Effects of intensive glucose lowering on brain structure and function in people with type 2 diabetes (ACCORD MIND): a randomised open-label substudy

Postmenopausal hormone therapy, type 2 diabetes mellitus, and brain volumes

OBJECTIVE

To examine whether the effect of postmenopausal hormone therapy (HT) on brain volumes in women aged 65-79 years differs depending on type 2 diabetes status during postintervention follow-up of a randomized controlled clinical trial.

METHODS

The Women's Health Initiative randomized clinical trials assigned women to HT (0.625 mg/day conjugated equine estrogens with or without 2.5 mg/day medroxyprogesterone acetate) or placebo for an average of 5.6 years. A total of 1,402 trial participants underwent brain MRI 2.4 years after the trials; these were repeated in 699 women 4.7 years later. General linear models were used to assess the interaction between diabetes status and HT assignment on brain volumes.

RESULTS

Women with diabetes at baseline or during follow-up who had been assigned to HT compared to placebo had mean decrement in total brain volume of -18.6 mL (95% confidence interval [CI] -29.6, -7.6). For women without diabetes, this mean decrement was -0.4 (95% CI -3.8, 3.0) (interaction p=0.002). This interaction was evident for total gray matter (p<0.001) and hippocampal (p=0.006) volumes. It was not evident for changes in brain volumes over follow-up or for ischemic lesion volumes and was not influenced by diabetes duration or oral medications.

CONCLUSIONS

For women aged 65 years or older who are at increased risk for brain atrophy due to type 2 diabetes, prescription of postmenopausal HT is associated with lower gray matter (total and hippocampal) volumes. Interactions with diabetes and insulin resistance may explain divergent findings on how estrogen influences brain volume among older women.

Impact of diabetes on cognitive function and brain structure

Both type 1 and type 2 diabetes have been associated with reduced performance on multiple domains of cognitive function and with structural abnormalities in the brain. With an aging population and a growing epidemic of diabetes, central nervous system-related complications of diabetes are expected to rise and could have challenging future public health implications. In this review, we will discuss the brain structural and functional changes that have been associated with type 1 and type 2 diabetes. Diabetes duration and glycemic control may play important roles in the development of cognitive impairment in diabetes, but the exact underlying pathophysiological mechanisms causing these changes in cognition and structure are not well understood. Future research is needed to better understand the natural history and the underlying mechanisms, as well as to identify risk factors that predict who is at greatest risk of developing cognitive impairment. This information will lead to the development of new strategies to minimize the impact of diabetes on cognitive function.

Association between Visit-to-Visit Glucose Variability and Cognitive Function in Aged Type 2 Diabetic Patients: A Cross-Sectional Study

Background and Purpose

Diabetes is associated with cognitive decline as well as the development of dementia. Although mean blood glucose levels are typically used to assess the status of diabetic patients, glucose variability is also involved in the manifestation of macro- and microvascular complications in this population. Thus, the present study sought to determine whether visit-to-visit glucose variability contributes to cognitive decline in patients with type 2 diabetes.

Methods

The present study assessed 68 patients with type 2 diabetes using several validated neuropsychological measures. All patients had no cerebrovascular disease, history of hypoglycemia, psychiatric conditions, or other medical illnesses. Standard deviations (SDs) and coefficients of variance (CVs) of the patients’ blood glucose (after fasting and 2 hours postprandial; FBS and PP2), and glycated hemoglobin (HbA1c) values were used as indices of glucose variability. The cognitive outcome parameters were transformed with z-scores and entered into a multiple linear regression model that included educational status, age, sex, vascular risk factors, and mean glucose parameters as covariates.

Results

The mean age of the total patient population was 70.9 years; 46 (67.6%) of the patients were men, and the median follow-up duration at our endocrinology outpatient clinic was 4.8 years. The mean FBS and PP2 glucose levels of the patients were 132 mg/dL and 199 mg/dL, respectively, and the mean HbA1c level was 8.0%. A univariable analysis revealed that only the PP2 value was associated with the Mini-Mental State Examination (MMSE) score, and multivariable analysis revealed that a high SD and/or CV for PP2 glucose were associated with low scores on the Rey Complex Figure Copy test and/or the Verbal Learning Test. Additionally, a high SD and a higher CV for HbA1c level were significantly associated with low MMSE and Digit Span test scores even after adjusting for mean HbA1c values.

Conclusions

The present data indicate that a greater degree of visit-to-visit glucose variability influenced specific types of cognitive function in type 2 diabetic patients independently of mean blood glucose levels. Future studies should focus on whether reductions in glycemic variability will improve the cognitive decline observed in type 2 diabetic patients.

Cardiovascular risk factors and cognitive decline in older people with type 2 diabetes

AIMS/HYPOTHESIS

The aim of this work was to assess the role of well-established cardiovascular risk factors in the late-life cognitive decline of patients with type 2 diabetes.

METHODS

Data from 831 participants (aged 60-75 years) attending the 4 year follow-up of the Edinburgh Type 2 Diabetes Study (ET2DS) were used. Smoking history (pack-years), BP, HbA1c, plasma glucose and cholesterol were determined at baseline clinics (single time measurements) and/or from serial data recorded on a clinical management database from diagnosis until recruitment ('historical' data). Principal component analysis derived a factor, g, of general ability from seven cognitive tests. Linear regression models of follow-up g were adjusted for baseline g to represent 4 year cognitive change. 'Accelerated late-life cognitive decline' was defined as scoring in the lowest tertile of '4 year cognitive change' regression scores. Analyses controlled for age and sex.

RESULTS

A baseline history of moderate/heavy smoking (≥ 10 pack-years) and a 1% increased historical HbA1c (equivalent to an increase by 11 mmol/mol) predicted a 64% (OR 1.64; 95% CI 1.14, 2.34; p = 0.007) and 21% (OR 1.21; 95% CI 1.00, 1.45; p = 0.046) increased risk of accelerated cognitive decline, respectively. When treated as continuous measures, higher pack-years, historical HbA1c and historical BP emerged as significant independent predictors of 4 year decline in g (standardised β range -0.07 to -0.14; all p ≤ 0.05).

CONCLUSIONS/INTERPRETATION

Increased smoking and poorer glycaemic control (with relatively weaker findings for BP) during the life-course were independently associated with accelerated late-life cognitive decline. Where possible, evaluation is warranted of these risk factors as targets for intervention to reduce the burden of cognitive impairment in diabetes.

Cognitive Function and Control of Type 2 Diabetes Mellitus in Young Adults

Background:

Type 2 diabetes mellitus (T2DM) has been associated with impairment of cognitive function. Studies show a strong negative correlation between the levels of glycosylated hemoglobin and cognitive function in adult patients above the mean age of 60 years. In healthy adults, age-related cognitive impairment is mostly reported after the age of 60 years, hence the decline in cognitive function can be a part of normal aging without diabetes. Since the majority of patients with diabetes are between the ages of 40 and 59 years, it is crucial to ascertain whether the levels of glycosylated hemoglobin negatively correlate with the levels of cognitive function scores in adult patients of age 60 years or younger, similar to the way it correlates in patients older than 60 years of age, or not.

Aims:

We observed the relationship between the levels of glycosylated hemoglobin and the levels of cognitive function in patients of age 60 years or younger with T2DM.

