Regional brain volume differences associated with hyperglycemia and severe hypoglycemia in youth with type 1 diabetes

The interface of child mental health and juvenile diabetes mellitus

Diabetes mellitus is a common childhood illness, and its management is often complicated by mental health challenges. Psychiatric comorbidities are common, including anxiety, depression, and eating disorders. The illness can profoundly affect the developing brain and family functioning and have lifelong consequences. The child mental health provider can provide valuable assistance to support the child and family and assessment and treatment of comorbid mental health problems and to promote positive family functioning and normal developmental progress.

Diabetes as a chronic metabolic stressor: causes, consequences and clinical complications

Diabetes mellitus is an endocrine disorder resulting from inadequate insulin release and/or reduced insulin sensitivity. The complications of diabetes are well characterized in peripheral tissues, but there is a growing appreciation that the complications of diabetes extend to the central nervous system (CNS). One of the potential neurological complications of diabetes is cognitive deficits. Interestingly, the structural, electrophysiological, neurochemical and anatomical underpinnings responsible for cognitive deficits in diabetes are strikingly similar to those observed in animals subjected to chronic stress, as well as in patients with stress-related psychiatric illnesses such as major depressive disorder. Since diabetes is a chronic metabolic stressor, this has led to the suggestion that common mechanistic mediators are responsible for neuroplasticity deficits in both diabetes and depression. Moreover, these common mechanistic mediators may be responsible for the increase in the risk of depressive illness in diabetes patients. In view of these observations, the aims of this review are (1) to describe the neuroplasticity deficits observed in diabetic rodents and patients; (2) to summarize the similarities in the clinical and preclinical studies of depression and diabetes; and (3) to highlight the diabetes-induced neuroplasticity deficits in those brain regions that have been implicated as important pathological centers in depressive illness, namely, the hippocampus, the amygdala and the prefrontal cortex.

Variables associated with severe hypoglycemia in children and adolescents with type 1 diabetes: a population-based study

OBJECTIVE

Hypoglycemia remains a central problem in the management of type 1 diabetes mellitus (T1DM) and limits the achievement of good or normal glycemic control. The Diabetes Control and Complication Trial showed that intensive treatment of T1DM increased the risk of severe hypoglycemia (SH) when compared to conventional therapy. The aim of our study was to determine the incidence of SH and associated variables in a population of children and adolescents with T1DM.

RESEARCH DESIGN AND METHODS

We performed a 7.5-yr prospective study enrolling 195 patients aged 13.9 ± 6.6 yr. The study was carried out by referring to the T1DM population-based register in the Abruzzo region of Italy. The incidence of SH, defined as blood glucose levels <50 mg/dL (<2.77 mmol/L) associated with altered states of consciousness (including confusional state, seizures, and coma) was recorded. Glycated hemoglobin (HbA1c) percentage, insulin dose, insulin regimen, time since diagnosis, and age at onset were also recorded.

RESULTS

One hundred and thirty-three severe hypoglycemic events occurred during the study period; the overall incidence was 9.4 episodes per 100 patient-years. Significant predictors of hypoglycemia were diabetes duration >10 yr (p = 0.01), basal/bolus insulin ratio (ratio of daily basal insulin units to daily bolus insulin units) >0.8 (p = 0.01). No relationship was found between hypoglycemic episodes and HbA1c levels, daily insulin requirements, or insulin regimen.

CONCLUSIONS

In these patients, a relatively low incidence of SH was recorded, without pronounced association with lower HbA1c or multiple daily injection insulin therapy. SH seems to be mainly related to management of diabetes. We believe that the main path to SH prevention is through patient and family education in the management of T1DM.

