Exenatide, a GLP-1 analog, has healing effects on LPS-induced autism model: Inflammation, oxidative stress, gliosis, cerebral GABA, and serotonin interactions

Sex shapes gut-microbiota-brain communication and disease

Research into the microbiota-gut-brain axis (MGBA) has entered a golden age, raising the hope that therapeutics acting on it may offer breakthroughs in the treatment of many illnesses. However, most of this work overlooks a fundamental, yet understudied, biological variable: sex. Sex differences exist at every level of the MGBA. Sex steroids shape the structure of the gut microbiota, and these microbes in turn regulate levels of bioactive sex steroids. These hormones and microbes act on gut sensory enteroendocrine cells, which modulate downstream activity in the enteric nervous system, vagus nerve, and brain. We examine recent advances in this field, and discuss the scientific and moral imperative to include females in biomedical research, using autism spectrum disorder (ASD) as an example.

The impact of maternal immune activation on GABAergic interneuron development: A systematic review of rodent studies and their translational implications

Mothers exposed to infections during pregnancy disproportionally birth children who develop autism and schizophrenia, disorders associated with altered GABAergic function. The maternal immune activation (MIA) model recapitulates this risk factor, with many studies also reporting disruptions to GABAergic interneuron expression, protein, cellular density and function. However, it is unclear if there are species, sex, age, region, or GABAergic subtype specific vulnerabilities to MIA. Furthermore, to fully comprehend the impact of MIA on the GABAergic system a synthesised account of molecular, cellular, electrophysiological and behavioural findings was required. To this end we conducted a systematic review of GABAergic interneuron changes in the MIA model, focusing on the prefrontal cortex and hippocampus. We reviewed 102 articles that revealed robust changes in a number of GABAergic markers that present as gestationally-specific, region-specific and sometimes sex-specific. Disruptions to GABAergic markers coincided with distinct behavioural phenotypes, including memory, sensorimotor gating, anxiety, and sociability. Findings suggest the MIA model is a valid tool for testing novel therapeutics designed to recover GABAergic function and associated behaviour.

Centrally administered GLP-1 analogue improves intestinal barrier function through the brain orexin and the vagal pathway in rats

Leaky gut, an altered intestinal barrier function, has been described in many diseases such as irritable bowel syndrome (IBS). We have recently demonstrated that orexin in the brain blocked leaky gut in rats, suggesting that the brain plays a role in regulation of intestinal barrier function. In the present study, we tried to clarify whether GLP-1 acts centrally in the brain to regulate intestinal barrier function and its mechanism. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Intracisternal injection of GLP-1 analogue, liraglutide dose-dependently abolished increased colonic permeability in response to lipopolysaccharide. Either atropine or surgical vagotomy blocked the central GLP-1-induced improvement of colonic hyperpermeability. Intracisternal GLP-1 receptor antagonist, exendin (9-39) prevented the central GLP-1-induced blockade of colonic hyperpermeability. In addition, intracisternal injection of orexin receptor antagonist, SB-334867 blocked the GLP-1-induced improvement of intestinal barrier function. On the other hand, subcutaneous liraglutide also improved leaky gut but larger doses of liraglutide were needed to block it. In addition, neither atropine nor vagotomy blocked subcutaneous liraglutide-induced improvement of leaky gut, suggesting that central or peripheral GLP-1 system works separately to improve leaky gut in a vagal-dependent or independent manner, respectively. These results suggest that GLP-1 acts centrally in the brain to reduce colonic hyperpermeability. Brain orexin signaling and the vagal cholinergic pathway play a vital role in the process. We would therefore suggest that activation of central GLP-1 signaling may be useful for leaky gut-related diseases such as IBS.

Maternal Immune Activation Induced by Prenatal Lipopolysaccharide Exposure Leads to Long-Lasting Autistic-like Social, Cognitive and Immune Alterations in Male Wistar Rats

Several studies have supported the association between maternal immune activation (MIA) caused by exposure to pathogens or inflammation during critical periods of gestation and an increased susceptibility to the development of various psychiatric and neurological disorders, including autism and other neurodevelopmental disorders (NDDs), in the offspring. In the present work, we aimed to provide extensive characterization of the short- and long-term consequences of MIA in the offspring, both at the behavioral and immunological level. To this end, we exposed Wistar rat dams to Lipopolysaccharide and tested the infant, adolescent and adult offspring across several behavioral domains relevant to human psychopathological traits. Furthermore, we also measured plasmatic inflammatory markers both at adolescence and adulthood. Our results support the hypothesis of a deleterious impact of MIA on the neurobehavioral development of the offspring: we found deficits in the communicative, social and cognitive domains, together with stereotypic-like behaviors and an altered inflammatory profile at the systemic level. Although the precise mechanisms underlying the role of neuroinflammatory states in neurodevelopment need to be clarified, this study contributes to a better understanding of the impact of MIA on the risk of developing behavioral deficits and psychiatric illness in the offspring.