Materials and Methods:

Eighty-two patients with T2DM underwent cognitive assessment testing by using a Modified Mini-Mental State Examination (3MS), and their cognitive function scores were correlated with their glycosylated hemoglobin levels, durations of diabetes, and levels of education.

Results:

Cognitive impairment was observed in 19.5% of the studied patients. We found a weakly negative relationship between the glycosylated hemoglobin level and cognitive function score (r = -0.292), a moderately negative relationship between the duration of diabetes and cognitive function score (r = -0.303), and a weakly positive relationship between the level of education and cognitive function score (r = 0.277).

Conclusion:

Cognitive impairment affects one-fifth of the patients of age 60 years or younger with T2DM. It is weakly negatively related to the glycosylated hemoglobin level, moderately negatively related to the duration of diabetes, and weakly positively related to the level of education.

Shared genetic etiology underlying Alzheimer's disease and type 2 diabetes

Epidemiological evidence supports the observation that subjects with type 2 diabetes (T2D) are at higher risk to develop Alzheimer's disease (AD). However, whether and how these two conditions are causally linked is unknown. Possible mechanisms include shared genetic risk factors, which were investigated in this study based on recent genome wide association study (GWAS) findings. In order to achieve our goal, we retrieved single nucleotide polymorphisms (SNPs) associated with T2D and AD from large-scale GWAS meta-analysis consortia and tested for overlap among the T2D- and AD-associated SNPs at various p-value thresholds. We then explored the function of the shared T2D/AD GWAS SNPs by leveraging expressional quantitative trait loci, pathways, gene ontology data, and co-expression networks. We found 927 SNPs associated with both AD and T2D with p-value ≤0.01, an overlap significantly larger than random chance (overlapping p-value of 6.93E-28). Among these, 395 of the shared GWAS SNPs have the same risk allele for AD and T2D, suggesting common pathogenic mechanisms underlying the development of both AD and T2D. Genes influenced by shared T2D/AD SNPs with the same risk allele were first identified using a SNP annotation variation (ANNOVAR) software, followed by using Association Protein-Protein Link Evaluator (DAPPLE) software to identify additional proteins that are known to physically interact with the ANNOVAR gene annotations. We found that gene annotations from ANNOVAR and DAPPLE significantly enriched specific KEGG pathways pertaining to immune responses, cell signaling and neuronal plasticity, cellular processes in which abnormalities are known to contribute to both T2D and AD pathogenesis. Thus, our observation suggests that among T2D subjects with common genetic predispositions (e.g., SNPs with consistent risk alleles for T2D and AD), dysregulation of these pathogenic pathways could contribute to the elevated risks for AD in subjects. Interestingly, we found that 532 of the shared T2D/AD GWAS SNPs had divergent risk alleles in the two diseases. For individual shared T2D/AD SNPs with divergent alleles, one of the allelic forms may contribute to one of the diseases (e.g., T2D), but not necessarily to the other (e.g., AD), or vice versa. Collectively, our GWAS studies tentatively support the epidemiological observation of disease concordance between T2D and AD. Moreover, the studies provide the much needed information for the design of future novel therapeutic approaches, for a subpopulation of T2D subjects with genetic disposition to AD, that could benefit T2D and reduce the risk for subsequent development of AD.

Treatment of Vascular Cognitive Impairment

OPINION STATEMENT

Cerebrovascular disease (CVD) is an important cause of cognitive dysfunction and dementia. The term vascular cognitive impairment (VCI) is used to describe the entire spectrum of cognitive dysfunction-ranging from mild impairment to dementia-attributable to all forms of cerebrovascular disease. Accurate assessment and management of vascular risk factors are a top priority in the treatment of VCI, particularly early in the disease when prevention strategies may prove to be more effective. There are limited treatment options to improve cognition and function in VCI. Several acetylcholinesterase inhibitors and the NMDA receptor antagonist memantine have been studied in large, well-designed trials. These agents are safe and provide modest cognitive benefits in vascular dementia (VaD) but have demonstrated inconsistent efficacy on functional measures. Other therapies, such as aspirin, calcium channel blockers, and vitamin supplementation, have less evidence to support their use in improving cognition in VCI. Although primary prevention trials suggest that treatment of hypertension, adherence to a Mediterranean diet, physical activity, and smoking cessation may reduce the risk of cognitive decline, there is limited evidence regarding these interventions in helping improve cognition in VCI. The pathophysiology and treatment of cerebral autosomal dominant arteriopathy with subcortical infarcts (CADASIL), cerebral amyloid angiopathy (CAA), and subcortical white matter disease (SWMD) deserves special consideration.

The impact of diabetes on cognitive decline: potential vascular, metabolic, and psychosocial risk factors

Older people with type 2 diabetes are at increased risk of developing cognitive impairment, for which several potential risk factors have been proposed. The present article reviews evidence in people with type 2 diabetes for associations of cognitive impairment with a range of vascular, metabolic, and psychosocial risk factors, many of which have a higher prevalence in people with type 2 diabetes than in non-diabetic adults of a similar age. Definitive research studies in this field are few in number. The risk factors may be involved in causal pathways or may act as useful markers of cerebrovascular damage (or both), and for which relatively consistent evidence is available, include poor glycemic control, hypoglycemia, microvascular disease, inflammation, and depression. For macrovascular disease, the strength of the association with cognitive impairment appears to depend on which vascular system has been examined. A role for pre-morbid ability in young adulthood as influencing the risk of both diabetes and cognitive impairment has also been suggested. The importance of considering inter-relationships between risk factors when investigating their potential contribution to cognitive impairment in future investigations is discussed.

Intensive glycaemic control and cognitive decline in patients with type 2 diabetes: a meta-analysis

The aim of this meta-analysis was to compare the effect of intensive vs standard glycaemic control on cognitive decline in type 2 diabetic patients. A systematic search of PubMed and ALOIS was conducted from inception up to October 30, 2014. Randomised controlled trials (RCTs) of type 2 diabetic patients comparing the rate of change in cognitive function among participants assigned to intensive vs standard glycaemic control were included. An inverse-variance-weighted random effects model was used to calculate standardised mean differences (SMDs) and 95% CIs. A total of 24 297 patients from five RCTs were included in the meta-analysis. Follow-up ranged from 3.3 to 6.2 years. The result from the pooled analysis showed that intensive glycaemic control was not associated with a slower rate of cognitive decline in patients with type 2 diabetes, compared with standard glycaemic control (SMD=0.02; 95% CI=-0.03 to 0.08) although there was some heterogeneity across individual studies (I(2)=68%, P for heterogeneity=0.01). There are few diabetes control trials including cognitive endpoints and a small number of trials comparing intensive and standard treatment strategies. Currently, intensive glycaemic control should not be recommended for prevention of cognitive decline in patients with type 2 diabetes because there is no evidence of its effectiveness. Moreover, the use of intensive diabetes treatment results in an increase of risk of hypoglycaemia, which is linked to a greater risk of poor cognition.

Glucose indices are associated with cognitive and structural brain measures in young adults

OBJECTIVE

To evaluate the possible early consequences of impaired glucose metabolism on the brain by assessing the relationship of diabetes, fasting blood glucose (FBG) levels, and insulin resistance with cognitive performance and brain integrity in healthy young and middle-aged adults.

