Diabetes materno severo e diabetes mellitus tipo 1 : uma perspectiva neuroinflamatória em modelos animais

O diabetes durante a gravidez constitui um ambiente intrauterino desfavorável para o desenvolvimento da prole. Apesar de já descritos na literatura mecanismos candidatos pelos quais o diabetes materno severo predispõe os filhos a alterações cerebrais e distúrbios do neurodesenvolvimento, os seus efeitos a curto e longo prazo sobre o sistema imunológico e as células nervosas, conjuntamente ao comportamento e aos parâmetros físicos da prole ainda não foram estudados. Da mesma forma, o Diabetes Mellitus Tipo 1 (DMT1) tem sido associado a complicações a longo prazo no sistema nervoso central induzidas pela hiperglicemia crônica, causando inflamação, disfunções microvasculares, celulares e moleculares, levando a comprometimento da neurogênese no giro denteado (GD) do hipocampo e déficits cognitivos e psicomotores. No entanto, o papel das respostas microgliais e astrocíticas e a modulação específica de proteínas regulatórias imunes sobre os diferentes estágios da neurogênese hipocampal na progressão da encefalopatia diabética ainda não foram satisfatoriamente elucidadas. No primeiro estudo, investigamos os efeitos a curto e longo prazo dos desfechos desenvolvimentais causados pela hiperglicemia materna severa não controlada sobre a sobrevivência celular no GD, a expressão de proteínas reguladoras de apoptose, o BDNF e a resposta neuroinflamatória no hipocampo de neonatos e ratos jovens nascidos de mães diabéticas. A curto prazo (no dia pós-natal 1), o modelo de diabetes materno severo proposto causou microssomia, atraso no neurodesenvolvimento dos filhotes e diminuição de Bcl-2, procaspase 3 e caspase 3. A longo prazo (no dia pós-natal 40), aumentou os níveis de TNF-α e diminuiu os de procaspase 3, caspase 3, MHC-I, IL-1β e BDNF, bem como prejudicou a sobrevivência celular no GD do hipocampo da prole. No segundo estudo, analisamos os efeitos agudo e crônico do DMT1 não controlado sobre a resposta das células e moléculas reguladoras imunes e a modulação das diferentes fases da neurogênese e apoptose no hipocampo de ratos jovens. Agudamente, o grupo diabético apresentou uma diminuição na proliferação de células marcadas com BrdU no GD, na expressão de Bcl-2 e BDNF, além de um aumento nos níveis de IL-6. Por outro lado, cronicamente, o DMT1 causou uma diminuição nos níveis de IL-1β e IL-10, acompanhado por um aumento na expressão de células microgliais Iba-1+ e uma diminuição não significativa na sobrevivência celular no GD do hipocampo. Os dados reforçam que a ativação da neuroinflamação, a desregulação dos níveis de apoptose, o prejuízo na sinalização de MHC-I e da sobrevivência celular no GD do hipocampo podem estar implicados nos distúrbios neurodesenvolvimentais e neurocognitivos vistos na prole de mães diabéticas. Ainda, que no modelo experimental proposto de DMT1 há um papel importante da neuroinflamação e um desequilíbrio de interleucinas específicas mediadas principalmente pela resposta de células microgliais, durante a janela temporal analisada, contribuindo para o comprometimento das diferentes fases da neurogênese hipocampal subjacente à encefalopatia diabética com a progressão da doença. Desse modo, a presente tese reforça o envolvimento da neuroinflamação como mecanismo neurobiológico presente em ambos os modelos de diabetes estudados.Maternal diabetes constitutes an unfavorable intrauterine environment for offspring development. Although isolated data reveal candidate mechanisms by which severe maternal hyperglycemia predisposes the offspring to neurodevelopmental disorders, their short- and long-term effects on offspring’s immune system, nerve cells, behavior and physical parameters remain poorly understood. Moreover, Type 1 Diabetes Mellitus (T1DM) has been associated with long-term complications in the central nervous system induced by chronic hyperglycemia, causing brain inflammation, microvascular, cellular and molecular dysfunctions, leading to neurogenesis impairment in the dentate gyrus (DG) of hippocampus and cognitive deficits. However, the role of microglial and astrocytic responses and the specific modulation of immune regulatory proteins on the different stages of hippocampal neurogenesis in the progression of diabetic encephalopathy have not yet been satisfactorily elucidated. In our first study, we investigated the short- and long-term effects of developmental outcomes caused by uncontrolled severe maternal hyperglycemia on cell survival in the DG, expression of apoptosis regulatory proteins, BDNF, and the neuroinflammatory response in the hippocampus of neonates and rats young born to diabetic mothers. Severe maternal diabetes caused microsomia and neurodevelopmental delay in pups and decrease of Bcl-2, procaspase 3 and caspase 3 in the hippocampus. In a later stage of development it was found an increase of TNF-α and a decrease of procaspase 3, caspase 3, MHC-I, IL-1β and BDNF in the hippocampus, as well as impairment in cellular survival in the DG. In our second study, we analyzed the acute and chronic effects of uncontrolled T1DM on the response of immune regulatory cells and molecules and the modulation of the different phases of neurogenesis and apoptosis in the hippocampus of young rats. Acutely, diabetic group presented a decrease in proliferation of BrdU-labeled cells, in Bcl-2 expression and BDNF, as well as an increase in IL-6 levels. On the other hand, chronically, T1DM caused a decrease in IL-1β and IL-10 levels, accompanied by an increase in microglial Iba-1 expression and a non-significant decrease in cell survival in the DG of hippocampus. Our data reinforce that activation of neuroinflammation, dysregulation of apoptosis levels, impairment in MHC-I signaling and cell survival in the hippocampus may be implicated in the neurodevelopmental and neurocognitive disorders observed in the offspring of diabetic mothers. In addition, in the proposed experimental model of T1DM there is an important role of neuroinflammation and a specific imbalance of interleukins mediate mainly by the microglia response, until the time-pointed investigated, contributing to the compromise of the different phases of hippocampal neurogenesis underlying the diabetic encephalopathy with disease progression. Thus, this thesis reinforces the involvement of neuroinflammation as a neurobiological mechanism present in both diabetes models studied

