SPATIAL MEMORY AND EXECUTIVE FUNCTIONING IN THE GOTO-KAKIZAKI RAT MODEL OF DIABETES

Type 2 diabetes mellitus is a disease that adversely affects cognitive function in areas extending to memory and executive functioning. The Goto-Kakizaki (GK) rat provides a model of type 2 diabetes that can illustrate the mechanisms by which this disease works. The present study compared hyperglycaemic GK rats and age-matched Wistar rats in the Morris water maze to assess spatial memory, and in a perceptual attentional set-shifting task to assess putative prefrontal-dependent executive functioning. Results showed there was no difference in path length during training trials, however, GK and Wistar rats differed in the path length travelled in the target quadrant during the probe trial. Although search strategies became more precise for both strains over the spatial training days, GK rat search strategies were less precise than Wistar rats. A urinary glucose test performed on the first and last days of water maze testing revealed that urine glucose significantly decreased after the water maze for GK rats. Golgi-Cox staining was used to examine dendritic complexity and spine densities in the suprapyramidal layer of the dentate gyrus. There was significantly less dendritic arbour and branching complexity in the GK rat dentate gyrus, particularly in the middle molecular layer. Spine densities were significantly decreased for GK rats in each molecular layer in the suprapyramidal blade. Results suggest that spatial memory retrieval deficits may be linked to diabetes, a mechanism thought to be associated with the dentate gyrus. In the attentional set-shifting task, Day 1 of the task involved training rats to dig for food rewards and discriminate between different odours, digging mediums, and textures. Day 2 of the task consisted of a series of 7 shifts including discriminations, an intradimensional shift, an extradimensional shift, and 3 reversals. GK rats required significantly more trials to reach criterion in the discriminations, but not the other shifts. Duration of the discrimination and reversal 1 trials were also significantly greater for the GK rats. Urinary glucose tests validated hyperglycemia both before and after the task. Golgi-Cox staining was used to examine pyramidal neuron spine densities in the prelimbic cortex. Spine densities were significantly decreased for GK rats in layers II/III in the basilar and apical dendrites. Results suggest that GK rats have morphological changes in the prefrontal cortex despite having preserved executive function. The cognitive deficits observed in GK rats appear to be related to altered perception rather than executive functioning. Keywords: Goto-Kakizaki rat; type 2 diabetes; dentate gyrus; prelimbic corte

Obesity and brain structure in schizophrenia - ENIGMA study in 3021 individuals

Schizophrenia is frequently associated with obesity, which is linked with neurostructural alterations. Yet, we do not understand how the brain correlates of obesity map onto the brain changes in schizophrenia. We obtained MRI-derived brain cortical and subcortical measures and body mass index (BMI) from 1260 individuals with schizophrenia and 1761 controls from 12 independent research sites within the ENIGMA-Schizophrenia Working Group. We jointly modeled the statistical effects of schizophrenia and BMI using mixed effects. BMI was additively associated with structure of many of the same brain regions as schizophrenia, but the cortical and subcortical alterations in schizophrenia were more widespread and pronounced. Both BMI and schizophrenia were primarily associated with changes in cortical thickness, with fewer correlates in surface area. While, BMI was negatively associated with cortical thickness, the significant associations between BMI and surface area or subcortical volumes were positive. Lastly, the brain correlates of obesity were replicated among large studies and closely resembled neurostructural changes in major depressive disorders. We confirmed widespread associations between BMI and brain structure in individuals with schizophrenia. People with both obesity and schizophrenia showed more pronounced brain alterations than people with only one of these conditions. Obesity appears to be a relevant factor which could account for heterogeneity of brain imaging findings and for differences in brain imaging outcomes among people with schizophrenia

Diagnosis of bipolar disorders and body mass index predict clustering based on similarities in cortical thickness-ENIGMA study in 2436 individuals

