Glycated Hemoglobin and Risk of Stroke in People Without Known Diabetes in the European Prospective Investigation Into Cancer (EPIC)–Norfolk Prospective Population Study

Association of Glycated Hemoglobin With Acute Ischemic Stroke in a Tertiary Care Center in a Tribal Region of Jharkhand

BACKGROUND

Increased glycated hemoglobin (HbA1c) levels have shown an association with an increased risk of stroke in patients admitted to a tertiary care center in Jharkhand.

OBJECTIVES

To find out and estimate the risk of acute ischemic stroke in patients with increased HbA1c levels compared with controls.

METHODS

This observational case-control study was conducted on patients admitted to the department of general medicine at a tertiary care center in Ranchi from June 2021 to November 2022. The patients included in this study were those aged 18 years or older and who were clinically and radiologically diagnosed with acute ischemic stroke. Only patients with a first episode of stroke were included, and patients with hemorrhagic stroke or transient ischemic attack were excluded from this study. An equal number of control participants were also included. Ion exchange high-performance liquid chromatography was used to perform the HbA1c tests. The same method was used to measure HbA1c levels in the controls. All findings were recorded in a Microsoft Excel sheet (Microsoft Corporation, Redmond, WA), and the data were analyzed using SPSS version 22.0 software (IBM Corp., Armonk, NY). After performing a descriptive statistical analysis, the findings were classified over a range of values and described accordingly. For each variable, an independent t-test was performed to compare the cases with the controls. A multivariable logistic regression analysis was used to choose the appropriate potential factors to determine the association in the multivariable analysis.

RESULTS

A total of 185 cases and 185 controls were included. The mean age of the cases with ischemic stroke was 63.77 ± 10.312, and that of the controls was 53.18 ± 11.35 (p < 0.01). The mean HbA1c level in the patients of acute ischemic stroke was 6.97 ± 1.84, and that of the controls was 5.99 ± 1.69 (p < 0.01). The mean random blood sugar (RBS) value in the ischemic stroke cases was 170.21 ± 84.16, and that of the controls was 150.03 ± 82.25 (p = 0.02). To compare the factors that were determined to be statistically significant between ischemic stroke cases and controls, a multivariable logistic regression analysis was performed. The HbA1c p-value was 0.01, the odds ratio (OR) was 1.280, and the 95% CI was 1.11-1.48. The other variables apart from HbA1c that were statistically significant between the ischemic stroke cases and the controls were age (p < 0.01, OR: 1.280, 95% CI: 1.06-1.11), hypertension (p = 0.618, OR: 1.130, 95% CI: 0.70-1.83), and high-density lipoprotein (p = 0.055, OR: 0.975, 95% CI: 0.95-1.00). When other cofounders were considered, it was concluded that with a 1% increase in HbA1c, the risk of stroke increases by 28% (OR: 1.28, 95% CI: 1.11-1.48). To compare the variables that were determined to be statistically significant between the control and ischemic stroke case groups, a multivariable logistic regression was used. The area under the receiver operating characteristic curve for HbA1c was 0.773 and RBS was 0.600.

CONCLUSION

This study shows that higher HbA1c levels in patients increase the risk of ischemic stroke. This study brings to light the need to screen the population periodically for diabetes by routinely testing for Hba1c in those who are at high risk of diabetes. Stroke risk can be reduced with early management and intervention. This study also concludes that HbA1c is a better predictor for assessing the risk of ischemic stroke than RBS levels.

Associations Between HbA1c Across the Normal Range, Diagnosed, and Undiagnosed Diabetes and Retinal Layer Thickness in UK Biobank Cohort

Purpose

The purpose of this study was to investigate the association between glycated hemoglobin (HbA1c) levels and retinal sub-layer thicknesses in people with and without diabetes.

Methods

We included 41,453 UK Biobank participants aged 40 to 69 years old. Diabetes status was defined by self-report of diagnosis or use of insulin. Participants were categorized into groups: (1) those with HbA1c <48 mmol/mol were subdivided into quintiles according to normal range of HbA1c; (2) those previously diagnosed with diabetes with no evidence of diabetic retinopathy; and (3) undiagnosed diabetes: >48 mmol/mol. Total macular and retinal sub-layer thicknesses were derived from spectral-domain optical coherence tomography (SD-OCT) images. Multivariable linear regression was used to evaluate the associations between diabetes status and retinal layer thickness.

Results

Compared with participants in the second quintile of the normal HbA1c range, those in the fifth quintile had a thinner photoreceptor layer thickness (-0.33 µm, P = 0.006). Participants with diagnosed diabetes had a thinner macular retinal nerve fiber layer (mRNFL; -0.58 µm, P < 0.001), photoreceptor layer thickness (-0.94 µm, P < 0.001), and total macular thickness (-1.61 µm, P < 0.001), whereas undiagnosed diabetes participants had a reduced photoreceptor layer thickness (-1.22 µm, P = 0.009) and total macular thickness (-2.26 µm, P = 0.005). Compared to participants without diabetes, those with diabetes had a thinner mRNFL (-0.50 µm, P < 0.001), photoreceptor layer thickness (-0.77 µm, P < 0.001), and total macular thickness (-1.36 µm, P < 0.001).

Conclusions

Participants with higher HbA1c in the normal range had marginally thinner photoreceptor thickness, whereas those with diabetes (including undiagnosed diabetes) had meaningfully thinner retinal sublayer and total macular thickness.

Translational Relevance

We showed that early retinal neurodegeneration occurs in people whose HbA1c levels are below the current diabetes diagnostic threshold; this might impact the management of pre-diabetes individuals.

Assessing the linear and non-linear association of HbA1c with cardiovascular disease: a Mendelian randomisation study

AIMS/HYPOTHESIS

We aimed to evaluate whether genetically predicted HbA_1c has an effect on the risk of cardiovascular diseases and investigate the shape of the relationship of genetically predicted HbA_1c with cardiovascular diseases.

METHODS

We performed linear univariable, multivariable and non-linear Mendelian randomisation analyses in 373,571 white British participants (mean age 56.9) from the UK Biobank.

