The effects of maternal diabetes and insulin treatment on neurogenesis in the developing hippocampus of male rats

The effects of induced type I diabetes on developmental regulation of GDNF, NRTN, and NCAM proteins in the dentate gyrus of male rat offspring

BACKGROUND

Maternal diabetes during pregnancy can affect the neurological development of offspring. Glial cell-derived neurotrophic factor (GDNF), neurturin (NRTN), and neural cell adhesion molecules (NCAM) are three important proteins for brain development. Therefore, this study aimed to investigate the impacts of the mentioned neurotrophic factors in the hippocampal dentate gyrus (DG) of rat offspring born to diabetic mothers.

METHODS

Wistar female rats were randomly allocated into diabetic (STZ-D) [(45 mg/kg BW, STZ (Streptozotocin), i.p)], diabetic + NPH insulin (STZ-INS) [(4-6 unit/kg/day SC)], and control groups. The animals in all groups were mated by non-diabetic male rats. Two weeks after birth, male pups from each group were sacrificed and then protein contents of GDNF, NRTN, and NCAM were evaluated using immunohistochemistry.

RESULTS

The study found that the expression of GDNF and NRTN in the hippocampus of diabetic rat offspring was significantly higher compared to the diabetic+ insulin and control groups, respectively (P < 0.01, P < 0.001). Additionally, the expression of NCAM was significantly higher in the diabetic group the diabetic+ insulin and control groups (P < 0.01, P < 0.001).

CONCLUSIONS

The results of the study revealed that diabetes during pregnancy significantly impacts the distribution pattern of GDNF, NRTN, and NCAM in the hippocampus of rat neonates.

Maternal diabetes affects rat offspring retinal structure and function: Sex-specific vulnerabilities at infancy

AIMS

Maternal diabetes negatively impacts the offspring's brain, but little is known about its effects on the retina, which is also part of the central nervous system. We hypothesized that maternal diabetes adversely influences offspring retina development leading to structural and functional deficits.

MAIN METHODS

Retinal structure and function were evaluated at infancy, by optical coherence tomography and electroretinography, in male and female offspring of control, diabetic and diabetic-treated with insulin Wistar rats.

KEY FINDINGS

Maternal diabetes induced a delay in male and female offspring eye-opening, while insulin treatment expedited it. Structural analysis showed that maternal diabetes decreased the thickness of the inner and outer segment layer of photoreceptors in male offspring. Electroretinography also revealed that maternal diabetes decreased the amplitude of scotopic b-wave and flicker response in males, suggesting bipolar cells and cone photoreceptor dysfunction, an effect not observed in females. Conversely, maternal diabetes decreased cone arrestin protein levels in female retinas, while not affecting cone photoreceptor number. Dam insulin therapy was efficient in preventing the offspring photoreceptor changes.

SIGNIFICANCE

Our results suggest that photoreceptors are affected by maternal diabetes, which may account for visual impairments at infancy. Notably, both male and female offspring presented specific vulnerabilities to hyperglycemia in this sensitive period of development.

