Hypoglycaemia-induced changes in regional brain volume and memory function

Understanding Alzheimer's Disease and its Metal Chelation Therapeutics: A Narrative Review

The neurodegenerative disorders are age-related illnesses that cause the morphology or activity of neurons to deteriorate over time. Alzheimer's disease is the most frequent neurodegenerative illness in the long run. The rate of advancement might vary, even though it is a progressive neurological illness. Various explanations have been proposed, however the true etiology of Alzheimer's disease remains unclear. Most pharmacological interventions are based on the cholinergic theory, that is earliest idea. In accordance with the amyloid hypothesis, the buildup of beta-amyloid in brain regions is the primitive cause of illness. There is no proof that any one strategy is useful in avoiding Alzheimer's disease, though some epidemiological studies have suggested links within various modifiable variables, such as cardiovascular risk, diet and so on. Different metals like zinc, iron, and copper are naturally present in our bodies. In metal chelation therapy drugs are used to jam the metal ions from combining with other molecules in the body. Clioquinol is one of the metal chelation drugs used by researchers. Research on metal chelation is still ongoing. In the present review, we go over the latest developments in prevalence, incidence, etiology, or pathophysiology of our understanding of Alzheimer's disease. Additionally, a brief discussion on the development of therapeutic chelating agents and their viability as Alzheimer's disease medication candidates is presented. We also assess the effect of clioquinol as a potential metal chelator.

Intensive glycemic control and macrovascular, microvascular, hypoglycemia complications and mortality in older (age ≥60years) or frail adults with type 2 diabetes: a systematic review and meta-analysis from randomized controlled trial and observation studies

INTRODUCTION

Guidelines for type 2 diabetes (T2D) recommend individualized HbA1c targets to take into account patient age or frailty. We synthesized evidence from randomized controlled trials and observational studies for intensive glycemic control (HbA1c target ≤58 mmol/mol) versus standard care, in elderly (age ≥60 years) or frail adults with T2D.

METHODS

Searches were performed utilizing recognized terms for T2D, frailty, older age, and HbA1c control and outcomes of interest. Meta-analysis was performed where possible. Primary outcomes included all-cause mortality, severe hypoglycemia, and hospital admission rates. Vascular complications, cognitive decline, and falls/fractures were secondary outcomes.

RESULTS

7,528 studies were identified of which 15 different clinical studies were selected. No difference was noted in all-cause mortality with intensive control (pooled hazard ratio 0.96, 95% confidence interval 0.90-1.03), but risk of severe hypoglycemia increased (2.45, 2.22-2.72). Intensive control was associated reductions in microvascular (0.73, 0.68-0.79) and macrovascular complications (0.84, 0.79-0.89). Outcome data for risk of hospitalization, cognition, and falls/fractures were limited.

CONCLUSION

Intensive glycemic control was associated with reduced rates of complications but increased severe hypoglycemia. Significant heterogeneity exists and the impact of different drug regimens is unclear. Caution is needed when setting glycemic targets in elderly or frail individuals.

Defective involuntary attention to novelty in type 1 diabetes and impaired awareness of hypoglycaemia

AIM

To determine if there are differences in terms of neurophysiology and neurocognitive functioning in a group of type 1 diabetes (T1D) patients regarding hypoglycaemia awareness.

METHODS

27 patients with T1D were classified according to Clarke score as having impaired awareness of hypoglycaemia (IAH; n = 11) or normal awareness to hypoglycaemia (NAH; n = 16). We measured several clinical and sociodemographic variables and cognitive performance using neuropsychological tests. Electroencephalography was assessed during an auditory oddball task. We compared the groups in terms of clinical/sociodemographic variables as well as two event-related brain potentials (ERPs): The P3a which is associated with automatic orientation of attention to novelty, and the P3b which is associated with target detection and processing.

RESULTS

The IAH group performed significantly worse on the Trail Making Test part A (TMT-A) (p = 0.05). Compared to the NAH group, P3a and P3b amplitudes in the frontal-central sites were significantly lower in the IAH group (p < 0.05). The P3a was strongly associated with worse performance on the TMT-A in the IAH group (r = 0.540; p < 0.005) CONCLUSION: IAH is accompanied by decreased neurophysiological activity in ERPs associated with information processing and with the automatic orientation of attention to novelty and environmental changes. These findings suggest a possible framework to better understand the cognitive origin of IAH in this patient population.

