Search

The mechanisms underlying selective serotonin reuptake inhibitor (SSRI) use during pregnancy as a major autism risk factor are unclear. Here, brain neurochemical changes following fluoxetine exposure and in an autism model were compared to determine the effects on autism risk. The study was performed on neonatal male western albino rats which were divided into Groups one (control), two (propionic acid [PPA]-induced autism model), and three (prenatal SSRI-exposed newborn rats whose mothers were exposed to 5 mg/kg of fluoxetine over gestation days 10–20). SSRI (fluoxetine) induced significant neurochemical abnormalities in the rat brain by increasing lipid peroxide (MDA), Interferon-gamma (IFN-γ), and caspase-3 levels and by depleting Glutathione (GSH), Glutathione S-transferases (GST), Catalase, potassium (K+), and Creatine kinase (CK) levels, similarly to what has been discovered in the PPA model of autism when compared with control. Prenatal fluoxetine exposure plays a significant role in asset brain damage in newborns; further investigation of fluoxetine as an autism risk factor is thus warranted.

The present study investigated that maternal type 1 diabetes may contribute to autism pathogenesis in offspring, and that insulin therapy during pregnancy may prevent the onset of autism. As evidenced, selected brain biomarkers representing the accepted etiological mechanism of autism in newborn rats from diabetic mothers and diabetic mothers receiving insulin therapy compared to the propionic acid (PPA) rodent model of autism were screened. Female Wistar rats with a controlled fertility cycle were randomly divided into three groups: a control group, a group treated with a single dose of 65 mg/kg streptozotocin (STZ) to induce type 1 diabetes (T1D), and a group treated with a single dose of STZ to induce T1D along with insulin therapy. Neonatal rats from these groups were divided into four experimental groups of six animals each: the control group, oral buffered PPA-treated group administered a neurotoxic dose of 250 mg/kg PPA for 3 days to induce autism, neonatal rats from mothers with T1D, and neonatal rats from mothers with T1D receiving insulin therapy. Biochemical parameters of oxidative stress, neuroinflammation, and glutamate excitotoxicity were examined in brain homogenates from all neonatal rats. The development of pathogenic bacteria was monitored in stool samples from all rat groups. Descriptive analyses of changes in fecal microbiota and overgrowth of Clostridium species were performed in diabetic mothers, diabetic mothers treated with insulin therapy, and their offspring. Clostridium species may induce autism-relevant behaviors in offspring from mothers with T1D. Maternal T1D without insulin therapy increased lipid peroxidation levels, reduced GST activity, and lower offspring’ vitamin C and GSH levels. Increased IL-6 levels and reduced GABA levels were detected in brain homogenates from neonatal rats whose mothers had T1D. Interestingly, insulin therapy reduced MDA and IL-6 levels and increased GST, GSH, and vitamin C levels in brain homogenates of neonatal rats from mothers with T1D receiving insulin therapy compared to the PPA-treated group. Based on our results, the PPA-treated group and neonatal rats from mothers with T1D exhibited similar results. These findings suggest that neonatal rats from mothers with T1D may develop autism-relevant biochemical autistic features and that insulin therapy may ameliorate oxidative stress, poor detoxification, inflammation, and excitotoxicity as ascertained mechanisms involved in the etiology of autism.

