Autism Associated With Anti-NMDAR Encephalitis: Glutamate-Related Therapy

Single-locus and Haplotype Associations of GRIN2B Gene with Autism Spectrum Disorders and the Demographic and Clinical Characteristics of Patients in Guilan, Iran

Autism spectrum disorders (ASDs) are described as generalized developmental disorders, with an average age of onset of 36 months. Genetic and environmental factors may contribute to this multifactorial disorder. The present study aimed to investigate the association of three GRIN2B polymorphisms, including rs1019385, rs1024893, and rs3764028, with ASDs. Based on the results, there was a significant difference regarding the genotype frequency of rs3764028 polymorphism between the control and case (ASD) groups (P = 0.027). According to the recessive model, this variant was associated with ASDs (P = 0.23). None of the eight haplotype models with frequencies above 0.5 showed significant differences between the case and control groups in terms of allelic frequency. The present results showed that the rs376028 variant was directly related to the phenotypic symptoms of ASDs.

Retrospective Comparison of Patients Evaluated for Pediatric Autoimmune Encephalitis with Typical and Atypical Premorbid Neuropsychiatric Development

PURPOSE

Patients with neurodevelopmental disorders (NDD) (i.e. autism, developmental delay, early-onset psychiatric or seizure disorders) increasingly seek evaluation of new or exacerbated symptoms concerning for autoimmune encephalitis (AE). Clinical AE evaluation can be challenging in NDD patients with symptom overlap between anti-neuronal autoimmunity and baseline atypical neurodevelopment. This study sought to explore differences in AE features by neurodevelopmental status.

METHODS

This retrospective chart review included 67 children with typical development (TD) or NDD evaluated for AE at the authors' institution. AE diagnosis included seronegative AE or seropositive AE with anti-NMDAR or anti-GAD antibodies. Reported AE clinical domains, symptom onset acuity, and treatment response were compared between three groups: (1) TD children with AE (TD-AE, N = 24); (2) NDD children with AE (NDD-AE, N = 21); and (3) NDD children with a non-AE diagnosis following appropriate workup (NDD-nonAE, N = 22).

RESULTS

Children with AE had a greater number of reported clinical domains than non-AE children with NDD (p < 0.0001) regardless of baseline developmental status. There were no observed differences in reported domains between TD-AE and NDD-AE groups. Onset acuity differed across the three groups (p = 0.04). No treatment response differences were observed between groups.

CONCLUSION

NDD children with AE had a comparable number of reported clinical domains relative to TD children and a similar treatment response. NDD patients with AE had a greater number of reported clinical domains than their NDD peers without an AE diagnosis. These findings suggest that AE is a multi-domain process in both TD and NDD children.

Altered glutamate level and its association with working memory among patients with treatment-resistant schizophrenia (TRS): a proton magnetic resonance spectroscopy study

BACKGROUND

Treatment-resistant schizophrenia (TRS) and non-TRS may be associated with different dopaminergic and glutamatergic regulations. The concept of dysregulated glutamatergic concentrations in specific brain regions remains controversial. Herein, we aimed to assess (i) the distribution of the glutamatergic concentration in the brain, (ii) the association between working memory (WM) differences in TRS and non-TRS patients, and (iii) whether an alteration in the glutamate (Glu) level is associated with WM.

METHODS

The participants included 38 TRS patients, 35 non-TRS patients, and 19 healthy controls (HCs), all of whom underwent 1.5-Tesla proton magnetic resonance spectroscopy of anterior cingulate cortex (ACC) and medial prefrontal cortex (MPFC). The ratios of glutamatergic neurometabolites to N-acetylaspartate + N-acetyl aspartylglutamate (NAAx) were calculated. Cognitive function was assessed using the Wechsler Adult Intelligence Scales, 4th Edition, which included the working memory index (WMI).

RESULT

The TRS patients had a higher glutamate + glutamine (Glx)/NAAx ratio compared to the non-TRS patients and HCs in the ACC, but this was not significantly different in the MPFC. WM was negatively correlated with Glx/NAAx in the ACC among the non-TRS patients, but not in the TRS patients or HCs.

