Microbiome and ASD

According to this 2020 paper, research studies are looking into the composition of gut microbiota as a possible factor in the pathogenesis of autism spectrum disorders (ASD) since functional gastrointestinal disorders are fairly prevalent issues and are linked with ASD. The aim of this narrative review was to examine the microbial profile of individuals with and without ASD and find associations between microbial profiles with functional gastrointestinal disorder comorbidity, and ASD pathogenesis. The results demonstrated that prevalence and risk of functional gastrointestinal disorders are related to severity of ASD (incidence was significantly higher in children with autism). Also, there were differences in bacterial and fungal diversity between the guts of ASD and non-autistic children. It should be noted that there are limitations with these studies analyzing gut microbiota - for example a varied range of methodologies were employed. Furthermore, covariate analysis revealed that the results were influenced by numerous factors such as demographics, diet, disease severity, GI comorbidity and allergies. [NPID: gut microbiota, gut microbiome, gastrointestinal, gut disorders, functional gastrointestinal disorders, gut-brain axis, ASD, autism, autism spectrum disorder]

As autism spectrum disorder (ASD) is suspected to be connected to the gut microbiota, this 2019 article presents the specific differences in the gut microbiota observed in many autistic patients. This paper also explains that the mechanisms by which these differences occur may lead to the production of bacterial metabolites and possibly a leaky gut. It is fairly common for autistic individuals to have a compromised gut-blood-barrier. In autistic children, abnormal levels of metabolites have been spotted. Many of these metabolites were of bacterial origin such as short chain fatty acids (SCFAs), indoles and lipopolysaccharides (LPS). The leakage of these bacterial metabolites in autistic patients result in modifications of their metabolisms and changes in body responses. Furthermore, autism is associated with an imbalance in gut microbiota (dysbiosis). Although the causal link between gut microbiota and ASD has yet to be confirmed, consuming probiotics does not appear to have adverse effects and can potentially promote gut health and help achieve gut homeostasis. Finally, the authors discuss the novel biomarkers currently showing promise, and the potential therapeutic strategies that could be implemented in this area of research. [NPID: gut microbiota, gut microbiome, autism, autism spectrum disorder, ASD, leaky gut, autistic, dysbiosis, probiotics]

This is a narrative review written in 2019 that aimed to evaluate the available research on dysbiosis (imbalance in gut microbial community) and gastrointestinal (GI) disorders in autism spectrum disorder (ASD), while also examining the evidence for the role of probiotics and other non-pharmacological approaches in the treatment of children with ASD. After analyzing the research papers, Fattorusso et al. found that gut dysbiosis was well documented in autistic children. However, there was no unique profile of gut microbiota composition specific to people with ASD. An imbalance in gut microbial community can contribute to the low-grade systemic inflammatory state reported in patients with GI comorbidities. The most promising treatment for the neurobehavioral symptoms and bowel dysfunction is probiotics but the current clinical trials are not consistent and are few in number. Well-designed, randomized, placebo-controlled clinical trials are required to validate the effectiveness of probiotics in the treatment of ASD and to identify the appropriate strains, doses, and timing of treatment. [NPID: probiotics, gut microbiota, gut microbes, gut bacteria, gut health, ASD, autism, autism spectrum disorder, autistic, children, gastrointestinal, GI, inflammation]

This 2018 review focuses on neurodevelopmental disorders such as autism spectrum disorder (ASD) since children with these types of disorders often complain of gastrointestinal problems and dysbiosis (imbalance) of gut microbiota. Firstly, the author describes the microbiome, which is a collection of microbes and their genetic material that can reside on the exposed and internal surfaces of our bodies. Hosts may receive physiological benefit from these microbes, while other bacteria can cause some diseases. Preclinical studies have indicated that the gut microbiome plays an important role in the bidirectional communication between the gut and central nervous system (gut-brain axis). In addition, the gut microbiome has been reported to be involved in the pathogenesis of autism spectrum disorder (ASD). While there seems to be a link between the microbiome, gut and brain, this review discusses the potential mechanisms by which gut microbiome influences the etiology of ASD via altering the gut-brain axis. Probiotic treatment and fecal microbiota transplant are new and potential treatment choices for ASD that target the gut microbiome. [NPID: gut microbiota, gut microbiome, gut bacteria, gut health, probiotics, GI, gastrointestinal, ASD, autism, autism spectrum disorder, transplant, fecal microbiota transplant]