AIMS: Rates of obesity have reached epidemic proportions, especially among people with psychiatric disorders. While the effects of obesity on the brain are of major interest in medicine, they remain markedly under-researched in psychiatry. METHODS: We obtained body mass index (BMI) and magnetic resonance imaging-derived regional cortical thickness, surface area from 836 bipolar disorders (BD) and 1600 control individuals from 14 sites within the ENIGMA-BD Working Group. We identified regionally specific profiles of cortical thickness using K-means clustering and studied clinical characteristics associated with individual cortical profiles. RESULTS: We detected two clusters based on similarities among participants in cortical thickness. The lower thickness cluster (46.8% of the sample) showed thinner cortex, especially in the frontal and temporal lobes and was associated with diagnosis of BD, higher BMI, and older age. BD individuals in the low thickness cluster were more likely to have the diagnosis of bipolar disorder I and less likely to be treated with lithium. In contrast, clustering based on similarities in the cortical surface area was unrelated to BD or BMI and only tracked age and sex. CONCLUSIONS: We provide evidence that both BD and obesity are associated with similar alterations in cortical thickness, but not surface area. The fact that obesity increased the chance of having low cortical thickness could explain differences in cortical measures among people with BD. The thinner cortex in individuals with higher BMI, which was additive and similar to the BD-associated alterations, may suggest that treating obesity could lower the extent of cortical thinning in BD

SPATIAL MEMORY AND EXECUTIVE FUNCTIONING IN THE GOTO-KAKIZAKI RAT MODEL OF DIABETES

Type 2 diabetes mellitus is a disease that adversely affects cognitive function in areas extending to memory and executive functioning. The Goto-Kakizaki (GK) rat provides a model of type 2 diabetes that can illustrate the mechanisms by which this disease works. The present study compared hyperglycaemic GK rats and age-matched Wistar rats in the Morris water maze to assess spatial memory, and in a perceptual attentional set-shifting task to assess putative prefrontal-dependent executive functioning. Results showed there was no difference in path length during training trials, however, GK and Wistar rats differed in the path length travelled in the target quadrant during the probe trial. Although search strategies became more precise for both strains over the spatial training days, GK rat search strategies were less precise than Wistar rats. A urinary glucose test performed on the first and last days of water maze testing revealed that urine glucose significantly decreased after the water maze for GK rats. Golgi-Cox staining was used to examine dendritic complexity and spine densities in the suprapyramidal layer of the dentate gyrus. There was significantly less dendritic arbour and branching complexity in the GK rat dentate gyrus, particularly in the middle molecular layer. Spine densities were significantly decreased for GK rats in each molecular layer in the suprapyramidal blade. Results suggest that spatial memory retrieval deficits may be linked to diabetes, a mechanism thought to be associated with the dentate gyrus. In the attentional set-shifting task, Day 1 of the task involved training rats to dig for food rewards and discriminate between different odours, digging mediums, and textures. Day 2 of the task consisted of a series of 7 shifts including discriminations, an intradimensional shift, an extradimensional shift, and 3 reversals. GK rats required significantly more trials to reach criterion in the discriminations, but not the other shifts. Duration of the discrimination and reversal 1 trials were also significantly greater for the GK rats. Urinary glucose tests validated hyperglycemia both before and after the task. Golgi-Cox staining was used to examine pyramidal neuron spine densities in the prelimbic cortex. Spine densities were significantly decreased for GK rats in layers II/III in the basilar and apical dendrites. Results suggest that GK rats have morphological changes in the prefrontal cortex despite having preserved executive function. The cognitive deficits observed in GK rats appear to be related to altered perception rather than executive functioning. Keywords: Goto-Kakizaki rat; type 2 diabetes; dentate gyrus; prelimbic corte