CONCLUSIONS

Our findings were consistent with most studies indicating that the glutamatergic concentration in the ACC plays important roles in the classification of TRS and cognition. Our results may provide potential evidence for predictors and treatment response biomarkers in TRS patients. Further research is needed to probe the value using the relationship between Glu and WM as a potential prognostic predictor of schizophrenia.

Targeting NMDA Receptors at the Neurovascular Unit: Past and Future Treatments for Central Nervous System Diseases

The excitatory neurotransmission of the central nervous system (CNS) mainly involves glutamate and its receptors, especially N-methyl-D-Aspartate receptors (NMDARs). These receptors have been extensively described on neurons and, more recently, also on other cell types. Nowadays, the study of their differential expression and function is taking a growing place in preclinical and clinical research. The diversity of NMDAR subtypes and their signaling pathways give rise to pleiotropic functions such as brain development, neuronal plasticity, maturation along with excitotoxicity, blood-brain barrier integrity, and inflammation. NMDARs have thus emerged as key targets for the treatment of neurological disorders. By their large extracellular regions and complex intracellular structures, NMDARs are modulated by a variety of endogenous and pharmacological compounds. Here, we will present an overview of NMDAR functions on neurons and other important cell types involved in the pathophysiology of neurodegenerative, neurovascular, mental, autoimmune, and neurodevelopmental diseases. We will then discuss past and future development of NMDAR targeting drugs, including innovative and promising new approaches.

Evaluation of memantine's efficacy and safety in the treatment of children with autism spectrum disorder: A systematic review and meta-analysis

BACKGROUND

The United States Food and Drug Administration has approved drugs that address only autism-related symptoms rather than the underlying impairments. N-Methyl-D-Aspartate  receptor antagonists have recently emerged as a promising treatment option for a variety of neurologic and developmental problems, including autism.

AIMS

To review (systematically), for the first time, the medical literature that explores the safety in and efficacy of memantine in autism.

METHODS AND PROCEDURES

A comprehensive electronic search for relevant randomized controlled trials was conducted in four databases. Using RevMan software, we extracted and pooled data as a risk ratio (RR) or normalized mean differences in an inverse variance strategy.

RESULTS

This systematic review and meta-analysis includes five trials. There was no difference in enhancing social responsiveness when compared to placebo, though memantine lowered the likelihood of anxiety (RR = 0.25; 95% Confidence interval: [0.07; 0.87], p = 0.03). However, memantine aggravated impulsive behaviors. Additionally, in another trial that compared memantine added to risperidone versus risperidone added to placebo, memantine was found to be effective and safe.

CONCLUSION

Memantine showed safety in reducing acute symptoms of anxiety and other symptoms encountered in pediatric patients with autism spectrum disorders. However, memantine does not improve the core symptoms of autism. Nevertheless, further long-term trials are needed to explore its potential efficacy.

Sodium Benzoate—Harmfulness and Potential Use in Therapies for Disorders Related to the Nervous System: A Review

Currently, due to the large number of reports regarding the harmfulness of food additives, more and more consumers follow the so-called “clean label” trend, i.e., prefer and choose the least-processed food products. One of the compounds known as a preservative with a high safety profile is sodium benzoate. While some studies show that it can be used to treat conditions such as depression, pain, schizophrenia, autism spectrum disorders, and neurodegenerative diseases, others report its harmfulness. For example, it was found to cause mutagenic effects, generate oxidative stress, disrupt hormones, and reduce fertility. Due to such disparate results, the purpose of this study is to comprehensively discuss the safety profile of sodium benzoate and its potential use in neurodegenerative diseases, especially in autism spectrum disorder (ASD), schizophrenia, major depressive disorder (MDD), and pain relief.

C1q/TNF-related protein-1: Potential biomarker for early diagnosis of autism spectrum disorder

INTRODUCTION

Autism spectrum disorders (ASDs) are neurodevelopmental diseases characterized by communication inabilities, social interaction impairment, repetitive behavior, as well as learning problems. Although the exact mechanism underlying this disease is still obscure, researchers believe that several factors play a significant role in its development and pathogenesis. Some authors have reported an association between adipokines family and autism. C1q/TNF-related protein-1 (CTRP1) is a member of the adipokines family, and we hypothesized that this adipokine might have an influential role in the pathogenesis of ASDs. Since there is no specific marker for screening the disease, we evaluated CTRP1 as a potential marker for achieving this purpose.