Background: Lipid homeostasis and gut flora can be related to many metabolic diseases, especially autism. Lipid metabolism in the brain can control neuronal structure and function and can also take part in signal transduction pathways to control metabolism in peripheral tissues, especially in the liver. Impaired phospholipid metabolism promotes oxidative stress and neuroinflammation and is, therefore, directly related to autism. Objective: The effect of propionic acid (PPA) toxicity on lipid homeostasis in the gut-liver-brain axis was evaluated to understand their inter-connection. Cytosolic phospholipase A2 (cPLA2) concentration and activity was measured in autistic model and protective role of omega-3 (ω-3) and vitamin B12 was evaluated. Methods: Animals were divided into five groups: Group I (control group); Group II (autistic model treated with neurotoxic dose of PPA); Group III (treated with vitamin B12 (16.7 mg/kg/day) for 30 days post PPA treatment); Group IV (treated with ω-3 (200 mg/kg body weight/day) for 30 days post PPA treatment; Group V (combined dose of ω-3 and Vitamin B12, for 30 days post PPA treatment). Phospholipase A2 activity and protein expression level in the liver homogenate of all the groups was analyzed by western blotting and was compared to brain cPLA2. Results: PPA increased the levels of liver and brain cPLA2. However, independent or combined treatment with ω-3 and vitamin B12 was effective in neutralizing its effect. Moreover, PPA-induced dysbiosis, which was ameliorated with the above treatments. Conclusions: This study showed the role of cPLA2 as a lipid metabolism marker, related to PPA-induced inflammation through a highly interactive gut-liver-brain axis.

Autism spectrum disorders (ASD) express as impaired social interactions and stereotypes. The gut microbiome which is remarkably different in ASD compared with controls may contribute to the sex bias of this disorder, with females being less vulnerable to clinically present autism. This review aims to understand the role of gut microbiota and female sex hormone in the sex bias of autism. Recent evidence proved that transplanted gut microbiota from autistic donors but not healthy controls into germ-free mice were effective in inducing autistic features. Moreover selective probiotic known to be more abundant in females than males was effective as a treatment strategy. The higher autistic phenotypes in males compared with females could be attributed to the protective effect of estrogen, the higher diversity and predominance of probiotics in females, the lower liability of females to develop leaky gut, neuroinflammation, and excitotoxicity as etiological mechanisms.

The marked heterogeneity of autism spectrum disorders is a challenge for research into biomarkers of these disorders. The present study aimed to assess the association of the thioredoxin (TRX) system and vasopressin with autism in children. Thirty-five autistic children were recruited with thirty-one healthy controls children matched for age and gender. Total antioxidant capacity (TAC), vasopressin, peroxiredoxin (PRDX1, PRDX3), phox domain-containing protein kinase-like protein, and TRX1 levels were measured in plasma and mercury and lead levels were measured in red blood cells. Children with autism had significantly lower levels of PRDX1 and TRX1 and significantly higher levels of lead and mercury compared with controls. Significantly higher levels of vasopressin were also observed in more severe cases of autism. Receiver operating characteristics analysis demonstrated satisfactory specificity and sensitivity of TAC, PRDX1, PRDX3, and TRX1 for the diagnosis of autism. The optimal cut-off value for plasma TRX1 levels, as an indicator of autism, was 10.6 ng/mL. Significant positive correlations existed between TRX system components, lead, and mercury. A negative correlation was found between vasopressin and TRX1, but positive correlations were found between vasopressin and mercury and lead. In conclusion, TAC, PRDX1, PRDX3, and TRX1 may be useful biomarkers for the diagnosis of autism in Saudi populations. Vasopressin-resistance in autistic patients may be due to an increased oxidative burden.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by reduced social communication and repetitive behaviors. The etiological mechanisms of ASD are still unknown; however, the GABAergic system has received considerable attention due to its potential as a therapeutic target. Based on the fact that individuals with autism demonstrate altered gene expression concomitant with impaired blood brain barrier (BBB), and gut barrier integrities, so increased glutamate levels in the blood and platelets of ASD patients can be related to lower numbers of cerebellar GABAergic neurons, less active GABA-synthesizing enzymes, and decreased brain GABA levels. Excitotoxic levels of released glutamate trigger a cascade of deleterious cellular events leading to delayed neuronal death. According to our understanding of glutamate excitotoxicity, GABA supplementation could theoretically be useful to treat certain autistic phenotypes. While there is still no effective and safe medication for glutamate-related cell damage and death, combined efforts will hopefully develop better treatment options. Here I hypothesize that an integrated treatment strategy with GABA supplements, regulation of chloride (Cl-) and magnesium (Mg2+) levels, vitamin D supplements, probiotics to enhance GABAA receptor and glutamate decarboxylase (GAD) expression, and memantine to activate glutamate transporters and inhibit NMDA receptors, could collectively reduce glutamate levels, maintain functional GABA receptors and thus treat repetitive behavior, impaired social behavior, and seizure activity in individuals with autism.