RESULTS

In univariable linear Mendelian randomisation analysis, a 1 mmol/mol increase in genetically predicted HbA_1c was associated with higher risk of coronary artery disease (OR 1.03, 95% CI 1.02, 1.05), stroke (OR 1.02, 95% CI 1.00, 1.05) and hypertension (OR 1.02, 95% CI 1.01, 1.03). Multivariable Mendelian randomisation adjusted for the effect of haemoglobin gave a consistent conclusion for coronary artery disease. The associations with stroke and hypertension were directionally similar but with wider CI overlapping the null. Non-linear Mendelian randomisation indicated that the shape of the effect of genetically predicted HbA_1c on cardiovascular outcomes was likely linear.

CONCLUSIONS/INTERPRETATION

The study suggests a detrimental effect of HbA_1c on coronary artery disease in both men and women, and the effect is via a glycaemic characteristic. The shape of the genetic association of HbA_1c with these cardiovascular outcomes, in particular coronary artery disease, is likely to be linear.

Improvement of glycemic control in type 2 diabetes: A systematic review and meta-analysis of randomized controlled trials

AIM

Different guidelines provide similar, but not identical, therapeutic targets for HbA1c in type 2 diabetes. These targets can also depend from the different pharmacological strategies adopted for intensifying glycemic control.

DATA SYNTHESIS

This meta-analysis includes randomized trials adopting any pharmacological regimen for intensifying glycemic control in T2DM (versus standard of care/placebo), with a trial duration ≥2 years and a between-group HbA1c difference≥0.5%. The primary outcome was to assess the effects of the improvement of glycemic control on major cardiovascular events (MACE), ocular and renal complications, and severe hypoglycemia. Mantel-Haenszel odds ratios (MH-OR) with 95% Confidence Intervals were calculated for all the outcomes considered. We included 13 trials fulfilling the inclusion criteria. The improvement of glycemic control was associated with a lower risk of MACE (MH-OR:0.89 [95%CI 0.85-0.94]) and renal adverse events (MH-OR 0.73 [0.65-0.82]), but not all-cause mortality (MH-OR 0.95 [0.88-1.01]) and ocular adverse complications (MH-OR 0.94 [0.72-1.22]). For glucose-lowering drugs inducing hypoglycemia, a protective effect on the risk of microvascular complications, but not of MACE and all-cause mortality, was observed only for HbA1c ≤ 48 mmol/mol, but with higher risk of severe hypoglycaemia (MH-OR 2.72 [1.79-4.13]). Drugs not inducing hypoglycaemia were associated with a reduction of MACE, renal adverse events, and all-cause mortality, for HbA1c< 7% (no data for lower targets).

CONCLUSIONS

The present meta-analysis show that the improvement of glycemic control with drugs not inducing hypoglycemia is associated with a reduction in the risk of long-term chronic vascular and renal complications, and all-cause mortality.

Ranking of stroke and cardiovascular risk factors for an optimal risk calculator design: Logistic regression approach

PURPOSE

Conventional cardiovascular risk factors (CCVRFs) and carotid ultrasound image-based phenotypes (CUSIP) are independently associated with long-term risk of cardiovascular (CV) disease. In this study, 26 cardiovascular risk (CVR) factors which consisted of a combination of CCVRFs and CUSIP together were ranked. Further, an optimal risk calculator using AtheroEdge composite risk score (AECRS1.0) was designed and benchmarked against seven conventional CV risk (CVR) calculators.

METHODS

Two types of ranking were performed: (i) ranking of 26 CVR factors and (ii) ranking of eight types of 10-year risk calculators. In the first case, multivariate logistic regression was used to compute the odds ratio (OR) and in the second, receiver operating characteristic curves were used to evaluate the performance of eight types of CVR calculators using SPSS23.0 and MEDCALC12.0 with validation against STATA15.0.

RESULTS

The left and right common carotid arteries (CCA) of 202 Japanese patients were examined to obtain 404 ultrasound scans. CUSIP ranked in the top 50% of the 26 covariates. Intima-media thickness variability (IMTV) and IMTV_10yr were the most influential carotid phenotypes for left CCA (OR = 250, P < 0.0001 and OR = 207, P < 0.0001 respectively) and right CCA (OR = 1614, P < 0.0001 and OR = 626, P < 0.0001 respectively). However, for the mean CCA, AECRS1.0 and AECRS1.0_10yr reported the most highly significant OR among all the CVR factors (OR = 1.073, P < 0.0001 and OR = 1.104, P < 0.0001). AECRS1.0_10yr also reported highest area-under-the-curve (AUC = 0.904, P < 0.0001) compared to seven types of conventional calculators. Age and glycated haemoglobin reported highest OR (1.96, P < 0.0001 and 1.05, P = 0.012) among all other CCVRFs.

CONCLUSION

AECRS1.0_10yr demonstrated the best performance due to presence of CUSIP and ranked at the first place with highest AUC.

Relationship Between Glycated Haemoglobin and Carotid Atherosclerotic Disease Among Patients with Acute Ischaemic Stroke

Objectives

This study aimed to determine the relationship between glycaemic control and carotid atherosclerotic disease among patients with acute ischaemic stroke (AIS).

Methods

This retrospective cross-sectional study took place in the Neurology Department of King Fahad Hospital of University, Khobar, Saudi Arabia, from April to October 2017. Data were collected from the medical records of 244 patients with a diagnosis of AIS confirmed by computed tomography. Doppler ultrasounds of the carotid artery were performed to determine the presence of increased carotid intima media thickness (CIMT) and plaques.

Results

Significantly higher mean glycated haemoglobin (HbA1c) levels were noted in cases with high CIMT values (P = 0.002), but not in cases with carotid plaques (P = 0.360). In addition, there was a significant association between diabetes mellitus (DM) and high CIMT (P = 0.045), but not with carotid plaques (P = 0.075). Finally, while dyslipidaemia and age were independently correlated with high CIMT values (P = 0.034 and <0.001, respectively) and carotid plaques (P <0.001 each), no independent relationships were noted in terms of gender and other risk factors like DM, hypertension and smoking (P >0.050 each).