METHODS

Blood samples were collected from 82 (41 ASDs boys, 41 healthy boys as controls) children aged 5-7 years old. CTRP1 gene expression and CTRP1 serum level were measured by quantitative realtime-PCR and enzyme-linked immunosorbent assay methods, respectively.

RESULTS

It was found that CTRP1 is significantly elevated in autistic children in comparison to healthy controls, both at the gene expression level, as well as at the serum level; demonstrating a good diagnostic value with a good range of sensitivity and specificity for detecting ASDs.

CONCLUSION

CTRP1 expression is elevated in ASDs boys aged 5-7 years old, suggesting a role for this adipokine in ASDs pathophysiology. Also, receiver operating characteristic curve analyses revealed that this adipokine could be utilized as a diagnostic biomarker for differentiating ASDs patients from healthy individuals along with other recently proposed biomarkers.

Common outcome, different pathways: Social information-processing deficits in autism spectrum disorder and attention-deficit/hyperactivity disorder

Social functioning is a key domain of impairment in both autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). This review adopts the social information-processing model as the theoretical framework to compare and contrast the deficits of ASD and ADHD at each of the six steps of social information-processing. Both disorders show deficits at each step, but the nature and origins of the deficits are different. Thus, while both disorders exhibit a common outcome of social impairment, the exact pathways that each disorder traverses along the six steps of social information-processing are different. For ASD, there is a social knowledge/behaviour deficit arising from difficulties in social/emotional cue detection, encoding, and interpretation, leading to problems in joining and initiating social interaction. For ADHD, there is a performance deficit incurred by disruption arising from the ADHD symptoms of inattention and hyperactivity/impulsivity, while its acquisition capacity on social knowledge is relatively intact. The inattentive, intrusive, and impulsive behaviours of ADHD unsettle social interaction. Finally, this review proposes training targets for intervention along the six steps of the social information-processing model for ASD and ADHD, as well as areas for future research in further elucidating the social impairment of the two disorders.

Age-dependent characteristics and prognostic factors of pediatric anti-N-methyl-d-aspartate receptor encephalitis in a Chinese single-center study

OBJECTIVE

To describe the clinical features and prognosis of pediatric anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis from a single center in northern China.

METHODS

The clinical and laboratory characteristics of hospitalized patients with anti-NMDAR encephalitis, stratified by age, were retrospectively studied. Risk factors including relapse and long-term (follow-up ≥1 year) outcomes were analyzed.

RESULTS

A total of 273 patients were included between November 2011 and December 2019, and the average age of onset was 7.5 ± 4.0 years (0.5-15.8 years). Of them, 159（58.2%） were female, and the proportion of females increased with age. Seizures were the most common initial symptom. Movement disorders（86.1%） and psychiatric（82.4%） symptoms were most frequent in the acute phase. In the acute stage, the incidence of movement disorders decreased with age (χ² = 10.676, p = 0.011), while the proportion of psychiatric symptoms increased with age (χ² = 21.85, p < 0.001) The recurrence rate was 9.6% (24/250). Demyelination was an independent risk factor for relapse (p = 0.006, OR = 5.877, 95% CI: 1.658-20.835). Among the 210 patients who were followed up for more than one year, 28 patients had a poor prognosis (mRS ≥3). Onset age (p = 0.038，OR = 0.844, 95% CI: 0.720-0.991), precursor of viral encephalitis (p = 0.007，OR = 9.876, 95% CI: 1.878-51.940), and ICU admission (p = 0.023，OR = 5.924, 95% CI: 1.280-27.064) significantly affected the prognosis. The mortality rate was 2.9%.

CONCLUSIONS

The characteristics of anti-NMDAR encephalitis in children are age-dependent. Early-onset, the precursor of viral encephalitis, and ICU admission may indicate poor prognosis. Demyelination may be a risk factor for recurrence.