It is proposed that gluten- and casein-rich diets (GRD and CRD) can synergistically exacerbate dysbiosis as comorbidity in autism by worsening leaky gut that affects the brain through the gut–brain axis. In this study, 35 young male rats were divided into 7 groups, Group 1 serves as control; Group 2, clindamycin (CL)-treated; and Group 3, propionic acid (PPA)-induced rodent model of autism. These three groups were fed standard diet until the end of the experiment. Groups 4–7 are rats treated similarly with CL and PPA, then fed on CRD or GRD until the end of the experiment. Serum zonulin, glutathione (GSH), lipid peroxides, and gut microbial composition were measured in the seven studied groups. Data demonstrate the significant increase in serum zonulin as marker of leaky gut in the CL-treated groups fed on CRD or GRD. Lipid peroxides were significantly higher in the serum of GRD-fed rats compared to CRD-fed or normal diet-fed rats. GSH was much lower in CL-treated groups fed on CRD or GRD compared to PPA-treated rats fed on both diets. Both diets differentially affected the diversity of the gut microbiota. This study demonstrates that CRD and GRD exacerbates leaky gut, according to serum zonulin, which was used as marker for increased gut permeability.

Background Innovative research highlighted the probable connection between autism spectrum disorder (ASD) and gut microbiota as many autistic individuals have gastrointestinal problems as co-morbidities. This review emphasizes the role of altered gut microbiota observed frequently in autistic patients, and the mechanisms through which such alterations may trigger leaky gut. Main body Different bacterial metabolite levels in the blood and urine of autistic children, such as short-chain fatty acids, lipopolysaccharides, beta-cresol, and bacterial toxins, were reviewed. Moreover, the importance of selected proteins, among which are calprotectin, zonulin, and lysozyme, were discussed as biomarkers for the early detection of leaky gut as an etiological mechanism of ASD through the less integrative gut–blood–brain barriers. Disrupted gut–blood–brain barriers can explain the leakage of bacterial metabolites in these patients. Conclusion Although the cause-to-effect relationship between ASD and altered gut microbiota is not yet well understood, this review shows that with the consumption of specific diets, definite probiotics may represent a noninvasive tool to reestablish healthy gut microbiota and stimulate gut health. The diagnostic and therapeutic value of intestinal proteins and bacterial-derived compounds as new possible biomarkers, as well as potential therapeutic targets, are discussed.

Autism is associated with gastrointestinal dysfunction and gut microbiota dysbiosis, including an overall increase in Clostridium. Modulation of the gut microbiota is suggested to improve autistic symptoms. In this study, we explored the implementation of two different interventions that target the microbiota in a rodent model of autism and their effects on social behavior: the levels of different fecal Clostridium spp., and hippocampal transcript levels. Autism was induced in young Sprague Dawley male rats using oral gavage of propionic acid (PPA) for three days, while controls received saline. PPA-treated animals were divided to receive either saline, fecal transplant from healthy donor rats, or Bifidobacterium for 22 days, while controls continued to receive saline. We found that PPA attenuated social interaction in animals, which was rescued by the two interventions. PPA-treated animals had a significantly increased abundance of fecal C. perfringens with a concomitant decrease in Clostridium cluster IV, and exhibited high hippocampal Bdnf expression compared to controls. Fecal microbiota transplantation or Bifidobacterium treatment restored the balance of fecal Clostridium spp. and normalized the level of Bdnf expression. These findings highlight the involvement of the gut–brain axis in the etiology of autism and propose possible interventions in a preclinical model of autism.