METHODS

The sample included dementia-free participants (mean age 40 ± 9 years; 53% women) of the Framingham Heart Study third-generation cohort with cognitive testing of memory, abstract reasoning, visual perception, attention, and executive function (n = 2,126). In addition, brain MRI examination (n = 1,597) was used to determine white matter, gray matter, and white matter hyperintensity (WMH) volumes and fractional anisotropy measures. We used linear regression models to assess relationships between diabetes, FBG, and insulin resistance with cognition, lobar gray matter, and WMH volumes as well as voxel-based microstructural white matter integrity and gray matter density, adjusting for potential confounders. Mediating effect of brain lesions on the association of diabetes with cognitive performance was also tested.

RESULTS

Diabetes was associated with worse memory, visual perception, and attention performance; increased WMH; and decreased total cerebral brain and occipital lobar gray matter volumes. The link of diabetes with attention and memory was mediated through occipital and frontal atrophy, and the latter also through hippocampal atrophy. Both diabetes and increased FBG were associated with large areas of reductions in gray matter density and fractional anisotropy on voxel-based analyses.

CONCLUSIONS

We found that hyperglycemia is associated with subtle brain injury and impaired attention and memory even in young adults, indicating that brain injury is an early manifestation of impaired glucose metabolism.

Morphological covariance in anatomical MRI scans can identify discrete neural pathways in the brain and their disturbances in persons with neuropsychiatric disorders

We hypothesize that coordinated functional activity within discrete neural circuits induces morphological organization and plasticity within those circuits. Identifying regions of morphological covariation that are independent of morphological covariation in other regions therefore may therefore allow us to identify discrete neural systems within the brain. Comparing the magnitude of these variations in individuals who have psychiatric disorders with the magnitude of variations in healthy controls may allow us to identify aberrant neural pathways in psychiatric illnesses. We measured surface morphological features by applying nonlinear, high-dimensional warping algorithms to manually defined brain regions. We transferred those measures onto the surface of a unit sphere via conformal mapping and then used spherical wavelets and their scaling coefficients to simplify the data structure representing these surface morphological features of each brain region. We used principal component analysis (PCA) to calculate covariation in these morphological measures, as represented by their scaling coefficients, across several brain regions. We then assessed whether brain subregions that covaried in morphology, as identified by large eigenvalues in the PCA, identified specific neural pathways of the brain. To do so, we spatially registered the subnuclei for each eigenvector into the coordinate space of a Diffusion Tensor Imaging dataset; we used these subnuclei as seed regions to track and compare fiber pathways with known fiber pathways identified in neuroanatomical atlases. We applied these procedures to anatomical MRI data in a cohort of 82 healthy participants (42 children, 18 males, age 10.5 ± 2.43 years; 40 adults, 22 males, age 32.42 ± 10.7 years) and 107 participants with Tourette's Syndrome (TS) (71 children, 59 males, age 11.19 ± 2.2 years; 36 adults, 21 males, age 37.34 ± 10.9 years). We evaluated the construct validity of the identified covariation in morphology using DTI data from a different set of 20 healthy adults (10 males, mean age 29.7 ± 7.7 years). The PCA identified portions of structures that covaried across the brain, the eigenvalues measuring the magnitude of the covariation in morphology along the respective eigenvectors. Our results showed that the eigenvectors, and the DTI fibers tracked from their associated brain regions, corresponded with known neural pathways in the brain. In addition, the eigenvectors that captured morphological covariation across regions, and the principal components along those eigenvectors, identified neural pathways with aberrant morphological features associated with TS. These findings suggest that covariations in brain morphology can identify aberrant neural pathways in specific neuropsychiatric disorders.

[Diabetes mellitus and dementia]

Diabetes mellitus, particularly type 2 diabetes, is a risk factor for dementia and this holds true for incident vascular dementia and Alzheimer's disease. Cerebrovascular complications of diabetes and chronic mild inflammation in insulin resistant states partly account for this increased risk. In addition, cellular resistance to the trophic effects of insulin on neurons and glial cells favor the accumulation of toxic metabolic products, such as amyloid and hyperphosphorylated tau protein (pTau). Weight loss frequently precedes overt cognitive symptoms of Alzheimer's disease. This results in an increased risk of hypoglycemic episodes in stable diabetic patients who are on suitably adjusted doses of oral insulin or insulinotropic antidiabetic drugs. In turn, hypoglycemic episodes may induce further damage in the vulnerable brains of type 2 diabetes patients. Patients with unexplained weight loss, hypoglycemic episodes and subjective memory complaints must be screened for dementia. Once dementia has been diagnosed the goals of diabetes management must be reevaluated as prevention of hypoglycemia becomes more important than tight metabolic control. As weight loss accelerates the rate of cognitive decline, nutritional goals must aim at stabilizing body weight. There is no available evidence on whether drug treatment of diabetes in middle-aged persons can help to prevent dementia; however, physical exercise, mental activity and higher education have preventive effects on the risk of dementia in later life. In addition, nutritional recommendations that are effective in preventing cardiovascular events have also been shown to reduce the risk of dementia.

Glucose regulation and cognitive function after bariatric surgery

INTRODUCTION

Obesity is associated with cognitive impairment, and bariatric surgery has been shown to improve cognitive functioning. Rapid improvements in glycemic control are common after bariatric surgery and likely contribute to these cognitive gains. We examined whether improvements in glucose regulation are associated with better cognitive function following bariatric surgery.

METHOD

A total of 85 adult bariatric surgery patients underwent computerized cognitive testing and fasting blood draw for glucose, insulin, and glycated hemoglobin (HbA1c) at baseline and 12 months postoperatively.

RESULTS

Significant improvements in both cognitive function and glycemic control were observed among patients. After controlling for baseline factors, 12-month homeostatic model assessment of insulin resistance HOMA-IR predicted 12-month digits backward (β = -.253, p < .05), switching of attention-A (β = .156, p < .05), and switching of attention-B (β = -.181, p < .05). Specifically, as HOMA-IR decreased over time, working memory, psychomotor speed, and cognitive flexibility improved. Decreases in HbA1c were not associated with postoperative cognitive improvements. After controlling for baseline cognitive test performance, changes in body mass index (BMI) were also not associated with 12-month cognitive function.

CONCLUSIONS

Small effects of improved glycemic control on improved aspects of attention and executive function were observed following bariatric surgery among severely obese individuals. Future research is needed to identify the underlying mechanisms for the neurocognitive benefits of these procedures.

Vascular factors and multiple measures of early brain health: CARDIA brain MRI study

OBJECTIVE

To identify early changes in brain structure and function that are associated with cardiovascular risk factors (CVRF).

DESIGN

Cross-sectional brain Magnetic Resonance I (MRI) study.

SETTING

Community based cohort in three U.S. sites.

PARTICIPANTS

A Caucasian and African-American sub-sample (n= 680; mean age 50.3 yrs) attending the 25 year follow-up exam of the Coronary Artery Risk Development in Young Adults Study.

PRIMARY AND SECONDARY OUTCOMES

3T brain MR images processed for quantitative estimates of: total brain (TBV) and abnormal white matter (AWM) volume; white matter fractional anisotropy (WM-FA); and gray matter cerebral blood flow (GM-CBF). Total intracranial volume is TBV plus cerebral spinal fluid (TICV). A Global Cognitive Function (GCF) score was derived from tests of speed, memory and executive function.

