Blood-brain barrier and intestinal epithelial barrier alterations in autism spectrum disorders

Effects of housing conditions on behaviors and biochemical parameters in juvenile cynomolgus monkeys (Macaca fascicularis)

To investigate the effects of environmental enrichment on laboratory monkeys, we studied behavioral and physiological differences following changes in housing conditions. Ten male and female juvenile cynomolgus monkeys were first housed in pairs for 8 weeks after quarantine/acclimatization (singly housed) and subsequently housed alone for the next 8 weeks. Monkeys were subjected to evaluations of body weight gain, stereotypic or affiliative behaviors, cortisol, 4-ethylphenyl sulfate (4EPS) and catecholamine concentrations in biological samples, and blood chemistry tests under both housing conditions. Under paired housing, the stereotypic behavioral score decreased in both sexes, and the affiliative behavioral score increased in males and showed an increasing trend in females. Under single housing, the stereotypic score increased in both sexes, and the affiliative score decreased in males. Paired housing decreased serum calcium and urine cortisol concentrations in both sexes and decreased plasma cortisol in males and plasma 4EPS concentrations in females. The stereotypic score was positively correlated with serum calcium, plasma and urine cortisol, and plasma 4EPS concentration and negatively correlated with the affiliative score. The feces painting score, affiliative score, and plasma cortisol and serum calcium concentrations showed sex differences, suggesting differences in responsiveness to environmental changes between males and females. In conclusion, paired housing improved behavioral abnormalities in juvenile cynomolgus monkeys, suggesting that it may be an effective environmental enrichment paradigm. Calcium, cortisol, and 4EPS concentrations in biological samples may be useful indices for evaluating the effects of environmental enrichment.

A systematic review of gut-immune-brain mechanisms in Autism Spectrum Disorder

Despite decades of research, the etiological origins of Autism Spectrum Disorder (ASD) remain elusive. Recently, the mechanisms of ASD have encompassed emerging theories involving the gastrointestinal, immune, and nervous systems. While each of these perspectives presents its own set of supporting evidence, the field requires an integration of these modular concepts and an overarching view of how these subsystems intersect. In this systematic review, we have synthesized relevant evidences from the existing literature, evaluating them in an interdependent manner and in doing so, outlining their possible connections. Specifically, we first discussed gastrointestinal and immuno-inflammation pathways in-depth, exploring the relationships between microbial composition, bacterial metabolites, gut mucosa, and immune system constituents. Accounting for temporal differences in the mechanisms involved in neurodevelopment, prenatal and postnatal phases were further elucidated, where the former focused on maternal immune activation (MIA) and fetal development, while the latter addressed the role of immune dysregulation in contributing to atypical neurodevelopment. As autism remains, foremost, a neurodevelopmental disorder, this review presents an integration of disparate modules into a "Gut-Immune-Brain" paradigm. Existing gaps in the literature have been highlighted, and possible avenues for future research with an integrated physiological perspective underlying ASD have also been suggested.

Immune Dysfunction and Autoimmunity as Pathological Mechanisms in Autism Spectrum Disorders

Autism spectrum disorders (ASD) are a group of heterogeneous neurological disorders that are highly variable and are clinically characterized by deficits in social interactions, communication, and stereotypical behaviors. Prevalence has risen from 1 in 10,000 in 1972 to 1 in 59 children in the United States in 2014. This rise in prevalence could be due in part to better diagnoses and awareness, however, these together cannot solely account for such a significant rise. While causative connections have not been proven in the majority of cases, many current studies focus on the combined effects of genetics and environment. Strikingly, a distinct picture of immune dysfunction has emerged and been supported by many independent studies over the past decade. Many players in the immune-ASD puzzle may be mechanistically contributing to pathogenesis of these disorders, including skewed cytokine responses, differences in total numbers and frequencies of immune cells and their subsets, neuroinflammation, and adaptive and innate immune dysfunction, as well as altered levels of immunoglobulin and the presence of autoantibodies which have been found in a substantial number of individuals with ASD. This review summarizes the latest research linking ASD, autoimmunity and immune dysfunction, and discusses evidence of a potential autoimmune component of ASD.