Encephalopathies: the emerging diabetic complications

Diabetic encephalopathies are now accepted complications of diabetes. They appear to differ in type 1 and type 2 diabetes as to underlying mechanisms and the nature of resulting cognitive deficits. The increased incidence of Alzheimer's disease in type 2 diabetes is associated with insulin resistance, hyperinsulinemia and hyperglycemia, and commonly accompanying attributes such as hypercholesterolemia, hypertension and obesity. The relevance of these disorders as to the emergence of dementia and Alzheimer's disease is discussed based on epidemiological studies. The pathobiology of accumulation of β-amyloid and tau the hallmarks of Alzheimer's disease are discussed based on experimental data. Type 1 diabetic encephalopathy is likely to increase as a result of the global increase in the incidence of type 1 diabetes and its occurrence in increasingly younger patients. Alzheimer-like changes and dementia are not prominently increased in type 1 diabetes. Instead, the type 1 diabetic encephalopathy involves learning abilities, intelligence development and memory retrieval resulting in impaired school and professional performances. The major underlying component here appears to be insulin deficiency with downstream effects on the expression of neurotrophic factors, neurotransmitters, oxidative and apoptotic stressors resulting in defects in neuronal integrity, connectivity and loss commonly occurring in the still developing brain. Recent experimental data emphasize the role of impaired central insulin action and provide information as to potential therapies. Therefore, the underlying mechanisms resulting in diabetic encephalopathies are complex and appear to differ between the two types of diabetes. Major headway has been made in our understanding of their pathobiology; however, many questions remain to be clarified. In view of the increasing incidence of both type 1 and type 2 diabetes, intensified investigations are called for to expand our understanding of these complications and to find therapeutic means by which these disastrous consequences can be prevented and modified.

Preliminary evidence for brain complications in obese adolescents with type 2 diabetes mellitus

AIMS/HYPOTHESIS

Central nervous system abnormalities, including cognitive and brain impairments, have been documented in adults with type 2 diabetes who also have multiple co-morbid disorders that could contribute to these observations. Assessing adolescents with type 2 diabetes will allow the evaluation of whether diabetes per se may adversely affect brain function and structure years before clinically significant vascular disease develops.

METHODS

Eighteen obese adolescents with type 2 diabetes and 18 obese controls without evidence of marked insulin resistance, matched on age, sex, school grade, ethnicity, socioeconomic status, body mass index and waist circumference, completed MRI and neuropsychological evaluations.

RESULTS

Adolescents with type 2 diabetes performed consistently worse in all cognitive domains assessed, with the difference reaching statistical significance for estimated intellectual functioning, verbal memory and psychomotor efficiency. There were statistical trends for executive function, reading and spelling. MRI-based automated brain structural analyses revealed both reduced white matter volume and enlarged cerebrospinal fluid space in the whole brain and the frontal lobe in particular, but there was no obvious grey matter volume reduction. In addition, assessments using diffusion tensor imaging revealed reduced white and grey matter microstructural integrity.

CONCLUSIONS/INTERPRETATION

This is the first report documenting possible brain abnormalities among obese adolescents with type 2 diabetes relative to obese adolescent controls. These abnormalities are not likely to result from education or socioeconomic bias and may result from a combination of subtle vascular changes, glucose and lipid metabolism abnormalities and subtle differences in adiposity in the absence of clinically significant vascular disease. Future efforts are needed to elucidate the underlying pathophysiological mechanisms.

Cerebral and cerebellar volume loss in children and adolescents with systemic lupus erythematosus: a review of clinically acquired brain magnetic resonance imaging

OBJECTIVE

Cerebral atrophy is a prominent feature in adults with systemic lupus erythematosus (SLE). We assessed cerebral and cerebellar volume loss on clinically acquired brain magnetic resonance imaging (MRI) scans of children and adolescents with SLE.

METHODS

We abstracted information on disease course for patients who underwent clinical brain MRI during the period 2002-2008. We completed qualitative assessments of volume loss and measured corpus callosum thickness and ventricular enlargement for patients with lupus and controls.