Although the cause of autism spectrum disorder (ASD) has not yet been confirmed, this 2018 article highlights that a disturbance of the gut-brain axis (communication that exists between the gut, microbiota, and brain) may be an important factor that contributes to autism. In this study, the fecal microbiota of 30 children with ASD were compared with that of 24 healthy children using next-generation gene sequencing. All participants were recruited from India. The autistic kids were also assessed on several markers associated with ASD such as the INCLEN Diagnostic Tool for Autism Spectrum Disorder (INDT-ASD) and the Indian Scale for Assessment of Autism (ISAA) tool. There was a notable imbalance in microbiota communities in the gut of autistic children, with higher abundances of families Lactobacillaceae, Bifidobacteraceae, and Veillonellaceae, compared to typically developing children. The dominant family in the gut microbiome of healthy children was Prevotellaceae. A comparative meta-analysis with another American dataset consisting of 20 ASD and 20 healthy control subjects (children) of similar age revealed a significantly high abundance of genus Lactobacillus in ASD children among both populations. In conclusion, microbial dysbiosis (imbalance in the microbial community) was evident in the gut microbiome of ASD children, which was associated with a high abundance of the Lactobacillus species. [NPID: gut microbiota, gut microbiome, gut bacteria, GI, gastrointestinal, autism, ASD, autism spectrum disorder, India, Indian, dysbiosis, autistic, children]

The aim of this 2019 systematic review was to characterize the gut microbiome profile of children with neurodevelopmental disorders, and to find potentially traits that are different to healthy children. The review included studies that recruited young individuals (aged between 0-18 years) with a neurodevelopmental disorder. Of the 10 case-control studies selected to be analyzed in this review, two studies examined the gut microbiome of children with attention deficit hyperactivity disorder (ADHD), while 8 reported data on either the gut or the oral microbiome of children with autism spectrum disorder (ASD). Across all studies, there was great variation in sample size, gender, clinical issues, and type of controls. This high level of heterogeneity, in addition to the small sample sizes of the studies, reduced the validity of these results. Moreover, the 10 studies were deemed to be low to moderate methodological quality. Overall, more high-quality observational studies are warranted to elucidate the potential role of the microbiome in patients with neurodevelopmental disorders. [NPID: gut microbiome, gut microbiota, gut bacteria, GI, gastrointestinal, neurodevelopmental disorders, ASD, ADHD, autism, autism spectrum disorder, attention deficit hyperactivity disorder, review, children]

The objective of this 2019 pilot study was to characterize the oral and gut microbiome of patients with autism spectrum disorders (ASD), and to compare these features with those of typically developed individuals. In addition, Kong et al. looked at the use of microbiome markers for ASD diagnosis and subtyping of clinical comorbid conditions. Another aim was to develop microbiome biomarkers that would help subsequent clinical trials report their findings on probiotic supplementation. The authors found that previous studies had paid little attention to the oral bacteria of patients. The results indicated distinct features in the gut and salivary microbiota, with variations found between typically developed people and autistic patients. Moreover, this present study attempted to find out microbiome characteristics associated with clinical subtypes such as allergies, abdominal pain, and abnormal dietary habits. The researchers determined that the diagnosis of ASD is potentially highly subjective, with a high level of reliance on psychological testing. Hopefully, the preliminary evidence for developing microbial markers presented in this study can be used to diagnose or guide therapy of ASD and comorbid conditions. Furthermore, these preliminary results can help future research with experiments such as testing whether modifying the gut and oral microbiome can improve co-morbid conditions in patients with ASD, and positively affect ASD symptomatology. [NPID: ASD, autism, autism spectrum disorder, autistic, gut microbiome, oral health, mouth bacteria, mouth microbiome, gut microbiota, gut health, gastrointestinal, GI]

See original abstract (too short to summarize).