Leaky Gut, Leaky Brain?

'Leaky gut' syndrome, long-associated with celiac disease, has attracted much attention in recent years and for decades, was widely known in complementary/alternative medicine circles. It is often described as an increase in the permeability of the intestinal mucosa, which could allow bacteria, toxic digestive metabolites, bacterial toxins, and small molecules to 'leak' into the bloodstream. Nervous system involvement with celiac disease is know to occur even at subclinical levels. Gluten and gluten sensitivity are considered to trigger this syndrome in individuals genetically predisposed to celiac disease. However, the incidence of celiac disease in the general population is quite low. Nevertheless, increased public interest in gluten sensitivity has contributed to expanded food labels stating 'gluten-free' and the proliferation of gluten-free products, which further drives gluten-free lifestyle changes by individuals without frank celiac disease. Moreover, systemic inflammation is associated with celiac disease, depression, and psychiatric comorbidities. This mini-review focuses on the possible neurophysiological basis of leaky gut; leaky brain disease; and the microbiota's contribution to inflammation, gastrointestinal, and blood-brain barrier integrity, in order to build a case for possible mechanisms that could foster further 'leaky' syndromes. We ask whether a gluten-free diet is important for anyone or only those with celiac disease.

Emerging Developments in Microbiome and Microglia Research: Implications for Neurodevelopmental Disorders

From immunology to neuroscience, interactions between the microbiome and host are increasingly appreciated as potent drivers of health and disease. Epidemiological studies previously identified compelling correlations between perinatal microbiome insults and neurobehavioral outcomes, the mechanistic details of which are just beginning to take shape thanks to germ-free and antibiotics-based animal models. This review summarizes parallel developments from clinical and preclinical research that suggest neuroactive roles for gut bacteria and their metabolites. We also examine the nascent field of microbiome-microglia crosstalk research, which includes pharmacological and genetic strategies to inform functional capabilities of microglia in response to microbial programming. Finally, we address an emerging hypothesis behind neurodevelopmental disorders, which implicates microbiome dysbiosis in the atypical programming of neuroimmune cells, namely microglia.

Fecal calprotectin levels correlate with main domains of the autism diagnostic interview-revised (ADI-R) in a sample of individuals with autism spectrum disorders from Slovakia

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by impaired social interaction and communication, as well as repetitive behavior and restricted interests. There is convincing evidence that the intestinal inflammation is involved in etiology of ASD. Increased levels of inflammatory markers were shown to be associated with more aberrant behaviors and communication of subjects with ASD. Calprotectin in the feces is produced by activated neutrophils and epithelial cells of the gut mucosa, and its levels reflect local inflammation of the gastrointestinal tract. Concentration of fecal calprotectin was determined by ELISA method in 87 individuals with ASD and 51 controls, of that 29 siblings of children with ASD and 22 non-related controls. In non-relatives significantly lower values of fecal calprotectin were observed than in both subjects with ASD and their siblings. In the group with ASD significant correlations of fecal calprotectin with all domains of the ADI-R diagnostic tool were found: qualitative abnormalities in reciprocal social interaction and communication, restrictive and repetitive patterns of behavior. Results suggest that low grade intestinal inflammation may be one of factors implicated in the pathophysiology of ASD.