Probiotics and prebiotics alleviate behavioral deficits, inflammatory response, and gut dysbiosis in prenatal VPA-induced rodent model of autism

Autism spectrum disorders are neuropsychiatric conditions characterized by social interaction and communication disorders and repetitive stereotypical behaviors. These disorders are also accompanied by an inflammatory status. Bidirectional communication between microbiome, gut, and brain has been discovered as a major mechanism influencing core symptoms and biomarkers of autism. Therefore, the modulation of the gut microbiota in autism has recently attracted interest. In this study, probiotic- and prebiotic-mediated modulation of the gut microbiota was compared in terms of different symptoms and findings in an experimental autism model. Valproic acid (VPA) (500 mg/kg) was administered to Wistar rats (on prenatal day 12.5) to induce autistic-like behaviors. Based on the supply of probiotics and prebiotics, animals were grouped as control (saline), autistic-like (prenatal VPA), probiotic (prenatal VPA + 22.5 × 10⁹ cfu/day probiotic), prebiotic (prenatal VPA + 100 mg/day prebiotic), and combined treatment (prenatal VPA + 22.5 × 10⁹ cfu/day probiotic + 100 mg/day prebiotic). After the treatment process, behavioral tests (social behaviors, anxiety, stereotypical behavior, sensorimotor gating, and behavioral despair) and biochemical analyses (serum and brain tissue) were conducted, and the quantities of some phyla and genera were determined in stool samples. Significant positive effects of probiotic and combined treatments were observed on the sociability, social interaction, and anxiety parameters. In addition, all three treatments had positive effects on stereotypical behavior. However, the treatments did not affect sensorimotor gating deficits and behavioral despair. Further, probiotic treatment reversed the VPA-induced increase and decrease in serum IL-6 and IL-10 levels, respectively. Combined treatment also significantly increased the IL-10 levels. Prenatal VPA exposure decreased 5-hydroxytryptamine (5-HT) levels in the prefrontal cortex of the brain; however, combined treatment reversed this decrease. Prenatal VPA exposure also caused a decrease in Bacteroidetes/Firmicutes ratio in the gut microbiota, while the probiotic treatment significantly increased this ratio. These findings indicate that probiotic- and prebiotic-mediated microbial modulation may represent a new therapeutic approach to alleviate autistic-like symptoms.

Trends in Gliosis in Obesity, and the Role of Antioxidants as a Therapeutic Alternative

Obesity remains a global health problem. Chronic low-grade inflammation in this pathology has been related to comorbidities such as cognitive alterations that, in the long term, can lead to neurodegenerative diseases. Neuroinflammation or gliosis in patients with obesity and type 2 diabetes mellitus has been related to the effect of adipokines, high lipid levels and glucose, which increase the production of free radicals. Cerebral gliosis can be a risk factor for developing neurodegenerative diseases, and antioxidants could be an alternative for the prevention and treatment of neural comorbidities in obese patients.

AIM

Identify the immunological and oxidative stress mechanisms that produce gliosis in patients with obesity and propose antioxidants as an alternative to reducing neuroinflammation.

METHOD

Advanced searches were performed in scientific databases: PubMed, ProQuest, EBSCO, and the Science Citation index for research on the physiopathology of gliosis in obese patients and for the possible role of antioxidants in its management.

CONCLUSION

Patients with obesity can develop neuroinflammation, conditioned by various adipokines, excess lipids and glucose, which results in an increase in free radicals that must be neutralized with antioxidants to reduce gliosis and the risk of long-term neurodegeneration.

Protective role of IGF-1 and GLP-1 signaling activation in neurological dysfunctions