Ursolic acid and rosmarinic acid ameliorate alterations in hippocampal neurogenesis and social memory induced by amyloid beta in mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a multifaceted neurodegenerative disorder characterized by substantial neuronal damage which manifests in the form of deficits in memory and cognition. In spite of the debilitating nature of Alzheimer's disease (AD), a dearth of treatment strategies calls for the need to develop therapeutic agents that stimulate neurogenesis and alleviate the associated cognitive deficits. The present study investigates the therapeutic potential of two major phytochemicals, rosmarinic acid (RA) and ursolic acid (UA) in an amyloid beta_1-42 (Aβ_1-42)-induced model of AD. UA, a natural pentacyclic triterpenoid and RA, a phenolic ester are major bioactive constituents of Rosmarinus officinalis, which is a medicinal herb belonging to family Lamiaceae and exhibiting significant biological properties including neuroprotection. Donepezil, a second generation cholinesterase inhibitor approved for the treatment of mild, moderate and severe Alzheimer's disease (AD) is used as control. Out of eight groups of male BALB/c mice, stereotaxic surgery was performed on four groups (n = 6 each) to introduce Aβ_1-42 in the hippocampus followed by treatment with vehicle (phosphate-buffered saline (PBS)), donepezil, UA or RA. The other four groups were given vehicle, donepezil, UA and RA only. Behavior analysis for social interaction was performed which constitutes the social affiliation and the social novelty preference test. Presence of Aβ plaques and expression of neurogenesis markers i.e., doublecortin (DCX) and Ki-67 were also assessed. Results revealed the neuroprotective effect of UA and RA observed through substantial reduction in Aβ plaques as compared to the Aβ_1-42- and donepezil-treated groups. The neuronal density was also restored as evident via DCX and Ki-67 immunoreactivity in Aβ_1-42 + RA and Aβ_1-42+UA-treated groups in comparison to Aβ_1-42-treated and Aβ_1-42+donepezil-treated groups. The social affiliation was reestablished in the Aβ_1-42 administered groups treated with UA and RA. Molecular docking studies further validated the comparable binding of UA and RA with Ki-67 and DCX to that of donepezil. Our findings suggest that UA and RA are potential neuroprotective compounds that reverses the histological hallmarks of AD and ameliorate impaired social memory and hippocampal neurogenesis.

Di-n-butyl phthalate disrupts neuron maturation in primary rat embryo neurons and male C57BL/6 mice

Di-n-butyl phthalate (DBP) is commonly used as a plasticizer and its usage continues to increase in conjunction with plastic consumption. DBP is readily released into air, drinking water, and soil, and unfortunately, is a potent endocrine disrupter that impairs central nervous system functions. Previously DBP was found to (1) arrest the cell cycle of C17.2 neural progenitor cells (NPCs) at the G1 phase, (2) reduce numbers of newly generated neural stem cells in the mouse hippocampus, and (3) adversely affect learning and memory. Other investigators also noted DBP-mediated neurotoxic effects, but as yet, no study has addressed the adverse effects of DBP on neuronal differentiation. Data demonstrated that at 200 μM DBP induced apoptosis in rat embryo primary neurons by increasing reactive oxygen species levels and inducing mitochondrial dysfunction. However, no significant effect was detected on neurons at concentrations of ≤100 μM. In contrast, doublecortin/microtubule associated protein-2 (DCX/MAP2) immunocytochemistry showed that DBP at 100 μM delayed neuronal maturation by increasing protein levels of DCX (an immature neuronal marker), without markedly affecting cell viability. Further in vivo studies confirmed that DCX⁺ cell numbers were significantly elevated in the hippocampus of DBP-treated mice, indicating that DBP delayed neuronal maturation, which is known to be associated with impaired memory retention. Data demonstrated that DBP might disrupt neuronal maturation, which is correlated with reduced neurocognitive functions.

Maternal diabetes-induced alterations in the expression of brain-derived neurotrophic factor in the developing rat hippocampus

Maternal diabetes during pregnancy affects the development of hippocampus in the offspring. Brain-derived neurotrophic factor (BDNF) has received increasing attention for its role in regulating the survival and differentiation of neuronal cells in developing and adult brain. In the current study, we evaluated the effects of maternal diabetes and insulin treatment on expression and distribution pattern of BDNF in the hippocampus of neonatal rats at the first two postnatal weeks. We found no differences in hippocampal expression of BDNF between diabetics with normal control or insulin treated neonatal rats at postnatal day (P0) (P > 0.05 each). Nevertheless, there was a marked BDNF downregulation in both sides' hippocampi of male/female diabetic group in two-week-old offspring (P ≤ 0.05 each). Furthermore, the numerical density of BDNF+ cells was significantly reduced in the right/left dentate gyrus (DG) of male and female newborns born to diabetic animals at all studied postnatal days (P ≤ 0.05 each). In addition, a lower number of reactive cells have shown in the all hippocampal subareas in the diabetic pups at P14 (P ≤ 0.05 each). Our results have demonstrated that the insulin-treatment improves some of the negative impacts of diabetes on the expression of hippocampal BDNF in the newborns. We conclude that diabetes in pregnancy bilaterally disrupts the expression of BDNF in the hippocampus of the both male and female newborns at early postnatal days. In addition, good glycemic control by insulin in the most cases is sufficient to prevent the alterations in expression of BDNF protein in developing hippocampus.

