rats.

METHODS

Diabetic rats were treated with insulin and mild/moderate RH was induced for 5 days. Three sets of experiments were performed. The first set evaluated the effects of RH exposure on global cerebral ischemia-induced acidosis in ITD rats. The second set evaluated the effect of an alkalizing agent (Tris-(hydroxymethyl)-aminomethane: THAM) on ischemic acidosis-induced brain injury in RH-exposed ITD rats. The third experiment evaluated the effect of the glucose transporter (GLUT) inhibitor on ischemic acidosis-induced brain injury in RH-exposed ITD rats. Hippocampal pH and lactate were measured during ischemia and early reperfusion for all three experiments. Neuronal survival in Cornu Ammonis 1 (CA1) hippocampus served as a measure of ischemic brain injury.

FINDINGS

Prior RH exposure increases lactate concentration and decreases pH during ischemia and early reperfusion when compared to controls. THAM and GLUT inhibitor treatments attenuated RH-induced increase in ischemic acidosis. GLUT inhibitor treatment reduced the RH-induced increase in lactate levels. Both THAM and GLUT inhibitor treatments significantly decreased ischemic damage in RH-exposed ITD rats.

CONCLUSIONS

Ischemia causes increased acidosis in RH-exposed ITD rats via a GLUT-sensitive mechanism. Exploring downstream pathways may help understand mechanisms by which prior exposure to RH increases cerebral ischemic damage.

Hyperglycemia / hypoglycemia-induced mitochondrial dysfunction and cerebral ischemic damage in diabetics

Enhancement of ischemic brain damage is one of the most serious complications of diabetes. Studies from various in vivo and in vitro models of cerebral ischemia have led to an understanding of the role of mitochondria and complex interrelated mitochondrial biochemical pathways leading to the aggravation of ischemic neuronal damage. Advancements in the elucidation of the mechanisms of ischemic brain damage in diabetic subjects have revealed a number of key mitochondrial targets that have been hypothesized to participate in enhancement of brain damage. The present review initially discusses the neurobiology of ischemic neuronal injury, with special emphasis on the central role of mitochondria in mediating its pathogenesis and therapeutic targets. Later it further details the potential role of various biochemical mediators and second messengers causing widespread ischemic brain damage among diabetics via mitochondrial pathways. The present review discusses preclinical data which validates the significance of mitochondrial mechanisms in mediating the aggravation of ischemic cerebral injury in diabetes. Exploitation of these targets may provide effective therapeutic agents for the management of diabetes-related aggravation of ischemic neuronal damage.

Relationship between blood pressure, cognitive function and education level in elderly patients with diabetes: a preliminary study

AIMS

This study aimed to assess the relationship between blood pressure and cognitive function in elderly patients with diabetes mellitus (DM).

METHODS

A total of 32 patients with DM aged ≥ 65 years (seven women and 25 men; mean ± SD age: 74.3 ± 6.4 years) were included in this cross-sectional study. Relationships between blood pressure and neuropsychological tests were determined using Spearman's rank correlations (ρ) and multivariable linear regression models.

RESULTS

Lower diastolic blood pressure was associated with lower scores on the Frontal Assessment Battery (ρ=0.32, P=0.02), longer times to complete the Trail Making Test Part B (ρ=0.51, P=0.003), lower scores for the Finger Tapping Test (ρ=0.36, P=0.046) and less verbal fluency (ρ=0.36, P=0.047). In multivariable models, these relationships were attenuated after adjusting for levels of education.

CONCLUSION

There was an association between lower diastolic blood pressure and poorer executive function in this cohort of elderly DM patients. These results underline the importance of systematic cognitive evaluation in elderly patients with DM, and suggest that a too-low diastolic blood pressure may have deleterious effects on mental function. Larger studies in the future are required to confirm these preliminary results.