RESULTS

Adjusting for TICV and demographic factors, current smoking was significantly associated with lower GM-CBF and TBV, and more AWM (all <0.05); SA with lower GM-CBF, WM-FA and TBV (p=0.01); increasing BMI with decreasing GM-CBF (p<0003); hypertension with lower GM-CBF, WM-FA, and TBV and higher AWM (all <0.05); and diabetes with lower TBV (p=0.007). The GCS was lower as TBV decreased, AWM increased, and WM-FA (all p<0.01).

CONCLUSION

In middle age adults, CVRF are associated with brain health, reflected in MRI measures of structure and perfusion, and cognitive functioning. These findings suggest markers of mid-life cardiovascular and brain health should be considered as indication for early intervention and future risk of late-life cerebrovascular disease and dementia.

Prediabetes and associated disorders

Prediabetes represents an elevation of plasma glucose above the normal range but below that of clinical diabetes. Prediabetes includes individuals with IFG, IGT, IFG with IGT and elevated HbA1c levels. Insulin resistance and β-cell dysfunction are characteristic of this disorder. The diagnosis of prediabetesis is vital as both IFG and IGT are indeed well-known risk factors for type 2 diabetes with a greater risk in the presence of combined IFG and IGT. Furthermore, as will be illustrated in this review, prediabetes is associated with associated disorders typically only considered in with established diabetes. These include cardiovascular disease, periodontal disease, cognitive dysfunction, microvascular disease, blood pressure abnormalities, obstructive sleep apnea, low testosterone, metabolic syndrome, various biomarkers, fatty liver disease, and cancer. As the vast majority of individuals with prediabetes are unaware of their diagnosis, it is therefore vital that the associated conditions are identified, particularly in the presence of mild hyperglycemia, so they may benefit from early intervention.

Cognitive function in patients with diabetes mellitus: guidance for daily care

Diabetes mellitus is associated with an increase in the risk of dementia and the proportion of patients who convert from mild cognitive impairment (MCI) to dementia. In addition to MCI and dementia, the stages of diabetes-associated cognitive dysfunction include subtle cognitive changes that are unlikely to affect activities of daily life or diabetes self-management. These diabetes-associated cognitive decrements have structural brain correlates detectable with brain MRI, but usually show little progression over time. Although cognitive decrements do not generally represent a pre-dementia stage in patients below the age of 60-65 years, in older individuals these subtle cognitive changes might represent the earliest stages of a dementia process. Acknowledgment of diabetes-associated cognitive decrements can help to improve understanding of patients' symptoms and guide management. Future challenges are to establish the importance of screening for cognitive impairment in people with diabetes, to identify those at increased risk of accelerated cognitive decline at an early stage, and to develop effective treatments.

E3 ubiquitin ligase Siah-1 downregulates synaptophysin expression under high glucose and hypoxia

BACKGROUND

Diabetes is proved to be one of the independent risk factors for cognitive dysfunction. The pathophysiologic changes caused by diabetes including hyperglycemia and tissue hypoxia may contribute greatly to cognitive decline. In the present study, we demonstrate E3 Ubiquitin Ligase Siah-1 downregulates the key synaptic protein Synaptophysin expression under high glucose and hypoxia condition which may be the underlying factor leading to cognitive dysfunction in diabetic patients.

METHODS

In this study, hypoxia (2% oxygen) and high glucose (50 mM) were used to treat primary neuronal culture. By using quantitative PCR and western blotting we determined the influence of hypoxia and high glucose on the expression of synaptophysin and Siah-1 and the phosphorylated forms of extracellular signal-regulated kinase (ERK). Knockdown of Siah-1, inhibitors for proteasome, lysosome and ERK kinase was employed to evaluate the role of Siah-1 and ERK activity on the expression of synaptophysin. By immunoprecipitation we also examined the role of Siah-1 in the ubiquitination of synaptophysin under hypoxic and hyperglycemic condition.

RESULTS

We demonstrated that hypoxia and high glucose together but not hypoxia or high glucose along mediated posttranscriptional reduction of synaptophysin with increased ERK phosphorylation and Siah-1 expression. The downregulation of synaptophysin was reversed by inhibition of ERK and Siah-1 knockdown. Overexpression of Siah-1 accelerated the degradation of synaptophysin under hypoxia and high glucose conditions and promoted the ubiquitination of synaptophysin.

CONCLUSIONS

The present results demonstrate that Siah-1 is the key factor that contributes to hypoxia and high glucose mediated synaptophysin degradation.

Spatial patterns of structural brain changes in type 2 diabetic patients and their longitudinal progression with intensive control of blood glucose

OBJECTIVE

Understanding the effect of diabetes as well as of alternative treatment strategies on cerebral structure is critical for the development of targeted interventions against accelerated neurodegeneration in type 2 diabetes. We investigated whether diabetes characteristics were associated with spatially specific patterns of brain changes and whether those patterns were affected by intensive versus standard glycemic treatment.

RESEARCH DESIGN AND METHODS

Using baseline MRIs of 488 participants with type 2 diabetes from the Action to Control Cardiovascular Risk in Diabetes-Memory in Diabetes (ACCORD-MIND) study, we applied a new voxel-based analysis methodology to identify spatially specific patterns of gray matter and white matter volume loss related to diabetes duration and HbA1c. The longitudinal analysis used 40-month follow-up data to evaluate differences in progression of volume loss between intensive and standard glycemic treatment arms.

RESULTS

Participants with longer diabetes duration had significantly lower gray matter volumes, primarily in certain regions in the frontal and temporal lobes. The longitudinal analysis of treatment effects revealed a heterogeneous pattern of decelerated loss of gray matter volume associated with intensive glycemic treatment. Intensive treatment decelerated volume loss, particularly in regions adjacent to those cross-sectionally associated with diabetes duration. No significant relationship between low versus high baseline HbA1c levels and brain changes was found. Finally, regions in which cognitive change was associated with longitudinal volume loss had only small overlap with regions related to diabetes duration and to treatment effects.

CONCLUSIONS

Applying advanced quantitative image pattern analysis methods on longitudinal MRI data of a large sample of patients with type 2 diabetes, we demonstrate that there are spatially specific patterns of brain changes that vary by diabetes characteristics and that the progression of gray matter volume loss is slowed by intensive glycemic treatment, particularly in regions adjacent to areas affected by diabetes.

Glycemia and cognitive function in metabolic syndrome and coronary heart disease

OBJECTIVE

Higher hemoglobin A1c (HbA1c) is associated with lower cognitive function in type 2 diabetes. To determine whether associations persist at lower levels of dysglycemia in patients who have established cardiovascular disease, cognitive performance was assessed in the Targeting INflammation Using SALsalate in CardioVascular Disease (TINSAL-CVD) trial.

METHODS

The age-adjusted relationships between HbA1c and cognitive performance measured by the Mini-Mental State Examination, Digit Symbol Substitution Test, Rey Auditory Verbal Learning Test, Trail Making Test, and Categorical Verbal Fluency were assessed in 226 men with metabolic syndrome and established stable coronary artery disease.

