Gastrointestinal alterations in autism spectrum disorder: What do we know?

Identifying understudied correlations between autism & phenotypic attributes in a large family dataset

BACKGROUND

Autism Spectrum Disorder (ASD), a neurodevelopmental condition marked by restricted, repetitive behaviors and social communication difficulties, is one of the fastest-growing pediatric behavioral health concerns in the United States. Long-term outcomes significantly improve with early intervention, but diagnosis and treatment are complicated by the large range of phenotypic presentations that can be moderated by identity factors like gender and culture. Many physical and behavioral characteristics associated with the autism phenotype are not included in the screening and diagnostic instruments used in research.

METHODS

We have built a multi-site registry of diverse families with children with autism to collect longitudinal data on their physical and behavioral attributes to study the heterogeneous autism phenotype. Our KidsFirst registry contains 6,951 participants (hereafter "children") from 4,120 families, 1,865 of which have more than one child. In addition to collecting standard clinical instruments such as the Social Communication Questionnaire (SCQ), we have collected information on the phenotypic attributes of hearing issues, noise sensitivity, vision challenges, irregular sleep, impaired motor skills, metabolic disorders, gastrointestinal (GI) problems, infections, seizures, and premature birth for both ASD and non-ASD children. After validating parent-reported diagnoses against SCQ scores, we analyzed the association of each attribute with the ASD diagnosis and the other attributes using a logistic regression model and permutation tests.

RESULTS

Noise sensitivity, impaired motor skills, irregular sleep, GI problems, infections, and seizures attributes were significantly associated with autism diagnosis. These attributes also share correlation structures amongst themselves, suggesting that groupings of attributes may help to define subtypes of autism.

LIMITATIONS

The attributes analyzed in this study are not a comprehensive list of suspected traits of autism. Parent-reported diagnoses may not always be accurate, although we validated diagnoses. Despite accounting for family structure in our experiments, the relationships between attributes and diagnosis are likely stronger in the general population because our "control" sample is comprised of biological siblings who may still possess subclinical autistic traits, given the heritability of autism.

CONCLUSIONS

A more expansive conceptualization of the autism phenotype is likely to be useful to both researchers and families for identifying a more targeted approach to intervention.

Shank3 mutation manifests in abnormal gastrointestinal morphology and function in mice

Background

Gastrointestinal (GI) comorbidities are common among those with Autism Spectrum Disorder (ASD), but their etiology is not well understood. This study aimed to characterize gastrointestinal morphology and function in Shank3B mutant mice, a common genetic model of ASD, to identify potential alterations to the GI tract that could underlie ASD-associated GI comorbidities.

Methods

GI and enteric nervous system morphology was characterized using Hematoxylin and Eosin staining and immunohistochemistry. GI permeability was measured using the FITC-Dextran paracellular permeability assay. Whole-GI tract motility time was measured in vivo using the carmine dye motility assay. Colonic contractions were characterized by tracking motility using an ex vivo motility assay.

Results

Homozygous knock-out (KO) Shank3B-/- mice exhibit significantly altered epithelial morphology and increased GI permeability. An increased myenteric plexus density and a higher number of HuC/D-expressing neurons in myenteric ganglia are observed in the colon of Shank3B-/- mice. These mice exhibit slowed whole-GI tract transit and reduced velocity and propagation length of colonic contractions. Compared to Shank3B-/- mice, heterozygous Shank3B+/- mice exhibit milder epithelial, neuronal, and functional alterations.

Conclusion

Shank3B-/- mice exhibit altered GI morphology and function, while Shank3B+/- mice exhibit a partial phenotype. These results indicate that Shank3, whose mutation is associated with ASD, is critical for function of the GI tract and its mutation may contribute to the etiology of GI comorbidities.

New perspectives on microbiome-dependent gut-brain pathways for the treatment of depression with gastrointestinal symptoms: from bench to bedside

Patients with depression are more likely to have chronic gastrointestinal (GI) symptoms than the general population, but such symptoms are considered only somatic symptoms of depression and lack special attention. There is a chronic lack of appropriate diagnosis and effective treatment for patients with depression accompanied by GI symptoms, and studying the association between depression and GI disorders (GIDs) is extremely important for clinical management. There is growing evidence that depression is closely related to the microbiota present in the GI tract, and the microbiota-gut-brain axis (MGBA) is creating a new perspective on the association between depression and GIDs. Identifying and treating GIDs would provide a key opportunity to prevent episodes of depression and may also improve the outcome of refractory depression. Current studies on depression and the microbially related gut-brain axis (GBA) lack a focus on GI function. In this review, we combine preclinical and clinical evidence to summarize the roles of the microbially regulated GBA in emotions and GI function, and summarize potential therapeutic strategies to provide a reference for the study of the pathomechanism and treatment of depression in combination with GI symptoms.

Genetic Variant Analyses Identify Novel Candidate Autism Risk Genes from a Highly Consanguineous Cohort of 104 Families from Oman

Deficits in social communication, restricted interests, and repetitive behaviours are hallmarks of autism spectrum disorder (ASD). Despite high genetic heritability, the majority of clinically diagnosed ASD cases have unknown genetic origins. We performed genome sequencing on mothers, fathers, and affected individuals from 104 families with ASD in Oman, a Middle Eastern country underrepresented in international genetic studies. This approach identified 48 novel candidate genes significantly associated with ASD in Oman. In particular, 35 of these genes have been previously implicated in neurodevelopmental disorders (NDDs) in other populations, underscoring the conserved genetic basis of ASD across ethnicities. Genetic variants within these candidate genes that would impact the encoded protein included 1 insertion, 4 frameshift, 6 splicing, 12 nonsense, and 67 missense changes. Notably, 61% of the SNVs were homozygous, suggesting a prominent recessive genetic architecture for ASD in this unique population. The scarcity of genetic studies on ASD in the Arabian Peninsula has impeded the understanding of the unique genetic landscape of ASD in this region. These findings help bridge this knowledge gap and provide valuable insights into the complex genetic basis of ASD in Oman.