Conclusion

High HbA1c levels were associated with high CIMT values, but not with carotid plaques. Therefore, HbA1c levels may be useful as an indirect marker of the initial stages of carotid artery atherosclerosis.

Single-nucleotide polymorphisms of the adherent junction component cadherin gene are associated with leukoaraiosis

BACKGROUND

Leukoaraiosis (LA) is one of the manifestations of cerebral small vessel disease. Blood-brain barrier (BBB) disruption plays a key role in LA. Cadherin is a component of adherent junctions (AJ), which play a crucial role in cell-cell adhesion, cell-cell recognition and homeostasis in BBB development. We hypothesized that alterations in cadherin genes might be a potential cause of BBB abnormalities that result in LA.

METHODS

A total of 339 LA individuals (LA-PVWM, 183; LA-DWM 156) were enrolled, who underwent brain magnetic resonance imaging with obtainable vascular risk factors. Genotyping of cadherin single-nucleotide polymorphisms (SNPs) (rs5030625, rs1801026, and rs16260) was performed by real-time polymerase chain reaction with LightSNiP reagents (coupled primer and probe) and FastStart DNAMaster HybProbe (Roche Diagnostic, GmBH, Mannheim, Germany) on a LightCycler 2.0 instrument.

RESULTS

Two SNPs, rs1801026 and rs16260, were significantly different between the control and LA groups. The combinatorial effects of the three SNPs were also significant. The haplotypes G-T-C and GA-T-A increased the development of LA-PVWM (OR = 1.76 and OR = 40.7, respectively). The haplotypes G-T-A and GA-T-A increased the development of LA-DWM (OR = 2.56 and OR = 10.48, respectively), but G-C-C decreased the development of LA-DWM (OR = 17.57).

CONCLUSION

This study provides evidence for genetic polymorphisms of the AJ component cadherin gene and the association of its haplotypes with LA.

Protocol for a feasibility randomised controlled trial of Screening and Enhanced Risk management for Vascular Event-related Decline in Memory (SERVED Memory)

INTRODUCTION

Stroke is a leading cause of death and disability. The development of dementia after stroke is common. Vascular risk factors (VRF) which contribute to stroke risk can also contribute to cognitive decline, especially in vascular dementia (VaD). There is no established treatment for VaD, therefore strategies for prevention could have major health resource implications. This study was designed to assess whether patients with early cognitive decline after stroke/transient ischaemic attack (TIA) can be easily identified and whether target-driven VRF management can prevent progression to dementia.

OBJECTIVES

The primary objective is to establish the feasibility of recruitment and retention of patients with early cognitive decline to a randomised controlled trial of enhanced VRF management. Secondary objectives include: (a) to determine the potential clinical benefit of the intervention; (b) to estimate the sample size for a future definitive multicentre randomised controlled trial; (c) to inform a future economic evaluation; (d) to explore the link between VRF control and the incidence of cognitive impairment on longitudinal follow-up in a UK population after stroke/TIA with current routine management.

METHODS

100 patients with cognitive decline poststroke/TIA will be recruited from stroke services at the Norfolk and Norwich University Hospital. After collection of baseline data, they will be randomised to intervention (3 monthly follow-up with enhanced management) or control (treatment as usual by the general practitioner). At 12 months outcomes (repeat cognitive testing, VRF assessment) will be assessed. A further 100 patients without cognitive decline will be recruited to a parallel observational group from the same site. At 12 months they will have repeat cognitive testing.

ETHICS AND DISSEMINATION

Ethical approval has been granted in England. Dissemination is planned via publication in peer-reviewed medical journals and presentation at relevant conferences.

TRIAL REGISTRATION NUMBER

42688361; Pre-results.

High HbA1c is associated with higher risk of ischaemic stroke in Pakistani population without diabetes

CONTEXT

The role of glycated haemoglobin (HbA1c) in the prediction of ischaemic stroke in individuals without diabetes is underestimated.

AIMS

We performed a study to analyse the role of HbA1c in the risk prediction of ischaemic stroke in Pakistani population without diabetes. We further studied the difference between HbA1c values of individuals with diabetes and without diabetes with stroke.

SETTINGS AND DESIGN

Single centre, case-control.

MATERIALS AND METHODS

In phase I, a total of 233 patients without diabetes with ischaemic stroke and 245 as controls were enrolled. Association of HbA1c levels, lipid profiles and blood pressure recordings with ischaemic stroke was analysed. In phase II, comparison was done between diabetics and non-diabetics with stroke.

STATISTICAL ANALYSIS

Comparison of the mean variables was performed with Student's t-tests. Logistic regression analysis with ischaemic stroke as the dependent variable was performed for phase I.

RESULTS

In phase I, the ischaemic stroke group had significantly higher HbA1c levels (5.9±2.9% vs 5.5±1.6%) compared with controls (p<0.05). Triglyceride cholesterol, high-density lipoprotein cholesterol, systolic blood pressure, diastolic blood pressure and HbA1c were the significant determinants of stroke (p<0.05). In phase II, mean HbA1c values were significantly higher in the diabetes group (7.6±2.1 vs 6.1±2.3) (p<0.05) but other parameters were not statistically significantly different (p>0.05).

CONCLUSIONS

Higher HbA1c indicated a significantly increased risk for ischaemic stroke. An HbA1c value above 5.6% (prediabetic range) predicted future risk of stroke and efforts to maintain glucose level within the normal range (≤5.6%) in individuals with high cardiovascular risk are important.

Type 2 diabetes mellitus and the clinical course of acute stroke

We carried out a comparative analysis of the clinical course of acute stroke in patients with and without type 2 diabetes mellitus (T2DM). The prevalence of carotid atherosclerosis (incl. those with plaques and hemodynamically significant [≥60%] carotid stenosis) was higher in patients with T2DM. With relatively similar baseline brain damage and neurological deficits patients with T2DM had a higher rate of symptom worsening, which leads to poorer outcome. A less favourable post-stroke prognosis was found to be associated with the presence of T2DM, but not with transient changes in glycemic levels. Most patients with T2DM presented with acute stroke showing elevated levels of both plasma glucose and glycated haemoglobin, the latter indicating a long period of hyperglycemia preceding the acute cerebrovascular event.

