Volumetric investigation of the hippocampus in rat offspring due to diabetes in pregnancy–A stereological study

A Review of Fetal Development in Pregnancies with Maternal Type 2 Diabetes Mellitus (T2DM)-Associated Hypothalamic-Pituitary-Adrenal (HPA) Axis Dysregulation: Possible Links to Pregestational Prediabetes

Research has identified fetal risk factors for adult diseases, forming the basis for the Developmental Origins of Health and Disease (DOHaD) hypothesis. DOHaD suggests that maternal insults during pregnancy cause structural and functional changes in fetal organs, increasing the risk of chronic diseases like type 2 diabetes mellitus (T2DM) in adulthood. It is proposed that altered maternal physiology, such as increased glucocorticoid (GC) levels associated with a dysregulated hypothalamic-pituitary-adrenal (HPA) axis in maternal stress and T2DM during pregnancy, exposes the fetus to excess GC. Prenatal glucocorticoid exposure reduces fetal growth and programs the fetal HPA axis, permanently altering its activity into adulthood. This programmed HPA axis is linked to increased risks of hypertension, cardiovascular diseases, and mental disorders in adulthood. With the global rise in T2DM, particularly among young adults of reproductive age, it is crucial to prevent its onset. T2DM is often preceded by a prediabetic state, a condition that does not show any symptoms, causing many to unknowingly progress to T2DM. Studying prediabetes is essential, as it is a reversible stage that may help prevent T2DM-related pregnancy complications. The existing literature focuses on HPA axis dysregulation in T2DM pregnancies and its link to fetal programming. However, the effects of prediabetes on HPA axis function, specifically glucocorticoid in pregnancy and fetal outcomes, are not well understood. This review consolidates research on T2DM during pregnancy, its impact on fetal programming via the HPA axis, and possible links with pregestational prediabetes.

Pregestational Prediabetes Induces Maternal Hypothalamic-Pituitary-Adrenal (HPA) Axis Dysregulation and Results in Adverse Foetal Outcomes

Maternal type 2 diabetes mellitus (T2DM) has been shown to result in foetal programming of the hypothalamic-pituitary-adrenal (HPA) axis, leading to adverse foetal outcomes. T2DM is preceded by prediabetes and shares similar pathophysiological complications. However, no studies have investigated the effects of maternal prediabetes on foetal HPA axis function and postnatal offspring development. Hence, this study investigated the effects of pregestational prediabetes on maternal HPA axis function and postnatal offspring development. Pre-diabetic (PD) and non-pre-diabetic (NPD) female Sprague Dawley rats were mated with non-prediabetic males. After gestation, male pups born from the PD and NPD groups were collected. Markers of HPA axis function, adrenocorticotropin hormone (ACTH) and corticosterone, were measured in all dams and pups. Glucose tolerance, insulin and gene expressions of mineralocorticoid (MR) and glucocorticoid (GR) receptors were further measured in all pups at birth and their developmental milestones. The results demonstrated increased basal concentrations of ACTH and corticosterone in the dams from the PD group by comparison to NPD. Furthermore, the results show an increase basal ACTH and corticosterone concentrations, disturbed MR and GR gene expression, glucose intolerance and insulin resistance assessed via the Homeostasis Model Assessment (HOMA) indices in the pups born from the PD group compared to NPD group at all developmental milestones. These observations reveal that pregestational prediabetes is associated with maternal dysregulation of the HPA axis, impacting offspring HPA axis development along with impaired glucose handling.

The impact of maternal diabetes on the future health and neurodevelopment of the offspring: a review of the evidence

Maternal health during gestational period is undoubtedly critical in shaping optimal fetal development and future health of the offspring. Gestational diabetes mellitus is a metabolic disorder occurring in pregnancy with an alarming increasing incidence worldwide during recent years. Over the years, there is a growing body of evidence that uncontrolled maternal hyperglycaemia during pregnancy can potentially have detrimental effect on the neurodevelopment of the offspring. Both human and animal data have linked maternal diabetes with motor and cognitive impairment, as well as autism spectrum disorders, attention deficit hyperactivity disorder, learning abilities and psychiatric disorders. This review presents the available data from current literature investigating the relationship between maternal diabetes and offspring neurodevelopmental impairment. Moreover, possible mechanisms accounting for the detrimental effects of maternal diabetes on fetal brain like fetal neuroinflammation, iron deficiency, epigenetic alterations, disordered lipid metabolism and structural brain abnormalities are also highlighted. On the basis of the evidence demonstrated in the literature, it is mandatory that hyperglycaemia during pregnancy will be optimally controlled and the impact of maternal diabetes on offspring neurodevelopment will be more thoroughly investigated.