Plasma vitamin levels and pathway analysis in boys with autism spectrum disorders

Abnormal feeding behaviors and inadequate nutrient intake of children with autism spectrum disorder (ASD) have been reported. This study aimed to examine the plasma vitamin status of boys with autism spectrum disorder (ASD) and to analyze the association between vitamin status and symptoms of ASD. A total of 45 boys with ASD (age = 3.25 ± 0.68 years) and 45 typically developing (TD) boys (age = 3.33 ± 0.66 years) were enrolled. The developmental levels were evaluated using the Gesell Developmental Schedules (GDS), the severity of ASD was evaluated using the Childhood Autism Rating Scale (CARS). The plasma vitamin levels were determined using metabolomics method. The Vitamin B1, nicotinamide, pyridoxamine dihydrochloride and Vitamin E were found to be significantly higher in the boys with ASD compared with those without ASD. In addition, no significant differences in vitamin metabolic pathways were found between the ASD group and the TD group.The nicotinamide and pyridoxamine dihydrochloride concentration were found to be negatively correlated with GDS score. In comparison with TD boys, the plasma vitamin concentration of ASD boys was not insufficient. Further studies are required to investigate whether it is necessary to use vitamin nutritional supplements in children with ASD.

Exploring the effect of diet programs on the behavior of Sudanese children with autism and the prevalence and association of gastrointestinal symptoms: a multi-center cross-sectional study

Background and aims

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social difficulties, speech and nonverbal communication issues, and restricted behaviors. Nutritional issues, such as food allergies and intolerances, can affect children with ASD. This study aimed to evaluate the impact of diet programs on ASD behavior and gastrointestinal symptoms, which would be considered as a starting point to increase the family's knowledge about how to practice healthy and suitable dieting for their children.

Materials and methods

The study was a cross-sectional observational study on 45 children with an autism spectrum disorder in four centers aged 2-18 in Khartoum state. Data was collected through an interview questionnaire, which included sociodemographic, diet, gastrointestinal, and behavioral assessments. The data was analyzed using SPSS to find the correlation between the various variables. Independent t-test, Analysis of Variance, and Mann-Whitney test were used in univariant analysis to assess the association between study variables, while multiple linear regression was used in multivariant analysis for the same purpose.

Results

The study involved a large number of children with autism spectrum disorder (ASD), with 80% being male and 73.3% being school-aged. Most had parents as guardians and 71.1% were in intermediate financial status. About 20% were overweight or obese, and 57.8% did not have a specific diet program. Food selectivity was prevalent, with 22.7% having allergies to milk and wheat. ASD children experienced vomiting, gastric reflux, abdominal pain, and changes in stool characteristics. A significant link was found between financial status, behavioral status and gastrointestinal changes. High financial status was significantly different from intermediate and low statuses based on behavioral changes. However, no significant association was found in multivariant analysis.

Conclusion

The study found that ASD children generally have good nutritional health, with a higher degree of dietary selection. The financial status of guardians significantly influenced behavioral and gastrointestinal changes in the children. Further interventional studies are recommended to assess the direct impact of diet programs on these symptoms.

Exploring Dietary Interventions in Autism Spectrum Disorder

Autism spectrum disorder (ASD) involves social communication difficulties and repetitive behaviors, and it has a growing prevalence worldwide. Symptoms include cognitive impairments, gastrointestinal (GI) issues, feeding difficulties, and psychological problems. A significant concern in ASD is food selectivity, leading to nutrient deficiencies. Common GI issues in ASD, such as constipation and irritable bowel syndrome, stem from abnormal gut flora and immune system dysregulation. Sensory sensitivities and behavioral challenges exacerbate these problems, correlating with neurological symptom severity. Children with ASD also exhibit higher oxidative stress due to low antioxidant levels like glutathione. Therapeutic diets, including ketogenic, high-antioxidant, gluten-free and casein-free, and probiotic-rich diets, show potential in managing ASD symptoms like behavior, communication, GI issues, and oxidative stress, though the evidence is limited. Various studies have focused on different populations, but there is increasing concern about the impact among children. This review aims to highlight the food preferences of the ASD population, analyze the effect of the physicochemical and nutritional properties of foods on the selectivity in its consumption, GI problems, and antioxidant deficiencies in individuals with ASD, and evaluate the effectiveness of therapeutic diets, including diets rich in antioxidants, gluten-free and casein-free, ketogenic and essential fatty acids, and probiotic-rich diets in managing these challenges.

Abnormal Porphyrin Metabolism in Autism Spectrum Disorder and Therapeutic Implications

Autism spectrum disorder (ASD) is a mosaic of neurodevelopmental conditions composed of early-onset social interaction and communication deficits, along with repetitive and/or restricted patterns of activities, behavior, and interests. ASD affects around 1% of children worldwide, with a male predominance. Energy, porphyrin, and neurotransmitter homeostasis are the key metabolic pathways affected by heavy metal exposure, potentially implicated in the pathogenesis of ASD. Exposure to heavy metals can lead to an altered porphyrin metabolism due to enzyme inhibition by heavy metals. Heavy metal exposure, inborn genetic susceptibility, and abnormal thiol and selenol metabolism may play a significant role in the urinary porphyrin profile anomalies observed in ASD. Altered porphyrin metabolism in ASD may also be associated with, vitamin B6 deficiency, hyperoxalemia, hyperhomocysteinemia, and hypomagnesemia. The present review considers the abnormal porphyrin metabolism in ASD in relation to the potential pathogenic mechanism and discusses the possible metabolic therapies such as vitamins, minerals, cofactors, and antioxidants that need to be explored in future research. Such targeted therapeutic therapies would bring about favorable outcomes such as improvements in core and co-occurring symptoms.

Reversal of Autism Symptoms among Dizygotic Twins through a Personalized Lifestyle and Environmental Modification Approach: A Case Report and Review of the Literature

The prevalence of autism has been increasing at an alarming rate. Even accounting for the expansion of autism spectrum disorder diagnostic (ASD) criteria throughout the 1990's, there has been an over 300% increase in ASD prevalence since the year 2000. The often debilitating personal, familial, and societal sequelae of autism are generally believed to be lifelong. However, there have been several encouraging case reports demonstrating the reversal of autism diagnoses, with a therapeutic focus on addressing the environmental and modifiable lifestyle factors believed to be largely underlying the condition. This case report describes the reversal of autism symptoms among dizygotic, female twin toddlers and provides a review of related literature describing associations between modifiable lifestyle factors, environmental exposures, and various clinical approaches to treating autism. The twins were diagnosed with Level 3 severity ASD "requiring very substantial support" at approximately 20 months of age following concerns of limited verbal and non-verbal communication, repetitive behaviors, rigidity around transitions, and extensive gastrointestinal symptoms, among other common symptoms. A parent-driven, multidisciplinary, therapeutic intervention involving a variety of licensed clinicians focusing primarily on addressing environmental and modifiable lifestyle factors was personalized to each of the twin's symptoms, labs, and other outcome measures. Dramatic improvements were noted within several months in most domains of the twins' symptoms, which manifested in reductions of Autism Treatment Evaluation Checklist (ATEC) scores from 76 to 32 in one of the twins and from 43 to 4 in the other twin. The improvement in symptoms and ATEC scores has remained relatively stable for six months at last assessment. While prospective studies are required, this case offers further encouraging evidence of ASD reversal through a personalized, multidisciplinary approach focusing predominantly on addressing modifiable environmental and lifestyle risk factors.