RESULTS

Of the participants, 61.5% had normoglycemia, 20.8% had impaired fasting glucose, and 17.7% had type 2 diabetes. HbA1c was associated with cognitive function tests of Digit Symbol Substitution Test, Rey Auditory Verbal Learning Test, Trail Making Test, and Categorical Verbal Fluency (all P < .02), but not the Mini-Mental State Examination. In an age-adjusted model, a 1% (11 mmol/mol) higher HbA1c value was associated with a 5.9 lower Digit Symbol Substitution Test score (95% confidence interval [CI], -9.58 to -2.21; P < .0001); a 2.44 lower Rey Auditory Verbal Learning Test score (95% CI, -4.00 to -0.87; P < .0001); a 15.6 higher Trail Making Test score (95% CI, 5.73 to 25.6; P < .0001); and a 3.71 lower Categorical Verbal Fluency score (95% CI, -6.41 to -1.01; P < .02). In a multivariate model adjusting for age, education, and cardiovascular covariates, HbA1c remained associated with cognitive function tests of Rey Auditory Verbal Learning Test (R(2) = 0.27, P < .0001), Trail Making Test (R(2) = 0.18, P < .0001), and Categorical Verbal Fluency (R(2) = 0.20, P < .0001), although association with the Digit Symbol Substitution Test was reduced.

CONCLUSIONS

Higher HbA1c is associated with lower cognitive function performance scores across multiple domain tests in men with metabolic syndrome and coronary artery disease. Future studies may demonstrate whether glucose lowering within the normative range improves cognitive health.

Diabetes Mellitus, Cognitive Impairment, and Traditional Chinese Medicine

Diabetes mellitus (DM) is a metabolic disorder affecting a large number of people worldwide. Numerous studies have demonstrated that DM can cause damage to multiple systems, leading to complications such as heart disease, cancer, and cerebrovascular disorders. Numerous epidemiological studies have shown that DM is closely associated with dementia and cognition dysfunction, with recent research focusing on the role of DM-mediated cerebrovascular damage in dementia. Despite the therapeutic benefits of antidiabetic agents for the treatment of DM-mediated cognitive dysfunction, most of these pharmaceutical agents are associated with various undesirable side-effects and their long-term benefits are therefore in doubt. Early evidence exists to support the use of traditional Chinese medicine (TCM) interventions, which tend to have minimal toxicity and side-effects. More importantly, these TCM interventions appear to offer significant effects in reducing DM-related complications beyond blood glucose control. However, more research is needed to further validate these claims and to explore their relevant mechanisms of action. The aims of this paper are (1) to provide an updated overview on the association between DM and cognitive dysfunction and (2) to review the scientific evidence underpinning the use of TCM interventions for the treatment and prevention of DM-induced cognitive dysfunction and dementia.

Glucose regulation, cognition, and brain MRI in type 2 diabetes: a systematic review

Type 2 diabetes is associated with cognitive dysfunction and structural brain changes. Abnormalities in glucose regulation are involved in several complications related to type 2 diabetes, but their role in these cerebral complications is unclear. We systematically reviewed studies of the association between glucose regulation (glycaemia, hypoglycaemic events, insulin concentration, insulin resistance, and glucose-lowering treatment) and cognitive function and brain abnormalities on MRI in people with type 2 diabetes. The 86 papers included showed that glycaemia, particularly high HbA1c concentration and glucose variability, are negatively associated with cognitive function in people with type 2 diabetes without dementia. However, the strength of this association is weak, and HbA1c generally accounted for less than 10% of the variance in cognition. Importantly, few studies have measured long-term cerebral outcomes, such as dementia and structural brain changes on MRI, and the effect of glucose-lowering treatment on these outcomes. More randomised controlled trials are needed to establish the effect of glucose-lowering treatment on long-term cognitive function in people with type 2 diabetes.

Cognitive and physical function in chronic kidney disease

PURPOSE OF REVIEW

Both cognitive and physical function are commonly impaired in individuals with chronic kidney disease (CKD), resulting in important impacts on their quality of life and overall health. This review summarizes the burden of cognitive and physical impairment in CKD, focusing on recent research that highlights a possible unifying microvascular cause among these shared comorbid conditions.

RECENT FINDINGS

Multiple small studies have been published recently evaluating cognitive and physical functioning in people with CKD. These studies overall demonstrate a high burden of comorbid conditions in people with CKD, including microvascular disease, that may result in cognitive impairment. Additionally, studies demonstrate that physical function is substantially worse than expected in individuals with CKD, that decreased physical activity is associated with worse outcomes, that frailty is very common and associated with an increased risk of death, and that structured exercise programs have small but tangible short-term effects on markers of physical performance.

SUMMARY

Impaired cognitive function and physical performance are important factors impacting the lives of people with CKD. Further research is necessary to better treat these important comorbid conditions in people with CKD.

Diabetes in midlife and cognitive change over 20 years: a cohort study

BACKGROUND

Type 2 diabetes is associated with dementia risk, but evidence is limited for possible associations of diabetes and prediabetes with cognitive decline.

OBJECTIVE

To determine whether diabetes in midlife is associated with 20-year cognitive decline and to characterize long-term cognitive decline across clinical categories of hemoglobin A1c (HbA1c) levels.

DESIGN

Prospective cohort study.

SETTING

The community-based ARIC (Atherosclerosis Risk in Communities) study.

PARTICIPANTS

13,351 black and white adults aged 48 to 67 years at baseline (1990 to 1992).

MEASUREMENTS

Diabetes was defined by self-reported physician diagnosis or medication use or HbA1c level of 6.5% or greater. Undiagnosed diabetes, prediabetes, and glucose control in persons with diagnosed diabetes were defined by clinical categories of HbA1c level. Delayed word recall, digit symbol substitution, and word fluency tests were used to assess cognitive performance and were summarized with a global Z score.

RESULTS

Diabetes in midlife was associated with a 19% greater cognitive decline over 20 years (adjusted global Z-score difference, -0.15 [;95% CI, -0.22 to -0.08];) compared with no diabetes. Cognitive decline was significantly greater among persons with prediabetes (HbA1c level of 5.7% to 6.4%) than among those with an HbA1c level less than 5.7%. Participants with poorly controlled diabetes (HbA1c level ≥ 7.0%) had greater decline than those whose diabetes was controlled (adjusted global Z-score difference, -0.16; P = 0.071). Longer-duration diabetes was also associated with greater late-life cognitive decline (P for trend < 0.001). Rates of decline did not differ significantly between white and black persons (P for interaction = 0.44).

LIMITATION

Single HbA1c measurement at baseline, 1 test per cognitive domain, and potential geographic confounding of race comparisons.

CONCLUSION

Diabetes prevention and glucose control in midlife may protect against late-life cognitive decline.

PRIMARY FUNDING SOURCE

National Institutes of Health.

The cross-sectional and longitudinal associations of diabetic retinopathy with cognitive function and brain MRI findings: the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial

OBJECTIVE

Longitudinal evidence linking diabetic retinopathy with changes in brain structure and cognition is sparse. We used data from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial to determine whether diabetic retinopathy at baseline predicted changes in brain structure or cognition 40 months later.

RESEARCH DESIGN AND METHODS

Participants from the ACCORD-MIND and ACCORD-Eye substudies were included in analyses of cognition (n = 1,862) and MRI-derived brain variables (n = 432). Retinopathy was categorized as none, mild nonproliferative, or moderate/severe. Tests of cognition included the Mini-Mental State Examination (MMSE), Digit Symbol Substitution Test (DSST), Rey Auditory Verbal Learning Test, and Stroop test. Primary brain outcomes were gray matter and abnormal white matter volumes.