RESULTS

Forty-nine children underwent brain MRI during the review period due to clinical indications. The lupus cohort was predominantly female and ethnically diverse. Mean age at imaging was 15.3 +/- 2.6 years and mean disease duration was 30.6 +/- 33.3 months. Findings suggestive of cerebral and cerebellar volume loss were seen respectively in 89.8% and 91.8% of lupus patients. Cerebral volume loss was moderate or severe in 26.5% of children. Cerebellar volume loss was moderate in 20.4% of these patients. Linear measurement means reflected corpus callosum thinning and ventricular enlargement in lupus patients. Volume loss was observed in newly diagnosed patients prior to corticosteroid use. Disease duration and corticosteroid use did not predict the severity of volume loss. There were statistically significant differences in linear imaging measurements comparing lupus patients to 14 similar-age controls.

CONCLUSION

Regional volume loss was observed in most adolescents with lupus undergoing clinical brain MRI scans. As in other pediatric conditions with inflammatory or vascular etiologies, these findings may be reflecting disease-associated neuronal loss and not solely the effects of corticosteroid.

The interface of child mental health and juvenile diabetes mellitus

Diabetes mellitus is a common childhood illness, and its management is often complicated by mental health challenges. Psychiatric comorbidities are common, including anxiety, depression, and eating disorders. The illness can profoundly affect the developing brain and family functioning and have lifelong consequences. The child mental health provider can provide valuable assistance to support the child and family and assessment and treatment of comorbid mental health problems and to promote positive family functioning and normal developmental progress.

Recurrent moderate hypoglycemia ameliorates brain damage and cognitive dysfunction induced by severe hypoglycemia

OBJECTIVE

Although intensive glycemic control achieved with insulin therapy increases the incidence of both moderate and severe hypoglycemia, clinical reports of cognitive impairment due to severe hypoglycemia have been highly variable. It was hypothesized that recurrent moderate hypoglycemia preconditions the brain and protects against damage caused by severe hypoglycemia.

RESEARCH DESIGN AND METHODS

Nine-week-old male Sprague-Dawley rats were subjected to either 3 consecutive days of recurrent moderate (25-40 mg/dl) hypoglycemia (RH) or saline injections. On the fourth day, rats were subjected to a hyperinsulinemic (0.2 units x kg(-1) x min(-1)) severe hypoglycemic ( approximately 11 mg/dl) clamp for 60 or 90 min. Neuronal damage was subsequently assessed by hematoxylin-eosin and Fluoro-Jade B staining. The functional significance of severe hypoglycemia-induced brain damage was evaluated by motor and cognitive testing.

RESULTS

Severe hypoglycemia induced brain damage and striking deficits in spatial learning and memory. Rats subjected to recurrent moderate hypoglycemia had 62-74% less brain cell death and were protected from most of these cognitive disturbances.

CONCLUSIONS

Antecedent recurrent moderate hypoglycemia preconditioned the brain and markedly limited both the extent of severe hypoglycemia-induced neuronal damage and associated cognitive impairment. In conclusion, changes brought about by recurrent moderate hypoglycemia can be viewed, paradoxically, as providing a beneficial adaptive response in that there is mitigation against severe hypoglycemia-induced brain damage and cognitive dysfunction.

Reliability and validity of MRI-based automated volumetry software relative to auto-assisted manual measurement of subcortical structures in HIV-infected patients from a multisite study

The automated volumetric output of FreeSurfer and Individual Brain Atlases using Statistical Parametric Mapping (IBASPM), two widely used and well published software packages, was examined for accuracy and consistency relative to auto-assisted manual (AAM) tracings (i.e., manual correction of automated output) when measuring the caudate, putamen, amygdala, and hippocampus in the baseline scans of 120 HIV-infected patients (86.7% male, 47.3+/-6.3y.o., mean HIV duration 12.0+/-6.3years) from the NIH-funded HIV Neuroimaging Consortium (HIVNC) cohort. The data was examined for accuracy and consistency relative to auto-assisted manual tracing, and construct validity was assessed by correlating automated and AAM volumetric measures with relevant clinical measures of HIV progression. When results were averaged across all patients in the eight structures examined, FreeSurfer achieved lower absolute volume difference in five, higher sensitivity in seven, and higher spatial overlap in all eight structures. Additionally, FreeSurfer results exhibited less variability in all measures. Output from both methods identified discrepant correlations with clinical measures of HIV progression relative to AAM segmented data. Overall, FreeSurfer proved more effective in the context of subcortical volumetry in HIV-patients, particularly in a multisite cohort study such as this. These findings emphasize that regardless of the automated method used, visual inspection of segmentation output, along with manual correction if necessary, remains critical to ensuring the validity of reported results.

