Neurofunctional evaluation of young male offspring of rat dams with diabetes induced by streptozotocin

Maternal Diabetes and Fetal Programming Toward Neurological Diseases: Beyond Neural Tube Defects

The purpose of this review was to search for experimental or clinical evidence on the effect of hyperglycemia in fetal programming to neurological diseases, excluding evident neural tube defects. The lack of timely diagnosis and the inadequate control of diabetes during pregnancy have been related with postnatal obesity, low intellectual and verbal coefficients, language and motor deficits, attention deficit with hyperactivity, problems in psychosocial development, and an increased predisposition to autism and schizophrenia. It has been proposed that several childhood or adulthood diseases have their origin during fetal development through a phenomenon called fetal programming. However, not all the relationships between the outcomes mentioned above and diabetes during gestation are clear, well-studied, or have been related to fetal programming. To understand this relationship, it is imperative to understand how developmental processes take place in health, in order to understand how the functional cytoarchitecture of the central nervous system takes place; to identify changes prompted by hyperglycemia, and to correlate them with the above postnatal impaired functions. Although changes in the establishment of patterns during central nervous system fetal development are related to a wide variety of neurological pathologies, the mechanism by which several maternal conditions promote fetal alterations that contribute to impaired neural development with postnatal consequences are not clear. Animal models have been extremely useful in studying the effect of maternal pathologies on embryo and fetal development, since obtaining central nervous system tissue in humans with normal appearance during fetal development is an important limitation. This review explores the state of the art on this topic, to help establish the way forward in the study of fetal programming under hyperglycemia and its impact on neurological and psychiatric disorders.

Expression of apoptosis-regulatory genes in the hippocampus of rat neonates born to mothers with diabetes

Diabetes during pregnancy impairs the development of the central nervous system (CNS) and causes cognitive and behavioral abnormalities in offspring. However, the exact mechanism by which the maternal diabetes affects the development of the brain remains to be elucidated. The aim of the present study was to investigate the effects of maternal diabetes in pregnancy on the expression of Bcl-2 and Bax genes and the numerical density of degenerating dark neurons (DNs) in the hippocampus of offspring at the first postnatal two weeks. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was sacrificed at P0, P7, and P14. Our findings demonstrated a significant down-regulation in the hippocampal expression of Bcl-2 in the diabetic group newborns (P < 0.05). In contrast, the mRNA expression of Bax was markedly up-regulated in the offspring born to diabetic dams at all of studied time-points (P < 0.05). Moreover, we found a striking increase in the numerical density of DNs in the various subfields of hippocampus of diabetic group pups (P < 0.05). The results of the present study revealed that maternal hyperglycemia during gestational period may result in disturbances in the expression of Bcl-2 and Bax genes as two important genes in neuronal apoptosis regulation and induces the production of DNs in the developing hippocampus of neonatal rats. These disturbances may be a reason for the cognitive, structural, and behavioral anomalies observed in offspring born to diabetic mothers. Furthermore, the control of maternal glycaemia by insulin administration in most cases normalized these negative impacts.

Synaptogenesis in the Cerebellum of Offspring Born to Diabetic Mothers

There is increasing evidence that maternal diabetes mellitus during the pregnancy is associated with a higher risk of neurodevelopmental and neurofunctional anomalies including motor dysfunctions, learning deficits, and behavioral problems in offspring. The cerebellum is a part of the brain that has long been recognized as a center of movement balance and motor coordination. Moreover, recent studies in humans and animals have also implicated the cerebellum in cognitive processing, sensory discrimination, attention, and learning and memory. Synaptogenesis is one of the most crucial events during the development of the central nervous system. Synaptophysin (SYP) is an integral membrane protein of synaptic vesicles and is considered to be a marker for synaptic density and synaptogenesis. Here, we review the manuscripts focusing on the negative impacts of maternal diabetes in pregnancy on the expression or localization of SYP in the developing cerebellar cortex. We believe that the alteration in synaptogenesis or synapse density may be part of the cascade of events through which diabetes in pregnant women affects the newborn's cerebellum.