In this 2020 study, the microbiota present in the gut of individuals with and without attention deficit hyperactivity disorder (ADHD) was extracted and placed in young, male mice. The animals’ behaviors were then analyzed (via a behavioral test), as well as its brain structure and function through magnetic resonance imaging (MRI). The researchers who conducted this experiment hypothesized that mice given the microbiota of persons with ADHD would be different in brain function and/or structure to mice that receive microbiota of persons without ADHD. The fecal microbiota of mice colonized with ADHD microbiota were distinguishable to that of mice transplanted with control microbiota. Examining the brain there was a reduction in structural integrity of both white and grey matter regions in mice that received ADHD microbiota. White matter integrity was strongly linked with distinct microbiota expression. Furthermore, the MRI indicated decreased connectivity between the right motor and right visual cortices in the mice colonized with ADHD microbiota. These regions are said to be altered in several neurodevelopmental disorders. The open-field test also revealed heightened anxiety in the mice given ADHD microbiota. To summarize these results, a change in microbial composition of the gut may stimulate further alterations in brain structure and function, as well as modifications in animal behavior. [NPID: gut microbiota, gut microbiome, gut bacteria, ADHD, attention deficit hyperactivity disorder, gut health, animal study, neurodevelopmental disorders]

Since the intestinal microbiota is thought to play a crucial role in the functioning and regulation of the central nervous system, neuroimmune system and neuroendocrine system, this 2020 article discusses how the microbiota and diet may relate to the development of autism spectrum disorder (ASD). Moreover, the author covers the recent findings on the influences that dietary supplements and probiotics have on the symptoms of autism. A robust survey suggested that the diet and lifestyle of mothers are strongly associated with the development of ASD and other neurodevelopmental disorders. Research has also shown that the gut microbiota composition is different in autistic patients compared to typically developing children. One limitation of these studies is the high diversity in participants. Due to this great variability, the distinct profile of microbiome in ASD has not been fully determined. Using probiotics as supplements has helped reduce ASD symptomatology but the results are inconclusive. Therefore, this article highlights the need for more detailed research on the role of the microbiome, diet, and probiotics in the development and management of autism spectrum disorder. [NPID: autism, autism spectrum disorder, ASD, gut microbiota, intestinal, gut microbiome, gut bacteria, diet, autistic, children, neurodevelopmental disorders, supplements, probiotics, supplementation]

This 2019 paper explains that the bacteria community (microbiota) in the gut may have a role in the physiological processes associated with autism spectrum disorder (ASD), since gastrointestinal dysfunction is a comorbidity that often accompanies ASD. Manipulation of the gut microbiota has been reported to reduce the symptoms of ASD, but studies have yet to confirm the patterns in altered bacterial species specific to this disorder. This meta-analysis examined the bacterial genera abundances seen in the gut of healthy control subjects and of patients with ASD. Nine studies were included in this meta-analysis, with data on 254 individuals with ASD. Autistic children were found to possess lower percentages of Akkermansia, Bacteroides, Bifidobacterium, and Parabacteroides and a higher percentage of Faecalibacterium in their guts, when compared with healthy controls. In addition, kids living with autism showed lower abundances of Enterococcus, Escherichia coli, Bacteroides, and Bifidobacterium and higher abundance of Lactobacillus (relative to control). This meta-analysis suggests an association between ASD and an alteration in gut microbiota composition. Future studies are recommended to assess the relationship between bacterial changes and symptoms of ASD, as this research would enhance the evidence for the accurate and appropriate treatment of autism. [NPID: autism, autism spectrum disorder, ASD, gut microbiota, gut microbiome, gut bacteria, meta-analysis, probiotics, children]

