Zinc in gut-brain interaction in autism and neurological disorders

A growing amount of research indicates that abnormalities in the gastrointestinal (GI) system during development might be a common factor in multiple neurological disorders and might be responsible for some of the shared comorbidities seen among these diseases. For example, many patients with Autism Spectrum Disorder (ASD) have symptoms associated with GI disorders. Maternal zinc status may be an important factor given the multifaceted effect of zinc on gut development and morphology in the offspring. Zinc status influences and is influenced by multiple factors and an interdependence of prenatal and early life stress, immune system abnormalities, impaired GI functions, and zinc deficiency can be hypothesized. In line with this, systemic inflammatory events and prenatal stress have been reported to increase the risk for ASD. Thus, here, we will review the current literature on the role of zinc in gut formation, a possible link between gut and brain development in ASD and other neurological disorders with shared comorbidities, and tie in possible effects on the immune system. Based on these data, we present a novel model outlining how alterations in the maternal zinc status might pathologically impact the offspring leading to impairments in brain functions later in life.

[Research advances in immunological dysfunction in children with autism spectrum disorders]

Autism spectrum disorders (ASD) are a group of neuro-developmental disorders in early childhood which are defined by social difficulties, communication deficits and repetitive or restrictive interests and behaviours. The etiology of ASD remains poorly understood. Much research has shown that children with ASD suffer from immunological dysfunction. This article reviews the current research progress on immunological dysfunction in children with ASD, including abnormalities in immune cells, antibodies, complements, cytokines, major histocompatibility complex and their potential association with ASD, and explores the impacts of maternal immunological activation on the immune dysfunction of children with ASD.

Evidence supporting an altered immune response in ASD

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by deficits in social interactions, communication, and increased stereotypical repetitive behaviors. The immune system plays an important role in neurodevelopment, regulating neuronal proliferation, synapse formation and plasticity, as well as removing apoptotic neurons. Immune dysfunction in ASD has been repeatedly described by many research groups across the globe. Symptoms of immune dysfunction in ASD include neuroinflammation, presence of autoantibodies, increased T cell responses, and enhanced innate NK cell and monocyte immune responses. Moreover these responses are frequently associated with more impairment in core ASD features including impaired social interactions, repetitive behaviors and communication. In mouse models replacing immune components in animals that exhibit autistic relevant features leads to improvement in behavior in these animals. Taken together this research suggests that the immune dysfunction often seen in ASD directly affects aspects of neurodevelopment and neurological processes leading to changes in behavior. Discussion of immune abnormalities in ASD will be the focus of this review.

[Clinical concept, etiology and pathology of neuromyelitis optica]

More than a century has passed since the first description of neuromyelitis optica (NMO) or Devic's disease. The relation between NMO and multiple sclerosis (MS) had long been debated, but the discovery of anti-aquaporin-4(AQP4) antibody, an NMO-specific autoantibody has accelerated clinical and experimental research of NMO, and contributed to estabilishing NMO spectrum disorder(NMOSD), a wider disease spectrum than a prototypic opticospinal phenotype and a new disease concept: autoimmune astrocytopathic disease. Clinical, MRI and laboratory findings and therapeutic response in NMOSD are different from those in MS. On the other hand, anti-AQP4 antibody-seronegative NMOSD has some distinct features from seropositive cases, and anti-myelin oligodendrocyte glycoprotein(MOG) antibody is detected in a fraction of cases of seronegative NMOSD. Unlike anti-AQP4 antibody-associated NMOSD, anti-MOG antibody-seropositive NMOSD may be a demyelinating desease. In this review, we provide an overview of how the concept of NMOSD has evolved in association with accumulated scientific evidences.

Pathophysiology of autism spectrum disorders: Revisiting gastrointestinal involvement and immune imbalance

Autism spectrum disorders (ASD) comprise a group of neurodevelopmental abnormalities that begin in early childhood and are characterized by impairment of social communication and behavioral problems including restricted interests and repetitive behaviors. Several genes have been implicated in the pathogenesis of ASD, most of them are involved in neuronal synaptogenesis. A number of environmental factors and associated conditions such as gastrointestinal (GI) abnormalities and immune imbalance have been linked to the pathophysiology of ASD. According to the March 2012 report released by United States Centers for Disease Control and Prevention, the prevalence of ASD has sharply increased during the recent years and one out of 88 children suffers now from ASD symptoms. Although there is a strong genetic base for the disease, several associated factors could have a direct link to the pathogenesis of ASD or act as modifiers of the genes thus aggravating the initial problem. Many children suffering from ASD have GI problems such as abdominal pain, chronic diarrhea, constipation, vomiting, gastroesophageal reflux, and intestinal infections. A number of studies focusing on the intestinal mucosa, its permeability, abnormal gut development, leaky gut, and other GI problem raised many questions but studies were somehow inconclusive and an expert panel of American Academy of Pediatrics has strongly recommended further investigation in these areas. GI tract has a direct connection with the immune system and an imbalanced immune response is usually seen in ASD children. Maternal infection or autoimmune diseases have been suspected. Activation of the immune system during early development may have deleterious effect on various organs including the nervous system. In this review we revisited briefly the GI and immune system abnormalities and neuropeptide imbalance and their role in the pathophysiology of ASD and discussed some future research directions.