Underrepresentation of Phenotypic Variability of 16p13.11 Microduplication Syndrome Assessed With an Online Self-Phenotyping Tool (Phenotypr): Cohort Study

Background

16p13.11 microduplication syndrome has a variable presentation and is characterized primarily by neurodevelopmental and physical phenotypes resulting from copy number variation at chromosome 16p13.11. Given its variability, there may be features that have not yet been reported. The goal of this study was to use a patient “self-phenotyping” survey to collect data directly from patients to further characterize the phenotypes of 16p13.11 microduplication syndrome.

Objective

This study aimed to (1) discover self-identified phenotypes in 16p13.11 microduplication syndrome that have been underrepresented in the scientific literature and (2) demonstrate that self-phenotyping tools are valuable sources of data for the medical and scientific communities.

Methods

As part of a large study to compare and evaluate patient self-phenotyping surveys, an online survey tool, Phenotypr, was developed for patients with rare disorders to self-report phenotypes. Participants with 16p13.11 microduplication syndrome were recruited through the Boston Children's Hospital 16p13.11 Registry. Either the caregiver, parent, or legal guardian of an affected child or the affected person (if aged 18 years or above) completed the survey. Results were securely transferred to a Research Electronic Data Capture database and aggregated for analysis.

Results

A total of 19 participants enrolled in the study. Notably, among the 19 participants, aggression and anxiety were mentioned by 3 (16%) and 4 (21%) participants, respectively, which is an increase over the numbers in previously published literature. Additionally, among the 19 participants, 3 (16%) had asthma and 2 (11%) had other immunological disorders, both of which have not been previously described in the syndrome.

Conclusions

Several phenotypes might be underrepresented in the previous 16p13.11 microduplication literature, and new possible phenotypes have been identified. Whenever possible, patients should continue to be referenced as a source of complete phenotyping data on their condition. Self-phenotyping may lead to a better understanding of the prevalence of phenotypes in genetic disorders and may identify previously unreported phenotypes.

Rapid effects of neurosteroids on neuronal plasticity and their physiological and pathological implications

Current neuroscience research on neurosteroids and their synthetic analogues - neuroactive steroids - clearly demonstrate their drug likeness in a variety of neurological and psychiatric conditions. Moreover, research on neurosteroids continues to provide novel mechanistic insights into receptor activation or inhibition of various receptors. This mini-review will provide a high-level overview of the research area and discuss the various classes of potential physiological and pathological implications discovered so far.

Dysfunctional d-aspartate metabolism in BTBR mouse model of idiopathic autism

BACKGROUND

Autism spectrum disorders (ASD) comprise a heterogeneous group of neurodevelopmental conditions characterized by impairment in social interaction, deviance in communication, and repetitive behaviors. Dysfunctional ionotropic NMDA and AMPA receptors, and metabotropic glutamate receptor 5 activity at excitatory synapses has been recently linked to multiple forms of ASD. Despite emerging evidence showing that d-aspartate and d-serine are important neuromodulators of glutamatergic transmission, no systematic investigation on the occurrence of these D-amino acids in preclinical ASD models has been carried out.

METHODS

Through HPLC and qPCR analyses we investigated d-aspartate and d-serine metabolism in the brain and serum of four ASD mouse models. These include BTBR mice, an idiopathic model of ASD, and Cntnap2^-/-, Shank3^-/-, and 16p11.2^+/- mice, three established genetic mouse lines recapitulating high confidence ASD-associated mutations.

RESULTS

Biochemical and gene expression mapping in Cntnap2^-/-, Shank3^-/-, and 16p11.2^+/- failed to find gross cerebral and serum alterations in d-aspartate and d-serine metabolism. Conversely, we found a striking and stereoselective increased d-aspartate content in the prefrontal cortex, hippocampus and serum of inbred BTBR mice. Consistent with biochemical assessments, in the same brain areas we also found a robust reduction in mRNA levels of d-aspartate oxidase, encoding the enzyme responsible for d-aspartate catabolism.

CONCLUSIONS

Our results demonstrated the presence of disrupted d-aspartate metabolism in a widely used animal model of idiopathic ASD.

GENERAL SIGNIFICANCE

Overall, this work calls for a deeper investigation of D-amino acids in the etiopathology of ASD and related developmental disorders.