Intermittent living; the use of ancient challenges as a vaccine against the deleterious effects of modern life - A hypothesis

Chronic non-communicable diseases (CNCD) are the leading cause of mortality in developed countries. They ensue from the sum of modern anthropogenic risk factors, including high calorie nutrition, malnutrition, sedentary lifestyle, social stress, environmental toxins, politics and economic factors. Many of these factors are beyond the span of control of individuals, suggesting that CNCD are inevitable. However, various studies, ours included, show that the use of intermittent challenges with hormetic effects improve subjective and objective wellbeing of individuals with CNCD, while having favourable effects on immunological, metabolic and behavioural indices. Intermittent cold, heat, fasting and hypoxia, together with phytochemicals in multiple food products, have widespread influence on many pathways related with overall health. Until recently, most of the employed challenges with hormetic effects belonged to the usual transient live experiences of our ancestors. Our hypothesis; we conclude that, whereas the total inflammatory load of multi-metabolic and psychological risk factors causes low grade inflammation and aging, the use of intermittent challenges, united in a 7-10 days lasting hormetic intervention, might serve as a vaccine against the deleterious effects of chronic low grade inflammation and it's metabolic and (premature) aging consequences.

The Perturbance of Microbiome and Gut-Brain Axis in Autism Spectrum Disorders

Gastrointestinal problems have been documented in Autism Spectrum Disorder (ASD). Studies have found that these disturbances may be associated with an altered gut microbiome in ASD. Furthermore, in ASD, these alterations are implicated in increased gut permeability, or “leaky gut”, which allows bacterial metabolites to cross the gut barrier, impacting neurodevelopment during early childhood in susceptible subjects by way of gut-brain axis. In our review, we will discuss the interaction of gut microbiota and brain development in ASD and the signaling mechanisms underlying this interaction. We will also explore the potential for treatment of ASD by targeting the microbiome with probiotics. Finally, this paper will attempt to provide significance to the aggregation of the research in this area of research; providing our interpretations and assessments of future of this field.

Dietary interventions for autism spectrum disorder: New perspectives from the gut-brain axis

There is still controversy surrounding the effectiveness of dietary interventions for autism spectrum disorder (ASD), namely the gluten-free/casein free diet and the ketogenic diet. Additionally, as studies mainly investigated their impact on ASD symptoms and behaviors, much remains unknown about their mechanisms of action and physiological effects. Given the recent surge of global interest in the gut-brain axis and its involvement in ASD, we underline the importance of understanding the physiological effects of such restrictive diets that remove certain nutritional items from one's diet. Some evidence has emerged with findings of the gut-microbial, inflammatory, and neuronal effects of these diets. We propose probiotics as a potential alternative that can serve similar biological purposes as these elimination diets and outline different physiological routes whereby probiotics can lead to improvements for individuals with ASD. We hope that future research can delineate the complete physiological effects of these diets. Such knowledge can guide the creation of more informed interventions, which conserve the components resulting in positive behavioral change while being less restrictive and devoid of the harmful effects of limiting certain nutrients.

Blood-brain barrier regulation in psychiatric disorders

The blood-brain barrier (BBB) is a dynamic interface between the peripheral blood supply and the cerebral parenchyma, controlling the transport of material to and from the brain. Tight junctions between the endothelial cells of the cerebral microvasculature limit the passage of large, negatively charged molecules via paracellular diffusion whereas transcellular transportation across the endothelial cell is controlled by a number of mechanisms including transporter proteins, endocytosis, and diffusion. Here, we review the evidence that perturbation of these processes may underlie the development of psychiatric disorders including schizophrenia, autism spectrum disorder (ASD), and affective disorders. Increased permeability of the BBB appears to be a common factor in these disorders, leading to increased infiltration of peripheral material into the brain culminating in neuroinflammation and oxidative stress. However, although there is no common mechanism underpinning BBB dysfunction even within each particular disorder, the tight junction protein claudin-5 may be a clinically relevant target given that both clinical and pre-clinical research has linked it to schizophrenia, ASD, and depression. Additionally, we discuss the clinical significance of the BBB in diagnosis (genetic markers, dynamic contrast-enhanced-magnetic resonance imaging, and blood biomarkers) and in treatment (drug delivery).