Protective effect of acorn (Quercus liaotungensis Koidz) on streptozotocin-damaged MIN6 cells and type 2 diabetic rats via p38 MAPK/Nrf2/HO-1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Acorn obtained from the Quercus liaotungensis Koidz tree is consumed as a Chinese folk medicine for the treatment of diarrhea, abdominal pain, and inflammation, also having strong antioxidant activity and have been utilized for the treatment of diabetes in China. However, its mechanism of action on complications of diabetes and oxidative stress is unclear.

AIM OF THE STUDY

The purpose of this research was to assess the effects of acorn (Quercus liaotungensis Koidz) ethanol extract (AE) on pancreatic β-cell dysfunction through a streptozotocin (STZ)-damaged mouse normal pancreatic β-cell (MIN6 cell) model in vitro, and by using a high-fat and high-sugar diet with STZ-induced diabetic rat model in vivo to explore the possible mechanism of action against diabetes.

MATERIALS AND METHODS

MIN6 cells were pretreated with AE (20, 40, 80 μM) for 2 h and then treated with 3 mM STZ for 24 h. Cell viability was measured by MTT assay. The amount of intracellular reactive oxygen species was measured by 2,7-dichlorodi-hydrofluorescein diacetate. The activities of insulin secretion, superoxide dismutase, catalase and glutathione were determined by kits. Sprague Dawley rats were either given normal feed or a high sugar and fat diet for four weeks, followed STZ (25 mg/kg, via i. p.) was given. Rats with fasting blood glucose ≥11.1 mmol/l after one week were deemed to be diabetic. Animals were divided into 5 groups, which received saline (10 mL/kg), metformin (200 mg/kg), or AE at doses of 200 and 400 mg/kg during 4 weeks by oral gavage. Blood samples were used to evaluate hematological and biochemical indicators, and pancreas was removed for post-analysis. Body weight and fasting blood glucose were recorded weekly. The expression levels of Bax, Bcl-2, p38, p-p38, Nrf2 and HO-1 were determined by Western blot.

RESULTS

Data showed that AE inhibited apoptosis and increased antioxidant level in STZ-induced MIN6 cells. In addition, the AE-administered group lowered blood glucose, increased insulin secretion, and alleviated weight loss in the diabetic rats. Histopathologically, the AE-administered group reduced pancreatic injury by significantly restoring the insulin content in β-islets. It was observed that the anti-diabetic effects of AE were associated with the suppressed the p38 MAPK pathway and actived the Nrf2 pathway.

CONCLUSIONS

The ameliorative impact of AE on diabetes may be attributed to protection of the function of pancreatic β islets and by improving serum insulin levels, hence reducing the blood glucose, which involved in the p38 MAPK and Nrf2 pathways.

Sex differences in offspring neurodevelopment, cognitive performance and microglia morphology associated with maternal diabetes: Putative targets for insulin therapy

Diabetes during pregnancy has been shown to affect the central nervous system (CNS) of the offspring, resulting in short- and long-term adverse effects. Children of diabetic mothers are more likely to develop cognitive impairment, also having increased susceptibility to psychiatric disorders. Microglia, the immune cells of the CNS, work as sensors of environmental changes, namely metabolic challenges, as early as the intrauterine period. During this period, microglia is actively involved in processes of neurogenesis, synaptic pruning and detection of any environmental alteration that may impact brain development. The remarkable sex dimorphism in neurodevelopment, as well as sex differences in the morphology and immune function of microglia during development, led us to clarify if maternal diabetes affects specific behavioral traits and microglia morphology during infancy in a sex-specific manner. Another important goal of this study was to clarify if insulin, the gold standard treatment of diabetes during gestation, could prevent maternal diabetes-induced behavioral changes, as well as microglia morphology, also considering sex specificities. Other molecular and cellular players potentially involved in the link between changes in metabolism and behavior were also analyzed in the hippocampus, a brain region implicated in cognition and other behavioral outcomes. Diabetes during pregnancy globally delayed female and male offspring development and was associated with impairments in recognition memory, but only in female offspring. In line with these results, at early and late infancy, some molecular and cellular markers were altered in offspring hippocampus in a sex-specific manner. The strict control of glycemia by insulin during pregnancy prevented most of the negative effects induced by uncontrolled hyperglycemia. Notably, insulin administration to diabetic dams may also modulate offspring development in a way that differs from what is observed in physiological conditions, since it promoted the expedited acquisition of developmental milestones and of discrimination ability at memory test, also inducing a hyper-ramification of male and female hippocampal microglia. Importantly, this study highlights the importance of analyzing the impact of maternal diabetes and insulin therapy, taking into account sex differences, since male and female present different vulnerabilities to hyperglycemia in this critical period of life.