Diagnosis and management of pediatric type 1 diabetes mellitus

Background: In contrast to type 2 diabetes, type 1 diabetes mellitus (T1DM) requires insulin treatment to control blood glucose. As the incidence and prevalence of T1DM have steadily increased; therefore, T1DM is increasingly being diagnosed not only in children and adolescents, but also in adults. Therefore, the importance of accurate diagnosis and optimal management of T1DM is being recognized in clinical practice.Current Concepts: T1DM is caused by insulin deficiency, following the destruction of insulin-producing pancreatic β-cells. Diagnosis of diabetes is based on the following criteria: fasting blood glucose levels ≥126 mg/dL, random blood glucose levels ≥200 mg/dL accompanied by symptoms of hyperglycemia, an abnormal 2-hour oral glucose tolerance test, or glycated hemoglobin ≥6.5%. Accurate diagnosis of T1DM based on patients’ clinical characteristics, serum C-peptide levels, and detection of autoantibodies against β-cell autoantigens is important for optimum care and to avoid complications. A target glycated hemoglobin level is recommended in children, adolescents, and young adults with access to comprehensive care. The availability of insulin analogues and mechanical technologies (insulin pumps and continuous glucose monitors) has improved the management of T1DM, and these are useful for the prevention of microvascular complications. Screening for microvascular complications should commence at puberty or 5 years after diagnosis of T1DM.Discussion and Conclusion: Effective cooperation and coordination between patient, parents, and healthcare providers are necessary to achieve a successful transition from pediatric to adult care in patients with T1DM. Diabetic management for T1DM should be individualized based on patients’ lifestyle, as well as psychosocial, and medical circumstances.

Structural Gray and White Matter Differences in Patients With Type 1 Diabetes and Impaired Awareness of Hypoglycemia

CONTEXT

Type 1 diabetes (T1D) is associated with an increased risk of cognitive decline, where severe hypoglycemia (SH) and impaired awareness of hypoglycemia (IAH) may play a role. While there is evidence of a possible association between IAH and brain damage, the potential brain changes remain poorly characterized by magnetic resonance imaging (MRI).

OBJECTIVE

To investigate whether there are structural brain differences in a group of T1D patients with IAH compared with normal awareness of hypoglycemia (NAH).

DESIGN

General practice, population-based, cross-sectional study (July 2018 to July 2019).

SETTING

Endocrinology Department, Hospital Santa Creu i Sant Pau.

PARTICIPANTS

A total of 40 T1D patients (20 each with IAH and NAH) matched for age, sex, T1D duration, and education level.

MAIN OUTCOME MEASURES

Using different neuroimaging techniques, we compared whole-brain gray matter (GM) and white matter (WM) differences. We used voxel-based morphometry and cortical surface area analysis methods to assess GM differences, and fractional anisotropy (FA) to assess WM differences.

RESULTS

Compared with patients with T1D-NAH, patients with T1D-IAH had reduced GM volumes and cortical surface areas, especially in frontal and parietal regions (P < 0.05 corrected), and also showed reduced FA values in major WM tracts. The observed MRI differences correlated with both SH frequency and IAH severity.

CONCLUSIONS

MRI for patients with T1D show that IAH is associated with brain changes involving both GM and WM. Further research is needed to elucidate whether the observed differences are a consequence of increased SH episode frequency and increased IAH severity.

Identifying risk effectors involved in neonatal hypoglycemia occurrence

Hypoglycemia is a common metabolic condition in neonatal period, but severe and persistent hypoglycemia can cause neurological damage and brain injury. The aim of the present study was to analyze the risk factors of neonatal hypoglycemia in clinic. A total of 135 neonatal hypoglycemia infants and 135 healthy infants were included in the present study. The differences in birth weight between neonatal hypoglycemia group and healthy control group were analyzed via t test. The associations between neonatal blood sugar level and relevant characteristic factors were explored using χ² test. Binary logistic regression analysis was used to analyze risk factors related to the incidence of neonatal hypoglycemia. The results showed that the average birth weight was matched in neonatal hypoglycemia group and healthy control group. Neonatal blood sugar level of the infants was significantly associated with born term, birth weight, feed, gestational diabetes mellitus (GDM) and hypothermia (all P<0.05). Besides, logistic regression analysis showed that babies’ born term (odds ratio (OR) = 2.715, 95% confidence interval (95% CI): 1.311–5.625), birth weight (OR = 1.910, 95% CI: 1.234–2.955), improper feeding (OR = 3.165, 95% CI: 1.295–7.736) and mother’s GDM (OR = 2.184, 95% CI: 1.153–4.134) were high risk factors for neonatal hypoglycemia. The incidence of hypoglycemia in infants was significantly associated with various clinical factors. And monitoring these risk factors is one of important measures to reduce long-term neurological damage caused by neonatal hypoglycemia.