Gut-brain barrier dysfunction bridge autistic-like behavior in mouse model of maternal separation stress: A behavioral, histopathological, and molecular study

Autism spectrum disorder (ASD) is a fast-growing neurodevelopmental disorder throughout the world. Experiencing early life stresses (ELS) like maternal separation (MS) is associated with autistic-like behaviors. It has been proposed that disturbance in the gut-brain axis-mediated psychiatric disorders following MS. The role of disruption in the integrity of gut-brain barrier in ASD remains unclear. Addressing this knowledge gap, in this study we aimed to investigate role of the gut-brain barrier integrity in mediating autistic-like behaviors in mouse models of MS stress. To do this, mice neonates are separated daily from their mothers from postnatal day (PND) 2 to PND 14 for 3 hours. During PND58-60, behavioral tests related to autistic-like behaviors including three-chamber sociability, shuttle box, and resident-intruder tests were performed. Then, prefrontal cortex (PFC), hippocampus, and colon samples were dissected out for histopathological and molecular evaluations. Results showed that MS is associated with impaired sociability and social preference indexes, aggressive behaviors, and impaired passive avoidance memory. The gene expression of CLDN1 decreased in the colon, and the gene expression of CLDN5, CLDN12, and MMP9 increased in the PFC of the MS mice. MS is associated with decrease in the diameter of CA1 and CA3 areas of the hippocampus. In addition, MS led to histopathological changes in the colon. We concluded that, probably, disturbance in the gut-brain barrier integrities mediated the autistic-like behavior in MS stress in mice.

Western diet components that increase intestinal permeability with implications on health

Intestinal permeability is a physiological property that allows necessary molecules to enter the organism. This property is regulated by tight junction proteins located between intestinal epithelial cells. However, various factors can increase intestinal permeability (IIP), including diet. Specific components in the Western diet (WD), such as monosaccharides, fat, gluten, salt, alcohol, and additives, can affect the tight junctions between enterocytes, leading to increased permeability. This review explains how these components promote IIP and outlines their potential implications for health. In addition, we describe how a reduction in WD consumption may help improve dietary treatment of diseases associated with IIP. Research has shown that some of these components can cause changes in the gut microbiota, leading to dysbiosis, which can promote greater intestinal permeability and displacement of endotoxins into the bloodstream. These endotoxins include lipopolysaccharides derived from gram-negative bacteria, and their presence has been associated with various diseases, such as autoimmune, neurological, and metabolic diseases like diabetes and cardiovascular disease. Therefore, nutrition professionals should promote the reduction of WD consumption and consider the inclusion of healthy diet components as part of the nutritional treatment for diseases associated with increased intestinal permeability.

High-fat diet-induced obesity causes intestinal Th17/Treg imbalance that impairs the intestinal barrier and aggravates anxiety-like behavior in mice

The prevalence of autism spectrum disorders (ASD) has been steadily increasing, and growing evidence suggests a link between high-fat diet (HFD), obesity, and ASD; however, the mechanism underlying this association remains elusive. Herein, BTBR T + tf/J (BTBR) inbred mice (a mouse ASD model) and C57Bl/6J (C57) mice were fed an HFD and normal diet (ND) for 8 weeks (groups: C57 + ND, C57 + HFD, BTBR + ND, and BTBR + HFD). Subsequently, mice underwent behavioral assessments, followed by intestinal tissues harvesting to detect expression of intestinal barrier proteins and inflammatory factors and immune cell numbers, and a correlation analysis. HFD-fed BTBR mice developed obesity, elevated blood sugar, significantly aggravated anxiety-like behaviors, impaired intestinal barrier function, intestinal inflammation with elevated CD4+IL17+ T (Th17) cells and reduced CD4+Foxp3+ T (Treg) cells, exhibiting reduced expression of proteins related to AMPK regulatory pathway (AMPK, p-AMPK, SIRT1). Correlation analysis revealed that the degree of behavioral anxiety, the degree of intestinal barrier damage, the severity of intestinal inflammation, and the degree of immune cell imbalance positively correlated with each other. Accordingly, HFD-induced obesity may cause intestinal Th17/Treg imbalance via the AMPK-SIRT1 pathway, leading to an inflammatory environment in the intestine, impairing intestinal barrier function, and ultimately aggravating anxiety-like behaviors in mice.

Autism spectrum disorder: pathogenesis, biomarker, and intervention therapy

Autism spectrum disorder (ASD) has become a common neurodevelopmental disorder. The heterogeneity of ASD poses great challenges for its research and clinical translation. On the basis of reviewing the heterogeneity of ASD, this review systematically summarized the current status and progress of pathogenesis, diagnostic markers, and interventions for ASD. We provided an overview of the ASD molecular mechanisms identified by multi-omics studies and convergent mechanism in different genetic backgrounds. The comorbidities, mechanisms associated with important physiological and metabolic abnormalities (i.e., inflammation, immunity, oxidative stress, and mitochondrial dysfunction), and gut microbial disorder in ASD were reviewed. The non-targeted omics and targeting studies of diagnostic markers for ASD were also reviewed. Moreover, we summarized the progress and methods of behavioral and educational interventions, intervention methods related to technological devices, and research on medical interventions and potential drug targets. This review highlighted the application of high-throughput omics methods in ASD research and emphasized the importance of seeking homogeneity from heterogeneity and exploring the convergence of disease mechanisms, biomarkers, and intervention approaches, and proposes that taking into account individuality and commonality may be the key to achieve accurate diagnosis and treatment of ASD.