Anti-N-methyl-D-aspartate-receptor antibody encephalitis combined with syphilis: A case report

BACKGROUND

Anti-N-methyl-D-aspartate-receptor (NMDAR) encephalitis is a common type of autoimmune encephalitis characterized by complex clinical signs and variable imaging manifestations. The pathogenesis of the disease is unclear. Syphilis is an infectious disease caused by Treponema pallidum that can invade the nervous and immune systems and cause systemic symptoms. There are few reports of anti-NMDAR encephalitis with syphilis, and the association between them is unknown; both diseases are related to immune system damage. We report a case of anti-NMDAR encephalitis with syphilis.

CASE SUMMARY

A 32-year-old man was admitted to our hospital with complaints of cognitive decline, diplopia, and walking instability during the previous 6 mo. He developed dysarthria, difficulty swallowing, and involuntary shaking of his head, neck, and limbs during the month prior to presentation. Cranial magnetic resonance imaging showed symmetrical abnormal signals in the pons, midbrain, and bilateral basal ganglia, and inflammatory demyelination was considered. The diagnosis of syphilis was confirmed based on the syphilis diagnosis test and the syphilis rapid test. He was given anti-syphilis treatment, but the above symptoms gradually worsened. Anti-NMDAR antibody was positive in cerebrospinal fluid but was negative in serum. Due to the cerebrospinal fluid findings, anti-NMDAR encephalitis was a consideration. According to the patient’s weight, he was treated with intravenous methylprednisolone 1 g QD for 5 d, with the dose gradually decreased for 6 mo, and immunoglobulin 25 g QD for 5 d; his symptoms improved after treatment.

CONCLUSION

This case shows that anti-NMDAR encephalitis may be combined with syphilis, which should be recognized to avoid misdiagnosis and treatment delay.

Can Maternal Autoantibodies Play an Etiological Role in ASD Development?

Autism spectrum disorder (ASD) is a heterogeneous condition with multiple etiologies and risk factors - both genetic and environmental. Recent data demonstrate that the immune system plays an important role in prenatal brain development. Deregulation of the immune system during embryonic development can lead to neurodevelopmental changes resulting in ASD. One of the potential etiologic factors in the development of ASD has been identified as the presence of maternal autoantibodies targeting fetal brain proteins. The type of ASD associated with the presence of maternal autoantibodies has been referred to as maternal antibodies related to ASD (MAR ASD). The link between maternal autoantibodies and ASD has been demonstrated in both clinical studies and animal models, but the exact mechanism of their action in the pathogenesis of ASD has not been clarified yet. Several protein targets of ASD-related maternal autoantibodies have been identified. Here, we discuss the role of microtubule-associated proteins of the collapsin response mediator protein (CRMP) family in neurodevelopment and ASD. CRMPs have been shown to integrate multiple signaling cascades regulating neuron growth, guidance or migration. Their targeting by maternal autoantibodies could change CRMP levels or distribution in the developing nervous system, leading to defects in axon growth/guidance, cortical migration, or dendritic projection, which could play an etiological role in ASD development. In addition, we discuss the future possibilities of MAR ASD treatment.

NMDAR PAMs: Multiple Chemotypes for Multiple Binding Sites

The N-methyl-D-aspartate receptor (NMDAR) is a member of the ionotropic glutamate receptor (iGluR) family that plays a crucial role in brain signalling and development. NMDARs are nonselective cation channels that are involved with the propagation of excitatory neurotransmission signals with important effects on synaptic plasticity. NMDARs are functionally and structurally complex receptors, they exist as a family of subtypes each with its own unique pharmacological properties. Their implication in a variety of neurological and psychiatric conditions means they have been a focus of research for many decades. Disruption of NMDAR-related signalling is known to adversely affect higherorder cognitive functions (e.g. learning and memory) and the search for molecules that can recover (or even enhance) receptor output is a current strategy for CNS drug discovery. A number of positive allosteric modulators (PAMs) that specifically attempt to overcome NMDAR hypofunction have been discovered. They include various chemotypes that have been found to bind to several different binding sites within the receptor. The heterogeneity of chemotype, binding site and NMDAR subtype provide a broad landscape of ongoing opportunities to uncover new features of NMDAR pharmacology. Research on NMDARs continues to provide novel mechanistic insights into receptor activation and this review will provide a high-level overview of the research area and discuss the various chemical classes of PAMs discovered so far.