A high extracellular concentration of glutamate has the potential to induce autism. Presently no appropriate treatment is available to modulate glutamate-mediated injury; however, increased levels of glutamate transporters, which aid in glutamate clearance, may potentially limit and prevent glutamate excitotoxicity, and β-lactam antibiotics have been found to activate the expression of a glutamate transporter. To identify the beneficial role of β-lactam in autism, we used an animal model of autism by administrating propionic acid (PPA) to juvenile rats and then treated these animals with this antibiotic. Animals were divided into three groups: (1) an untreated control group, (2) a PPA-intoxicated group and (3) a PPA-intoxicated group treated with β-lactam. Selected parameters related to glutamate signaling were measured in brain homogenates of all groups. The obtained data demonstrated neurotoxicity of PPA through glutamate (GLU) excitotoxicity. Moreover, the rats treated with β-lactam exhibited higher glutamate transporter 1 (Glt-1) levels than the control group (p = 0.044). Furthermore, compared to the expression in the control group and the untreated autism model group, Glt-1 gene expression was much higher in brain samples from β-lactam-treated autism model rats (p < 0.056). Receiver operating characteristic (ROC) analyses revealed that measured parameters such as GLU and GLU/γ-aminobutyric acid, Glt-1, and GLU/Glt-1 were found to be predictive markers of the protective effect of β-lactam against GLU excitotoxicity. Immediate upregulation of Glt-1 may reduce extracellular GLU levels and thereby prevent damage to neurons. Therefore, increasing Glt-1 expression could be a potential approach to prevent excitotoxicity in the brain.

Autism, a neurodevelopmental disorder, is characterized by a high level of social interaction insufficiency, impairment in language, and repetitive behavior. The gut–brain axis (GBA) is considered a bidirectional communication pathway between the gut and the brain. Growing evidence shows that the GBA contributes to the etiology of autism. The phenotypic behaviors of autism and the gastrointestinal problems that are comorbidity in autism are associated with modified gut microbiota. Understanding the role of the gut microbiota in oxidative stress, heavy metal toxicity, glutamate excitotoxicity, impaired lipid metabolism, and neuroinflammation as pathological mechanisms of autism might support the use of nutritional and dietary interventions through the supplementation of probiotics for the amelioration of unhealthy perinatal and postnatal gut microbiota. This could lead to strategies to prevent, or at least control, autism through the correction of these pathological mechanisms. The aim of this chapter is to understand how autism is responsive to the composition of the gut microbiota, which can be targeted to treat this disorder.

The role of glutathione in autism spectrum disorder (ASD) is emerging as a major topic, due to its role in the maintenance of the intracellular redox balance. Several studies have implicated glutathione redox imbalance as a leading factor in ASD, and both ASD and many other neurodevelopmental disorders involve low levels of reduced glutathione (GSH), high levels of oxidized glutathione (GSSG), and abnormalities in the expressions of glutathione-related enzymes in the blood or brain. Glutathione metabolism, through its impact on redox environment or redox-independent mechanisms, interferes with multiple mechanisms involved in ASD pathogenesis. Glutathione-mediated regulation of glutamate receptors [e.g., N-methyl- d -aspartate (NMDA) receptor], as well as the role of glutamate as a substrate for glutathione synthesis, may be involved in the regulation of glutamate excitotoxicity. However, the interaction between glutathione and glutamate in the pathogenesis of brain diseases may vary from synergism to antagonism. Modulation of glutathione is also associated with regulation of redox-sensitive transcription factors nuclear factor kappa B (NF-κB) and activator protein 1 (AP-1) and downstream signaling (proinflammatory cytokines and inducible enzymes), thus providing a significant impact on neuroinflammation. Mitochondrial dysfunction, as well as neuronal apoptosis, may also provide a significant link between glutathione metabolism and ASD. Furthermore, it has been recently highlighted that glutathione can affect and modulate DNA methylation and epigenetics. Review analysis including research studies meeting the required criteria for analysis showed statistically significant differences between the plasma GSH and GSSG levels as well as GSH:GSSG ratio in autistic patients compared with healthy individuals (P = 0.0145, P = 0.0150 and P = 0.0202, respectively). Therefore, the existing data provide a strong background on the role of the glutathione system in ASD pathogenesis. Future research is necessary to investigate the role of glutathione redox signaling in ASD, which could potentially also lead to promising therapeutics.