Obesity and brain structure in schizophrenia - ENIGMA study in 3021 individuals

Schizophrenia is frequently associated with obesity, which is linked with neurostructural alterations. Yet, we do not understand how the brain correlates of obesity map onto the brain changes in schizophrenia. We obtained MRI-derived brain cortical and subcortical measures and body mass index (BMI) from 1260 individuals with schizophrenia and 1761 controls from 12 independent research sites within the ENIGMA-Schizophrenia Working Group. We jointly modeled the statistical effects of schizophrenia and BMI using mixed effects. BMI was additively associated with structure of many of the same brain regions as schizophrenia, but the cortical and subcortical alterations in schizophrenia were more widespread and pronounced. Both BMI and schizophrenia were primarily associated with changes in cortical thickness, with fewer correlates in surface area. While, BMI was negatively associated with cortical thickness, the significant associations between BMI and surface area or subcortical volumes were positive. Lastly, the brain correlates of obesity were replicated among large studies and closely resembled neurostructural changes in major depressive disorders. We confirmed widespread associations between BMI and brain structure in individuals with schizophrenia. People with both obesity and schizophrenia showed more pronounced brain alterations than people with only one of these conditions. Obesity appears to be a relevant factor which could account for heterogeneity of brain imaging findings and for differences in brain imaging outcomes among people with schizophrenia.FUNDING: NAC et al. were supported by the Agencia Nacional de Investigación y Desarrollo, Chile, through its grants PIA ACT1414, ANID-PIA-ACT 192064, and FONDECYT regular 1200601. This work was funded by the German Research Foundation (DFG, grant FOR2107 DA1151/5-1 and DA1151/5-2 to UD; SFB-TRR58, Projects C09 and Z02 to UD) and the Interdisciplinary Center for Clinical Research (IZKF) of the medical faculty of Münster (grant Dan3/012/17 to UD). The NUDZ and IKEM sites were supported by funding from the Ministry of Health of the Czech Republic (16-32791A, NU20-04-00393) and conceptual development of research organization (Institute for Clinical and Experimental Medicine – IKEM, IN 00023001). This work was also funded by the German Research Foundation (DFG grant FOR2107, KI588/14-1 and FOR2107, KI588/14-2 to TTJK, Marburg, Germany), as well as, the Alexander von Humboldt Foundation, EU and Deutsche Forschungsgemeinschaft (DFG), grants NE2254/1-2, NE2254/3-1, NE2254/4-1. Additional support provided by research grants from the National Healthcare Group, Singapore (SIG/05004; SIG/05028), and the Singapore Bioimaging Consortium (RP C009/ 2006) research grants awarded to KS. EW was supported by the European Union’s Horizon 2020 research and innovation programme (Early Cause, grant n° 848158). Funding for TWW was provided by the National Health and Medical Research Council Australia Project Grant 568807; New South Wales Health, University of New South Wales, Neuroscience Research Australia and the Schizophrenia Research Institute. GD’s research was funded by the European Research Council 677467 and Science Foundation Ireland 16/ERCS/3787. VDC was supported by NIH R01MH118695. PMT was supported by NIMH grant R01MH116147. Lastly, TH was supported by funding from the Canadian Institutes of Health Research (103703, 106469 and 142255), Nova Scotia Health Research Foundation, Dalhousie Clinical Research Scholarship to TH, Brain & Behavior Research Foundation (formerly NARSAD); 2007 Young Investigator and 2015 Independent Investigator Awards to T

Mega-analysis of association between obesity and cortical morphology in bipolar disorders:ENIGMA study in 2832 participants

Background: Obesity is highly prevalent and disabling, especially in individuals with severe mental illness including bipolar disorders (BD). The brain is a target organ for both obesity and BD. Yet, we do not understand how cortical brain alterations in BD and obesity interact.Methods: We obtained body mass index (BMI) and MRI-derived regional cortical thickness, surface area from 1231 BD and 1601 control individuals from 13 countries within the ENIGMA-BD Working Group. We jointly modeled the statistical effects of BD and BMI on brain structure using mixed effects and tested for interaction and mediation. We also investigated the impact of medications on the BMI-related associations.Results: BMI and BD additively impacted the structure of many of the same brain regions. Both BMI and BD were negatively associated with cortical thickness, but not surface area. In most regions the number of jointly used psychiatric medication classes remained associated with lower cortical thickness when controlling for BMI. In a single region, fusiform gyrus, about a third of the negative association between number of jointly used psychiatric medications and cortical thickness was mediated by association between the number of medications and higher BMI.Conclusions: We confirmed consistent associations between higher BMI and lower cortical thickness, but not surface area, across the cerebral mantle, in regions which were also associated with BD. Higher BMI in people with BD indicated more pronounced brain alterations. BMI is important for understanding the neuroanatomical changes in BD and the effects of psychiatric medications on the brain.</p

Mega-analysis of association between obesity and cortical morphology in bipolar disorders:ENIGMA study in 2832 participants