Although there has been an increase in support for the possible connection between the gut microbiota (and its metabolites) with gastrointestinal disorders and the development of autism spectrum disorder (ASD), this 2019 study emphasizes that there is limited data on the link between gut microbiota with gastrointestinal symptoms and the presence of short-chain fatty acids (a metabolite of the gut microbiota) in the feces of children with autism. The researchers associated with this trial sequenced the bacterial 16S rRNA gene, detected fecal short chain fatty acids (SCFAs), assessed GI symptoms, and analyzed the relationship between the gut microbiome and fecal SCFAs in autistic and neurotypical individuals. The results demonstrated that the compositions of the gut microbiota and the short-chain fatty acids (SCFAs) were different in the autistic participants, relative to the control group (neurotypical). The subjects with autism also had lower levels of acetic acid and butyrate, and a higher level of valeric acid in their fecal samples. Furthermore, abundances of key butyrate-producing taxa (Ruminococcaceae, Eubacterium, Lachnospiraceae and Erysipelotrichaceae) were lower in those with autism, while their abundance of valeric acid associated bacteria (Acidobacteria) were higher than the control subjects. The one gastrointestinal disorder identified in the children with ASD was constipation. When examining the stools of these constipated autistic individuals, the scientists noticed increased abundance of Fusobacterium, Barnesiella, Coprobacter and valeric acid-associated bacteria (Actinomycetaceae) as well as reduced butyrate-producing taxa. To conclude, this study suggests that the gut microbiota contributes to fecal SCFAs and constipation in autism. Microbiota-modifying strategies may have potential as an alternative treatment of autism, particularly those targeting the butyrate-producing bacteria in the gut. [NPID: gut microbiota, gut microbes, gut bacteria, GI, gastrointestinal, autism, autism spectrum disorder, ASD, fatty acids, bacteria, autistic, children]

According to this 2020 article, dysbiosis (imbalance in microorganisms in the gut) and gastrointestinal comorbidities are often associated with autism spectrum disorder (ASD). Therefore, the aim of this present review was to investigate the differences in composition of gut microbiota in children with and without ASD. Firstly, electronic databases were searched to find relevant studies for this meta-analysis. A total of 18 studies were included, equating to a dataset of 493 children with ASD and 404 non-autistic individuals. The main microbiota found in the gut of ASD children were of the phyla Bacteroidetes, Firmicutes, and Actinobacteria. These were more abundant in the autistic children than the healthy control subjects. In addition, the kids with autism showed a significantly higher abundance of the genera Bacteroides, Parabacteroides, Clostridium, Faecalibacterium, and Phascolarctobacterium and a lower percentage of Coprococcus and Bifidobacterium (compared with non-autistic participants). In conclusion, this meta-analysis provides evidence that there is an imbalance in the gut microbiota community of autstic children, which may affect their development and the severity of their ASD symptomatology. Additional research is encouraged to enhance our current knowledge on the effectiveness of pre- or probiotics in reducing autistic behaviors. [NPID: autism, autism spectrum disorder, ASD, autistic, children, meta-analysis, dysbiosis, gut microbiota, gut microbes, gut bacteria, GI, gastrointestinal]

In this 2019 paper, the authors reviewed the available literature on the use of nutritional therapy in autism spectrum disorder (ASD). The aim was to look at the current evidence on nutritional treatment, and its effects on symptoms of autism. Electronic databases such as PubMed were searched for studies regarding nutrition and autism. The review discovered that although gluten-free/casein-free and ketogenic diets, camel milk, curcumin, probiotics, and fermentable foods may contribute to a reduction in ASD symptoms, the intake of sugars, additives, pesticides, genetically modified organisms, inorganic processed foods, and hard to digest starches may worsen the symptoms. It is worth studying the current nutritional approaches specific to people with autism, although more prospective controlled trials with large sample populations are warranted. Nevertheless, this review provides future trials with suggestions on study designs that may help identify and develop novel treatments for autism. [NPID: autism, autism spectrum disorder, ASD, diet, symptoms, review, nutrition, sugars, processed food, camel milk, gluten-free, casein-free, gluten]