Early detection of cognitive impairment in patients with insulinoma

PURPOSE

Long-standing hypoglycemia can cause cognitive impairment, and whether recurrent severe hypoglycemia impacts cognitive function in patients with insulinoma has not been studied. This study focused on exploring the cognitive function in patients with insulinoma.

METHODS

A prospective study was conducted to assess cognitive function in patients with insulinoma by administering the Montreal Cognitive Assessment (MoCA) questionnaire between January 2016 and July 2017, and patients with cognitive impairment were followed up to undergo the MoCA test 1 year after surgery. The MoCA scores after surgery were compared with the scores before surgery, and the associations between cognitive impairment and relevant factors were further evaluated by multiple linear regression analysis.

RESULTS

Eighteen out of thirty-four patients (53%) with insulinoma were screened positive for cognitive impairment as defined by a MoCA score <26. Performance in certain cognitive domains, including visuospatial and executive functions, delayed memory, attention, language, and abstraction, was significantly worse in patients with cognitive impairment. Multivariate analysis indicated that MoCA scores correlated significantly with tumor grade and years of education. Eight patients with cognitive impairment were lost to follow-up. The remaining ten patients with cognitive impairment showed improvements 1 year postoperatively, and seven patients recovered to normal cognitive function.

CONCLUSIONS

Cognitive impairment was found in patients with insulinoma and was reversible in some patients 1 year after surgery. More studies are needed to explore the underlying mechanisms of the existence and reversibility of cognitive impairment in patients with insulinoma.

Recurrent moderate hypoglycemia exacerbates oxidative damage and neuronal death leading to cognitive dysfunction after the hypoglycemic coma

Moderate recurrent hypoglycemia (RH) is frequent in Type 1 diabetes mellitus (TIDM) patients who are under intensive insulin therapy increasing the risk for severe hypoglycemia (SH). The consequences of RH are not well understood and its repercussions on neuronal damage and cognitive function after a subsequent episode of SH have been poorly investigated. In the current study, we have addressed this question and observed that previous RH during seven consecutive days exacerbated oxidative damage and neuronal death induced by a subsequent episode of SH accompanied by a short period of coma, in the parietal cortex, the striatum and mainly in the hippocampus. These changes correlated with a severe decrease in reduced glutathione content (GSH), and a significant spatial and contextual memory deficit. Administration of the antioxidant, N-acetyl-L-cysteine, (NAC) reduced neuronal death and prevented cognitive impairment. These results demonstrate that previous RH enhances brain vulnerability to acute hypoglycemia and suggests that this effect is mediated by the decline in the antioxidant defense and oxidative damage. The present results highlight the importance of an adequate control of moderate hypoglycemic episodes in TIDM.

The db mutation improves memory in younger mice in a model of Alzheimer's disease

Alzheimer's disease (AD) is the most common age-related neurodegenerative disease, while obesity is a major global public health problem associated with the metabolic disorder type 2 diabetes mellitus (T2DM). Chronic obesity and T2DM have been identified as invariant risk factors for dementia and late-onset AD, while their impacts on the occurrence and development of AD remain unclear. As shown in our previous study, the diabetic mutation (db, Lepr^db/db) induces mixed or vascular dementia in mature to middle-aged APP^ΔNL/ΔNL x PS1^P264L/P264L knock-in mice (db/AD). In the present study, the impacts of the db mutation on young AD mice at 10 weeks of age were evaluated. The db mutation not only conferred young AD mice with severe obesity, impaired glucose regulation and activated mammalian target of rapamycin (mTOR) signaling pathway in the mouse cortex, but lead to a surprising improvement in memory. At this young age, mice also had decreased cerebral Aβ content, which we have not observed at older ages. This was unlikely to be related to altered Aβ synthesis, as both β- and γ-secretase were unchanged. The db mutation also reduced the cortical IL-1β mRNA level and IBA1 protein level in young AD mice, with no significant effect on the activation of microglia and astrocytes. We conclude that the db mutation could transitorily improve the memory of young AD mice, a finding that may be partially explained by the relatively improved glucose homeostasis in the brains of db/AD mice compared to their counterpart AD mice, suggesting that glucose regulation could be a strategy for prevention and treatment of neurodegenerative diseases like AD.