Exposure to Varicella Zoster Virus is higher in children with autism spectrum disorder than in healthy controls. Results from a case-control study

BACKGROUND/AIM

Autism spectrum disorder (ASD) is a group of central nervous system disorders lacking a definite etiology. The aim of the present study was to compare the exposure rate and titer of antibodies to Varicella Zoster Virus (VZV) in children with ASD and in healthy controls.

PATIENTS AND METHODS

We enrolled 54 children with ASD and 46 control individuals.

RESULTS

The exposure rate and titer of anti-VZV antibodies were significantly higher in children with ASD compared to controls (59% vs. 39% and 694 mIU/ml vs. 94 mIU/ml, respectively).

CONCLUSION

In the present case-control study, exposure to VZV was found to be independently associated with ASD.

Prevalence and titre of antibodies to cytomegalovirus and epstein-barr virus in patients with autism spectrum disorder

BACKGROUND/AIM

The etiology of autism spectrum disorders (ASD) is currently unknown. Few studies have explored the role of Cytomegalovirus (CMV) and Epstein Barr Virus (EBV) as potential etiological factors of ASD. The aim of the present study was to evaluate the seropositivity rate and antibody titre to CMV and EBV in children with ASD compared to same-aged healthy controls.

PATIENTS AND METHODS

We compared the seropositivity rate and titre of antibodies to CMV and EBV in 54 children with ASD (19 with autistic disorder and 35 with non-autistic disorder ASD) and in 46 controls.

RESULTS

Seropositivity rate and titre of the two antibodies were not dissimilar between cases and controls. However, considering only patients with ASD, those seropositive for CMV tended to test worse to the major severity scales than the seronegative ones.

CONCLUSION

Titre and seropositivity rate of antibodies to CMV and EBV are similar between children with ASD and healthy controls.

Prevalence of herpes simplex virus 1 and 2 antibodies in patients with autism spectrum disorders

BACKGROUND/AIM

The etiology of autism spectrum disorder (ASD) is unknown, even though it is hypothesized that a viral infection could trigger this disorder. The aim of this study was to evaluate the seropositivity rate and antibody level of Herpes Simplex Virus 1 (HSV1) and Herpes Simplex Virus 2 (HSV2) in children with ASD compared to same-aged healthy controls.

PATIENTS AND METHODS

We compared seropositivity rate and levels of antibodies to HSV1/2 in 54 children with ASD (19 with autistic disorder and 35 with non-autistic ASD) and in 46 controls.

RESULTS

Seropositivity rate and levels of anti-HSV1/2 were not dissimilar between cases and controls. Exposure to HSV2 was minimal.

CONCLUSION

Rate of contact with HSV1 and HSV2 assessed by the mean of detection of specific antibodies was similar between children with ASD and healthy controls.

Response to measles-mumps-rubella vaccine in children with autism spectrum disorders

BACKGROUND/AIM

The etiology of autism spectrum disorders (ASD) is unknown. The measles-mumps-rubella (MMR) vaccination has been in the past implicated in ASD pathogenesis. The aim of our study was to evaluate the rate of seropositivity and the levels of antibodies against MMR antigens in a cohort of children with ASD compared to control children.

PATIENTS AND METHODS

In a cohort of children with ASD and same-age healthy controls, we measured levels and seropositivity of antibodies against MMR.

RESULTS

A total of 60 children, 31 with ASD and 29 controls were enrolled. The seropositivity rate and levels of all the three antibodies were similar in cases and controls.

CONCLUSION

Children with ASD have a similar level and seropositivity rate of antibodies against the MMR vaccine to same-age controls. As persistent infections are typically associated with high antibody levels, our results support the arguments against a role of MMR vaccination as a causal factor or co-factor in development of ASD.