Background: Obesity is highly prevalent and disabling, especially in individuals with severe mental illness including bipolar disorders (BD). The brain is a target organ for both obesity and BD. Yet, we do not understand how cortical brain alterations in BD and obesity interact.Methods: We obtained body mass index (BMI) and MRI-derived regional cortical thickness, surface area from 1231 BD and 1601 control individuals from 13 countries within the ENIGMA-BD Working Group. We jointly modeled the statistical effects of BD and BMI on brain structure using mixed effects and tested for interaction and mediation. We also investigated the impact of medications on the BMI-related associations.Results: BMI and BD additively impacted the structure of many of the same brain regions. Both BMI and BD were negatively associated with cortical thickness, but not surface area. In most regions the number of jointly used psychiatric medication classes remained associated with lower cortical thickness when controlling for BMI. In a single region, fusiform gyrus, about a third of the negative association between number of jointly used psychiatric medications and cortical thickness was mediated by association between the number of medications and higher BMI.Conclusions: We confirmed consistent associations between higher BMI and lower cortical thickness, but not surface area, across the cerebral mantle, in regions which were also associated with BD. Higher BMI in people with BD indicated more pronounced brain alterations. BMI is important for understanding the neuroanatomical changes in BD and the effects of psychiatric medications on the brain.</p

Mega-analysis of association between obesity and cortical morphology in bipolar disorders:ENIGMA study in 2832 participants

Background: Obesity is highly prevalent and disabling, especially in individuals with severe mental illness including bipolar disorders (BD). The brain is a target organ for both obesity and BD. Yet, we do not understand how cortical brain alterations in BD and obesity interact. Methods: We obtained body mass index (BMI) and MRI-derived regional cortical thickness, surface area from 1231 BD and 1601 control individuals from 13 countries within the ENIGMA-BD Working Group. We jointly modeled the statistical effects of BD and BMI on brain structure using mixed effects and tested for interaction and mediation. We also investigated the impact of medications on the BMI-related associations. Results: BMI and BD additively impacted the structure of many of the same brain regions. Both BMI and BD were negatively associated with cortical thickness, but not surface area. In most regions the number of jointly used psychiatric medication classes remained associated with lower cortical thickness when controlling for BMI. In a single region, fusiform gyrus, about a third of the negative association between number of jointly used psychiatric medications and cortical thickness was mediated by association between the number of medications and higher BMI. Conclusions: We confirmed consistent associations between higher BMI and lower cortical thickness, but not surface area, across the cerebral mantle, in regions which were also associated with BD. Higher BMI in people with BD indicated more pronounced brain alterations. BMI is important for understanding the neuroanatomical changes in BD and the effects of psychiatric medications on the brain.</p

Mega-analysis of association between obesity and cortical morphology in bipolar disorders: ENIGMA study in 2832 participants.

BACKGROUND: Obesity is highly prevalent and disabling, especially in individuals with severe mental illness including bipolar disorders (BD). The brain is a target organ for both obesity and BD. Yet, we do not understand how cortical brain alterations in BD and obesity interact. METHODS: We obtained body mass index (BMI) and MRI-derived regional cortical thickness, surface area from 1231 BD and 1601 control individuals from 13 countries within the ENIGMA-BD Working Group. We jointly modeled the statistical effects of BD and BMI on brain structure using mixed effects and tested for interaction and mediation. We also investigated the impact of medications on the BMI-related associations. RESULTS: BMI and BD additively impacted the structure of many of the same brain regions. Both BMI and BD were negatively associated with cortical thickness, but not surface area. In most regions the number of jointly used psychiatric medication classes remained associated with lower cortical thickness when controlling for BMI. In a single region, fusiform gyrus, about a third of the negative association between number of jointly used psychiatric medications and cortical thickness was mediated by association between the number of medications and higher BMI. CONCLUSIONS: We confirmed consistent associations between higher BMI and lower cortical thickness, but not surface area, across the cerebral mantle, in regions which were also associated with BD. Higher BMI in people with BD indicated more pronounced brain alterations. BMI is important for understanding the neuroanatomical changes in BD and the effects of psychiatric medications on the brain