Association between hemoglobin A1c and carotid atherosclerosis in rural community-dwelling elderly Japanese men

Background

Recent studies have reported an association between both higher and lower levels of hemoglobin A1c (HbA1c) and higher mortality of diabetes patients. Like diabetes, carotid atherosclerosis is a well known lifestyle-related disease. However, no studies have yet reported an association between HbA1c levels and carotid atherosclerosis.

Methods

We conducted a cross-sectional study of 1,150 Japanese elderly men aged ≥60 years who were undergoing general health checkups. Carotid atherosclerosis was defined as a carotid intima-media thickness (CIMT) ≥1.1 mm. Since body mass index (BMI) is regarded as a cardiovascular risk factor that exerts a strong influence on both HbA1c levels and carotid atherosclerosis, we performed a stratified analysis of this risk based on BMI.

Results

Using the intermediate HbA1c quintile as a reference group, the groups in the lowest HbA1c quintiles showed a significantly higher risk of carotid atherosclerosis in patients with low BMI (≤23 kg/m²) vs. no increased risk in those with high BMI (>23 kg/m²). The association of HbA1c with carotid atherosclerosis became slightly stronger when these analyses were limited to subjects who were not taking glucose-lowering medications or medications for hyperlipidemia and cardiovascular disease. After adjusting for classical cardiovascular risk factors, adjusted odds ratios (ORs) for carotid atherosclerosis were 1.36 (0.84 to 2.20) for total subjects, 2.29 (1.12 to 4.66) for low-BMI groups, and 0.68 (0.33 to 1.41) for high-BMI groups.

Conclusions

Lower HbA1c level is a significant risk factor for carotid atherosclerosis in rural community-dwelling elderly Japanese men with low, but not high BMI, particularly in those not taking glucose-lowering medication.

Multiple biomarker models for improved risk estimation of specific cardiovascular diseases related to metabolic syndrome: a cross-sectional study

Background

Metabolic syndrome (MetS) is the co-occurrence of several conditions that increase risk of chronic disease and mortality. Multivariate models for calculating risk of MetS-related diseases based on combinations of biomarkers are promising for future risk estimation if based on large population samples. Given biomarkers’ nonspecificity and commonality in predicting diseases, we hypothesized that unique combinations of the same clinical diagnostic criteria can be used in different multivariate models to develop more accurate individual and cumulative risk estimates for specific MetS-related diseases.

Methods

We utilized adult biomarker and cardiovascular disease (CVD) data from the National Health and Nutrition Examination Survey as part of a cross-sectional analysis. Serum C-reactive protein (CRP), glycohemoglobin, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, fasting glucose, and apolipoprotein-B were modeled. CVDs included congestive heart failure, coronary heart disease, angina, myocardial infarction, and stroke. Decile analysis for disease prevalence in each biomarker group and multivariate logistic regression for estimation of odds ratios were employed to measure the joint association between multiple biomarkers and CVD diagnoses.

Results

Of the biomarkers considered, glycohemoglobin, triglycerides, and CRP were consistently associated with the CVD outcomes of interest in decile analysis and were selected for the final models. Associations were overestimated when using single-marker models in comparison with full models; individual odds ratios decreased an average of 16.4% from the single-biomarker models to the joint association models for CRP, 6.6% for triglycerides, and 1.4% for glycohemoglobin. However, joint associations were stronger than any single-marker estimate. Additionally, reduced models produced unique combinations of biomarkers for specific CVD outcomes.

Conclusion

The reduced joint association modeling results suggest that unique combinations of biomarkers with their related measure of association can be used to produce more accurate cumulative risk estimates for each CVD. Additionally, our results indicate that the use of multiple biomarkers in a single multivariate model may provide increased accuracy of individual biomarker association estimates by controlling for statistical artifacts and spurious relationships due to co-biomarker confounding.

Electronic supplementary material

The online version of this article (doi:10.1186/s12963-015-0041-5) contains supplementary material, which is available to authorized users.

Association of rs2075575 and rs9951307 polymorphisms of AQP-4 gene with leukoaraiosis

BACKGROUND

Leukoaraiosis (LA) is associated with structural and functional vascular changes that correlate with motor and gait disturbances, depressive symptoms, urinary disturbances, and dementia. The blood-brain barrier (BBB) plays a key role in development of lacunar stroke, leukoaraiosis, and other feature of cerebral small-vessel disease, and there are numerous studies examining changes in the BBB with normal aging and in dementia and LA. Aquaporin-4 (AQP-4), the primary water channel protein in the central nervous system, is involved in BBB development, function, and integrity, and its dysfunction induces several neurologic diseases. The aim of our study was to evaluate whether genetic variations in AQP-4 gene are associated with the development of LA.

METHODS

DNA was amplified and the single-nucleotide polymorphisms in AQP-4 gene were investigated by melting curve analysis using real-time polymerase chain reaction.

RESULTS

The frequency of both T allele and CT/TT genotypes of rs2075575 was significantly higher in LA group than in control group (C versus T, P = .0145; CC versus CT/TT, P = .038). However, no significant difference was observed between LA group and control group in rs9951307. Interestingly, the rs9951307 AG + GG genotype may confer a synergistic effect in odds ratio (OR) values when combined with the rs2075575 CT + TT genotypes (OR = 1.65 → 2.51). The C-A haplotype was significantly different between LA group and the control group (P = .005). By stratified analysis, rs2075575 and rs9951307 polymorphisms were statistically significant in the subjects with hypertension and hemoglobin A1c (P < .05), whereas the rs2075575 polymorphism was associated with high serum cholesterol (P < .05) and the rs9951307 polymorphism was associated with low serum homocysteine (P < .05).

CONCLUSIONS

Our results indicate that AQP-4 genetic variations and haplotypes might contribute to the risk factors for LA.