Hypoglycemia and cognitive function in diabetic patients

AIMS

Hypoglycemia can be considered the most common complication of Diabetes Mellitus treatment. So far, controversial studies have been carried out to examine the impacts of hypoglycemia on the cognitive function.

METHODS

This study was conducted as case-control. The case group was 35 patients with Diabetes Mellitus Types I or II hospitalized in Imam Hussein Hospital, Tehran, Iran, who have experienced hypoglycemic attacks (glucose level below 70 mg/dl). The control group consisted of diabetic patients hospitalized in hospital, but they had no history of hypoglycemia. As the blood glucose level became in normal range and the patients' Mental status became stable, the brain cognitive function was examined using Mini-Mental State test.

RESULTS

The mean age of the subjects in the case and control groups was 56.77, 53.73 years old, respectively. The mean cognitive score in the control and hypoglycemic groups was 29.09 and 25.29, respectively. The mean MMSE cognitive score was significantly diminished in the hypoglycemic group (p < 0.001).

CONCLUSIONS

This study indicated that incidence of hypoglycemia in diabetic patients is associated with cognitive disorders. Further, there is a linear association between cognitive disorders and hypoglycemia, age and diabetes mellitus complication.

Effect of recurrent severe hypoglycemia on cognitive performance in adult patients with diabetes: A meta-analysis

The purpose of this study was to investigate the existence and extent of cognitive impairment in adult diabetes mellitus (DM) patients with episodes of recurrent severe hypoglycemia, by using meta-analysis to synthesize data across studies. PubMed, EMBASE and Cochrane library search engines were used to identify studies on cognitive performance in DM patients with recurrent severe hypoglycemia. Random-effects meta-analysis was performed on seven eligible studies using an inverse-variance method. Effect sizes, which are the standardized differences between the experimental group and the control group, were calculated. Of the 853 studies, 7 studies met the inclusion criteria. Compared with control subjects, the adult DM patients with episodes of recurrent severe hypoglycemia demonstrated a significantly lowered performance on memory in both types of DM patients, and poor performance of processing speed in type 2 DM patients. There was no significant difference between adult DM patients with and those without severe hypoglycemia in other cognitive domains such as general intelligence, executive function, processing speed and psychomotor efficiency. Our results seem to confirm the hypothesis that cognitive dysfunction is characterized by worse memory and processing speed in adult DM patients with a history of recurrent severe hypoglycemia, whereas general intelligence, executive function, and psychomotor efficiency are spared.

Cognitive deficits associated with impaired awareness of hypoglycaemia in type 1 diabetes

AIMS/HYPOTHESIS

The aim of this study was to compare cognitive function in adults with type 1 diabetes who have impaired awareness of hypoglycaemia with those who have normal awareness of hypoglycaemia. A putative association was sought between cognitive test scores and a history of severe hypoglycaemia.

METHODS

A total of 68 adults with type 1 diabetes were included: 33 had impaired and 35 had normal awareness of hypoglycaemia, as confirmed by formal testing. The groups were matched for age, sex and diabetes duration. Cognitive tests of verbal memory, object-location memory, pattern separation, executive function, working memory and processing speed were administered.

RESULTS

Participants with impaired awareness of hypoglycaemia scored significantly lower on the verbal and object-location memory tests and on the pattern separation test (Cohen's d -0.86 to -0.55 [95% CI -1.39, -0.05]). Participants with impaired awareness of hypoglycaemia had reduced planning ability task scores, although the difference was not statistically significant (Cohen's d 0.57 [95% CI 0, 1.14]). Frequency of exposure to severe hypoglycaemia correlated with the number of cognitive tests that had not been performed according to instructions.

CONCLUSIONS/INTERPRETATION

Impaired awareness of hypoglycaemia was associated with diminished learning, memory and pattern separation. These cognitive tasks all depend on the hippocampus, which is vulnerable to neuroglycopenia. The findings suggest that hypoglycaemia contributes to the observed correlation between impaired awareness of hypoglycaemia and impaired cognition.

Diabetes mellitus and white matter hyperintensity

White matter hyperintensity (WMH) is a brain lesion detected as a high-intensity area in magnetic resonance imaging T2 and fluid-attenuated inversion recovery images, and it has been suggested that WMH reflects damage to small vessels in periventricular and subcortical areas. Although WMH has been linked to the incidence of stroke, more recently it has been clarified that WMH is also associated with progression of cognitive decline and functional disability, which are components of so-called geriatric syndrome. In addition to hypertension, which is the classical risk factor for WMH, evidence has been accumulating to suggest that diabetes mellitus could also be associated with WMH progression, and some studies have shown that WMH severity is correlated with cognitive decline in patients with diabetes. The factors that accelerate WMH formation in elderly patients with diabetes remain poorly defined. It is considered that insulin resistance is an exacerbating factor, but the effects of hypertension, dyslipidemia or other vascular risk factors have yet be clarified, and further studies are required.