Cytokine dysregulation in autism spectrum disorders (ASD): possible role of the environment

Autism spectrum disorders (ASD) are neurodevelopmental diseases that affect an alarming number of individuals. The etiological basis of ASD is unclear, and evidence suggests it involves both genetic and environmental factors. There are many reports of cytokine imbalances in ASD. These imbalances could have a pathogenic role, or they may be markers of underlying genetic and environmental influences. Cytokines act primarily as mediators of immunological activity but they also have significant interactions with the nervous system. They participate in normal neural development and function, and inappropriate activity can have a variety of neurological implications. It is therefore possible that cytokine dysregulation contributes directly to neural dysfunction in ASD. Further, cytokine profiles change dramatically in the face of infection, disease, and toxic exposures. Imbalances in cytokines may represent an immune response to environmental contributors to ASD. The following review is presented in two main parts. First, we discuss select cytokines implicated in ASD, including IL-1Β, IL-6, IL-4, IFN-γ, and TGF-Β, and focus on their role in the nervous system. Second, we explore several neurotoxic environmental factors that may be involved in the disorders, and focus on their immunological impacts. This review represents an emerging model that recognizes the importance of both genetic and environmental factors in ASD etiology. We propose that the immune system provides critical clues regarding the nature of the gene by environment interactions that underlie ASD pathophysiology.

Behavioral correlates of maternal antibody status among children with autism

Autism spectrum disorders (ASDs) affect approximately 1 in 110 children in the United States. This report profiles fetal-brain reactive autoantibodies of a large cohort of mothers of children with autism and controls, yielding significant associations between the presence of IgG reactivity to fetal brain proteins at 37 and 73 kDa and a childhood diagnosis of full autism (p = 0.0005), which also correlated with lower expressive language scores (p = 0.005). Additionally, we report on reactivity to proteins at 39 and 73 kDa, which correlated with the broader diagnosis of ASD (p = 0.0007) and increased irritability on the Aberrant Behavioral Checklist (p = 0.05). This study provides evidence of multiple patterns of reactivity to fetal brain proteins by maternal antibodies associated with ASD and specific childhood behavioral outcomes.

The major histocompatibility complex and autism spectrum disorder

Autism spectrum disorder (ASD) is a complex disorder that appears to be caused by interactions between genetic changes and environmental insults during early development. A wide range of factors have been linked to the onset of ASD, but recently both genetic associations and environmental factors point to a central role for immune-related genes and immune responses to environmental stimuli. Specifically, many of the proteins encoded by the major histocompatibility complex (MHC) play a vital role in the formation, refinement, maintenance, and plasticity of the brain. Manipulations of levels of MHC molecules have illustrated how disrupted MHC signaling can significantly alter brain connectivity and function. Thus, an emerging hypothesis in our field is that disruptions in MHC expression in the developing brain caused by mutations and/or immune dysregulation may contribute to the altered brain connectivity and function characteristic of ASD. This review provides an overview of the structure and function of the three classes of MHC molecules in the immune system, healthy brain, and their possible involvement in ASD.

A case series of a luteolin formulation (NeuroProtek®) in children with autism spectrum disorders

There has been an impressive, little understood increase in cases of autism spectrum disorders (ASD). The lack of any distinctive pathogenetic mechanism has hampered the development of any effective treatments. Increasing evidence indicates oxidative stress, brain inflammation, gastrointestinal (GI) dysfunction and allergic symptoms may be present in ASD patients. The flavone luteolin has anti-oxidant, anti-flammatory, anti-allergy and neuroprotective properties. Given these findings, a dietary supplement was developed with a unique mixture of luteolin with the related flavonoids quercetin and rutin in a liposomal formulation of olive kernel oil (OKO), which increases their absorption. Results are presented for children with ASD (n=37, 4-14 years old) who had not obtained any benefit from multiple other regimens and who used this formulation for at least 4 months. GI and allergy symptoms improved in about 75 percent of children, eye contact and attention in 50 percent, social interaction in 25 percent and resumption of speech in about 10 percent. There were no adverse effects. Even though these results represent an uncontrolled open case series, they are encouraging because they suggest good tolerability and potential effectiveness.

Male gender bias in autism and pediatric autoimmunity

Male bias in both autism and pediatric autoimmune disease is thought to involve hormonal perturbations in pregnancy or early childhood in the context of genetic control. These early molecular events, at a time of rapid development, are intimately linked to concurrent development in the brain and immune system. It is suggested here that these early regulatory events may overlap between autism and autoimmunity in determining male sex bias and may provide evidence of an etiological link among autism, immune dysregulation, and autoimmune disease.