Is hypoglycaemia dangerous?

Tight glycaemic control (TGC) for patients treated in an intensive care unit ICU is associated with an increased risk for hypoglycaemia. Since hypoglycaemia mainly occurs in the sickest patients, no matter whether TGC is applied or not, it might be a marker for severity of illness or a harmful event in itself. Furthermore, it remains a matter of debate whether harmful effects of hypoglycaemia outbalance the clinical benefits of TGC. This review focusses on the clinical manifestations of hypoglycaemia in the critically ill and highlights its potential short- and long-term consequences specifically concerning neurocognitive function.

Children's higher order cognitive abilities and the development of secondary memory

The relations between higher cognitive abilities and immediate and delayed recall were studied in 57 children (6-16 years of age). The participants were tested repeatedly on free recall of a supraspan list (Children's Memory Scale), and their fluid ability was also assessed (Woodcock-Johnson III Spatial Relations). Consistent with Unsworth and Engle's (2007) account of the relation between memory and higher order cognition, the children's fluid ability was significantly correlated with retrieval from secondary memory, regardless of whether it was measured using immediate or delayed recall. Multiple regression analyses provided further support for this view, revealing that measures of immediate and delayed retrieval from secondary memory accounted for the same variance in the children's fluid ability.

Brain volume abnormalities and neurocognitive deficits in diabetes mellitus: points of pathophysiological commonality with mood disorders?

BACKGROUND

It is hypothesized that diabetes mellitus (DM) and mood disorders share points of pathophysiological commonality in the central nervous system.

METHODS

A PubMed search of all English-language articles published between 1966 and March 2009 was performed with the following search terms: depression, mood disorders, hippocampus, amygdala, central nervous system, brain, neuroimaging, volumetric, morphometric, and neurocognitive deficits, cross-referenced with DM. Articles selected for review were based on adequacy of sample size, the use of standardized experimental procedures, validated assessment measures, and overall manuscript quality. The primary author was principally responsible for adjudicating the merit of articles that were included.

RESULTS

Volumetric studies indicate that individuals with Type 1/2 DM exhibit regional abnormalities in both cortical and subcortical (e.g., hippocampus, amygdala) brain structures. The pattern of neurocognitive deficits documented in individuals with Type 1 DM overlap with Type 2 populations, with suggestions of discrete abnormalities unique to each phenotype. The pattern of volumetric and neurocognitive deficits in diabetic populations are highly similar to that reported in populations of individuals with major depressive disorder.

CONCLUSION

The prevailing models of disease pathophysiology in DM and major depressive disorder are distinct. Notwithstanding, the common abnormalities observed in disparate effector systems (e.g., insulin resistance, immunoinflammatory activation) as well as brain volume and neurocognitive performance provide the nexus for hypothesizing that both conditions are subserved by overlapping pathophysiology. This conception provides a novel framework for disease modeling and treatment development in mood disorder.

Hippocampal volumes in youth with type 1 diabetes

OBJECTIVE

Hippocampal neurons in adult animals and humans are vulnerable to severe hypoglycemia and hyperglycemia. Effects are hypothesized to be exacerbated during development, but existing studies on developing human brains are limited. We examined whether hypoglycemia or hyperglycemia experienced during brain development in humans affects hippocampal volumes.

RESEARCH DESIGN AND METHODS

We analyzed T1-weighted magnetic resonance images in 95 youth with type 1 diabetes and 49 sibling control subjects aged 7-17 years. Youth with diabetes were categorized as having 0 (n = 37), 1-2 (n = 41), or 3 or more (3+; n = 17) prior severe hypoglycemic episodes. Hyperglycemia exposure was estimated from median lifetime A1C, weighted for duration of diabetes. Stereologic measurements of hippocampal volumes were performed in atlas-registered space to correct for whole brain volume.