The Influence of Stroke Risk Factors and Comorbidities on Assessment of Stroke Therapies in Humans and Animals

The main driving force behind the assessment of novel pharmacological agents in animal models of stroke is to deliver new drugs to treat the human disease rather than to increase knowledge of stroke pathophysiology. There are numerous animal models of the ischaemic process and it appears that the same processes operate in humans. Yet, despite these similarities, the drugs that appear effective in animal models have not worked in clinical trials. To date, tissue plasminogen activator is the only drug that has been successfully used at the bedside in hyperacute stroke management. Several reasons have been put forth to explain this, but the failure to consider comorbidities and risk factors common in older people is an important one. In this article, we review the impact of the risk factors most studied in animal models of acute stroke and highlight the parallels with human stroke, and, where possible, their influence on evaluation of therapeutic strategies.

Type 2 diabetes among rural Hispanics in Washington State: perspectives from community stakeholders

During February-March 2006, elicitation interviews were conducted with 23 community stakeholders in the Yakima Valley, Washington State, to examine concerns about diabetes and to obtain recommendations for how to address concerns among Hispanics in this rural community. Using a snowball approach, stakeholders were identified from organizations providing care and outreach for Hispanics with diabetes. Interviews were guided by a social ecology approach and were conducted as part of a larger parent study using principles of community-based participatory research. Audiotaped interviews were transcribed and then coded by three staff members who identified common themes independently before meeting to reach consensus. Stakeholders represented health care delivery or social service organizations, churches, or local radio stations. Diabetes was perceived as an important problem among community members, who often underwent delayed diagnosis of the disease. Lack of disease knowledge, access to appropriate information or services, health insurance, and personal responsibility were perceived as barriers. Stakeholders recommended using exiting organizations and businesses as intervention channels, promoting cultural sensitivity of health professionals and volunteers, creating and distributing appropriate information, and organizing activities to promote awareness and disease management. Recommendations have informed the design of community interventions to lessen the impact of diabetes in the Yakima Valley.

The economic consequences of diabetes and cardiovascular disease in the United States

Diabetes-related care and complications constitute a significant proportion of the United States' (US) health care expenditure. Of these complications, cardiovascular disease (CVD) is a major component. Higher morbidity and mortality rates translate to higher costs of care in patients with diabetes compared to those who do not have the disease. Minorities bear a disproportionate burden of diabetes and CVD. We review this disparity and examine potential etiologies for it in Hispanics and African-Americans, the two largest minority groups in the US. We examine strategies in these populations that may improve outcomes in diabetes and CVD, potentially decreasing health care costs.

Relationship between diabetes codes that affect Medicare reimbursement (tier comorbidities) and outcomes in stroke rehabilitation

OBJECTIVES

To examine the extent to which diabetes codes that increase reimbursement (tier comorbidities) under the prospective payment system are related to length of stay and functional outcomes in stroke rehabilitation.

DESIGN

Secondary data analysis.

SETTING

Inpatient rehabilitation facilities (N=864) across the United States.

PARTICIPANTS

Patients (N=135,097) who received medical rehabilitation for stroke in 2002-2003.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Length of stay, FIM instrument, and discharge setting. Diabetes status was assigned to 1 of 3 categories: tier (increases reimbursement), nontier (no reimbursement effect), and no diabetes.

RESULTS

Mean +/- standard deviation age of the sample was 70.4+/-13.4 years, and 31% had diabetes (6% tier, 25% nontier). Diabetes status by age demonstrated significant (P<.05) interaction effects, which lead to the following age-specific findings. In younger stroke patients (60y), tier diabetes was associated with shorter lengths of stay compared with both groups, lower FIM discharge scores compared with both groups, and lower odds of discharge home relative to the no-diabetes group. In older stroke patients (80y), tier diabetes was associated with longer lengths of stay compared with both groups and with higher FIM discharge scores compared with the nontier group.

CONCLUSIONS

The diabetes-related conditions identified as tier comorbidities under the prospective payment system are significant predictors of stroke rehabilitation outcomes, but these relationships are moderated by patient age.