[Abnormalities of synaptogenesis in autism. Pathogenic and therapeutic implications]

INTRODUCTION

The social, language, and behavioural problems that occur with autism suggest that this syndrome affects a functionally diverse and widely distributed set of neural systems.

AIMS

To review the molecular pathways involved in synaptic growth, development, and stability of human synapses. We also examine the genes implicated in synaptogenesis which have been associated with autism. In particular, we highlight the role of these genes in synaptic cell adhesion, organization of presynaptic and postsynaptic specializations, growth signaling pathways, and endosomal function.

DEVELOPMENT

Proper brain function requires stringent balance of excitatory and inhibitory synapse formation during neural circuit assembly. Mutation of genes that normally sculpt and maintain this balance results in severe dysfunction, causing neurodevelopmental disorders including autism, epilepsy, Angelman syndrome, fragile X syndrome, and Rett syndrome. Such mutations may result in defective architectural structuring of synaptic connections, molecular assembly of synapses and/or functional synaptogenesis.

CONCLUSIONS

Increased knowledge of abnormal mechanisms of human synaptogenesis may lead to define different etio-pathogenic models of autism and to understand how far abnormal cell/synaptic growth and synaptic function could be reversed.

Autism spectrum disorders: from immunity to behavior

Autism spectrum disorders (ASD) are complex and heterogeneous with a spectrum of diverse symptoms. Mounting evidence from a number of disciplines suggests a link between immune function and ASD. Although the causes of ASD have yet to be identified, genetic studies have uncovered a host of candidate genes relating to immune regulation that are altered in ASD, while epidemiological studies have shown a relationship with maternal immune disturbances during pregnancy and ASD. Moreover, decades of research have identified numerous systemic and cellular immune abnormalities in individuals with ASD and their families. These include changes in immune cell number, differences in cytokine and chemokine production, and alterations of cellular function at rest and in response to immunological challenge. Many of these changes in immune responses are associated with increasing impairment in behaviors that are core features of ASD. Despite this evidence, much remains to be understood about the precise mechanism by which the immune system alters neurodevelopment and to what extent it is involved in the pathogenesis of ASD. With estimates of ASD as high as 1% of children, ASD is a major public health issue. Improvements in our understanding of the interactions between the nervous and immune system during early neurodevelopment and how this interaction is different in ASD will have important therapeutic implications with wide ranging benefits.

Plasma cytokine profiles in subjects with high-functioning autism spectrum disorders

BACKGROUND

Accumulating evidence suggests that dysregulation of the immune system is involved in the pathophysiology of autism spectrum disorders (ASD). The aim of the study was to explore immunological markers in peripheral plasma samples from non-medicated subjects with high-functioning ASD.

METHODOLOGY/PRINCIPAL FINDINGS

A multiplex assay for cytokines and chemokines was applied to plasma samples from male subjects with high-functioning ASD (n = 28) and matched controls (n = 28). Among a total of 48 analytes examined, the plasma concentrations of IL-1β, IL-1RA, IL-5, IL-8, IL-12(p70), IL-13, IL-17 and GRO-α were significantly higher in subjects with ASD compared with the corresponding values of matched controls after correction for multiple comparisons.

CONCLUSION/SIGNIFICANCE

The results suggest that abnormal immune responses as assessed by multiplex analysis of cytokines may serve as one of the biological trait markers for ASD.

[Innate and adaptive immunity in children with psychotic forms of autism-spectrum disorders]

Leukocyte elastase (LE) activity, functional activity of alpha1-proteinase inhibitor, C-reactive protein, autoantibodies to nerve growth factor and to basic myelin protein have been studied in the blood serum of children with psychotic forms of autistic disorders - children psychosis (F84.02) and atypical children psychosis (F84.11). The activation of innate immunity (the increase in LE activity and acute phase proteins) was seen in children psychosis. The more severe mental disturbances, that are characteristic of endogenous atypical children psychosis, were accompanied by the activation of both innate and adaptive immunity ( the increase of the level of autoantibodies to neuroantigenes in the peripheral blood). Correlations between immunological and clinical parameters suggest the involvement of innate and adaptive immunity in the formation of autistic and cognitive disorders in children.

Increased prevalence of familial autoimmunity in probands with pervasive developmental disorders

OBJECTIVES

Increased prevalence of familial autoimmune disease is a common finding among probands with various autoimmune disorders. Autistic disorder (autism) is a highly genetic disorder with known immune and immunogenetic abnormalities. Previous research has found an increased frequency of autoimmune disorders in families with autistic probands. We further investigated this association by determining the frequency of autoimmune disorders in families that have probands with pervasive developmental disorders (PDDs), including autism, compared with 2 control groups.