Severe Uncontrolled Maternal Hyperglycemia Induces Microsomia and Neurodevelopment Delay Accompanied by Apoptosis, Cellular Survival, and Neuroinflammatory Deregulation in Rat Offspring Hippocampus

Maternal diabetes constitutes an unfavorable intrauterine environment for offspring development. Although it is known that diabetes can cause brain alterations and increased risk for neurologic disorders, the relationship between neuroimmune activation, brain changes, and neurodevelopment deficits in the offspring remains unclear. In order to elucidate the short- and long-term biological basis of the developmental outcomes caused by the severe uncontrolled maternal hyperglycemia, we studied apoptosis, neurogenesis, and neuroinflammation pathways in the hippocampus of neonates and young rats born to diabetic dams. Diabetes was induced on gestational day 5 by an injection of streptozotocin. Evaluations of milestones, body growth, and inhibitory avoidance were performed to monitor the offspring development and behavior. Hippocampal modifications were studied through cellular survival by BrdU in the dentate gyrus, expression of apoptosis-regulatory proteins (procaspase 3, caspase 3, and Bcl-2), BDNF, and neuroinflammatory modulation by interleukins, MHC-I, MHC-II, Iba-1, and GFAP proteins. Severe maternal diabetes caused microsomia and neurodevelopmental delay in pups and decrease of Bcl-2, procaspase 3, and caspase 3 in the hippocampus. Moreover, 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 dentate gyrus. This study showed significant short- and long-term commitments on the development, apoptosis, cell survival, and neuroinflammation in the offspring hippocampus induced by severe uncontrolled maternal hyperglycemia. The data reinforce the need for treatment of maternal hyperglycemic states during pregnancy and breast-feeding.

The artificial sweetener Splenda intake promotes changes in expression of c-Fos and NeuN in hypothalamus and hippocampus of rats

BACKGROUND

Obesity is the result of the interaction of multiple variables, including the excessive increase of sugar-sweetened beverages consumption. Diets aimed to treat obesity have suggested the use of artificial sweeteners. However, recent evidence has shown several health deficits after intake of artificial sweeteners, including effects in neuronal activity. Therefore, the influence of artificial sweeteners consumption such as Splenda, on the expression of c-Fos and neuronal nuclear protein (NeuN) in hypothalamus and hippocampus remains to be determined.

OBJECTIVES

We investigated the effects on c-Fos or NeuN expression in hypothalamus and hippocampus of Splenda-treated rats.

METHODS

Splenda was diluted in water (25, 75 or 250 mg/100 mL) and orally given to rats during 2 weeks ad libitum. Next, animals were sacrificed by decapitation and brains were collected for analysis of c-Fos or NeuN immunoreactivity.

RESULTS

Consumption of Splenda provoked an inverted U-shaped dose-effect in c-Fos expression in ventromedial hypothalamic nucleus while similar findings were observed in dentate gyrus of hippocampus. In addition, NeuN immunoreactivity was enhanced in ventromedial hypothalamic nucleus at 25 or 75 mg/100 mL of Splenda intake whereas an opposite effect was observed at 250 mg/100 mL of artificial sweetener consumption. Lastly, NeuN positive neurons were increased in CA2/CA3 fields of hippocampus from Splenda-treated rats (25, 75 or 250 mg/100 mL).

CONCLUSION

Consuming Splenda induced effects in neuronal biomarkers expression. To our knowledge, this study is the first description of the impact of intake Splenda on c-Fos and NeuN immunoreactivity in hypothalamus and hippocampus in rats.