Paternal physical exercise modulates global DNA methylation status in the hippocampus of male rat offspring

It is widely known that maternal physical exercise is able to induce beneficial improvements in offspring cognition; however, the effects of paternal exercise have not been explored in detail. The present study was designed to evaluate the impact of paternal physical exercise on memory and learning, neuroplasticity and DNA methylation levels in the hippocampus of male offspring. Adult male Wistar rats were divided into two groups: sedentary or exercised fathers. The paternal preconception exercise protocol consisted of treadmill running, 20 minutes daily, 5 consecutive days per week for 22 days, while the mothers were not trained. After mating, paternal sperm was collected for global DNA methylation analysis. At postnatal day 53, the offspring were euthanized, and the hippocampus was dissected to measure cell survival by 5-bromo-2′-deoxiuridine and to determine the expression of synaptophysin, reelin, brain-derived neurotrophic factor and global DNA methylation levels. To measure spatial memory and learning changes in offspring, the Morris water maze paradigm was used. There was an improvement in spatial learning, as well as a significant decrease in hippocampal global DNA methylation levels in the offspring from exercised fathers compared with those from sedentary ones; however, no changes were observed in neuroplasticity biomarkers brain-derived neurotrophic factor, reelin and 5-bromo-2′-deoxiuridine. Finally, the global DNA methylation of paternal sperm was not significantly changed by physical exercise. These results suggest a link between paternal preconception physical activity and cognitive benefit, which may be associated with hippocampal epigenetic programming in male offspring. However, the biological mechanisms of this modulation remain unclear

Efeito benéfico do enriquecimento ambiental sobre o déficit de memória e a plasticidade celular hipocampal em ratos diabéticos tipo 1