RESULTS

Baseline retinopathy was associated with lower gray matter volume (adjusted means of 470, 466, and 461 cm(3) for none, mild, and moderate/severe retinopathy, respectively; P = 0.03). Baseline retinopathy also predicted a greater change in MMSE and DSST scores at 40 months in each retinopathy category (MMSE: -0.20, -0.57, and -0.42, respectively [P = 0.04]; DSST: -1.30, -1.84, and -2.89, respectively [P = 0.01]).

CONCLUSIONS

Diabetic retinopathy is associated with future cognitive decline in people with type 2 diabetes. Although diabetic retinopathy is not a perfect proxy for diabetes-related brain and cognitive decline, patients with type 2 diabetes and retinopathy represent a subgroup at higher risk for future cognitive decline.

Effect of hypoglycemia on brain structure in people with type 2 diabetes: epidemiological analysis of the ACCORD-MIND MRI trial

OBJECTIVE

The effect of hypoglycemia related to treatment of type 2 diabetes mellitus (T2DM) on brain structure remains unclear. We aimed to assess whether symptomatic severe hypoglycemia is associated with brain atrophy and/or white matter abnormalities.

RESEARCH DESIGN AND METHODS

We included T2DM participants with brain MRI from the Action to Control Cardiovascular Risk in Diabetes-Memory in Diabetes (ACCORD-MIND) trial. Symptomatic severe hypoglycemia was defined as blood glucose <2.8 mmol/L or symptoms resolved with treatments that required the assistance of another person or medical assistance (hypoglycemia requiring assistance [HA]). Standardized brain MRI was performed at baseline and at 40 months. Total brain volume (TBV) and abnormal white matter (AWM) volume were calculated using an automated computer algorithm. Brain MRI scans of hypoglycemic participants were also reviewed for local disease.

RESULTS

Of the 503 T2DM participants (mean age, 62 years) with successful baseline and 40-month brain MRI, 28 had at least one HA episode during the 40-month follow-up. Compared with participants without HA, those with HA had marginally significant less atrophy (less decrease in TBV) from baseline to 40 months (-9.55 [95% CI -15.21, -3.90] vs. -15.38 [95% CI -16.64, -14.12], P = 0.051), and no significant increase of AWM volume (2.06 [95% CI 1.71, 2.49] vs. 1.84 [95% CI 1.76, 1.91], P = 0.247). In addition, no unexpected local signal changes or volume loss were seen on hypoglycemic participants' brain MRI scans.

CONCLUSIONS

Our study suggests that hypoglycemia related to T2DM treatment may not accentuate brain pathology, specifically brain atrophy or white matter abnormalities.

Diabetes mellitus is independently associated with more severe cognitive impairment in Parkinson disease

BACKGROUND

There is increasing interest in interactions between metabolic syndromes and neurodegeneration. Diabetes mellitus (DM) contributes to cognitive impairment in the elderly but its effect in Parkinson disease (PD) is not well studied.

OBJECTIVE

To investigate effects of comorbid DM on cognition in PD independent from PD-specific primary neurodegenerations.

METHODS

Cross-sectional study. Patients with PD (n = 148); age 65.6 ± 7.4 years, Hoehn and Yahr stage 2.4 ± 0.6, with (n = 15) and without (n = 133) comorbid type II DM, underwent [(11)C]methyl-4-piperidinyl propionate (PMP) acetylcholinesterase (AChE) PET imaging to assess cortical cholinergic denervation, [(11)C]dihydrotetrabenazine (DTBZ) PET imaging to assess nigrostriatal denervation, and neuropsychological assessments. A global cognitive Z-score was calculated based on normative data. Analysis of covariance was performed to determine cognitive differences between subjects with and without DM while controlling for nigrostriatal denervation, cortical cholinergic denervation, levodopa equivalent dose and education covariates.

RESULTS

There were no significant differences in age, gender, Hoehn and Yahr stage or duration of disease between diabetic and non-diabetic PD subjects. There was a non-significant trend toward lower years of education in the diabetic PD subjects compared with non-diabetic PD subjects. PD diabetics had significantly lower mean (±SD) global cognitive Z-scores (-0.98 ± 1.01) compared to the non-diabetics (-0.36 ± 0.91; F = 7.78, P = 0.006) when controlling for covariate effects of education, striatal dopaminergic denervation, and cortical cholinergic denervation (total model F = 8.39, P < 0.0001).

CONCLUSION

Diabetes mellitus is independently associated with more severe cognitive impairment in PD likely through mechanisms other than disease-specific neurodegenerations.

Roles of resveratrol and other grape-derived polyphenols in Alzheimer's disease prevention and treatment

Alzheimer's disease (AD) is a devastating disorder that strikes 1 in 10 Americans over the age of 65, and almost half of all Americans over 85 years old. The odds of an individual developing AD double every five years after the age of 65. While it has become increasingly common to meet heart attack or cancer survivors, there are no AD survivors. There is mounting evidence that dietary polyphenols, including resveratrol, may beneficially influence AD. Based on this consideration, several studies reported in the last few years were designed to validate sensitive and reliable translational tools to mechanistically characterize brain bioavailable polyphenols as disease-modifying agents to help prevent the onset of AD dementia and other neurodegenerative disorders. Several research groups worldwide with expertise in AD, plant biology, nutritional sciences, and botanical sciences have reported very high quality studies that ultimately provided the necessary information showing that polyphenols and their metabolites, which come from several dietary sources, including grapes, cocoa etc., are capable of preventing AD. The ultimate goal of these studies was to provide novel strategies to prevent the disease even before the onset of clinical symptoms. The studies discussed in this review article provide support that the information gathered in the last few years of research will have a major impact on AD prevention by providing vital knowledge on the protective roles of polyphenols, including resveratrol. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

The synergistic effects of HIV, diabetes, and aging on cognition: implications for practice and research

Thanks to highly active antiretroviral therapy, many people infected with HIV will likely live into old age. Although this is a welcome prognosis, new issues are emerging that may complicate the ability to successfully age in this clinical population. HIV and aging independently are related to cognitive impairments, so there are concerns that those aging with HIV may be more at risk of such cognitive impairments. Moreover, highly active antiretroviral therapy itself can create metabolic disorders, such as prediabetes and/or frank type 2 diabetes, which have also been linked to poorer cognitive functioning. Thus, concerns increase that, as people age with HIV and develop comorbid metabolic disorders that may lead to type 2 diabetes, they will be at triple risk of developing cognitive impairments that can impair everyday functioning and reduce quality of life. This article explores these issues and provides implications for practice and research.

Diabetes and cognitive outcomes in a nationally representative sample: the National Health and Aging Trends Study

BACKGROUND

The prevalence of both type II diabetes mellitus (DM) and cognitive impairment is high and increasing in older adults. We examined the extent to which DM diagnosis was associated with poorer cognitive performance and dementia diagnosis in a population-based cohort of US older adults.

METHODS

We studied 7,606 participants in the National Health and Aging Trends Study, a nationally representative cohort of Medicare beneficiaries aged 65 years and older. DM and dementia diagnosis were based on self-report from participants or proxy respondents, and participants completed a word-list memory test, the Clock Drawing Test, and gave a subjective assessment of their own memory.