Inflammation and Neuro-Immune Dysregulations in Autism Spectrum Disorders

Autism Spectrum Disorder (ASD) is characterized by persistent deficits in social communication and interaction and restricted-repetitive patterns of behavior, interests, or activities. Strong inflammation states are associated with ASD. This inflammatory condition is often linked to immune system dysfunction. Several cell types are enrolled to trigger and sustain these processes. Neuro-inflammation and neuro-immune abnormalities have now been established in ASD as key factors in its development and maintenance. In this review, we will explore inflammatory conditions, dysfunctions in neuro-immune cross-talk, and immune system treatments in ASD management.

Microbiota-gut-brain axis: Interaction of gut microbes and their metabolites with host epithelial barriers

The gastrointestinal barrier and the blood brain barrier represent an important line of defense to protect the underlying structures against harmful external stimuli. These host barriers are composed of epithelial and endothelial cells interconnected by tight junction proteins along with several other supporting structures. Disruption in host barrier structures has therefore been implicated in various diseases of the gastrointestinal tract and the central nervous system. While there are several factors that influence host barrier, recently there is an increasing appreciation of the role of gut microbiota and their metabolites in regulating barrier integrity. In the current issue of Neurogastroenterology and Motility, Marungruang et al. describe the effect of gastrointestinal barrier maturation on gut microbiota and the blood brain barrier adding to the growing evidence of microbiota-barrier interactions. In this mini-review I will discuss the effect of gut microbiota on host epithelial barriers and its implications for diseases associated with disrupted gut-brain axis.

Infant colic or early symptom of autism spectrum disorder?

BACKGROUND

Gastrointestinal (GI) disorders are common in autism spectrum disorder (ASD). Infant colic (IC), the functional GI disorder of infancy, has not been evaluated in this patient group. The aim of this study was therefore to determine the rate of IC in ASD and investigate a possible association between ASD and IC.

METHODS

The subjects consisted of 100 ASD patients (mean age, 6.6 ± 3.5 years) and 100 healthy controls (mean age, 5.3 ± 2.8 years). The parents were questioned using the diagnostic criteria for infant colic for clinical research purposes defined in Rome IV to diagnose IC, retrospectively. The sample size was estimated using a maximum type I error probability of 5% (alpha) and a type II error of 20%.

RESULTS

The rate of IC was 16% and 17% in the ASD group and control group, respectively (P ˃ 0.05). Excessive crying with late onset and long duration in infants was defined as persistent crying. The rate of persistent crying was significantly higher in the ASD group than in the control group (32% vs 9%, P < 0.001). The relative risk of persistent crying was 4.40 in ASD. The likelihood of being misdiagnosed with IC in this group was 78%.

CONCLUSION

The rate of IC is not increased in patients with ASD, but infants with excessive crying should be very thoroughly evaluated before being diagnosed with IC. In particular, persistent crying in infants (i.e. excessive crying with late onset and long duration) may be an early symptom of ASD.

"Immune Gate" of Psychopathology-The Role of Gut Derived Immune Activation in Major Psychiatric Disorders

Interaction between the gastrointestinal tract (GI) and brain functions has recently become a topic of growing interest in psychiatric research. These multidirectional interactions take place in the so-called gut-brain axis or more precisely, the microbiota-gut-brain axis. The GI tract is the largest immune organ in the human body and is also the largest surface of contact with the external environment. Its functions and permeability are highly influenced by psychological stress, which are often a precipitating factor in the first episode, reoccurrence and/or deterioration of symptoms of psychiatric disorders. In recent literature there is growing evidence that increased intestinal permeability with subsequent immune activation has a major role in the pathophysiology of various psychiatric disorders. Numerous parameters measured in this context seem to be aftermaths of those mechanisms, yet at the same time they may be contributing factors for immune mediated psychopathology. For example, immune activation related to gut-derived bacterial lipopolysaccharides (LPS) or various food antigens and exorphins were reported in major depression, schizophrenia, bipolar disorder, alcoholism and autism. In this review the authors will summarize the evidence and roles of such parameters and their assessment in major psychiatric disorders.