Prenatal caffeine exposure induces autism-like behaviors in offspring under a high-fat diet via the gut microbiota-IL-17A-brain axis

Prenatal caffeine exposure (PCE) is a significant contributor to intrauterine growth retardation (IUGR) in offspring, which has been linked to an increased susceptibility to autism spectrum disorder (ASD) later in life. Additionally, a high-fat diet (HFD) has been shown to exacerbate ASD-like behaviors, but the underlying mechanisms remain unclear. In this study, we first noted in the rat model of IUGR induced by PCE that male PCE offspring exhibited typical ASD-like behaviors post-birth, in contrast to their female counterparts. The female PCE offspring demonstrated only reduced abilities in free exploration and spatial memory. Importantly, both male and female PCE offspring displayed ASD-like behaviors when exposed to HFD. We further observed that PCE + HFD offspring exhibited damaged intestinal mucus barriers and disturbed gut microbiota, resulting in an increased abundance of Escherichia coli (E. coli). The induced differentiation of colonic Th17 cells by E. coli led to an increased secretion of IL-17A, which entered the hippocampus through peripheral circulation and caused synaptic damage in hippocampal neurons, ultimately resulting in ASD development. Our strain transplantation experiment suggested that E. coli-mediated increase of IL-17A may be the core mechanism of ASD with a fetal origin. In conclusion, PCE and HFD are potential risk factors for ASD, and E. coli-mediated IL-17A may play a crucial role in fetal-originated ASD through the gut-brain axis.

Identification of two novel autism genes, TRPC4 and SCFD2, in Qatar simplex families through exome sequencing

This study investigated the genetic underpinnings of autism spectrum disorder (ASD) in a Middle Eastern cohort in Qatar using exome sequencing. The study identified six candidate autism genes in independent simplex families, including both four known and two novel autosomal dominant and autosomal recessive genes associated with ASD. The variants consisted primarily of de novo and homozygous missense and splice variants. Multiple individuals displayed more than one candidate variant, suggesting the potential involvement of digenic or oligogenic models. These variants were absent in the Genome Aggregation Database (gnomAD) and exhibited extremely low frequencies in the local control population dataset. Two novel autism genes, TRPC4 and SCFD2, were discovered in two Qatari autism individuals. Furthermore, the D651A substitution in CLCN3 and the splice acceptor variant in DHX30 were identified as likely deleterious mutations. Protein modeling was utilized to evaluate the potential impact of three missense variants in DEAF1, CLCN3, and SCFD2 on their respective structures and functions, which strongly supported the pathogenic natures of these variants. The presence of multiple de novo mutations across trios underscored the significant contribution of de novo mutations to the genetic etiology of ASD. Functional assays and further investigations are necessary to confirm the pathogenicity of the identified genes and determine their significance in ASD. Overall, this study sheds light on the genetic factors underlying ASD in Qatar and highlights the importance of considering diverse populations in ASD research.

Comparative Assessment of Disturbances of Contractions of the Isolated Uterus in 3- and 9-Month-Old Rats with a Model of Autism

We performed a comparative study of the effects of carbachol, α,β-methylene-ATP, β,γ-methylene-ATP, and electric field stimulation on the contractile activity of the isolated uterus from rats aged 3 and 9 months with valproic model of autism. The contractile responses of isolated rat uterine preparations induced by P2X-receptor agonists α,β-methylene-ATP and β,γ-methylene-ATP were significantly lower than in the control. In addition, the contractions of the isolated uterus of 9-month-old rats induced by carbachol were significantly lower than in controls. No significant differences in uterine smooth muscle contractions in both age groups of rats induced by electric field stimulation in comparison with the control were found. Thus, significant impairment of uterine contractile activity was revealed in rats with valproic model of autism, which persisted up to the age of 9 months. The absence of changes in the contractions induced by electric field stimulation suggests that the changes in the contractile activity of the uterus of the rats with modeled autism spectrum disorder are caused by the disorders occurring at the postsynaptic level.

Structure and synthesis of a vaccine and diagnostic target for Enterocloster bolteae, an autism-associated gut pathogen – Part II

Enterocloster bolteae (formerly known as Clostridium bolteae) is a gastro-intestinal pathogenic bacterium often detected in the fecal microbiome of children in the autism spectrum. E. bolteae excretes metabolites that are thought to act as neurotoxins. This study is an update of our first E. bolteae investigation that discovered an immunogenic polysaccharide. Through a combination of chemical derivatizations/degradations, spectrometry and spectroscopy techniques, a polysaccharide composed of disaccharide repeating blocks comprised of 3-linked β-d-ribofuranose and 4-linked α-l-rhamnopyranose, [→3)-β-D-Ribf-(1 → 4)-α-L-Rhap-(1→]_n, was identified. To confirm the structure, and to provide material for subsequent investigations, the chemical synthesis of a corresponding linker-equipped tetrasaccharide, β-D-Ribf-(1 → 4)-α-L-Rhap-(1 → 3)-β-D-Ribf-(1 → 4)-α-L-Rhap-(1→O(CH₂)₈N₃, is also described. Research tools based on this immunogenic glycan structure can form the foundation for serotype classification, diagnostic/vaccine targets and clinical studies into the hypothesized role of E. bolteae in the onset/augmentation of autism related conditions in children.

Autism in Women

Relative to males, women with autism spectrum disorder (ASD) have neurobiological and clinical presentation differences. Recent research suggests that the male/female ASD prevalence gap is smaller than previously reported. Sex differences in symptom presentation as well as the male bias of ASD account for delayed/missed diagnosis among women. Investigating ASD and providing psychological evaluation referrals for women who are struggling socially and present with complex mental health conditions (e.g., ADHD, depression), even when they do not show typical autistic characteristics, is important. Accurate diagnosis facilitates understanding of challenges, increases access to treatments, and alleviates the burden of ASD.

Fecal microbiota transplantation improves VPA-induced ASD mice by modulating the serotonergic and glutamatergic synapse signaling pathways

Autism spectrum disorder (ASD) is a complex behavioral disorder diagnosed by social interaction difficulties, restricted verbal communication, and repetitive behaviors. Fecal microbiota transplantation (FMT) is a safe and efficient strategy to adjust gut microbiota dysbiosis and improve ASD-related behavioral symptoms, but its regulatory mechanism is unknown. The impact of the microbiota and its functions on ASD development is urgently being investigated to develop new therapeutic strategies for ASD. We reconstituted the gut microbiota of a valproic acid (VPA)-induced autism mouse model through FMT and found that ASD is in part driven by specific gut dysbiosis and metabolite changes that are involved in the signaling of serotonergic synapse and glutamatergic synapse pathways, which might be associated with behavioral changes. Further analysis of the microbiota showed a profound decrease in the genera Bacteroides and Odoribacter, both of which likely contributed to the regulation of serotonergic and glutamatergic synapse metabolism in mice. The engraftment of Turicibacter and Alistipes was also positively correlated with the improvement in behavior after FMT. Our results suggested that successful transfer of the gut microbiota from healthy donors to ASD mice was sufficient to improve ASD-related behaviors. Modulation of gut dysbiosis by FMT could be an effective approach to improve ASD-related behaviors in patients.