RESULTS

Greater exposure to severe hypoglycemia was associated with larger hippocampal volumes (F [3,138] = 3.6, P = 0.016; 3+ larger than all other groups, P < 0.05). Hyperglycemia exposure was not associated with hippocampal volumes (R(2) change = 0.003, F [1,89] = 0.31, P = 0.58, semipartial r = 0.06; one outlier removed for high median A1C), and the 3+ severe hypoglycemia group still had larger hippocampal volumes after controlling for age of onset and hyperglycemia exposure (main effect of hypoglycemia category, F [2,88] = 6.4, P = 0.002; 3+ larger than all other groups, P < 0.01).

CONCLUSIONS

Enlargement of the hippocampus may reflect a pathological reaction to hypoglycemia during brain development, such as gliosis, reactive neurogenesis, or disruption of normal developmental pruning.

Understanding the role of nutrition in the brain and behavioral development of toddlers and preschool children: identifying and addressing methodological barriers

The preschool years (i.e. 1-5 years of age) is a time of rapid and dramatic postnatal brain development (i.e. neural plasticity), and of fundamental acquisition of cognitive development (i.e. working memory, attention and inhibitory control). Also, it is a time of transition from a direct maternal mediation/selection of diet-based nutrition to food selection that is more based on self-selection and self-gratification. However, there have been fewer published studies in preschool children than in infants or school-aged children that examined the role of nutrition in brain/mental development (125 studies versus 232 and 303 studies, respectively during the last 28 years). This may arise because of age-related variability, in terms of individual differences in temperament, linguistic ability, and patterns of neural activity that may affect assessment of neural and cognitive development in pre-school children. In this review, we suggest several approaches for assessing brain function in children that can be refined. It would be desirable if the discipline developed some common elements to be included in future studies of diet and brain function, with the idea that they would complement more targeted measures based on time of exposure and understanding of data from animal models. Underlining this approach is the concept of 'window of sensitivity' during which nutrients may affect postnatal neural development: investigators and expert panels need to look specifically for region-specific changes and do so with understanding of the likely time window during which the nutrient was, or was not available.

Diabetes increases brain damage caused by severe hypoglycemia

Insulin-induced severe hypoglycemia causes brain damage. The hypothesis to be tested was that diabetes portends to more extensive brain tissue damage following an episode of severe hypoglycemia. Nine-week-old male streptozotocin-diabetic (DIAB; n = 10) or vehicle-injected control (CONT; n = 7) Sprague-Dawley rats were subjected to hyperinsulinemic (0.2 U.kg(-1).min(-1)) severe hypoglycemic (10-15 mg/dl) clamps while awake and unrestrained. Groups were precisely matched for depth and duration (1 h) of severe hypoglycemia (CONT 11 +/- 0.5 and DIAB 12 +/- 0.2 mg/dl, P = not significant). During severe hypoglycemia, an equal number of episodes of seizure-like activity were noted in both groups. One week later, histological analysis demonstrated extensive neuronal damage in regions of the hippocampus, especially in the dentate gyrus and CA1 regions and less so in the CA3 region (P < 0.05), although total hippocampal damage was not different between groups. However, in the cortex, DIAB rats had significantly (2.3-fold) more dead neurons than CONT rats (P < 0.05). There was a strong correlation between neuronal damage and the occurrence of seizure-like activity (r(2) > 0.9). Separate studies conducted in groups of diabetic (n = 5) and nondiabetic (n = 5) rats not exposed to severe hypoglycemia showed no brain damage. In summary, under the conditions studied, severe hypoglycemia causes brain damage in the cortex and regions within the hippocampus, and the extent of damage is closely correlated to the presence of seizure-like activity in nonanesthetized rats. It is concluded that, in response to insulin-induced severe hypoglycemia, diabetes uniquely increases the vulnerability of specific brain areas to neuronal damage.