Identification of Correlative Shifts in Indices of Brain Cholesterol Metabolism in the C57BL6/Mecp2tm1.1Bird Mouse, a Model for Rett Syndrome

Rett syndrome (RS) is a pervasive neurodevelopmental disorder resulting from loss-of-function mutations in the X-linked gene methyl-Cpg-binding protein 2 (MECP2). Using a well-defined model for RS, the C57BL6/Mecp2^tm1.1Bird mouse, we have previously found a moderate but persistently lower rate of cholesterol synthesis, measured in vivo, in the brains of Mecp2^-/y mice, starting from about the third week after birth. There was no genotypic difference in the total cholesterol concentration throughout the brain at any age. This raised the question of whether the lower rate of cholesterol synthesis in the mutants was balanced by a fall in the rate at which cholesterol was converted via cholesterol 24-hydroxylase (Cyp46A1) to 24S-hydroxycholesterol (24S-OHC), the principal route through which cholesterol is ordinarily removed from the brain. Here, we show that while there were no genotypic differences in the concentrations in plasma and liver of three cholesterol precursors (lanosterol, lathosterol, and desmosterol), two plant sterols (sitosterol and campesterol), and two oxysterols (27-hydroxycholesterol [27-OHC] and 24S-OHC), the brains of the Mecp2 ^-/y mice had significantly lower concentrations of all three cholesterol precursors, campesterol, and both oxysterols, with the level of 24S-OHC being ~20% less than in their Mecp2 ^+/y controls. Together, these data suggest that coordinated regulation of cholesterol synthesis and catabolism in the central nervous system is maintained in this model for RS. Furthermore, we speculate that the adaptive changes in these two pathways conceivably resulted from a shift in the permeability of the blood-brain barrier as implied by the significantly lower campesterol and 27-OHC concentrations in the brains of the Mecp2^-/y mice.

Gut-immune-brain dysfunction in Autism: Importance of sex

Autism Spectrum Disorder (ASD) is characterized by social behavior deficits, stereotypies, cognitive rigidity, and in some cases severe intellectual impairment and developmental delay. Although ASD is most widely identified by its neurological deficits, gastrointestinal issues are common in ASD. An intimate and complex relationship exists between the gut, the immune system, and the brain, leading to the hypothesis that ASD may be a systems-level disease affecting the gut and immune systems, in addition to the brain. Despite significant advances in understanding the contribution of the gut and immune systems to the etiology of ASD, there is an intriguing commonality among patients that is not well understood: they are predominantly male. Virtually no attention has been given to the potential role of sex-specific regulation of gut, peripheral, and central immune function in ASD, despite the 4:1 male-to-female bias in this disorder. In this review, we discuss recent revelations regarding the impact of gut-immune-brain relationships on social behavior in rodent models and in ASD patients, placing them in the context of known or putative sex specific mechanisms.

Intestinal Microbiota Influences Non-intestinal Related Autoimmune Diseases

The human body is colonized by millions of microorganisms named microbiota that interact with our tissues in a cooperative and non-pathogenic manner. These microorganisms are present in the skin, gut, nasal, oral cavities, and genital tract. In fact, it has been described that the microbiota contributes to balancing the immune system to maintain host homeostasis. The gut is a vital organ where microbiota can influence and determine the function of cells of the immune system and contributes to preserve the wellbeing of the individual. Several articles have emphasized the connection between intestinal autoimmune diseases, such as Crohn's disease with dysbiosis or an imbalance in the microbiota composition in the gut. However, little is known about the role of the microbiota in autoimmune pathologies affecting other tissues than the intestine. This article focuses on what is known about the role that gut microbiota can play in the pathogenesis of non-intestinal autoimmune diseases, such as Grave's diseases, multiple sclerosis, type-1 diabetes, systemic lupus erythematosus, psoriasis, schizophrenia, and autism spectrum disorders. Furthermore, we discuss as to how metabolites derived from bacteria could be used as potential therapies for non-intestinal autoimmune diseases.