Evaluation of Disorders of Contractile Activity of Smooth Muscle Tissues in 9-Month-Old Rats with a Model of Autism

We studied the effect of carbachol, P₂ receptor agonists, and electric field stimulation on mechanical activity of isolated preparations of the duodenum, ileum, bladder, and vas deferens in 9-month-old rats with the valproic acid-induced model of autism. It was found that the contractions and relaxations of the isolated intestine of the experimental rats caused by various agonists and electric field stimulation did not differ from those in control animals. Carbachol induced more significant contractions of the bladder in rats with autism model than in controls and electric field stimulation induced more significant contractions of the vas deferens. We did not find significant differences in the effect of ATP, α,β-methylene-ATP and 2-methylthio-ATP on the contraction and relaxation of the studied smooth muscle organs of rats of the experimental and control groups. It was concluded that 9-month-old rats with an autism model retained increased contractile activity of the bladder and vas deferens, while intestinal contractions in experimental and control animals of this age did not differ significantly.

Diagnostic Process for Autism Spectrum Disorder: A Meta-Analysis of Worldwide Clinical Practice Guidelines for the Initial Somatic Assessment

(1) Background: Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is highly associated with various somatic conditions that can be masked by the core symptoms of ASD and thus complicate the diagnosis. Identifying co-occurring somatic disorders is critical for providing effective healthcare and social services for ASD populations and influences their long-term outcomes. A systematic assessment of co-occurring somatic conditions is essential during this ASD diagnostic process. Therefore, this study aimed to identify the organization and content of the initial somatic assessment (ISA). (2) Methods: We conducted a systematic review of the clinical practice guidelines (CPG) for the ASD diagnostic process published between January 2005 and December 2019 in English and French and performed an appraisal following the Appraisal of Guidelines Research and Evaluation, second edition (AGREE-II). (3) Results: We selected 14 CPGs that were heterogeneous in quality, with methodological scores between 32.3 and 91.9. Clinical examinations are the first step in the ISA, and the participation of pediatric, neuropediatric, and genetic specialists was highly recommended by the majority of the CPGs. The recommendations included hearing screening tests (10/14), visual examinations (8/14), and systematic genetic investigations (4/14). The CPGs also described additional investigations that should be conducted based on numerous warning signs. (4) Conclusions: Screening for consensual international warning signs is necessary to perform a comprehensive and systematic ISA during the ASD diagnostic process. A "referral form" could be used to guide clinicians and improve the coordination process. This tool may reinforce epidemiological data on co-occurring somatic disorders in patients with ASD.

Impairment in the Intestinal Morphology and in the Immunopositivity of Toll-like Receptor-4 and Other Proteins in an Autistic Mouse Model

Autism spectrum disorder (ASD) identifies a neurodevelopmental disease defined by social impairments and repetitive or stereotyped behaviors. The etiology of ASD remains unclear; it primarily affects the brain, but a link between gastrointestinal (GI) diseases, inflammatory mucosal pathology and this disorder has been suggested. In particular, a central role seems to be played by an imbalance in pro-and anti-inflammatory cytokines, oxidative stress, and apoptosis. Toll-like receptor 4 (TLR4) is a protein of innate immunity responsible for the regulation and maintenance of intestinal homeostasis. Through histochemical and immunohistochemical evaluations we analyzed the intestinal morphology and the immunopositivity of TLR4 and of other pro-inflammatory and apoptotic proteins in BTBR T+Itpr3tf/J mice. Morphological data showed that the mucosal tunica presented longer intestinal villi. The length of the villi and the epithelial surface determine the exchanges of the intestinal mucosa with luminal contents, modifying the microbiota composition. The biochemical and immunohistochemical results indicated a close relationship among the increase of TLR4 and the activation of NF-kB subunits (p65 and p50) and pro-inflammatory and apoptotic proteins, such as cyclooxygenase-2, interleukin-1β, inducible nitric oxide synthase, tumor nuclear factor—alpha, caspase-3, caspase-8. These preliminary results require more in-depth study but they suggest the TLR4 signaling pathway as a possible target for therapeutic approaches to reduce GI disorders in ASD.

The Current View on the Paradox of Pain in Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, which affects 1 in 44 children and may cause severe disabilities. Besides socio-communicational difficulties and repetitive behaviors, ASD also presents as atypical sensorimotor function and pain reactivity. While chronic pain is a frequent co-morbidity in autism, pain management in this population is often insufficient because of difficulties in pain evaluation, worsening their prognosis and perhaps driving higher mortality rates. Previous observations have tended to oversimplify the experience of pain in autism as being insensitive to painful stimuli. Various findings in the past 15 years have challenged and complicated this dogma. However, a relatively small number of studies investigates the physiological correlates of pain reactivity in ASD. We explore the possibility that atypical pain perception in people with ASD is mediated by alterations in pain perception, transmission, expression and modulation, and through interactions between these processes. These complex interactions may account for the great variability and sometimes contradictory findings from the studies. A growing body of evidence is challenging the idea of alterations in pain processing in ASD due to a single factor, and calls for an integrative view. We propose a model of the pain cycle that includes the interplay between the molecular and neurophysiological pathways of pain processing and it conscious appraisal that may interfere with pain reactivity and coping in autism. The role of social factors in pain-induced response is also discussed. Pain assessment in clinical care is mostly based on subjective rather than objective measures. This review clarifies the strong need for a consistent methodology, and describes innovative tools to cope with the heterogeneity of pain expression in ASD, enabling individualized assessment. Multiple measures, including self-reporting, informant reporting, clinician-assessed, and purely physiological metrics may provide more consistent results. An integrative view on the regulation of the pain cycle offers a more robust framework to characterize the experience of pain in autism.