A Case of Transient Global Amnesia: A Review and How It May Shed Further Insight into the Neurobiology of Delusions

Transient global amnesia is a clinical syndrome characterized by the sudden onset of anterograde amnesia, accompanied by repetitive questioning, sometimes with a retrograde component, lasting up to 24 hours, without compromise of other neurologic function. Neuroimaging after an acutetransient global amnesia event often shows transient perturbation of specific hippocampal circuits that are involved in memory processing. Critical clinical distinctions, such as between transient global amnesia and other forms of transient amnesic episodes, as well as important clues to the underlying pathophysiologies are herein reviewed. Finally, we discuss the role of hippocampal insufficiency in the neurobiology of delusions.

Technical feasibility and safety profile of laparoscopic diverted sleeve gastrectomy with ileal transposition (DSIT)

Background

In this study, we specifically aimed to analyze the technical and safety aspects of laparoscopic diverted sleeve gastrectomy with ileal transposition (DSIT) in patients with type 2 diabetes (T2DM).

Methods

A total of 360 patients with type 2 diabetes who underwent a DSIT procedure within the past 2-year period (2011–2013) were analyzed. Operation time, length of hospital stay, perioperative and postoperative complications, and mortality were recorded and analyzed.

Results

The participants consisted of 229 males (63.6 %) and 131 females (36.4 %). Mean duration of follow-up was 12.4 months (range, 6–31). One early and two late mortalities occurred. Early mortality was due to an anastomotic leak, and late mortalities were related to myocardial infarction and a traffic accident. Leakage and bleeding were the most common surgical complications. The total number of surgical complications was 22 (6.1 %). Of those, 19 occurred within the first month (early) and 3 occurred after the first month (late). Among early complications, seven (1.94 %) required re-operation, two patients (0.55 %) required endoscopic treatment, and the remaining ten were managed conservatively. Late surgical complications (sleeve angulation) were noted in three patients (0.83) and were treated by endoscopic stents. Surgery-related non-surgical complications occurred in 19 cases (5.2 %), and neurological complications were noted in 11 patients (3.05 %). Additional surgical intervention was required in 26 patients (7.22 %). Of those, 15 (4.16 %) required cholecystectomy.

Conclusions

Our data demonstrate that DSIT is a technically feasible operation and can be safely performed in type 2 diabetic patients with acceptable complication and mortality rates.

Acute hypoglycemia results in reduced cortical neuronal injury in the developing IUGR rat

BACKGROUND

Hypoglycemia (HG) is common in intrauterine growth restricted (IUGR) neonates. In normally grown (NG) neonatal rats, acute HG causes neuronal injury in the brain; the cerebral cortex is more vulnerable than the hippocampus (HPC). We hypothesized that the IUGR brain is less vulnerable to HG-induced injury while preserving regional variation in vulnerability.

METHODS

We induced IUGR via bilateral uterine artery ligation on gestational day 19 (term 22 d) rats. On postnatal day 14, insulin-induced HG of equivalent severity and duration (blood glucose < 40 mg/dl for 240 min) was produced in IUGR and NG (IUGR/HG and NG/HG). Neuronal injury in the cortex and HPC was quantified 6-72 h later using Fluoro-Jade B (FJB) histochemistry. The mRNA expression of monocarboxylate transporters, MCT1 and MCT2, and glucose transporters, GLUT1 and GLUT3, was determined using quantitative PCR.

RESULTS

There were fewer FJB-positive (FJB+) cells in the cortex of IUGR/HG; no difference was observed in FJB+ cells in HPC. Core body temperature was lower in IUGR/HG compared with NG/HG. MCT2 expression was increased in the IUGR cortex.

CONCLUSION

HG-induced neuronal injury is decreased in the cortex of the developing IUGR brain. Adaptations including systemic hypothermia and enhanced delivery of alternative substrates via MCT2 might protect against HG-induced neuronal injury in IUGR.