Interplay Between Peripheral and Central Inflammation in Autism Spectrum Disorders: Possible Nutritional and Therapeutic Strategies

Pre- and post-natal factors can affect brain development and function, impacting health outcomes with particular relevance to neurodevelopmental diseases, such as autism spectrum disorders (ASDs). Maternal obesity and its associated complications have been related to the increased risk of ASDs in offspring. Indeed, animals exposed to maternal obesity or high fat diets are prone to social communication impairment and repetitive behavior, the hallmarks of autism. During development, fatty acids and sugars, as well as satiety hormones, like insulin and leptin, and inflammatory factors related to obesity-induced low grade inflammation, could play a role in the impairment of neuroendocrine system and brain neuronal circuits regulating behavior in offspring. On the other side, post-natal factors, such as mode of delivery, stress, diet, or antibiotic treatment are associated to a modification of gut microbiota composition, perturbing microbiota-gut-brain axis. Indeed, the interplay between the gastrointestinal tract and the central nervous system not only occurs through neural, hormonal, and immune pathways, but also through microbe-derived metabolic products. The modification of unhealthy perinatal and postnatal environment, manipulation of gut microbiota, nutritional, and dietary interventions could represent possible strategies in preventing or limiting ASDs, through targeting inflammatory process and gut microbiota.

Can EGCG Alleviate Symptoms of Down Syndrome by Altering Proteolytic Activity?

Down syndrome (DS), also known as "trisomy 21", is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. Silencing these extra genes is beyond existing technology and seems to be impractical. A number of pharmacologic options have been proposed to change the quality of life and lifespan of individuals with DS. It was reported that treatment with epigallocatechin gallate (EGCG) improves cognitive performance in animal models and in humans, suggesting that EGCG may alleviate symptoms of DS. Traditionally, EGCG has been associated with the ability to reduce dual specificity tyrosine phosphorylation regulated kinase 1A activity, which is overexpressed in trisomy 21. Based on the data available in the literature, we propose an additional way in which EGCG might affect trisomy 21-namely by modifying the proteolytic activity of the enzymes involved. It is known that, in Down syndrome, the nerve growth factor (NGF) metabolic pathway is altered: first by downregulating tissue plasminogen activator (tPA) that activates plasminogen to plasmin, an enzyme converting proNGF to mature NGF; secondly, overexpression of metalloproteinase 9 (MMP-9) further degrades NGF, lowering the amount of mature NGF. EGCG inhibits MMP-9, thus protecting NGF. Urokinase (uPA) and tPA are activators of plasminogen, and uPA is inhibited by EGCG, but regardless of their structural similarity tPA is not inhibited. In this review, we describe mechanisms of proteolytic enzymes (MMP-9 and plasminogen activation system), their role in Down syndrome, their inhibition by EGCG, possible degradation of this polyphenol and the ability of EGCG and its degradation products to cross the blood-brain barrier. We conclude that known data accumulated so far provide promising evidence of MMP-9 inhibition by EGCG in the brain, which could slow down the abnormal degradation of NGF.

Impact of Auditory Integrative Training on Transforming Growth Factor-β1 and Its Effect on Behavioral and Social Emotions in Children with Autism Spectrum Disorder

OBJECTIVE

To explore the impact of auditory integrative training (AIT) on the inflammatory biomarker transforming growth factor (TGF)-β1 and to assess its effect on social behavior in children with autism spectrum disorder (ASD).

SUBJECTS AND METHODS

In this cross-sectional study, 15 patients (14 males and 1 female) with ASD aged 3-12 years were recruited. All were screened for autism using the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Plasma levels of TGF-β1 were measured in all patients using a sandwich enzyme-linked immunoassay (ELISA) immediately and 1 and 3 months after the AIT sessions. Pre- and post-AIT behavioral scores were also calculated for each child using the Childhood Autism Rating Scale (CARS), the Social Responsiveness Scale (SRS), and the Short Sensory Profile (SSP). Data were analyzed using the Statistical Package for the Social Sciences (SPSS 21.0 for Windows).