Haemoglobin A1c even within non-diabetic level is a predictor of cardiovascular disease in a general Japanese population: the Hisayama Study

Background

There is little information about predictive ability of haemoglobin A1c (HbA1c) for cardiovascular disease (CVD) in Asians. To investigate the discriminatory ability of HbA1c to identify subjects who are at greater risk of developing CVD in a prospective study of a defined community-dwelling Japanese population.

Methods

A total of 2,851 subjects aged 40–79 years were stratified into five groups (HbA1c levels with ≤ 5.0, 5.1–5.4, 5.5–6.4, and ≥ 6.5% and a group with antidiabetic medication) and followed up prospectively for 7 years (2002–2009).

Results

During the follow-up, 119 subjects developed CVD. The multivariable-adjusted risk of CVD was significantly increased in subjects with HbA1c levels of 5.5–6.4 and ≥ 6.5% and diabetic medication compared to HbA1c level with ≤ 5.0% (hazard ratio, 2.26 [95% confidence interval, 1.29–3.95] for the 5.5–6.4%; 4.43 [2.09–9.37] for the ≥ 6.5%; and 5.15 [2.65–10.0] for the antidiabetic medication group). With regard to CVD subtype, the positive associations between HbA1c levels and the risk of coronary heart disease (CHD) and ischaemic stroke were also significant, but no such associations were seen for haemorrhagic stroke. The C statistic for developing CVD was significantly increased by adding HbA1c values to the model including other risk factors (0.789 vs. 0762, p = 0.006), and the net reclassification improvement was 0.105 (p = 0.004).

Conclusions

Our findings suggest that elevated HbA1c levels are an independent risk factor for CVD, especially CHD and ischaemic stroke, and that the addition of HbA1c to the model with traditional risk factors significantly improves the predictive ability of CVD.

HbA1c and the risks for all-cause and cardiovascular mortality in the general Japanese population: NIPPON DATA90

OBJECTIVE

Associations between HbA1c and cardiovascular diseases (CVD) have been reported mainly in Western countries. It is not clear whether HbA1c measurements are useful for assessing CVD mortality risk in East Asian populations.

RESEARCH DESIGN AND METHODS

The risk for cardiovascular death was evaluated in a large cohort of participants selected randomly from the overall Japanese population. A total of 7,120 participants (2,962 men and 4,158 women; mean age 52.3 years) free of previous CVD were followed for 15 years. Adjusted hazard ratios (HRs) and 95% CIs among categories of HbA1c (<5.0%, 5.0-5.4%, 5.5-5.9%, 6.0-6.4%, and ≥6.5%) for participants without treatment for diabetes and HRs for participants with diabetes were calculated using a Cox proportional hazards model.

RESULTS

During the study, there were 1,104 deaths, including 304 from CVD, 61 from coronary heart disease, and 127 from stroke (78 from cerebral infarction, 25 from cerebral hemorrhage, and 24 from unclassified stroke). Relations to HbA1c with all-cause mortality and CVD death were graded and continuous, and multivariate-adjusted HRs for CVD death in participants with HbA1c 6.0-6.4% and ≥6.5% were 2.18 (95% CI 1.22-3.87) and 2.75 (1.43-5.28), respectively, compared with participants with HbA1c <5.0%. Similar associations were observed between HbA1c and death from coronary heart disease and death from cerebral infarction.

CONCLUSIONS

High HbA1c levels were associated with increased risk for all-cause mortality and death from CVD, coronary heart disease, and cerebral infarction in general East Asian populations, as in Western populations.

Role of oxidative stress in physiological albumin glycation: a neglected interaction

Protein glycation is a key mechanism involved in chronic disease development in both diabetic and nondiabetic individuals. About 12-18% of circulating proteins are glycated in vivo in normoglycemic blood, but in vitro studies have hitherto failed to demonstrate glucose-driven glycation below a concentration of 30mM. Bovine serum albumin (BSA), reduced BSA (mercaptalbumin) (both 40g/L), and human plasma were incubated with glucose concentrations of 0-30mM for 4 weeks at 37°C. All were tested preoxidized for 8h before glycation with 10nM H2O2 or continuously exposed to 10nM H2O2 throughout the incubation period. Fructosamine was measured (nitroblue tetrazolium method) at 2 and 4 weeks. Oxidized BSA (both preoxidized and continuously exposed to H2O2) was more readily glycated than native BSA at all glucose concentrations (p = 0.03). Moreover, only oxidized BSA was glycated at physiological glucose concentration (5mM) compared to glucose-free control (glycation increased by 35% compared to native albumin, p < 0.05). Both 5 and 10mM glucose led to higher glycation when mercaptalbumin was oxidized than when unoxidized (p < 0.05). Fructosamine concentration in human plasma was also significantly higher when oxidized and exposed to 5mM glucose, compared to unoxidized plasma (p = 0.03). The interaction between glucose concentration and oxidation was significant in all protein models (p < 0.05). This study has for the first time demonstrated albumin glycation in vitro, using physiological concentrations of albumin, glucose, and hydrogen peroxide, identifying low-grade oxidative stress as a key element early in the glycation process.

Glucose control and cardiovascular outcomes in individuals with diabetes mellitus: lessons learned from the megatrials

Glucose lowering should be approached by managing overall cardiovascular risk. Glycemic goals should be individualized based on duration of diabetes, preexisting cardiovascular disease, age, and life expectancy. Intensive glycemic control has consistently been shown to produce a substantial benefit for preventing long-term microvascular complications in both type 1 and type 2 diabetes mellitus. Although cardiovascular disease is the major cause of death in patients with diabetes, microvascular complications cause substantial morbidity and disability. Thus, it is apparent that additional strategies on multimodal treatment options are necessary to promote effective management and prevention of diabetic complications.

Glycated hemoglobin A₁c (HbA₁c) and diabetes: a new era?

Abstract In January 2011 the American Diabetes Association (ADA) published the latest guidelines for the diagnosis and treatment of diabetes mellitus (DM)(1,2). Despite some controversies, glycated hemoglobin A(1c) (HbA(1c)), an established marker of long-term glycemia traditionally used to assess the quality of DM management, remained an independent criterion for the diagnosis of DM, and indeed now appears to be well established in the USA. This has far-reaching implications for clinical practice worldwide.