Inflammation in Diabetic Encephalopathy is Prevented by C-Peptide

Encephalopathy is an increasingly recognized complication of type 1 diabetes. The underlying mechanisms are not well understood, although insulin deficiency has been implicated. The spontaneously diabetic BB/Wor-rat develops neuro-behavioral deficits and neuronal cell death in hippocampus and frontal cortex, which can be prevented by insulinomimetic C-peptide. Here we examined whether contributing factors such as activation of innate immune mediators are responsive to C-peptide replacement. Seven-month diabetic BB/Wor-rats and those treated with full C-peptide replacement were compared to age-matched control rats. Hippocampi of diabetic rats showed upregulation of RAGE and NF-kappaB, the former being localized to proliferating astrocytes. These changes were associated with increased expression of TNF-alpha, IL-1beta, IL-2 and IL-6 in hippocampi of diabetic rats. Full C-peptide replacement, which did not induce hyperglycemia, resulted in significant prevention of upregulation of RAGE expression, activation of NF-kappaB and activation of pro-inflammatory factors. In conclusion, impaired insulin activity is associated with upregulation of RAGE and pro-inflammatory factors, and these are likely to contribute to previously described oxidative and apoptotic neuronal cell death. Replacement of insulinomimetic C-peptide significantly prevents this cascade of events.

Central nervous system function in youth with type 1 diabetes 12 years after disease onset

OBJECTIVE

In this study, we used neurocognitive assessment and neuroimaging to examine brain function in youth with type 1 diabetes studied prospectively from diagnosis.

RESEARCH DESIGN AND METHODS

We studied type 1 diabetic (n = 106) and control subjects (n = 75) with no significant group difference on IQ at baseline 12 years previously by using the Wechsler Abbreviated Scale of General Intelligence, magnetic resonance spectroscopy and imaging, and metabolic control data from diagnosis.

RESULTS

Type 1 diabetic subjects had lower verbal and full scale IQs than control subjects (both P < 0.05). Type 1 diabetic subjects had lower N-acetylaspartate in frontal lobes and basal ganglia and higher myoinositol and choline in frontal and temporal lobes and basal ganglia than control subjects (all P < 0.05). Type 1 diabetic subjects, relative to control subjects, had decreased gray matter in bilateral thalami and right parahippocampal gyrus and insular cortex. White matter was decreased in bilateral parahippocampi, left temporal lobe, and middle frontal area (all P < 0.0005 uncorrected). T2 in type 1 diabetic subjects was increased in left superior temporal gyrus and decreased in bilateral lentiform nuclei, caudate nuclei and thalami, and right insular area (all P < 0.0005 uncorrected). Early-onset disease predicted lower performance IQ, and hypoglycemia was associated with lower verbal IQ and volume reduction in thalamus; poor metabolic control predicted elevated myoinositol and decreased T2 in thalamus; and older age predicted volume loss and T2 change in basal ganglia.

CONCLUSIONS

This study documents brain effects 12 years after diagnosis in a type 1 diabetic sample whose IQ at diagnosis matched that of control subjects. Findings suggest several neuropathological processes including gliosis, demyelination, and altered osmolarity.

Perspectives from the symposium: The role of nutrition in infant and toddler brain and behavioral development

This symposium examined current trends in neuroscience and developmental psychology as they apply to assessing the effects of nutrients on brain and behavioral development of 0-6-year-olds. Although the spectrum of nutrients with brain effects has not changed much in the last 25 years, there has been an explosion in new knowledge about the genetics, structure and function of the brain. This has helped to link the brain mechanistic pathway by which these nutrients act with cognitive functions. A clear example of this is linking of brain structural changes due to hypoglycemia versus hyperglycemia with cognitive functions by using magnetic resonance imaging (MRI) to assess changes in brain-region volumes in combination with cognitive test of intelligence, memory and processing speed. Another example is the use of event-related potential (ERP) studies to show that infants of diabetic mothers have impairments in memory from birth through 8 months of age that are consistent with alterations in mechanistic pathways of memory observed in animal models of perinatal iron deficiency. However, gaps remain in the understanding of how nutrients and neurotrophic factors interact with each other in optimizing brain development and function.