O diabetes mellitus tipo 1 (DMT1) tem sido associado com complicações a longo prazo no sistema nervoso central, além dos efeitos periféricos comuns relacionados à doença, causando disfunções cognitivas no encéfalo. Por outro lado, o enriquecimento ambiental (EA) induz mecanismos de plasticidade dependentes da experiência, especialmente no hipocampo, melhorando o desempenho dos animais em testes de aprendizado e memória. Assim, nosso objetivo foi avaliar a influência do EA sobre o déficit de memória, a atividade locomotora, os níveis de corticosterona, a imunorreatividade da proteína sinaptofisina, e a densidade e a ativação de astrócitos e microglia no giro denteado (GD) do hipocampo de ratos diabéticos tipo 1. Para isso, ratos Wistar machos com 21 dias de idade, foram expostos ao EA ou mantidos em caixamoradia padrão (controles, C) por 3 meses. Quando adultos, os animais tanto C quanto EA foram randomicamente divididos e induziu-se diabetes através de injeção de estreptozotocina em metade dos animais de cada grupo, sendo mantidas as respectivas condições ambientais para cada um dos grupos. A memória espacial dependente de hipocampo foi avaliada em todos os grupos através do teste de reconhecimento de objeto reposicionado, no 41o dia após a indução do diabetes, bem como a locomoção geral dos animais no campo aberto durante o mesmo teste. Os níveis séricos de corticosterona foram medidos ao final do experimento, a imunorreatividade da sinaptofisina foi avaliada por imunoistoquímica, e a densidade e a ativação de astrócitos e da microglia por imunofluorescência no hilo do GD do hipocampo. Nossos resultados mostraram que o EA foi capaz de prevenir ou atrasar o desenvolvimento do déficit de memória causado pelo diabetes em ratos, porém não reverteu o déficit motor observado nos animais diabéticos. Não houve diferença significativa na imunorreatividade da sinaptofisina entre os grupos. Além disso, embora o EA não tenha modificado a densidade e a ativação dos astrócitos nos animais diabéticos, o enriquecimento atenuou os efeitos prejudiciais da hiperglicemia sobre a ativação microglial, bem como reduziu os níveis séricos de corticosterona nos ratos diabéticos adultos. Assim, o EA ajudou a amenizar as comorbidades cognitivas associadas ao diabetes, possivelmente por atenuar a hiperatividade do eixo HPA e a ativação microglial nos animais diabéticos.Type 1 diabetes mellitus (T1DM) has been associated with long-term complications in central nervous system, besides peripheral common adverse effects, causing neurocognitive dysfunction in the brain. On the other hand, enriched environment (EE) induces mechanisms of experiencedependent plasticity especially in hippocampus, improving the performance of animals in learning and memory tasks. Thus, our objective was to investigate the influence of the EE on memory deficits, locomotion, corticosterone levels, synaptophysin protein immunoreactivity, and density and activation of astrocytes and microglia in the hippocampal dentate gyrus (DG) of type 1 diabetic rats. For this, male Wistar rats, 21 days old, were exposed to the EE or maintained in standard housing (controls, C) for 3 months. At adulthood, C and EE animals were randomly divided and half of them induced to diabetes by streptozotocin, being maintained the respective environmental conditions for each animal groups. Hippocampus-dependent spatial memory was evaluated in all groups in the novel object-placement recognition task, on 41th day after diabetes induction, as well as the general locomotion in the open field at the same test. Serum corticosterone levels were measured in the end of the experiment, contents of synaptophysin was evaluated by immunohistochemistry, and density and activation of both astrocytes and microglia by immunofluorescence in the hilus of the DG in hippocampus. Our results showed that EE was able to prevent or delay the development of memory deficits caused by diabetes in rats, however did not revert the motor impairment observed in group diabetic. There was no significant difference in synaptophysin immunoreactivity among the groups. Furthermore, although the EE did not modify the density and activation of astrocytes in diabetic animals, it attenuated the injurious effect of hyperglycemia over microglial activation, as well as decreased the serum level of corticosterone in diabetic adult rats. Thus, the EE has helped to ameliorate cognitive comorbidities associated with T1DM, possibly by reducing the hyperactivity of HPA axis and the microglial activation in diabetic animals

O ENRIQUECIMENTO AMBIENTAL É CAPAZ DE MINIMIZAR OS DEFICITS DE MEMORIA CAUSADOS PELA DIABETES EM RATOS WISTAR?

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O ENRIQUECIMENTO AMBIENTAL É CAPAZ DE MINIMIZAR OS DEFICITS DE MEMORIA CAUSADOS PELA DIABETES EM RATOS WISTAR?

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Enriched environment prevents memory deficits in type 1 diabetic rats

Studies have shown that an enriched environmental (EE) enhances hippocampal neurogenesis and dendritic branching in rodents, improving the performance in learning and memory task. Diabetes, however, is associated with memory deficits and decreasing in cell proliferation in the hippocampal dentate gyrus (DG), possibly related with higher glucocorticoid levels. Thus, our objective was to investigate the influence of EE on the memory deficits and cell proliferation of diabetic rats. For this, we reared rats for 2 months during early stages of life in standard environments (control rats) or EE. At adulthood, control and EE groups were divided and half of them induced to diabetes by a single injection of streptozotocin, 60 mg/kg, via i.p. Memory deficit was evaluated in these groups in the novel object-placement recognition task 11 days after diabetes induction. BrdU label cells were detected by immunohistochemistry after 3 days of administration to correlate cell proliferation in the DG area and performance in the memory task. Our results showed that EE decreased memory deficits in diabetic-induced rats (p < 0.05). Although cell proliferation in the DG was lower in the diabetic rats, enriched environment did not interfere in this parameter. These findings suggest that enriched environment is able to prevent or delay the development of memory deficits caused by diabetes in rats

El magisterio español : Revista General de la Enseñanza: Año LXVIII Número 9297 - 1934 Mayo 31

Incluye suplemento. Incluye el suplemento La Escuela en acción.Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 200