Current and lifetime somatic symptom burden among transition-aged autistic young adults

Somatic symptoms are the most common cause of outpatient medical visits in the general population, yet their presence and severity in individuals on the autism spectrum has rarely been studied. We sought to assess the prevalence, impact, and clinical correlates of 14 commonly reported somatic symptoms in a sample of 290 transition-aged autistic young adults (mean [SD] age: 23.10 [2.38] years, range 18-26; 76.7% diagnosed with autism before age 18) recruited from the Simons Foundation SPARK participant pool. A modified version of the Patient Health Questionnaire-15 was used to assess somatic symptom prevalence/impact, along with measures of depression, anxiety, autistic traits, and quality of life. Somatic symptom burden was much higher in autistic young adults than previously reported in the general population. The most commonly reported current symptoms were fatigue (72.8%), sleep problems (69.0%), and menstrual problems (61.4% of females). Moderate or severe symptom levels were reported by 53.9% of females and 18.75% of males in our cohort, with the odds of females endorsing any given symptom being 2-4 times greater than males. Both individual symptoms and total symptom burden were related to higher levels of depression, anxiety, and autistic traits, along with lower quality of life. Despite little research on this topic previously, somatic symptoms are highly prevalent in autistic young adults, particularly women. Future research is needed to investigate links between somatic symptoms, medical and psychiatric morbidity, and health care utilization in the autistic population. LAY SUMMARY: Somatic symptoms (i.e., physical symptoms such as such as pain, weakness, stomachache, or shortness of breath) are highly prevalent in the general population and account for a large proportion of health care costs. However, few studies have investigated how often these symptoms are reported by autistic adults or their associations with other clinical and demographic variables. Based on self-report data from 290 young autistic adults, we found very high rates of bothersome somatic symptoms in this population, with females endorsing all symptoms at substantially higher rates than males. Somatic symptoms were also associated with worse mental health and quality of life, suggesting that they represent an overlooked contributor to poor health outcomes in the autistic adult population.

The Autism Intervention Research Network on Physical Health (AIR-P) Research Agenda

OBJECTIVES

In the United States, autistic individuals experience disproportionate physical and mental health challenges relative to non-autistic individuals, including higher rates of co-occurring and chronic conditions and lower physical, social, and psychological health-related quality of life. The Autism Intervention Research Network on Physical Health (AIR-P) is an interdisciplinary, multicenter research network for scientific collaboration and infrastructure that aims to increase the life expectancy and quality of life for autistic individuals, with a focus on underserved or vulnerable populations. The current paper describes the development of the AIR-P Research Agenda.

METHODS

Development of the research agenda involved an iterative and collaborative process between the AIR-P Advisory Board, Steering Committee, and Autistic Researcher Review Board. The methodology consisted of 3 phases: (1) ideation and design, (2) literature review and synthesis; and (3) network engagement.

RESULTS

Six core research priorities related to the health of autistic individuals were identified: (1) primary care services and quality, (2) community-based lifestyle interventions, (3) health systems and services, (4) gender, sexuality, and reproductive health, (5) neurology, and (6) genetics. Specific topics within each of these priorities were identified. Four cross-cutting research priorities were also identified: (1) neurodiversity-oriented care, (2) facilitating developmental transitions, (3) methodologically rigorous intervention studies, and (4) addressing health disparities.

CONCLUSIONS

The AIR-P Research Agenda represents an important step forward for enacting large-scale health-promotion efforts for autistic individuals across the lifespan. This agenda will catalyze autism research in historically underrepresented topic areas while adopting a neurodiversity-oriented approach to health-promotion.

Eosinophilic gastrointestinal disorders in children and adolescents: A single-center experience

BACKGROUND

To date, few studies have been conducted in Italy on pediatric eosinophilic gastrointestinal diseases (EGIDs).

AIMS

To assess clinical features of pediatric patients with EGIDs who are followed in a tertiary pediatric center.

METHODS

From January 2015 to December 2019, we retrospectively enrolled patients with EGIDs, and collected clinical, endoscopic, and histological data.

RESULTS

We enrolled 112 patients, 75.8% were male. Mean age was 9.3 ± 4.8 years. Diagnosis of EGIDs has increased in the last two years, with non-esophageal EGIDs more prevalent than eosinophilic esophagitis (EoE) (5.1% vs. 4.4%). Approximately 30% of patients had allergic comorbidities, which prevailed in children with EoE. Autism spectrum disorders were common in patients with non-esophageal EGIDs (p = 0.007), a statistically significant finding. In addition, esophageal atresia was associated with EoE (p = 0.04). Most EGIDs patients had normal findings or an inflammatory endoscopic phenotype. Patients with EoE were mainly treated with proton pump inhibitors (PPIs) alone or in combination with swallowed steroids. PPIs, oral steroids, and food-elimination diets were prescribed to patients with non-esophageal EGIDs.

CONCLUSION

This is the first Italian study revealing an increased frequency of EGIDs in a pediatric population. Further studies are needed to characterize patients with these emerging diseases.

Feeding and Swallowing Issues in Autism Spectrum Disorders

Children with autism spectrum disorder (ASD) often experience difficulties related to communication and behaviour. However, their feeding issues are most distressing to their families and healthcare professionals as they impact on the children's adaptive function and health. In comparison to typically developing children, those with ASD experience significantly more feeding difficulties. Children with ASD may display distinctive feeding difficulties and atypical feeding behaviours that include picky eating, limited independent feeding, need for increased feeding times, and a highly restrictive food repertoire. Many of these feeding difficulties continue into childhood, persist in adolescence, and even spill over into adulthood. This proves to be a formidable challenge, as feeding is an essential component for healthy nutrition, growth, and development. This article will highlight how particular food items that are eaten and preferred by affected children may be contributing to their exhibited feeding difficulties. Next, it will be shown how the children's restrictive diets supplant more healthy food options. When this is combined with the children's noted reduced physical activity, the consequences are especially serious, as they include not only malnutrition but also give rise to childhood obesity. In sum, it will be demonstrated that feeding difficulties in young children with ASD are not well understood nor managed. The dearth of knowledge about feeding issues in this population affects both assessment choices and, specifically, management practices - aspects that will be elaborated on in this article. Conclusions will include suggested future directions for enhancing and complementing knowledge of these issues for stakeholders.

Regulatory T lymphocytes/Th17 lymphocytes imbalance in autism spectrum disorders: evidence from a meta-analysis

Background

Immune system dysfunction has been proposed to play a critical role in the pathophysiology of autism spectrum disorders (ASD). Conflicting reports of lymphocyte subpopulation abnormalities have been described in numerous studies of patients with ASD. To better define lymphocytes abnormalities in ASD, we performed a meta-analysis of the lymphocyte profiles from subjects with ASD.

Methods

We used the PRISMA recommendations to query PubMed, Embase, PsychoINFO, BIOSIS, Science Direct, Cochrane CENTRAL, and Clinicaltrials.gov for terms related to clinical diagnosis of ASD and to lymphocytes’ populations. We selected studies exploring lymphocyte subpopulations in children with ASD. The search protocol has been registered in the international Prospective Register of Systematic Reviews (CRD42019121473).