Altered expression and localization of synaptophysin in developing cerebellar cortex of neonatal rats due to maternal diabetes mellitus

There is sufficient evidence that diabetes during pregnancy is associated with a higher risk of neurodevelopmental anomalies including learning deficits, behavioral problems and motor dysfunctions in the offspring. Synaptophysin (SYP) is an integral membrane protein of synaptic vesicles and is considered as a marker for synaptogenesis and synaptic density. This study aimed to examine the effects of maternal diabetes in pregnancy on the expression and localization of SYP in the developing rat cerebellum. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was euthanized at postnatal day (P) 0, 7, and 14. The results revealed a significant down-regulation in the mRNA expression of SYP in the offspring born to diabetic animals at both P7 and P14 (P < 0.05 each). One week after birth, there was a significant reduction in the localization of SYP expression in the external granular (EGL) and in the molecular (ML) layers of neonates born to diabetic animals (P < 0.05 each). We also found a marked decrease in the expression of SYP in all of the cerebellar cortical layers of STZ-D group pups at P14 (P < 0.05 each). Moreover, our results revealed no significant changes in either expression or localization of SYP in insulin-treated group pups when compared with the controls (P ≥ 0.05 each). The present study demonstrated that maternal diabetes has adverse effects on the synaptogenesis in the offspring's cerebellum. Furthermore, the rigid maternal blood glucose control in the most cases normalized these negative impacts.

Effect of maternal diabetes on gliogensis in neonatal rat hippocampus

Background:

Diabetes in pregnancy is a common metabolic disorder associated with various adverse outcomes in the offspring including impairments in attention and memory and alterations in social behavior. Glial cells are proven to have a critical role in normal function of neurons, and alteration in their activity could contribute to disturbance in the brain function. The aim of this study was to investigate the effect of maternal diabetes on hippocampal mRNA expression and distribution pattern of glial fibrillary acidic protein (GFAP) immunoreactive glial cells in the dentate gyrus (DG) of rat neonate at postnatal day 14 (P14).

Materials and Methods:

Wistar female rats were randomly allocated in control, diabetic, and insulin-treated diabetic groups. Diabetes was induced by injection of streptozotocin from 4 weeks before gestation until parturition. After delivery, the male offspring was euthanized at P14.

Results:

Our results showed a significant higher level of hippocampal GFAP expression and an increase in the mean number of GFAP positive cells in the DG of diabetic group offspring (P < 0.05). We also found an insignificant up-regulation in the expression of GFAP and the mean number of positive cells in the insulin-treated diabetic group neonates as compared to control group (P > 0.05).

Conclusion:

The present study revealed that diabetes during pregnancy strongly increased the glial cells production in the developing rat hippocampus.

Diabetes in Pregnancy Adversely Affects the Expression of Glycogen Synthase Kinase-3β in the Hippocampus of Rat Neonates

Diabetes during pregnancy causes a wide range of neurodevelopmental and neurocognitive abnormalities in offspring. Glycogen synthase kinase-3 (GSK-3) is widely expressed during brain development and regulates multiple cellular processes, and its dysregulation is implicated in the pathogenesis of diverse neurodegenerative and psychological diseases. This study was designed to examine the effects of maternal diabetes on GSK-3β messenger RNA (mRNA) expression and phosphorylation in the developing rat hippocampus. Female rats were maintained diabetic from a week before pregnancy through parturition, and male offspring was killed immediately after birth. We found a significant bilateral upregulation of GSK-3β mRNA expression in the hippocampus of pups born to diabetic mothers at P0, compared to controls. Moreover, at the same time point, there was a marked bilateral increase in the phosphorylation level of GSK-3β in the diabetic group. Unlike phosphorylation levels, there was a significant upregulation in hippocampal GSK-3β mRNA expression in the insulin-treated group, when compared to controls. The present study revealed that diabetes during pregnancy strongly influences the regulation of GSK-3β in the right/left developing hippocampi. These dysregulations may be part of the cascade of events through which diabetes during pregnancy affects the newborn's hippocampal structure and function.