Health related quality of life in older Mexican Americans with diabetes: a cross-sectional study

BACKGROUND

The older Hispanic population of the U.S. is growing at a tremendous rate. While ethnic-related risk and complications of diabetes are widely-acknowledged for older Hispanics, less is known about how health related quality of life is affected in this population.

METHODS

Cross-sectional study assessing differences in health related quality of life between older Mexican Americans with and without diabetes. Participants (n = 619) from the Hispanic Established Population for the Epidemiological Study of the Elderly were interviewed in their homes. The primary measure was the Medical Outcomes Study Short Form (SF-36).

RESULTS

The sample was 59.6% female with a mean age of 78.3 (SD = 5.2) years. 31.2% (n = 193) of the participants were identified with diabetes. Individuals with diabetes had significantly (F = 19.35, p < .001) lower scores on the Physical Composite scale (mean = 37.50, SD = 12.69) of the SF-36 compared to persons without diabetes (mean = 43.04, SD = 12.22). There was no significant difference between persons with and without diabetes on the Mental Composite scale of the SF-36.

CONCLUSION

Diabetes was associated with lower health related quality of life in older Mexican Americans. The physical components of health related quality of life uniformly differentiated those with diabetes from those without, whereas mental component scores were equivocal.

Mortality in pharmacologically treated older adults with diabetes: the Cardiovascular Health Study, 1989-2001

BACKGROUND

Diabetes mellitus (DM) confers an increased risk of mortality in young and middle-aged individuals and in women. It is uncertain, however, whether excess DM mortality continues beyond age 75 years, is related to type of hypoglycemic therapy, and whether women continue to be disproportionately affected by DM into older age.

METHODS AND FINDINGS

From the Cardiovascular Health Study, a prospective study of 5,888 adults, we examined 5,372 participants aged 65 y or above without DM (91.2%), 322 with DM treated with oral hypoglycemic agents (OHGAs) (5.5%), and 194 with DM treated with insulin (3.3%). Participants were followed (1989-2001) for total, cardiovascular disease (CVD), coronary heart disease (CHD), and non-CVD/noncancer mortality. Compared with non-DM participants, those treated with OHGAs or insulin had adjusted hazard ratios (HRs) for total mortality of 1.33 (95% confidence interval [CI], 1.10 to 1.62) and 2.04 (95% CI, 1.62 to 2.57); CVD mortality, 1.99 (95% CI, 1.54 to 2.57) and 2.16 (95% CI, 1.54 to 3.03); CHD mortality, 2.47 (95% CI, 1.89 to 3.24) and 2.75 (95% CI, 1.95 to 3.87); and infectious and renal mortality, 1.35 (95% CI, 0.70 to 2.59) and 6.55 (95% CI, 4.18 to 10.26), respectively. The interaction of age (65-74 y versus > or =75 y) with DM was not significant. Women treated with OHGAs had a similar HR for total mortality to men, but a higher HR when treated with insulin.

CONCLUSIONS

DM mortality risk remains high among older adults in the current era of medical care. Mortality risk and type of mortality differ between OHGA and insulin treatment. Women treated with insulin therapy have an especially high mortality risk. Given the high absolute CVD mortality in older people, those with DM warrant aggressive CVD risk factor reduction.

The brain of the elderly diabetic patient

All available estimations agree that the French population is aging and that the proportion of diabetics in the elderly population is increasing. The prevalence of diabetes could be about 10% in the over 65 y population. The fact that diabetes has an effect on brain function is widely accepted, but there are very few studies providing pertinent details. Diabetes is known to affect brain function, potential consequences including cognitive decline, dementia, depression, and stroke. These complications are frequently associated, leading to poor quality-of-life with considerable social and economic impact. While the results of different studies can be contradictory, there is an overall trend towards the conclusion that diabetes, often associated with high blood pressure, contributes to cognitive decline in elderly diabetics as well as to an increased frequency and severity of cerebral vascular events. These considerations point out the importance of proper management of diabetes in the elderly population and the need for cooperative studies to determine the role of diabetes and different cardiovascular risk factors in the development of dementia, stroke, and depressive syndromes whose consequences are probably underestimated.