Insulin-like growth factor-1 (IGF-1), a pleiotropic polypeptide, plays an essential role in CNS development and maturation. Glucagon-like peptide-1 (GLP-1) is an endogenous incretin hormone that regulates blood glucose levels and fatty acid oxidation in the brain. GLP-1 also exhibits similar functions and growth factor-like properties to IGF-1, which is likely how it exerts its neuroprotective effects. Recent preclinical and clinical evidence indicate that IGF-1 and GLP-1, apart from regulating growth and development, prevent neuronal death mediated by amyloidogenesis, cerebral glucose deprivation, neuroinflammation and apoptosis through modulation of PI3/Akt kinase, mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK/ERK). IGF-1 resistance and GLP-1 deficiency impair protective cellular signaling mechanisms, contributing to the progression of neurodegenerative diseases. Over the past decades, IGF-1 and GLP-1 have emerged as an essential component of the neuronal system and as potential therapeutic targets for several neurodegenerative and neuropsychiatric dysfunctions. There is substantial evidence that IGF-1 and GLP-1 analogues penetrate the blood-brain barrier (BBB) and exhibit neuroprotective functions, including synaptic formation, neuronal plasticity, protein synthesis, and autophagy. Conclusively, this review represents the therapeutic potential of IGF-1 and GLP-1 signaling target activators in ameliorating neurological disorders.

The effect of glucagon like peptide-1 receptor agonist on behavioral despair and anxiety-like behavior in ovariectomized rats: Modulation of BDNF/CREB, Nrf2 and lipocalin 2

Ovariectomized (OVX) rodents show behavioral despair and anxiety-like behaviors. Glucagon-like peptide-1 receptor agonists (GLP-1RA) possess neuroprotective effects by reducing oxidative stress and neuroinflammation, thereby preventing synaptic loss. The objective of the present study is to evaluate the effect of GLP-1RA, namely liraglutide, on emotional behaviors, and to identify the level of oxidative stress, neuroinflammation, and BDNF signaling in the hippocampus of OVX rats. Forty female young Wistar rats were divided into 5 groups: Control, Control+liraglutide treated, OVX, OVX+fluoxetine, and OVX+liraglutide (150 µg/kg for 15 days, sc). Open field test and elevated plus-maze test were used to evaluate behaviors that are suggestive of anxiety. A forced swimming test was used to evaluate behavioral despair. At the end of the experiments, blood glucose level and body weight gain were measured. The levels of BDNF, CREB, Nrf2, and lipocalin 2 in the hippocampal tissue were measured by ELISA. Malondialdehyde (MDA) and glutathione levels were also evaluated. Statistical analysis was conducted through ANOVA and Bonferroni tests. Seven weeks post-OVX rats exhibited high anxiety related behavior and behavioral despair in comparison with the control groups. These behavioral changes were associated with increased lipocalin 2 and MDA levels in rats. Moreover, BDNF, CREB, and Nrf2 levels decreased significantly in the hippocampus of OVX rats. Liraglutide treatment limited the reduction of BDNF and Nrf2 levels in the hippocampus, maintaining them at the control levels. Liraglutide treatment also prevented the symptoms of behavioral despair and anxiety related behavior. As the main finding of the study GLP-1RA reduced behavioral despair and anxiety level and this may be related to the preservation of BDNF/Nrf2 levels and the decrease in oxidative stress and lipocalin 2 levels in the hippocampus.

Granulocyte Colony-Stimulating Factor Has a Sex-Dependent Positive Effect in the Maternal Immune Activation-Induced Autism Model

OBJECTIVE

The medical intervention for autism spectrum disorder (ASD) is restricted to ameliorating comorbid situations. Granulocyte colony-stimulating factor (G-CSF) is a growth factor that enhances the proliferation, differentiation and survival of hematopoietic progenitor cells. In the present study, we aimed to investigate the effects of G-CSF in a maternal immune activation-induced autism model.

METHODS

Sixteen female and 6 male Wistar adult rats were included in the study. After 21 days, forty-eight littermates (8 male controls, 8 female controls, 16 male lipopolysaccharide (LPS)-exposed rats and 16 female LPS-exposed rats) were divided into groups. Sixteen male LPS-exposed and 16 female LPS-exposed rats were divided into saline and G-CSF treatment groups.

RESULTS

In male rats, the LPS-exposed group was found to have significantly higher levels of TNF-α, IL-2, and IL-17 than the LPS-exposed G-CSF group. Levels of nerve growth factor, brain PSD-95 and brain GAD67 were higher in the LPS-exposed G-CSF group than in the LPS-exposed group in male rats. In female rats, brain NGF levels were similar between groups. There was no difference between groups in terms of brain GAD 67 levels. Brain PSD-95 levels were higher in the control group than in both the LPS-exposed and LPS-exposed G-CSF groups in female rats. Both neuronal CA1 and neuronal CA2 levels were lower, and the GFAP immunostaining index (CA1) and GFAP immunostaining index (CA3) were higher in the LPS-exposed group than in the LPS-exposed G-CSF group in male rats. However, neuronal count CA1 and Neuronal count CA3 values were found to be similar between groups in female rats.