A look inside the diabetic brain: Contributors to diabetes-induced brain aging

Central nervous system (CNS) complications resulting from diabetes is a problem that is gaining more acceptance and attention. Recent evidence suggests morphological, electrophysiological and cognitive changes, often observed in the hippocampus, in diabetic individuals. Many of the CNS changes observed in diabetic patients and animal models of diabetes are reminiscent of the changes seen in normal aging. The central commonalities between diabetes-induced and age-related CNS changes have led to the theory of advanced brain aging in diabetic patients. This review summarizes the findings of the literature as they relate to the relationship between diabetes and dementia and discusses some of the potential contributors to diabetes-induced CNS impairments.

Impact of diabetes and its treatment on cognitive function among adolescents who participated in the Diabetes Control and Complications Trial

OBJECTIVE

The purpose of this study was to evaluate whether severe hypoglycemia or intensive therapy affects cognitive performance over time in a subgroup of patients who were aged 13-19 years at entry in the Diabetes Control and Complications Trial (DCCT).

RESEARCH DESIGN AND METHODS

This was a longitudinal study involving 249 patients with type 1 diabetes who were between 13 and 19 years old when they were randomly assigned in the DCCT. Scores on a comprehensive battery of cognitive tests obtained during the Epidemiology of Diabetes Interventions and Complications follow-up study, approximately 18 years later, were compared with baseline performance. We assessed the effects of the original DCCT treatment group assignment, mean A1C values, and frequency of severe hypoglycemic events on eight domains of cognition.

RESULTS

There were a total of 294 reported episodes of coma or seizure. Neither frequency of hypoglycemia nor previous treatment group was associated with decline on any cognitive domain. As in a previous analysis of the entire study cohort, higher A1C values were associated with declines in the psychomotor and mental efficiency domain (P < 0.01); however, the previous finding of improved motor speed with lower A1C values was not replicated in this subgroup analysis.

CONCLUSIONS

Despite relatively high rates of severe hypoglycemia, cognitive function did not decline over an extended period of time in the youngest cohort of patients with type 1 diabetes.

Prevalence of structural central nervous system abnormalities in early-onset type 1 diabetes mellitus

OBJECTIVE

To characterize the effects of severe hypoglycemia on the developing brain in children with early-onset type 1 diabetes mellitus (T1DM).

STUDY DESIGN

Children diagnosed with T1DM before age 6 years were studied. Those with prospectively monitored severe hypoglycemia (coma/seizure; n = 32) were compared with age-matched peers (n = 30) with no history of such events using magnetic resonance imaging. Glycemic control (evaluated based on glycated hemoglobin [HbA(lc)] level), episodes of diabetic ketoacidosis (DKA), and clinical variables were monitored continuously since diagnosis in all subjects.

RESULTS

Mean HbA(lc) from diagnosis and the duration of T1DM were similar in those with and without a history of severe hypoglycemia (9.0% +/- 0.9% vs 8.8% +/- 0.9%; 7.2 +/- 2.7 years vs 6.7 +/- 2.3 years). A high prevalence of central nervous system (CNS) structural abnormalities was detected (29%), and mesial temporal sclerosis (MTS) was detected in 16% of the total sample (n = 62). The presence of MTS was not associated with a history of severe hypoglycemia or DKA. Analysis of brain matter volumes suggested relatively less gray matter density in those subjects with a history of severe hypoglycemia.

CONCLUSIONS

Early age of onset of T1DM per se is associated with a high incidence of CNS abnormalities, particularly MTS, suggesting hippocampal damage. Early-onset severe hypoglycemia may have an effect on gray matter volume.