Results

We selected 13 studies gathering 388 ASD patients and 326 healthy controls. A significant decrease in the CD4+ lymphocyte was found in ASD patients compared to controls [− 1.51 (95% CI − 2.99; − 0.04) p = 0.04] (I² = 96% [95% CI 94.6, 97.7], p < 0.01). No significant difference was found for the CD8+ T, B and natural killer lymphocytes. Considering the CD4+ subpopulation, there was a significant decrease in regulatory T lymphocytes (Tregs) in ASD patients (n = 114) compared to controls (n = 107) [− 3.09 (95% CI − 4.41; − 1.76) p = 0.0001]; (I² = 90.9%, [95% CI 76.2, 96.5], p < 0.0001) associated with an increase oin the Th17 lymphocytes (ASD; n = 147 controls; n = 128) [2.23 (95% CI 0.79; 3.66) p = 0,002] (I² = 95.1% [95% CI 90.4, 97.5], p < 0.0001).

Limitations

Several factors inducing heterogeneity should be considered. First, differences in the staining method may be responsible for a part in the heterogeneity of results. Second, ASD population is also by itself heterogeneous, underlying the need of studying sub-groups that are more homogeneous.

Conclusion

Our meta-analysis indicates defects in CD4+ lymphocytes, specifically decrease oin Tregs and increase in Th17 in ASD patients and supports the development of targeted immunotherapies in the field of ASD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00472-4.

Molecular signatures from multi-omics of autism spectrum disorders and schizophrenia

The genetic and phenotypic heterogeneity of autism spectrum disorder (ASD) impedes the unification of multiple biological hypotheses in an attempt to explain the complex features of ASD, such as impaired social communication, social interaction deficits, and restricted and repetitive patterns of behavior. However, recent psychiatric genetic studies have identified numerous risk genes and chromosome loci (copy number variation: CNV) which enable us to analyze at the single gene level and utilize system-level approaches. In this review, we focus on ASD as a major neurodevelopmental disorder and review recent findings mainly from the bioinformatics of omics studies. Additionally, by comparing these data with other major psychiatric disorders, including schizophrenia (SCZ), we identify unique characteristics of both diseases from multiple enrichment, pathway, and protein-protein interaction networks (PPIs) analyses using susceptible genes found in recent large-scale genetic studies. These unified, systematic approaches highlight unique characteristics of both disorders from multiple aspects and demonstrate how convergent pathways can contribute to an understanding of the complex etiology of such neurodevelopmental and neuropsychiatric disorders.

Gastrointestinal involvement of autism spectrum disorder: focus on gut microbiota

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder typical of early age, characterized by impaired communication, social interaction, and repetitive behaviors. ASD patients frequently suffer from gastrointestinal (GI) symptoms. Neuro-psychological functions, intestinal homeostasis, and functional GI disturbances are modulated by the gut microbiota through the so-called 'microbiota-gut-brain axis'.

AREAS COVERED

Literature regarding GI symptoms among the ASD community as well as the involvement and modulation of the gut microbiota in GI disturbances of ASD patients was searched. Constipation, diarrhea, reflux, abdominal bloating, pain, and discomfort are reported with variable prevalence. ASD is characterized by a reduction of Bacteroidetes/Firmicutes, of the abundance of Bacteroidetes and other imbalances. ASD patients with GI symptoms present microbial changes with plausible relation with deficiency of digestive enzymes, carbohydrate malabsorption, selective eating, bacterial toxins, serotonin metabolism, and inflammation. The strategies to mitigate the GI distress through the gut microbiota modulation comprise antimicrobials, probiotics, prebiotics, fecal microbiota transplantation, and dietary intervention.

EXPERT OPINION

The modulation of the gut microbiota in ASD individuals with GI disturbances seems a promising target for the future medicine. A standardization of the research strategies for large-scale studies together with a focus on poorly explored fields is necessary to strengthen this hypothesis.

Gastrointestinal Symptoms During Depressive Episodes in 3256 Patients with Major Depressive Disorders: Findings from the NSSD

BACKGROUND

Little is known how often depressive episodes are accompanied by gastrointestinal symptoms in major depressive disorders (MDD). The authors sought to determine the frequency and clinical correlates of gastrointestinal symptoms during episodes of depressive disorder.

METHODS

3,256 MDD patients from the National Survey on Symptomatology of Depression (NSSD), which was designed to investigate the magnitude of symptoms of current major depressive episodes in China, were enrolled and assessed for gastrointestinal symptoms in this study. Illness characteristics were compared in patients with a different frequency of gastrointestinal symptoms. Pearson correlation analysis and multiple linear regression analysis were employed to investigate the associations between gastrointestinal symptoms and psychological characteristics in the patients.

RESULTS

More than 70% of the subjects with depressive episodes had concomitant gastrointestinal symptoms. A higher frequency of gastrointestinal symptoms was associated with an increased risk of suicide ideation, suicide attempts, anxious mood, depressed mood, insomnia, feeling a failure, poor concentration, body pain, hopelessness, anger, and irritability. Pearson correlation analysis indicated moderate but significant associations between gastrointestinal symptoms and psychological characteristics (p<0.001). Multiple linear regression analysis showed that suicide ideation (β=0.161, p<0.001), anxiety mood (β=0.166, p = 0.006), insomnia (β =0.262, p<0.001), anger (β=0.144, p<0.001), feeling a failure (β =0.365, p<0.001), and body pain (β=0.581 p<0.001) were independently associated with gastrointestinal symptoms in MDD patients.

CONCLUSION

Gastrointestinal symptoms were one of the most prevalent clinical presentations of MDD. The associations between gastrointestinal symptoms and psychological characteristics may prove useful in expanding our understanding of how gastrointestinal symptoms contributes to MDD.

Eosinophilic colitis in children: a new and elusive enemy?

PURPOSE

Eosinophilic gastrointestinal disorders are rare in children and present with a broad spectrum of non-specific symptoms. To date, no guidelines for diagnosis, therapy and follow-up are validated. Aim of our study is to focus on eosinophilic colitis (EC), to determine a possible correlation between associated disorders, macroscopic findings and treatment/follow up.

METHODS

Retrospective study from 2015 to 2019 including all colonoscopies performed at our Institution. Eosinophilic colitis was defined according to the threshold identified by Collins: > 100 Eo/Hpf: right colon, > 84 Eo/Hpf transverse and left colon, > 64 Eo/Hpf sigma and rectum. We excluded colonoscopy in patients with IBD or other diseases causing hypereosinophilia (i.e., parasite infection, GVHD).