The purpose of this 2020 study was to analyze the microbiota living in the gut of children with attention deficit hyperactivity disorder (ADHD), and to determine the role of the gut microbiota in the development of this disorder. Wan et al. recruited 17 young children (aged 6-12 years) with ADHD who were treated in the Chinese PLA General Hospital in 2019, and 16 healthy children without ADHD (aged 6-12 years). Fecal samples were taken from the participants to compare the differences in abundance of bacteria between the two groups. There was no significant difference in diversity of bacteria between the children with and without ADHD. But the scientists noticed markedly lower populations of Faecalibacterium and Veillonellaceae, and higher abundances of Odoribacter and Enterococcus in the ADHD group compared with the control group. Moreover, there appeared to be dissimilarities in the metabolic pathways of neurotransmitters (including serotonin and dopamine) between the two groups. This study concluded that distinct compositions of the gut microbiota may influence the brain-gut axis and neurotransmitter levels, which can in turn affect ADHD symptoms. [NPID: attention deficit hyperactivity disorder, ADHD, children, China, Chinese, bacteria, microbiota, microbiome, neurotransmitters]

This 2020 article looks at the gut microbiota (community of microorganisms living in the gut) in relation to autism spectrum disorder (ASD). This topic is brought up due to the publication of studies that have demonstrated the gut microbiota’s potential association with social dysfunction and repetitive behaviors (two core symptoms of autism). The bidirectional communication pathway that exists between the gut bacteria and the central nervous system (known as the microbiota-gut-brain axis) plays a part in the modification of behaviors such as sociability and anxiety. There have been attempts to characterize the microbial composition specific to patients with ASD, but results have been inconsistent. Nevertheless, there is a difference in the composition of the gut microbiota between autistic and typically developed individuals. The results of several past animal studies have suggested that the gut microbiota plays an important role in ASD pathophysiology. Further evidential support comes from reports of abnormalities in metabolites produced by the gut microbiota in ASD patients. Moreover, the intestinal bacteria of autistic people have been associated with abnormal immune responses. While the microbiota has been used to develop treatments for ASD, supplementary studies are required to confirm the effectiveness of these microbiota-based treatments in ASD. [NPID: ASD, autism, autism spectrum disorder, autistic, children, microbiota, microbiome, bacteria, gut, GI, gastrointestinal, anxiety]

While many pediatric studies have investigated the relationship between autism spectrum disorder and the microbiome-gut-brain axis (the communication between the gut microbiome and the central nervous system), this 2021 paper focuses on the potential role of this microbiome-gut-brain axis (MGBA) in attention deficit/hyperactivity disorder (ADHD). Although ADHD is the most common neurodevelopmental disorder in children, the research on this association has been limited and variable. Thus, the purpose of this present review was to present the current evidence on the functioning of the MGBA in children with ADHD and explain how omega-3 polyunsaturated fatty acids (ω-3 PUFAs) play a particular role in this interaction. In addition, the authors explore the possibility of utilizing the gut microbiome as a therapeutic target for ADHD. This review covers the following topics: the diverse interplay between the gut microbiome and the central nervous system; the influence of the gut microbiota on the imbalance in omega-3 polyunsaturated fatty acids seen in ADHD; and the current literature on probiotic use in pediatric patients with ADHD. In addition, the paper addresses the altered composition of gut microbiota observed in children and adolescents with ADHD, and how this relates to irregular physiological processes linked with the disorder. Finally, the article examines the connection between the gut microbiome and the regulation of circadian rhythm since sleep disorders often accompany ADHD. [NPID: ADHD, attention deficit hyperactivity disorder, microbiome, microbiota, bacteria, probiotics, omega-3, fatty acids, PUFAs, children, adolescents]