Effect of exposure to maternal diabetes during pregnancy on offspring's brain cortical thickness and neurocognitive functioning

Little is known about the long-term effects of maternal diabetes during pregnancy (DP), either gestational diabetes or preexisting diabetes (type 1 or type 2), on offspring's brain morphometry and neurocognitive functioning (NCF). This study examined the effect of prenatal exposure to maternal DP on the brain structure and NCF in children between 9 and 10 years of age. This study used cross-sectional neuroimaging and NCF data from the baseline wave of the Adolescent Brain and Cognitive Development® study. Exposure to maternal DP was assigned from the developmental history questionnaire. Differences in the brain cortical thickness (CTh) and five cognitive abilities (executive function, working and episodic memory, processing speed, and language abilities) were examined in diabetes-exposed and diabetes-unexposed children. Linear mixed effect models and generalized linear models were used to adjust for the effect of confounding variables. A total of 9,967 children (718 diabetes-exposed and 9249 unexposed) were included in the analysis. Diabetes-exposed children had lower whole-brain CTh [mean: exposed vs unexposed = 2.725 mm vs 2.732 mm; difference (95%CI): -0.007 mm (-0.013, -0.001)] compared to unexposed children after adjusting for confounding variables. Diabetes-exposed children had lower CTh in most part of the occipital lobe of both hemispheres, right postcentral gyrus, and left superior parietal cortex. Diabetes-exposed children also had lower scores in processing speed task [mean difference (95%CI): -1.7 (-2.8, -0.6)] and total cognition [mean difference (95%CI): -0.6 (-1.2, -0.02)]. Diabetes-exposed children have reduced CTh and NCF during preadolescence, which might have implications for psychomotor development during later life. Prospective studies are needed to confirm our findings.

Exposure to Cadmium Alters the Population of Glial Cell Types and Disrupts the Regulatory Mechanisms of the HPG Axis in Prepubertal Female Rats

Despite the fact that the brain is susceptible to neurotoxicity induced by cadmium (Cd), the effects of Cd on the neuroanatomical development in the hypothalamus and regulatory mechanisms of the hypothalamic-pituitary-gonadal (HPG) axis are not fully understood. To clarify this issue, we investigated the effects of 25 mg/kg BW/day cadmium chloride (CdCl₂) on neuroanatomical alterations in the hypothalamus of prepubertal female rats. Twenty-four Sprague-Dawley rats were randomly assigned to two groups (n = 12), and CdCl₂ was administered via gavage from postnatal days (PND) 21 to PND35. The results of the stereological analysis demonstrated that prepubertal exposure to Cd reduced the number of neurons and oligodendrocytes in the arcuate (ARC) and dorsomedial hypothalamus nucleus (DMH) nuclei. In contrast, Cd exposure increased the number of microglial cells in the ARC and DMH nuclei. Cd exposure decreased the mRNA levels of gonadotropin-releasing hormone (GnRH) and increased the mRNA levels of RFamide-related peptide (RFRP-3), but not kisspeptin (Kiss1) in the hypothalamus. Moreover, hormonal assay showed that Cd exposure caused a reduction in the concentration of gonadotropins: luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum. Immunohistochemical expression of RFRP-3 in neuronal cell bodies demonstrated that the mean number of RFRP-3 expressing neurons in the DMH nucleus of cadmium-treated rats was dramatically higher than the vehicle group. Overall, exposure to Cd during the prepubertal period alters the population of neurons and glial cell types in the hypothalamus. Additionally, Cd exposure disrupts the regulatory mechanisms of the HPG axis.

Berberine and Ginsenoside Rb1 Ameliorate Depression-Like Behavior in Diabetic Rats