RESULTS

Among 399 colonoscopies performed in 355 patients, we made 50 diagnosis of EC, 36 males, 14 females, median age 8.5 (3-17). Symptoms leading to endoscopy were recurrent abdominal pain (66%), chronic diarrhea (64%), and chronic constipation (8%). Two patients presented with GI bleeding and one with weight loss. Macroscopic findings were mostly normal or lymphoid nodular hypertrophy presenting different endoscopic features. In seven children (14%) we found history of allergy and atopy. 22 children present a diagnosis of autistic spectrum disorder (ASD) with a prevalence higher than in the overall population (44% vs 28.5%, p = 0.03). According to symptoms, treatment consist variably of steroids, six food elimination diet, mesalamine. For patients with available follow-up, we found histological persistence of Eosinophils in 75%, even in patients with symptoms relief.

CONCLUSION

This study focus attention on EC as a new challenging pathology. Multicentric randomized clinical trials are needed to understand physiopathological mechanisms to validate a possible endoscopic score and related histological threshold, and to standardize therapy according to clinical features and instrumental findings. The high prevalence of EC in ASD need further specific research.

CNVs inform the biological network of Autism spectrum disorder

Autism spectrum disorder (ASD) is a heterogeneous condition linked to an anomalous neurodevelopment. Although the underlying causes of ASD are not well described, literature data strongly suggests a genetic component, with a complex inheritance pattern. It has recently been observed that CNVs (copy number variation) may play an important role in ASD manifestation and partially explain the complex heritability of this tract. Another factor That adds another level of complexity to ASD is its potential genetic heterogeneity. In this paper, we hypothesize that the different patterns of alteration within individuals with ASD may converge towards the same function. We genotyped a sample of 107 individuals through aCGH analysis for CNVs that were related (by localization) to approximately 1400 genes. The genes were tested for functional interactions and clustered in functional groups. We highlighted a functional genetic cluster of 256 genes potentially related to ASD. These altered genes may contribute to the same function, alterations of which increase the risk of ASD. After testing our functional cluster for biological functions, processes related to oxidative stress, immune system and energy metabolism are the pathways potentially involved with the biological alterations underlying ASD.

Case Report: Whole Exome Sequencing Revealed Disease-Causing Variants in Two Genes in a Patient With Autism Spectrum Disorder, Intellectual Disability, Hyperactivity, Sleep and Gastrointestinal Disturbances

Autism Spectrum Disorder (ASD) refers to a broad range of conditions characterized by difficulties in communication, social interaction and behavior, and may be accompanied by other medical or psychiatric conditions. Patients with ASD and comorbidities are often difficult to diagnose because of the tendency to consider the multiple symptoms as the presentation of a complicated syndromic form. This view influences variant filtering which might ignore causative variants for specific clinical features shown by the patient. Here we report on a male child diagnosed with ASD, showing cognitive and motor impairments, stereotypies, hyperactivity, sleep, and gastrointestinal disturbances. The analysis of whole exome sequencing (WES) data with bioinformatic tools for oligogenic diseases helped us to identify two major previously unreported pathogenetic variants: a maternally inherited missense variant (p.R4122H) in HUWE1, an ubiquitin protein ligase associated to X-linked intellectual disability and ASD; and a de novo stop variant (p.Q259X) in TPH2, encoding the tryptophan hydroxylase 2 enzyme involved in serotonin synthesis and associated with susceptibility to attention deficit-hyperactivity disorder (ADHD). TPH2, expressed in central and peripheral nervous tissues, modulates various physiological functions, including gut motility and sleep. To the best of our knowledge, this is the first case presenting with ASD, cognitive impairment, sleep, and gastrointestinal disturbances linked to both HUWE1 and TPH2 genes. Our findings could contribute to the existing knowledge on clinical and genetic diagnosis of patients with ASD presentation with comorbidities.

Gastrointestinal Symptoms and Feeding Problems and Their Associations with Dietary Interventions, Food Supplement Use, and Behavioral Characteristics in a Sample of Children and Adolescents with Autism Spectrum Disorders

Autism spectrum disorders (ASD) are characterized by impairments in social interaction, communication, and restricted, stereotyped behavior. Gastrointestinal (GI), nutritional, and feeding problems are often reported in ASD. We investigated the prevalence of GI symptoms, food selectivity, and mealtime difficulties, and their associations with dietary interventions, food supplement use, and behavioral characteristics in a sample involving 247 participants with ASD and 267 controls aged 2-18 years. Data were collected by a questionnaire. GI symptoms were observed in 88.9% of children and adolescents with ASD, more often in girls than in boys. High rates of food selectivity (69.1%) and mealtime problems (64.3%) were found. Food supplements were used by 66.7% of individuals, mainly vitamins/minerals, probiotics, and omega-3 fatty acids. In the ASD sample, 21.2% of subjects followed a diet, mostly based on gluten and milk restriction, including individuals exhibiting food selectivity. Frequency of GI symptoms, food selectivity, and mealtime problems correlated weakly, but significantly with behavioral characteristics in the ASD group, but not with food supplement use. The study demonstrated that higher frequency of GI symptoms, food selectivity, and mealtime problems are a common problem in pre-schoolers, schoolchildren, and adolescents with ASD, and together with dietary modification, they are significantly associated with ASD.

Maternal Immunity in Autism Spectrum Disorders: Questions of Causality, Validity, and Specificity

Autism spectrum disorders (ASD) are complex neurodevelopmental disorders with unknown heterogeneous aetiologies. Epidemiological studies have found an association between maternal infection and development of ASD in the offspring, and clinical findings reveal a state of immune dysregulation in the pre- and postnatal period of affected subjects. Maternal immune activation (MIA) has been proposed to mediate this association by altering fetal neurodevelopment and leading to autism. Although animal models have supported a causal link between MIA and development of ASD, their validity needs to be explored. Moreover, considering that only a small proportion of affected offspring develop autism, and that MIA has been implicated in related diseases such as schizophrenia, a key unsolved question is how disease specificity and phenotypic outcome are determined. Here, we have integrated preclinical and clinical evidence, including the use of animal models for establishing causality, to explore the role of maternal infections in ASD. A proposed priming/multi-hit model may offer insights into the clinical heterogeneity of ASD, its convergence with related disorders, and therapeutic strategies.