RESULTS

In unadjusted analyses, self-reported DM diagnosis was associated with poorer immediate and delayed word recall, worse performance on the Clock Drawing Test, and poorer self-rated memory. After adjusting for demographic characteristics, body mass index, depression and anxiety symptoms, and medical conditions, DM was associated with poorer immediate and delayed word recall and poorer self-rated memory, but not with the Clock Drawing Test performance or self-reported dementia diagnosis. After excluding participants with a history of stroke, DM diagnosis was associated with poorer immediate and delayed word recall and the Clock Drawing Test performance, and poorer self-rated memory, but not with self-reported dementia diagnosis.

CONCLUSIONS

In this recent representative sample of older Medicare enrollees, self-reported DM was associated with poorer cognitive test performance. Findings provide further support for DM as a potential risk factor for poor cognitive outcomes. Studies are needed that investigate whether DM treatment prevents cognitive decline.

Hyperglycemia induces memory impairment linked to increased acetylcholinesterase activity in zebrafish (Danio rerio)

Diabetes mellitus, which causes hyperglycemia, affects the central nervous system and can impairs cognitive functions, such as memory. The aim of this study was to investigate the effects of hyperglycemia on memory as well as on the activity of acethylcholinesterase. Hyperglycemia was induced in adult zebrafish by immersion in glucose 111mM by 14 days. The animals were divided in 4 groups: control, glucose-treated, glucose-washout 7-days and glucose-washout 14-days. We evaluated the performance in inhibitory avoidance task and locomotor activity. We also determined acethylcholinesterase activity and gene expression from whole brain. In order to counteract the effect of hyperglycemia underlined by effects on acethylcholinesterase activity, we treated the animals with galantamine (0.05ng/g), an inhibitor of this enzyme. Also we evaluated the gene expression of insulin receptor and glucose transporter from zebrafish brain. The hyperglycemia promoted memory deficit in adult zebrafish, which can be explained by increased AChE activity. The ache mRNA levels from zebrafish brain were decrease in 111mM glucose group and returned to normal levels after 7 days of glucose withdrawal. Insulin receptors (insra-1, insra-2, insrb-1 and insrb-2) and glut-3 mRNA levels were not significantly changed. Our results also demonstrated that galantamine was able to reverse the memory deficit caused by hyperglycemia, demonstrating that these effects involve modulation of AChE activity. These data suggest that the memory impairment induced by hyperglycemia is underlined by the cholinergic dysfunction caused by the mechanisms involving the control of acetylcholinesterase function and gene expression.

The Israel Diabetes and Cognitive Decline (IDCD) study: Design and baseline characteristics

BACKGROUND

Type 2 diabetes (T2D) is associated with increased risk of dementia. The prospective longitudinal Israel Diabetes and Cognitive Decline study aims at identifying T2D-related characteristics associated with cognitive decline.

METHODS

Subjects are population-based T2D 65+, initially cognitively intact. Medical conditions, blood examinations, and medication use data are since 1998; cognitive, functional, demographic, psychiatric, DNA, and inflammatory marker study assessments were conducted every 18 months. Because the duration of T2D reflects its chronicity and implications, we compared short (0-4.99 years), moderate (5-9.99), and long (10+) duration for the first 897 subjects.

RESULTS

The long duration group used more T2D medications, had higher glucose, lower glomerular filtration rate, slower walking speed, and poorer cognitive functioning. Duration was not associated with most medical, blood, urine, and vital characteristics.

CONCLUSIONS

Tracking cognition, with face-to-face evaluations, exploiting 15 years of historical detailed computerized, easily accessible, and validated T2D-related characteristics may provide novel insights into T2D-related dementia.

The ApoE4 genotype modifies the relationship of long-term glycemic control with cognitive functioning in elderly with type 2 diabetes

AIM

To assess whether the APOE4 genotype affects the relationship of long-term glycemic control with cognitive function in elderly with type 2 diabetes (T2D).

METHODS

Participants were cognitively normal and pertained to a Diabetes Registry which provided access to HbA1c levels and other T2D related factors since 1998. Glycemic control was defined as the mean of all HbA1c measurements available (averaging 18 measurements) per subject. Four cognitive domains (episodic memory, semantic categorization, attention/working memory and executive function), based on factor analysis and an overall cognitive score (the sum of the 4 cognitive domains) were the outcome measures.

RESULTS

The analysis included 808 subjects; 107 (11.9%) subjects had ≥1ApoE4 allele. In ApoE4 carriers, higher mean HbA1c level was significantly associated with lower scores on all cognitive measures except attention/working memory (p-values ranging from 0.047 to 0.003). In ApoE4 non-carriers, higher mean HbA1c level was significantly associated with lower scores on executive function, but not with other cognitive measures-despite the larger sample size. Compared to non-carriers, there were significantly stronger associations in ApoE4 carriers for overall cognition (p=0.02), semantic categorization (p=0.03) and episodic memory (p=0.02), and the difference for executive function approached statistical significance (p=0.06).

CONCLUSION

In this cross-sectional study of cognitively normal T2D subjects, higher mean HbA1c levels were generally associated with lower cognitive performance in ApoE4 carriers, but not in non-carriers, suggesting that ApoE4 affects the relationship between long-term glycemic control and cognition, so APOE4 carriers may be more vulnerable to the insults of poor glycemic control.

Brain changes underlying cognitive dysfunction in diabetes: what can we learn from MRI?

Diabetes is associated with cognitive dysfunction and an increased risk of dementia. This article addresses findings with brain MRI that may underlie cognitive dysfunction in diabetes. Studies in adults with type 1 diabetes show regional reductions in brain volume. In those with a diabetes onset in childhood, these volume reductions are likely to reflect the sum of changes that occur during brain development and changes that occur later in life due to exposure to diabetes-related factors. Type 2 diabetes is associated with global brain atrophy and an increased burden of small-vessel disease. These brain changes occur in the context of aging and often also in relation to an adverse vascular risk factor profile. Advanced imaging techniques detect microstructural lesions in the cerebral gray and white matter of patients with diabetes that affect structural and functional connectivity. Challenges are to further unravel the etiology of these cerebral complications by integrating findings from different imaging modalities and detailed clinical phenotyping and by linking structural MRI abnormalities to histology. A better understanding of the underlying mechanisms is necessary to establish interventions that will improve long-term cognitive outcomes for patients with type 1 and type 2 diabetes.

Effect of diabetes on brain structure: the action to control cardiovascular risk in diabetes MR imaging baseline data

PURPOSE

To investigate the association of characteristics of type 2 diabetes mellitus (duration and biochemical severity of diabetes) to brain structure measured on magnetic resonance (MR) images, specifically testing whether more severity in metrics of diabetes is inversely correlated with brain volumes and positively correlated with ischemic lesion volumes.

MATERIALS AND METHODS

This study protocol was approved by the institutional review board of each center and participants provided written informed consent. Baseline severity of diabetes was evaluated by testing fasting plasma glucose levels, hemoglobin A1c levels, and duration of diabetes. MR imaging was performed with fluid-attenuated inversion recovery, proton-density, T2-weighted, and T1-weighted sequences, which were postprocessed with an automated computer algorithm that classified brain tissue as gray or white matter and as normal or ischemic. Separate linear regression models adjusted for potential confounding factors were used to investigate the relationship of the diabetes measures to MR imaging outcomes in 614 participants (mean age, 62 years; mean duration of type 2 diabetes mellitus, 9.9 years).