Rhizoma coptidis (Huang-lian) and Asian ginseng have been widely used in the treatment of diabetes and other concurrent diseases with apparent effects. This study investigated the effects of the active ingredients of R. coptidis and ginseng, berberine and ginsenoside Rb1, on depression-like behavior in a rat diabetes model. The animal model was established via a high-fat diet and intraperitoneal injection of streptozotocin, while the animal's depression-like behavior was induced via chronic unpredictable mild stress. These experimental rats were divided into four groups: control, depression-like behavior (DLB), metformin plus fluoxetine hydrochloride (M+FH), and berberine plus ginsenoside Rb1 (B+GRb1) groups. Glucose metabolism and insulin resistance were evaluated by oral glucose test and glucose clamp study. Depression-like behavior was evaluated via behavioral analyses, including forced swim, sucrose preference, elevated plus maze, and open-field tests. HE and Nissl staining, plasma cortisol expression of adrenocorticotropic hormone, and brain-derived neurotrophic factor (BDNF) levels were assayed to explore the mechanisms of action. Compared with the control, rats in the DLB group had a significant increase in the levels of blood glucose and depression-like behavior. The B+GRb1 group significantly improved glucose metabolism and insulin resistance, reduced depression-like behavior, downregulated levels of plasma cortisol and adrenocorticotropic hormone under stress, and upregulated BDNF protein expression compared to the DLB rats. HE and Nissl staining data revealed that B+GRb1 protected neurons from pathological and morphological changes. Thus, berberine and ginsenoside Rb1 not only improved glucose metabolism in diabetic rats but also ameliorated their depression-like behavior under chronic unpredictable stress. Mechanistically, studied data with plasma hormonal levels and brain neuronal pathological/morphological changes supported the observed effects. The combination of berberine and ginsenoside Rb1 may have a clinical value in the management of diabetic patients with depression.

Prepubertal exposure to high dose of cadmium induces hypothalamic injury through transcriptome profiling alteration and neuronal degeneration in female rats

Cadmium (Cd) is a toxic metal, which seems to be crucial during the prepubertal period. Cd can destroy the structural integrity of the blood-brain barrier (BBB) and enters into the brain. Although the brain is susceptible to neurotoxicity induced by Cd, the effects of Cd on the brain, particularly hypothalamic transcriptome, are still relatively poorly understood. Therefore, we investigated the molecular effects of Cd exposure on the hypothalamus by profiling the transcriptomic response of the hypothalamus to high dose of Cd (25 mg/kg bw/day cadmium chloride (CdCl₂)) during the prepubertal period in Sprague-Dawley female rats. After sequencing and annotation, differential expression analysis revealed 1656 genes that were differentially expressed that 108 of them were classified into 37 transcription factor (TF) families. According to gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, these differentially expressed genes (DEGs) were involved in different biological processes and neurological disorders including Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), prolactin signaling pathway, PI3K/Akt signaling, and dopaminergic synapse. Five transcripts were selected for further analyses with Real-time quantitative PCR (RT-qPCR). The RT-qPCR results were mostly consistent with those from the high throughput RNA sequencing (RNA-seq). Cresyl violet staining clearly showed an increased neuronal degeneration in the dorsomedial hypothalamus (DMH) and arcuate (Arc) nuclei of the CdCl₂ group. Overall, this study demonstrates that prepubertal exposure to high doses of Cd induces hypothalamic injury through transcriptome profiling alteration in female rats, which reveals the new mechanisms of pathogenesis of Cd in the hypothalamus.

Orbital volume measurements from magnetic resonance images using the techniques of manual planimetry and stereology

Introduction:

Current volume measurement techniques, for the orbit, are time-consuming and involve complex assessments, which prevents their routine clinical use. In this study, we evaluate the applicability and efficacy of stereology and planimetry in orbital volume measurements using magnetic resonance imaging (MRI).

Materials and Methods:

Prospective imaging study using MRI. Sheep craniums and human subjects were evaluated. Water-filling measurements were performed in animal skulls, as the standard validation technique. Planimetry and stereology techniques were used in each dataset. Intraobserver and interobserver reliability testing were applied.

Results:

In stereology customization, 1/6 systematic sampling scheme was determined as optimal with acceptable coefficient of error (3.09%) and low measurement time (1.2 min). In sheep craniums, the mean volume measured by water displacement, planimetry, and stereology was 17.81 ± 0.59 cm³, 18.53 ± 0.24 cm³, and 19.19 ± 0.17 cm³, respectively. Planimetric and stereological methods were highly correlated (r = 0.94; P ≈ 0.001). The mean difference of the orbital volume using planimetry and stereology was 0.316 ± 0.168 cm³. In human subjects, using stereology, the mean orbital volume was found to be 19.62 ± 0.2 cm³ with a CE of 3.91 ± 0.15%.

Conclusions:

The optimized stereological method was found superior to manual planimetry in terms of user effort and time spent. Stereology sampling of 1/6 was successfully applied in human subjects and showed strong correlation with manual planimetry. However, optimized stereological method tended to overestimate the orbital volume by about 1 cc, a considerable limitation to be taken in clinical practice.