Metabolites of proper fatty acids modulate the inflammatory response and are essential for normal brain development; equally, abnormal fatty acid metabolism plays a critical role in the pathology of autism. Currently, dietary supplements are often used to improve the core symptoms of Autism spectrum disorder (ASD). The present study analyzed the effects of orally supplemented omega-3 (ω-3) and vitamin B12 on ameliorating oxidative stress and impaired lipid metabolism in a propionic acid (PPA)-induced rodent model of autism, together with their effect on the gut microbial composition, where great fluctuations in the bacterial number and strains were observed; interestingly, polyunsaturated fatty acids such as omega-3 induced higher growth of the gram-positive bacterium Staphylococcus aureus and decreased the survival rates of Clostridia sp. as well as other enteric bacterial strains. Thirty-five young male western albino rats were divided into five equal groups. The first group served as the control; the second group was given an oral neurotoxic dose of PPA (250 mg/kg body weight/day) for 3 days. The third group received an oral dose of ω-3 (200 mg/kg body weight/day) for 30 days after the 3-day PPA treatment. Group four was given an oral dose of vitamin B12 (16.7 mg/kg/day) for 30 days after PPA treatment. Finally, group five was given a combination of both ω-3 and vitamin B12 at the same dose for the same duration after PPA treatment. Biochemical parameters related to oxidative stress and impaired fatty acid metabolism were investigated in the brain homogenates of each group. The effects of the dietary supplements on the gut microbiota were also observed. The PPA-treated autistic model expressed significantly higher levels of lipid peroxides and 5-lipoxygenase (5-LOX) and significantly less glutathione (GSH), glutathione S-transferase (GST), and cyclooxygenase 2 (COX2) than the control group. However, a remarkable amelioration of most of the impaired markers was observed with oral supplementation with ω-3 and vitamin B12, either alone or in combination. Our results concluded that impairment at various steps of the lipid metabolic pathways may contribute to the development of autism; however, supplementation with ω-3 and vitamin B12 can result in a positive therapeutic effect.

Autism spectrum disorder (ASD) is a multifactorial disorder caused by an interaction between environmental risk factors and a genetic background. It is characterized by impairment in communication, social interaction, repetitive behavior, and sensory processing. The etiology of ASD is still not fully understood, and the role of neuroinflammation in autism behaviors needs to be further investigated. The aim of the present study was to test the possible association between prostaglandin E2 (PGE2), cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-1 (mPGES-1), prostaglandin PGE2 EP2 receptors and nuclear kappa B (NF-κB) and the severity of cognitive disorders, social impairment, and sensory dysfunction. PGE2, COX-2, mPGES-1, PGE2-EP2 receptors and NF-κB as biochemical parameters related to neuroinflammation were determined in the plasma of 47 Saudi male patients with ASD, categorized as mild to moderate and severe as indicated by the Childhood Autism Rating Scale (CARS) or the Social Responsiveness Scale (SRS) or the Short Sensory Profile (SSP) and compared to 46 neurotypical controls. The data indicated that ASD patients have remarkably higher levels of the measured parameters compared to neurotypical controls, except for EP2 receptors that showed an opposite trend. While the measured parameter did not correlate with the severity of social and cognitive dysfunction, PGE2, COX-2, and mPGES-1 were remarkably associated with the dysfunction in sensory processing. NF-κB was significantly increased in relation to age. Based on the discussed data, the positive correlation between PGE2, COX-2, and mPGES-1 confirm the role of PGE2 pathway and neuroinflammation in the etiology of ASD, and the possibility of using PGE2, COX-2 and mPGES-1 as biomarkers of autism severity. NF-κB as inflammatory inducer showed an elevated level in plasma of ASD individuals. Receiver operating characteristic analysis together with predictiveness diagrams proved that the measured parameters could be used as predictive biomarkers of biochemical correlates to ASD.