Some of the experimental and clinical aspects of the effects of the maternal diabetes on developing hippocampus

Diabetes mellitus during pregnancy is associated with an increased risk of multiple congenital anomalies in progeny. There are sufficient evidence suggesting that the children of diabetic women exhibit intellectual and behavioral abnormalities accompanied by modification of hippocampus structure and function. Although, the exact mechanism by which maternal diabetes affects the developing hippocampus remains to be defined. Multiple biological alterations, including hyperglycemia, hyperinsulinemia, oxidative stress, hypoxia, and iron deficiency occur in pregnancies with diabetes and affect the development of central nervous system (CNS) of the fetus. The conclusion from several studies is that disturbance in glucose and insulin homeostasis in mothers and infants are major teratogenic factor in the development of CNS. Insulin and Insulin-like growth factor-1 (IGF-1) are two key regulators of CNS function and development. Insulin and IGF-1 receptors (IR and IGF1R, respectively) are distributed in a highly specific pattern with the high density in some brain regions such as hippocampus. Recent researches have clearly established that maternal diabetes disrupts the regulation of both IR and IGF1R in the hippocampus of rat newborn. Dissecting out the mechanisms responsible for maternal diabetes-related changes in the development of hippocampus is helping to prevent from impaired cognitive and memory functions in offspring.

The effects of induced type-I diabetes on developmental regulation of insulin & insulin like growth factor-1 (IGF-1) receptors in the cerebellum of rat neonates

Diabetes during pregnancy impairs brain development in offspring, leading to behavioral problems, motor dysfunction and learning deficits. Insulin and insulin-like growth factor-1 (IGF-1) are important regulators of developmental and cognitive functions in the central nervous system. Aim of the present study was to examine the effects of maternal diabetes on insulin receptor (InsR) and IGF-1 receptor (IGF-1R) expression in the developing rat cerebellum. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was killed at P0, P7, and P14, an active neurogenesis period in brain development equivalent to the third trimester in human. The expression of InsR and IGF-1R in cerebelli was evaluated using real-time PCR and western blot analysis. We found a significant upregulation of both IGF-1R and InsR transcripts in cerebellum of pups born to diabetic mothers at P0, compared to controls. However, at the same time point, the results of western blot analysis revealed only a slight change in their protein levels. In contrast to InsR, which does not show any difference, there was a markedly reduction in cerebellar expression of IGF-1R mRNA and protein level in the diabetic group of newborns at P7. Moreover, 2 weeks after birth, mRNA expression and protein levels of both InsR and IGF-1R in cerebellum of the diabetic group was significantly downregulated. Compared to controls, we did not find any difference in cerebellar InsR or IGF-1R mRNA and protein levels in the insulin treated group. The present study revealed that diabetes during pregnancy strongly influences the regulation of both InsR and IGF-1R in the developing cerebellum. Furthermore, optimal maternal glycaemia control by insulin administration normalized these effects.

The effects of maternal diabetes on expression of insulin-like growth factor-1 and insulin receptors in male developing rat hippocampus

Diabetes during pregnancy causes neurodevelopmental and neurocognitive abnormalities in offspring. Insulin and insulin-like growth factor-1 (IGF-1) are important regulators of developmental and cognitive functions in the central nervous system. We examined the effects of maternal diabetes on insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor (InsR) expression in the developing rat hippocampus. Female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was killed at P0, P7, and P14. We found a significant bilateral upregulation of both IGF-1R and InsR transcripts in the hippocampus of pups born to diabetic mothers at P0, as compared to controls. However, at the same time point, the results of western blot analysis revealed only a slight change in their protein levels. At P7, there was a marked bilateral reduction in mRNA expression and protein levels of IGF-1R, although not of InsR in the diabetic group. We also found a downregulation in IGF1-R transcripts, especially in left hippocampus of the diabetic group at P14. Moreover, at the same time point, InsR expression was significantly decreased in both hippocampi of diabetic newborns. When compared with controls, we did not find any difference in hippocampal IGF-1R or InsR mRNA and protein levels in the insulin-treated group. The present study revealed that diabetes during pregnancy strongly influences the regulation of both IGF-1R and InsR in the right/left developing hippocampi. Furthermore, the rigid control of maternal glycaemia by insulin administration normalized these effects.