Cognition and diabetes: a lifespan perspective

Diabetes mellitus is associated with cognitive dysfunction and abnormalities that can be seen with brain imaging. Recent studies provide important new insights into the nature and severity of these cerebral complications that help to explain why some patients with diabetes have clinically relevant neurocognitive morbidity, whereas most are apparently unaffected. This Personal View investigates the hypothesis that clinically relevant diabetes-related cognitive decrements mainly occur at two crucial periods in life: when the brain is developing in childhood, and when the brain undergoes neurodegenerative changes associated with ageing. Outside of these periods cognitive decrements mainly occur in patients with notable diabetes-related comorbidities, in particular microvascular or macrovascular complications. The identification of crucial periods and conditions for the development of diabetes-related cognitive decrements helps to draw the attention of physicians to individuals at risk and can direct future studies into the mechanisms that underlie these conditions.

Hyperglycaemia as a determinant of cognitive decline in patients with type 1 diabetes

Individuals with type 1 diabetes show mild performance deficits in a range of neuropsychological tests compared to healthy controls, but the mechanisms underlying this cognitive deterioration are still poorly understood. Basically, two diabetes-related mechanisms can be postulated: recurrent severe hypoglycaemia and/or chronic hyperglycaemia. Intensive insulin therapy in type 1 diabetes, resulting in a durable improvement of glycaemic control, has been shown to lower the risk of long-term microvascular and macrovascular complications. The down side of striving for strict glycaemic control is the considerably elevated risk of severe hypoglycaemia, sometimes leading to seizure or coma. While retrospective studies in adult patients with type 1 diabetes have suggested an association between a history of recurrent severe hypoglycaemia and a modest or even severe degree of cognitive impairment, large prospective studies have failed to confirm this association. Only fairly recently, better appreciation of the possible deleterious effects of chronic hyperglycaemia on brain function and structure is emerging. In addition, it can be hypothesized that hyperglycaemia associated microvascular changes in the brain are responsible for the cognitive decline in patients with type 1 diabetes. This review presents various pathophysiological considerations concerning the cognitive decline in patients with type 1 diabetes.

Psychiatric symptoms in a patient with Wolfram syndrome caused by a combination of thalamic deficit and endocrinological pathologies

DIDMOAD or Wolfram syndrome is a hereditary disorder characterized by early onset diabetes and optic atrophy. Besides these features, a variety of other symptoms have been described including psychiatrical abnormalities leading to hospitalization in about 25% of all patients. To our knowledge, until now, a detailed characterization of these psychiatric symptoms does not exist. Here we describe a 21-year-old male patient with deficits of frontal lobe function, such as impaired impulse control and learning deficits. Magnetic resonance imaging (MRI) of the brain showed a bilateral optic atrophy, but no signs of frontal brain atrophy. Neuropsychological tests revealed performance deficits in complex planning (e.g., Tower of London). Also his capacities in memorizing logically connected information after a short and delayed period of time were significantly reduced. Since histopathological studies did not reveal frontal brain abnormalities, but did show thalamic neuronal loss and gliosis, we interpret our findings as representative of thalamic dysfunction. In addition, hypoglycaemia seemed to trigger rapid mood swings. As soon as blood glucose levels improved, the patient stabilized emotionally and assaultive behaviour disappeared while the cognitive deficits remained unchanged.

Diabetes, sugar-coated but harmful to the brain

Type 2 diabetes mellitus appears to directly impair cognition and brain function, independent of its associated cardiovascular disease. This is supported by the presence of similar findings among adults with insulin resistance (pre-diabetes) and obese children with type 2 diabetes, years before overt cardiovascular disease. Hippocampal based memory performance is impaired early in the disease, although deficits in executive function, attention, and psychomotor speed are also seen in more chronic disease and/or poorer disease control, particularly in the presence of co-morbidities such as hypertension. Although there has been some speculation as to possible links between diabetes and Alzheimer's Disease based on associations found in population studies, no convincing empirical evidence has been put forth and brain autopsy studies, the gold standard of Alzheimer's diagnosis, have not supported such a link. Future studies should focus on understanding the mechanisms for the cognitive impairments associated with type 2 diabetes. We propose that insulin resistance-associated impairments in vascular reactivity and endothelial function are possible candidates as they may impact substrate delivery across the blood-brain-barrier. These are important issues given the obesity epidemic and the associated rising prevalence of insulin resistance and type 2 diabetes.