Repeated administration of exendin-4 reduces focal cerebral ischemia-induced infarction in rats

Exendin-4 is a GLP-1 agonist that is clinically used for the treatment of diabetes mellitus and may also have neuroprotective effect. We explored the effect of repeated administration of exendin-4 (0.5 μg/kg, intraperitoneal twice a day for 7 days) on infarct volume, neurological deficit (neurological score, grip test, foot fault and rota rod tests), oxidative stress parameters (malondialdehyde, reduced glutathione, and superoxide dismutase) and expression of endothelin (ET) ET(A) and ET(B) receptors following cerebral ischemia produced in rats by permanent middle cerebral artery occlusion (MCAO). Since ET(A) receptors in the central nervous system (CNS) are involved in cerebral ischemia, we determined the effect of a specific ET(A) receptor antagonist, BQ123 (1mg/kg, intravenously administered thrice: 30 min, 2h and 4h after MCAO for a total dose of 3 mg/kg) on cerebral ischemia in control and exendin-4 treated rats. Results indicate that exendin-4 treated rats had significant protection following MCAO induced cerebral ischemia. The infarct volume was 27% less compared to vehicle treated rats. The neurological deficit following MCAO was lower and oxidative stress parameters were improved in exendin-4 treated rats compared to control. BQ123 significantly improved infarct volume, oxidative stress parameters and neurological deficit in ischemic rats treated with vehicle or exendin-4. BQ123 induced protection from cerebral ischemia was similar in vehicle or exendin-4 treated rats. Expression of ET(A) receptors was significantly increased following cerebral ischemia which was not affected by exendin-4 treatment or by BQ123 administration. No change in expression of ET(B) receptors was observed following cerebral ischemia or any treatment. It is concluded that exendin-4 protects the CNS from damage due to cerebral ischemia by reducing oxidative stress and is independent of ET receptor involvement.

Ongoing clinical trials evaluating the cardiovascular safety and efficacy of therapeutic approaches to diabetes mellitus

Research has substantiated that patients with type 2 diabetes mellitus are at increased risk for cardiovascular (CV) disease. It is well established that aggressive management of metabolic risk factors is critical to reducing morbidity and mortality in patients with diabetes. A number of clinical trials are currently focusing on evaluating the safety and efficacy of therapeutic approaches to diabetes. These trials will provide additional information on the role of aggressive management of glucose in patients with diabetes and CV risk. This article provides a summary of these ongoing trials, and discusses the impact of glycemic control and strategies to promote CV risk reduction in patients with diabetes.

Haemoglobin A1c levels and subsequent cardiovascular disease in persons without diabetes: a meta-analysis of prospective cohorts

AIMS/HYPOTHESIS

The aim of this meta-analysis was to determine the relationship between HbA(1c) levels and subsequent cardiovascular outcomes in individuals without diabetes.

METHODS

We searched Medline, Embase and Scopus from initiation of the study until the end of 2009. One reviewer searched and another verified findings. Data were extracted by one reviewer and verified by another. We accepted prospective studies in any language reporting three or more quartiles for HbA(1c) levels. Within quartiles, authors must have presented both numbers of patient-years at risk and cardiovascular outcomes. Outcomes per person-time at risk were regressed on average HbA(1c) values using Poisson regression. We pooled β coefficients using Cochran's semi-weighted (inverse variance) random-effects model. Study quality was assessed using the Downs-Black scale.

RESULTS

We investigated 16 datasets (nine for total cardiovascular events and seven for death) from five papers with 44,158 patients (44% men) over 404,899 patient-years of follow-up. There were 1,366 cardiovascular deaths (3.1%; 3.37/1,000 person-years) and 2,142 cardiovascular events (4.9%; 5.29/1,000 person-years). The overall meta-analytic β coefficients were 0.720 (95% CI 0.307-1.133) and 0.757 (95% CI 0.382-1.132) for cardiac death and events, respectively. Compared with the baseline value of 0.0427, an HbA(1c) level of 0.05 was associated with a relative risk for cardiovascular death of 1.13 (95% CI 1.05-1.21), a 0.06 value with 1.34 (95% CI 1.13-1.58), and a 0.07 HbA(1c) with relative risk 1.58 (95% CI 1.22-2.06). Results for total cardiovascular events were similar. The average study quality was 0.7 (70%).

CONCLUSIONS/INTERPRETATION

We conclude that HbA(1c) was significantly associated with cardiovascular events and deaths in persons without diabetes.

Cortical neurons develop insulin resistance and blunted Akt signaling: a potential mechanism contributing to enhanced ischemic injury in diabetes

Patients with diabetes are at higher risk of stroke and experience increased morbidity and mortality after stroke. We hypothesized that cortical neurons develop insulin resistance, which decreases neuroprotection via circulating insulin and insulin-like growth factor-I (IGF-I). Acute insulin treatment of primary embryonic cortical neurons activated insulin signaling including phosphorylation of the insulin receptor, extracellular signal-regulated kinase (ERK), Akt, p70S6K, and glycogen synthase kinase-3β (GSK-3β). To mimic insulin resistance, cortical neurons were chronically treated with 25 mM glucose, 0.2 mM palmitic acid (PA), or 20 nM insulin before acute exposure to 20 nM insulin. Cortical neurons pretreated with insulin, but not glucose or PA, exhibited blunted phosphorylation of Akt, p70S6K, and GSK-3β with no change detected in ERK. Inhibition of the phosphatidylinositol 3-kinase (PI3-K) pathway during insulin pretreatment restored acute insulin-mediated Akt phosphorylation. Cortical neurons in adult BKS-db/db mice exhibited higher basal Akt phosphorylation than BKS-db(+) mice and did not respond to insulin. Our results indicate that prolonged hyperinsulinemia leads to insulin resistance in cortical neurons. Decreased sensitivity to neuroprotective ligands may explain the increased neuronal damage reported in both experimental models of diabetes and diabetic patients after ischemia-reperfusion injury.