METHODS

Three well-defined study groups, including 1) families that have a child with a PDD, 2) families that have a child with an autoimmune disorder, and 3) families with a healthy control child, constituted the sample. A questionnaire inquiring about which first- and second-degree family members had received a diagnosis of having specific autoimmune disorders was completed by 101 families in each group.

RESULTS

The frequency of autoimmune disorders was significantly higher in families of the PDD probands compared with families of both the autoimmune and healthy control probands. Autoimmunity was highest among the parents of PDD probands compared with parents of the healthy control subjects. Hypothyroidism/Hashimoto's thyroiditis and rheumatic fever were significantly more common in families with PDD probands than in the healthy control families.

CONCLUSIONS

Autoimmunity was increased significantly in families with PDD compared with those of healthy and autoimmune control subjects. These preliminary findings warrant additional investigation into immune and autoimmune mechanisms in autism.

Is fever suppression involved in the etiology of autism and neurodevelopmental disorders?

BACKGROUND

There appears to be a significant increase in the prevalence rate of autism. Reasons for the increase are unknown, however, there is a substantial body of evidence that suggests the etiology involves infections of the pregnant mother or of a young child. Most infections result in fever that is routinely controlled with antipyretics such as acetaminophen. The blocking of fever inhibits processes that evolved over millions of years to protect against microbial attack. Immune mechanisms in the central nervous system are part of this protective process.

HYPOTHESIS

The blockage of fever with antipyretics interferes with normal immunological development in the brain leading to neurodevelopmental disorders such as autism in certain genetically and immunologically disposed individuals.

TESTING THE HYPOTHESIS

Epidemiological studies to determine associations between the use of antipyretics and neurodevelopmental disorders should be undertaken. Biochemical tests will involve the examination of fluids/serum by mass spectrometry and the determination of cytokine/chemokine levels in serum and cell culture fluids after stimulation with fever-inducing molecules from bacteria, viruses and yeast. Postmortem brain can be examined by immunohistochemistry or other methods such as fluorescent in situ hybridization (FISH) to determine altered expression levels of chemokines/cytokines and other molecules.

IMPLICATIONS OF THE HYPOTHESIS

1) The use of antipyretics during pregnancy or in young children may be reserved for more severe fevers. 2) The perplexing genetic findings in autism may be better understood by categorizing genes along functional pathways. 3) New treatments based on immune, cell, pharmacological or even heat therapies may be developed.

Intestinal cytokines in children with pervasive developmental disorders

OBJECTIVES

A relationship between autism and gastrointestinal (GI) immune dysregulation has been postulated based on incidence of GI complaints as well as macroscopically observed lymphonodular hyperplasia and microscopically determined enterocolitis in pediatric patients with autism. To evaluate GI immunity, we quantitatively assessed levels of proinflammatory cytokines, interleukin (IL)-6, IL-8, and IL-1beta, produced by intestinal biopsies of children with pervasive developmental disorders.

METHODS

Fifteen patients, six with pervasive developmental disorders and nine age-matched controls, presenting for diagnostic colonoscopy were enrolled. Endoscopic biopsies were organ cultured, supernatants were harvested, and IL-6, IL-8, and IL-1beta levels were quantified by ELISA. Tissue histology was evaluated by blinded pathologists.

RESULTS

Concentrations of IL-6 from intestinal organ culture supernatants of patients with pervasive developmental disorders (median 318.5 pg/ml, interquartile range 282.0-393.0 pg/ml) when compared with controls (median 436.9 pg/ml, interquartile range 312.6-602.5 pg/ml) were not significantly different (p = 0.0987). Concentrations of IL-8 (median 84,000 pg/ml, interquartile range 16,000-143,000 pg/ml) when compared with controls (median 177,000 pg/ml, interquartile range 114,000-244,000 pg/ml) were not significantly different (p = 0.0707). Concentrations of IL-1beta (median 0.0 pg/ml, interquartile range 0.0-94.7 pg/ml) when compared with controls (median 0.0 pg/ml, interquartile range 0.0-60.2 pg/ml) were not significantly different (p = 0.8826). Tissue histology was nonpathological for all patients.

CONCLUSIONS

We have demonstrated no significant difference in production of IL-6, IL-8, and IL-1beta between patients with pervasive developmental disorders and age-matched controls. In general, intestinal levels of IL-6 and IL-8 were lower in patients with pervasive developmental disorders than in age-matched controls. These data fail to support an association between autism and GI inflammation.