RESULTS

Plasma levels of TGF-β1 significantly increased to 85% immediately after AIT (20.13 ± 12 ng/mL, p < 0.05), to 95% 1 month after AIT (21.2 ± 11 ng/mL, p < 0.01), and to 105% 3 months after AIT (22.25 ± 16 ng/mL, p < 0.01) compared to before AIT (10.85 ± 8 ng/mL). Results also revealed that behavioral rating scales (CARS, SRS, and SSP) improved in terms of disease severity after AIT.

CONCLUSION

Increased plasma levels of TGF-β1 support the therapeutic effect of AIT on TGF-β1 followed by improvement in social awareness, social cognition, and social communication in children with ASD. Furthermore, TGF-β1 was associated with severity in all scores tested (CARS, SRS, and SSP); if confirmed in studies with larger sample sizes, TGF-β1 may be considered as a marker of ASD severity and to assess the efficacy of therapeutic interventions.

Microbiota-related Changes in Bile Acid & Tryptophan Metabolism are Associated with Gastrointestinal Dysfunction in a Mouse Model of Autism

Autism spectrum disorder (ASD) is one of the most prevalent neurodevelopmental conditions worldwide. There is growing awareness that ASD is highly comorbid with gastrointestinal distress and altered intestinal microbiome, and that host-microbiome interactions may contribute to the disease symptoms. However, the paucity of knowledge on gut-brain axis signaling in autism constitutes an obstacle to the development of precision microbiota-based therapeutics in ASD. To this end, we explored the interactions between intestinal microbiota, gut physiology and social behavior in a BTBR T+Itpr3tf/J mouse model of ASD. Here we show that a reduction in the relative abundance of very particular bacterial taxa in the BTBR gut - namely, bile-metabolizing Bifidobacterium and Blautia species, - is associated with deficient bile acid and tryptophan metabolism in the intestine, marked gastrointestinal dysfunction, as well as impaired social interactions in BTBR mice. Together these data support the concept of targeted manipulation of the gut microbiota for reversing gastrointestinal and behavioral symptomatology in ASD, and offer specific plausible targets in this endeavor.

Food and the gut: relevance to some of the autisms

Complex, diverse and rarely appearing without comorbidity, the autism spectrum disorders continue to be a source of research interest. With core symptoms variably impacting on social communication skills, the traditional focus of many research efforts has centred on the brain and how genetic and environmental processes impact on brain structure, function and/or connectivity to account for various behavioural presentations. Alongside emerging ideas on autistic traits being present in various clinical states, the autisms, and the overrepresentation of several comorbid conditions impacting on quality of life, other research avenues have opened up. The central role of the brain in relation to autism may be at least partially influenced by the functions of other organs. The gastrointestinal (GI) tract represents an important biological system pertinent to at least some autism. The notion of a gut-brain-behaviour axis has garnered support from various findings: an overrepresentation of functional and pathological bowel states, bowel and behavioural findings showing bidirectional associations, a possible relationship between diet, GI function and autism and recently, greater focus on aspects of the GI tract such as the collected gut microbiota in relation to autism. Gaps remain in our knowledge of the functions of the GI tract linked to autism, specifically regarding mechanisms of action onward to behavioural presentation. Set however within the context of diversity in the presentation of autism, science appears to be moving towards defining important GI-related autism phenotypes with the possibility of promising dietary and other related intervention options onward to improving quality of life.

Organ-specific protection mediated by cooperation between vascular and epithelial barriers

Immune privilege is a complex process that protects organs from immune-mediated attack and damage. It is accomplished by a series of cellular barriers that both control immune cell entry and promote the development of tolerogenic immune cells. In this Review, we describe the vascular endothelial and epithelial barriers in organs that are commonly considered to be immune privileged, such as the brain and the eye. We compare these classical barriers with barriers in the intestine, which share features with barriers of immune-privileged organs, such as the capacity to induce tolerance and to protect from external insults. We suggest that when intestinal barriers break down, disruption of other barriers at distant sites can ensue, and this may underlie the development of various neurological, metabolic and intestinal disorders.