Diabetes mellitus and Alzheimer's disease: shared pathology and treatment?

Epidemiological and basic science evidence suggest a possible shared pathophysiology between type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD). It has even been hypothesized that AD might be 'type 3 diabetes'. The present review summarizes some of the evidence for the possible link, putative biochemical pathways and ongoing clinical trials of antidiabetic drugs in AD patients. The primary and review literature were searched for articles published in peer-reviewed sources that were related to a putative connection between T2DM and AD. In addition, public sources of clinical trials were searched for the relevant information regarding the testing of antidiabetic drugs in AD patients. The evidence for a connection between T2DM and AD is based upon a variety of diverse studies, but definitive biochemical mechanisms remain unknown. Additional study is needed to prove the existence or the extent of a link between T2DM and AD, but sufficient evidence exists to warrant further study. Presently, AD patients might benefit from treatment with pharmacotherapy currently used to treat T2DM and clinical trials of such therapy are currently underway.

New diagnosis criteria for diabetes with hemoglobin A1c and risks of macro-vascular complications in an urban Japanese cohort: the Suita study

The association of the new diagnosis criteria for diabetes adopting hemoglobin A1c, recently proposed by the international expert committee, with macro-vascular complications was tested in a 12-year population-based cohort. The present analysis suggested that this new criteria were applicable to macro-vascular complications in the Japanese.

Clinical usefulness of glycosylated hemoglobin as a predictor of adenomatous polyps in the colorectum of middle-aged males

OBJECTIVE

We investigated the clinical usefulness of HbA1c in screening an average-risk group <50 years of age who need colonoscopy for colorectal cancer (CRC) screening.

METHODS

Eight hundred nineteen asymptomatic males who underwent colonoscopy for CRC screening with blood chemistries between January 2006 and December 2006 were enrolled. The ages of the subjects ranged from 40 to 59.

RESULTS

Subjects in their 50 s had significantly more adenomatous polyps than subjects in their 40 s (32.7% vs. 26.0%, p < 0.05). The incidence of adenomatous polyp increased with increasing quartiles of HbA1C as follows: first quartile (19.9%, HbA1c 4.0-5.0), second quartile (27.8%, HbA1c 5.1-5.3), third quartile (32.7%, HbA1c 5.4-5.5), and fourth quartile (34.9%, HbA1c = 5.6-8.8)(p = 0.008). When combining quartile of HbA1c and age (40 s vs. 50 s) according to HbA1C levels, the odds ratio for adenomatous polyp in subjects in their 40 s with HbA1c <5.4% was significantly lower than that in subjects in their 50 s. However, the odds ratio for adenomatous polyp in subjects in their 40 s with HbA1c > or =5.4% was similar to that in subjects in their 50 s with average risk for CRC.

CONCLUSIONS

An elevated HbA1c may be useful as a clinical predictor of adenomatous polyps in male subjects <50 years of age who have average risk for CRC.

Effects of beta-blockers on glucose and lipid metabolism

BACKGROUND

Activation of the sympathetic nervous system (SNS) has been linked to hypertension. Beta-blockers, which decrease SNS activation via beta-adrenergic receptor antagonism, are effective in lowering blood pressure and reducing cardiovascular morbidity and mortality in several conditions, including post-myocardial infarction and heart failure. Despite these clinical benefits, many physicians are reluctant to prescribe beta-blockers because of perceived negative metabolic effects, including reduced glycemic control, masking of hypoglycemia, insulin resistance, and dyslipidemia.

OBJECTIVE

This article reviews the pathophysiology of hypertension and either insulin resistance or dyslipidemia as well as treatment effects from glucose- and lipid-lowering regimens on cardiovascular morbidity and mortality. Based on a PubMed literature search from January 1980 to December 2008, the effects of nonvasodilating (atenolol, metoprolol, and propranolol) and vasodilating beta-blockers (carvedilol, labetalol, and nebivolol) on parameters of glucose and lipid metabolism in hypertension are presented. Preference for clinical trial inclusion was given to randomized, controlled trials with at least 100 patients. Limitations of a drug class literature review may include trial inclusion bias with associated result skewing and underrepresentation of an individual agent, which may give different results.

RESULTS

Beta-blockers differ in terms of their mechanism of action and their effects on glucose and lipid metabolism. Nonvasodilating beta-blockers reduce blood pressure in association with a cardiac output reduction and may increase or have no appreciable effect on peripheral vascular resistance. As a result, nonvasodilating beta-blockers are associated with a worsening of glycemic and lipidic control. In contrast, vasodilating beta-blockers reduce peripheral vascular resistance but have little or no effect on cardiac output. Numerous studies have established that vasodilating beta-blockers are associated with more favorable effects on glucose and lipid profiles than nonvasodilating beta-blockers.

CONCLUSIONS

Improvements in glucose and lipid metabolism mediated by vasodilating beta-blockers may help reduce coronary artery disease risk among high-risk patients with hypertension.

Does glycated hemoglobin have clinical significance in ischemic stroke patients?

OBJECTIVES

It has been suggested that patients with an elevated hemoglobin A1c (HbA1c) level have an increased risk of cardiovascular disease regardless of the presence of diabetes. However, an association between HbA1c and stroke has not yet been determined. In this study, our purpose was to examine whether HbA1c was independently associated with various types of cerebral vascular lesions in stroke patients.

METHODS

A consecutive series of acute ischemic stroke patients were included for this analysis from October, 2002, to March, 2006. HbA1c was examined on admission, and MR imaging was performed for analysis of large artery diseases (LADs) and small artery diseases (SADs). Symptomatic or asymptomatic LAD was diagnosed by MR angiography, and SAD was classified as leukoaraiosis, microbleeds, or old lacunar infarctions.

RESULTS

A total of 639 stroke patients were analyzed (diabetics, n=247; non-diabetics, n=392). There was no relationship between the level of HbA1c and any type of cerebrovascular lesion in the non-diabetic patients. In contrast, HbA1c showed a significant negative association with symptomatic LAD and leukoaraiosis in the diabetic patients using univariate analysis (p=0.01 and p<0.05, respectively). These associations did not remain significant, however, after adjustment for age and hypertension. This was, in part, because the HbA1c level in our diabetic population decreased gradually with age (p=0.03).