Atrophic Patterns of the Frontal-Subcortical Circuits in Patients with Mild Cognitive Impairment and Alzheimer's Disease

Atrophy of the cortical thickness and gray matter volume are regarded as sensitive markers for the early clinical diagnosis of Alzheimer’s disease (AD). This study aimed to investigate differences in atrophy patterns in the frontal-subcortical circuits between MCI and AD, assess whether these differences were essential for the pathologic basis of cognitive impairment. A total of 131 individuals were recruited, including 45 with cognitively normal controls (CN), 46 with MCI, and 40 with AD. FreeSurfer software was used to perform volumetric measurements of the frontal-subcortical circuits from 3.0T magnetic resonance (MR) scans. Data revealed that both MCI and AD subjects had a thinner cortex in the left caudal middle frontal gyrus and the left lateral orbitofrontal gyrus compared with CN individuals. The left lateral orbitofrontal gyrus was also thinner in AD compared with MCI patients. There were no statistically significant differences in the cortical mean curvature among the three groups. Both MCI and AD subjects exhibited smaller bilateral hippocampus volumes compared with CN individuals. The volumes of the bilateral hippocampus and the right putamen were also smaller in AD compared with MCI patients. Logistic regression analyses revealed that the left lateral orbitofrontal gyrus and bilateral hippocampus were risk factors for cognitive impairment. These current results suggest that atrophy was heterogeneous in subregions of the frontal-subcortical circuits in MCI and AD patients. Among these subregions, the reduced thickness of the left lateral orbitofrontal and the smaller volume of the bilateral hippocampus seemed to be markers for predicting cognitive impairment.

Non-Alzheimer's disease-related memory impairment and dementia

Although Alzheimer's disease (AD) is a common cause of memory impairment and dementia in the elderly disturbed memory function is a widespread subjective and/or objective symptom in a variety of medical conditions. The early detection and correct distinction of AD from non-AD memory impairment is critically important to detect possibly treatable and reversible underlying causes. In the context of clinical research, it is crucial to correctly distinguish between AD or non-AD memory impairment in order to build homogenous study populations for the assessment of new therapeutic possibilities. The distinction of AD from non-AD memory impairment may be difficult, especially in mildly affected patients, due to an overlap of clinical symptoms and biomarker alterations between AD and certain non-AD conditions. This review aims to describe recent aspects of the differential diagnosis of AD and non-AD related memory impairment and how these may be considered in the presence of memory deficits.

Hippocampal Volume in Type 1 Diabetes

The hippocampus plays an important role in human memory and is known to be vulnerable to extreme hyperglycaemia and hypoglycaemia in animal models of type 1 diabetes. Within humans with type 1 diabetes, exposure to glycaemic extremes has been associated with alterations in hippocampal structure and in memory function, but results are inconsistent. It has been hypothesised that the effects of hypoglycaemia and hyperglycaemia on the hippocampus may depend on when during neurodevelopment these extremes occur, possibly explaining some of these inconsistencies. However, data addressing this concept are limited. We review here the existing literature on this complex topic and suggest future avenues of required research.

Neuronal damage and cognitive impairment associated with hypoglycemia: An integrated view

The aim of the present review is to offer a current perspective about the consequences of hypoglycemia and its impact on the diabetic disorder due to the increasing incidence of diabetes around the world. The main consequence of insulin treatment in type 1 diabetic patients is the occurrence of repetitive periods of hypoglycemia and even episodes of severe hypoglycemia leading to coma. In the latter, selective neuronal death is observed in brain vulnerable regions both in humans and animal models, such as the cortex and the hippocampus. Cognitive damage subsequent to hypoglycemic coma has been associated with neuronal death in the hippocampus. The mechanisms implicated in selective damage are not completely understood but many factors have been identified including excitotoxicity, oxidative stress, zinc release, PARP-1 activation and mitochondrial dysfunction. Importantly, the diabetic condition aggravates neuronal damage and cognitive failure induced by hypoglycemia. In the absence of coma prolonged and severe hypoglycemia leads to increased oxidative stress and discrete neuronal death mainly in the cerebral cortex. The mechanisms responsible for cell damage in this condition are still unknown. Recurrent moderate hypoglycemia is far more common in diabetic patients than severe hypoglycemia and currently important efforts are being done in order to elucidate the relationship between cognitive deficits and recurrent hypoglycemia in diabetics. Human studies suggest impaired performance mainly in memory and attention tasks in healthy and diabetic individuals under the hypoglycemic condition. Only scarce neuronal death has been observed under moderate repetitive hypoglycemia but studies suggest that impaired hippocampal synaptic function might be one of the causes of cognitive failure. Recent studies have also implicated altered mitochondrial function and mitochondrial oxidative stress.