RESULTS

The mean volumes of total gray matter (463.9 cm(3)) and total white matter (463.6 cm(3)) were similar. The mean volume of abnormal tissue was 2.5 cm(3), mostly in the white matter (81% white matter, 5% gray matter, 14% deep gray and white matter). Longer duration of diabetes and higher fasting plasma glucose level were associated with lower normal (β = -0.431 and -0.053, respectively; P < .01) and total gray matter volumes (β = -0.428 and -0.053, respectively; P < .01). Fasting plasma glucose was also inversely correlated with ischemic lesion volume (β = -0.006; P < .04). Hemoglobin A1c level was not associated with any MR imaging measure.

CONCLUSION

Longer duration of diabetes is associated with brain volume loss, particularly in the gray matter, possibly reflecting direct neurologic insult; biochemical measures of glycemia were less consistently related to MR imaging changes. Contrary to common clinical belief, in this sample of patients with type 2 diabetes mellitus, there was no association of diabetes characteristics with small vessel ischemic disease in the brain.

Type 2 diabetes as a risk factor for cognitive impairment: current insights

Type 2 diabetes mellitus (T2DM) is a risk factor for cognitive dysfunction and dementia in the elderly. T2DM has been thought to be associated with vascular diseases, eventually leading to vascular dementia, but recent studies have established that T2DM is also associated with Alzheimer's disease (AD). With the increase in the number of elderly individuals with T2DM, the number of diabetic patients with cognitive dysfunction has been increasing. T2DM may accelerate AD-associated pathologies through insulin resistance. Vascular pathologies may also be associated with cognitive dysfunction and dementia in T2DM subjects. Several other mechanisms also seem to be involved in T2DM-related cognitive dysfunction. More investigations to clarify the association of T2DM with cognitive impairment are warranted. These investigations may help to increase our understanding of AD and open a new door to the development of therapeutics. Recent pharmaceutical advancement in T2DM treatment has resulted in the availability of a wide range of antidiabetics. Some evidence has suggested that antidiabetic therapies help to prevent cognitive dysfunction. At present, however, the optimal level of blood glucose control and the best combination of medications to achieve it in terms of cognitive preservation have not been established. More investigation is warranted. Cognitive dysfunction is an emerging new complication of T2DM that requires further study.

Duration of type 2 diabetes and very low density lipoprotein levels are associated with cognitive dysfunction in metabolic syndrome

Type 2 diabetes (T2D) is now recognized as an independent risk factor for accelerated cognitive decline and neurological conditions like Alzheimer's disease. Less is known about the neurocognitive function of T2D patients with comorbid metabolic syndrome, despite their elevated risk for impairment. Computerized testing in 47 adults with T2D that met criteria for NCEP metabolic syndrome revealed that cognitive impairment was prevalent, including 13% in tests of memory, 50% in attention, and 35% in executive function. Partial correlations showed that longer duration of diabetes was associated with poorer performance on tests of basic attention (r = -0.43), working memory (r = 0.43), and executive function (r = 0.42). Strong associations between very low density lipoprotein and poor cognitive function also emerged, including tests of set shifting (r = 0.47) and cognitive inhibition (r = -0.51). Findings suggest that patients with T2D that meet criteria for metabolic syndrome are at high risk for cognitive impairment. Prospective studies should look to replicate these findings and examine the possible neuroprotective effects of lipid-lowering medication in this population.

Trajectories in glycemic control over time are associated with cognitive performance in elderly subjects with type 2 diabetes

Objective

To study the relationships of long-term trajectories of glycemic control with cognitive performance in cognitively normal elderly with type 2 diabetes (T2D).

Methods

Subjects (n = 835) pertain to a diabetes registry (DR) established in 1998 with an average of 18 HbA1c measurements per subject, permitting identification of distinctive trajectory groups of HbA1c and examining their association with cognitive function in five domains: episodic memory, semantic categorization, attention/working memory, executive function, and overall cognition. Analyses of covariance compared cognitive function among the trajectory groups adjusting for sociodemographic, cardiovascular, diabetes-related covariates and depression.

Results

Subjects averaged 72.8 years of age. Six trajectories of HbA1c were identified, characterized by HbA1c level at entry into the DR (Higher/Lower), and trend over time (Stable/Decreasing/Increasing). Both groups with a trajectory of decreasing HbA1c levels had high HbA1c levels at entry into the DR (9.2%, 10.7%), and high, though decreasing, HbA1c levels over time. They had the worst cognitive performance, particularly in overall cognition (p<0.02) and semantic categorization (p<0.01), followed by that of subjects whose HbA1c at entry into the DR was relatively high (7.2%, 7.8%) and increased over time. Subjects with stable HbA1c over time had the lowest HbA1c levels at entry (6.0%, 6.8%) and performed best in cognitive tests.

Conclusion

Glycemic control trajectories, which better reflect chronicity of T2D than a single HbA1c measurement, predict cognitive performance. A trajectory of stable HbA1c levels over time is associated with better cognitive function.

The negative effects of obesity and poor glycemic control on cognitive function: a proposed model for possible mechanisms

Obesity has reached epidemic proportions and is a contributor to many adverse health outcomes, including increased risk for dementia and adverse structural and functional brain changes. Milder forms of cognitive impairment in multiple domains can also be found in obese individuals of all ages that are believed to stem from brain abnormalities long prior to onset of neurologic conditions such as dementia. However, the mechanisms for adverse brain changes and subsequent cognitive dysfunction in obesity are complex and poorly understood. This paper proposes a possible etiologic model for obesity associated cognitive impairment with emphasis on the role of poor glycemic control and conditions like type 2 diabetes mellitus. Clinical implications associated with treatment of obesity in persons with cognitive deficits in addition to the cognitive promoting effects of weight loss surgery are also discussed.

Diabetes. Cognitive decline and T2DM--a disconnect in the evidence?

Type 2 diabetes mellitus is associated with an increased risk of cognitive decline and dementia. Observational data suggest that hyperglycaemia, hypertension and dyslipidaemia might be involved in the causal pathway underlying this link, but data from the ACCORD MIND investigators challenge these findings. Why are the findings of observational and intervention studies so disconnected?

Diabetes and the brain: issues and unmet needs

Diabetes mellitus (DM) is associated with an increased risk of mild cognitive impairment, dementia and stroke. The association between DM and dementia appears to be stronger for vascular cognitive impairment than for Alzheimer’s disease, suggesting cerebrovascular disease may be an important factor in cognitive impairment in DM. Although the exact mechanisms by which DM affects the brain remain unclear, changes to brain vasculature, disturbances of cerebral insulin signaling, insulin resistance, glucose toxicity, oxidative stress, accumulation of advanced glycation end products, hypoglycemic episodes, and alterations in amyloid metabolism may all be involved. Cognitive impairment and dementia associated with DM may also be mediated via vascular risk factors, in particular brain ischemia, the occurrence of which can have an additive or synergistic effect with concomitant neurodegenerative processes. To date, no drug has been approved for the treatment of vascular dementia and there are no specific pharmacological treatments for preventing or reducing cognitive decline in patients with DM. Most focus has been on tighter management of vascular risk factors, although evidence of reduced cognitive decline through reducing blood pressure, lipid-lowering or tighter glycemic control is inconclusive. Tailored, multimodal therapies may be required to reduce the risk of cognitive dysfunction and decline in patients with DM. The use of pleiotropic drugs with multimodal mechanisms of action (e.g., cerebrolysin, Actovegin) may have a role in the treatment of cognitive dysfunction and their use may warrant further investigation in diabetic populations.