CONCLUSIONS

Our results indicate that HbA1c is not associated with risk for various types of cerebrovascular lesions in ischemic stroke patients. The negative association between age and HbA1c in diabetic patients should be further investigated.

Optimum control of blood glucose for prevention and treatment of ischemic and hemorrhagic stroke

Stroke is the most common cause of disability and a major cause of mortality. Each year, more than 500,000 Americans sustain a stroke. Reperfusion and antithrombotic therapies are still of limited benefit, hence increasing interest has been focused on therapeutic approaches that prevent and/or modulate infarct evolution. Hyperglycemia in acute stroke has a poor prognosis and is associated with significant morbidity and mortality. However, it remains unclear whether intensive lowering of blood glucose levels in the hyperacute and acute phases of stroke improves clinical outcomes. Experimental data suggest that elevated blood glucose may contribute to infarct expansion directly through a number of maladaptive metabolic pathways and that treatment with insulin may attenuate these adverse effects. Despite some controversy surrounding the optimal level of blood glucose control, much of the evidence to date supports rigorous blood glucose control and comprehensive cardiovascular risk factor management to prevent stroke in patients with diabetes. The current recommendation is to aim for strict control of blood pressure, glucose, and lipids along with lifestyle modification to improve cardiovascular health. However, there remains a distinct paucity of information concerning secondary stroke prevention. To date, the overwhelming evidence suggests that aggressive glucose management should be the standard of care in all patients with stroke and hyperglycemia. This article presents an overview of the recommendations for the optimum control of blood glucose for prevention and treatment of ischemic and hemorrhagic stroke.

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

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

Accuracy of death certification and hospital record linkage for identification of incident stroke

BACKGROUND

There is little information on the validity of using record linkage with routinely collected data for case ascertainment of stroke in large population-based studies in the UK. We examined the accuracy of these routine record linkage approaches for identifying incident stroke cases in a large UK population-based study, the European Prospective Investigation into Cancer (EPIC)-Norfolk cohort.

METHODS

We examined a sample of hospital records of incident stroke cases identified by linkage with two routine data sources, death certificates and a national hospital record linkage system (ENCORE), using predefined study criteria. Two senior Specialist Registrars with clinical experience in stroke medicine examined the hospital records and searched for the evidence of stroke recorded in these records between 1993/97-2003.

RESULTS

Of 520 incident strokes identified between 1993/1997-2003 using record linkage systems in the EPIC-Norfolk, a sample of 250 medical case notes were examined between March and July 2004. Using the predefined study criteria, there were 191 definite strokes (76%), 20 probable strokes (8%), 11 possible strokes and 11 cases of transient ischaemic attacks (4% each) i.e. 233/250 (93%) with possible or definite stroke or transient ischaemic attacks. Stroke could not be verified using hospital records in 13 cases (5%) and 4 cases (2%) had other diagnoses: 3 cases of vascular dementia and 1 case of benign intracranial hypertension. The diagnosis of stroke in 185 out of 250 cases identified in the EPIC-Norfolk (74.0%) was supported by radiological evidence using WHO criteria.

CONCLUSION

Death certificates and hospital record linkage in this British prospective study have a high accuracy or positive predictive value in correctly identifying incident stroke cases.

Post-challenge blood glucose concentration and stroke mortality rates in non-diabetic men in London: 38-year follow-up of the original Whitehall prospective cohort study

AIMS/HYPOTHESIS

While individuals with diabetes have a raised risk of stroke, it is unclear whether hyperglycaemia in non-diabetic populations is related to the development of this disease.

METHODS

In this prospective cohort study of 19,019 men, capillary blood was drawn 2 h after consumption of a glucose preparation equivalent to 50 g of anhydrous dextrose. Study participants were then followed for mortality for a maximum of 38 years.

RESULTS

During follow-up of 18,406 non-diabetic men, 13,116 deaths occurred (1,189 by stroke). Plots of stroke mortality rates versus blood glucose identified an upward inflection in risk of death from stroke at about 4.6 mmol/l. This upward inflection in risk could be adequately described using a single linear term above this threshold. A 1 mmol/l increase in blood glucose after this point was associated with a 27% increase in risk of death from stroke (hazard ratio 1.27, 95% CI 1.14-1.42). This increase in risk was partially attenuated by adjustment for covariates (1.17, 1.04-1.31) but remained statistically significant at conventional levels. Similar observations were made when all-cause mortality was the outcome of interest, although the magnitude of the association with blood glucose was somewhat lower.

CONCLUSIONS/INTERPRETATION

An incremental elevation in stroke mortality rates occurs with increasing post-challenge blood glucose.

Insulin, glucose and glycated hemoglobin in Alzheimer’s and vascular dementia with and without superimposed Type II diabetes mellitus condition

Increased concentrations of insulin, glucose and glycohemoglobin are associated with Type II diabetes mellitus (DM) and recognized as characteristic markers of the disease; in Alzheimer's (AD), Vascular dementia (VaD), and both dementia's with superimposed diabetes (AD + DM, VaD + DM) the knowledge is scarce. The sample (n = 122; males = 60; mean age = 73 +/- 7) comprised DM, AD, VaD, AD + DM, and VaD + DM patients, and healthy controls (C). The ANOVA's yielded significant differences between groups: Insulin p = 3.7 x 10(-3); Glucose p < 10(-12); Glycohemoglobin p = 9.2x10(-4). Comparisons between groups (DM vs. C, AD + DM vs. AD, VaD + DM vs. VaD, and demented DM vs. non-demented DM) resulted significant for all variables (Bonferroni's statistic, alpha = 0.05). Diabetic and diabetic demented patients presented significant increases largely different from controls (0.01 < p < 0.001), unlike the non-significant changes in their non-diabetic counterparts; linear relationships were found across all groups. The correlation's insulin/glucose and insulin/glycohemoglobin change to positive within demented groups, indicating a different performance of insulin in demented and non-demented subjects.