CONCLUSIONS

The present research is the first to demonstrate the beneficial effects of G-CSF on core symptoms of ASD experimentally depending on male sex. G-CSF can be a good candidate for ameliorating the core symptoms of ASD without serious side effects in males.

Demonstration of Ameliorating Effect of Vardenafil Through Its Anti-Inflammatory and Neuroprotective Properties in Autism Spectrum Disorder Induced by Propionic Acid on Rat Model

Introduction: Autism spectrum disorder (ASD) is a neurodevelopmental disorder with complex etiology. In this study, we aimed to determine the ameliorating effects of vardenafil in the ASD rat model induced by propionic acid (PPA) in terms of neurobehavioral changes and also support these effects with histopathological changes, brain biochemical analysis and magnetic resonance spectroscopy (MRS) findings.Materials and Methods: Twenty-one male rats were randomly assigned into 3 groups. Group 1 (control, 7 rats) did not receive treatment. Rats in groups 2 and 3 were given PPA at the dose of 250 mg/kg/day intraperitoneally for 5 days. After PPA administration, animals in group 2 (PPAS, 7 rats) were given saline and animals in group 3 (PPAV, 7 rats) were given vardenafil. Behavioral tests were performed between the 20th and 24th days of the study. The rats were taken for MRS on the 25^th day. At the end of the study, brain levels of interleukin-2 (IL-2), IL-17, tumor necrosis factor-α, nerve growth factor, cGMP and lactate levels were measured. In the cerebellum and the CA1 and CA3 regions of the hippocampus, counts of neurons and Purkinje cells and glial fibrillary acidic protein (associated with gliosis) were evaluated histologically.Results: Three chamber sociability and passive avoiding test, histopathological results, lactate levels derived from MRS, and biochemical biomarkers revealed significant differences among the PPAV and PPAS groups.Conclusion: We concluded that vardenafil improves memory and social behaviors and prevent loss of neuronal and Purkinje cell through its anti-inflammatory and neuroprotective effect.

The effect of sulfasalazine in pentylenetetrazole-induced seizures in rats

We aimed to reveal the anti-convulsant effects sulfasalazine and its mechanism in pentylenetetrazole (PTZ)-induced seizures in rats. Forty-eight male Wistar albino rats (200-250 g) were randomly divided into two groups: 24 for electroencephalography (EEG) recording (group A) and 24 for behavioral studies (group B). About 70 mg/kg PTZ was used for behavioral studies after sulfasalazine administration and 35 mg/kg PTZ was used for EEG recording after sulfasalazine administration. Electrodes were implanted on the dura mater over the left frontal cortex and the reference electrode was implanted over the cerebellum for EEG recording. Racine's convulsion scale, first myoclonic jerk onset time, spike percentages, brain malondialdehyde (MDA), superoxide dismutase (SOD), and prostaglandin F2α (PGF2α) levels were evaluated between the groups. First myoclonic jerk onset time was significantly shorter in the saline group than both 250 and 500 mg/kg sulfasalazine groups (P<0.05). Racine's convulsion scores were significantly lower in the 250 and 500 mg/kg sulfasalazine groups than the saline group (P<0.05, P<0.001). The two sulfasalazine groups had lower spike percentages than the saline group (P<0.05). Significantly lower MDA and PGF2α levels were observed in the 250 and 500 mg/kg sulfasalazine groups compared with the saline group (P<0.05, P<0.001, respectively). SOD increased significantly in both sulfasalazine groups compared with the PTZ+saline group (P<0.05). Our study demonstrated that sulfasalazine had protective effects on PTZ-induced convulsions by protecting against oxidative and inflammatory damage associated with PTZ.

Microglia and BDNF at the crossroads of stressor related disorders: Towards a unique trophic phenotype

Stressors ranging from psychogenic/social to neurogenic/injury to systemic/microbial can impact microglial inflammatory processes, but less is known regarding their effects on trophic properties of microglia. Recent studies do suggest that microglia can modulate neuronal plasticity, possibly through brain derived neurotrophic factor (BDNF). This is particularly important given the link between BDNF and neuropsychiatric and neurodegenerative pathology. We posit that certain activated states of microglia play a role in maintaining the delicate balance of BDNF release onto neuronal synapses. This focused review will address how different "activators" influence the expression and release of microglial BDNF and address the question of tropomyosin receptor kinase B (TrkB) expression on microglia. We will then assess sex-based differences in microglial function and BDNF expression, and how microglia are involved in the stress response and related disorders such as depression. Drawing on research from a variety of other disorders, we will highlight challenges and opportunities for modulators that can shift microglia to a "trophic" phenotype with a view to potential therapeutics relevant for stressor-related disorders.