Increased Serum Zonulin Levels as an Intestinal Permeability Marker in Autistic Subjects

OBJECTIVE

To evaluate the serum levels of zonulin, which regulates tight junctions between enterocytes and is a physiological modulator controlling intestinal permeability, in patients with autism spectrum disorders (ASDs).

STUDY DESIGN

Serum zonulin levels were determined in 32 patients with ASD and 33 healthy controls using an enzyme-linked immunosorbent assay. The severity of ASD symptoms was assessed with the Childhood Autism Rating Scale.

RESULTS

Serum zonulin levels were significantly higher in the patients with ASD (122.3 ± 98.46 ng/mL) compared with the healthy controls (41.89 ± 45.83 ng/mL). There was a positive correlation between zonulin levels and Childhood Autism Rating Scale score when all subjects were assessed (r = 0.523; P < .001).

CONCLUSIONS

This study suggests that zonulin, which regulates intestinal permeability, plays a role in the development of symptoms of ASD.

Bio-collections in autism research

Autism spectrum disorder (ASD) is a group of complex neurodevelopmental disorders with diverse clinical manifestations and symptoms. In the last 10 years, there have been significant advances in understanding the genetic basis for ASD, critically supported through the establishment of ASD bio-collections and application in research. Here, we summarise a selection of major ASD bio-collections and their associated findings. Collectively, these include mapping ASD candidate genes, assessing the nature and frequency of gene mutations and their association with ASD clinical subgroups, insights into related molecular pathways such as the synapses, chromatin remodelling, transcription and ASD-related brain regions. We also briefly review emerging studies on the use of induced pluripotent stem cells (iPSCs) to potentially model ASD in culture. These provide deeper insight into ASD progression during development and could generate human cell models for drug screening. Finally, we provide perspectives concerning the utilities of ASD bio-collections and limitations, and highlight considerations in setting up a new bio-collection for ASD research.

Neuroinflammation and Infection: Molecular Mechanisms Associated with Dysfunction of Neurovascular Unit

Neuroinflammation is a complex inflammatory process in the central nervous system, which is sought to play an important defensive role against various pathogens, toxins or factors that induce neurodegeneration. The onset of neurodegenerative diseases and various microbial infections are counted as stimuli that can challenge the host immune system and trigger the development of neuroinflammation. The homeostatic nature of neuroinflammation is essential to maintain the neuroplasticity. Neuroinflammation is regulated by the activity of neuronal, glial, and endothelial cells within the neurovascular unit, which serves as a “platform” for the coordinated action of pro- and anti-inflammatory mechanisms. Production of inflammatory mediators (cytokines, chemokines, reactive oxygen species) by brain resident cells or cells migrating from the peripheral blood, results in the impairment of blood-brain barrier integrity, thereby further affecting the course of local inflammation. In this review, we analyzed the most recent data on the central nervous system inflammation and focused on major mechanisms of neurovascular unit dysfunction caused by neuroinflammation and infections.

The Gut Microbiota and Autism Spectrum Disorders

Gastrointestinal (GI) symptoms are a common comorbidity in patients with autism spectrum disorder (ASD), but the underlying mechanisms are unknown. Many studies have shown alterations in the composition of the fecal flora and metabolic products of the gut microbiome in patients with ASD. The gut microbiota influences brain development and behaviors through the neuroendocrine, neuroimmune and autonomic nervous systems. In addition, an abnormal gut microbiota is associated with several diseases, such as inflammatory bowel disease (IBD), ASD and mood disorders. Here, we review the bidirectional interactions between the central nervous system and the gastrointestinal tract (brain-gut axis) and the role of the gut microbiota in the central nervous system (CNS) and ASD. Microbiome-mediated therapies might be a safe and effective treatment for ASD.